BOZ: Replacement for tip29?

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#2
TIP29 replacement

Hi KT
The TIP29 comes in seven varieties, each with different voltage ratings.
If yours are plain TIP29 or TIP29A, B or C try 2N6123 or BD589.
If they are D, E or F, I don't have a direct replacement listed.
Regarding their sonic performance, I have no knowledge.
Hope this helps.
Rob
 
#4
TIP29 replacement

OK, but the same thing applies. The BD239 also comes in seven voltage variants so you need to know what your supply voltages are.
Also, the hfe or current gain of the BD239 is lower than the TIP29 so you may not get as much output from it.
Cheers
Rob
 
#6
Thanks Rpapps,

Please do pass along the information. I'm using an Avel-Lindberg dual secondary 30V transformer in order to get the required 60V.

I haven't had a chance to look up the transistor specs. Would this tip29 work OK for this voltage? Or would I need another one of the units?

Thanks a lot,
KT
 
#7
Rpapps, I suppose you are right about hfe being lower on bd239. But I get the impression you think tip29 (it’s tip29c by the way) is the output device, but it’s part of the zener voltage regulator. Matching hfe isn’t necessary, as long as it can handle the dissipation.
 
#9
RCA,

BOZ_stand for "Bride of Zen". This is the Nelson Pass designed preamplifier which was meant to be mated with the original Zen amplifier.

BOSOZ stands for "Bride of Son of Zen", which later generation preamp. This was designed to mate with the "Son of Zen", which is a later generation Zen amp. Both the BOSOZ and the SOZ use a balanced topology.

All of these projects were designed by Nelson Pass and graciously bestowed upon the DIY community. These articles and designs were originally published in The Audio Amateur beginning in 1994 and then later in AudioXpress as the designs evolved.

From what I understand, many of these DIY designs aren't too far off of the topologies of Pass Labs' commercial offerings.

The articles and circuits can be found on www.passdiy.com.

KT
 
#10
KT,

Thanx for the excellent explanation. I was searching for a fitting technical topological acronym and had gotten nowhere. I never would have guessed. Like I said. I play with tubes and have virtually no interest anymore in sand DIY for home audio.
 
#11
KT

As we already use IRF610, I would use IRF610 instead of TIP29.

But, two things are to be considered:

- Sum of zener voltage to be about 64V, not 60V
- Add 220 Ohm at the gate of IRF610

You could see detail from the BOSOZ article.

Good luck.
 
#12
Jh6you,

Thank you for the information and the hints.

The tip29 is actually used in the regulator section of the BOZ preamp. The output transistor I plan to use is the IRF510.

Do you have experience with the IRF510 vs. IRF610?

A preliminary search seems to suggest more people prefer the 510. I think I recall a post from Mr. Pass indicating that the IRF510 is preferable, but I'm not 100% sure.

Something about the 510 being more "musical" and the 610 being more neutral, or something like that.

Thanks,
KT
 
#13
Jh6you,

Just re-read your post and realize that you DID suggest to use the IRF610 in the regulator section.

How are the results of this? If this works well, why was the tip29 specified to begin with? Perhaps it's better suited to this task?

Thanks for the hint.

Best,
KT
 
#14
Hi KT

I don't know very well. But, BOZ is the first version and uses TIP29. Meanwhile, BOSOZ is the next version and uses IRF610. In my case, I use IRF240 (leftover from ZENs). Nevertheless, the sound of amp is very good.

I have used both IRF510 and IRF610. For me, I don't feel any difference which could make my face more than 0.1% distortion. If there is any reasonable difference, Aleph preamps should have used IRF510, instead of all the IRF610.

Hope this info will help.
 
#15
KT - I used a MOSFET as the buffer for my stack o' zeners in my own BoZ. I didn't have a TIP29 laying around, but I had plenty of IRF510s. It sounded nice, but a TIP29 would probably also have sounded fine: my room isn't exactly ideal for sussing out the most minute differences. 🙂

Definitely put the 220 ohm (or whatever you have in about that size) resistor right on the gate pin of the MOSFET. Also consider putting a zener (mine was 9.1V) from source to gate (striped end toward the gate; I connected it to the free pin of the 270-ohm gate resistor.)

Good luck,
Erik
 
#17
Hi guys,

OK, so I'm finally getting around to building the thing. I'll use an IRF610 or IRF510 in place of the TIP29.

Erik and jh6you suggest to put a 220 ohm resistor on the gate of the this transistor.

How would I connect this? Does it mean to put the resistor in series with the pin, so that it goes between the gate of the transitor and the pad on the board? Or does this pin attatch to the pad on the board AND the gate pin of the transistor and then terminate somewhere else?

I'm a bit confused about this.

Any clarification would be most appreciated.

Thanks,
KT
 
#20
Hey KT,

Look at any of the schematics from PassDIY and you'll see they
always use a 221ohm resistor on the gate of the FET.

Here is a quote from the Balanced Zen Line Stage article.

Resistors R7, R8, R9, and R10 serve to slightly isolate the inputs and
outputs from the transistor pins, preventing parasitic and other types of
oscillation. The values for these resistors can range from 100 to 475
ohms, and 221 ohms is about the best value.
 
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