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Old 6th July 2004, 11:09 AM   #1
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Default Using output transformers on Zen Amp?

Anyone ever tried to use output transformers on the outputs of the Zen amp instead of the large electrolytic caps? Just curious.
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Old 6th July 2004, 01:45 PM   #2
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I'm also anxious to see the Master's beautiful work with transformer or chokes. He has done beautiful work with GC. When will the transformer acrobatics shows? The last masterpiece with choke or transformer is Zen V-7T, but it stops there.
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Old 14th October 2004, 09:56 AM   #3
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Default Hi.... Output Trans Fans...!

Hello G and Lumanaw...

I think the output trans would make the Zen become more inconvinience for the 'average' DIY fans (like Pass stated in the Balanced Zen and Zen V4 Articles). I guess the Zen7 is very hard to duplicate its output trans....

If you're thinking about the power trans, ELCOs and the HEAT SINK (oah.... the sick one..!), have confused enough, how do those exotic parts would cost us; why do you think about the Output trans....?
It's only make us smaller in this big, wild world...

Regards, KS
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Old 14th October 2004, 10:57 AM   #4
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Power amp yang menggunakan trafo suaranya bagus, lho... Pernah coba?
Memang kalau diukur kacau balau, tapi suaranya enak.
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Old 14th October 2004, 03:41 PM   #5
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I've tried it. You have to remove the CCS and replace it with an inductor larger than 80mH. This inductor acts as a CCS. It has to be capable of handling 2A of DC bias current. I used 120mH that didn't saturate until 2.5A.

I ran the amp at 1.5A bias current, and added a secondary wrap to the inductor - making it into a coupled inductor, or a transformer. I didn't spend too much time calculating the inductance of the secondary.

It worked, but not nearly as good as the original circuit. Power output was very poor, probably a result of the poorly coupled secondary winding.

I have also operated the Zen in the parafeed configuration (yes, I'm a tube guy). This works quite well, but with no obvious benefit. If you exchange the CCS for a 80+mH coil, and run the amp as parafeed, you can cut the heat dissipation by half. There's plenty of threads on choke-loading a zen amp: Choke Loads for Zen/Aleph Amps

Today, I have some big filament transformers coupling the output. I connect the Zen to a 6.3V secondary, and the speaker to the other 6.3V secondary (1:1 ratio). Then I hook some compensation to the primary - similar to Deckard's GIZMO. This works reasonably well for tweaking, but it's not permanently installed in my system. Be careful if you mess with transformers designed for 60Hz - they can't take any DC bias, and they usually have poor frequency response. The ones I'm using, they measured flat past 30kHz.
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Old 14th October 2004, 06:27 PM   #6
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I'm not in love with transformers, or any other part that has
distortion, but sometimes they have their uses.

If you are loading the Drain of a Zen type circuit with an
inductor, I recommend an air core coil. Yes, they're big and
expensive, but they have very little distortion, and you can
start approaching that theoretical 50% efficiency.
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Old 15th October 2004, 02:55 AM   #7
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" Hallo Lumanaw, apa kabar...? Saya pernah coba pre-amp Output Transformer WE417, Suaranya agak rada SLOW, ngga menggebu, dan agak kurang 'transient', 'not open'. Secara 'tone', enak sih, tetapi secara 'fidelity', saya rasa tidak demikian. Trans yang dipakai James Audio 5K:600Ohm.... Jadi udah mahal, ngga paten-paten banget..... agak sedih juga.....! "

The inductors or air coils in Zen, except Kashmire 6.3V trannies, still couldn't eliminate the output Cap (ELCO), right...? Then why don't we use the high tech constant currents source like the Zen did....?

I guess the next tweaking project will be : Single Ended Push Pull
Yeah..... how does it works if we put the Zen single ended for the positive half cycle and the other Zen for the negative half cycle, together. No, I mean this one didn't like the balanced Zen....!
The single ended Mosfets which acts as the signal amplifier, now, is acting as the push pull with the other, and each of them has its own constant current source... Is it possible...? or it just cost us without the worth result...?

Any idea..... or opinion from you, guys...?
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Old 15th October 2004, 03:03 AM   #8
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The output capacitor is removed if you replace the CCS with a large (80+mH) mutually coupled inductor. The inductor has to tolerate large DC currents (2+ Amps) and have good coupling over a large bandwidth.

Mine was pretty lousy with poor coupling and poor bandwidth. I'd rather have the output capacitor!
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Old 15th October 2004, 03:38 AM   #9
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Transformer are not linear. One of the response curve is here http://www.diyaudio.com/forums/attac...amp=1097704812
Look at the curve. +/-6dB and many "Holes" in its frequency response.

But how come some amps are nice sounding with transformers/chokes?

Memang kalau pakai Transformer suaranya jadi berkurang detil dan speednya, agak "Blurry" dan "mish-mash". Jadi transformer nggak bisa dipakai di power-power kelas berat, cuma di kelas ringan saja, untuk fun listening.
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Old 15th October 2004, 05:15 PM   #10
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Quote:
Originally posted by karnovim_salim
[BI guess the next tweaking project will be : Single Ended Push Pull
Yeah..... how does it works if we put the Zen single ended for the positive half cycle and the other Zen for the negative half cycle, together. No, I mean this one didn't like the balanced Zen....!
The single ended Mosfets which acts as the signal amplifier, now, is acting as the push pull with the other, and each of them has its own constant current source... Is it possible...? or it just cost us without the worth result...?[/B]
Running an ordinary Zen in balanced, bridged, or even differential
configuration pretty much achieves something like this, and of
course the phrase "balanced single-ended operation" is one of
the better oxymorons, but don't look at me - I didn't make it up.

Also, I have tried paralleling "mirror" Zens, where one operates
off a + supply and uses an N channel device for the gain stage
and the other operates off a - supply and uses a P channel
device for the gain stage. Totally fascinating result.
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