John Curl's Blowtorch preamplifier part II

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john curl

john curl

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Joined 2003
The only time that I used a semiconductor curve tracer recently was for the Blowtorch Mosfets. There, you could really see differences, because Gm seems to vary, without any obvious reason, but with Idss, or Beta, it is not the easiest measurement, where you can make a simple circuit to measure these, and compare with a simple meter.
 
hitsware

hitsware

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Joined 2002
miller-music.one/
Kindhornman said:
As one with no experience in the matching of npn and pnp devices I have a question. Most of what I think I see are matches that are made between the same manufacturer SCAxxx or whatever the numbers are. Are there ever times where the matches in electrical values are better by matching a transistor from let's say Toshiba and another from Fairchild where those match better than the same brand or is there something inherently better matching like devices from a single manufacturer?
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Complementary pairs are usually purposely constructed, thus usually by
a single manufacturer with (perhaps) related part numbers.
 
hitsware

hitsware

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miller-music.one/
This is good for 2 lead devices :
02431x01.png

What (equally simple) needs be added for the 3rd lead ?
 
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Max Headroom

Max Headroom

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Joined 2013
a.wayne said:
Or these .....
STILLPOINTS ULTRA 5 (EA) at Music Direct
Click to expand...

Or these for free.....
htup_0912_07_o+2009_honda_civic_si_sedan+valve_spring_comparison.jpg
A webbing of cured standard roofing/bathroom silicone between the coils damps them.
A heavy slab (an offcut of standard kitchen top granite/marble etc) suspended on springs makes for a very cost effective equipment platform (zero cost !).
Placing another slab on top of line level gear makes for a very high mass assembly that is nicely inert.
Mileage may vary according to donor car.

Dan.
 
Triodethom

Triodethom

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Joined 2009
Triodes are more linear however unless you have SABLE ( stash acquisition beyond life expectancy ) stock then you go down the road of ultra unabtanium . This lends them to Diyers for one off types . Myself unless I have 6 to 12 of a date code and type then I stay away from them . For design of and building of salable product Triodes are far less viable than fets. If your doing it for you self and have 40 or 50 of one date code tube then go for it.
 
scott wurcer

scott wurcer

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Joined 2004
Typical "complementary" NPN/PNP

I just grabbed a couple of graphs for some Toshiba devices sold as complements of eachother. This result is typical of many if not most, Beta/Va quite different as well as saturation characteristics. Absolute Vbe's also all over the place. You can match beta's at one Vce that's about it.
 

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Triodethom

Triodethom

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Joined 2009
Steve Eddy said:
Well to be fair, a good portion of that is due to an air gapped transformer with DC current flowing through its primary.

se
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Thanks ! Every thing has it limits operating them outside of there comfort zone and using transformer to drive a low z speaker when a high z speaker matches better is a problem. I did not say they where perfect nor that they could do every thing for everybody . Rightness of fit for the task .
 
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