ROG Thunderchief HUGE volume issue

[Atodovax]

Hi everyone. Does anyone know how to lower the volume on the ROG Thunderchief? My pedal sounds super but the volume is just super huge. At max, it seems it could actually break an amp

[antonis]

Why you want to do something that isn't supposed to be done..??

Anyway, raise any of (or both) 15k output resistors (right before Volume pot) with simultaneously lowering 2.2nF cap(s) by the same amount/ratio..
Or, just lower Volume pot value under the risk of last stage JFET Drain loading..

[Atodovax]

Why you want to do something that isn't supposed to be done..??

Anyway, raise any of (or both) 15k output resistors (righe before Volume pot) with simultaneously lowering 2.2nF cap(s) by the same amount..
Or, just lower Volume pot value under the risk of last stage JFET Drain loading..

Thanks Antonis, I had to put a 2M2 in series wich the ouput which sounds crazy but actually made it. Even with a 100k or 470k in series the volume was huge. Now it sounds great but there is a slight blowing noise in the background .

Why you want to do something that isn't supposed to be done..??
What do you mean?

[antonis]

Now it sounds great but there is a slight blowing noise in the background .

With a 2M2 series resistor, it should rather sound like a hurricane..

Why you want to do something that isn't supposed to be done..??
What do you mean?

http://www.runoffgroove.com/thunderchief.html

edit: Are you sure about 2M2 series resistor value..??

[ElectricDruid]

Why you want to do something that isn't supposed to be done..??
What do you mean?

He means you're the first guitarist in history to want to turn something down!!

http://www.runoffgroove.com/thunderchief.html
edit: Are you sure about 2M2 series resistor value..??

+1 agree. That's weird. 2M2 would *flatten* the volume here, so there must be something we're missing. Perhaps the OP has the output components wired up wrong somehow, or perhaps the 2M2 isn't connected where we think it's connected. But 2M2 into 100K is -86dB, so that *can't* be right.

[PRR]

The TC can put out over 2V, which is a lot for any amp expecting 20mV-200mV inputs (normal pickups). So it could get loud.

> I had to put a 2M2 in series with the output

To drive what?? If driving one of the older Ampegs with 6.8Meg input, 2M in series hardly takes the edge off; one of the 47k early transistor amps would about go silent.

Series resistor to unknown loads is usually a poor idea. Also tends to a maximum-impedance which may be maximum-hiss and also hum/buzz.

Try somewhat like this:

[Rob Strand]

There's a way you can add an output attenuator without affecting the impedances in the circuit, and in fact without affecting them for any pot setting.




Notice that R1 + (R2 // 100k pot) = 100k

You can use this L-pad attenuator calculator:

http://www.sengpielaudio.com/calculator-Lpad.htm

Speaker Impedance Z:      Enter 100 ohms (enter 100 for 100k, entering 100000 is just making things messy)
Enter attenuation as a positive number (eg 10 for 10dB)
Read off R1 and R2 as if they are in k ohms.

An L-pad attenuator provides attenuation without changing the input impedance.

[ElectricDruid]

> I had to put a 2M2 in series with the output

To drive what?? If driving one of the older Ampegs with 6.8Meg input, 2M in series hardly takes the edge off; one of the 47k early transistor amps would about go silent.

Series resistor to unknown loads is usually a poor idea. Also tends to a maximum-impedance which may be maximum-hiss and also hum/buzz.

Aah! Ok, thanks PRR! I hadn't understood what Altodovax was up to.

I assumed they'd put the resistor in series with the output, but *ahead* of the volume control (so in the position of R1 on Rob's schematic). I assumed that because that's what seems logical to try for me (cut down the maximum volume level using a basic voltage divider, simple enough). Adding a series resistor *after* the volume control makes little sense, as you say.

[antonis]

I hadn't understood what Altodovax was up to.

+1..!!
(almost everyone understood the resistor placed BEFORE Volume pot..)

At least, that was proposed to serve as a voltage divider..

[Atodovax]

Why you want to do something that isn't supposed to be done..??
What do you mean?

He means you're the first guitarist in history to want to turn something down!!

http://www.runoffgroove.com/thunderchief.html
edit: Are you sure about 2M2 series resistor value..??

