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Can a post phase inverter master Vol be installed in other amps

Messages
1,950
Hi just curious if a post phase inverter master volume can be installed in non marshall style amps and more fendery style stuff like my carr slant 6v. Seems to work excellent in the new Dr Z MAZ 18MKII so would it work with these other amps???.
 

BlueRiff

Member
Messages
6,926
Hi just curious if a post phase inverter master volume can be installed in non marshall style amps and more fendery style stuff like my carr slant 6v. Seems to work excellent in the new Dr Z MAZ 18MKII so would it work with these other amps???.
Yes!! I have one on a Blackface Fender Deluxe Reverb boosted to 40 watts along with an added mid control. Cranking the mids and preamp volume yields a beautiful Stones raunch similar to live Midnight Rambler recording. Definitely not a Marshall sound.
 
Messages
1,950
Ft
Yes!! I have one on a Blackface Fender Deluxe Reverb boosted to 40 watts along with an added mid control. Cranking the mids and preamp volume yields a beautiful Stones raunch similar to live Midnight Rambler recording. Definitely not a Marshall sound.
Ok I just heard in some forums lol that PPIMV only sounded good in marshall style amps but I'm starting to hear different things. Some people say it only works really well with cathode bias amps, not too sure how much weight that theory holds.
 

BlueRiff

Member
Messages
6,926
Ft
Ok I just heard in some forums lol that PPIMV only sounded good in marshall style amps but I'm starting to hear different things. Some people say it only works really well with cathode bias amps, not too sure how much weight that theory holds.
Well I’m only a single data point on this, but I heartily disagree with those other forums!! It is a huge fat overdrive sound but not designed for Marshall palm muted tight chugging - more riffing. It’s a blast!
 
Messages
1,950
Well I’m only a single data point on this, but I heartily disagree with those other forums!! It is a huge fat overdrive sound but not designed for Marshall palm muted tight chugging - more riffing. It’s a blast!
What are you for and against sorry. Not clear which you dig. Thanks.
 

dazco

Member
Messages
15,473
When i was building tube amps i tried this a number of times and i never understood why they are lauded by some. What they do is allow the PI to distort which sounds ratty and horrible IMO. A pre PI master worked best no matter what circuit i tried them in. I'm still puzzled why people seek that feature out. I researched the hell out of it and tried everything imaginable but could never get anything close to a good sound out of an amp with a post PI master. Maybe with very clean preamps they might sound good, i dunno. But i built amps with 3 stage cascaded preamps that were NOT high gain but at least a good healthy classic rock degree of gain.
 

critter74

Silver Supporting Member
Messages
5,269
I'm not sure what type of Master Allen Amps uses but my Old Flame (BF Super Reverb clone with extra awesomeness) has a master on it that works fantastic.
 

communarchy

Silver Supporting Member
Messages
789
Yes., it can work. Some circuits work better than others. The reason why a PPIMV works well in Dr. Z Amps is because most of them have no negative feedback or very little. A cathode biased power section also helps smooth things out as well. Amps with more NFB will not sound as good lower on the dial, as a PPIMV will lower the amount of NFB being injected in the circuit as it's lowered, which in some circuits can result in a rawer tone at lower volumes which is what some people call "ratty" or "fuzzy." Marshall amps vary in the amount of NFB that is present in the circuit and are also fixed biased, which is why many people think they sound good in some band bad in others. Where and how much NFB is injected back into the circuit on Marshall's varied wildly through the years. That said, there are a variety of ways to implement a PPIMV circuit and the right variation and component value choices will depend on the circuit to get the best results. There is some taste testing involved.

When i was building tube amps i tried this a number of times and i never understood why they are lauded by some. What they do is allow the PI to distort which sounds ratty and horrible IMO. A pre PI master worked best no matter what circuit i tried them in. I'm still puzzled why people seek that feature out. I researched the hell out of it and tried everything imaginable but could never get anything close to a good sound out of an amp with a post PI master. Maybe with very clean preamps they might sound good, i dunno. But i built amps with 3 stage cascaded preamps that were NOT high gain but at least a good healthy classic rock degree of gain.

