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Dream Amplifier Design Dynamic Microphones
Old 4 weeks ago
  #1
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Dream Amplifier Design

Hello all,

I am a final year Applied Sound Engineering student studying at The University of West London.

For my final year project I am designing an 'amp-in-the-box' style guitar amplifier which will recreate valve tone with solid state components and also implement cabinet smulation technology.

For the benefit of research and development, I would like to know from the community each of your favourite ampifier stacks/combos and their specific components and features that make them so desirable to you. Also, what genre of music would you use them for.

I would like to know in this thread your preferred:


Pre-amp: Tube/Valve or Transistor make and model

Power Amp: Tube/ Valve or Transistor make and model, Amplifier Classification (A, A/B, C etc.)

EQ: 3 Band or Graphic

Gain Staging and Channel Numbers: 1 Channel, 2 Channel, DSP Modelling etc

Cabinet: Speaker Cone Size, Number of Speakers, Speaker Cone make/model.

Microphone: Make and Model, On/Off Axis

Genre/Style of Play: Blues, Djent, Finger-Pick etc

Thank you,
Jacob D
Old 4 weeks ago
  #2
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[MENTION=11648]@Jacob_Dworkin, all the best in your studies and successful design.

Pre-amp: Tube

Power Amp: Tube

EQ: 3 Band all the way

Gain Staging and Channel Numbers: 1 Channel if amp has a gain control, 2 channel if channel 2 is a gain channel.

Cabinet: 1 x 12

Microphone: SM57 slightly off center

Genre/Style of Play: Rock, Pop
Old 4 weeks ago
  #3
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Mikhael's Avatar
 

Pre-amp: Transistor: Pearce G2r

Power Amp: Transistor: Pearce G2r, stereo 100W/ch

EQ: 3 Band w/ semi-parametric mid on BOTH channels

Gain Staging and Channel Numbers: 2 channels, one voiced Fenderish, the other more like a Marshall, both with pre/post volumes and a master volume. Would like a good limiter available for Fenderish clean channel.

Cabinet: 4x12" Marshall, split stereo, w/Celestion G12-75

Microphone: Old EV dynamic, 627. I found the model number...

Genre/Style of Play: Prog and Fusion

I have the feeling I'll be alone on this one...

Last edited by Mikhael; 4 weeks ago at 09:30 PM..
Old 4 weeks ago
  #4
Is this an historical re-creation? Pods and Kemper have done the leg work for you already.
Old 3 weeks ago
  #5
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Quote:
Originally Posted by Mikhael View Post
Pre-amp: Transistor: Pearce G2r

Power Amp: Transistor: Pearce G2r, stereo 100W/ch

EQ: 3 Band w/ semi-parametric mid on BOTH channels

Gain Staging and Channel Numbers: 2 channels, one voiced Fenderish, the other more like a Marshall, both with pre/post volumes and a master volume. Would like a good limiter available for Fenderish clean channel.

Cabinet: 4x12" Marshall, split stereo, w/Celestion G12-75

Microphone: Old EV dynamic, 627. I found the model number...

Genre/Style of Play: Prog and Fusion

I have the feeling I'll be alone on this one...
This

I'd like to add

- FX Loop
- Footswitch
- Direct and record out
- Worldwide voltage selector (120/240V)
- Also 1 x 12" cabinet option available
Old 3 weeks ago
  #6
Quote:
Originally Posted by Jacob_Dworkin View Post
Hello all,

I am a final year Applied Sound Engineering student studying at The University of West London.

For my final year project I am designing an 'amp-in-the-box' style guitar amplifier which will recreate valve tone with solid state components and also implement cabinet smulation technology.

For the benefit of research and development, I would like to know from the community each of your favourite ampifier stacks/combos and their specific components and features that make them so desirable to you. Also, what genre of music would you use them for.
Hi Jacob,

Good luck with your project. You will fail, what you're attempting is impossible because transistors simply don't behave like tubes, especially when operated outside the conventional design parameters as often happens with guitar amps (I could elaborate, but the post would be very long. We can discuss it elsewhere if you like), but hopefully you'll come up with a good SS design. They do exist, they just don't behave or sound like tube amps.

