guitar4444
Well-known member
- Joined
- Oct 1, 2009
- Messages
- 105
Not sure if this is the spot to post this but anyway.
I have an UA LA-610. I had distortion problems when running it as the levels are suggested in the manual and with the VU reading below 0db on both input and output. I opened it up and measured the heater voltage at 5volts after reading someone else had a problem with low votage. It turns out the LM1085 regulator is setup to give 4.9volts which is below the generally accepted +/-10% tolerance. Any way I changed one resistor from 2.2k ohms to 2.8k ohms (actually just lifted one leg and put in an extra 590 ohms resistor) and now the voltage is about 5.9 volts, well within spec. Preliminary testing suggests it's gone from almost unusable to great. I'm looking forward to further testing and being able to use it without so much caution.
I'm running the new reissue eletro harmonix Mullard 12ax7's and another black plate 12at7 (can't remember what the brand was) on the output.
cheers Greg
I have an UA LA-610. I had distortion problems when running it as the levels are suggested in the manual and with the VU reading below 0db on both input and output. I opened it up and measured the heater voltage at 5volts after reading someone else had a problem with low votage. It turns out the LM1085 regulator is setup to give 4.9volts which is below the generally accepted +/-10% tolerance. Any way I changed one resistor from 2.2k ohms to 2.8k ohms (actually just lifted one leg and put in an extra 590 ohms resistor) and now the voltage is about 5.9 volts, well within spec. Preliminary testing suggests it's gone from almost unusable to great. I'm looking forward to further testing and being able to use it without so much caution.
I'm running the new reissue eletro harmonix Mullard 12ax7's and another black plate 12at7 (can't remember what the brand was) on the output.
cheers Greg
