What’s That Smell? Nevermind Tone

“I’ve got information, man. New s**t has come to light.” —Jeffrey Lebowski

It’s been a while since we last posted about this album, and while we’re always working on the next tone, we’ve got some new information to share. It’s timely because we now have a model of the classic DS-1 Distortion pedal too. All signs are pointing toward revisiting the recording of Nevermind.

New S**t Has Come to Light

Hyrkas, S. [@livenirvana]. (2025, May 2). May 2–28, 1991 – Van Nuys, CA, US Nirvana records a session with Butch Vig at Sound City Studios… [Photograph]. Instagram. https://www.instagram.com/p/DJKv3q6NVA0/?img_index=7

In a recent interview with Rick Beato, Butch Vig revealed that the recording of Smells Like Teen Spirit could have had a Fender Bassman mixed in at low volume, panned to the center, just to thicken things up a bit.1 That would have been accompanied by stereo-panned, double-tracked guitars through the Mesa/Boogie with clean tones coming from a Vox AC30. Recently, we came across the track sheet for Smells Like Teen Spirit on Instagram. Not only does this confirm Vig’s statement about a center panned Bassman, it also reveals that the original stereo tracks were recorded with the Bassman, not the Mesa/Boogie.

That M**********r Stole My Guitar Tone

In another interview with Beato, Billy Corgan described how he pioneered use of the Big Muff with Butch Vig during the recording of their first album, Gish.2 Corgan figured out that using the low input of the amplifier helped improve note clarity, providing headroom for a heavily distorted guitar at the input which Vig was able to get on tape. Really, Vig just had to hold back his reservations since no one at that time was willing to record such heavily distorted guitars. Butch’s experience, or lack thereof, was about to alter music history.

During that same interview, Corgan admitted that when he first heard a pre-release copy of Nevermind, it was immediately obvious that Butch had applied the same techniques they had pioneered on Gish to the sound of Nirvana’s major label debut.

The Fender Bassman

Could this be the defining sound of grunge? Vig was no stranger to promoting how important this amp would turn out to be. With Corgan, they ran the Big Muff into a Marshall amplifier, however for Cobain they would use the Fender Bassman. This was a favorite amp of Vig who had a modified version at his own Smart Studios. Since the Bassman and Tremolux share similarities in their circuit, we decided to start with the 204D Amplifier and 1×12” C 15W ‘63 Cabinet.

I have to admit that Smells Like Teen Spirit has always been a mystery. That tone. That riff. It’s a song that has definitely spent it’s time in the spotlight, maybe too much time. A magnet for fans that knew nothing about the previous record. Refined over hours of rehearsals and pre-production until every second felt right. It’s the only song on the record over five minutes in length. Regardless of what anyone in the band has said, this was intended to make a statement. And it did. It revolutionized the music industry almost overnight. You know the story well. But the guitar tone? We thought that was lost to time. Lost to forgotten facts about amps and effects. Lost to a mix engineer that crafted ear candy so sweet, we all fell prey to his whims.

In Bloom

We decided to tackle In Bloom first. The stereo mix sounds like two heavily panned guitars, enough to isolate each tone and compare what might have been used in the studio. And it seemed logical that one of those might be the Mesa/Boogie and the other could be the Bassman.

After firing up the 204D Amplifier, we could almost instantly hear that the right channel was the Bassman. There’s a certain rasp to this Fender amp that’s unmistakable. In this case, we’re just cranking the amp, no distortion pedal. That left us with the left channel for the Mesa/Boogie. We spent some time with the 802C Amplifier and 4×12” A 300W ‘87 Cabinet going back and forth between the DS-1, the Big Muff, and the preamp and found that the Big Muff had the closest tone.

Preset: Teen Spirit

Preset: Mesa Verde

Smells Like Teen Spirit

With In Bloom sounding pretty good, it was time to revisit Smells Like Teen Spirit. Based on the track sheet, we mixed two separate takes of the Bassman, panned hard left and hard right, but there was something missing. Just like Vig said, there’s a thickness present in the final mix that we couldn’t hear with just two tracks. However we knew adding a third take with the same Bassman would be overkill.

We happened to notice that the track sheet had the stereo guitars listed as DIST GTR, but the center track listed as GTR. Did DIST indicate that a pedal was used? We went back to the stereo Bassman tracks and added the Big Muff. That was too thick, so we tried the DS-1. It still wasn’t sounding right, but we pushed on with the third Bassman track. First with the Big Muff to provide some contrast to the stereo DS-1s, but it wasn’t working. Since there was no DIST in the center track’s label, we went back to just the cranked Bassman. That sounded really close. The rasp from the Bassman was sitting perfectly on top of the smoother distortion from the DS-1s, pulled back a little in volume, panned to the center just like Vig said. It was the closest to tonal Nirvana we’ve ever come, much closer than we had been before. If you want to try the mix yourself, follow this layout in your DAW:

  • [Left] Bassman + DS-1 (Take A)
  • [Center] Cranked Bassman, -3 to -6 dB
  • [Right] Bassman + DS-1 (Take B)

We also added a clean tone with chorus for good measure.

