Silent Stage Guitar amp

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I think some simulators are starting to get pretty good, and probably the best of them run on a (powerful) PC. Lots of computing horsepower to run fairly sophisticated mathematical models.
And with decent quality ADC/DACs.

In the real world, if I chain a distortion and a delay or reverb pedal, I can find some settings that magically smooth out the harshness from the distortion. On my Zoom G3, I can't find a setting like that.
Agreed. My Zoom is collecting dust.

I spent a bit of time a decade or two ago with non-linear modelling tools (shock and vibe analysis) and we learnt two things quickly: one, NLM takes a shedload more computing power; and two:the models themselves are much more complicated if you want to actually match reality.

Stuff like all the interesting "intermod" issues (such as B+ ripple/sag in PP amps and speaker thermal compression) which we've only really (re)discovered in the last decade and the modellers won't have even tried to model.

There's another thread here somewhere looking at trying to get a decent MOSFET model for Spice. You'd have thought that would have been solved back in the eighties but it's still a problem once you move from "the normal" operating areas and are interested in low level effects.

I was looking at the curves for an 807 last night(from STC June 1954 Sydney). Not nice, even in the negative grid area (there's a kink around Vp=150V, Vg=-20, Vs=250). Push into positive grid area and it's all over the place.

Then you want to start modelling cone break up or cabinet flex? Good luck trying to model that meaningfully.

Actually, that's hopefully my next little project: playing with small speakers to emulate "stacks" behaviour but at sub one watt power levels. Right now the "real" world is keeping me far, far too busy to complete existing projects nevermind start new ones :(
 
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I think some simulators are starting to get pretty good, and probably the best of them run on a (powerful) PC. Lots of computing horsepower to run fairly sophisticated mathematical models.
-Gnobuddy
Which ones, specifically, do you think are "pretty good"? The ones I've tried (Line 6 and Tascam) are just way too "gimmicky" sounding to me and don't even approach the real thing.
 
Which ones, specifically, do you think are "pretty good"? The ones I've tried (Line 6 and Tascam) are just way too "gimmicky" sounding to me and don't even approach the real thing.
Agree with you entirely about the Line 6 stuff. I wasted good money on a couple of them. Stupid me.

I've also wasted money on awful-sounding Digitech pedals. And less-awful Zooms that are still sufficiently bad that they just sit in my closet.

I've never tried a Tascam. And I've never tried any of the recent, relatively good ones, because they cost more than a DIY valve amp! That makes zero sense to me, so I build my own amp(s).

But, from the clips I've heard, the Atomic Amplifire sounds considerably better than previous generations of modelling pedals: YouTube

On the software side, this demo of BIAS FX software sounds interestingly less-bad than a lot of older modelers: YouTube

Also give this a listen: YouTube

-Gnobuddy
 
one, NLM takes a shedload more computing power; and two:the models themselves are much more complicated if you want to actually match reality.
I don't doubt you. In the last two decades, though, we have been given the gift or shedloads more computing power - the difference in speed between the PC I used in 1997 and the five-year old Core i5 I'm using right now is absolutely staggering. Many orders of magnitude.

Heck, for the last year or two, it's been possible to buy a quad-core, 1.2 GHz computer for $35 USD - the Raspberry Pi 3. (Of course we in Canada, you in Australia, are not so lucky!)

I think the second part of the equation - the quality of the software models - is probably going to be the big question mark. Guitar sounds have more or less vanished from popular music, the music industry is mostly dead, far fewer people are buying electric guitars, and I'm not sure how much incentive anyone has to continue to work on improved mathematical models for valve amps.

But, if my ears are any judge, the better models have certainly improved in the last few years.

There's another thread here somewhere looking at trying to get a decent MOSFET model for Spice. You'd have thought that would have been solved back in the eighties but it's still a problem once you move from "the normal" operating areas and are interested in low level effects.
Yeah, and it's the same story with vacuum tube SPICE models. Some of them kinda-sorta work, but I rarely bother simulating valve circuitry, because the simulations don't match reality very well.

It's quite a different story with "classic" semiconductor devices, though - opamps, diodes, and whatnot. My experience there is that if it works well in the simulator, it will usually work well when I build it in real life.

Actually, that's hopefully my next little project: playing with small speakers to emulate "stacks" behaviour but at sub one watt power levels.
I would be very interested in your results when you eventually get to it!

Quite coincidentally, I spent an hour or so earlier today designing and simulating an analogue filter to roughly mimic the published frequency response of a guitar speaker. The idea was to have this follow some sort of valve preamp, acting as a speaker emulator, and feed the output into a flat frequency response speaker (or P.A. system).

I think I got fairly close using a 3-opamp circuit (images attached). Same x-axis scale, same range of y-values, plots as close to the same size as I could manage, so you can compare them by eye.

