John Curl's Blowtorch preamplifier part II

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#36,442
I must point out something here:
I keep reading that I follow 'market trends' or some-such. This is nonsense. I follow my OWN standards developed for the audio industry over the last 35 years.
I would have used an input transformer for SOME cartridges, IF I could be sure that it sounded best in the mid-range, AND did not have too much low frequency distortion. I put out a sincere effort to find the best transformers possible, and even then I was disappointed. No big deal. Nobody told me to use transformers and nobody told me NOT to use transformers, it just fell out that we could get along without them, when I found that the best transformers that I could find, had tradeoffs.
IF I wanted to conform with market trends, I would design tube equipment.
 
#36,444
wayne:

if you don't mind me asking, what characteristics for your preferred choice of hp filter?

mlloyd1

wayne said:
AP did a nice job with uV signals low distortion and a Jensen transformer. Of course this was on the generator side but we still use it to measure uv sweeps on phono stages. Some of the transformers are pretty good but I still prefer not to use one but that is just my choice.
SY you made a very good point about cartridge output when you think of low level music playing VS rated output. While I DC couple I still prefer to use the RIAA HP filter it keeps out more than record warp.
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#36,445
SY said:
You wouldn't happen to know where a schematic of their scheme could be found?
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If it is the one Wayne is referring to, it's the use of a noninductive copper winding in the transformer to be used to temperature-compensate the positive feedback to reduce the output impedance at the secondary and extend the undistorted lower frequency limit. I think it is Hofer's patent, and I saw a schematic. In fact somewhere I downloaded the service manual for an Ap System One so it probably is there too.
 
#36,447
simon7000 said:
I'll take that as you didn't read the article.
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Ed
What you are pointing at? Vertical or transverse modulation?
http://www.diyaudio.com/forums/attachment.php?attachmentid=334646&stc=1&d=1362699535
http://www.diyaudio.com/forums/attachment.php?attachmentid=334647&stc=1&d=1362699535

Or is it distortion related to modulation amplitude?
See some measurements. Formulas in that link predict distortion products. Measurements show this.
http://www.diyaudio.com/forums/attachment.php?attachmentid=334648&stc=1&d=1362699535
http://www.diyaudio.com/forums/attachment.php?attachmentid=334649&stc=1&d=1362699535
http://www.diyaudio.com/forums/attachment.php?attachmentid=334650&stc=1&d=1362699535
http://www.diyaudio.com/forums/attachment.php?attachmentid=334651&stc=1&d=1362699535

But there are a myriad “small” mechanical details that play a role too. See the following for some of them.
http://www.diyaudio.com/forums/attachment.php?attachmentid=334652&stc=1&d=1362699535
http://www.diyaudio.com/forums/attachment.php?attachmentid=334653&stc=1&d=1362699535
http://www.diyaudio.com/forums/attachment.php?attachmentid=334654&stc=1&d=1362699535
http://www.diyaudio.com/forums/attachment.php?attachmentid=334655&stc=1&d=1362699535
jneutron said:
Interesting article.
Not much on anti-skate though
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Skating force is another problem. If you like see here:
http://www.diyaudio.com/forums/analogue-source/75389-think-thhow-puthhy-cat.html#post863681
Apart from antiskating force doesn’t match the change of skating force across the record radius, skating force varies with the dynamics of the recorded signal. Almost impossible to compensate for this

Kindhornman said:
Scott,
Thanks for that RCA reference, makes me wish my Radiotron handbook hadn't been destroyed in flood! Still had information that was useful today, but that the way it goes when it rains into a rented warehouse!
Click to expand...

A waterproof source 🙂
http://ia701507.us.archive.org/25/items/RadioDesignersHandbook/LangfordSmith-RadioDesignersHandbook.pdf

George
 

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#36,450
bcarso said:
I think Wayne is suggesting doing something as an input transformer in some way similar. Perhaps he will clarify.
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There is a trick. Lundahl has it on their site. it allows the transformer to be much smaller. http://www.lundahl.se/pdf/7101.pdf However it doesn't work for this application (I asked).

The AP output transformer trick works but does require virtually perfect matching of the DCR of the transformer, hence the extra winding. I also asked about this and the Jensen guys did not recommend it, too difficult to execute and expensive. They make the transformer for AP.
 
#36,451
1audio said:
There is a trick. Lundahl has it on their site. it allows the transformer to be much smaller. http://www.lundahl.se/pdf/7101.pdf However it doesn't work for this application (I asked).

The AP output transformer trick works but does require virtually perfect matching of the DCR of the transformer, hence the extra winding. I also asked about this and the Jensen guys did not recommend it, too difficult to execute and expensive. They make the transformer for AP.
Click to expand...

Thanks Demian. Yes, after I thought a while I remembered the article somewhere about mic transformers, was it by Gaylord?

I understand that the latest Ap analyzers use a synthetic active transformer, which is o.k. in some cases but of course does not have galvanic isolation.

UREI used to license the patent for the copper resistor and used those transformers in some of their equipment.
 
#36,452
john curl said:
IF I wanted to conform with market trends, I would design tube equipment.
Click to expand...

Why follow building tube equipment market trends - spoken opposite, can we not see it with solid state as well?

Another point is that you only state with masurements. OK, they are fundamental but I'd like to see some objective statements regarding how it sounds. Why you don't compare both prototypes of the phono stage versions (with / without input transformers) and compare them in practical sonical tests. Would be informativ what the sonics results are. Maybe the version with input transformers sounds better?
 
#36,455
Bonsai said:
Objective statements about how something sounds is an oxymoron.
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Depends. If one uses a panel of listeners and collects rankings along various "subjective" quality axes (e.g., "brightness," "clarity," "image specificity," that sort of thing), objective conclusions can be drawn about subjective impressions. These data are often presented in "radar charts." ANOVA is your friend here.

That's not very practical for low volume items made for niche markets, unfortunately.
 
#36,456
Bonsai said:
Objective statements about how something sounds is an oxymoron.
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Not at all. It is very well possible to get objective judgements about subjective perceptions.
Actually, it can be argued that the only judgements about 'how something sounds' that have any value beyond just the single, personal, anecdotal judgement is an objective judgement.

jan
 
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