Preset: Cranked

Preset: Cleen Spirit

Lithium

One more thing. From interviews, we know that the Big Muff was a key element to the chorus in Lithium. Since we dialed in presets with the Bassman by itself, and with the DS-1, we thought it would be worthwhile to also dial in this classic preset with the Big Muff.

Preset: Immodium II

While there’s still more songs to cover, we felt these core tones needed to be heard, asap. We’re taking some additional time to think about studio effects like reverb, the elusive SPX-90 Symphonic preset, as well as Kurt’s live tone. Also that searing guitar, supposedly plugged directly into the mixing board on Territorial Pissings. But more on that later, for now our little tribe is going to take a rest, as a friend.

1 Beato, Rick. “Butch Vig: From Smashing Pumpkins to Nirvana – Alternative Rock’s OG.” YouTube, uploaded by RickBeato, 21 March 2023, https://www.youtube.com/watch?v=5U9XJdd4FlM.

2 Beato, Rick. “The Smashing Pumpkins: The Billy Corgan Interview” YouTube, uploaded by RickBeato, 13 December 2022, https://www.youtube.com/watch?v=nAfkxHcqWKI.

Fun House Tone: Garbage Bin Overdrive

Did you know that Rhino released all of the tapes from the Fun House sessions? Like everything? It captures a moment in time when bands wanted to stay true to their art and capture complete performances. They had to ask themselves questions like, did someone mess something up? Do we feel like we could do better? And always, let’s do one more as a safety. In this case, we’re given access to the complete process. For instance, all 28 takes of Loose. The mistakes, the banter, the brilliance. It’s a cool snapshot. Released in 1999 and spread across 7 compact discs, 1970: The Complete Fun House Sessions may have originally been positioned as a collectors item but it’s really a pillar of our rock n’ roll heritage and should be heard by everyone that picks up a guitar, microphone, or pair of sticks.1

Social Distortion

Iggy famously hated the sound of his voice. Starting with this recording, Iggy actually ran his vocal mic through Marshall amplifiers, acting as a P.A. for their live performance as well as adding some dirt, essentially creating his signature sound.2 Note that while Iggy did not sing through an amplifier on the first record, they did treat his vocal with one during remixing. This was likely the start of the idea, and why not capture it live?

Ron Asheton, the guitarist and brother of drummer Scott Asheton, has gone on record stating that he used Marhsall amplifiers for his sound as well. And while we do see live footage of Ron with a few Marshall stacks, our ears tell us something different. When we sat down to run some tone tests, we found that the amplifier used on this record sounds more like a Vox. Why? Our guess is that a small Vox combo that could only output 30W was much more acceptable in the studio. Remember, this was a time when engineers were unable to tame the extreme volume of a 100W Marshall, let alone more than one.

All the King’s Men

Don Galluci served as the producer on Fun House. In Ron’s words, “Galluci was Elektra’s choice,” but the band was ultimately happy.3 Don had a career in television which cemented his status as a famous icon with the group, and at the young age of fourteen played organ on “Louie Louie,” a song that certainly shares some D.N.A. with The Stooges. Galluci would be the one who influenced the group to record live, charging forward in an all-for-one onslaught of crazed-rock togetherness. The idea was to capture the power of the band live, a phrase that continues to echo through the music industry today with bands far and wide.

And capture the band live they did. With take after take, each song getting refined into the diamond we now know, you can hear the bleed from the instruments in the room. You can hear the room caving in on itself. Add a layer of plate reverb smearing the guitar like butter on bread and you’ll get a taste of this sonic toast in your ears.

The Presets

We ended up blending our ‘67 cabinet with 20W Celestion speakers. It’s possible that Ron used his Marshall cabinets as extensions, or maybe there was additional EQ from the console that we’re hearing. Either way, this trashy sound is yours to keep. Have fun! House!

Loose

The core sound, with more Vox than Marshall from the cabinets. This tone has a ringing, jangly quality, like something’s actually loose in the amplifer. Where this tone is more lacerating to the ears, turn to TV Eye for something more stabby.

TV Eye

The core sound, tuned to the song T.V. Eye. Some of the other tracks on this album were less bright and more washed out in reverb. For big chords pull back the Boost for more clarity. Like most records during this era, there really wasn’t a lot of distortion on the guitar signal. Single notes might sound thinner than you’d expect from today’s high gain amps. If you need it, the extra boost is at your fingertips.

TV Eye B

Similar to the core tone but with more bass if you’re still feeling like this tone is too thin with the boost up. This has a little more of that 4×12” meat on the bones.

TV Fuzz

Rolling back the gain and engaging the fuzz was Ron’s lead tone. It has a less brittle, smooth sustaining quality. There’s still a heap of garbage coming through the speakers, but it stands in contrast to the rhythm guitar sound. Used on tracks like Down On the Street, and Loose, pan right with the rhythm guitar on the left for a fun mix.

