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Old 3rd April 2019, 06:12 PM   #6181
amplidude is offline amplidude  Denmark
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By the way, I'm thinking about using other output transistors , I have from another project 2sc2608 2sa1117 to3 sanken nos ,the entire output board will be mounted in a u profile aluminium, the to3 drilled in thorough sides of profile, think it will give good heat dissipation.
If you have pics, suggestions, or other input I'm in
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Old 3rd April 2019, 07:27 PM   #6182
chalky is offline chalky
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Yes I 'm going to build a complete amp. I got the same set of pcbs as you. I think you should be ok with the 2sa1117/2sc2608 pairs. They have relatively low hfe and the ft isn't even quoted, so I assume that its quite low. This can be important with output stages like the Bryston as its almost impossible to get it stable if you use high hfe, high gain modern transistors. That's also why the output stage has gain; its not unity gain stable. I don't intend to experiment with the output stage but to try some of Douglas Self or Bob Cordell's improvements to the input stage. Maybe we should start a separate thread rather than hijack this one.
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Old 3rd April 2019, 07:46 PM   #6183
chalky is offline chalky
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Hmm, just found more complete datasheets for the 2sa1117/2sc2608 pair and the ft is given as 20MHz as opposed to 4MHz minimum for the mjl21193/94. 20MHz may be a bit high for ft, but if you try the amp with single output pairs and a current limited power supply, as suggested in the debugging instructions that came with the pcbs, then you should be safe enough if the amp oscillates. Keep an eye on R59 ( 10R 3W ) which will get hot very rapidly if the amp oscillates.
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Old 5th April 2019, 04:24 PM   #6184
Roobarb is offline Roobarb  United Kingdom
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Default Greg Ball Mono's

After almost giving up on this project following frying one of the boards, I finally got them working and finished. Here's my pair of GB150D Mono Blocks in the making....
1 Will it fit .jpg

2 Laid out.jpg

3 Amp Board.jpg

4 Amp to Cooler.jpg

5 Testing.jpg

6 It does fit.jpg

7 Inside .jpg

8 Finished.jpg

9 Woodwork.jpg
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Old 5th April 2019, 06:47 PM   #6185
kct is offline kct  Canada
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Post your Solid State pics here.
^^^ Nice.
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Old 5th April 2019, 08:52 PM   #6186
fuego is offline fuego
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Nice
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Old 5th April 2019, 09:54 PM   #6187
Roobarb is offline Roobarb  United Kingdom
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Thanks guys, they sound superb too. I had a McIntosh 2600, which got rapidly dumped after about 10 minutes of listening to these..
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Old 9th April 2019, 04:11 PM   #6188
apexaudio is offline apexaudio  Serbia
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APEX A40
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Old 9th April 2019, 04:32 PM   #6189
amplidude is offline amplidude  Denmark
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Quote:
Originally Posted by chalky View Post
Hmm, just found more complete datasheets for the 2sa1117/2sc2608 pair and the ft is given as 20MHz as opposed to 4MHz minimum for the mjl21193/94. 20MHz may be a bit high for ft, but if you try the amp with single output pairs and a current limited power supply, as suggested in the debugging instructions that came with the pcbs, then you should be safe enough if the amp oscillates. Keep an eye on R59 ( 10R 3W ) which will get hot very rapidly if the amp oscillates.
Hi chalky, are you making progress on your boards?,starting a new Bryston clone thread might be an idea, but I'm not online that often so I would not be able to participate often, don't now if anybody else are fiddling with Therese boards.
I'm having difficulty finding the two bridge rectifiers, they're leg orientation isn't all that standard, also the two spdt switches on input board are troubling me, so now I'm stuck with 35 CK switches and none fit, the guy only sold as lot..
I would love some pics of your progress and info on any enhancements on the input board.
Regards thomas
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Old 11th April 2019, 06:44 PM   #6190
chalky is offline chalky
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Hi Thomas, My board sets have arrived and I'll be picking them up from the Post Office tomorrow ( need to pay some import duty ). I have bought complete semiconductor sets for the four channels that I'll be building. Easy to get almost perfect matches between groups of npn or pnp transistors, but alas npn to pnp matching between any of the complementary pairs used isn't that great. Doesn't matter quite so much for the output stages because of the topology, but would have reduced the raw thd of the input stages a little if matching was better. Ah well thank goodness for nfb! Regards, David
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