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Old 13th September 2009, 09:25 PM   #21
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Quote:
Originally Posted by Lazy Cat View Post
constructors usually place a current mirrors instead of collector resistors but this ruin the musicality even worse.
I don't have much experience, but I agree. Whenever I've tried a current mirror on top of the LTP, the sound has been seriously degraded but the THD has been much lower.

Are you willing to share more of your listening observations? How do you find single end vs complementary stages? What improvements cascoding and CFP make for different stages etc. Have you tried JFETs for VAS?
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Old 14th September 2009, 09:11 AM   #22
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Lazy Cat,
Quote:
which has for the purpose it serves, to small input impedance,
Rather not small enough for the purpose it serves, as it, ideally, should be zero Ohm.
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Old 14th September 2009, 09:42 AM   #23
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Quote:
Originally Posted by Lumba Ogir View Post
Lazy Cat,

Rather not small enough for the purpose it serves, as it, ideally, should be zero Ohm.
Yeah, and zero current too ... ideally, but in a real world there is real impedance anadequately loading previous stage. As said before there are many solutions to this problem, but which one is more musical ... as that's the only thing it counts for me.
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Old 14th September 2009, 10:18 AM   #24
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Quote:
Originally Posted by nelsonvandal View Post
I don't have much experience, but I agree. Whenever I've tried a current mirror on top of the LTP, the sound has been seriously degraded but the THD has been much lower.

Are you willing to share more of your listening observations? How do you find single end vs complementary stages? What improvements cascoding and CFP make for different stages etc. Have you tried JFETs for VAS?

Discrete single ended VAS is filled with double differential stages, current mirrors, folded cascodes ... every possible way (to "suppress" the sound) to bring out symetrical signal, referenced to ground, at its output. Why choosing a lot of electrical tricks to form the signal it can be done much simpler? For me, if it is single ended, it should be until the speaker connection, so fully single ended configuration only.

Symetrical complementary stages have more relaxed, naturaly flown and realistical transient sound than single ended design.

I know that in this forum everything is about the numbers, but sometimes personal listening observations regarding some electrical designs have to be enlightened. I'm sorry if my remarks offend some intelects around here.
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Old 14th September 2009, 10:52 AM   #25
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Quote:
Originally Posted by Lazy Cat View Post
I know that in this forum everything is about the numbers, but sometimes personal listening observations regarding some electrical designs have to be enlightened. I'm sorry if my remarks offend some intelects around here.
I wish more people here reviewed the sound of different topologies and parts more often than they do. It's the sound that matters, "musicality" or "neutrality" or whatever we're after.
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Old 16th September 2009, 06:46 PM   #26
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I'm in the phase to collect some good core parts like toroids, big capacitors, etc.

I was thinking to buy RIFA low ESR, low ESI capacitors 22 mF/100V (PEH169PV5220QB2) and ultrafast recovery rectifier double diodes 2 x 60 A/400 V (STTH120R04TV) for the power supply.

Click the image to open in full size.Click the image to open in full size.

Still I have to find some really low noise 1 kVA toroid. Any suggestion?
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Old 16th September 2009, 07:21 PM   #27
osscar is offline osscar  Latvia
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When I built my Leach amp I am using transformer from this supplier, mine is smaller - just about 11Kg and diam. 20cm and 800VA. You should ask bigger
they call it - Audio transformer....shielded and silent


But it will not be cheap....

here is picture of mine...
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File Type: jpg DSC00696.JPG (370.8 KB, 330 views)
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Last edited by osscar; 16th September 2009 at 07:47 PM. Reason: added more pictures
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Old 16th September 2009, 07:58 PM   #28
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Thanks, it looks very promising.

I also found something like low noise transformer by Plitron. I have to check more.

Click the image to open in full size.
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Old 11th October 2009, 11:45 AM   #29
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Default Maximus Soft Start

Lately some experimenting was performed on soft start circuit for Maximus amplifier. I made quite some tests with triac as power switch and phase control soft start but there was just too much power harmonics interferences when triac is completely on. So I returned to good old relay switch to softly turn on massive 2 kVA power supply. I also employed external 12 V trigger signal to turn on amplifier remotely. The result is something like schematics below.

Last edited by Lazy Cat; 11th October 2009 at 12:13 PM.
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Old 11th October 2009, 12:21 PM   #30
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Default Maximus Soft Start

Here's promised soft start schematics:
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