Highly dependent on the type of amp you are working with. Cascaded preamp configurations can work, but it needs to be married with the right power section design. It may have been that they type of amps you were building just didn't lend themselves to the PPIMV circuit, as I mentioned, some factors need to be taken into account before implementing them.
 
Messages
1,950
When i was building tube amps i tried this a number of times and i never understood why they are lauded by some. What they do is allow the PI to distort which sounds ratty and horrible IMO. A pre PI master worked best no matter what circuit i tried them in. I'm still puzzled why people seek that feature out. I researched the hell out of it and tried everything imaginable but could never get anything close to a good sound out of an amp with a post PI master. Maybe with very clean preamps they might sound good, i dunno. But i built amps with 3 stage cascaded preamps that were NOT high gain but at least a good healthy classic rock degree of gain.
I have to say I noticed a good difference with my MAZ 18 MKII that has one. Dr z says it only really works in cathode bias amps, is there some science to this ?
 
Messages
1,950
Yes., it can work. Some circuits work better than others. The reason why a PPIMV works well in Dr. Z Amps is because most of them have no negative feedback or very little. A cathode biased power section also helps smooth things out as well. Amps with more NFB will not sound as good lower on the dial, as a PPIMV will lower the amount of NFB being injected in the circuit as it's lowered, which in some circuits can result in a rawer tone at lower volumes which is what some people call "ratty" or "fuzzy." Marshall amps vary in the amount of NFB that is present in the circuit and are also fixed biased, which is why many people think they sound good in some band bad in others. Where and how much NFB is injected back into the circuit on Marshall's varied wildly through the years. That said, there are a variety of ways to implement a PPIMV circuit and the right variation and component value choices will depend on the circuit to get the best results. There is some taste testing involved.




Highly dependent on the type of amp you are working with. Cascaded preamp configurations can work, but it needs to be married with the right power section design. It may have been that they type of amps you were building just didn't lend themselves to the PPIMV circuit, as I mentioned, some factors need to be taken into account before implementing them.
I keep hearing consistently that these master volumes work great in marshall style 800 or similar type amps.
 

gldtp99

Member
Messages
4,078
I keep hearing consistently that these master volumes work great in marshall style 800 or similar type amps.
You could always install a PPIMV and see how it sounds to you

Don't put too much stock in what it might say in an internet post ---- often the same mod will be Great, OK, and/or Terrible depending on who wrote the post

Trust your own ears

Also, there are several different kinds of PPIMV's

I've included Lar/Mar PPIMV's in BF Fender type builds many, many times

I find them to be a very useful addition, in most cases
 

LaXu

Member
Messages
9,167
I have one in my Victory VC35 which is a mix of fixed and cathode bias in the full 35W mode. Not sure how that mix works as I haven't seen it in any other amp. The idea afaik is to avoid going through powertubes quickly like some Vox AC30s can. In the 12W low power mode it's fully cathode biased. The difference is mainly in punch and feel between the two modes at equal volume.

Soundwise it's somewhere between a Vox AC30 and a Matchless DC30 to my ears, with a bit more punch in the midrange.

But getting back to the PPIMV, it works really well in this amp. Gradual all the way and not a huge difference between the cranked sound vs turning the PPIMV down. Adding a compressor and a bit more preamp gain gets surprisingly close to the cranked sound.

Maybe having the Vox style high cut control helps? It's called the Tone knob in this amp, it's just a reverse wired high cut so it's more intuitive to use with the other controls.

Local builder Bluetone puts a PPIMV in most of the amps they make (mostly Fender and Marshall based ones) and every one I've tried has worked well in that regard.
 
Messages
5,200
When i was building tube amps i tried this a number of times and i never understood why they are lauded by some. What they do is allow the PI to distort which sounds ratty and horrible IMO. A pre PI master worked best no matter what circuit i tried them in. I'm still puzzled why people seek that feature out. I researched the hell out of it and tried everything imaginable but could never get anything close to a good sound out of an amp with a post PI master. Maybe with very clean preamps they might sound good, i dunno. But i built amps with 3 stage cascaded preamps that were NOT high gain but at least a good healthy classic rock degree of gain.
Have you ever played a modern Vox, or an Orange? These are 2 examples of PPIMV amps.

It’s very application specific. Sometimes it works, sometimes it doesn’t.
 




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