Secret to tight gain when modding? (2204 content)

[Kapo_Polenton]

What is the secret to tight bass when you are doing gain mods? I wanted to hotrod one of my 2204 builds because I have a PTP and it is easy to play around with things. I have done the following;

common fat/lean switch (.022 vs .0022) on first coupling cap. Maybe I need to go even tighter?
fixed resonance off the NFR Friedman style (220k, 0047 cap) coming off my 47 K resistor to 4 Ohm tap.
V1 plate resistor value 110K in series with 220k for total 330k.
1 uf cap over 820 R on V2
V1b 10K to 5K on a switch for more gain

It all sounds good when the preamp is set to around 7 but after that, it goes to mush at around 9 and sounding almost like a fuzz at full gain. I also tried a .68 bypass cap on V1b and I got some oscillation. ( I know 100-500 pf cap over the 330k in V1 is supposed to help with that but its still messy sounding) I’m just wondering what additional tricks of the trade are used to keep it all from falling apart at higher preamp/gain settings? I look at the Friedman and Ceriatone stuff and I know their circuits are even more gained out. How is it not woof city when dimed? Or do those circuits sound crappy/ fall apart past 8 as well? I thought of maybe just bypassing the 10K resistor on V1b with a 1uf as I know that crisps it up but I am interested in how other hot rodded Marshall style amps accomplish this.

Thanks amp nerds!

 

[psychodave]

It’s the sum of all the parts, not just one or two changes.

The one thing I see is that 220k/.0047 depth circuit. That cap adds in a lot of sub lows. .002/.003 will sound more Marshall like. I’d also suggest wiring in a pot and letting your ears tell you what to use. Also, use a ceramic cap here.

 

[SpiderWars]

What psychodave said.

Plus, try smaller cathode bypass caps like .47u instead .68u. 1uf is getting about as big as I go but Cameron among others uses those (again, sum of all parts). In addition your voltages will affect it.

Also, do you have the 470k//470pf treble peaker in there?

Adding a big cap like 1uf or .68uf across the 10k is a massive gain boost and 1uf pretty much covers all guitar frequencies.

Also look at those other circuits you mentioned, yes there is a lot of gain but alot of it is dumped to ground. That compresses the signal so it doesn't kick the next stage in the nuts.

 

[fusedbrain]

All great info posted so far
Other things to try:
On the 470k //470pf + 470k voltage divider going to V2a - Try lowering the value of the resistor to ground. 220k or lower.
If you are going to bypass V2a cathode + lower V1b cathode from 10k and / or bypass that resistor, you may want to scale back on the 330k @ the V1 plate. 220k is usually enough with the above tweaks.
Try adding a grid stopper to V1b between the gain pot and the grid. Try 220k or 470k.

 

[Kapo_Polenton]

What psychodave said.

Plus, try smaller cathode bypass caps like .47u instead .68u. 1uf is getting about as big as I go but Cameron among others uses those (again, sum of all parts). In addition your voltages will affect it.

Also, do you have the 470k//470pf treble peaker in there?

Adding a big cap like 1uf or .68uf across the 10k is a massive gain boost and 1uf pretty much covers all guitar frequencies.

Also look at those other circuits you mentioned, yes there is a lot of gain but alot of it is dumped to ground. That compresses the signal so it doesn't kick the next stage in the nuts.

Yes still have the 470k/470pf peaker there. i am trying to keep it as raw and as Marshall as possible without changing too much of the tone.

Some good info though here guys.. also I know every amp is a bit diff so you have to tweak values here or there to taste.

On the 470k //470pf + 470k voltage divider going to V2a - Try lowering the value of the resistor to ground. 220k or lower.

What does this do? Is this sending more of the signal to ground in order to reduce the bloat?

 

[fusedbrain]

On the 470k //470pf + 470k voltage divider going to V2a - Try lowering the value of the resistor to ground. 220k or lower.

What does this do? Is this sending more of the signal to ground in order to reduce the bloat?

Yes.

Another take when bypassing V1b & V2a is to leave the above mentioned divider alone, and replace peaking circuit from low input to gain pot with 470k / 220k voltage divider and add pf value cap to taste over 470k. The latest "Red Dragon" amp uses 560pf cap with voltage divider at this location.

 

[mixn4him]

The other thing to consider is voltages, what are your drop resistors? Keeping the Voltage up a little helps keep things tight with that much gain. If you have 2 10k's after the choke maybe lower to 15k or just the single 10k..

 

[Kapo_Polenton]

The other thing to consider is voltages, what are your drop resistors? Keeping the Voltage up a little helps keep things tight with that much gain. If you have 2 10k's after the choke maybe lower to 15k or just the single 10k..

Plate Voltage on this specific amp is 397. It seems kind of low I guess in comparison to what people post online but in stock 2204 the thing sounds fantastic to my ear. With gain mods, falling apart. Doing a quick search I see people feel the lower voltage amps are "spongier". Mix of Sozo and mallories and silver mica. Stuff I have lying around. carbon film and carbon composite. I think you guys are right though, probably too much signal getting through and I need to dump some to ground along the way.

Bright cap is another interesting one. I think I've got a 500pf on there. I see they can go quite high value wise but thinking that doesn't address the low end flub. Coupling caps prob have more impact I would think.

