parasound 3500 verses parasond jc1

Steve, we are talking about different things.......The IR devices that need to be repaced with Harris are not rectifiers, they are Mosfets used in the input section and this is the cause of the huge amount of 2nd harmonic distortion in the 3500 over the JC-1.......This amount of 2nd harmonic comes across as brightness in the upper midrange which can be tamed with two parts and about ten minutes of work.........The Harris diodes used as rectifiers in all three bridges in the 3500 will allow for improved bass tightnesss as well as a much better stage......

Bob Crump
CTC Builders

The 3500 is a stereo JC-1 is about the only difference worth noting in the electronic design. The 3500 has a ton more 2nd harmonic due to the International Rectifier devices in the driver circuit in lieu of the better mannered Harris devices in the JC-1 so the JC-1 is a much smoother amplifier without the glitz and glimmer in the 3500's sound. You are never going to get the 3500 as smooth as the JC-1s due to the devices as well as the layout.

Bob Crump
CTC Builders

I'll get with John later in the day and post the number as easier than tearing the top off my 3500 :-) Funny thing is the Harris is the second source for the Mosfets as they are IR/Fairchild parts, but they don't exhibit the weird behavior and brightness of the IR/Fairchild parts......

Bob Crump
CTC Builders

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

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