Aleph clones using BJT

Mambo · 3rd March 2003, 10:27 AM

Are there any drawbacks upon building an Aleph clone all with BJTs ?

Like
- KSA1220A/MJE350 in the input stage with MJE15033 as current source
- Darlingtons MJ11032/MJ11016 or "custom darlingotns" with MJE243+MJ15003 or MJL3281

I'm simulating such a configuration and it seems to work ok, at least for DC operating point and transient analysis.

Thank You

Nelson Pass · 3rd March 2003, 04:25 PM

No reason why it couldn't work.

DRC · 3rd March 2003, 04:42 PM

Quote:

Mambo wrote
Are there any drawbacks upon building an Aleph clone all with BJTs ?

Quote:

Nelson Pass wrote
No reason why it couldn't work.

How about and AlephX in BJT flavour ?
Has anyone tried (built / simulated) this ?

Dave

Nelson Pass · 3rd March 2003, 08:32 PM

Mosfets are favored because of their high input impedance
and also because their high Vgs makes it easy to insert control
circuits that operate at 4 volts or so, rather than the 1.4 volts
seen in a darlington.

Mambo · 4th March 2003, 09:07 AM

The lower input ipedance of BJT requires higher current from the input differential pair; I'm getting good results (in simulation) with about 25 mA each.

Due to their lower Collector-Emiter on resistence BJTs should give you a lower output impedence also for low power versions of the clones (A5 and A3) and thus a better control like the big Aleph 1.2 and 2.

3rd March 2003, 10:27 AM	#1
Mambo diyAudio Member Join Date: Feb 2002 Location: Italy	Aleph clones using BJT Are there any drawbacks upon building an Aleph clone all with BJTs ? Like - KSA1220A/MJE350 in the input stage with MJE15033 as current source - Darlingtons MJ11032/MJ11016 or "custom darlingotns" with MJE243+MJ15003 or MJL3281 I'm simulating such a configuration and it seems to work ok, at least for DC operating point and transient analysis. Thank You

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3rd March 2003, 04:25 PM	#2
Nelson Pass The one and only Join Date: Mar 2001	No reason why it couldn't work.

3rd March 2003, 08:32 PM	#4
Nelson Pass The one and only Join Date: Mar 2001	Mosfets are favored because of their high input impedance and also because their high Vgs makes it easy to insert control circuits that operate at 4 volts or so, rather than the 1.4 volts seen in a darlington.

4th March 2003, 09:07 AM	#5
Mambo diyAudio Member Join Date: Feb 2002 Location: Italy	The lower input ipedance of BJT requires higher current from the input differential pair; I'm getting good results (in simulation) with about 25 mA each. Due to their lower Collector-Emiter on resistence BJTs should give you a lower output impedence also for low power versions of the clones (A5 and A3) and thus a better control like the big Aleph 1.2 and 2.

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