Nice Leach Amp or Super Amp

[Mikett]

http://xoops.govern.com.tw/modules/n...php?storyid=19

Can anyone translate?

[rodolfo]

ho yeahhhhhh
wonderfull
magnifico

[Upupa Epops]

Wonderfull ? With this long wires ?

[amplifierguru]

Exactly. Unfortunately so many potentially good designs never even come close to their full potential due to poor lead dress or PCB layout.

I can recall my time with one famous amplifier manufacturer where their resident engineer had just rearranged an old design (someone else's) by rearranging the PCB layout and trying new power transistors. When he fired it up the THD was around 0.3% some 10 times the old design. As he was scratching his head, I looked over the board and glaring back was the Vas output track weaving to the front end and encircling the input transistors. Cut this I said and run a jumper away from there. He did that and the THD dropped two scales.

And the punch line "Does layout matter!" he said. I kid you not. Top designer for the company!

A black art?

[jacco vermeulen]

Very strange !
The Leach main boards look very neatly built up.
Obviously the person who built it had the patience to place the components very carefully on the boards, unlike pictures of other Leach amplifiers shown on this forum.
The Leach boards seem to be gold plated, and have a silk print and solder mask.
The 62vac toroid must be an expensive one, the Rifa 169 capacitors used are too.
Yet, making a couple of output boards was not an option, dispite already making the main pcb's.

I really do not understand that some think this is beautifull.
For 25 years the experts say it is best to avoid signal wiring in amplifiers, and achieve superior performance.
2005, and still people do Pasta amplifiers, incredible !

[still4given]

Originally posted by jacco vermeulen
Very strange !
The Leach main boards look very neatly built up.
Obviously the person who built it had the patience to place the components very carefully on the boards, unlike pictures of other Leach amplifiers shown on this forum.
The Leach boards seem to be gold plated, and have a silk print and solder mask.
The 62vac toroid must be an expensive one, the Rifa 169 capacitors used are too.
Yet, making a couple of output boards was not an option, dispite already making the main pcb's.

I really do not understand that some think this is beautifull.
For 25 years the experts say it is best to avoid signal wiring in amplifiers, and achieve superior performance.
2005, and still people do Pasta amplifiers, incredible !

Hi jacco,

A question from someone who is trying hard to learn, is it better to run signal through PCB traces than through heavy stranded wire? For some reason it just doesn't seem that any kind of current would prefer traveling through a PCB trace than through a quality stranded wire. Please help me understand this. Obviously a PCB looks tidier but does it really flow current better?

Thanks again, Terry

[Upupa Epops]

Hi Terry, problem is in inductance of these wires, not in resistance. The same amp can oscilate ( if is made with long wires ) easyly, than with short wires and this oscilation are often hard eliminated.

[Mikett]

if you surf some of these asian sites, you'll see that there are some really nice pcbs available and they are quite inexpensive. Lots of HV power supply regulators and a bunch of DACs. If anyone noticed, his chassis was stainless steel to boot and he even had the TO3 covers that matched his heatsinks. Some of their kits contain premium parts.

[EJ]

It's a Super Leach. Here is the translation for you guys. I'm just translating. I didn't build this.

================================================== =======
Before you proceed with this project, I strongly suggest studying the articles written by Dr. Leach thoroughly. Many important ideas are explained inside. It took me about three months to read them through.

Preparing materials:
1. PCB: ....(some kind of group buy in Taiwan).... The layout is correct. Just follow the silk print.
2. Transformer: Purchased from .....(some web site in Taiwan)..... The first one cost me 5000 TWD (eq to 150USD). There was a group buy for transformers of the same spec. The price was only half as much but the size was smaller than mine.
3. Transistors: ...........(where to find them in Taiwan)
4. Resistors: I used philips 0.1% resistors just for my vanity. ....... (the price)....
5. Capacitors: ...(where to find them in Taiwan)....
6. Heatsinks: ...(where to find them in Taiwan)....
7. Chasis: Made of stainless steel....(where to machine them in Taiwan)....


Fig1. the transformer


Fig2. the pcb after assembling


Fig3. Testing according to the instructions of Dr. Leach


Fig4. Mounting the heatsinks to the chasis


Fig5. Viewed from outside the chasis. The thermal compensation diodes are installed on the small pcb. I made some cover plates to keep myself from being electrified by the 86V power transitors. You can see the cover plates on the right side.


Fig6. Adjusting quiescent current

Summary:
This Super Leach Amp project took me about 1 year, from collecting parts to complete. ......(how it sounds)....... I still haven't built the front plate so there is no final picture. ....(asking if anyone knows where to machine the front plate in Taiwan).......

If you have any questions, I will gladly share my experiences learned during the project with you.

Thanks!

E-mail: yjhuang@ma.ks.edu.tw

[still4given]

Originally posted by Upupa Epops
Hi Terry, problem is in inductance of these wires, not in resistance. The same amp can oscilate ( if is made with long wires ) easyly, than with short wires and this oscilation are often hard eliminated.

OK, so is it the length of the wires that is the problem, not so much the fact that wires are used? If output PCB's are used, wouldn't there still be some wires involved? Is there a way to lower inductance in wiring? Is there no inductance problems with PCB's?

Thanks, Terry