bass frequency response in a twin.

[Chickenwings]

I'm always looking for ways to beef up the low end (my amp is a 1969 ab763 twin).
Using the "Duncan Tone Stack Calculator" http://www.duncanamps.com/tsc/index.html I noticed that by decreasing the value of the bass/mids cap (.047uf) i can raise the peak of the bass frequency from around 10-20hz up to about 50-60 hz with much more control over the all important 100hz frequency. It would also add lower mids.
Looking around ive found that the super reverb has a .022uf cap in the place of the .047uf. Why did fender do this? Has anyone tried doing this in a twin?
The cap im talking about in this diagram would swapping the .047uf for a .022uf such as that found in an ab763 super reverb.
It would be a super easy mod in an old PTP type amp.

 

[MetalManiac]

Re: bass frequency response in a twin.

I learned awhile back that if I don't have anything nice to say about CBS silverface amps, then don't say it. So I won't say anything.

 

[Chickenwings]

Re: bass frequency response in a twin.

Tune your guitar, then say whatever you like jerry.

 

[AlexR]

Re: bass frequency response in a twin.

Oooh, snap!!!

Does the bass response have to be hardwired into the amp??
Would an Eq pedal do the trick?

 

[Chickenwings]

Re: bass frequency response in a twin.

yeh. I try to have as little as possible in my signal chain. Sold off my eq anyways.

 

[misterwhizzy]

Re: bass frequency response in a twin.

If I were in your shoes, I'd probably put both on a SDPT switch. Play a while, flip the switch, see what the difference is. To answer your question, though, I'm not sure what the difference is.

 

[the guy who invented fire]

Re: bass frequency response in a twin.

What speakers are you running in your TR?

 

[the guy who invented fire]

Re: bass frequency response in a twin.

I learned awhile back that if I don't have anything nice to say about CBS silverface amps, then don't say it. So I won't say anything.

-Peter Green
-Jeremy Spencer
-Danny Kirwan
-Mike Bloomfield
-BB King
-David Gilmour
-Pete Towshend
-Jeff Beck
-Albert Collins
-Jack White
-Joe Perry
-Marc Ford
-Tom Petty
-Mike Campbell
-Eric Clapton
-Johnny Marr
-Keith Richards
-John Lennon
-George Harrison

This is just a short list of guys that use or have used Silverface Fender amps...now, stop douching up the forum and if you don't have anything useful to add to a thread go bust another POS parts Strat into pieces or maybe do something constructive like learning how to tune a guitar to vacuum your floor.

 

[MetalManiac]

Re: bass frequency response in a twin.

-Peter Green
-Jeremy Spencer
-Danny Kirwan
-Mike Bloomfield
-BB King
-David Gilmour
-Pete Towshend
-Jeff Beck
-Albert Collins
-Jack White
-Joe Perry
-Marc Ford
-Tom Petty
-Mike Campbell
-Eric Clapton
-Johnny Marr
-Keith Richards
-John Lennon
-George Harrison

.

Serious? Those guys played those sh*t terrible glassy scrub amps??
I wouldn't touch one. God-aweful, IMHO.
DO YOU even know the difefrences between a blackface and a Silver?!?? I can tell you if you want, casue I know, and it aint pretty.
NO..you cant really "Blackface" a silverface either. depite what you may think.
You can kinda sorta, but your dreming if you think a silverface in any way shape or form resembles a Blackface, and yes, even the early Silverface Deluxes..HUGE differences..wanna bet?

 

[Chickenwings]

Re: bass frequency response in a twin.

Christian: Texas heats. I love them - much fatter than the weber californias that i had in before. They have plenty of bass to give, and i can squeeze tons more low end out using various pedals. Id just like to get more low end running thru the eq circuit, rather than artificially squeezing more in via pedals.. As you know, all i use in the signal chain is either a fuzz face or nothing at all - i find the fuzz sounds best with nothing either before or after it in the chain. Hmm while im at it, i might swap out the cap in my fuzzface (hartman 108) for a bit more bass too. Its currently .001 so i'm thinking of going for .047 or maybe even .01 like analog mike did in my sunface.

oh yeh...you can add jimi hendrix to your list of CBS fender users for jerry.

 

[the guy who invented fire]

Re: bass frequency response in a twin.