As it is my answer will not be as concise or simple as your question format would indicate, as I own over 10 various guitar and bass amps, my music partner who shares my house has about the same number, and we share gear, each using what's appropriate depending on the project.


Quote:
I would like to know in this thread your preferred:


Pre-amp: Tube/Valve or Transistor make and model
Tube. Fender, Marshall, Vox, Ampeg, and (vintage) Supro. Various models.

Quote:
Power Amp: Tube/ Valve or Transistor make and model, Amplifier Classification (A, A/B, C etc.)
Tube. Fender, Marshall, Ampeg, Vox. Mostly Class AB, have some small single ended Class A. Nobody uses Class B or C for audio amplifiers.

Quote:
EQ: 3 Band or Graphic
No guitar amps that I know of use a graphic for main tone control. Some amps like (some) Boogies, the Fender Super Twin, and a couple others have an auxilliary graphic in addition to the main tone controls.

There are several types of "three band" (or two band) tone circuits. None of them (except possibly the Baxandall) should properly be termed "EQ". There are even several different types of one knob tone controls, some surprisingly sophisticated, such as the "slant" control which boosts bass and cuts treble at one extreme, boots treble and cuts bass at the other, and is more or less flat(ish) in the middle.

Most of our amps use some form of the Fender/Marshall "tone stack", which is an odd passive design with make-up gain that has interaction between the various controls so that moving one varies the action of the other(s). This common "tone stack" has no real "flat" setting. These are nothing like a conventional EQ found in a hi-fi system A discussion of this circuit can be found HERE, which contains, among other stuff (some erroneous) my explanation of the operation of the Fender circuit, which I don't feel like retyping here. A few amps, notably Ampegs, use a Baxandall EQ circuit, often modified with an added midrange bandpass/cut.

You're also ignoring the classic Presence control circuit as found in tweed and brownface Fenders and vintage Marshalls. This is not an EQ or conventional tone control at all, its a control that varies th frequency spectrum of the negative feedback loop in the power amp stage and as such affects not only frequency response but also the spectrum and amount of harmonic distortion, gain of the power stage, damping factor, saturation of the output transformer, etc.

Quote:
Gain Staging and Channel Numbers: 1 Channel, 2 Channel, DSP Modelling etc
None of our amps use "modern" overdriven gain staging. We have pedals for that. We have both 1 and 2 channel amps, no switching. Actually, that's not quite right - Bob has a Fender Princeton II, which is a Rivera design with channel switching but I don't think we've ever used the overdrive for anything, and I have a little Fender Frontman SS practice amp that gets recorded occasionally that has an "overdrive channel" function but we don't use that 'cause it's pretty awful.

DSP modeling, never.

Quote:
Cabinet: Speaker Cone Size, Number of Speakers, Speaker Cone make/model.
We have both separate cabs and combo amps.
Mostly 12", JBL, Celestion, Jensen. My Marshall Class 5 has a 10 but sounds better with a 12. I also like 15s but don't have any at present. Bob does have one in his vintage Supro.

Quote:
Microphone: Make and Model, On/Off Axis
I have over 80 microphones of which at least a dozen get used for electric guitar. Favorites include Beyer M201, EV RE10/11/15/16, Beyer M88, EV 635A, Earthworks M30, AKG C12A, AKG C414EB, Sennheiser MD409, AKG D12. Very rarely Shure SM 56/57 and Sennheiser MD421 but usually not. SM 57s and Sennheiser e609s get used for live punk and metal gigs where I don't want to risk better mics, that I use for recording.

I'm probably forgetting something.

Mic is NEVER on axis of the dome, often is toward the edge pointing in if close. Mic is frequently pulled back 1 or 2 feet, depending on the music.

Genre/Style of Play: Blues, Djent, Finger-Pick etc

Many different styles. Country, blues, rock, and punk more than others.

Finger picking, flat picking, combination picking, whatever it takes.


