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Old 20th January 2007, 01:11 PM   #21
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I did build a single channel.

I can report it worked well. I need to get my PC FFT working so I can at least get some basic measurements. But it seemed to sound fine to me.

If there is interest I will get around to designing a proper PCB for it.

I actually used a bipolar PNP for the phase splitter, but really only because I was low on IRF9610s. And only used a single pair of IRFP140s for the heavy lifting.

I will build a stereo amp as soon as I am able.

Cheers!
Russ
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Old 7th February 2007, 07:39 PM   #22
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Hi Alex,

Earlier in the thread you suggested you might elaborate on the implemention of your interesting 'minimalist' circuit design..

"There are limitations and quirks in this circuit - I hope I know most of these and know how to overcome them. Perhaps I should do a brief note on the basic requirements, dangers and solutions in this circuit."

- Alex

I for one would appreciate any further notes you might add regarding the "real-world" application of you amplifier...

Thanks if you have time.
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Old 9th April 2007, 09:58 AM   #23
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Quote:
Originally posted by Russ White
I did build a single channel.

I can report it worked well. I need to get my PC FFT working so I can at least get some basic measurements. But it seemed to sound fine to me.

If there is interest I will get around to designing a proper PCB for it.

I actually used a bipolar PNP for the phase splitter, but really only because I was low on IRF9610s. And only used a single pair of IRFP140s for the heavy lifting.

I will build a stereo amp as soon as I am able.

Cheers!
Russ

Mr Russ,
Any updates on your X-Pro based NQCA.....

Kanwar
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Old 9th April 2007, 11:22 PM   #24
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Quote:
Originally posted by Workhorse



Mr Russ,
Any updates on your X-Pro based NQCA.....

Kanwar

I can only report that I have tested a pair of amps based on this design, and they sound very good. I cannot adequately measure them yet, but they are stable with no detectable white noise/hiss. I cannot hear any nasty crossover distortion as I have with some other FET amps with low bias current.

My measured bias is < 70ma

I will later try a more powerful amp with better PCBs.

Cheers!
Russ
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Old 10th April 2007, 01:36 AM   #25
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How about posting a working schematic so that all members would be able to see that design...
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Old 10th April 2007, 02:24 AM   #26
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I am sure I will. The version I built used only two N-Channel FETs as X-pros did, and is probably good for around 50W.

It been a few months since I even looked at it, I will see if I can dig them up.

I used IRFP140s for the power transistors.

I used both BJT and IRF9610 for the phase splitter.

Cheers!
Russ
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Old 26th May 2010, 04:53 AM   #27
lhquam is offline lhquam  United States
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Default X-pro's Quasi or "current sharing" is circlotron (almost)

I am not sure whether this should be the start of a new thread or not, but I will propose that the output topology used by X-Pro in the Creek amps (5350 4330) are essentially equivalent to a the output topology of the Circlotron (aka. floating bridge). The main different is in the phase splitter. If the output stage gates of both topologies are driven transformer coupled, then they are equivalent except for various parasitic elements that are never modelled in Spice simulations.

(This is my first attempt to insert image attachments in a forum message, so I apologize for some likely formatting problems.)

Figures 1a and 1b illustrate the topologies. Their only difference is the order of the power supply in the two current loops. With the transformer coupling, this ordering is irrelevant.
figs1a-1b.jpg
Usually we want to avoid transformer coupling (and sometimes avoid capacitor coupling too). Therefore we must have drive circuits for gates of the output FETS which have low distortion properties.

Michael Rothacher's paper "Build the the Amazing FET Circlotron"
http://www.passdiy.com/pdf/Build%20T...Circlotron.pdf
Below is Figure 7 from that paper showing the totally symmetric (identical) drive circuits for the two output FETS. This cct requires balanced inputs, which will usually necessitate a proceeding phase splitter stage, thus creating an assymetry in the overall cct.
FET-Circl-fig7.jpg


Alex Nikitin's paper "N-channel D-MOSFET output stage with improved linearity" http://www.ant-audio.co.uk/Theory/N-...0linearity.pdf shows a Quasi (or as Alex prefers) "current sharing" output stage with several different optimizations of the driver stage. Here is the variant that is used in the Creek 5350:
x-pro-fig4.jpg

My claim is that the two topologies are nearly identical, except for the phase splitter parts of the circuits. If the phase splitters can be designed to minimize distortion (and other potential problems), then there should be no difference in the performance of the two topologies.
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Old 26th May 2010, 11:34 AM   #28
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I much prefer Alex Nikitin's topology, but I must admit I've not built or tested it.

Have you by chance?

I would prefer a singleton phase splitter, but then, that could not be direct coupled....

Hugh
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Old 6th October 2013, 04:37 AM   #29
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Alex,

After going through the topic in more depth. I agree with you that non-complementary and Quasi-complementary have substantial difference in way of their working and emulating reflected impedances at output. Thanxz for teaching me with nice explanations and clearing my ignorance.
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Old 10th October 2013, 07:02 AM   #30
AKSA is offline AKSA  Australia
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Kanwar,

By ending up with different output impedances from each half, you force higher levels of H2 and H4. Put another way, this sounds a bit more warm.

Some people actually prefer a quasi amp over a complementary output stage.

But then you knew this already.....

Ciao

Hugh
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