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John Curl's Blowtorch preamplifier part II
John Curl's Blowtorch preamplifier part II
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Old 1st March 2013, 01:25 AM   #36051
bcarso is offline bcarso  United States
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Originally Posted by Kindhornman View Post
bcarso,
I could be wrong about it but I think it has to do with another thread that Christophe has pertaining to an amplifier protection circuit. It is an external comparator taking a signal from the output and comparing it to the input signal. He can correct me if I am wrong but that must be part of the circuit that he has proposed in his own thread.
Do you know what that thread is? I don't even know if the two inverters on the left signify two independent power amp outputs, or possibly taken together are the two outputs of a single-channel bridge-mode amp.

Actually, if it is something to set some limiter or overload protection, there are ways to make it better even with the one opamp and as well vary the gain with a single potentiometer. However, if it is something to prevent clipping distortion, and the power amp has unregulated rails, I could suggest some more efficacious approaches
 
Old 1st March 2013, 01:42 AM   #36052
Kindhornman is offline Kindhornman  United States
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John Curl's Blowtorch preamplifier part II
The thread is under Solid State and is titled: An ultimate amp protection circuit ?
 
Old 1st March 2013, 02:14 AM   #36053
bcarso is offline bcarso  United States
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Originally Posted by Kindhornman View Post
The thread is under Solid State and is titled: An ultimate amp protection circuit ?
Thanks I found it. The plot thickens
 
Old 1st March 2013, 05:32 AM   #36054
Esperado is offline Esperado  France
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Thanks a lot to all of you, for your interest to my previous question, and your answers. I had dig a little more, and it seem impossible to get anything precise with diodes, or to sum or to rectify: the offset vary following the levels. So i ended with 4 comparators, with two thresholds, no summation between the two sides. It is square, now. Two quad ICs (one more), but less parts around: only 2 resistors for the thresholds and an adjustable for the gap in the middle.
As habit, simple is beautiful. Thanks to you all, again.

Last edited by Esperado; 1st March 2013 at 05:37 AM.
 
Old 1st March 2013, 06:06 AM   #36055
bcarso is offline bcarso  United States
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Originally Posted by Esperado View Post
Thanks a lot to all of you, for your interest to my previous question, and your answers. I had dig a little more, and it seem impossible to get anything precise with diodes, or to sum or to rectify: the offset vary following the levels. So i ended with 4 comparators, with two thresholds, no summation between the two sides. It is square, now. Two quad ICs (one more), but less parts around: only 2 resistors for the thresholds and an adjustable for the gap in the middle.
As habit, simple is beautiful. Thanks to you all, again.
Comparators hooked up with open-collector "wired-AND" outputs, as window discriminators, are a good way to go.
 
Old 1st March 2013, 03:57 PM   #36056
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Originally Posted by bcarso View Post
Comparators hooked up with open-collector "wired-AND" outputs, as window discriminators, are a good way to go.

MC34161, MC33161 from Onsemi could further simplify the task.
 
Old 1st March 2013, 04:50 PM   #36057
jan.didden is offline jan.didden  Europe
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It's a bad season for audio. James Bongiorno also passed away, as well as Larry Klein, long-time editor of Stereo Review. And Brian Cheney from VMPS Loudspeakers.

jan
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Old 1st March 2013, 05:12 PM   #36058
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In recent years, most of my design efforts have gone to phono stages, rather than line stages. I don't think that I will ever be able to improve the CTC Blowtorch in any way that would be useful, and certainly I would hate to go through all that effort and cost, once again. This is not true with phono stages, however.
Just this morning a received an E-mail from a CTC Blowtorch owner to UPGRADE his preamp with a phono stage. Last week, an associate virtually 'begged me' to start up Vendetta again. Apparently, the customers are out there, as vinyl has gained an upsurge.
What about the 'software'? Of course, there is the old vinyl that often is amazingly good sounding, better than 20-40 year old analog tape ever could be, if properly stored and not ruined by many plays on cheap equipment. There is also 'new vinyl' that is actually backlogged at the record pressing plants as it is so popular. Is it as good, or 'better' than the old vinyl? I don't know yet. It depends on the processing, sources of the music, i.e. CD, DSD, DXD, or whatever. With my allergy to digital, if any digital processing is used in the production of the vinyl recording, then all bets are off, and maybe another approach should be used, instead.
My biggest worry today, is using a digital delay for 'preview' rather than the old way of putting a reproduce head a few feet ahead to capture the signal and tell the control electronics in the disc cutter how much to widen the groove. Other methods could be used, and I hope that they are, but you never know without investigation.
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Old 1st March 2013, 05:51 PM   #36059
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Now, some would say: ' A phono stage is not a line stage' and imply that it is off topic, but it is not! Several CTC Blowtorch preamps have phono stages, that was offered initially at additional cost. It is the 'very best' way to have a Blowtorch, but many customers already had Vendetta Research SCP-2 phono stages or they were already totally digital, so few were built with the phono stage built in. Yet, it was a significant addition to the CTC Blowtorch, and I would not have it any other way.
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Last edited by john curl; 1st March 2013 at 06:11 PM.
 
Old 1st March 2013, 06:05 PM   #36060
bcarso is offline bcarso  United States
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Quote:
Originally Posted by john curl View Post
In recent years, most of my design efforts have gone to phono stages, rather than line stages. I don't think that I will ever be able to improve the CTC Blowtorch in any way that would be useful, and certainly I would hate to go through all that effort and cost, once again. This is not true with phono stages, however.
Just this morning a received an E-mail from a CTC Blowtorch owner to UPGRADE his preamp with a phono stage. Last week, an associate virtually 'begged me' to start up Vendetta again. Apparently, the customers are out there, as vinyl has gained an upsurge.
What about the 'software'? Of course, there is the old vinyl that often is amazingly good sounding, better than 20-40 year old analog tape ever could be, if properly stored and not ruined by many plays on cheap equipment. There is also 'new vinyl' that is actually backlogged at the record pressing plants as it is so popular. Is it as good, or 'better' than the old vinyl? I don't know yet. It depends on the processing, sources of the music, i.e. CD, DSD, DXD, or whatever. With my allergy to digital, if any digital processing is used in the production of the vinyl recording, then all bets are off, and maybe another approach should be used, instead.
My biggest worry today, is using a digital delay for 'preview' rather than the old way of putting a reproduce head a few feet ahead to capture the signal and tell the control electronics in the disc cutter how much to widen the groove. Other methods could be used, and I hope that they are, but you never know without investigation.
I've been purchasing some of the new vinyl and some of it is spectacular. And I have plenty of well-preserved old vinyl with which to compare. I suspect that the cutting is done in other ways, with a score so the operator knows in advance and doesn't rely on a hardware delay.

Of the latter (old vinyl), I was stunned the other evening by an old Nonesuch release, Calliope Festival. Now granted that Renaissance music is often of fairly limited dynamic range; but the fidelity and quiet surfaces were quite staggeringly good. I would suppose the record had been played once before, possibly never (the inner sleeve had that characteristic foldover of corners, which I always straighten out. But it was not in shrinkwrap.
 

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