John Curl's Blowtorch preamplifier part II - Page 2435 - diyAudio
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Old 11th July 2012, 01:12 AM   #24341
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Thanks gentlemen, Ive ordered the lot, Im tired of searching and got a good price for the lot, BF862 is good alternative but not TO92 and I dont think I want to change pc boards. Maybe someone knows of a adapter prefer one that brings two parts into thermal contact.
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Old 11th July 2012, 02:30 AM   #24342
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Quote:
Originally Posted by homemodder View Post
Thanks gentlemen, Ive ordered the lot, Im tired of searching and got a good price for the lot, BF862 is good alternative but not TO92 and I dont think I want to change pc boards. Maybe someone knows of a adapter prefer one that brings two parts into thermal contact.
Yes that part is a fluke but it's an out for folks who just want to order some cheap parts from a major distributor and not risk fakes, etc. Plenty of projects posted here where they did just fine.
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Old 11th July 2012, 06:32 AM   #24343
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It is a shame that good complementary jfets are hard to find. They will not be completely unavailable in future, but they certainly will not be as cheap or as easily found as in the past. For many line level applications, the extremely low 1/f noise of the Toshiba parts is not really necessary. Just phono inputs or analog tape reproduce inputs come to mind, or of course, microphone inputs.
I had designed without complementary input devices, until complementary devices became available, but I would not like to revert to non-complementary jfet designs, if at all possible.
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Old 11th July 2012, 10:33 AM   #24344
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Originally Posted by RNMarsh
Note- if a person 'likes' the sound of tube equipment, there are many caps and transformers which if measured as a total system would have worse total group delay from system input to system output.
Not necessarily. A 'conventional' valve amp with decent amounts of feedback could have lower group delay than a 'zero feedback' SE. Although there may be many caps and transformers, the dominant one will be modified by feedback and the rest won't have much effect until subsonic frequencies. Could still end up worse than SS, but below the threshold so OK.

Don't forget that something has to set the LF rolloff to a sensible figure, so that subsonics you can't hear don't create distortion and IM with things you can hear.
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Old 11th July 2012, 01:56 PM   #24345
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Doesn't the massive group delay in the typical woofer obviate any group delay in a typical amplifier?

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Old 11th July 2012, 03:19 PM   #24346
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Probably, but I assumed that these people who are worried about LF have speakers (and rooms) that go down to turntable rumble or even LP rotation levels of subsonics.

Normal people have to put up with amps which stop at 20Hz driving speakers which already stopped at 45Hz.
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Old 11th July 2012, 04:07 PM   #24347
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Probably, but I assumed that these people who are worried about LF have speakers (and rooms) that go down to turntable rumble or even LP rotation levels of subsonics.
I have listened to one of these, you actually could hear the London subway on some old Mercuries (<10Hz components for sure). Amazing
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Old 11th July 2012, 04:42 PM   #24348
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When I once experimented with feedback by acceleration a curved LP spit off cone of the woofer.
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Old 11th July 2012, 06:04 PM   #24349
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LP? Thats the reference now?

Guess I am not a normal person.... have a large living room. Now use 4 -15 inch cerwin vega bass drivers and adding a pair of TC Sounds Ultra 5400 18 inch drivers for subs sitting in the garage waiting for time to get it done. Not much compression and lots of dynamic range.
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Old 11th July 2012, 06:44 PM   #24350
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by DF96 View Post
Not necessarily. A 'conventional' valve amp with decent amounts of feedback could have lower group delay than a 'zero feedback' SE. Although there may be many caps and transformers, the dominant one will be modified by feedback and the rest won't have much effect until subsonic frequencies. Could still end up worse than SS, but below the threshold so OK.

Don't forget that something has to set the LF rolloff to a sensible figure, so that subsonics you can't hear don't create distortion and IM with things you can hear.
Did you miss the words "system"? A single component does not make a system. Look at just the low end roll off of the source (say LP cartridge), the MC pre-preamp, RIAA preamp, line amp, power amp and electronic crossover , if using one. Measure the System from it's input to it's output. It wont look so nice nor measure so well, then. But, that is what you are listening too - a system of interconnected components with thier total sum affects.

Last edited by RNMarsh; 11th July 2012 at 06:48 PM.
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