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

[CoffeeTones]

The 2.2M = safety resistors
5.6k are already there usually
You can re-use the green and orange wires twisted together for shielding or not, but would be better to use shielded wire.

[riff19]

Will the 5.6k resistors be in a JTM45? If so, what do they look like? Do I just leave them where they are?

What would re-using & twisting the green & orange wires be used to shield? What do they shield? Where would this go? Is there a picture illustrating this setup?

Thanks!

[CoffeeTones]

Not to be rude, but for your safety maybe you should have a tech do the mod. If you can't figure these simple things out, maybe you should not be messing around inside the amp. I will also add that if you do not discharge the amp, it could electrocute and kill you.

I will try to help, but don't want to lead you to injury.

[djseban]

Hi,
I've just finished my #34/#36 amp, and I consider mounting Lar/Mar PPIMV. I've one question about cables on pot. In metroamp wiki,

Code: Select all

http://metroamp.com/wiki/index.php/Lar/Mar_PPI-MV

I can read, that if you are mounting PPIMV, you have to use RG174/U as your cable for mod. Is this really necessary to use this type of cable? I've asked for this in all electronics stores in my city - they say, that they don't have it in stock.

Regards

[neikeel]

Hi,
I've just finished my #34/#36 amp, and I consider mounting Lar/Mar PPIMV. I've one question about cables on pot. In metroamp wiki,

Code: Select all

http://metroamp.com/wiki/index.php/Lar/Mar_PPI-MV

I can read, that if you are mounting PPIMV, you have to use RG174/U as your cable for mod. Is this really necessary to use this type of cable? I've asked for this in all electronics stores in my city - they say, that they don't have it in stock.

Regards

It is not mandatory, just that you have long wires with lots of signal passing through the middle of your pre-amp making cross talk and interference more likely. Using a decent shielded wire (not necessarily this type) is a good idea, you may get away with it, or not

[djseban]

Hi,
I've just finished my #34/#36 amp, and I consider mounting Lar/Mar PPIMV. I've one question about cables on pot. In metroamp wiki,

Code: Select all

http://metroamp.com/wiki/index.php/Lar/Mar_PPI-MV

I can read, that if you are mounting PPIMV, you have to use RG174/U as your cable for mod. Is this really necessary to use this type of cable? I've asked for this in all electronics stores in my city - they say, that they don't have it in stock.

Regards

It is not mandatory, just that you have long wires with lots of signal passing through the middle of your pre-amp making cross talk and interference more likely. Using a decent shielded wire (not necessarily this type) is a good idea, you may get away with it, or not

Thanks for reply, I drilled a hole near impedance selector and mounted PPIMV. It's working perfectly, by first try, even without shielded cable.

Regards

[syscokid]

... you have to use RG174/U as your cable for mod. Is this really necessary to use this type of cable? I've asked for this in all electronics stores in my city - they say, that they don't have it in stock.

Where are you located?

[coldengray]

I installed the LarMar MV in my JTM45 last night and I seem to notice more gain now...is this normal?

[CoffeeTones]

There should not be more perceived gain if the LarMar is turned all the way up, unless the resistors and pot in parallel do not equal the original value of the two resistors removed from the original circuit. Turned down, yes.

[stef]

I installed the LarMar MV in my JTM45 last night and I seem to notice more gain now...is this normal?

Yes it is normal, the gain increase comes from lowering the NFB via PPIMV. It should also sound looser and brighter, fizzier etc

[coldengray]

Yes, turned below Noon it gets fuzzy and loose. And definitely more gain the more the MV is used. But certainly a very usable solution. Noon or higher it really shines. Thanks for the help. Love this amp!

PS - yes when turned completely up everything is back to "normal". And loud!

[coldengray]

Would increasing the 47pf PI cap help smooth the fizziness when the LarMar is engaged heavily?

[stef]

Yes, increasing it should help, but what worked best for me was removing that MV all together

[Roe]

Would increasing the 47pf PI cap help smooth the fizziness when the LarMar is engaged heavily?

I'd rather increase NFB. try a 22k resistor in series with a 220k pot into the 16 ohms secondary

[coldengray]

Yes, increasing it should help, but what worked best for me was removing that MV all together

It doesn't color the tone too much at 50% or higher...it's certainly a usable solution for me considering it only cost $10 in parts. I might try out a Phaez Brink attentuator.