Always Wanted to do this...
- Thread starter EchoWars
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Hey EW -- Did that KR-9050 CD-ROM Service Manual ever arrive?
rockin1150
Super Member
that's awsome! i have a question..
How did you do that? I wouldn't have the foggiest clue where to find teh signal in/out to connect those jacks to inside.. any advice?
How did you do that? I wouldn't have the foggiest clue where to find teh signal in/out to connect those jacks to inside.. any advice?
Yes it did!! I didn't thank you?? Oops...my bad. Been pretty swamped, but I did take a look at the topology. I like it... Nice 2SC2607/2SA1116 output stage. Power supply uses +/- 75V rails, and four 10,000µf 90V caps (the KR-9600 also uses four 10,000µf caps).
If this one blows up, no unobtanium parts. Always good...
School?
Honestly, I've had a lot of practice with this. Every amp is different, and some require buffering since elsewise they would have no drive capability.
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waylyn5945
Active Member
Nice job EW. I'd like to do that with my hk-430. Make it a hell of a lot more versatile.
Brass. Copper would corrode too badly and is too soft to hold a shape. The brass looks cool and will not corrode (but will tarnish over time...a bit of Brasso will make 'em look like new again).
It's turning into a bit more of a project than I thought...the preamp has very good drive capability (500 ohms) until the tone controls are switched in, then it goes to hell (3.5K). That might be good enough for a lot of amps, but in general kinda sucks. I'm buffering the output with a Burr-Brown OPA2604. The 7100 also does not have sutable split supplies to power the opamp, so I also have to fashion a +/-18V zener regulator to power the opamp.
It'll be fine once done, but so far has taken most of the day...
Edit: The copper would oxidize, but it is not a huge problem (so I am informed), as copper oxide conducts just fine. I still use brass because 8ga solid-core copper is a pain to find.
It's turning into a bit more of a project than I thought...the preamp has very good drive capability (500 ohms) until the tone controls are switched in, then it goes to hell (3.5K). That might be good enough for a lot of amps, but in general kinda sucks. I'm buffering the output with a Burr-Brown OPA2604. The 7100 also does not have sutable split supplies to power the opamp, so I also have to fashion a +/-18V zener regulator to power the opamp.
It'll be fine once done, but so far has taken most of the day...
Edit: The copper would oxidize, but it is not a huge problem (so I am informed), as copper oxide conducts just fine. I still use brass because 8ga solid-core copper is a pain to find.
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OK...mod is done. Here's the OPA2604 opamp and the +/-18V regulator, made as small as possible. The 7100, used as a preamp, can now drive any amp you can dig up. The opamp is DC coupled to the pre-out jacks, so the 'on-last, off-first' rule for separate amps/preamps is in effect.
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wow...
At first glance I wasn't sure exactly what I was looking at... then gave my head a shake and realized that you have effectively attached that tiny piece of perforated circuit board onto an exposed and unused tab on the original circuit board.
Nice job.... looks very unobtrusive!
At first glance I wasn't sure exactly what I was looking at... then gave my head a shake and realized that you have effectively attached that tiny piece of perforated circuit board onto an exposed and unused tab on the original circuit board.
Nice job.... looks very unobtrusive!
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Yep...but I learned a while back that the tape can and does let go sometimes, so there is also a dab of epoxy on both sides of the board to help hold it in place.glen65 said:
Thank you! I don't like kludges, and that whole section of the control PCB has no circuitry on it. No reason not to put it there.hpsenicka said:
The wires running to the rear jacks is RG-174 mini-coax...grounded at the rear panel only. The wires running to the opamp assembly are of course not shielded, but due to the placement being close shielded wire is not needed.
The amp measures about 80WPC at 0.5% THD, and at the rated 60WPC, measures about 0.006% THD. Not bad...
EW
Fair enough... I don't want to encourage you to take any risks... especially not with my gear
.
If you still have the 7100 on your bench hooked up to your test gear, there is one other thing I was wondering about...
I'm assuming that within the normal power output range the measured THD is fairly flat (in this case probably around .01% or less?), then starts to rise somewhat as power output exceeds the normal limits the amp was designed for.
Can you measure, or even approximate where the slope of this curve starts to climb significantly.. or alternately, perhaps defining this as the output level where THD exceeds the original spec of .02%?
Fair enough... I don't want to encourage you to take any risks... especially not with my gear
.If you still have the 7100 on your bench hooked up to your test gear, there is one other thing I was wondering about...
I'm assuming that within the normal power output range the measured THD is fairly flat (in this case probably around .01% or less?), then starts to rise somewhat as power output exceeds the normal limits the amp was designed for.
Can you measure, or even approximate where the slope of this curve starts to climb significantly.. or alternately, perhaps defining this as the output level where THD exceeds the original spec of .02%?
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Is it just me or do we all love EWs threads and dirty little deeds?
You amaze me with the Chit you come up with and as a craftsmen I know the time it takes to get things like this right.
I suspect I won't be the first to call you a name-Perfectionist!!!!!!!!!
Well done EW and I would be proud to own one of your creations.
Gary
You amaze me with the Chit you come up with and as a craftsmen I know the time it takes to get things like this right.
I suspect I won't be the first to call you a name-Perfectionist!!!!!!!!!
Well done EW and I would be proud to own one of your creations.
Gary
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