I haven't built it, but the simulated frequency response looks fairly close to the real speaker.

Right now the "real" world is keeping me far, far too busy to complete existing projects nevermind start new ones :(
I know the feeling. :(

-Gnobuddy
 

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You could "cut a whole new door and walk through" the problem by buying a Fryette GPDI recording amp which will do exactly the silent stage thing. I have one and it's really remarkable how versatile it is. Inductive speaker load built in, all-tube, meant for direct injection into a recording console so it ought to be just fine in a live situation. Really sounds like an amp because it is a complete amp from preamp to power amp to speaker to XLR output. As a side bonus, it is capable of 1 watt power output to a speaker for times when you want to hear what you are doing through a normal speaker.
I'm thrilled with mine.
It's a little tabletop thing, about the size of a cigar box, no visible speaker, it looks like just a chassis.
 
My amp has two jacks for outputs.

I wired an 8 ohm 20 watt resistor to a 1/4" plug so I can pull the speaker plug out of the jack and plug the dummy load in easily.

I wired the other output jack to the secondary of the 70v transformer I had on hand.

I input a 1v 1kHz sine wave to the various primary taps until I found ~100mV on the secondary, I got 120mV, close enough. That gives me a 8.33:1 turns ratio or a 69.4:1 impedance/inductance ratio.

I then put a 1.2k resistor and the primary of the 70v transformer in series and placed my signal generator across them. I put the scope probe across the transformer and changed the frequency until I found the -6db point, which was 800Hz. That gives me an inductance of 238mH.

I simulated it and it showed roughly what I want, cut lows and highs. Certainly doesn't resemble a speaker much but it actually sounds pretty good. I hooked the output up to a self powered PA speaker and played through it. I think it will get me through the practices coming up.

Eventually I want to make and effects box like gnobuddy did with his opamp circuit except I want to use tubes and make it have ~5%THD. That way I can get the warmth of tube distortion and the frequency response of a speaker.
 

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You could "cut a whole new door and walk through" the problem by buying a Fryette GPDI recording amp which will do exactly the silent stage thing. I have one and it's really remarkable how versatile it is. Inductive speaker load built in, all-tube, meant for direct injection into a recording console so it ought to be just fine in a live situation. Really sounds like an amp because it is a complete amp from preamp to power amp to speaker to XLR output. As a side bonus, it is capable of 1 watt power output to a speaker for times when you want to hear what you are doing through a normal speaker.
I'm thrilled with mine.
It's a little tabletop thing, about the size of a cigar box, no visible speaker, it looks like just a chassis.

This is the type of device I am leaning towards. BUT I am not spending $800 for one. I think I can make a 1 watt amp with passive filtering to resemble a speaker and mic for less than $100 depending on the chassis I use.
 
Which ones, specifically, do you think are "pretty good"?

If you have a PC or Mac with an audio interface that can eat a 1/4 inch guitar cable try the free demo of TH3 from Overloud.

It is the full version of the software limited to 10 minute sessions, or two weeks with registration. It will take more that 10 minutes to explore everything. There are zillions of models,including amps, guitars, stomp boxes and cabinets. You graphically drag them onto a canvas and connect them up. I made a setup with two different effects chains that can be blended back together with a MIDI volume pedal before feeding the amp and cabinet. There is also a looper included.

The software can function standalone, or as a plugin for most DAWs. The full manual is on their web site for download.

Home | Overloud

I use an Audio4 USB interface from iCONNECTIVITY and you can just plug the guitar into the front panel. I have an old MOTU MicroBook II, it works too.
 
famousmockingbird,
Yes, definitely nothing budget about the Fryette. It is, though a great piece of gear to own for any number of situations.
If you can ever find an Award (or Morley) JD10 Jerry Donahue guitar preamp pedal, it also is made for recording without an amp or speaker. They have been out of production for many years so you may or may not be able to find one, but it will also do the job. I like them so much that I bought three of them over a stretch of time. Paid between $125 and $200 for each one.

Here's just one example. It may be gone by the time you read this though...
Award Session JD-10 Jerry Donahue | eBay
 
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I want to use tubes and make it have ~5%THD. That way I can get the warmth of tube distortion and the frequency response of a speaker.
This is something I have been wanting to do for some time now. If you ever come up with a design you like, I hope you'll share!

My reason for wanting an amp in a tiny box that plugs into the P.A. is simply that I often play acoustic guitar, electric guitar, and electric bass at our jams, as well as sing, and I ran out of enthusiasm for hauling around three amps plus a P.A. system, plus microphones, plus mixer, plus my guitars, each time.

