Rob Flindall (flinly)
I recently replaced IC-1, IC-3 and IC-4 on my 112RD-100 (2100-RD-GD2A circuit with 6L6 output tubes). The stock ICs were Texas Instruments TL072. I replaced them with TLE2072 (also T-I). I did this hoping to reduce the noise and hiss when the Reverb is engaged.
At the same time I had the Amp Technician clean the Reverb Pot and check the bais on the output tubes.
Hiss has improved, and the Reverb is more pronounced. Otherwise there was no discernable change. So I can't really determine if the IC change out made a difference. However it didn't bugger it up, and the overall outcome is improved at least on the Reverb.
On a side note, T-I sent me the ICs for free. They have a "Free Sample" program on there website.
If any one has suggestions on better upgrades either for the TL072 of the LM 1458, I would be interetsed in your experience.
I would still like to get a better response out of the "Distortion" channel. I am not 100% confident the Amp Tech biased the thing correctly. Bob G at Cosmos here in Richmond Hill, Ontario supervised the work (thanks Bob!) but the distortion still seems to clip at high gain. So it may go back in the future.
|Mike Kaus (mm210)|
If I remember correctly, the distortion on those amps sucked anyway. I have always found pedals the way to go on MM's. Their "natural" distortion has always been harsh.
|Rob Flindall (flinly)|
Yah, I am just learning guitar, so mostly playing clean...but for low cost, I want to switch on some distortion for things like ZZ Top "Jesus left Chicago" type of sound. Plus I like toying around with the electronics of Amp...hence my interest in the 112RD.
|Lars Verholt (lmv)|
The distortion effect in this model of MM is accomplished by clipping diodes. The op-amps (ICs) should never overload during normal operation of the amp. As long as the op-amps are working properly they are not supposed to add any coloration to the sound.
Some have replaced the diodes in the clipping circuit with other types, even LED's, to produce different sounds.
If the amp sounds clean at low/moderate levels on the clean channel, the output tubes are biased correctly. If you get a buzz 'behind' the clean sound at low levels, the bias could use an adjustment. Likewise if the output tubes are red-plating, the bias should be looked at.
If you ever need help (relatively) locally, feel free to drop me a line. I'm in Peterborough.
|Rob Flindall (flinly)|
No issues in clean, low volume, so bias probably is good ( it was checked).
Thanks for the offer, I am in Peterborough frequently to visit family, so I may take you up.
Tue, 03/25/2014 - 09:54#1