Fun House Wah

And of course the Wah. What’s left to say. Pair with a controller like the FCB1010 for hands free operation with the new device profile now available in the MIDI configuration selector.

1 https://www.rhino.com/product/complete-funhouse-sessions

2, 3 Edmonds, B. (1999). [Liner notes]. In 1970: The Complete Fun House Sessions [CD]. Rhino.

Void Your Warranty: Circuit Bending on an iPhone with SynthStamp

We’d like to take a moment to introduce you to the B500. A synth both internally and externally modeled after a popular sampler from the mid-80s. The reason for its popularity was primarily its cost. For $100 in 1985 ($300 in 2026), this sampling keyboard could be yours. That was a fraction of the cost of the nearest competitor, but it also came with a caveat—audio quality was low-fidelity. Over time this sampler was relegated to the toy bin in most stores and minds, eventually experiencing a resurgence, again due to its affordability. This time, hackers, creatives, and engineers ventured to open things up and started tweaking circuits to find new sounds. It wasn’t until Reed Ghazala coined the term Circuit-Bending in 1992 that a movement had been realized.1

Circuit Bending

Circuit bending is an exploratory art. The premise being that the deeper you go, the more interesting things get. For instance, you could audition every combination of patch capable between analog and digital sections, or try connecting them all in different configurations, or in different combinations of one, two, or three patches, or… you get the picture. And while certain patches will become familiar sounds that you can internalize and reach for with your new sonic vocabulary, there’s always one more sound to be discovered. Whether it’s a new combination of patches, a specific patch that you hadn’t yet tried, or a new sample that happens to sound more interesting when bent with a specific patch, or all of the above, the quest never ends.

Tapping on the orange Circuit Bending button in the B500 will open up the Circuit Bending view. There are three sections that can be patched, representing different features of the synthesizer circuit: analog, digital, and clock. Analog routes can be used to bypass filtering for more gain, connect outputs to inputs for feedback, and route to digital and clock sections to impact address, data, and/or timing functionality with control voltage like behavior. Note that analog-to-digital connections are represented with an orange wire. Digital-to-analog connections are represented with a blue wire. They are treated differently. Also note that bending does not have an effect on synthesized tones, and only the clock section impacts rhythm playback.

Experimental Musical Instruments

Figure 1: From “Circuit-Bending and Living Instruments,” by Q. R. Ghazala, 1992, Experimental Musical Instruments, Volume 8 (Number 1) p. 23.

For those just beginning their journey, there is a treasure trove of information available on the internet. Take a moment to flip through a few pages of Experimental Musical Instruments.2 This is the first page where the term Circuit-Bending is said to have originated. The magazine dates back to 1985, and Ghazala has stated that his interest in manipulating electronics for experimental purposes started as early as the late 60s. It’s important to distinguish the idea of non-standard instrument making for the purposes of sound exploration from bending instruments that already exist to create sounds that the original designer did not intend. While there is sonic overlap and sympathetic interests between the two fields, they are distinct.

And really, this is a new frontier for SynthStamp. The idea that we can model real instruments in a way that permits dynamic connections similar to those made when bending an instrument. Does this inspire you to want to bend other instruments? Are you content with the B500 as a unique one-of-a-kind tool in your plugin kit? Or do you want more?

1 Ghazala, Reed, Circuit Bending: Build Your Own Instruments, Wiley Publishing, Inc., 2005, p. 12.

2 https://archive.org/details/emi_archive/0-START-HERE/

Wheels of Fire Tone: Live, Loud, and Fully Blown

“…if I turn it down, the sound changes. And I can’t get the sustain I want.” 1 – Eric Clapton discussing the recording of Blues Breakers

Time seems to have a dulling effect on our collective memory. Stories that we thought would last forever don’t seem to be as relevant in today’s culture. Things that were shocking no longer seem to shock. Sounds that were too loud and aggressive no longer seem as loud or as aggressive as they once were. In 1968, Cream was at the height of it’s commercial success. Bringing intense, improvisational blues rock to audiences night after night. As Mickey Hart said in Beware of Mr. Baker, “They were like Vikings. It was like scorched earth. They were there to take heads.”2 But they were simultaneously falling apart at the seams due to internal friction, they would break up by the end of the year.

But not before releasing two albums and going on a farewell tour. At this point, there was no question audiences were going to be subjected to some very serious volume, specifically coming from cranked Marshall amplifiers. But just like a distant memory, that’s no longer what people hear when they listen to these performances. In stark contrast, modern sound systems put cranked Marshall amplifiers to shame. With advances in sound reinforcement and improvements in audio quality, audiences now experience a much higher fidelity concert, in some cases in stereo or multi-channel audio. And while there is still room to grow, to take live shows to new levels of creativity, the days of driving guitar amplifiers to their destructive brinks are faded memories of the past. It was with this in mind that we set out to revisit some of the sounds heard on Disraeli Gears when we realized Wheels of Fire and it’s groundbreaking live performances might be more interesting to analyze.

