Solid state preamp with tonecontrol

[Domin9797]

Hi, i want to make my own solid state amp from preamp and poweramp chip and i want to make some good preamp with tonecontrols. I tried BJT designs, jfet preamp emulators , even opamp based but nothing sounds like i want it to... jfets sounded best but the ones i have are too powerfull, when i bias them to 1/2 of PS i cant get clean tone. Sound im looking for is clean, with gain maxed little bit dirty but not too much, maybe 2 gain stages, classic tonestack and what i can clean up with turnign volume down on guitar. Any ideas? I tried Alembic Fet2B, i liked it most, but i had to omit 47uF bypass caps parallel to resistors because i got overdrive not clean sound. There is how i would like it to sound (intro) https://youtu.be/Dhfy9TPga-c

[joecool85]

Great sound on that intro, I can see why you want to emulate this.  Honestly though, it shouldn't be too hard.  The Honey amp can sound like this with gain turned up about 1/4 to 1/3 (depending on what pickups are on your guitar).  I feel like this is yet another issue where tone stack in many preamp designs shared online are garbage.  A lot of times, tone stack before the heavy gain stages can fix your drive sound issues.

If you want to play with some stacks and adjust a circuit, check out TSC in the web: https://www.guitarscience.net/tsc/info.htm

I generally like a gentle sweep mid cut centered around 500hz as a good starting place.

[Tassieviking]

I would find clips on Utube and other places, read forums etc to find an amp I like the sound of, and then go from there.

I made a PCB for the Marshall 12watt amp because its popular and sought after, I posted the gerber files somewhere on this site for the PCB files.
If you are just after the pre-amp then you could easily build it on a Solder-less Plug-in Breadboard to try it out, change the tone stack and gain components etc.

How complicated do you want to go ? A simple pre-amp or multi channel pre-amp ?
What sort of power are you going to run it at and is it for home or are you going to use it in a band etc ?

[Domin9797]

You mean Marshall Lead 12? I tried to breadboard it but something went wrong and didnt sound right. I measured all caps and resistor but i couldnt find what was wrong...
I want just clean preamp with gain around Sunn Model T, not high gain, for high gain i have pedals. I made Sunn Model T Jfet version from Coda Effects but since my Jfets are quite higher gain, it sounded horrible. I found one design of preamp which use Jfet but with different gate bias method followed by BJT buffer going into tonestack and then same Jfet/BJT stage again, for now i breadboarded just first stage and tonestack and its nice clean but with bypass cap on source its again too gainy even if i roll down volume. I want it for home use, just some playing for fun. I have TDA7297 poweramp pcb which i want to isw with 9 or 12v

[Tassieviking]

Re you sure you want a clean preamp ?
I though the SUNN Model T was more suited for grunge, doom, stoner, drone, sludge type of music.
Then again that is what most people use the SUNN BETA amps for but they can put out some nice clean sound as well if set right.

Try looking at lots of SUNN BETA youtube clips to see what you think of that one, it can sound similar to a SUNN Model T.(Try to find a clean sounding clip)

SUNN BETA amps are all IC's with a couple of FET's for switching channels, they get a bit more complicated but you can buy PCB's for stompboxes for one channel that can drive a power amp.
You can even find veroboard layouts for them if you look around, I am thinking about making a PCB to fit one in a 12"x3"x8" Hammond case with a class D power amp in it for a Bass Amp. (500watt @ 4ohm)

[Domin9797]

But same as Fender Bassman it can be quite clean...i like lots of tones, i like to play some sludge metal too so it wont harm to have Sunn Model T preamp I found just one clip where is Sunn Beta Lead in clean, even preamp pedal but its hard from one video. For now i dont have CMos chips it uses and not so big and quality breadboard.

