Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Ed_Chambley on February 10, 2012, 05:38:48 pm
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Their design replaces the 220 ohm resistors with the pot being 250 ohms and added a 2m2 resistor to both left lugs on pot. I seem to have lost some volume when the master is full on. This layout replaces wire to tube hook-up on pin 5 of v-4 and 5 in my case. Is is a El-34 with 12Ax7 in v1 2 3.
It is wired correctly as I am getting good volume, but it seems like only about 70% of what was there before. Same cab and speakers.
I questioned the 2m2 resistors when putting them on the pot. They are there to protect the tube in a pot wiper failure.
Will reducing these resistors increase output? Anyone else used this type of master? I read where it is the best PPIMV, but I have serious doubts now. Any and all comments are welcome from opinions about MV's and or ideas to get that amp screaming with this type of MV.
Link http://metroamp.com/wiki/index.php/Lar/Mar_PPI-MV (http://metroamp.com/wiki/index.php/Lar/Mar_PPI-MV)
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No,do not change the resistors.You have mis-wired something because if properly implemented,the Lar-Mar master will not reduce output volume.
You are the variable here.It is easy to make a simple mistake.Recheck your work.
The master volume design is not the issue.
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Their design replaces the 220 ohm resistors with the pot being 250 ohms and added a 2m2 resistor to both left lugs on pot.
Maybe this is a typo but if your pot is 250 ohms instead of 250k then you will have little to no volume. You need dual gang 250k pots with 2.2M resistors.
With respect, Tubenit
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Their design replaces the 220 ohm resistors with the pot being 250 ohms and added a 2m2 resistor to both left lugs on pot.
Maybe this is a typo but if your pot is 250 ohms instead of 250k then you will have little to no volume. You need dual gang 250k pots with 2.2M resistors.
With respect, Tubenit
Typo, but thanks.
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No,do not change the resistors.You have mis-wired something because if properly implemented,the Lar-Mar master will not reduce output volume.
You are the variable here.It is easy to make a simple mistake.Recheck your work.
The master volume design is not the issue.
Thanks, I will do, but the volume drop was not right after the install of the master. It was just the last mod I did. I was just checking if it COULD do it. Now I know it cannot, I will recheck the wiring and then begin looking elsewhere.
Thank you.
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I find a lot of the volume loss is due to not being able to turn the bass up very much as it gets very muddy when doing so. Running an eq into the amp I was able to get the volume back and kill some of the bass. I ended up changing the large value caps on v1a from 330 to 25 and added a separate cap as in a plexi to a .01. Added a couple of .0022 like in a 2204 and wow what a difference. Not really a jtm 45 anymore, but I have 35 watts of El 34s and the touch sensitivity is incredible and the tone stack is very useable. I guess it is now a tube rectified Plexieighthundredand45.