The PPIMV (Post-PI-Master-Volume) thread.

[hotguit]

Hi
i'm going to install a PPIMV (larMar) on my '75 1959 SL.
My head has stock EL 34 tubes, 82K grid res instead of 220K and 0,022 output caps.
I have read somewhere in this thread that i should use a dual gang 100K log pot and two 470 K safety resistors instead of the 250K dual pot and 2,2 M res.
Well, that is ok; my question is: do i have to replace the 0,022 output caps with two 0,1 caps as suggested (don't remember where i read it) in this thread or i can let in place the stock caps (0,022)?
In LarMar's layout the caps are in fact 0,1.
Who can help me to well understand that?
thank you
hotguit

[Roe]

keep the 22s if you like 'em. If you want more deep bass, try 100s

[neikeel]

Best compromise is 0.047s IMO

[halebox]

WORKS GREAT BUT HUGE VOLUME LOSS WHEN MASTER CRANKED. I just put a larmar in my very loud 1983 JCM 800 4 hole NMV 1987. Its a cheapie dual 250 pot that measures 170 and 163. I am using 1.5 ohm 2% resistors? I had the correct resistors but I plugged in with the speaker jack not all the way pushed in and I think the 2.2's fried so I put these ones in. Im not sure it was getting full wattage when the 2.2's were in there. Anyone know whats wrong here? It sounds very good but its like a 10 watt amp now. I plan to get better pot in there.

[Harold]

I am using 1.5 ohm 2% resistors?

I hope you mean 1.5 mOhm as in 1 500 000 Ohm?

[halebox]

Ok problem solved. I bought proper resistors but that wasn't the problem. I believe there was a wire touching on my mini dual pot. I did get shocked when looking for problem with amp on I pulled softly on black and red wire going to r23 and r24 to make sure those were connected right. Sounds great!

[halebox]

Who makes the best dual 250 pot and where can I order one?

[cebix]

Quick question. 2006 1987X, LarMar, pot placed in the speaker jack hole - the pot itself gets quite warm, about the same temperature as the heat when touching the back grill. Is this normal?

Thanks in advance for any replies.

EDIT: Oh and I've played virtually 99% of the time at bedroom volumes with this amp for the past year and everything is great. Great mod.

[julkke]

Quick question here too. Could the PPIMV be installed to the indicator light hole without any PO issues etc?

[gloeidraad]

Hello Julkke,that is no problem aslong as you use shielded wire.

Erik

[SteadyEddie]

What's good shielded cable that's easy to use for a PPIMV?
I used this stuff and it's giving me problems: http://www.belden.com/techdatas/metric/9271.pdf" onclick="window.open(this.href);return false;
Belden twinaxial shielded. Has a foil shield. The cable started getting noisy on me.
I had it lying around and it worked for almost two years no problem. Now my volume started dropping. When I tap on the cable now, the sound cuts in and out like it's got some sort of internal problem.
So I'm going to change it out, but with what?
I use a lot of Belden 8723 at work. It's a 22 gauge, twisted pair, each pair is shielded. I can double up on the conductors. Would that be good enough?

[gloeidraad]

I always use RG 174-U,thats a single wire shielded coax,but thats because i have a spool with 100meter on it.
Its not to thick and flexible,and low capacity.

[Harold]

I always use RG 174-U,thats a single wire shielded coax,but thats because i have a spool with 100meter on it.
Its not to thick and flexible,and low capacity.

I was told the RG174-U wire was way too flimsy (26AWG) to act as PPIMV wire here: http://www.gitaarnet.nl/forum/showthrea ... ost2895372" onclick="window.open(this.href);return false; (should be readable to you)

I replaced the wiring with twisted 18AWG which seems to keep the low end better intact, but I could be fooled into thinking that.

http://img.tapatalk.com/d/12/10/31/yge9e5aj.jpg" onclick="window.open(this.href);return false;

[gloeidraad]

I dont know,but Larry recommended this wire somewhere on page 17 of this thread,and its working fine for me.

Erik

[SteadyEddie]

I replaced the wiring with twisted 18AWG which seems to keep the low end better intact, but I could be fooled into thinking that.

http://img.tapatalk.com/d/12/10/31/yge9e5aj.jpg" onclick="window.open(this.href);return false;

That's what I just did. Twisted it up good with a drill. I don't hear any oscillations at all.
I haven't had a chance to crank it up for any decent amount of time to determine whether there's any change in tone or not.
But it looks cleaner.