Post-Phase Inverter Master Volume (PPIV MV) Installation in a Marshall amp
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- เผยแพร่เมื่อ 6 ก.ย. 2024
- How to install a post-phase inverter master volume in a Marshall amp. This is a JCM800 Master Model 50W Mk II Lead amp that already has a pre-phase inverter master, but adding a MV post-PI allows more gain and fuller tone at much lower volumes. The procedure is the same for any similar amplifier, as the PPIV MV is installed between the output of the phase inverter and the power tube grids.
I offer this as a DIY kit on the GrangerAmp website, for those who want to add it to their amps, and who have enough electronics experience to do so safely. IMPORTANT DISCLAIMER! Voltages inside tube amps can severely injure of even kill. Do not attempt this or any other modifications if you are not sure what you are doing, or if you do not understand how to properly discharge any high voltages present inside the amp.
This added MV would get rid of that JCM800 standard MV issue of going from off, to extremely loud ,between zero and 1! Way better for home use, I bet!?
I really...really like your amps, your workmanship and technical expertise, which is displayed in your amps and finished work. I would like to see more of these type of videos. Great idea of using shielded cabling to eliminate noise. Nice shiny solder concave fillets. Always keep that board free of flux. Like my NASA workmanship instructor says, clean clean clean...and when you are done clean again. LOL.
Thank you David! I'm planning on posting more DIY and repair type videos in the future.
@@Grangeramp I think you could work up a good following if you did. You do great work.
I just bought a '90 2204, and will be using this video as my bible to install a LarMar! Also, it looks to be easier to do the wiring under the board, since it would be tough jamming the red, black, and shield into the small holes from the top. Also, those are 1 watt 2.2 meg resistors, the half watt ones I have are way smaller.
Thank you Sir for this great tutorial ,...I'm a house builder but wish I was a tech !.......................Subscribed !
You're welcome Lou, I appreciate your feedback and thank you for subscribing!
Great work ! nice
Thank you!
I e been thinking about a master volume mod for my Marshall class 5….or a variable power control ( I don’t know if it’s the same as a master volume) kit.
Excellent video. Do you know if this mod can be done on an SV20H amp?
Yes, most likely if it's the same 1987/1959 preamp/tone stack/LTPI circuit they use in most of their "plexi" amps.
Can an amp like my carr slant 6v have a post phase inverter master volume installed without issues or is it only for marshall style amps.
Is it safe on catode biased power tubes?
My JCM800 has flying leads to the pots, I thought board mounted pots didn’t start until the JCM900, is this a later 800?
Yes, horizontal (side-by-side) inputs. Many of the later 800s had board mounted pots.
@@CurtGranger - thanks. That was my only gripe with the 900’s, every one of them I owned I had to repair.
I would also like to install a master volume for jtm45 I am a little worried that the sound will not change. What do you think? Thanks
I've added to many JTM45, and it makes the amp more usable.
I think I like the regular Marshall pre-phase inverter master volume better.
I personally prefer to have both. Cleaner tones with the pre, but it's lossy (low end loss) at anything below 4. Then it gets loud quick. the PPIV gets fuzzy at lower settings. A blend of both achieves a nice balance at any volume ( to a certain degree - there's no substitution for cranking it loud).
The "Type 4" Master Volume as Ken Fischer called it... it comes off the Treble control in the tone-stack. This cathode-follower Master is better for more metal styles...