Quote:
Thank you,
Jacob D
You're welcome!

Last edited by John Eppstein; 3 weeks ago at 11:55 PM..
Old 3 weeks ago
  #7
RiF
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RiF's Avatar
Why not simply use as your reference what you can easily be seen as the seemingly most used guitar / cab combos out there? Or just take all the lists of the modelled amps / cabs from the top digital modellers and use those that everybody seems to have on their list. They did the market research work for you already.

You'll end up with a list of amps that will probably contain the following from Fender Twin / Deluxe / Bassman, Vox AC30, Marshall Super Lead / JCM 800 / Mesa MkII-V / Rectifier, Soldano SLO, Peavey 5150. Add some Marshall 1960 cabs with G12-T75 or Vintage 30 speakers and a Mesa Rectifier 4x12 with V30's to the built-in speakers of the combo amps and you're covered a lot of common ground.
Same with the mics. Although John uses/likes different mics, I think you'll find the Shure SM57, Sennheiser MD421 and Royer R121 (plus a combination of those) on top of that list. At least for studio work. For live, I am with John where you can see 57's and e906/e609's everywhere.
Old 3 weeks ago
  #8
Here for the gear
 

Thank you, @John Eppstein , for your detailed reply.

The overall aim of the project isn't to necessarily have full SS recreation of a valve amplifier system but to increase the efficiency of guitar amplification in general (lower power consumption, smaller size, lower cost components etc.) One aim of the project is to measure the ratio of second harmonic to third harmonic distortion introduced by overdriving valve amplifier systems and recreate that with a transistor pre-amp. With careful consideration to input biasing and transistor choice all research shows that this can be possible.

Most of the sonic characteristics (sag, voicing etc) of a valve amplifier comes from the power amplifier section as apposed to the pre-amplifier section so all research and data collection shows that valve pre-amp tone can be recreated succesfully in with a SS pre-amp, however the SS amp will never behave fully like a valve amplifier if the power amplifier is transistor based, that much is certain.

The Fender tone stack approach to equalisation is a new concept to me so thanks for flagging that up, the thread you have hyperlinked shows scientific consideration to its design and it is greatly appreciated.

As a guitarist myself, placing microphones off-axis is always the best way to go, in no situation (live/ studio) have I ever preferred the response of on-axis, hyper/ regular cardioid microphhones. The microphone and cabinet pairing will determine the frequency response of the cabinet simulation technology implemented, measured with an IR in a DSP environment and recreated with an analogue filter network.

You also raise a good point in which modern overdrive settings are not required much from an amplifier as boost/ drive pedals are common place even in more extreme genres.

All of these points have been take in to account for the initial design stage.

Thanks again,
Jacob D.
Old 3 weeks ago
  #9
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@RiF

You are correct there has been market research into this area already but as I am an academic I must prove I have done my own research into this field.

The most common combinations I have heard of during this research stage is a Peavey 5150 head with Celestion 12" speakers (usually 4 in a cabinet) and an SM57 off-axis, however most guitarists I have been able to speak to are in the metal sub-genres of music.

Choosing between a Marshall, Fender or Peavey sounding amplifier will be the creative choice I take in the design process.
Old 3 weeks ago
  #10
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Mikhael's Avatar
 

Quote:
Originally Posted by Jacob_Dworkin View Post
Thank you, John, for your detailed reply.

The overall aim of the project isn't to necessarily have full SS recreation of a valve amplifier system but to increase the efficiency of guitar amplification in general (lower power consumption, smaller size, lower cost components etc.) One aim of the project is to measure the ratio of second harmonic to third harmonic distortion introduced by overdriving valve amplifier systems and recreate that with a transistor pre-amp. With careful consideration to input biasing and transistor choice all research shows that this can be possible.
Some companies have already made great strides in that. Check out the circuitry for Pearce; the schematics are available online.
Old 3 weeks ago
  #11
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@Mikhael

Thank you, I will look in to Pearce.
Old 3 weeks ago
  #12
Quote:
Originally Posted by Jacob_Dworkin View Post
Thank you, @John Eppstein , for your detailed reply.

