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-   -   Help with 8 channel Leach Amp Power Supply (http://www.diyaudio.com/forums/power-supplies/146541-help-8-channel-leach-amp-power-supply.html)

bowdown 26th June 2009 12:29 PM

Help with 8 channel Leach Amp Power Supply
 
Hi guys,

I am currently building an 8 channel Leach amp, I would like to know the best and safest way to connect all 8 channels to the power supply. I am using a Toroidal transformer which has the following secondary outputs (45-0-45 & 45-0-45), there is a total of 8 wires on the secondary side. How would be the best way to connect the 8 channels so as to avoid getting any hum,but also keeping things safe.
Any info would be great.


Cheers

Bowdown

pacificblue 29th June 2009 12:07 PM

8 amplifier channels, two center-tapped secondaries and no hum. That is asking a lot.

The best solution for the transformer would be to feed 4 amplifiers off each secondary. The best solution against hum would probably be to connect the secondaries in parallel on the shortest possible path. In both cases the amplifier supply leads should be connected in a star topology with the leads as short and as thick as possible and all of the same length.
The parallel secondaries solution has a drawback in that it requires more attention to the current rating of the power supply wiring/fusing.

alfredrofe 2nd July 2009 01:38 PM

Re: Help with 8 channel Leach Amp Power Supply
 
Quote:

Originally posted by bowdown
Hi guys,

I am currently building an 8 channel Leach amp, I would like to know the best and safest way to connect all 8 channels to the power supply. I am using a Toroidal transformer which has the following secondary outputs (45-0-45 & 45-0-45), there is a total of 8 wires on the secondary side. How would be the best way to connect the 8 channels so as to avoid getting any hum,but also keeping things safe.
Any info would be great.
Cheers
Bowdown

Hello Bowdown,
I don't know how long you have been attending this forum, but your request is devoid of sufficent information to even start to assist you. Two fact and no details to work with, you either expect us to be mind readers, or sitting next to you. I am neither.
If you want help we need a detailed description of your vision, and how far you have progressed towards it.
I have some 2.5 years experience with the Leach 4.5 origional and none with the clone which has more easily obtainable transistors.
I have some 3 years experience making PSUs and winding transformers. Your description of the transformer would indicate it is not an off the shelf model, and your question indicates no experience in making psu's.
Perhaps if you detail your plan, and detail what you have to date, we can help you. I see from another thread you want to make a surround sound system, is that what you intend to do here??????
Alfred

bowdown 2nd July 2009 02:05 PM

Hey Alfred,

My bad.. The amps are Leach v4.5 running on approximately +/- 63V, I already have the mentioned Toroid, It was wound by a company in the eastern states. As it is a 2Kva Toroid, the company said that they will not wind 2 secondaries, they insisted on having 4 secondaries. I too have made a few Leach 4.5's and also the Super Leach with no hassles, only difference was that they were 2ch. I just wanted to get peoples opinion on the best way to ground it, without causing hum or safety issues. Yes it will be used in a Home theatre setup running fronts,rears,front center and rear center. The other 2 channels are still optional, they will be for an "out door" zone which will be done at a later stage. I have every single thing here for the amps(Transistors,caps,resistors,diodes,pcb's,wirin g,connectors..and all the miscelleneous component like screws), the case is currently being built...altho I know the layout of the heat sink fins could be better, but I dont want to get them machined in half and reorientate them. I did build a super amp and also a Leach 4.5 with the same heatsink setup (But shorter length, 350mm for the 4.5 and 400mm for the super amp) They have both been working for just over 5 yrs now for the super amp and just over 3.5yrs for the 4.5. They run barely warm. I just thought I'd build a 6 or 8 channel amp instead of multiple 2 channel amps..Any way let me know if there is any more info you want.

Cheers

Bowdown

alfredrofe 6th July 2009 03:57 AM

It would seem you are committed for this project, if you had done a little more research you may have gone down a different path.
The obvious solution to your grounding is to use a star ground which is mentioned in the Leach notes. Instead of having one secondary you have two, very simple. Divide your two sec between the amps you want to serve.
A rather simplistic approarch you have taken which will compromise the High Fidelity most of us seek. I can see why others have not come to your aid, the results will be poor running speaker leads of varying lenghts all over the place. The Leach amp itself does not perform as well as a modified Blamless, see other threads on this forum, SCULD and Thermal trak, for PSU see the Robert Cordell thread and see why you path is less than Hi-Fi, as I said in my first post, describe what you want to achieve, so far you have not, it seem you are not willing to reveal your quest in any detail, from what you have said you are aspiring to the antithises of what I aspire to Hi-Fi, I cannot help you any further.
Alfred

bowdown 6th July 2009 05:26 AM

Hey Alfred,

Thanx for your post any ways. Im not sure what you want me to describe, All I want to build is a decent 6-8ch amp, 150 - 200 watts per channel @ 8 Ohms (Doesnt have to be with all channels driven). I have my 2ch Amp for Music that I am already happy with. Thanx for trying to help tho, I do appreciate your responses.

Cheers

Bowdown

Tequilataz 26th July 2009 10:12 PM

I don't know if this will help, But I've built 2 4 channel Leach Superamps. One for my SUV and one for the home. On both amps I only used one transformer in the power supplies. In the car amp were the switching power supply frequency is around 28K
I used banks of 2 x 35,000 uf capacitors and in the home amp I used a 2 x 100,000 uf bank of capacitors. Neither one has any hum and Ive had many experienced listeners say that it is the best sounding system they have ever heard, So the fidelity did not suffer. Both of the transformers I used (I wound the high frequency toroid myself) were well over 2KVA each. The home transformer weighs 40 lbs. ISince mine came out great I don't see why yours would be any different. Good Luck

bowdown 29th July 2009 12:41 AM

Hey Tequilataz,

Thanx for the motivation, glad that your projects went well. mine is still a while off as I work away most of the time and can only get a few days a month to work on it. I was actually looking at building one for the car as well after this is done. Anything that I need to be aware of? Is it possible for you to post some pics of your finished projects, as its always nice to see what others have created.


cheers

Bowdown


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