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Old 15th February 2001, 08:03 AM   #1
jteef is offline jteef  United States
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I just started building the leach amp today, (it will probably help a lot having the man who designed it right across the hall) I am pretty optimistic and have heard nothing but good things about this amp. This is my first experience with hi-fi home audio...I have been mainly focused in the 12V stuff until now.

Anyways, My main question is:

If I were to walk into a hi fi audio store, what sorts of products would be comparable to this amplifier in terms of sound quality/power/etc.

Question #2

After this is done, I am going to need a good pre-amp. Can somebody suggest a good DIY pre-amp?

Question #3

I would like to put an IR remote section in my amp so that it turns off with the rest of my stuff...i.e. cd player...preamp...etc. Where can i go to find what the standards are (if any) I've got a couple old TV's that I might scrap for the remote section. But if that doesn't work out, what will I need to do to get something working if I use one of the cheap universal remotes you can buy at wal-mart, or in the future, one of the fancy touch screen jobs.

Thanks!

jt
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Old 16th February 2001, 12:06 AM   #2
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Regarding pre-amp, when Leach originally published the Low TIM series he followed it with "Build a Wide Bandwidth Pre-amplifier"

I built a number of this combination back in the 70s and they work quite well.
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Old 17th February 2001, 06:34 AM   #3
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OK i'm interested Would you happen to know if that article or the schematic is online somewhere?
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Old 17th February 2001, 10:35 PM   #4
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The article was published in 1977 (god I'm getting old).

Oddly it is not on the Leach Website. I have sent him an e-mail asking & will reply in due course.

My scanner is broken. If I get a chance at work I will scan the article into a PDF file.

"jteef" should (being across the hall) be able to answer this pretty quickly ...... and why was he asking us anyway, surely you would ask the designer first ..... how odd :-)

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Old 18th February 2001, 12:20 AM   #5
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Scanner fixed.

WML - FET tone Control Circuit.PDF file (500k). The PCB is a scan of the actual board, so you will have to do some artwork.

Haven't included the RIAA pre-amp bit.

E-mail me if you want it: mailto:mark.finnis@adelaide.edu.au
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Old 19th February 2001, 03:29 AM   #6
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Mail is on the way! Tnx man
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Old 19th February 2001, 07:10 PM   #7
jteef is offline jteef  United States
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hehe, I posted here, because i mainly wanted question #1 answered, and asking the designer of a rival is not usually the best source for information...even if it is free.

I was not aware that he had designed a preamp, but I have since asked him about it and still waiting for a reply...I'll be in on wednesday to finish soldering the boards and i'll try to ask in person then.

and I asked him at the beginning of the semester about the remote, and didn't get much of an answer. I am still pretty interested in this and if anybody has any info on where i can go to find out how to accomplish it, that'd be great. Ideally, i'd like to be able to use the remote from my home theater receiver or an aftermarket remote and be able to turn the power on the amp off.

thanks

jteef
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Old 21st February 2001, 06:48 PM   #8
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Default toroids

If haven't bought your transformer yet check out the 88volt 4.5 amp torroids for $20 plus $5 shipping at allelectronics.com they are listed under power transformers. It may be on the light side for 2 channels, but if you are building mono block style it is a great deal. I just bought 2, I'll probably take a few windings off the secondary to drop the rails down to 59-61 volts.

Wade
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Old 28th March 2001, 07:59 PM   #9
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I've been building Leach's amplifier since the 70s and am currently updating my beloved old boatanchor to ver 4.5,
with an eye toward Self's and Sloan's books on the subject.
The old driver boards will be fodder for some Evil Experiments with current sources and Sziklai output configurations.

Leach built several preamp designs over the years, including one with a JFET input and I have notes and circuit boards in various
states of non-completion . I never got around to building
a serious preamp partly because I couldn't come up with a
chassis design that didn't look awful! That and I found a
Hafler SE-100 (all-JFET design) for a good price, and that
pretty much settled it. I had to mess with that one, too,
installing a Jung regulator supply.

While I'm pretty firmly in the objectivist/gotta measure it camp, I have started a tube amp project, which is stalled for lack of money, output transformers and a design. Hopefully as time goes by, I'll have acquired a better perspective on the solid state vs tube debate, or maybe not;
I generally have no problem just enjoying the music!

I'd be pleased to hear from others on the subjects, and can offer moral and some technical support.
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Old 29th March 2001, 02:27 AM   #10
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Damon,
Evil Experiments, huh? You sound like a man after my own heart. Why let well enough alone, when you can tilt at windmills and generally annoy the neighbors? (or at least their pesky dog...)
Okay...regarding tubes...what are your intentions? Would you use such an amp full-range, or as part of a bi/tri-amp system? How much power are you considering?
If you've read the other threads, here, you may have noticed that tube-folks are comparatively scarce at this site. For the reason why, note the reception that I got in the Great Mother Of All Debates (aka Slone Opti-MOS thread). You have to be pretty thick-skinned to endure that much abuse. Most people just pack their bags and go elsewhere. N.B.: As I state somewhere in that thread, I like both solid state and tubes, so I'm content to talk about either.
You said you were stalled for a design. Like any amp project, work backwards. Fiddle with the questions I advanced above and we'll see if there's a schematic that can be dredged up that will fit the bill.

Grey
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