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Old 17th December 2011, 09:17 AM   #361
Elvee is offline Elvee  Belgium
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Did you also use 2SA970's as input for your previous version?

Could you try to describe more accurately the kind of noise, or even better, capture a bit on wav file?
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Old 17th December 2011, 10:50 AM   #362
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Quote:
Originally Posted by Elvee View Post
Did you also use 2SA970's as input for your previous version?

Could you try to describe more accurately the kind of noise, or even better, capture a bit on wav file?
Yes, I can swap transistors by placed female pin headers. There is no difference with BC's and 2SA970's. As I said before, this noise problem is a known issue due to radio transmitters near my house. Same noise appears in my commercial equipment also. I don't want to bloat this thread with this specific problem.
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Old 17th December 2011, 11:40 AM   #363
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Quote:
Originally Posted by terranigma View Post
I don't want to bloat this thread with this specific problem.
OK, one last suggestion: try to remove completely C5: it might create a (tiny) low impedance RF reception loop within the LTP.
This effect could be damped by leaving R19 alone in the circuit.
Ferrite beads in the emitter leads might also help. It depends on the RFI frequency.
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Old 18th December 2011, 08:13 AM   #364
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Quote:
Originally Posted by Elvee View Post
OK, one last suggestion: try to remove completely C5: it might create a (tiny) low impedance RF reception loop within the LTP.
This effect could be damped by leaving R19 alone in the circuit.
Ferrite beads in the emitter leads might also help. It depends on the RFI frequency.
Yes, It worked. I removed completely C5 and now I have silence again. It looks like that was what they call "microphonic effect" of ceramics. Just remained some very low level hiss that hard to hear closely which probably related with my cabling of current setup. Thank you for great support Elvee.
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Old 18th December 2011, 08:23 AM   #365
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Quote:
Originally Posted by terranigma View Post
It looks like that was what they call "microphonic effect" of ceramics.
Not really microphonic, it is rectification/intermodulation of RF signals.
The ambient RF level at your location must be truly horrendous for something like that to happen: normally, the input filter's role is precisely to keep this kind of signal out of the amplifier, but here the direct coupling with the magnetic component of the signal is sufficient to cause troubles.

You could try ferrite beads on the emitters and/or bases of the IP transistors, this might help.
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Old 18th December 2011, 07:51 PM   #366
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So, Terra, Are you as utterly satisfied with the Circlophone as I am?

I use it in my everyday setup for both music and HT. All purpose. It is great at every task I give it.

Adding to that, I just moved into a new home and of course have a different speaker placement than before. The result: Yet another dimension of audio has been unveiled. Something wasn't optimal with my previous setup. There is much more depth -- and in result, detail -- to the sound.

Now, I have to make an addition to my Circlophone. I need to add a summing amplifier to output to my powered subwoofer. Elvee, what would you recommend regarding this? Right now I'm thinking simple summing op amp setup with an opa27 with its inputs in parallel with the Circlophone's. I can't think of a more simple or better arrangement than this.
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Old 19th December 2011, 08:10 AM   #367
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by odysseybmx414 View Post
Now, I have to make an addition to my Circlophone. I need to add a summing amplifier to output to my powered subwoofer. Elvee, what would you recommend regarding this? Right now I'm thinking simple summing op amp setup with an opa27 with its inputs in parallel with the Circlophone's. I can't think of a more simple or better arrangement than this.
It depends on how your system is organized.
It could be as simple as a 2-resistor passive mixer, if the signal after your main volume pot is buffered and your sub has a high enough input impedance, or it could require two input buffers and one output buffer if you take the signal directly from the pot wipers and your sub is low-Z.
In any case, if an active circuit is required, the OPA27 should be transparent.
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Old 20th December 2011, 08:15 AM   #368
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Quote:
Originally Posted by odysseybmx414 View Post
So, Terra, Are you as utterly satisfied with the Circlophone as I am?

I use it in my everyday setup for both music and HT. All purpose. It is great at every task I give it.
When criticize an amp, I have to take account my source anyway. In my point of view, amplifiers should reveal real capabilities of your source. As what Circlophone does. Despite all fancy words for describing things, I will just say that this amp makes me put a smile on my face while listening music. This is fair enough for me.. Am I utterly satisfied? Yes, indeed. But I'm not finished yet. I'm on trial for investigating effect of different components on sound signature. And I didn't try faster output devices yet.
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Old 20th December 2011, 01:28 PM   #369
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Some great news:

mickeymoose is about to release his PCB version for the Circlophone.

It is a complete one-channel module including the power supply, a balanced preamplifier, a fan, fan controller, auxiliary supplies, and a well thought out mechanical/heatsinking design.

Neat and compact, works like a charm.

Here is a preview of the beta version:
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Old 20th December 2011, 01:32 PM   #370
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