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Old 30th January 2008, 06:25 PM   #1
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Default BR6521 and BR6522 power transistors for a Bryston Amp

This goes especially to anatech. But any electronic pro could help:

I'm repairing a Bryston B4 amp and also having trouble by finding a suitable replacement for the BR6521 and BR6522 power transistors.

In a previous post I found that "2N5631 and 2N6031 are a good pair (anatech)" ( -> same as NTE60 and NTE61).

The Bryston had beed repaired ones before, and MJ802's were replacing all of the BR6521 transistors on one channel. MJ802 corresponds to NTE181, normally used as pair with the NTE180.

What do you think might work best: NTE60/NTE61 or NTE180/NTE181?

Thanks in advance for your reply.

PhantomBox
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Old 31st January 2008, 02:36 AM   #2
BrianL is offline BrianL  United States
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I would presume that you mean "4B", not "B4"

To venture a wild guess, I would presume that they are custom-selected, custom-marked (ergo the "BR" for "BRyston" prefix). Likely, Bryston has the factory select for fairly close parameter tolerances that yields more consistent match between PNP and NPN devices.

The obvious first pass is to replace "BR" with "2N", "MPS", or one of the Japanese transistor prefixes. It doesn't seem to yield anything useful.

You could look at Toshiba and On Semi for their latest audio power transistors and give those a try. You can only guess at match of devices.

Ya know, you could order some from Bryston. I hear they have very good support, and shipping around the world shouldn't be too hard. Try sending them an email. The amp might even be still under warranty.
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Old 31st January 2008, 01:58 PM   #3
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Thanks BrianL.
Non of the Japanese prefixes gives me any result (just tried out any combination that I know of).
And asking Bryston for assistance doesn't help me either, I have to get the amp fixed for yesterday.

MJ802 (replacment of a BR5621, the only clue that I have) is a transistor equivalent to NTE181, and the number I can get at a local supplier for that transistor is 2N5882. Counterpart to that would be NTE180, equivalent to 2N5880, I assume.

As "anatech" mentioned in an earlier post, he uses 2N5631 for BR5621 and 2N6031 for BR5622 (equivalent to NTE60 and NTE61, numbers that actually are available to me), I would like his opinion on what pair he'd prefer: 2N5880/5881 or NTE60/61?

Thanks again,

PhantomBox
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Old 31st January 2008, 02:16 PM   #4
zlast is offline zlast  United States
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Default 4B

http://www.diyaudio.com/forums/showt...postid=1091677
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Old 31st January 2008, 03:30 PM   #5
anatech is offline anatech  Canada
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Hi PhantomBox,
NTE will not cut it. Sorry. You need to buy real transistors with actual numbers on them.

Go for MJ21193 and MJ21194, they are not too fast. MJ15022 and MJ15023 would work also, but might oscillate in a stacked output circuit. I think I have used them in the past, but you should stick with the slower parts.

Bryston parts from back then were not matched very well. The numbers were simply to help keep their circuit a secret. I had to trace the 4B out back then as they refused to release any information. The only specialty part was the TO-220 drivers that they messed up on and required extended leads to reach the socket. That one gave me a laugh. Imagine how much money that added to the cost that was avoidable. Well, they had their custom part and the other only looked custom.

-Chris
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Old 31st January 2008, 11:02 PM   #6
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Thanks an awefull lot, Chris.

I don't know much about how to interprete the datasheet specs for a specific transistor, but I can try to locate these particular numbers.

By the way: you don't happen to have (or know where to get) the schematics of a 1987 Bryston 4B amp? That must be the 1st issue, or very close to that. I found a whole lot of Bryston amp schematics on their homepage, but the mainboard plans are all '88 and up (I just realized that).

Best regards,
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Old 1st February 2008, 04:23 AM   #7
anatech is offline anatech  Canada
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Hi PhantomBox,
Quote:
I found a whole lot of Bryston amp schematics on their homepage, but the mainboard plans are all '88 and up (I just realized that).
Darn! I fired my hand drawn schematic into the garbage years ago after Bryston put these diagrams up.

They should be pretty close. Possibly some component changes, but the basic circuit should be the same. The current drawings should be usable, especially if you mark down the differences.

-Chris
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Old 1st February 2008, 05:03 AM   #8
taj is offline taj
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Quote:
Originally posted by anatech

Bryston parts from back then were not matched very well. The numbers were simply to help keep their circuit a secret. I had to trace the 4B out back then as they refused to release any information. The only specialty part was the TO-220 drivers that they messed up on and required extended leads to reach the socket. That one gave me a laugh. Imagine how much money that added to the cost that was avoidable. Well, they had their custom part and the other only looked custom.
-Chris
Ha ha... Chris, you're never gonna cut them any slack are you? You'll go to your grave cursing Bryston's name all the way. You have to mind your blood pressure. Let it go...


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Old 1st February 2008, 05:11 AM   #9
taj is offline taj
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Oh, and just to add some substance to my nattering... My old 4B's all had 2N3773 and 2N6609.

They might be quite cheap as a drop-in replacement. But I think the MJ21193 & 4 would be a better (albeit more expensive) choice.

..Todd
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Old 1st February 2008, 01:40 PM   #10
anatech is offline anatech  Canada
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Hi Todd,
Bryston doesn't bug me anymore, and haven't for years. I was only providing background and some factual info for the question posed. I understand that the SST amps are very good and I'll accept that.

Your choice of 2N3773 and 2N6609 are good ones. I used to use those until 2N6609 became scarce. They seemed to be available again after about 5 years of being scarce. They would be the better choice as the amp was designed and stabilized with those parts to begin with. My concerns with transistor choice was more centered around speed and oscillations.

I'm glad you got a laugh out of my view on early Bryston product. You ought to hear me when I am pissed with them!

Do you still have an old 4B or two? I have some ideas that might really make them sound much better. This is without changing the actual circuitry. If changes were allowed, I would concentrate on the bias circuit for reliability and to allow good sound soon after turn on. Inrush current limiting would be another worthwhile addition.

-Chris

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