+1 agree. That's weird. 2M2 would *flatten* the volume here, so there must be something we're missing. Perhaps the OP has the output components wired up wrong somehow, or perhaps the 2M2 isn't connected where we think it's connected. But 2M2 into 100K is -86dB, so that *can't* be right.

Sorry for the delay! I was on a trip. Well i actually have the 2m2 wired in series before the 100k pot. Now the pedal has the perfect volume but 2m2 sure sounds overkill... The volume without any series resistor is just too much. Much more higher than any other distortion pedal i[ve ever tried. Even higher than the highest clean boost running at 24v

[Atodovax]

I hadn't understood what Altodovax was up to.

+1..!!
(almost everyone understood the resistor placed BEFORE Volume pot..)

At least, that was proposed to serve as a voltage divider..

Sorry, the resistor is in fact before the volume pot acting as a divider. It just seems overkill to put such a high value there. Also the hiss got quite loud with the resistor there. But without any resistor, any setup over the first turn of the volume pot is just HUGE!
The volume pot is bearly usable. I tried lowering the volume pot also but i know that would mess with the output impedance so i was trying to keep the output impedance more or less the same by adding something before the pot...
ROb , i will try what you suggest and report back. I hope i can make it work with less hiss. Thanks everyone

[Rob Strand]

The volume pot is bearly usable. I tried lowering the volume pot also but i know that would mess with the output impedance so i was trying to keep the output impedance more or less the same by adding something before the pot...
ROb , i will try what you suggest and report back. I hope i can make it work with less hiss. Thanks everyone

I'm pretty sure the hiss will go.

About your volume pot issue: Are you sure you are using a 100kA (log taper)?  If you have a 100kB (linear taper) it's certainly going to make controlling the level a lot harder.   The pedal output level is probably high but that *and* a 100kB will make it just that little bit more difficult to adjust the level.

[Atodovax]

The volume pot is bearly usable. I tried lowering the volume pot also but i know that would mess with the output impedance so i was trying to keep the output impedance more or less the same by adding something before the pot...
ROb , i will try what you suggest and report back. I hope i can make it work with less hiss. Thanks everyone

I'm pretty sure the hiss will go.

About your volume pot issue: Are you sure you are using a 100kA (log taper)?  If you have a 100kB (linear taper) it's certainly going to make controlling the level a lot harder.   The pedal output level is probably high but that *and* a 100kB will make it just that little bit more difficult to adjust the level.

Thanks Rob, i double checked and its a logaritmic taper pot. Its without doubt the loudest pedal i've ever built , and i've built quite a lot of pedals. I also checked every component. It seems its the nature of the pedal. I wonder if adding the tonestack would lower the volume enought to a normal level. Anyway i will try your sugestion tomorrow and report back

[Rob Strand]

Thanks Rob, i double checked and its a logaritmic taper pot.

I just thought I would mention it.  The divider/l-pad has to work.  It's essentially a better wheel of what you have already done.

[antonis]

I wonder if adding the tonestack would lower the volume enought to a normal level.

A Big Muff style tonestack would lower the volume to about -12dB..
There is much more road till -86dB..

[duck_arse]

two questions - can we see this thing? and - can you measure the resistance to ground at the 2M2//pot junction, please?

[Atodovax]

I wonder if adding the tonestack would lower the volume enought to a normal level.

A Big Muff style tonestack would lower the volume to about -12dB..
There is much more road till -86dB..

Why do you say -86db? Isnt 2m2 in series to de 100k pot producing a -10db attenutation?

[Atodovax]

two questions - can we see this thing? and - can you measure the resistance to ground at the 2M2//pot junction, please?

Sure, will take some pics tomorrow. The resistance to ground is essentially de 100k pot. I dont mean that de 2m2 is not working. Its working perfectly fine. I was curious on how such a big value was needed there to lower the volume on this thing. But im going to try the L pad attenuator tonight and report back

[antonis]

Why do you say -86db? Isnt 2m2 in series to de 100k pot producing a -10db attenutation?

-27dB..!!
[20*log(100k/2M2+100k)]

-86dB correspond to 22000 attenuation which comes for Volume pot almost full CCW.. 

[anotherjim]

Your lucky the pedants don't query that two-point-two milliohm resistor value...oops I fell into the trap! 

Anyway, could it be the negative feedback in the design isn't working? That would make it louder than intended I think.

The path back via the 2n2 and 100k I mean, are those parts wired in good?