parasound 3500 verses parasond jc1

Talked it over with Curl and might as well give the information to make the 3500 a better amp for those still using the old war horse....Replace Q-5 which is an IR part with Harris IRF9610. This along with the AC polarity and feedback resistor we have published before will get you down the road pretty well......These can be replaced without even taking off anything but the top as they are close to the top of the boards......To get any more serious with the 3500 includes replacing the emitter resistors and then the rectifiers, both of which are a real job involving almost complete disassembly.......It was a five day job to rebuild the 3500s into the CTC BBQ and much of the metalwork was redone as well as used circuit breakers in lieu of the 6a switches and surgisters for turn-on........

Best,

Bob Crump
CTC Builders

Bob Crump
CTC Builders

Bob - I get what you mean now.

My customers and I both find the "brightness" of the 3500 to be exceptional clarity once it is modded. I had to go back to the JC-1's after CES and improve the HF extension and dynamics to match that of the 3500. I actually used the modded 3500 most of the time at CES/THE Show as opposed to the JC-1's because of this pristine, clear high-end. It's hard to believe that this is distortion....

Steve, sorry but suggest you measure it........We did and found a ton of 2nd.........Glad you and your customers like the brightness this imparts on the sound as it saves $5 or so in parts for the revisions along with maybe ten minutes of work........Really glad you fixed the horrible problems in HF extension and dynamics in the JC-1s and suggest that once your amp is out you send it here so that we can criticize it and perhaps offer mods to fix the problems as we see them.............Sorry, but without changing the emitter resistors the 3500 will never be pristine and you will have the same problems we did as you'll run out of heatsink before you get it pristine.......

Bob Crump
CTC Builders

interesting!

Bob - thanks much for the tips. I will definitely try the Harris part on the next one that I mod.

BTW - I decided to replace all of the bias pots with sealed Bournes units in the 3500 and eventually, the JC-1's to avoid creeping bias and future warranty problems. Also made some other changes to minimize warranty issues. I appreciate your "war-stories" on this.