Tight Metal huge volume

[JackSkellington]

Hey, guys!

I'm building the Tight Metal on a verified veroboard layout I found. I'm testing the circuit, it works fine and sounds really good, but the volume is HUGE. I can't go over 2/10. It's really strange. Every schematic I found suggest a B10k Volume pot, but it's impossible use this normally.
The schematic is this:



The loop effect in my case are jumpered.
I can see the resistor to the ground near the output 47k in another schematic and 33k in Grind Custom FX's schematic.
I know the Tight Metal includes a 18v Charge Pump, too. But the layout I used doesn't have it. I'm gonna include it on a daughter board later.

Need some help, please.

Thanks!

[mjg]

Hey,

Yeah, it's a loud one.  I just got mine out for a quick shred (it's lots of fun), but I didn't need the volume past about 20%.  I guess if you had some of the more extreme scoop settings, with a minimum gain setting, you might need a bit more volume.  But I agree, for most settings the volume is best turned way down. 

(I'm using the Grind Customs version.   Entered it in Build of the year for 2017, so you can have a look at the video from that, and hey look, the volume never goes over a quarter in my demo.    http://graybloomfield.com/guitar/2017/03/31/brutalist/the-brutalist-demo/  )

[mjg]

I guess if you used an A10k for the volume, that might spread it out a bit nicer in the low end?

[JackSkellington]

Then, it's really loud!
I guess it, too, about the log pot. Unfortunately, I didn't have a A10k pot, now.

After I tried the stock schematic I'll try to replace the trash switch with a the Scoop control. I already have the external Gate pot and the switch. Then I have to wait for the daugther board.

[JackSkellington]

I tested my Tight Metal, again. This time with PSU, (last time I tried just the battery). No changing, of course.

But the volume pot is unsuable! I can't set it at 9 o'clock, because the volume is really loud. If I get the volume pot of the amp I can hear the effect sound.
Looking at the schematic what happend if I change something? For example:

Volume pot: B10k -> B20k or B5k? Maybe Log, but what about the value?
R38 100k: Do it set the overall volume? Could I use a 47k or a 33k?
R3 475k (I used 470k): What happend if I use a 320k?

[mjg]

I would try a A10k pot first, to see if that makes it useable. 

Other things that I would try:

- is the gain of that final op amp being set by the 'volume' pot?  If so, maybe there would be less gain if you change R32 and R33.  Not sure, but if you make them lower it might be less gain?  (Or higher? I generally just try it and see  )

- R36 seems to bridge the output and ground, so changing that to something lower would reduce the overall volume I think.
-R38 is also one to try changing, as you mention. 

(Actually, looking at it again... if you aren't using the send/return loop, you could replace R36 and R38 with a single resistor, about 30k or 33k.  Try lowering that value to see if it drops the volume?)

[mjg]

I don't think R3 is doing much if you don't use the send/return loop.  I suspect you could probably leave out R3 and R4, and jumper C4 and C5.  But don't quote me on that.   

[mjg]

One more thing I would try... Put a more conventional volume right at the end, which does the usual of blending between output and ground.  It would be an A100k, or whatever you normally use.  The existing volume pot in the circuit could be replaced with a trimmer, or fixed value resistors, then just use the new volume pot at the end to control the overall volume. 

[JackSkellington]

Thanks for the answer, I'm a bit anxious.
I don't want "twist" too much the schematic, but looking at the Aeons by Grind Custom FX, we have just one resistor before every loop effect.
In the schematic I used:
- R3 475k, but I used a 470k (on socket). I could use a 330k, Aeons has a 320k.
- R4 1M, I can leave it out. Aeons don't have it.

And:
- R36 47k. I could use a 33k like in the Aeons.
- R38 100k, I can leave it out. Aeons don't have it.

But in both the cases there's something of redundant, because I can adjust those values like Aeons, but actually it's already like that. Indeed:
475k||1M = 322k
47k||100k = 32k

I prefer don't touch R32 and R33, I don't want change the amount of the gain.

The trick trimmer/final pot could be the last chance.

Anyway, today I'm gonna try with a A10k pot (I had one for another project ). Then I could try with a smaller pot like a 5k linear, the one I have. I should turn it about at 9 o'clock, maybe. And even a 2k could be good, in this case absolutely linear as the one I have.
With the stock 10k linear I'm using I can use just the 10%, really hard to set the volume fine. At less than 1k it's louder then bypass.
I hope to solve with that A10k pot!

I have to say just one thing, I still didn't do it, but I would change the trash control with a scoop pot like in the Aeons.
Here the schematic: