Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Kitarist on February 03, 2017, 08:26:16 am
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So i tried 2 type of master volume mods. PRE and POST but both dont work properly. (1 MEG LOG POT)
I did everything as it shows on the schematics and it still doesnt work properly. https://robrobinette.com/5e3_Modifications.htm#Add_Master_Volume
What is happening that the volume mod is totally unusable when i just shift it a bit the amp already goes very loud and theres not much to work with. Is that normal? Both do the same thing.
I even checked again the operating voltages of the amplifier and everything works fine. Both mods are so simple really not sure why.. I even mesured and tested the pot.
So not sure what it would be causing this? Anyone got any ideas? Could be the output tubes? im using JJ 6V6 S tubes.
Thanks!!!
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I've done Bruce Collins Mission Amps master volume mod it uses a dual 1MA pot replacing the current first 1MA volume pot and coupling cap to .1uf and other changes.
Not sure I should post the layout.
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Not sure I should post the layout.
Why not?
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I'm no stranger to amplifier forums and once another person's layout is posted a shit storm arrives right after.
Why I mentioned the mod is so the OP can research and find the mod himself like I did without the problems associated with posting layouts.
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I think it's already been posted a few times here?
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Yes it has been posted here a few times. I remember posting it a few times myself. Don't remember a storm after, but you never know.
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Let's see, it is posted again.
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Kitarist, are you sure the pot is a log or audio and not linear or reverse audio? Since both master volume configurations didn't work I'm thinking it's the pot.
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Here is the layout.
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I put a pre PI master volume on my mutated Princeton Reverb (similar phase inverter). Works great.
--Craig
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I checked everything even changed different pot still same prob really not sure what could it be.
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I could not get the Robinette version to work without keeping the original 1 meg grid leak resistor and adding a 1 meg pot and another cap (.047). See my schematic for details if you want to try again.
--Craig
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Ok i'll try that. Really not sure why both volume mods in robs website dont work :|
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I apologize, but I am not clear on what you have tried? Have you tried this PPIMV? I've used it on an amp very similar to a 5E3, and it worked excellent to my ears.
With respect, Tubenit
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Here is the layout.
MFowler,
Is this a pull switch pot or does the second volume become the main volume? I have not seen this layout, but it look as if it incorporates what I have heard refereed to as a trick switch? Have you tried this? It looks interesting. If you have done this, did you keep the 12Ay7 or change to 12Ax7?
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I apologize, but I am not clear on what you have tried? Have you tried this PPIMV? I've used it on an amp very similar to a 5E3, and it worked excellent to my ears.
With respect, Tubenit
This master volume I have found to be best for most amps and I have used it in a 5E3 incorporating the 6G3 tone stack. The amp changes a LOT and you get a slower ramp up in volume. You do lose the interaction of volume controls and the early onset of distortion which is what a lot of folks like about the Tweed Deluxe. It doesn't make it a Brown Deluxe, but it gets sort of in-between. The Ampeg mod ( Paul C mod for the PI) and a Blackface tone stack will make this amp sound a lot like a Carr Rambler. :thumbsup: If you want to make it into one you will need to Beef up the PT to run 5881's and add a Fender verb circuit. I simply used the 1 tube verb. Keep the voltages low since the rambler states 28 watts.
Now it is back mainly stock with a split cathode on V1 to get a good Humbucker tone simply because I decided to build a Carr knockoff.
Fun circuit to play with for sure.
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MFowler,
Is this a pull switch pot or does the second volume become the main volume? I have not seen this layout, but it look as if it incorporates what I have heard refereed to as a trick switch? Have you tried this? It looks interesting. If you have done this, did you keep the 12Ay7 or change to 12Ax7?
This is a dual 1MA pot no push/pull. I have build an amp using this mod.
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MFowler,
Is this a pull switch pot or does the second volume become the main volume? I have not seen this layout, but it look as if it incorporates what I have heard refereed to as a trick switch? Have you tried this? It looks interesting. If you have done this, did you keep the 12Ay7 or change to 12Ax7?
This is a dual 1MA pot no push/pull. I have build an amp using this mod.
Thanks for the photos. I got it now! Gonna give it a try, looks interesting and the only way to know is build it. I see you did use a 12Ax7.
Thanks again!
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This is my recommended master volume for the 5E3 Deluxe:
(https://robrobinette.com/images/Guitar/5E3P_Build/5e3_Pre_PI_Master_Volume_Schematic.png)
It simply replaces the V2A 1M grid leak resistor with a 1MA pot. At max volume the circuit is unchanged.
(https://robrobinette.com/images/Guitar/5E3P_Build/5e3_Pre_PI_Master_Volume_Mod_small.png)
You have to clip or remove the original 1M grid leak resistor.