This Wheel’s on Fire

Figure 1: Live recording configuration from 1968 concerts used for Wheels of Fire. From “An In-Depth Interview with Engineer/Producer Tom Dowd,” by P. Laurence, 1975, Recording Engineer/Producer, Volume 6 (Number 3) p. 38.

Tom Dowd first worked with Cream on Disraeli Gears and would go on to work with Eric Clapton extensively during his solo career. He may have been the first, or at least one of the first engineers to figure out how to record a Marshall amplifier on full blast. While most would have asked the artist to turn it down for the purposes of making a proper record, Tom let it rip and got it all on tape. And for this we are forever grateful. Despite his involvement with Cream in the studio, Tom had a busy career working for Atlantic Records and for the live recordings on Wheels of Fire he was only present early on to check sound quality before turning the engineering reigns over to Bill Halverson, a relatively new engineer from Wally Heider Studios in San Francisco, then on his second remote assignment.

Bill opened up to an interviewer in a mid-70s publication regarding the recording setup he used for these live performances. Two mics, one on each amp, selecting one of eight speakers across two cabinets per amplifier, blended, and that’s it. And it really is. Clapton had a wah pedal in between his guitar and amp, and nothing else. He relied on volume, tone controls, and the pickup selector to emphasize different passages. More bass for his famed Woman Tone, more volume for blistering solos, rolling back during verses, and changing pick attacks to signal delicate melodies or phrase notes more aggressively, all tied together with an amazing vibrato technique. It would be his voice in the days when he didn’t like to sing.

Cascading Distortion

But then how does the guitar end up sounding like that? It’s certainly distorted, sometimes violin-like, sometimes thick and muddy, sometimes harsh. It’s really combination of things. The humbucking pickups in The Fool pushing the front end, the amp turned up loud driving the power-amp into saturation, and the speakers also getting pushed to the edge of their operable state. It’s interesting, because on playback, far removed from the physicality of the loudness, to a young listener it probably sounds just like a muddy guitar. A recognizable and primitive sound that would get refined by boosting treble, cutting bass, and scooping mids through subsequent hard rock and heavy metal bands. Ultimately ending up in a buzz-saw onslaught until we just couldn’t take any more.

However, if you take a moment to let your ears adjust and unlearn the modern sound of guitar, you might find that this sound is richer, more nuanced, and more dynamic. It’s not squashed and brittle, it breathes with each note. Especially for younger guitarists who can’t yet play with speed, slowing down and learning to articulate phrasing might not be such a bad thing. We’ve read that the Marshall amplifiers Clapton was using were transitional, meaning old stock with new head boxes and logos. While these amps may look like the new models with split cathodes, they’re likely not. Since we’re using the Normal channel, the differences are actually minor, it was the Treble channel (Channel I) that changed drastically between these two revisions, nonetheless we’ve employed the VG402B Amplifier.

More Lore

“I had a little Shure microphone which no matter where I’d put it, it just distorted! …I ended up in the center of [the] speakers, not in front of any of them.”3 – Bill Halverson discussing how he recorded Cream live

That’s revealing and something we focused on when dialing in the VG 4×12 ’67 Cabinet. Using a combination of Offset and Cabinet Drive we were able to replicate the sound of an off-center mic picking up a speaker playing well above it’s operating range. The sound in unmistakable, start with a medium output humbucker in the bridge position and you’ll be right there next to the band in hallowed halls. You can roll off the highs with your tone control or engage the Dark Boost for convenience, simulating tone control effects while also providing a boost for solos via the EQ100 Treble Boost (or in this case, treble cut via the Invert toggle). Lastly, things wouldn’t be complete without the WH100 Wah. Control via MIDI for hands free operation or just let the default setting wrap around your notes, it’s a classic.

The Presets

It was also important to dial in some echo to create sense of space, sounds bouncing off the walls as listeners ears are getting melted. In this case we went with the AMB200 Spring Reverb set to a short decay with a decent amount of pre-delay to get a slapback repeat that was pleasing to our ears. That’s another cool thing about our Ambience modules, they can be configured with shorter decays to get a variety of room sounds as well as the traditional echoes that they’re known for. The spring reverb is in Mono, a nod to the times, but check out the Echo Chamber or Plate Reverb for stereo options.

Loudness II: starts off with the basics: cranked amp, offset mic, and cabinet drive. Instant bliss.

Loudness IIb: engages Dark Boost for violin-like leads, switch to the neck pickup for even more cream.

Bolero: engages both Dark Boost and Wah in fixed position which helps to accentuate lead passages.

Cleanish: dials it back just a little for a change in mood.

1 Port, Ian S. The Birth of Loud: Leo Fender, Les Paul and the Guitar Pioneering Rivalry that shaped Rock n’ Roll. Scribner, 2019, p. 227.

2 Beware of Mr. Baker. Directed by Jay Bulger, Insurgent Media, Pugilist at Rest Productions, 2012.

3 Genzolini, E. Cream: Claption, Bruce & Baker Sitting on Top of the World. Schiffer, 2023, p. 49.

Celebrating 10 Years of AmpStamp

A look back at the first 10 years of AmpStamp, and a technical decision that we’ve never talked about.