Serious? Those guys played those sh*t terrible glassy scrub amps??
I wouldn't touch one. God-aweful, IMHO.
DO YOU even know the difefrences between a blackface and a Silver?!?? I can tell you if you want, casue I know, and it aint pretty.
NO..you cant really "Blackface" a silverface either. depite what you may think.
You can kinda sorta, but your dreming if you think a silverface in any way shape or form resembles a Blackface, and yes, even the early Silverface Deluxes..HUGE differences..wanna bet?

Sure...I got a few seconds to waste...tell me everything you know about it!

- - - Updated - - -

Christian: Texas heats. I love them - much fatter than the weber californias that i had in before. They have plenty of bass to give, and i can squeeze tons more low end out using various pedals. Id just like to get more low end running thru the eq circuit, rather than artificially squeezing more in via pedals.. As you know, all i use in the signal chain is either a fuzz face or nothing at all - i find the fuzz sounds best with nothing either before or after it in the chain. Hmm while im at it, i might swap out the cap in my fuzzface (hartman 108) for a bit more bass too. Its currently .001 so i'm thinking of going for .047 or maybe even .01 like analog mike did in my sunface.

Interesting...I dunno where to go short of some small mods then.

The Texas Heats (in my limited experience) are pretty robust in the lows so you might be on the right track.

 

[MetalManiac]

Re: bass frequency response in a twin.

Sure...I got a few seconds to waste...tell me everything you know about it!

Hang on Bozo, I'm looking for it.

 

[Chickenwings]

Re: bass frequency response in a twin.

I guess i'm after more low end than most ppl use cos i play in two different outfits where there is either no bass player, or a bass player only rarely.
Here is a plot of how the mod should affect things. The red line is stock at .047uf, the cyan is .022uf and the green one is .01uf. The tone controls are set at 7,5,3 (b,m,t)

 

[the guy who invented fire]

Re: bass frequency response in a twin.

I guess i'm after more low end than most ppl use cos i play in two different outfits where there is either no bass player, or a bass player only rarely.

Hmm...I feel ya.

 

[Laughing Kookaburra]

Re: bass frequency response in a twin.

Not in the same conundrum as you Cam, but I do keep hearing good things about Texas Heats, which may serve me in the future...

 

[Chickenwings]

Re: bass frequency response in a twin.

yeh man heats are killer. Cannabis rexes are sweet too in lower wattage amps.

 

[glassman]

Re: bass frequency response in a twin.

Changing the .047 to a .022 in the tone stack is going to raise the midrange center frequency by a couple hundred Hz...probably not a direction you want to go in unless more projection is your goal. The tone stack is probably the wrong area to work in anyway; the Fender design passes some very low frequencies already and if you attempt to pass even more, it will come out as pure mud. The frequency limiter in a Fender is the phase inverter.

Here's what I'd do: First, make certain you are using a 12AT7 in the PI and not a 12AX7; a 12AX7 loosens lows in comparison to a 12AT7. Second, swap out the .1uF @200v cap in the tail side of the PI with a larger value; this will extend the frequency response of the PI. I'd start with a .22; I've tried up to a .68 in that position but at that value, the lows are so powerful that I could only use it with certain guitars. You may want to consider a little more screen limiting (470 ohm to 1k ohm) to make sure things stay under control with the extra bass frequencies. Also, this doesn't shift the EQ, it only expands the range; all of your previous mids and highs are still there.

You may want to put this on a switch; like one that adds another cap in parallel with the one that's already there. That way when you do have a bass player, you're not eating up all of his territory.

 

[glassman]

Re: bass frequency response in a twin.

Another thing you might want to do is to drop the value of the capacitor on the last node of the power supply from a 20uF to somewhere around an 8uF or 10uF; this will serve to round out the bass a little more and make it sound more like you would expect a bass to sound. It actually can make the bass frequencies feel a little more powerful.

 

[MetalManiac]

Re: bass frequency response in a twin.

eff silvers

 

[nedcronin]

Re: bass frequency response in a twin.

I have to laugh at SF fender bashers. Unless you are some guy who owns a BF and insists on feeling great about it. I've owned both and I have NEVER understood the SF bashing. Gimme a break. Ever a linear master volume SF sounds better than 90% of amps made today or yesterday.