Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Tone Junkie on February 24, 2014, 06:42:12 pm
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Just need to know I have my ppimv conected properly with a cathode biased amp . tried to find tyhe schematics i saw before couldnt.
Thanks Bill
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If you look in ARCHIVES, there is ALOT of information there including schematic of various master volumes including the PPIMV LarMar:
Look at Reply #7
http://www.el34world.com/Forum/index.php?topic=3496.0 (http://www.el34world.com/Forum/index.php?topic=3496.0)
With respect, Tubenit
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Thanks tubnit but non of those showed a cathode biased amp with a lar-mar ppimv didnt one of you. didnt one of you d,mars or TOS schematics have one. I will go look
Thanks Bill
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OK, I see what you're talking about. You just ground the dual gang pot instead of sending it to bias.
With respect, Tubenit
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May be I'm wrong
but I think that in a cathode bias circuit the 2.2M resistor connected to the wiper of the pots aren't indispensable and you can omit it
K
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Yes thats the one i finally found it in a large pile of papers . I copy all that stuff . Much of it hangs in my computer room in poster sized schematics , im a little odd (LOL).
Thanks Bill
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I installed a LarMar in my cathode bias EL34, but it has a 18 watt marshall preamp. Ended up replacing it with the common marshall mv. I really like the Larmar in most everything, but here I did prefer the pre master. As a matter of fact it is the only master volume amp I have that is not like the Larmar.
Just thought I would mention it to you, but you may prefer the Larmar. Mine has a Chieftan power section with much lower voltage and it became very difficult to get anything close to clean.
Not trying to tell you what to do as we all like different things.
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Ed I will keep that in mind.
I have not got her up and running yet ,still checking voltages and double checking everything just wanted to make sure it was wired rite before I stick the tubes in.
Everything seems good.
Thanks Bill
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I installed a LarMar in my cathode bias EL34, but it has a 18 watt marshall preamp. Ended up replacing it with the common marshall mv. I really like the Larmar in most everything, but here I did prefer the pre master. As a matter of fact it is the only master volume amp I have that is not like the Larmar.
The 18 watt preamp does not have much gain. Even when dimed it will not drive the phase inverter into heavy overdrive. Most of the drive in the 18 watt (also in the Spitfire) comes from overdriving the output tubes which you cannot do with a PPIMV turned down. The LarMar works really well in preamps with two gain stages where there is enough gain to overdrive the phase inverter.
Cheers Stephan
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No worries there my own brand of hot rod marshall 3 gain stages +CF
Bill
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If you post a schematic of your amp we could tell you for sure if it at least works on paper.
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No worries there my own brand of hot rod marshall 3 gain stages +CF
In that case a pre PI master volume should work well, too. But some mods - especially Mod 5 - use a PPIMV.
Cheers Stephan
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Sorry I didnt get back right away Ive been battling sleep issues, :help:.
Steve its just a basic Marshall master volume type amp with with cathode biased el34,s I never tried it that way before.
I just have 2.7K and .82 cathode caps for the first 2 gain stages instead of the usual arrangement . Im trying out valve wizards 2 different bootstrapped cathode followers before the tone stack, to see if I like them.
I just didn't want to plug power tubes in and wreck a set. So I asked about PPIMV with cathode biasing.
I have that cheap amp set up with cap built into the guitar cable that Doug showed us in his tools section. so I can just listen on down the line as I go.
Im still playing around with a few things. So I havn't cranked here up yet.
darkbluemurder I like the master volume set up with a PPIMV also.
Thanks Bill