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

[danman]

@bmwfreq...you can replace the nfb resistor with a potentiometer of a lower value than the resistor. Wire it as a variable resistor and not a voltage divider. This will allow you to dial in a bit of extra nfb voltage when you turn the ppimv down. You will want to add a small resistor in series with the pot to prevent you from dialing in too much nfb. From memory I believe that I have used a 10k (linear) pot with a 5k series resistor with good results.

[novosibir]

The NFB resistor value has to be at least twice of the resistor's value below the slope R to ground, otherwise the poweramp will oscillate

[djseban]

Hey there,

In my 2203 I recently moved PPIMV to the front (left from Presence pot above the filter cap with 56K resistors on it), but since this I experience problems with oscillation - when I slowly increase PPIMV pot, the amp starts to do these windy noises/crackling and sometimes pops. Usually I don't go above 25-30%. Does anyone have idea on what might be the culprit? I use very fine shielded wire. I also tried relocating the PPIMV pot to the back - problem totally gone, dimed the pot without an issue. I'd be grateful for any insight on this. I thought about interference with filter cap and presence pot, but I am not sure, maybe the wires going to swampers (5k6) on EL34s are too long?

[danman]

The wire leading from the board to the presence pot can cause problems in a stock amp if it's not routed properly. It may be that your PPIMV pot being so close to the presence pot is causing the issue. It's weird since you did use shielded wire but that's the only thing that I can think of.

[ESR]

Hey there,

In my 2203 I recently moved PPIMV to the front (left from Presence pot above the filter cap with 56K resistors on it), but since this I experience problems with oscillation - when I slowly increase PPIMV pot, the amp starts to do these windy noises/crackling and sometimes pops. Usually I don't go above 25-30%. Does anyone have idea on what might be the culprit? I use very fine shielded wire. I also tried relocating the PPIMV pot to the back - problem totally gone, dimed the pot without an issue. I'd be grateful for any insight on this. I thought about interference with filter cap and presence pot, but I am not sure, maybe the wires going to swampers (5k6) on EL34s are too long?

I hope Danman's response it helpful to you. On a different note, I've been curious for a while about how a PPIMV would sound on a Master Volume circuit. So, am I correct in assuming that you have your PPIMV wired in as an *additional* master on top of the original stock master on the front panel? In other words, you've got a preamp gain knob, an original master volume control, AND a PPIMV... yes?

So, if this is the case, I've always thought that you can use the preamp gain knob to adjust how much "sizzle" you want, while using the "stock" master volume to slam your phase inverter with the full onslaught of the preamp... then use your PPIMV to dictate overall volume output of the amp...

Is that how yours works? Good results? Details?

[novosibir]

@ djseban - you haven't specified, what kind of PPIMV you've installed, what pot value.
Keep in mind, that a PPIMV's pot value of 2*500K is much more sensitive and hence much more prone for cross talk or picking up stray fields than a 2*250K pot like i.e. the LarMar PPIMV

And yes, keep an eye to the routing of the violet Presence wire and keep it far away of the PPIMV's wiper and their cable as well as far away of the OT's primaries.

[djseban]

I hope Danman's response it helpful to you. On a different note, I've been curious for a while about how a PPIMV would sound on a Master Volume circuit. So, am I correct in assuming that you have your PPIMV wired in as an *additional* master on top of the original stock master on the front panel? In other words, you've got a preamp gain knob, an original master volume control, AND a PPIMV... yes?

So, if this is the case, I've always thought that you can use the preamp gain knob to adjust how much "sizzle" you want, while using the "stock" master volume to slam your phase inverter with the full onslaught of the preamp... then use your PPIMV to dictate overall volume output of the amp...

Is that how yours works? Good results? Details?

Yeah, that's basically how it's done - regulating the signal coming out from PI to power amp, everything before that can be as stock as it gets. Personally, preamp-wise, I have hot-rodded 2203/#34/#36 modes in preamp and I can say PI distortion is vital for attaining the tone I want. Of course, having master on 7 and PPIMV rolled to 3 won't sound like full-blown master on 7, nevertheless it's still better than having no PPIMV. Recently I played on my friend's stock 2203 clone with MV and Gain dimed and I'd say it was one step away from being considered high-gainish.

