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t_majerovic 4th October 2008 02:47 PM

PassLabs Aleph 4.0
2 Attachment(s)

This is my very first discussion thread to DIY community. I'm building Aleph 4.0 like many others people with few modifications (added protection circuit and controlled soft-start circuit).

For beginning I have question about possibility to replace ZTX450 by BC639 (I'm unable to buy/get ZTX450 in Slovakia and BC639 looks similar).

Thank you for answer/reaction in advance.


Gyuri 4th October 2008 04:57 PM

Aleph 4
Szervusz Thomas!
This is a piece with a pleasure!
Do not be sad about the transistors. Any kind of similar one suits.
I hope for it a some kind of friendship, which could serve as a sample to our folk, takes shape between us!
The trouble is never with the individuals!


t_majerovic 5th October 2008 12:07 AM

2 Attachment(s)
Hello Gyuri

Thanks for your post...I read few discussions about ZTX450 replacement by any BCxxx transistor. But it was always connected to smaller PassLabs Aleph versions. Well, I expect that amplifier “first turn on” occurs next month. It shows me if BC639 is right equivalent in this circuit. I'm really curious....

My Aleph 4.0 adaptation uses concept of two mono blocks in common enclosure with independent power supply for each mono block. There is only one common part – power supply soft-start control and input filter.
Currently finished parts are: enclosure, whole power supply and I'm waiting for powerstage components. Oh, and I forgot mentioned that IRFP240 are already matched to 4 groups with 6 pieces transistors (I have 50 pieces population of IRFP240). IRF9610 remains to matching very soon.

Here is look to inside of enclosure my PassLabs Aleph 4.0 adaptation:

Gyuri 5th October 2008 06:17 AM

I am top notch for roughly 100 forints for you if you believe it in that manner to obtain ZTX450 transistor.
The ZTX653 transistor is what I used here, this is real overkill here.
With a greeting:
This amplifier between the most beautiful ones owes, what I saw here.

Taco 5th October 2008 07:24 AM

Very neat layout, a very clean build! :smash:

t_majerovic 6th October 2008 03:04 PM

Hello Gyuri

Thanks for your offer. Today morning I had some email communication to one shop in Zilina. They have few of ZTX450 in store but don’t offer over internet. However we agreed to send transistors over normal post mail service. I expect delivery next Monday.

To Gyuri and Taco:
Thank you for your appreciation…

t_majerovic 7th October 2008 02:07 PM

Schematics - enjoy :-)

I share schematics for everybody who is interested.

Complete schematics of power supply:

Complete schematics of Aleph 4.0 + protection circuit – one channel/mono block:

t_majerovic 15th October 2008 08:08 PM

Today morning ZTX450 and 220uF capacitors arrived. I'm waiting for another package with remains components.

stoN_Cold 15th October 2008 08:23 PM

t_majerovic, do you have some beter Pic, on facebook

Are Unredable!

Regards zeoN_Rider

jacco vermeulen 15th October 2008 10:05 PM


ditto here, me old and blind.
(bigger pics of the girlfriends too, please)

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