The overall aim of the project isn't to necessarily have full SS recreation of a valve amplifier system but to increase the efficiency of guitar amplification in general (lower power consumption, smaller size, lower cost components etc.) One aim of the project is to measure the ratio of second harmonic to third harmonic distortion introduced by overdriving valve amplifier systems and recreate that with a transistor pre-amp. With careful consideration to input biasing and transistor choice all research shows that this can be possible.
The problem is that it's not linear and it's always changing dynamically. - and transistors (even FETs) don't work like tubes do when they're outside their range of linear operation.

The other problem is that there are a lot of details that are not given in the part spec sheets, especially concerning non-linear operating modes.

You could do real world analysis of specific parts to try an figure out what's going on, but the devil is in the details.

Th third thing is that it's not just the circuits, a printed in the schematic. In audio amps layout can be crucial, because layout dictates interaction between parts of a circuit, including traces/wiring. There are stray inductances and capacitances. I've seen copies of popular amplifiers that went as far as using original parts ordered from the factory that did not work as intended - sometimes barely worked at all - because the builder did not adhere to the original layout.

Quote:
Most of the sonic characteristics (sag, voicing etc) of a valve amplifier comes from the power amplifier section as apposed to the pre-amplifier section so all research and data collection shows that valve pre-amp tone can be recreated succesfully in with a SS pre-amp, however the SS amp will never behave fully like a valve amplifier if the power amplifier is transistor based, that much is certain.

The Fender tone stack approach to equalisation is a new concept to me so thanks for flagging that up, the thread you have hyperlinked shows scientific consideration to its design and it is greatly appreciated.

As a guitarist myself, placing microphones off-axis is always the best way to go, in no situation (live/ studio) have I ever preferred the response of on-axis, hyper/ regular cardioid microphhones. The microphone and cabinet pairing will determine the frequency response of the cabinet simulation technology implemented, measured with an IR in a DSP environment and recreated with an analogue filter network.

You also raise a good point in which modern overdrive settings are not required much from an amplifier as boost/ drive pedals are common place even in more extreme genres.

All of these points have been take in to account for the initial design stage.

Thanks again,
Jacob D.
Musicman did a pretty good job with their hybrid amps (SS pre/tube power) as far as the clean Fender kind of tone goes. Their later amps used an SS phase inverter, but a lot of people seem to prefer the earlier tube circuit.

I think you misinterpreted what I said about pedals and modern overdrive. Few pedals can really duplicate the handling characteristics of a tube overdrive preamp because transistors do not and cannot go into distortion the same way tubes do. Tubes go into clipping gradually with a soft knee until you really start pushing them hard. Transistors do not soft clip - the knee is always hard.

In my band we use a combination of technologies, using each for its strengths. I don't see much point in trying to force a square peg into a round hole.

FWIW, I spent a good portion of my life as an audio service tech.

Quote:
efficiency of guitar amplification in general (lower power consumption, smaller size, lower cost components etc.)
Well, you can't put out what you don't take in. Smaller size? Well there are a LOT of small "lunchbox" amps around these days. That's plenty small. Any smaller you get into problems both with ergonomics and with things like heat dissipation. plus when you have audio power circuits you need a certain amount or room to avoid thye layout interactions I mentioned previously.

As to lower cost components, DON'T. Just don't. Guitar amps are subjected to considerable stress, both mechanical and electrical and cheap components fail. Take it from somebody who services them. Something else that often seems to be overlooked these days is serviceability. There are a lot of modern amps of all types that are insanely difficult to service, to the point where the labor bill can be over a hundred dollars to replace a 5 cent part. Guitar amps are one of the few remaining areas of electronics where it is expected that an unit can be repaired quickly and economically when it fails.

