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Old 30th November 2011, 07:53 AM   #1441
clm811 is offline clm811  United States
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Thanks Andrew, Bob.

I figured since the Zeners were there to limit the voltage to 40vdc, that a regulator would be better, and would be easy to insert. Alternative?

Boards are the 6 transistor version, and I wonder, how low can you go with VCC/VSS before you need to start changing component values? Is 52VDC useable for this circuit (what about 50vdc)?
My transformer is one of a pair, I planned to use one per PCB, if possible.

-Chas
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Old 30th November 2011, 10:33 AM   #1442
AndrewT is offline AndrewT  Scotland
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The Zeners are not there to limit the voltage to 40Vdc.

Download Leach's papers on the Lo Tim and read what he says about the design in general, each stage in detail and includes a useful build guide.
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Old 30th November 2011, 11:28 AM   #1443
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Your transformers will give you 56V. That's a good operating point. When you understand how the VAS and output stages work you'll see why the VAS needs to operate in the vicinity of the output rails.

Front end regulation is an interesting exercise, but providing the required raw voltages can be a challenge with an uncertain benefit. Why not try your amps without regulation, but leave room for regulators and their PSU. You may well find that your Leach amps leave little to be desired.
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Old 30th March 2012, 07:04 PM   #1444
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Default About some components..

Hello forum,

It been a very long time that i had bought the 10 version transistor - Leach Amplifier from Jens / Delta Audio (that time).

Now i try to get the components for the amplifier as on the pdf manual.

Since now i choose metal film Beayschlag Resistors (both for 0.6 and 1W) and Nichicon KZ & ES for the electrolytic capacitors.

Now i'm searching about the emmiter resistors 0R47/5W and i would like to ask if someone have any experience of Mills MRA-5 and Ohmite Audio Series ?

Any other suggestion for those resistors?

Thanks a lot!

Regards.


P.S. Because i was now following the subject for years, is there any change at the components list for the 10 transistor version ?
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Old 30th March 2012, 10:32 PM   #1445
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Mot on/off
I used the Mills resistors in my first set of Leach boards and was extremely pleased with them. I am not overly critical of components if they in some way work.
My set of Leach amps is better than any commercial offering I have ever owned. You will be extremely pleased with the outcome. Be very careful dialing in the the pots on each leg of each channel and the bass will just come alive.
I have several sets of these boards up and running and a pair of twelve output boards which have not made it yet.

Shop wisely for components and you can get some very good deals. I chose to use the Rifa film caps in my amp and like them very much. I could not fit the Dale resistors in the holes on the board and used whatever Mouser had in that range.

Build a very robust power supply and it will serve you for many many years.

Tad
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Old 31st March 2012, 08:27 AM   #1446
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Thanks a lot for you help, hits & tips!

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Old 3rd August 2012, 03:22 AM   #1447
Junie is offline Junie  Philippines
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Hi, does anyone have spare boards for sale?
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Old 4th August 2012, 11:12 PM   #1448
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I have two boards for sale. if you are interested, please contact me at ipolykov at pacbell.net.

Thanks,
Igor
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Old 4th August 2012, 11:53 PM   #1449
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I sold almost two hundred of these boards. Has anyone built one yet? Did they get the protection circuit figured out?
The ten transistor amps turned out flawlessly I cannot figure out why the twelve device amp did not respond as well. I have yet to get one up and running. Please let me know how any of yours turned out.
Tad
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Old 5th August 2012, 12:01 AM   #1450
AJT is offline AJT  Philippines
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Quote:
Originally Posted by tryonziess View Post
I sold almost two hundred of these boards. Has anyone built one yet? Did they get the protection circuit figured out?
The ten transistor amps turned out flawlessly I cannot figure out why the twelve device amp did not respond as well. I have yet to get one up and running. Please let me know how any of yours turned out.
Tad
hey Tad,

after all the discussions about the merit of routing the feedback path to make it shorter......what was the issue about?

i am in the process of building still, very very slowly as i am deep into tubes right now...
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