pics of my leach amp - just finished

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BrianGT

BrianGT

Retired diyAudio Moderator
Joined 2002
chipamp.com
#1
This is my first amplifier project. It came out good, and sounds quite good. Here are some pictures: tell me what you think

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I used the 4.5 boards I obtained from prof. leach.

--
Brian Bell
gte619j@prism.gatech.edu
 
#3
I am currently using a Denon dolby digital processor that I got a few years ago for my denon av amplifier. It just allows 3 sources (2 fiber optic/coaxial) and one external source) and it has a volume control. No gain. It works for now, but I would like to build a pre-amp. I am considering building the Leach pre-amp, if I can find any way to obtain/make circuit boards. I am also looking for other pre-amps to build also.

I have larger versions of the pictures, but I didn't want to slow down the forum too much.

I got the transformer from victoria magnetics:
http://www.victoriamagnetics.com/leach_amp.html

I had John, the guy in charge, make it with an extra shield around it. He also set me up with the case. The case is from Smart Devices. They make this amplifier:

http://www.smartdev.com/2x150vt.html

I had them sell me the case and connectors from their amplifier. They called it the "Leach Amp Chassis Kit" and can put together more if needed. The case is similar to the Hafler case from the late 70s.

Any suggestions for a pre-amp would be appreciated.

--
Brian
gte619j@prism.gatech.edu
 
#5
Very Nice

Great job! the chassis looks like a great one for small Class A amps. Very pictures. Notice the bleeder resistors Grey, and I swear they won't hurt the sound ( except maybe the sound of swearing when someone sticks screwdriver across a charged cap)

H.H.
 
#6
Brian,
Your amp looks outstanding. Great job. I particularly like your case and your construction is tidy. Would you elaborate on how it sounds - have you compared it with any commercial amps?
BAM
PS I would like to get hold of a couple of these cases to build a couple of class A monoblocks. Do you have an email contact at smartdev?
 
#7
I put 9.2k 2W resistors for the bleeder resistors. They take at least 10 minutes to discharge the 22,000uF caps. I tried it without them also, and I heard no noticable difference.

My favorite part of the case is that I can unscrew the heatsinks from the chassis bottom and fold them flat, which allows for easy working on the boards.

I will eventually post more pictures. I really enjoyed building the amplifier. It took me 3 weeks total, from the first day I went in Leach's office to buy some circuit boards. He is a really nice guy and answered any question that I had along the way. I only had one problem building the amplifier... when I initially made the boards, for the 1/2 W resistors in the output stage R41-R44I accidently used 10k resistors instead of 10 ohm resistors. This still allowed the circuit to work, but I was getting no biasing current. I was really confused and I took it to Prof. Leach, and he spotted the problem in a few minutes.

--
Brian
 
#10
I paid $208 for the chassis, with 2 heatsinks, the bottom, the top, and all of the connectors on the back and the power switch. (connectors being 2 alps audio pots, 3 fuse holders, gold plated input and output jacks, high quality)

I am going to see them next week, and I will see if we can get the price lower by leaving out some connectors. I will keep you posted.

Their info is:

Smart Devices
Gwen Sawyer
General / Sales Manager
gwen@smartdev.com


I like the case a lot, even though it was expensive, it is great quality, and I think it was worth it. I priced out buying a case, heatsinks and connectors, and it came to about $140 for the case that I wanted, and I would still have to drill the heatsinks. This case has all pre-drilled heatsinks, and they have space for 6 to3s per side, which the leach amp uses 4 per side. I think it was worth $208, and I plan on having it for a long time.
If you can find an old hafler case.. it might be as good. I like that this case also had mounting points for the transformer and capacitors. It is made for a transformer similar to the Victoria Magnetics Leach Amp transformer (80V 6A).

The amplifier sounds great, with no noticable distortion. I am taking it into Prof. Leach's audio lab to hook up to the machine that measures amplifier distortion next week, and I will post the results.

--
Brian
 
#11
by the way.. the white stuff on the inside of the heatsinks is from the glue that I used to put around the thermal diodes connected to the heatsinks. I have pictures of how I wired the power transistors and thermal diodes, and I can post them if anyone is interested

--
Brian
 
#13
I just received an email from Norm Schneider:
"Thank you for your inquiry. The cases used by the Georgia Tech students to complete their engineering courses are not in our product line. We sell these to students as a special favor. They are the mechanical parts we build to use in our $2250 2X150 audiophile amplifier. All switches, terminals, heat sinks, rubber feet, and hardware are included in the kit. The output devices, PCB's, filer caps, and transformer are supplied by the students. We charge them $208 for these critical parts. The heatsinks are custom made for us by Wakefield. We buy 1000 at a time. The total surface of each heat sink is 364 square inches."

So looks like you need to make friends with a Georgia Tech student in order to get a kit.
 
#16
Nice!

I'm also searching for a pre-amp to go with my Leach 4.5 (not built yet) and found three designs that interest me. It looks like each one is of very high quality, with the proper components of course, and very inexpensive. I personally will not be adding the phono stage.

- A Low Distortion IC Preamplifier,
Audio Amateur, 1/79. You should be able to get back issues from www.audioXpress.com

- Self on Audio, by Douglas Self
ISBN #0 7506 4765 5
www.dself.demon.co.uk

- The Audiophile's Project Sourcebook, by G. Randy Slone
ISBN #0 07 137929 0
www.sealelectronics.com

The books are available at www.amazon.com

good luck
 
#20
After seeing this, I'm too ashamed to show my junk-box
special implementations of Leach's amplifiers. 🙁

I used to live near Atlanta. I'd love to work for this company.
I'd love to be working, period.

Ya'll excuse me while I go beat my head against something
solid. WAH!

Really, REALLY frustrated in Seattle....
 
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