Trying out different V1a and Tone stack

JimiJames · Post by **JimiJames** » Fri Jan 31, 2014 11:43 pm

It will be a little while until I can listen to this. I want to record and post a clip.
I changed out the RS 270pf to a SM 500pf. Trying out a 220μ cathode. Have the 330μ off to the side in this pic.

mightymike · Post by **mightymike** » Sat Feb 01, 2014 7:37 pm

If you leave one of each cap desoldered, then you can jumper wire one, play a little bit, then jumper the other cap, then play a little bit. This way the difference will be fresh, rather than a month apart with a different tone stack cap to boot. Just saying

Roe · Post by **Roe** » Sun Feb 02, 2014 5:40 am

220 or 330uf doesn't matter. if you measure the 220 it may read 300, and the frequency response is virtually simular anyway, boosting sub-human lows

neikeel · Post by **neikeel** » Sun Feb 02, 2014 5:58 am

Roe wrote:220 or 330uf doesn't matter. if you measure the 220 it may read 300, and the frequency response is virtually simular anyway, boosting sub-human lows

Yup. 10uF makes a moderate difference and 4n7 significant difference at least to my ears, now what the visceral non-aural frequency is affected when you stand in front of a cranked stack and hit a big open A - I do not know

JimiJames · Post by **JimiJames** » Sun Feb 09, 2014 12:19 pm

Thanks guys ! mucho appreciato !

O.K. took it for a test spin....
Liked it better with a 330μ so I'll rewire that back and take back out the 220μ.
I'm still having issues now that this build is near 3 years old. I'll order and resource some parts then rewire everything back to stock, but leave the PPIMV (when playing out.)
I also want to swap out the .0022 for a .022 and hear what happens.
What would give me that hollow - boxy sound. (like speaking into a can)
That's what I need to get rid of. Would it be a leaky cap ? - very annoying
(I'll try recording and post a clip next time around )

JimiJames · Post by **JimiJames** » Thu Feb 20, 2014 9:39 am

I went in with a lighted magnifying glass and could not find any leaky caps.
I'm gonna' order some electrolytic's and change some filtering....
aaarrrg ! where's my tone !

JimiJames · Post by **JimiJames** » Thu Feb 20, 2014 1:57 pm

Were 220's early spec (V1 w/820) , then 330μf later ?

JimiJames · Post by **JimiJames** » Thu Mar 06, 2014 10:28 am

I swapped out those two Blue ITW 0.68's (200v) with Mustards, and I also found a RS 470pF to replace the SM 500pF.
Made no difference... Here's a sample of the issue I'm having : https://soundcloud.com/user5906127/boxy-amp-tone
sucks !

Strat78 · Post by **Strat78** » Sat Mar 08, 2014 1:39 am

I hear what you are struggling with there. Did you try two 32uf's for the screens yet? Back off on the vol1 a bit and see if it gets a little bite back in the tone. Bright cap?

JimiJames · Post by **JimiJames** » Mon Mar 10, 2014 1:42 am

Nothing on the bright cap but here is the amp I built http://home.comcast.net/~jbjdav26/1959/ ... l%20B+.JPG Thanks SDM !

I have on the 8Ω tap & I have one of those blue ITW 0.68μ's on the Presence where a .1μ should be.
Everything else is to print.

I just received the F&T cans in the mail yesterday (Thanks ValveStorm !), so I'll put it on the bench and get to work on it today.
I'd have to take it back to the jam spot to turn the amp up to band levels. I'll record another clip then.
I'll know something after that so later in the week if work permits.

Leave the PI cap alone ? I have spare 32+32μF...

maxwedge572 · Post by **maxwedge572** » Mon Mar 10, 2014 2:47 am

You definitely need to leave the 470/500pf in there as long as you have the 33k slope resistor as in the schematic. With the 270p you loose a lot of mids. Check out the Duncan Ton Stack Calculator and you can see the changes in the tone stack.
http://www.duncanamps.com/tsc/

It does sound odd but I don't think that the problem is in the preamp. How is the master volume set in that clip? I'd by-pass that and test, but I know it'll be loud. Never been a fan of those tone suckers!

That's my guess anyway.

JimiJames · Post by **JimiJames** » Tue Mar 18, 2014 6:13 am

...hmm.... no... I do not have a Vol.1 bright cap...

My head must be in SB mode as the do not have bright caps at all....

I took'er for a test spin through a 12" Fender Blue label I had lying around...sounded decent with none of that boxy sound...
Going to the jam spot tonight and record a new sample...
Things changed :
ALL Mustard's now

0.10 Mullard on the way for Presence
RS 470pF on tone stack
F&T 32μF+32μF x2 on Screens
fresh 12'er of Stella

~Jimmie

syscokid · Post by **syscokid** » Sun May 25, 2014 12:44 pm

JimiJames wrote: I also want to swap out the .0022 for a .022 and hear what happens.

Did you ever do this swap?

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