My acoustic guitar has an onboard piezo pickup and preamp, so it goes direct into my little mixer. My bass goes through an ART Tube MP/C preamp ( ), and then into the mixer. But I haven't yet managed to get the electric guitar to sound right going into the P.A. So something like that Fryette, that I could build for about one tenth of the price, would be nice!

By the way, for guitar, I found that as much as 20% - 30% distortion (mostly second harmonic) still sounds clean for single-note playing, particularly at lower volume, when our ears are less sensitive.

There are cheaper options than the Fryette - the Joyo American Sound (which may or may not be a Sansamp rip-off, depending on whom you ask) is one of them: Joyo American Sound JF-14 Pedal | CheaperPedals.com

There are a couple of videos on that page featuring the Joyo, including one that's a comparison of the Joyo vs. a real Fender amp.

I have the American Sound, and found it more likable than any of the digital amp emulators I've tried (it is an all analogue product). But I didn't like it enough to keep on using it.

For six times the price, there is the Tech21 Fly Rig 5 (which is officially a Sansamp, which some people speak highly of): Tech 21 Fly Rig 5 Multi-effects Pedal | Sweetwater

-Gnobuddy
 
you may have to start a blog of your adventure to keep us updated!
i'm certainly interested in what you end up with, and your perspective on it all.


Certainly. I will at the very least start another build thread once I have things simulated and breadboarded. I am thinking a flea watt amp with inexpensive power tubes and iron.

I'd love to hear what you come up with. I wonder if one of the pedals mentioned, going into your tube device, would be a good combination?

Are you talking about the Custom Comp? It's a big part of my overall sound and will always run it into my rig. My understanding is it's a Dynacomp but with the original metal can 3080 and some internal controls. I love it. I will probably always keep the TS9 and Custom Comp in my arsenal.
 
I was actually thinking more of the amp-like pedals but of course you have to include your go-to pedals that you always use. This is going off-topic but it's quite impressive what happens when you add a boost pedal like an OCD into an amp-like pedal that is set for a light crunch tone.
 
I am thinking a flea watt amp with inexpensive power tubes and iron.
I have been tinkering with a preamp design based on inexpensive NOS small-signal triode-pentode tubes. I'm currently using a 6JW8.

The "pentode" in the 6JW8 appears to actually be a little beam tetrode, like a very small 6V6 (1.2 watts max plate dissipation). Good, because I love the sound of the 6V6, and other beam tetrodes have some family resemblance to their sound.

I've plotted some load-lines that suggest that something like the Musical Power Supplies OT5PP (22.5k anode-to-anode primary impedance) would work with a pair of the little beam tetrodes, with about 160 - 180 volts for B+ voltage (and output power probably just a few hundred milliwatts).

But my initial experiments simply use a single 6JW8, with the beam tetrode running single-ended, and a resistor as the anode load. We're only looking for enough output to drive a P.A. input, so why bother with an output transformer?

The tetrode has quite high voltage gain (around 50x, if I recall correctly) with the resistive load. So the triode in the 6JW8 actually has more than enough voltage gain to drive the little tetrode well into overdrive when fed from a guitar.

So just one tube is enough to make what amounts to a micro-Champ, triode input stage, "pentode" output stage, with just milliwatts of output power.

(I think you will also might need another triode gain stage if you do use an output transformer, as the tetrode will have less voltage gain than it does now.)

Currently I run the output of the beam tetrode through a tone control circuit (could be the usual Fender one if you like), and then to a pot that acts as a master volume. The output from the pot currently goes to my thunderously powerful 2-watt 6AK6 push-pull power amp ;), and then to an actual loudspeaker. But it could probably go through a speaker emulator into a P.A. system instead.

It works well for clean tones and slight overdrive, but gets a bit ratty and harsh if you turn it up all the way to maximum gain, so I still have some work to do tweaking the circuit. But I think it shows promise.

-Gnobuddy
 
Inspired for a second I thought I could do a quick little one tube guitar amp with a 12V laptop supply, a high voltage booster bought online and a 7258 tube. It has a pentode and triode in it and I thought to use the triode as the output stage. Looked up some Hammond transformers and what they would cost in town. A reverb transformer replacement was $25 but other than that everything was $50 and up. I am guessing they are setting their prices at what you could buy the item and have it shipped in for. Hammond transformer 125ASE (3W).

Angela, $42.75 US (53.24 CAD)

Locally, $62.90 CAD
 

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The "reverb" transformer is very appropriate for a 2 Watt tube at 100V-150V and 7mA-15mA.

Pentode-Triode has too much gain up front and a too-polite power stage. I would work triode preamp and pentode as "power" stage. About 1/3rd Watt out.

This is still a bit shy on gain. (1V into 7258-P grid, Gv=14 in 7258-T, 70mV pk or 50mV rms input sensitivity). I had a way to use-up excess 6AU6 (or 12AU6).
 

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