68 board layout question

Info about our boards and kits.

Moderator: VelvetGeorge

Post Reply
wrea398
Senior Member
Posts: 649
Joined: Thu Nov 26, 2009 10:06 am
Just the numbers in order: 7

68 board layout question

Post by wrea398 » Fri Jan 21, 2011 3:35 pm

Hello all. Had a dumb question about the differences in using the 500/560pf capacitors on the board. I am building a 67/68 100w (haven't finished it quite yet) but I decided along the way to use the '68 board layout in Georges board layout section. I noticed that diagram uses the dual 560pf micas on the board. I have yet to see another original amp using this setup or a replica for that matter. Mabey its not too popular a setup? Most I see use the dual 500pf or the 500/250pf combination. Anyone here use the 560/560pf setup and what are your thoughts vs. the more common setups? I know alot of it will be my personal preference. I'm just looking for personal opinions in what I should expect from this setup vs. other more popular arrangements. I am also using the 33k/470k setup and the (7) .022 mustards if this helps. Thanks in advance.

User avatar
toner
Senior Member
Posts: 2582
Joined: Sun Dec 03, 2006 7:57 pm
Location: Iowa

Re: 68 board layout question

Post by toner » Fri Jan 21, 2011 3:52 pm

For the mixer bypass, using 560pF vs. 500pF will lower the high-pass corner frequency slightly so it will pass a little bit more mids (around 600Hz).

560pF in the tone stack will also add mids but higher in frequency, around 1kHz.

Both of these will add a tiny bit of overdrive gain (mainly the tone stack one) but it and the frequency changes will be extremely subtle. You probably won't notice a difference when compared to 500pF.

audioclone
New Member
Posts: 25
Joined: Wed Feb 03, 2010 11:43 am
Just the numbers in order: 7

Re: 68 board layout question

Post by audioclone » Fri Jan 21, 2011 3:55 pm

wrea398 wrote:I am also using the 33k/470k setup and the (7) .022 mustards if this helps. Thanks in advance.
I'm sorry, but what's 33k/470k setup?

wrea398
Senior Member
Posts: 649
Joined: Thu Nov 26, 2009 10:06 am
Just the numbers in order: 7

Re: 68 board layout question

Post by wrea398 » Sat Jan 22, 2011 7:13 am

Tone stack resistor is a 33k and the normal and bright channel mix resistors are 470K. I have heard others ask what you had installed when talking about the 500/560pf micas, so I included this info in my question.

wrea398
Senior Member
Posts: 649
Joined: Thu Nov 26, 2009 10:06 am
Just the numbers in order: 7

Re: 68 board layout question

Post by wrea398 » Sat Jan 22, 2011 7:15 am

Thanks for the quick reply. I just thought it was wierd that NOONE uses this setup as I can find. Thought there might be a better solution for a better reason. I would be interested in a little more mid and gain anyway so mabey I will like this setup. I'm still learning...

toner wrote:For the mixer bypass, using 560pF vs. 500pF will lower the high-pass corner frequency slightly so it will pass a little bit more mids (around 600Hz).

560pF in the tone stack will also add mids but higher in frequency, around 1kHz.

Both of these will add a tiny bit of overdrive gain (mainly the tone stack one) but it and the frequency changes will be extremely subtle. You probably won't notice a difference when compared to 500pF.

Post Reply