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Old 21st January 2012, 02:30 PM   #41
6L6 is offline 6L6  United States
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You can't build just one...

No real news, I've just been lazy and haven't made the drawings to give to the machinist. I can't go any further until the enclosure is complete, because I need the real enclosure to measure for parts fit, and to see where things will actually place and mount.

The other delay is that I started a Sonos system, and having a Class-A amp (my F5) just cooking away for background music is a little silly... So I have a chipamp project that is taking what little time I have for building.

That said, this will get back on track, hopefully soon.
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Old 19th December 2012, 12:59 AM   #42
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Quote:
Originally Posted by 6L6 View Post
Here is a copy of the schematic that Nelson drew out for me at Burning Amp (well, he modified and made notes on an Aleph J schematic) Not significantly different than the original.

Click the image to open in full size.
Thinking about putting this together - have boards, psu and 4 ssR100s.

Is the pot that is added between input jfet and output jfet really 500k?

I ask because in the Semisouth Aleph J forum post !2 Nelson states

I think you can see significant improvement by simply
dropping the Jfet in on the negative side - the IRF240
on the top (aleph) side can be left as is.

To bias it properly you will need to drop the value of the
resistor from the Drain of the input transistor (and Gate
of the Jfet) to the negative rail to a lower value - I
recommend a 500 ohm pot.

Thanks

Bob
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Old 19th December 2012, 01:22 AM   #43
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Bob,
Run man. Yougot it bad. The Aleph amps are seductive. Big lush midrange. Should have stopped with my monoblocks. Dont say i didnt warn you.
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Old 19th December 2012, 01:34 AM   #44
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The F6 grabbed me. I was even wondering if putting a small pot across R17 and R18 would allow experimentation

Last edited by flocchini; 19th December 2012 at 01:35 AM. Reason: fix
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Old 19th December 2012, 03:54 AM   #45
6L6 is offline 6L6  United States
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Quote:
Originally Posted by flocchini View Post
Is the pot that is added between input jfet and output jfet really 500k?
I will change that, you are correct, it's 500ohm -- your comments about biasing it are spot on.


Quote:
I think you can see significant improvement by simply
dropping the Jfet in on the negative side - the IRF240
on the top (aleph) side can be left as is.
Yes, that's how it's drawn.

My question in should I pursue this amp, or save my unobtanium R100s for an F6...

This project got royally derailed time-wise some time ago, but I was going through my various boxes and bins to realize that I have everything I need to build this amp except the transformer...
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Old 19th December 2012, 08:28 AM   #46
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Default Peter Daniel`s Aleph J boards

I have two sets of Peter`s boards left, either to build two unbalanced stereo sets (= four channels) or one balanced stereo amp.

If anybody is interested, please send a PM
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Old 19th December 2012, 02:52 PM   #47
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"My question in should I pursue this amp, or save my unobtanium R100s for an F6...

This project got royally derailed time-wise some time ago, but I was going through my various boxes and bins to realize that I have everything I need to build this amp except the transformer..."

6L6 - tough question
The F6 is a tremendous learning experience for me and it is great for driving the PHL mids in my system. If SITs became available I would probably want to try them in the F6. The Jango seems like another learning experience. Back to the Zen articles. I still use the Aleph 30 on the low end. My sealed SEAS W26s are not efficient as the PHLs and the Raven so I need the gain.

My friends say take the time and listen. The best way for me to do that is have amps that I can rotate in the system.

Thanks again to those friends and the great DIY community
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Old 19th December 2012, 02:57 PM   #48
Tea-Bag is offline Tea-Bag  United States
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The F6 has nuts I don't remember on the Aleph's - big control - but I never built the 30 - just the Mini.
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Old 19th December 2012, 03:54 PM   #49
Itsmee is offline Itsmee  England
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Quote:
Originally Posted by flocchini View Post
Is the pot that is added between input jfet and output jfet really 500k?
Check the BA2, it's 5K.
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Old 19th December 2012, 04:01 PM   #50
6L6 is offline 6L6  United States
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No, it's not 5K.

It's 500ohm. You only need a Vgs of 1.2v
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