Tone stack/coupling cap mods?

11 Gauge · November 21st, 2006, 01:13 PM

Most of my amps seem to run .022 uF caps for the midrange stuff - a little too high in the mids for my tastes.

I guess I'm mainly a BF/SF Fender amp guy, but the .047's seem like they'd be a little too deep for the .022-based amps I have.

How about .033 uF? A good compromise? I'd like to know before I gut anything...

Stan Martin · November 21st, 2006, 01:32 PM

.033 is a good compromise. btw what is the value of the other cap? I'm assuming a .1mf.

Bob Arbogast · November 21st, 2006, 02:46 PM

I tend to prefer .047uF for both the bass and mid caps. I also use a 100k pot for the bass control. That extra 150k in the stock bass pot is wasted as far as I'm concerned.

On my closest-to-BF amp I actually have .022uF caps and a 56k slope resistor -- very much like a 5F6A Bassman, except for the 100k bass pot.

Bob Arbogast

11 Gauge · November 21st, 2006, 02:53 PM

the other cap almost always tends to be another .022. and the slope resistor is almost always a 33K. maybe I'll start by knocking the slope resistor up to a 47K and take it from there. The Marshall I just got has a 1 meg bass pot! anything above 2 and it becomes a bass amp (with a .022 cap and 33K slope)!

thanks for the tips. I'll work incrementally to bring the mids down on a few of these projects...

Tremo · November 21st, 2006, 05:15 PM

You can download the tone stack calculator and play with cap and resistor values, and see what the results are.

jjmantele · November 23rd, 2006, 11:07 PM

Blue (bottom) line is 0.100u (100n) Mid Cap
Green above that is 0.047u (47n) Mid Cap
Green above that is 0.033u (33n) Mid Cap
Green on top is 0.022u (22n) Mid Cap

It looks like, as you increase the value of the mid-cap, you are scooping out more of the lower requency mids while the amount of upper-mid scooping remains the same. My '71 SFDR uses .047 (47n) for the mid cap, although the mid "control" is set to "6.8" since it uses a resistor instead of a knob.

Dowload the calculator. It is very cool.

maestrovert · November 24th, 2006, 10:07 AM

Quote:

Originally Posted by Tremo

You can download the tone stack calculator and play with cap and resistor values, and see what the results are.

Would you please post the link for us dummies ?

Thanx !

DrewB · November 24th, 2006, 10:14 AM

http://www.duncanamps.com/tsc/download.html

11 Gauge · November 24th, 2006, 11:47 AM

I use Macs, so I guess I'm missing the boat on this one...

I'll start by messing with the slope resistor and take it from there, 1st at 47K, next at 56K, then up to 68K. Hopefully I won't have to go any higher than that...

November 21st, 2006, 01:13 PM	#1 (permalink)
11 Gauge Friend of Leo's Join Date: Mar 2003 Location: The East Coast Posts: 3,015 10 Photos	Tone stack/coupling cap mods? Most of my amps seem to run .022 uF caps for the midrange stuff - a little too high in the mids for my tastes. I guess I'm mainly a BF/SF Fender amp guy, but the .047's seem like they'd be a little too deep for the .022-based amps I have. How about .033 uF? A good compromise? I'd like to know before I gut anything... __________________

November 21st, 2006, 01:32 PM	#2 (permalink)
Stan Martin Tele-Holic Join Date: Mar 2003 Location: Pepperell Posts: 810	sure .033 is a good compromise. btw what is the value of the other cap? I'm assuming a .1mf.

November 21st, 2006, 02:46 PM	#3 (permalink)
Bob Arbogast Tele-Holic Join Date: Mar 2003 Location: Columbus, Ohio, USA Age: 48 Posts: 538	My prefs I tend to prefer .047uF for both the bass and mid caps. I also use a 100k pot for the bass control. That extra 150k in the stock bass pot is wasted as far as I'm concerned. On my closest-to-BF amp I actually have .022uF caps and a 56k slope resistor -- very much like a 5F6A Bassman, except for the 100k bass pot. Bob Arbogast

November 21st, 2006, 02:53 PM	#4 (permalink)
11 Gauge Friend of Leo's Join Date: Mar 2003 Location: The East Coast Posts: 3,015 10 Photos	the other cap almost always tends to be another .022. and the slope resistor is almost always a 33K. maybe I'll start by knocking the slope resistor up to a 47K and take it from there. The Marshall I just got has a 1 meg bass pot! anything above 2 and it becomes a bass amp (with a .022 cap and 33K slope)! thanks for the tips. I'll work incrementally to bring the mids down on a few of these projects... __________________

November 23rd, 2006, 11:07 PM	#6 (permalink)
jjmantele Tele-Holic Join Date: Aug 2003 Location: New Jersey Posts: 850	Blue (bottom) line is 0.100u (100n) Mid Cap Green above that is 0.047u (47n) Mid Cap Green above that is 0.033u (33n) Mid Cap Green on top is 0.022u (22n) Mid Cap It looks like, as you increase the value of the mid-cap, you are scooping out more of the lower requency mids while the amount of upper-mid scooping remains the same. My '71 SFDR uses .047 (47n) for the mid cap, although the mid "control" is set to "6.8" since it uses a resistor instead of a knob. Dowload the calculator. It is very cool. __________________ JJman If it says "Vintage" on it -it isn't.

November 21st, 2006, 05:15 PM	#5 (permalink)
Tremo Friend of Leo's Join Date: Mar 2003 Location: Silicon Valley, CA, USA Posts: 3,767	You can download the tone stack calculator and play with cap and resistor values, and see what the results are.

November 24th, 2006, 10:14 AM	#8 (permalink)
DrewB Tele-Afflicted Join Date: Feb 2005 Location: Independence, MO Posts: 1,086	http://www.duncanamps.com/tsc/download.html __________________ There is no substitute for Sound Pressure Level

November 24th, 2006, 11:47 AM	#9 (permalink)
11 Gauge Friend of Leo's Join Date: Mar 2003 Location: The East Coast Posts: 3,015 10 Photos	I use Macs, so I guess I'm missing the boat on this one... I'll start by messing with the slope resistor and take it from there, 1st at 47K, next at 56K, then up to 68K. Hopefully I won't have to go any higher than that... __________________