It’s hard to believe that AmpStamp turned 10 this January. 10 years of coding, 10 years of listening tests and A/B comparisons, 10 years of chasing classic recordings down endless rabbit holes. We wanted to take a moment to mark the occasion and share something we’ve never really talked about publicly. It’s a technical decision that shaped the sound of AmpStamp from day one, and looking back, we probably should have been talking about it from day one.

Convolution, on a Phone, in 2016

When we shipped the first version of AmpStamp (then called Vintage Guitar) on January 19th, 2016. At the time, the standard approach for cabinet emulation on mobile was algorithmic. A chain of filters, some carefully tuned EQ curves, and a hope that it sounded close enough. It’s a reasonable approach—it’s lightweight, it doesn’t tax the CPU, and on headphones most people couldn’t tell the difference anyway. The major iOS amp sims of the day were all going this route. But there was another approach, well-established on desktop by then, used in plugins like Two Notes Torpedo and various IR loaders that pro studios were already running: convolution. Instead of approximating what a speaker cabinet sounded like with filters, you could take a recorded snapshot of an actual cabinet—an impulse response—and mathematically apply that snapshot to a guitar signal in real time. It’s not an approximation. It’s the actual sound, re-applied.

We went with convolution. With Support for iPhone 5s. In 2016.

This was, to put it mildly, not the obvious choice. Real-time convolution at audio rates was expensive on mobile hardware of the day, and getting it to run cleanly while also handling the rest of the signal chain—amp model, effects, all of it—took some work. But the difference in sound was undeniable. A real cabinet has resonances and complex behavior that algorithmic models, no matter how carefully tuned, just don’t fully capture. Once you’ve heard your guitar through a convolution-based cab, going back is hard.

To be clear about what we did: we captured real cabinets ourselves and built a custom convolution engine. We weren’t shipping an IR loader for users to drop in their own files—we were using IRs as the foundation of how every cabinet in AmpStamp sounds, baked in so that guitarists could just pick a cabinet and play. Convolution was the engine, not a feature.

The Part We Kept Quiet About

Here’s the thing—we didn’t talk about it. The technique itself wasn’t patentable, convolution and impulse responses had been around for ages, and the concept of using IRs for guitar cabinets was already old news in high-end studios. What we had was an early, performant implementation on mobile, which is a craft advantage, not a legal one.

The thinking at the time was, if we publicly say AmpStamp uses convolution, we’re basically pointing competitors in the right direction. The work to get there on mobile was nontrivial, but once someone knew where to look, the path got a lot shorter. So we let the app speak for itself and figured guitarists with good ears would notice the difference.

That was a mistake. Not the technical decision—the marketing one.

The Lesson

On the App Store, no one hears the difference unless you tell them what to listen for. Guitarists scrolling through amp sim apps aren’t doing blind A/B tests. They’re reading screenshots and bullet points, often listening through phone speakers, making decisions in seconds. The technical decision that made AmpStamp sound more authentic was completely invisible at the point of purchase.

Meanwhile, “convolution-based cabinet modeling using real impulse responses” is exactly the kind of bullet point that gear nerds among us actually read carefully. We had the substance. We just didn’t put it on the label. It would be years before convolution-based cabinet tech became the standard on iOS. The major mobile amp sims didn’t move in that direction until somewhere between four and seven years after we shipped. By the time the field caught up, the differentiation was gone—and we’d never even claimed the ground when it was ours to claim. It’s a lesson we’re carrying forward.

Hear It For Yourself

Which brings us to Free Previews, our newest feature. The idea is simple—we want everyone to be able to hear these tones, regardless of whether they’ve paid for the gear yet. Pull up a preset, hit play, and hear what AmpStamp actually sounds like. The amp, the cabinet, the convolution under the hood, all of it. No subscription, no purchase, just the tone in your ears.

It’s the answer to a question we should have been asking 10 years ago: how do we let people hear what we’ve built? It turns out the best way is to just let them play it.

Looking Forward

AmpStamp is still going strong. The convolution engine we shipped in 2016 is still doing its thing, still helping guitarists land on tones that sound like the records they love. We’ve added a lot since then—new amps, new cabinets, new effects, the recent Cabinet Drive feature, and most recently the EQ200 Dual Parametric Equalizer which has unlocked a whole new realm of heavy metal tone exploration.

And we’re bringing what we learned to SynthStamp, our new app that launched on April 3rd of this year. SynthStamp is built on the same philosophy—technical decisions that most users won’t see at first, but that you’ll hear immediately. Model 5001 is the first ARP 2600 emulation on mobile, with full patch cabling, and Model B500 is, as far as we can tell, a first-ever circuit-bendable take on the Casio SK-1. All models also accept stereo audio input for real-time effects processing, which almost no other synth app does.

This time, we’re telling you up front. We learned that one the hard way.

Thanks for 10 years of AmpStamp. Here’s to the next 10.

System Presets: B500

Sampled Tones

Synthesized Tones

Circuit Bending

External Sources

System Presets: 5001

Basic Instruments

Advanced Instruments

Rhythms

Natural Sounds

Arpeggios, Chords & Sequences

Sound Effects

Advanced Applications

External Sources

B500 Sampling Keyboard

The B500 Sampling Keyboard models a sampler from the mid ’80s, with 4-voice polyphony and multi-channel note memory. The audio engine and user interface are based on the Casio SK-1. Many DIY enthusiasts have taken advantage of the affordability of this synth and pioneered circuit modifications to manipulate ROM address and data outputs for a variety of otherworldly sounds; a practice that has since been coined circuit bending.


Section Details

1 Volume

Increasing volume above 50% engages speaker distortion with Internal Speaker blend greater than zero.

2 Internal Speaker

Sets blend between Direct output and Internal Speaker emulation.

3 Operation Modes

  • Normal mode is the default mode of operation, supporting 4-voice polyphony.
  • Solo modes 1 and 2 each provide separate monophonic voices, supporting different tone selection.
  • Chord mode splits the keyboard and engages 3 or 4 note diatonic chords from F3 to C5, with chord type specification from C#5 to C6. Refer to synth labeling for chord type per note which includes: major, minor, 7th, minor 7th, minor-major 7th, augmented, diminished, suspended 4th, augmented, 6th, minor 6th, and half-diminished chords. If no type is supplied, chords default to major.

All modes can be sequenced via note Memory, refer to Section 10 below for details.

4 Effects

  • Vibrato engages subtle pitch bending after an initial delay.
  • Portamento bends each note up or down to pitch depending on if an existing note is being held below or above the played note.

5 Circuit Bending

Tapping the Circuit Bending button opens a new window containing three sections corresponding to Analog, Digital, and Clock sections of the internally modeled circuit. A fixed set of bend points have been provided that can be dynamically connected or configured with a wide variety of results mimicking actual bends on a ROM-based synthesizer.

Note that inter-section connections are unidirectional with respect to the point of origin. If a bend connection is modified, wire color will change to reflect routing from the source to a new destination. This allows for independent control of analog-to-digital or digital-to-analog bends, with each direction providing a unique effect.

6 Envelope Select

Tapping the Envelope Select button highlights the currently selected volume envelope. Each accidental key on the main keyboard represents a different envelope. Envelopes are pre-programmed with each tone and can be modified and saved in a preset. The display bar above the keyboard contains visual representations of each envelope type.

7 Synthesized Tone

Tapping the Synthesized button selects the synthesized tone, which defaults to reference pitch.

Tapping the Synthesizing button opens the drawbar which overlays partial values above the specific subset of natural keys that control each partial. These keys can be tapped or dragged to change the level of each partial from values 0 to 15. Each partial is labeled based on traditional organ pipe lengths from 16′ to 1′.

Note that synthesized tones are internally generated and are not impacted by Circuit Bending.

8 Sampled Tones

What else is there to say? These sampled tones are classics, we hope you enjoy them!

Note that selecting a sampled tone loads a pre-programmed envelope, and re-selecting the same sampled tone will re-apply this envelope. Envelopes with sustain or longer decays than selected sample length will loop automatically.

9 Rhythm

Tapping the Rhythm button highlights the currently selected beat. The lower section of the drawbar shows each available beat for the specific subset of natural keys that apply. Changing the beat is instantaneous and can transition mid-measure during playback. Tapping Tempo buttons changes BPM by +/-10.

Tapping the Fill-In button plays a preset fill with custom duration based on the selected beat. Fills transition mid-measure and will play to the end of the current measure, or the next full measure when tapped within a 1-2 beat grace period at the end of the current measure.

10 Memory Sequencing

Tapping the Memory button opens a new window containing a score-based view for recording simple melodies. In Normal mode, melodies can contain four note harmony, in Multi-Channel mode (Solo 1/2, Chord), melodies are monophonic or fixed diatonic chords.

Melodies can be manually entered using Note Length and Insert Rest for composition. Melodies can also be recorded live which may provide a less accurate notation for the performance but will play back exactly. Delete removes the current or previous note based on cursor position. Clear erases the entire sequence on the selected staff.

When recording live, rhythm always plays back to provide a reference for the beat. During manual playback, Sync Rhythm can be enabled so that the beat starts during playback. Enabling Repeat sets a loop point at the end of the last measure with playable notes.

Note that after programming and/or recording a melody, the Lock icon above the title bar can be enabled to ensure further edits are disabled.


Continuous Sampling

  • Continuous sampling for realtime glitch effects
  • Sample loop editing for time and pitch manipulation
  • Single or multi-part sequencing for sample playback—combine with continuous sampling for additional chaos

Tapping the Continuous Sampling button engages a live sampling mode where the buffer used for playback is taken directly from stereo audio input. By default the buffer plays back at a normal rate, reproducing the original signal, slightly degraded by the limitations of the internal sampler. In addition to this, the keyboard or Memory sequencer can be used to trigger buffer playback at different sample rates. And in addition to that, Circuit Bending can be employed on sample buffer playback. With full stereo support.

