Hafler DH-200 Transistor Swap. - diyAudio
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Old 18th January 2012, 03:45 AM   #1
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Default Hafler DH-200 Transistor Swap.

What does everyone think about the idea of using a 2N5551 instead of a 2N5550 for Q1-3? I can readily get matched 2n5551's but will need to order 2n5550's in single pairs and wait.

2N5550 is what is shown on the schematic, but the data sheet indicates they are pretty similar. I am quite the novice, so feel free to laugh/flame me.

Here is the data sheet

http://www.onsemi.com/pub_link/Collateral/2N5550-D.PDF

And attached is the schematic.
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File Type: pdf dh-200_amp_schematic.pdf (47.5 KB, 24 views)
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Old 19th January 2012, 05:20 PM   #2
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Just looking at that for myself. I was looking at much newer parts. 2SA2362 ore BD139.
I figure transistor technology may have advanced in 50 years.
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Old 19th January 2012, 06:46 PM   #3
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Default I think there are other options.

I found someone one on AudioAsylum suggesting other transistors and have even exchanged messages with them. You may want to do a search there.

I can get the 5551's quick, matched and cheap, and I have had luck with the original Fairchild components, so in this thread I was primarily focused on 5551 vs 5550 only.

My problem is that I am not an electronics person, so can't really determine if the differences are significant. I am simply going by the fact that they appear side-by-side on the same data sheet which implies they are very similar.

If you have the expertise to advise, that would be very appreciated. However, its not worth it to me to trash the amp on an experiment so be conservative in your advise and err on the side of caution.
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Old 19th January 2012, 07:13 PM   #4
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Will do.
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Old 19th January 2012, 07:25 PM   #5
tvrgeek is offline tvrgeek  United States
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All I found is a recommendation for outputs, which I happen to have on order. ( I was testing the limit of my power supply DH-120 mod and found it)

If you happen to have a link, it would be much appreciated.
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Old 19th January 2012, 08:01 PM   #6
tvrgeek is offline tvrgeek  United States
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Looks to me like the 2N5551 is a very suitable replacement. Slightly lower noise, slightly higher Vec. Not a great transistor from the sheet, but probably better and should not require any circuit changes.

Where are you getting the matched ones? I might get a few.
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Old 20th January 2012, 03:16 PM   #7
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Sorry, I've been slow to reply.

I had the opportunity to buy someones remaining supply and having 2 DH-200's and a couple DH-300's that I'm looking at, I thought it might be wise to simply have some matched pairs available and I would be getting them for a lot less than if I got them individually (matched pairs are expensive because someone has to do the labor to match a pile of them. But once they do, the usually have a bunch of spares left over).

How many would you be interested in? I am getting both 2N5401's and 2N5551's, which is what you would need for many of the Haflers.

If you do a search for DH-200 in this thread I think you will find the discussion of alternative transistors. If not, let me know and I will dig more.
Amplifier Distortion, DC-Offset, and You! [Archive] - AudioKarma.org Home Audio Stereo Discussion Forums
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