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Old 11th February 2005, 08:55 AM   #1
beppe61 is offline beppe61  Italy
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Default Leach wide bandwidth preamp.

Dear Friends,

Is there someone who has built this preamp?
How is the quality of its line section ?
If a damage to the signal is done in the preamp then you can only amplify it.

Thank you all.

Regards,

beppe61
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Old 11th February 2005, 10:42 AM   #2
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Hello,

Are you refering to this one: http://users.ece.gatech.edu/~mleach/...b77article.pdf


If so, I've built it and it sounds very good....
It's actually a discrete opamp design so you can set
the gain as you want...
also check this: Leach opamp

Regards,

Udi.
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Old 11th February 2005, 11:07 AM   #3
beppe61 is offline beppe61  Italy
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Dear Udip,

Thank you very much indeed for your kind and valuable reply.
That is the one.
How do you rate is line section ?
I am not interested in LP listening anymore.
I am too lazy and clumsy for black disks.
What intrigues me is the fact that is made out just two BJT.
May be is becoming my obsession.
Which line preamp is possible from just two BJT.
I strongly think that is possible a lot indeed.

Any your suggestion, information and opinion would be greatly appreciated here.

Kind regards,

beppe61
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Old 11th February 2005, 11:37 AM   #4
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Quote:
Originally posted by beppe61

What intrigues me is the fact that is made out just two BJT.
May be is becoming my obsession.
Which line preamp is possible from just two BJT.
I strongly think that is possible a lot indeed.

Any your suggestion, information and opinion would be greatly appreciated here.


Hi again,

You were refering to the first one with the two BJT's line amp,
I actually built the FET version (look at page 10-11 in
the article) were both the MC preamp and line preamp are
the same (except for the feedback compoments) - they are
actually a discrete opamp so you can use it in any application
you want... and the sound is very good indeed..at least
I liked it...and also they are very quiet!
I haven't tried the two BJT's version so I can't tell you
how it sounds... but I guess it should be pretty good as a line amp with not too much gain...
If you decide to try the discrete opamp version, you can
check the thread I'v posted and modify it for +-15 supply.

Regards,

Udi.
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Old 11th February 2005, 03:13 PM   #5
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I bought the both Leach preamps, the line stage and power supply from Dr. Leach in the late 1970s. I bought them built to avoid the hassel of ordering and matching parts. Most parts houses had a minimum order amount, both quantity and price. One time I wanted 4 transistors and had to buy a bag of 25. I prefer the JFET version of the preamp and replaced most of the caps in it with polystyrene caps. The JFET preamp has a much higher slew rate and much lower input capacity than the BJT version. High inductance MM cartridges require low terminating capacity.
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Old 12th February 2005, 12:45 PM   #6
beppe61 is offline beppe61  Italy
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Dear Mr.Rayfutrell,

Thank you for your kind reply.
I would like very much to know your opinion about the sonic quality of the line section.

Kind regards,

beppe61
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Old 14th February 2005, 03:19 PM   #7
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I couldn't tell you.

I didn't use the line amp because the preamp provided enough output to drive my power amp. The line amp was just not needed, so I removed it. That was so long ago (20 years) I have no idea if it affected the sound.

Regards,
Ray
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Old 15th February 2005, 03:44 AM   #8
Mikett is offline Mikett  Canada
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I bulit both the BJT and FET versions. The line sections are a little veiled and certainly not as dynamic as compared to Walt Jung's AD744-811 design.

Unfortunately, I am comparing the Leach sections with a "Sulzer" type regulator versus Jung's high performance regulators on the 744-811 section.
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Old 15th February 2005, 07:45 AM   #9
beppe61 is offline beppe61  Italy
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Quote:
Originally posted by Mikett
I bulit both the BJT and FET versions. The line sections are a little veiled and certainly not as dynamic as compared to Walt Jung's AD744-811 design.

Unfortunately, I am comparing the Leach sections with a "Sulzer" type regulator versus Jung's high performance regulators on the 744-811 section.
Dear Mikett,

Thank you very much for your kind and valuable reply.
Could you please give me some more info on this Sulzer type regulator or some useful link ?
I intend to use 24V fixed voltage regulators or the 117-317 pair for the +/- 24V dual power supply.
I am very intrigued by the simplicity of this line stage (something called Sziklai pair I guess), just two BJTs, and the high voltage rails (for a preamp of course).
I am sure that this simple stage deserves a good power supply.

As soon as I will build it I will report.

Kind regards,

beppe61
Torino__ITALY
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Old 15th February 2005, 10:41 PM   #10
Mikett is offline Mikett  Canada
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Super Regulator, collecting the facts
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