Hello,
I am a novice parts changer in the process of restoring a late 1970s Pioneer SX-1250 receiver. I need around 12 transistors that have been gain matched (Hfe, Vbe, anything else I am missing.) I am in California. The transistor Mouser part numbers are 512-KSA992FBU. Please provide price, shipping cost and availability.
Regards,
Dave Lyon
I am a novice parts changer in the process of restoring a late 1970s Pioneer SX-1250 receiver. I need around 12 transistors that have been gain matched (Hfe, Vbe, anything else I am missing.) I am in California. The transistor Mouser part numbers are 512-KSA992FBU. Please provide price, shipping cost and availability.
Regards,
Dave Lyon
Instead of spending loads of cash on stuff you will never be certain of, why not purchase a transistor tester for about ten bucks a batch of say 100 transistors and match them yourself. It will be cost effective and good practise.
Assuming you get the matched transistors for your SX-1250. What equipment would you use to adjust the output DC bias for minimum distortion?
If you are going into the trouble of matching the power amp differential input pair, I'm assuming you are shooting for the lowest distortion possible. Getting almost zero DC offset at the output and setting the DC bias to the factory's recommended "one setting for all" is not enough.
You have to consider how you are going to validate the improvement in distortion once you swapped the parts. Minimum equipment to do this is a scope and signal generator, preferred setup is a low distortion audio analyzer and a scope.
I have designed amplifiers for years and never bothered matching transistors.
I use source/emitter resistors to balance out the current.
For LTP I use a trimmer in the current mirror to counter any slight offset.
I use source/emitter resistors to balance out the current.
For LTP I use a trimmer in the current mirror to counter any slight offset.
What is wrong with the existing transistors? "Novice parts changers" often change things which don't need changing as they wrongly believe that this is the essence of 'restoration'.
Be aware that Pioneer never did any gain matching. Your objective is unclear. Only replace stuff that's broken lest you change the behavior the designers intended. Unless you want to mod and customize, of course. Then that becomes your objective.
Its been touted numerous times on another forum to gain match on the 2 amplifiers to gain match the 2 992's on each amp board within 1 or 2%, and others say it's not required, I redid my boards and had 150 992's to choose from, so i did it because I could, I never heard any sonic difference anyway, but I guess it's easy to get hooked up on all the hype that goes into other forums, that when someone speaks it's like the second coming of the messiah. Like some one said in an earlier post, you need alot of equipment to get a receiver perfect anyway, I dont have it and set my offset and bias by the spec, It isn't perfect but it sure sounds pretty nice for a generic tune up
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