PPIMV

[geoff 1965]

check this demo for a PPIMV using PEC pots!
he say's the price of the PEC's is justified as they have a very good tonal balance at low volume compared to alpha's which can sound harsh at low settings.
has anyone tried them?
https://youtu.be/vypgBhGQwJA

[crgfrench]

That guy has one impressive collection of insulated screwdrivers...

[colossal]

I've used dual gang PECs for PPIMVs for a long time. They are up to the task both for tone and quality (having each side well matched to the other). They are pricey of course. That said, I am at a bit of a crossroads with master volumes and specifically PPIMVs. I have found [PPIMVs] to affect the sound (and even add noise) and prefer to leave them out in favor of a pair of fixed resistors, whenever possible. They are a useful tool, however. I would recommend PECs over Alphas or other pots, especially for this application. Your mileage and utility may vary, of course.

[geoff 1965]

thank's for the info colossal,i've tried the spitfire type ppimv with a 1meg pot and that did add noise also the scope and low volume was'nt that good.
i have the one from the forum downloads at present but with a dual 1meg pot and 820K grid leaks in parallel to be closer to the stock 470K.
very good scope and tone at low volume plus the versatility of cleaning up or driving the el84's.
i've yet to find a CTS or alpha dual pot with a balanced and accurate resistance,they can be as much as 100K difference on the 1megs!

[colossal]

thank's for the info colossal,i've tried the spitfire type ppimv with a 1meg pot and that did add noise also the scope and low volume was'nt that good.

Yes, those crossline PIs make a mess of the PI's balance and are kind of an on/off switch, rather than a proper, gradual decline in volume.

i have the one from the forum downloads at present but with a dual 1meg pot and 820K grid leaks in parallel to be closer to the stock 470K.
very good scope and tone at low volume plus the versatility of cleaning up or driving the el84's.

That's the one I use with an 18W (dual 1MA || 887k fixed grid leaks).

i've yet to find a CTS or alpha dual pot with a balanced and accurate resistance,they can be as much as 100K difference on the 1megs!

Yes, they are not good. PECs are usually very close to the nominal value and the dual-gang pots within a few kΩ of each other. Expensive yes, but very important for that application.

[crgfrench]

I'm going to try these PECs.

Parenthetically, a pet peeve of mine is the term "PPIMV" because the first "P" could just as easily mean "Pre-" or "Post-". Its not a specific abbreviation.

[colossal]

I'm going to try these PECs.

Pricey little suckers but if you must have the control, they are the ones to use. Their rated 10% precision is usually very close. I bought a 300k Alpha recently because I needed 300k (!) but it turned out to be 250k

Parenthetically, a pet peeve of mine is the term "PPIMV" because the first "P" could just as easily mean "Pre-" or "Post-". Its not a specific abbreviation.

Great point! One of those annoying internet propagations that unfortunately stuck.