Note that this mode is independent of the traditional internal mono sample buffer that can be used to capture and store samples for playback and manipulation.

11 Sampling

Tapping the Sampling button opens a new window containing an oscilloscope-style view for capturing samples and setting the loop point. Instructions to operate are as follows:

  1. Drag the Threshold (horizontal line) up or down to establish a reasonable threshold slightly above the noise floor
  2. If needed, adjust Gain and/or Range to set input level
  3. Engage by tapping Record which transitions to an Armed state
  4. Once the input signal exceeds the threshold an internal 1.4s buffer will fill with audio data
  5. Drag the Loop Point (vertical line) left or right to establish where sample playback will stop and/or loop

By default, Left and Right inputs are summed to a mono, however Left or Right can be selected independently. Use Monitor to listen to sounds before and/or during recording. Dir/Mic sets blend between Direct input and Internal Microphone emulation.

By default, playback is normalized to A4, however Tune can be adjusted +/- 12 semitones to extend range or assist with tuning.


Audio Unit Operation

  • Section 9: Sync DAW Tempo

In addition to the specified controls above, a new button is made available when running SynthStamp as an audio unit. The Sync DAW Tempo button is provided which enables continuously tracking DAW BPM rates so that rhythms can be synchronized with DAW recording and playback.

5001 Analog Synthesizer

The 5001 Analog Synthesizer models a dynamically patchable, semi-modular, monophonic analog synthesizer from the late ’70s. The audio engine and user interface are based on the ARP 2600. The front panel and extension panel on the keyboard present a majority of the controls and I/O from the original synth. The layout has been slightly modified for conciseness and to support stereo audio input. The drawbar in between the keyboard and the front panel can be dragged up or down to maximize either view for ease of use.


Getting Started with Normalled Connections

If you’ve never worked with a synth like this before, or if you need a refresher, each control input is internally connected to an output as labeled on the synth without having to make any additional patches. Historically, this conserved patch cables for relatively frequent connections, allowing for more experimentation if cables were limited as well as kept the visual layout of a patch much simpler by avoiding unnecessary clutter. In a software incarnation with virtually unlimited patching normalling also serves as an effective starting point for learning the instrument. If you’re not sure how to begin or if you want to get to a usable sound fairly quickly, start by creating a new preset with no default patches, turn up some sliders, and start playing. Note that we’re using the term patch to refer to an individual connection between inputs and outputs as well as a generic term for the whole preset once all patches have been made, e.g. a patch can refer to either a single connection or the preset itself made up of multiple connections.

Key sliders to getting initial sounds include:

  1. Section 8: Mixer Slider No. 2 (VCA)
    • Start here, enable output to speakers
  2. Section 7: VCA Sliders No. 1 (VCF), and No. 3 (AR)
    • Next, enable output from VCF
    • Control volume with AR triggered by keyboard input
  3. Section 6: VCF Sliders Nos. 1-3 (VCOs)
    • Route VCO square/saw outputs through VCF
    • Increase Initial Filter Freq. for brighter sounds

During step #3 you should begin to hear sound when playing the keyboard as you increase the VCO input levels to the VCF. Note that the keyboard input alters oscillator pitch, adjusts filter frequency, and triggers the volume envelope all at the same time! This simple patch produces a filtered combination of the three VCOs, tuned to the same pitch by default, without involving any patching. The sound is gated by playing the keyboard via the VCA and AR envelope generator. From here you can begin to alter tuning, modify filter cutoff for different timbres, and adjust envelope attack and decay for dynamics.


Section Details

1 Stereo Preamplifier

Use the audio input selector in the app toolbar to choose Left and Right input channels: tap to assign L, double tap to assign R. Left and Right assignments can be the same channel for mono routing flexibility. With mono input buses, L/R automatically share the same channel.

2 Envelope Follower/Ring Modulator

The envelope follower generates a control voltage based on the amplitude of the supplied input signal. Note that the input is normalled to the sum of the Left and Right input channels (which is the same channel for mono input buses).

The ring modulator is a four quadrant multiplier producing the multiplication of two supplied inputs. Note that polarity is preserved such that phase can be inverted when supplying a negative input signal. The DC/AC switch inserts or removes DC blocking capacitors at each of the inputs. Select DC when multiplying control voltages, AC for strictly audio inputs.

3 Keyboard CV/Multiples

The keyboard control voltage (CV) is normalled to the VCOs and VCF, and is provided as an output here for additional routing.

The four multiples dynamically reconfigure based on their connections and can provide 1 input to 3 outputs, 2 summed inputs to 2 outputs, or 3 summed inputs to 1 output. Both voltage control and audio inputs are supported.

4 VCOs

The voltage-controlled oscillators (VCOs) have a range of 0.1 Hz – ~20 kHz, and 0.01 Hz – 30 Hz in low frequency (LF) mode. Frequency control has a range of +/- 2 octaves, fine tuning control has a range of +/- 1 semitone.