@ djseban - you haven't specified, what kind of PPIMV you've installed, what pot value.
Keep in mind, that a PPIMV's pot value of 2*500K is much more sensitive and hence much more prone for cross talk or picking up stray fields than a 2*250K pot like i.e. the LarMar PPIMV

And yes, keep an eye to the routing of the violet Presence wire and keep it far away of the PPIMV's wiper and their cable as well as far away of the OT's primaries.

Hi Larry, I've got LarMar type installed. I also didn't specify that my 2203 is a clone. I resolved the issue by eliminating everything in equation: I switched OT and choke with my other amp and basically rewired entire amp with new components (including filter caps) - the issue was still present and was random af. Once I moved PPIMV back to the backplate the issue stopped, but shortly after it continued to do the noises. I've got 2 quadros of JJ EL34s on which I always tested my amp and recently I borrowed EHs from my friend and it turns out my JJs were in the end of their lifespan. To get JJs to 34mA of resting current I had to set bias to about -38V, when I put in EHs I had to dime bias pot to -45V, and even with that the weakest tube had like 38mA) - I played the amp for a good hour on EHs and there were no issues whatsoever. Turns out that entire thing with moving PPIMV to frontplate and amp starting to crackle/oscillate was a coincidence.

[ESR]

Hi Larry, I've got LarMar type installed. I also didn't specify that my 2203 is a clone. I resolved the issue by eliminating everything in equation: I switched OT and choke with my other amp and basically rewired entire amp with new components (including filter caps) - the issue was still present and was random af. Once I moved PPIMV back to the backplate the issue stopped, but shortly after it continued to do the noises. I've got 2 quadros of JJ EL34s on which I always tested my amp and recently I borrowed EHs from my friend and it turns out my JJs were in the end of their lifespan. To get JJs to 34mA of resting current I had to set bias to about -38V, when I put in EHs I had to dime bias pot to -45V, and even with that the weakest tube had like 38mA) - I played the amp for a good hour on EHs and there were no issues whatsoever. Turns out that entire thing with moving PPIMV to frontplate and amp starting to crackle/oscillate was a coincidence.

djseban--

I'm finally building myself a 2204 (JCM800 layout). I've planned to put a PPIMV on it since back before I bought all my parts. (I've installed the LarMar PPIMV on my Super Lead as well as my 1987. Love it.) I like the PPIMV on my plexi's... Very excited to utilize it on the 2204.

Wanted to ask you--did you do the stock LarMar PPIMV values when you put it on your 2203? (dual gang 250k log pot, 2.2M resistors), with the 220k resistors removed...?

Also, to you or to anyone else who can answer confidently--the 5.1k grid resistors on pin 5 of each power tube should stay in place, correct?

Thanks!
-ESR

[novosibir]

Also, to you or to anyone else who can answer confidently--the 5.1k grid resistors on pin 5 of each power tube should stay in place, correct?

They are 5.6K and yes they should stay as an oscillation protection

[tjohn1968]

I’m installing a Lamar MV in a new 100w build. I am also going to install a Zero Loss Loop. My chassis two sets of dual speaker jacks on the back panel. I was going to use the second set of speaker jack holes for the Zero Loss Loop since it fits in the already drilled holes. I have come up with two options for the location of the MV pot. In one of the other speaker jack holes or drilling a new hole where the voltage selector switch of I had one would go.

I would rather keep my two speaker jacks by not sure if putting the pot where the voltage selector would be is a good idea. Would it be OK to install the pot there?

Thanks!

[novosibir]

I would rather keep my two speaker jacks by not sure if putting the pot where the voltage selector would be is a good idea. Would it be OK to install the pot there?

Twist the secondary leads to the output selector switch and keep a respectful distance of at least one inch between them and the PPIMV leads, which also have to be twisted or shielded.

[tjohn1968]

I would rather keep my two speaker jacks by not sure if putting the pot where the voltage selector would be is a good idea. Would it be OK to install the pot there?

Twist the secondary leads to the output selector switch and keep a respectful distance of at least one inch between them and the PPIMV leads, which also have to be twisted or shielded.

Twist the secondary leads to the output selector switch and keep a respectful distance of at least one inch between them and the PPIMV leads, which also have to be twisted or shielded.
[/quote

Dang it I have already installed my output selector switch and don’t have the slack in my my wires to really put any good twist in them. I suppose this is always a good thing to do. This is only my second build and haven’t twisted them it doesn’t say anything about it in the Metro build instructions.

Anyway, is it too risky to put the MV pot in the area where the voltage selector would be then? If that’s the case then I will just move it back to a speaker output hole and learn something for my next build.

