Anyone know a good substitute for 2N5401?

[GlasgowGrip]

Hello all,

I'm doing a minimalist refurb of my Hafler DH-200, no real mods, basically just upgrading caps, a few key resistors, the power switch and rectifier bridge. I'm also looking to replace the 2N5550 and 2N5401 differential pair transistors to lower the offset - it has high offset on the R channel at 111 mV. The L channel is fine at 10 mV, but I would still replace all diff pairs to keep things symmetrical.

I can still source ON Semi 2N5550's from Mouser/Digi-key, however it looks like 2N5401 is obsolete and has gone out of stock, unless I go with Central Semiconductor parts from Mouser.

Question: Is it a safe bet to go with Central Semi for the 2N5401's? (I've had good results with a few of their TO-39 cans, but otherwise have no experience with them.)

I looked through the usual suspects I have on hand, but nothing fits all the criteria. The combination of high voltage, current, gain and bandwidth seems no longer readily available in a TO-92 package - or am I overlooking something?

2N5550 NPN - VCEO: 140V, VCBO: 160V, VEBO: 6V, Ic: 0.6A, Pd: 0.625W, hFE: 60-240, fT: 100 MHz
2N5401 PNP - VCEO: -150V, VCBO: -160V, VEBO: -5V, Ic: -0.6A, Pd: 0.625W, hFE: 60-240, fT: 100 MHz

Hopefully this is a question might help out another AK'er in the future with a Hafler DH-200 or DH-220. Thanks in advance! - Steve

 

[GlasgowGrip]

P.S. It looks like this substitution will also be relevant for the Dynaco ST-400, where the 2N5401 has been recommended as the replacement for the 2N4889, the first differential pair on the PC-28 board at Q201/Q202.

 

[Semanon]

2N5401 by On Semi in stock at B & D Enterprises for under a buck.

 

[GlasgowGrip]

I'm unfamiliar with B&D Enterprises, have you used them much? I just did a search on AK and I do see several other well-known AK'ers giving them a recommendation, so it looks like I should give them a try. Thanks for the head's up! bdent.com

 

[Semanon]

They have hard to find stuff. Never had a problem with their quality or shipping. Never had to use customer service, so can't comment there (but thats a good thing).

 

[dr*audio]

BD Enterprises only sells genuine parts, no counterfeits. They do charge too much for shipping, though.

 

[roger2]

Just a question, does the DH-220 really use two different transistors, an NPN and a PNP, for the differential pair?

In all the cases that I have come across the diff pair was comprised of two matching transistors. But I have never worked on a Hafler or looked at a schematic for one....

 

[rcs16]

Yes, it is a complementary diff pair to create a push-pull vas( voltage amp stage)
I am using the rectron 2n5401 from mouser
I bought 2n5401y from Digikey, beta selected from onsemi/ Fairchild
I have not used the central version
I thought dh-220 has a dc offset adj pot

 

[GlasgowGrip]

Just a question, does the DH-220 really use two different transistors, an NPN and a PNP, for the differential pair?

In all the cases that I have come across the diff pair was comprised of two matching transistors. But I have never worked on a Hafler or looked at a schematic for one....

@roger2: The Hafler DH-200 (and the DH-220) has two differential pairs, an NPN pair and a PNP pair. As @rcs16 alluded to, the two diff pairs act in a complementary push-pull fashion. I won't pretend I understand amplifier design well enough to really explain the topology, but it makes sense to my oversimplified way of thinking about it. (And given the excellent performance of the DH-200/DH-220, David Hafler obviously knew what the heck he was doing!)

And to @rcs16: You're correct that the DH-220 does have a DC Offset pot. Unfortunately its predecessor the DH-200 does not. I have seen some threads referring to a DH-200 mod which adds components to the circuit to allow for DC Offset adjustment, but I'm trying to get in and get out of this thing without getting too fancy. I figure replacing the diff pairs with new hand-matched parts is the simplest route.

P.S. I did just edit the original post - I meant to say I have a DH-200, not a 220.

 

[GlasgowGrip]

Update on my original question - given that the ON Semi 2N5550T is still active, I'm hoping to find a good sub for the 2N5401 which is now Obsolete and out of stock at Mouser/Digikey/etc.

First, I went for some NOS - I bought 25 pcs of ON Semi 2N5401 from B&D Enterprises, but they won't arrive until Monday at the earliest. I will report back on what I get.
Second, I decided to try out the Central Semiconductor parts at Mouser - I bought 10 pcs of the Central Semi 2N5401PBFREE since I was putting in an order anyway, and they just arrived this morning.

Just did some matching, and I identified some pairs. I used my el cheapo ATmega328P-based component tester, so these are not lab-grade numbers:
- ON Semi 2N5550T: tested 8 pieces; all 8 pieces had hFE = 208; the Vf ranged from 692 - 700 mV.
- Central Semi 2N5401 PBFREE: tested 10 pieces; hFE ranged from 175 - 182; the Vf for 8 of them was 650 mV, but for 2 pieces it was 682 mV.

I think the Central Semi parts seem okay, so I selected pairs (though I did not use the two that had the higher Vf). I might need to go buy me a better transistor tester at this point - maybe a Peak Atlas?

 

[roger2]

For what its worth...

I have had very good luck matching based on hFE alone and using only an ultra cheap $5 DMM from Harbor Freight. On one amp I actually got a DC offset of 0mv in one channel. And typically have been able to get in the 10-15mv range with no problem. These are amps that have also had all electrolytics and tantalums replaced, so perhaps that helped, I don't know. Relative values of hFE between candidates are what matters when matching, so the testing procedure should be consistent especially in the amount of handling each transistor receives as body heat alters hFE.

You may already know the above, if so apologies. My point is that it can be done without more costly instruments.

 

[GlasgowGrip]

Hey, thanks @roger2! I'm already there with what you're saying, but it never hurts to get a sanity check and positive reinforcement.

So yes, I look for relative hFE values from the el cheap-o tester and I too have had good results so far matching diff pairs by hFE (for a number of vintage SS restoration projects - 5 Marantz receivers, 3 Marantz integrateds, a Pioneer receiver, 2 Pioneer integrateds, a Sansui receiver, a Hafler preamp, a Dynaco power amp). I recently just started keeping track of the Vf measurements as well, in case some kind of pattern emerges (possibly a waste of time).

Anyway, for a procedure, I pull out candidates from the bag or off the tape and let them sit out for several minutes after I've touched them. Then I pick them up with tweezers to put in the tester so they should all be at roughly the same temperature. Certainly not lab precision to be sure, but a low-effort technique that gives repeatable results. Hey, maybe someday I'll splurge for a real transistor tester, or an actual curve tracer, but that's still TBD and somewhere down the road in my vintage audio journey.

 

[gslikker]

In Europe, we have the Diotec ones which are sold by TME.
Unfortunately, I do not know the manufacturers reputation.
At least they are cheap (2 eurocents each if you buy 500).
The last few years I did buy several types of elcheapo through hole transistors to have enough for generic use the rest of my life..