Last edited by John Eppstein; 3 weeks ago at 11:10 PM..
Old 3 weeks ago
  #13
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For Vox sounds, I like the second channel on the Bad Cat Black Cat or the Matchless DC-30 for most playing, which features an EF86 preamp tube with a 12AX7 in the tone stack position. Most probably prefer the first channel as it has that Vox chime thing going on but the second channel is something that will fit in day in and day out and does not tend to get harsh as the first channel on these amps can (yes they sound great with the best players but you really have to watch your tone and volume controls and your playing). I like these two amps in particular (as they started as the same design by the same designer with the Bad Cat getting modern updates) for note separation and how reactive they are to how hard or light I hit the strings. Fabulous amps and I do not think anyone has bested Mark Sampson's designs yet.
Old 3 weeks ago
  #14
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Quote:
Originally Posted by John Eppstein View Post
Musicman did a pretty good job with their hybrid amps (SS pre/tube power) as far as the clean Fender kind of tone goes. Their later amps used an SS phase inverter, but a lot of people seem to prefer the earlier tube circuit.
I think most people assume the tube in the earlier ones was really a preamp tube when it is not.

I own one of the best examples of a Music Man amp with an HD-150 head and a 412-GS cabinet in about as good of condition as you will find in 2019. Found it very music "festival" sounding live but lackluster when recorded. I would have thought someone by now would have come up with some mods for the solid state preamp. Interesting to me that these have such a low value on the used market that the tubes outside of the amp (four Sylvania 6L6 still going strong) are probably worth more than the amp head.
Old 3 weeks ago
  #15
Quote:
Originally Posted by ozraves View Post
I think most people assume the tube in the earlier ones was really a preamp tube when it is not.

I own one of the best examples of a Music Man amp with an HD-150 head and a 412-GS cabinet in about as good of condition as you will find in 2019. Found it very music "festival" sounding live but lackluster when recorded. I would have thought someone by now would have come up with some mods for the solid state preamp. Interesting to me that these have such a low value on the used market that the tubes outside of the amp (four Sylvania 6L6 still going strong) are probably worth more than the amp head.
Solid State preamps on PC boards do not generally lend themselves to mods, at least not mods done by amateurs. Jim Williams could probably do it. Maybe I might have back when my eyesight was better, but I would probably have passed on such a project, as it would be a bigger PITA than would have been worth my while on a one-off unless the customer had significant cash (and time) to invest. It's not like a hand wired tube amp (like the competing Fenders and Marshalls of the time), which are easy and straightforward to work on and you can swap parts in and out with ease to fine-tune a mod.

I'm not entirely sure I'd want to buy used tubes from a Musicman. They ran their plate voltage WAY higher than maximum spec, to the point where they had to institute special circuit measures to prevent flashover and shorted tubes with burned sockets. They tended to run through power tubes much faster than most other amps.
Old 3 weeks ago
  #16
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Quote:
Originally Posted by John Eppstein View Post
Solid State preamps on PC boards do not generally lend themselves to mods...

I'm not entirely sure I'd want to buy used tubes from a Musicman. They ran their plate voltage WAY higher than maximum spec, to the point where they had to institute special circuit measures to prevent flashover and shorted tubes with burned sockets. They tended to run through power tubes much faster than most other amps.
I was thinking an IC swap. You know how people go nuts over Burr Brown.

I've never had an issue with running through tubes.
Old 3 weeks ago
  #17
Quote:
Originally Posted by ozraves View Post
I was thinking an IC swap. You know how people go nuts over Burr Brown.

I've never had an issue with running through tubes.
Well, IC swaps are easy if there are sockets. Not so easy if there aren't. I don't remember if MM had them or not. Also, sometimes with chip swaps you also need to change some of the supporting parts as well. Especially if you're going from an older, low bandwidth/slew rate chip to a modern one that's much faster.

Well, MMs are pretty hard on tubes and can run through them faster than a less extreme design. I'm not sure what modern tube I'd want to use in that amp. Maybe none, which could get expensive looking for NOS Sylvanias.

Have you considered a speaker swap?
Old 2 weeks ago
  #18
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Check out Evans Amplifiers (I think they sound better clean than any tube amp, but have tube qualities)... as mentioned is possible (sort of), however there will be some differences. When pushed beyond their clean range, saturation will get more and more different.
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