[Tassieviking]

If you bought a PCB for a pedal you can still run leads to the pots and mount them in a case like a real looking amp, just use some supports under the PCB so it keeps steady.
The TDA7297 will give you about 12 watts at 9V or 14 watts at 12v, you can get a TPA3116D2 MONO amp module fairly cheap that can run off an old laptop power supply.
I have a 3116D2 mono module in a 125B box with a tiny fan that I run from a 19v laptop supply on my bench, I can give it 26 volts and get 100watts from it.
It looks just like a small stompbox and will run on voltages from 4.5 volts to 26 volts.
15 watts from 12 volts if you are camping.

https://tagboardeffects.blogspot.com/2016/03/sunn-beta-preamp.html
https://aionfx.com/project/beta-preamp/
https://dirtboxlayouts.blogspot.com/2020/08/sunn-beta-pre-amp.html
https://pcbguitarmania.com/product/sun-beta-lead/

[Tassieviking]

I forgot, BAJAMAN  has made a number of circuits for preamps over on Free Stompboxes,
https://www.freestompboxes.org/index.php?sid=244283fce956bdeb138bb1af61af85ef

Check his 59 Bassman layout, it might be worth a look, all his designs are made for stompboxes but you could adapt them for mounting in a box.
https://www.freestompboxes.org/viewtopic.php?t=28915

I think BajaMan must have designed a dozen or two of these circuits emulating popular amplifiers and they get some good praise.
You could carry a dozen different amps in a small case in stompbox form.
Cheers
Mick

[Domin9797]

Yeah but often shipping costs more than PCB. TPA3116 is good choice too but im not sure if i want PA which cant sound "good" while clipping. I have only 20W speaker so im little bit limited.
I know about his circuits. His MDR will be my distortion channel or at least distortion pedal. Im not sure about 59 Bassman since there arent any sound clips of it. Another idea is his Orange emulator

[joecool85]

Yeah but often shipping costs more than PCB. TPA3116 is good choice too but im not sure if i want PA which cant sound "good" while clipping. I have only 20W speaker so im little bit limited.
I know about his circuits. His MDR will be my distortion channel or at least distortion pedal. Im not sure about 59 Bassman since there arent any sound clips of it. Another idea is his Orange emulator

Personally I don't worry about clipping the power amp.  You can design the preamp in such a way (utilizing diode clipping for instance) that you can't clip the power amp section no matter how hard you drive the front end.

[Domin9797]

Thats truth but Sunn Beta Lead preamp doesnt use diodes and output is strong enough to saturate TPA...often i use resistor in series with volume pot so i have smaller range of volume

[Tassieviking]

According to the SUNN BETA service manual:
The Sunn Beta has 1.75v P-P out at the master line output, but each individual channel has only 1.1v P-P at the preamp line output.
Sunn Beta basically has 3 effect loops.
If you made a single channel the output to the power amp is only 1.1v P-P which should be ok, and you don't have to crank the volume pot all the way around.

If anything you might not get enough signal to drive the TPA chip to full power since the Beta figures are peak to peak.

[Domin9797]

I went with this preamp, clean all the way up, clipping is mostly from my LM386 power amp https://static1.squarespace.com/static/56a5a0e242f55268768a0c2b/t/59275264be6594ad0823dc71/1495749220225/MM+HD+Pre.png

[Tassieviking]

That one looks like a nice simple circuit to make, should not cost too much to make.
Please show us all some pictures of your build when you finish.
Good luck

Cheers
Michael

[joecool85]

According to the SUNN BETA service manual:
The Sunn Beta has 1.75v P-P out at the master line output, but each individual channel has only 1.1v P-P at the preamp line output.
Sunn Beta basically has 3 effect loops.
If you made a single channel the output to the power amp is only 1.1v P-P which should be ok, and you don't have to crank the volume pot all the way around.

If anything you might not get enough signal to drive the TPA chip to full power since the Beta figures are peak to peak.

I think it should be OK.  The TPA3116 has gain from 20 to 36db.  I haven't done the math to verify, but I think this should get close.