John Curl's Blowtorch preamplifier part II - Page 1061 - diyAudio
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Old 5th March 2011, 03:50 PM   #10601
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Quote:
Originally Posted by hhoyt View Post
One thing I would contribute to the discussion regarding subtle sound differences: There are cases, especially in a studio environment but also at home, when the signal is not present and the noise floor sounds clean, but in the presence of signal, ground current noise modulates the signal.
I'm not following you here.

If there's no audible ground current noise when a signal is not present, then how does the presence of a signal cause it to be audible?

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My cure for this historically has been to utilize transformer isolation for cables interfacing with remote rooms. It is the only way I have been able to easily stop a multitude of different noise effects. Historically I used UTC A-20s, but due to their inavailability I currently use Jensen JT-11s.
Check out the CineMag CMLI-15/15B.

Every bit as good in my opinion but costs significantly less.

In fact, the 11P-1 is, in a sense, actually a 15/15B rather than the other way around.

It was Ed Reichenbach of Reichenbach Engineering who designed and manufactured all of the transformers sold by Deane under the Jensen Transformers label (note the "By Reichenbach Engineering" on the jacket).

Click the image to open in full size.

When Jensen split from Reichenbach, they took all the engineering for Ed's designs with them and began making them on their own (well, sort of... It's my understanding that they're wound for them by another company down in the Los Angeles area).

The owner of CineMag is Tom Reichenbach, Ed's son, who acquired all of his father's engineering. So the 15/15B is ultimately the father of the 11P-1.

se
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Old 5th March 2011, 04:08 PM   #10602
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Originally Posted by john curl View Post
Howard, I consider input and output transformers a FIX, rather than optimum audio design. Yes, they work, but at what price in sound and money?
When used properly, there is no price in sound quality in my opinion. They're among the most transparent audio devices around. And given their ability to provide galvanic isolation, the ability to readily accept input from both balanced and unbalanced sources, and their unparalleled common-mode rejection even when fed from unbalanced sources, there's not only no price to pay in sound quality, they also pay dividends.

As for money...

Please. We're talking about this in a thread about a simple audio preamplifier that sold for $20,000.

se
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Old 5th March 2011, 04:13 PM   #10603
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Originally Posted by Steve Eddy View Post
We're talking about this in a thread about a simple audio preamplifier that sold for $20,000.
Don't mention the preamplifier. I did, but I think I got away with it.

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Old 5th March 2011, 04:21 PM   #10604
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Originally Posted by wakibaki View Post
Don't mention the preamplifier. I did, but I think I got away with it.
I'm sooooooo glad I didn't have a mouth full of coffee when I read that.

Thanks!

se
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Old 5th March 2011, 04:25 PM   #10605
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>If there's no audible ground current noise when a signal is not present,
>then how does the presence of a signal cause it to be audible?

I have heard this described as "operational noise".
Noise in a circuit that manifests with a signal, but
is not there at idle. One could maybe call it "random
distortion" or electronic "rub and buzz".
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Old 5th March 2011, 04:34 PM   #10606
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Originally Posted by hitsware View Post
>If there's no audible ground current noise when a signal is not present,
>then how does the presence of a signal cause it to be audible?

I have heard this described as "operational noise".
Noise in a circuit that manifests with a signal, but
is not there at idle. One could maybe call it "random
distortion" or electronic "rub and buzz".
Yeah. But I'd like to know just what the mechanism is that would cause it.

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Old 5th March 2011, 05:18 PM   #10607
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Actually the CTC Blowtorch preamp sold for a time for $50,000 in equivalent Japanese yen in Tokyo, when Bob Crump built them, before 2005.
However, we had to sell them at $10,000 to the importer.
Of this: $2000 went to me for designing, building and testing the circuit boards (4) 2 line, 2 power.
$3000 went to the fabrication of the cases, finishing and detailing.
About $1000 went for the pots ($400), all silver switches ($200) and pure silver wire ($200) and accessories such as screws, connectors, teflon barrier, etc.
This left $3000 for Bob Crump or ME to assemble them, wire them, Make a precision umbilical cable with multi-pin connectors, and line cord; test them, and make them as pristine as possible, before putting them in custom fitted (by us) flight cases, and burn them in for at least 20 days. Finally, we have a 'lifetime' warranty that has cost me many thousands of dollars to honor, due to import-export fees, shipping, and erratic owners, one of whom blew up 2 of our power amps and both channels of the CTC Blowtorch due to a mod to a tuner by someone else.
Oh, yeh! WHAT A PROFITABLE UNDERTAKING!
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Old 5th March 2011, 05:25 PM   #10608
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Collecting stunning women does sound like more fun.
Reviewing them is more fun....and far less expensive. And besides they still need tweaking and modification to get them to perform correctly.
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Not so fast. Remember what he also said?
"I buy my specs from the local $2.00 shop, and for the princely sum of $12.00 I got 6 pairs that cover the whole range of powers available."
How stunning they really were could depend on which set of specs he was wearing. Lens Changes Everything. Could have been the Placebo effect, especially if he was wearing the rose colored ones.
Haha, my eyes are perfectly fine for general usage...I only need specs for reading the fine print.
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Who dat, Mike Bubble?? You mean Michel Boo-bley accent grave over the e, never heard of him. I hear Liszt garnered the same treatment.
After working two shows in a row, I mean Michael Booble with the accent on the first syllable....he buzzed into the outdoor catering tent today on a Segway and nearly ran me over.
I said, "You got a license for that thing" and we both laughed....him at my joke, and me at him.

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Old 5th March 2011, 05:56 PM   #10609
hhoyt is offline hhoyt  United States
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Default Noise Modulation

Quote:
Originally Posted by Steve Eddy View Post
I'm not following you here. If there's no audible ground current noise when a signal is not present, then how does the presence of a signal cause it to be audible?...
Good question; the two mechanisms I am aware of are: conducted RF on shields which is demodulated in input stages, and modulation of DC operating points by ground potential lift inducing currents in chassis and PCB traces.

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Originally Posted by Steve Eddy View Post
Check out the CineMag CMLI-15/15B. Every bit as good in my opinion but costs significantly less. In fact, the 11P-1 is, in a sense, actually a 15/15B rather than the other way around. se
I appreciate the info! Budgets being what they are at non-NPR college stations, we need all the help we can get!

Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill
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Old 5th March 2011, 06:01 PM   #10610
hhoyt is offline hhoyt  United States
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Default Transformers

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Originally Posted by john curl View Post
Howard, I consider input and output transformers a FIX, rather than optimum audio design. Yes, they work, but at what price in sound and money?
I agree, any performance limiting component is best eliminated, but what I was referring to was the fact that many people claim certain tube gear to have the best sonic characteristics. Without getting into a discussion of solid-state vs thermionic circuits, what I was interested in hearing you comment on was; if some of that tube gear sounds so good, maybe the galvanic inter-stage isolation aspect of the transformers inherent in their design is part of the reason?

Howard Hoyt
CE - WXYC-FM 89.3
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