 

[SpiderWars]

Just my opinion but the fuzz/flub is probably elsewhere than the coupling caps. And if you go too far with coupling caps (going too small) the amp doesn't have the right tonal spectrum. It might sound OK playing a certain riff but move around on the fretboard and it just doesn't sound right everywhere.

I think the lower voltages can work, especially on the plexi-type circuits but (again just my opinion) the higher voltages seem to work better on the JCM800 type circuit.

 

[Kapo_Polenton]

I also have gone down to a 47 k NFR in the past to give it more of that plexi characteristic but I understand a part of that JCM800 tone is also that tight grindier 100k in that position. Thankfully this is a PTP, so easy to patch things in and out for shits n giggles.I might go back and simplify because regardless of gain, I find I really like boosts and always seem to tighten things with an OD anyway. It is a tricky balance between retaining that kick ass JCM800 big raw sound with upping the gain and getting more modern tone, or more of a loose and flubby/compressed gain done wrong sort of deal.

 

[nico22]

Would try a res from gain wiper to ground , from 68-82k to 330k.
Or like fusedbrain said 220k in // with gain pot, ala jel Friedman...

 

[V2a]

What is the secret to tight bass when you are doing gain mods? I wanted to hotrod one of my 2204 builds because I have a PTP and it is easy to play around with things. I have done the following;

common fat/lean switch (.022 vs .0022) on first coupling cap. Maybe I need to go even tighter?

The low-frequency roll off depends not only on the value of the coupling cap but also on the output impedance of the previous stage and the resistive load following the coupling cap. The BE has a tight low end, but the 2n2 coupling cap is followed by 136k load (68k series R and 68k shunt R). Since the resistive load is a lot higher in the 2204 (470k series into a 1M gain pot), you need to lower the coupling cap quite a bit to get the same low-freq roll off.

Example: Egnater seminar amp has a 220k plate resistor (stage 1) and a 2204 type gain-pot configuration following the first coupling cap. The tight switch lowers the value of the coupling cap to 750p or so.

 

[V2a]

Also, you might want to add a bright switch so that you have a switchable bypass cap around the series portion of the gain pot. Try a 2n2 bypass cap, which will increase gain of mids as well as highs. Set your gain to 7 to keep the low end low and engage the bypass cap to maximize gain at higher frequencies.

 

[FourT6and2]

Your voltages are too low if the amp's B+ is under 400. If you want it tighter, you wanna see somewhere around 480v B+ and no lower than 160-170v on V1a plate.

Other than that, you could try what others suggested and run a voltage divider from the second stage feeding V1b grid. 68k/68k with a small cap in parallel to the resistor going to ground to kill some high end fizz. The higher the value of the resistor going to ground, the less signal it will bleed. So you can experiment or just use a pot. But the secret to getting TIGHT gain is to use LESS of it.

 

[Kapo_Polenton]

Your voltages are too low if the amp's B+ is under 400. If you want it tighter, you wanna see somewhere around 480v B+ and no lower than 160-170v on V1a plate.

Other than that, you could try what others suggested and run a voltage divider from the second stage feeding V1b grid. 68k/68k with a small cap in parallel to the resistor going to ground to kill some high end fizz. The higher the value of the resistor going to ground, the less signal it will bleed. So you can experiment or just use a pot. But the secret to getting TIGHT gain is to use LESS of it.

Love it, reminds me of something Miyagi Sensei might say to Daniel if he actually knew how to play that guitar he beat Steve Vai with in Crossroads... Agreed though, I don't need gobs of gain. I prefer less overall.

 

[FourT6and2]

Your voltages are too low if the amp's B+ is under 400. If you want it tighter, you wanna see somewhere around 480v B+ and no lower than 160-170v on V1a plate.

Other than that, you could try what others suggested and run a voltage divider from the second stage feeding V1b grid. 68k/68k with a small cap in parallel to the resistor going to ground to kill some high end fizz. The higher the value of the resistor going to ground, the less signal it will bleed. So you can experiment or just use a pot. But the secret to getting TIGHT gain is to use LESS of it.

Love it, reminds me of something Miyagi Sensei might say to Daniel if he actually knew how to play that guitar he beat Steve Vai with in Crossroads... Agreed though, I don't need gobs of gain. I prefer less overall.

 

[CornNutz]

You're probably slamming a stage with too much signal. You get blocking distortion that flubs, and farts out.

fusedbrain's suggestion is on the right path. You can dump some signal like that.

You might also consider .0022uf coupling on the second stage too.

 

[GlideOn]

I've tried a lot of above mentions on my YBA-1, which has a lot of 2203 (more accurately 2204) voicing and gain going on. I also run KT77s for deeper bass (more on that in other thread).

Ended up being VERY stiff but extremely tight and musical.

Controversially, I did all of this and then added a 100w 130hm sag resistor in between mains filter and rectifier and this was the magic velvet touch it needed to 'relax' the amp a bit while retaining tightness.

Of course my end goal was to still have a somewhat old-school brownsound going on, but I find it still very aggressive yet refined for modern styles.

I lost about 10% of total output, but works in my favor as the amp was just insanely ear-bleeding loud before.

YMMV.

 

[Kapo_Polenton]

Found this yesterday and thought I might add it to this thread in the event that anyone else down the line might be looking for more tips. Gives a good overview.

 

[SpiderWars]

That's pretty cool. Have you checked out the Rockstah Mod 5 (which allegedly came from Larry or even Chris Merren before that but I digress lol)?