Thanks Larry!

[CoffeeTones]

I find it helps to include the PPIMV bias wire within the twisting of the PPIMV secondary leads (all three twisted together). Unless you use a multi conductor, shielded wire instead of separate PPIMV leads. You could shield the OT secondaries by wrapping them with an insulated ground wire, with only one end attached to ground, along with the OT secondary ground, or just extend the OT secondary ground wire and wrap it along the length of the remaining, connected OT secondaries. The grounded wrap wire you make the shield out of, should be closely and snuggly coiled around the wires you are shielding.

[novosibir]

Unless you use a multi conductor, shielded wire instead of separate PPIMV leads.

If you use shielded wires, then don't 'ground' the shield, but use it to run the negative bias voltage from the board to the PPIMV pot

[uiovbged332]

Air Force 1
Jordan 13s
Nike Running Shoes For Men
Nike Outlet Online
Jordans 15
Nike Air Force
NHL Jerseys
Nike Epic React
Nike Shoes Canada
Jordan Shoes
Nike Blazers
Jordan 29
Nike Jordan 1 Mid
Jordan 2
Pandora
Adidas Shoes
Nike Air Max 270
Jordan 25
Wholesale Adidas
Air Max 720
Jordan 33
Nike Zoom Pegasus
Adidas Yeezy
Nike Wholesale
Wholesale Nike Shoes
Nike Canada
Wholesale Jordans China
Wholesale Clothing
Jordan Retro
Nike Air Max Men
Pandora Bracelet Charms
Jordans 18
Toddler Jordans
Jordan 23
Nike Shoes Outlet Store Online Shopping
Pandora Jewelry Charms
Nike Outlet Store Online Shopping
Jordans 27
Jordan 33 shoes
Wholesale Nike Shoes China
Jordan 24
Pandora
Nike Shoes
Nike Outlet Store Online Shopping
Nike Huarache Women
Wholesale Adidas
Jordan 6s
Nike Shox Mens
Air Jordan 5 What The
Michael Jordan Shoes
Nike Outlet Store
Jordans 21
Nike Air Force 1 High
Nike Air Force 1
Jordan 35
Jordan 11
Kids Jordans
Fjallraven
Wholesale Jordans From China Factory
Nikes Shoes
Nike Women's Shoes
Louboutin Shoes
Nike Shoes For Women
Jordan 11 Concord
Cheap Jordans
Nikes
Pandora Jewelry
Jordans 22
Nike Canada
Air Max
Jordan 11 Retro
Nike Shoes
New Jordan
Pandora Jewelry
Adidas Shoes For Men
Nike Foamposite
Off White x Nike
Pandora Jewelry 70% off Clearance
Wholesale Air Jordans
Nike Shoes Men
Jordans 12
Jordan 30
Adidas Store
Air Max
Jordan AJ 1
Cheap Jordan Shoes For Women
Nike Air Force 1
Jordan 33
Nike Blazer
Wholesale Adidas
Nike 270
Pandora CZ Charms
Retro 12
Jordan 34
NMD
Jordan 13
Raptors Jersey
Wholesale Jerseys
NHL Store
Jordan 11 Low
Jordans 17
Jordans 31
Nike Outlet Store
Adidas Yeezy Boost 350 V2
Cheap Jordans
Jordan Dior
Cheap Nikes
Nike
Air Jordan 16
Nike Wholesale
Pandora Rings
Red Bottoms
Lebron Shoes
Jordan 12
Jordan 4 Retro
Nike Air Jordan Shoes
Pandora Ring
Nikes Shoes
Cheap Jerseys
Nike SB Dunk
Air Jordan 14
MLB Jerseys
Nike Shoes
Cheap Jordans Wholesale
Nike Sneakers
Nike Shoes Black Friday Deals
Nike Zoom Pegasus
Nike Slides
Air Force 1s
Air Jordan 32
Jordan 28
Nike Sneakers
Nike Free rn
Christian Louboutin
Nike Outlet Online
Huarache
Huarache
Nike Wholesale
Jordan 1
Cheap Nike Shoes
Nike Store
Jordan 19
Nike Free
Nike Foamposite
Nike Running Shoes For Men
NFL Gear
Adidas Factory Outlet
Nike Wholesale Suppliers
Jordan 26
Jordan 20
MLB Jerseys
Jordan Retro
Men Nike Shoes
Nike Clearance
Yeezy Boost 350 V2