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Old 15th October 2005, 07:04 AM   #1
Tyimo is offline Tyimo  Hungary
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Default Which SE-ECL82 amp to build?

Hi!
I was looking for a nice and simple SE amp with one ECL82 per side and found two attractive circuits.
I would like ask the experts about these designs:
-are they operate in Class A?
-has any negative fead back in the circuits?
-which one is better? :-)


Thanks and greets:

Tyimo
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Old 15th October 2005, 07:09 AM   #2
Tyimo is offline Tyimo  Hungary
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Here is the another competitor!

Note. Power supply removed from schema -- to dangerous to contemplate
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Old 15th October 2005, 07:41 AM   #3
PRR is offline PRR  United States
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> -are they operate in Class A?

Yes, obviously.

> -has any negative fead back in the circuits?

No. (I won't count the cathode resistor in the first one.)

> -which one is better? :-)

They are essentially THE SAME. Draw them both in the same style: very minor differences.

One BIG difference: #1 does not show a power supply, #2 does, and the #2 power supply as drawn is a death trap!!! It shows one side of the wall-power line connected to chassis. There no indication which side is utility-ground. It is uncertain which wall-socket pin is grounded (60% of my kitchen outlets had black and white reversed). The chassis is exposed to the users at the input connector, which makes the whole hi-fi system "electrically HOT". It can kill you or your children. And as drawn, turning the power switch Off ensures that the chassis will be "hot". Do not build that power supply as shown!!!
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Old 15th October 2005, 08:44 AM   #4
Giaime is offline Giaime  Italy
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Please moderators, remove that awfully dangerous schematic, as PRR said.
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Old 15th October 2005, 01:35 PM   #5
Tyimo is offline Tyimo  Hungary
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And here is the first one's PSU:
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Old 15th October 2005, 05:04 PM   #6
Giaime is offline Giaime  Italy
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Quote:
Originally posted by Tyimo
Giaime: here is a corrected schem.
That is always no-good, the B+ runs directly from the mains. You should use an isolation trasformer between the diode and the mains, to mantain safety rules. And also a half wave rectifier is no good. Try to redesign the PSU using PSUDesigner.
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Old 15th October 2005, 06:37 PM   #7
kevinkr is offline kevinkr  United States
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I think I would just build the more recent of the two circuits, supply decoupling looks to be marginally better in the newer design.

If you do build the earlier one do get a power transformer with about a 180-200V secondary as well as a filament winding. You can use a bridge rectifier, bear in mind the original halfwave rectifier would have dropped significantly more voltage than a full wave bridge.

The old power supply design as previously stated is extremely hazardous to put it mildly.

Kevin
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Old 15th October 2005, 08:47 PM   #8
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How about Morse's Gnat?

Pics of my 6BM8 - The Gnat....

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Old 15th October 2005, 10:18 PM   #9
Zen Mod is offline Zen Mod  Serbia
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search for "Aleksandar Kitic" in this forum.
LH84 (if I remember OK ) looks promising
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Old 16th October 2005, 05:52 AM   #10
Tyimo is offline Tyimo  Hungary
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Hi!

Quote:
the B+ runs directly from the mains
Giaime! Yes, you are right! I looked only the main-audio circuit section and not the whole circuit with the PSU... That PSU design was realy a "deadly joke" Thanks for the moderators that removed it from the schematic!

Kevin: Thanks! Which one do you mean: the Noel82, with coloured schem ? I would anyway build a better PSU for this amp.

Greets:

Tyimo
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