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Old 13th February 2012, 08:24 PM   #661
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Quote:
Originally Posted by danielwritesbac View Post
I'm so curious. You like fine tuning C12, and I wonder for what part of the audio band does tuning that have the largest effect? What varieties are possible by tuning C12?
Thanks!
I just intend to use smaller values with relatively slower output devices. That's all. I hadn't serious listening tests for C12.. I think their purpose more related with stability issues.
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Old 15th February 2012, 02:41 AM   #662
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Ken's soft clipper applied to my amplifier in the picture of post #657, well, this:
Click the image to open in full size.
It got some additional experimentation today, with a lot of different combinations. And much like Edison's 1000 ways not to make a light bulb I discovered quite a few ways not to make a soft clipper. Failures included a bass remover (courtesy of bat86), a hard clipper (when the soft clipper is set too aggressive), a burglar alarm (constructor error), acutance ringing (screaming midrange if 470R is shorted) or a complex device (that does absolutely nothing).

But, after a lot of patience, there was one upgrade that worked.
See the inversely parallel 1n914 clipper at in+ and see the voltage divider (in place of R16 at in-) in that picture with the 470R in-between? I added inversely parallel pair of 1n5819 in parallel to that 470R. It was to see if two decent results could work together, and they did. NICE!!!

That slight change is very similar results to the photo, less clipping, slightly clearer, bigger soundfield size. However, the amplifier now sounds "fresher" and cleaner (super loud russian triode on regulated power kind of sound?) and even bigger soundfield--up to 6 foot wide, 21 foot long soundcast from a single speaker. The clipping performance is much like the original unaltered amplifier's clipping performance, except with more x-max and no significant clipping. I like it a lot!

The really clean presentation applies whether it is cranked up loud or playing quietly. Perhaps a very small amount of feed forward is going on, but I do not know.

It is nice that a 45 watt amplifier can easily do much more, although there is still no explanation for audio power like wind that most 45w amplifiers don't do. Fascinating! Now it is time to build more sturdy speakers.

P.S.
These results are with the Post#1 Circlophone only slightly modified with different output device and driver, with R17 at 20k, and with R21/D8/D9 set to support 31v rails.

Last edited by danielwritesbac; 15th February 2012 at 02:48 AM.
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Old 15th February 2012, 04:23 AM   #663
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On a lark, I changed C6 to 2n2 to try that out. That seems to have done nothing differently, but I wanted to ask if it is okay and what the audible effects may/should be?
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Old 15th February 2012, 12:04 PM   #664
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There are compensations I do not fully understand in more than one place.
Could be bad if accidently tuning two poles closer to the same frequency.
You are probably adding more phase shift and dropping the frequency of
that pole.

Last edited by kenpeter; 15th February 2012 at 12:18 PM.
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Old 15th February 2012, 12:22 PM   #665
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Quote:
Originally Posted by danielwritesbac View Post
See the inversely parallel 1n914 clipper at in+ and see the voltage divider (in place of R16 at in-) in that picture with the 470R in-between? I added inversely parallel pair of 1n5819 in parallel to that 470R. It was to see if two decent results could work together, and they did. NICE!!!
Can you clarify that what is the aim of these alterations? Are these only applicable if using such 22K/470R gain ratio? Or, are you trying to satisfy nfb respecting that high gain? Do you recommend those modifications for gain setting around 30db?

Last edited by terranigma; 15th February 2012 at 12:27 PM.
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Old 15th February 2012, 12:44 PM   #666
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Quote:
Originally Posted by danielwritesbac View Post
On a lark, I changed C6 to 2n2 to try that out. That seems to have done nothing differently, but I wanted to ask if it is okay and what the audible effects may/should be?
It changes somewhat the aspect of the open loop transfer function.

The effect on the closed loop response is infinitesimal, and should not be audible.

2n2 is still safe, but going much further could begin to cause instabilities.
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Old 15th February 2012, 12:44 PM   #667
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He's tuning the knee of his clip to personal taste and voltage headroom.
I think I tuned upon the assumption of 24V rails. Dan's rails are higher.

The aim is to clip something simple and open loop that recovers quicker
than if clipping were to occur within an amplier's closed loop. A soft clip
is also theoretically reversible. Information is distorted in a soft clip, but
not lost. This often sounds less objectionable than a hard clip where
information is smashed flat against a brick wall. And/or cumulative error
improperly "fixed" long after the fact. I don't think Elvee's amp suffers
delayed fix prob, was more in-general gripe about run of the mill clips.

We soft clip to the opposite side of the LTP rather than GND to get a
better feel if the amplifier is handling the situation fine, or needs help.
That way we aren't clipping quite so much more than necessary. It
moves the knee up, and allows for greater linearity below the knee.

Its also more tunable than a stack of grounded diodes of fixed drop.
I would have just tuned the ratio of resistors that make R16. But Dan
might have prefered the sound with a Schottky knee? It is certainly a
different curve than the junction diode alone.

Last edited by kenpeter; 15th February 2012 at 01:11 PM.
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Old 15th February 2012, 01:55 PM   #668
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Quote:
Originally Posted by kenpeter View Post
He's tuning the knee of his clip to personal taste and voltage headroom.
I think I tuned upon the assumption of 24V rails. Dan's rails are higher.
Ok, I got it. It is look like something that I'm not going to deal with.
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Old 16th February 2012, 07:27 AM   #669
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Quote:
Originally Posted by terranigma View Post
Can you clarify that what is the aim of these alterations?
The aim of the alterations is improved sound quality. That's what the added circuit is for. I'm sure that you will find it easy and well worth your time, except if your amplifier is far more powerful than you need, then the soft clip circuit would not switch on. As Ken mentioned, soft clip recovery is possible. Here is one option to remove/reduce compression of recordings.
I have attempted to modify Ken's circuit to imitate a triode sound.
Quote:
Originally Posted by terranigma View Post
Are these only applicable if using such 22K/470R gain ratio? Or, are you trying to satisfy nfb respecting that high gain? Do you recommend those modifications for gain setting around 30db?
They are applicable for 31v rails. For more or less, adjust the R16 voltage divider that is shown on the schematic below.

Well I think that there must be a good reason that you make a power amplifier with gain instead of a large buffer without. As for gain settings you'll want to proof your computer source with free RightMark Audio Analyzer since everything may be just fine until the computer source has to push dynamics. You can have cleaner output (avoid blaring) by having either a preamplifier or Circlophone perform some of the amplification duties and not run the computer source out of headroom for either voltage or current. The easy fix is to turn the computer up only as far as sounds good and then set your gain for the difference so that you can make clean use of your power amplifier's potential.
Applied:
After checking six different sound chips and four different sound cards, I got 20k for R17 (when amp has 31v rails) except for an M-Audio Audiophile that has two paralleled JRC4580 onboard preamplifiers and then R17 at 15k worked in that case. The simplest possible solution for a modern source pushing a power amp larger than ~17w, is gain in proportion to power, which is Very dynamic, whereby you might appreciate the soft clip circuit which activates only when needed, such as realistic replay of a concert with only a medium size solid state power amp.
Quote:
Originally Posted by terranigma View Post
Ok, I got it. It is look like something that I'm not going to deal with.
Opportunity cost applies. My apologies for the quality control outage earlier--Instead of relying on a confusing mess of text that wasn't clear, I should have created a small clean schematic, focused to the point.
This accessory is a potentially desirable integrated amplifier component.
Here it is:
Attached Images
File Type: gif SoftClip.gif (7.8 KB, 317 views)
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Old 16th February 2012, 04:57 PM   #670
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It looks like terranigma's board is a good design.
So, how do we get a group buy of boards?
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