5 VCF

The voltage-controlled filter (VCF) has a range of 20 Hz – 20 kHz. Fine tuning control has a range of +/- 1 octave. Increasing resonance can cause self-oscillation near maximum.

6 Envelope Generators

There are two envelope generators producing either attack, decay, sustain, and release (ADSR) or attack, decay (AR) envelopes. They are normalled to the keyboard gate/trigger and have a manual control that can be tapped to trigger the envelope cycle. Additionally, an external source can be selected for gate/trigger which disables keyboard input. The keyboard gate/trigger are also made available here for external routing.

7 VCA

The voltage-controlled amplifier (VCA) supports two audio inputs and two control inputs. The initial gain can be used to “open” the VCA and set a default volume, applying additional control signals is additive.

8 Mixer/Reverb

The mixer section has several components related to system output. The Mixer sums two inputs to mono and provides a Mixer Pan control for the mono output. In addition to the mono output, the summed signal is routed to an internal Spring Reverb with separate Left and Right volume controls. Both the Mixer and Reverb outputs are made available for additional routing purposes.

In addition to the Mixer and Reverb outputs, a stereo Aux Input is provided as well as the full stereo System Output.

9 Internal Speakers

The Left and Right channels are routed through internal speaker emulations. Each channel can be separately blended between Direct and Speaker emulation outputs.

10 Noise Generator

The noise generator has two controls for spectrum (white, pink, etc.) and level, with one output. Increasing the spectrum control produces more high frequency energy by increasing the cutoff of the internal low pass filter.

11 Voltage Processors

There are four voltage processors. From the top, 1 and 2 are summed. The summed output and 3 have additional inverted outputs. And 4 is a lag processor, adding ramp and decay time to supplied control signal inputs. 1 and 3 are normalled to +10V which equates to the highest possible control voltage. 2 is normalled to Keyboard CV. And 4 is normalled to the Envelope Follower output.

Note that this section can be used to provide extra multiples if needed, as well as Keyboard CV inversion for interesting effects.

12 Sample & Hold/Switch

The Sample & Hold is driven by a clock signal provided internally or overridden by the External Clock input. The input, which is normalled to the Noise Generator output, is sampled based on the frequency of the clock signal and the sampled voltage is produced at the output. If supplied internally, clock speed is controlled by the second slider. Output level is controlled by the first slider.

The Switch is a bidirectional switch that reconfigures based on applied connections. The configuration can be either switching between A/B inputs to C [A | B >> C], or switching between A/B outputs from C [C >> A | B]. Switching is based on the same clock signal supplied to the Sample & Hold which can be overridden by the External Clock input.

13 Drawbar

The drawbar is provided for additional flexibility and can be used to resize the ratio between the front panel and the keyboard. This allows for more focus on patching or playing with smaller screen sizes.


The Keyboard

  • Highest-note priority
  • Note memory
  • Tuning options

The keyboard is automatically routed to the VCOs and VCF via KBD ON switches, as well as provided in Section 3 with KBD CV output, with the Gate and Trigger provided in Section 6. The keyboard produces a monophonic output with high note priority and note memory, i.e. highest note wins, after releasing the highest note, control voltage remains present at the output.

14 Keyboard Controls

Keyboard controls include toggling between Variable (0.5x-2.0x) and Fixed (~0.8x-~1.2x) interval tuning, as well as selectable Tuning (+/-12 semitones) and Portamento (0s-0.5s) controls.

Note that the Tone Interval controls (Variable, Fixed) adjust pitch spacing relative to Middle C (C4). Increasing these values spreads notes further apart, decreasing brings notes closer together, enabling crude microtonal tunings.


Audio Unit Operation

  • Section 3: DAW Clock Out

In addition to the specified controls above, a new output is made available when running SynthStamp as an audio unit. The DAW Clock output is provided in Section 3 which continuously tracks DAW BPM rates and re-syncs with measure playback so that rhythmic effects can be achieved in synchronization with DAW recording and playback.

Welcome to SynthStamp!

We hope you enjoy this app as much as we do.

Mac, iPad, and iPhone

SynthStamp can be used across all of your devices including Mac, iPad, and iPhone. You can launch SynthStamp as a standalone app for dedicated playing, or as a plugin inside of any DAW that supports Audio Units. SynthStamp is made available as both an Instrument and Music Effect audio unit.

Audio Unit

Loading as an Instrument (“SynthStamp”) provides dedicated sound generation with MIDI support. Note that as an Instrument, audio processing is limited to mono sidechain input. The sidechain input channel can be selected inside of DAW settings.

Loading as a Music Effect (“SynthStamp FX”) provides stereo audio input processing with MIDI support. Note that as a Music Effect, MIDI input is not typically recorded inside of DAWs like GarageBand or Logic Pro.

Stay Tuned!

It bears repeating that we’ve launched release 0.9 to get these synths out there and in your ears. We’re seeking some early feedback and will be rolling out an official 1.0 release shortly. This will include additional features like sequencing and, of course, more synths. Let us know what you think and what you want to see next!