Anyone out there who can match eight 2N3055 for me? - diyAudio
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Old 12th February 2009, 05:44 PM   #1
Salar is offline Salar  Germany
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Default Anyone out there who can match eight 2N3055 for me?

Hi,
I would like to get eight matched 2N3055 for my Musical Fidelity B1 Amp.
I could get some here in Germany, but the minimum is 10 matched pairs for a total of
140 Euros.
So anyone out there, who can do this work as well?
(And who has no counterfeits )
I did attach the schematics, maybe one gets a clue, which measurements are
are needed. BTW, I need also the driver transistors T15-T18, but when I am looking
for them on the web, I do not get a result.
Here is the schematic

All the best,
Sal
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Old 12th February 2009, 09:10 PM   #2
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consider using a new device with a higher SOA?

The 2N3055 is fairly old and of limited current rating...

...also the emitters have fairly large value resistors, so matching probably won't buy you a whole lot. You could just buy a small batch, pop them into a test circuit and test them for static current at the same bias level that the amp runs them at (check the voltage across those resisitors). That will be more than close enough for this amp.

This is especially simple if there are only 4 devices per channel, as shown - an easy match job.

you probably don't really need to match them...

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Old 12th February 2009, 10:00 PM   #3
mjf is offline mjf  Austria
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hallo.
wenn ich richtig lese: treiber bd137/bd138.... leicht erhältlich.
bc184/bc214 müssten auch noch erhältlich sein (vergleichbar mit bc550/bc560),die typen mit bezeichnung L haben eine andere anschlussfolge (bitte nachsehen).
matching der 2n3055 dürfte nicht allzu kritisch sein........
grüsse...............
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Old 12th February 2009, 11:33 PM   #4
Salar is offline Salar  Germany
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Hello bear, hallo mjf,
bear, do you have a proposal? Replacemets for the 2N3055 should fit without
changing the circuit.
If not: with
Quote:
With static current at the same bias level
you mean measuring hfe?

Should bd137/138 and/or bc184/214 also be matched or are those even less critical?
BTW, found a good thread about adjusting the MF B1 over here:
Biasing MF B1
All the best,
Sal
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Old 12th February 2009, 11:40 PM   #5
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If you wanted to you could build a tester yourself. I think there is a DIY design on Rod Elliot's site (Elliot Sound products) in Sydney Australia. That has been used to match T-03 devices for class A amps. More work and some expense but a bit of fun too!
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Old 12th February 2009, 11:46 PM   #6
Salar is offline Salar  Germany
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Quote:
If you wanted to you could build a tester yourself. I think there is a DIY design on Rod Elliot's site (Elliot Sound products) in Sydney Australia. That has been used to match T-03 devices for class A amps. More work and some expense but a bit of fun too!
Hi jonathan,
thanks, but my technical abilities and knowledge are VERY limited.
Just liked to get matched pairs (again is HFE is sufficient?)
solder them in my amp and try to bias the amp like it was done in the link above...
All the best, Sal
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Old 13th February 2009, 03:55 AM   #7
EUVL is offline EUVL  Europe
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As to modern devices, you could try MJ15003, or even MJ21194 (for audio). The latter "may" cause oscillation though. See :

http://www.tcaas.btinternet.co.uk/jlhupdate.htm

I don't think you need all 8 identical (that would be ideal of course). You need minimum 4 matched pairs (to ensure equal current sharing), and preferrably 2 matched quads.

I have some matched MJ15003s left if that is what you want to try. Pls contact by PM.

Gruss,
Patrick
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Old 13th February 2009, 06:38 AM   #8
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You can use the MJ802 in place 2N3055, are better Tr...
Realy need matched Tr's parallel output in gain (hfe), or put resistor degenerative the colector of Tr's(0.1 ohm)
Ex: http://sound.westhost.com/project03.htm (last fig.)
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Old 13th February 2009, 07:15 AM   #9
jaycee is offline jaycee  United Kingdom
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MJ15003/4 or MJ15024/5 works well with this amp, and they are more robust than the original 2955/3055. I wouldn't risk the MJ21193/4's as they most likely won't be stable.

I've never heard an A1/B1 but from reading Mark Hennessy's site about them, the design does not impress me one bit!
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Old 13th February 2009, 07:32 AM   #10
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