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Old 11th September 2007, 01:38 PM   #51
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Quote:
Originally posted by tryonziess
How much power would be necessary to just run the input stage.
The smallest 40VCT would do, bet you a dollar i can find surplus PCB mount versions for 5 bucks/pc in 5 minutes.

Second option is placing the secondaries of a small low voltage transformer in series with the secondaries of the big donut and regulate the front end output voltage.
The latter approach has been used by Elektor mag a couple of times. PCB layouts for transformer and diodes of those designs can be found on the web.
(better to use the main fuse or protection gear, the front end needs to be switched off rapido if something happens to the output stage)
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Old 11th September 2007, 01:54 PM   #52
hags is offline hags  United States
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Default Re: Jens Rasmussen Leach clone group buy

Quote:
Originally posted by tryonziess
I emailed Jens the other night to see if he had any objections to a group buy of his leach design. It was o.k. with him. Now would there be any interest out there for this project. There are several versions, ie, the 10 transistor and 6 transistor version. I am currently waiting delivery of my AAK symasym boards to build. I would like a project waiting when i finish them. Let me know of any interest in the Leach clone project. The board i am talking about can be seen at www.deltaaudio.com

I think this is turning into more than just a group buy of an established design. If we have qoutes for the 10 transistor version as stated in the original post then let's order them, if not I don't feel like playing around.
If people are going to play around with the design, changing this, adding that, deleting this, and they don't resemble the boards here http://delta-audio.com/Leach-Clone.htm I'm simply not interested.
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Old 11th September 2007, 03:56 PM   #53
AndrewT is offline AndrewT  Scotland
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Jens' layout already has separated power supplies for the voltage amp and the driver+ output stage.

The front end of mine takes about 30mA.
The peak current into the drivers can approach 500mA, so it would make sense to power these from the output stage exactly as Jens' has done.

The front end can be derived from the main supply AC by adding a small 9+9Vac transformer to the big 40+40Vac and then smoothing & regulating. Alternatively 12Vdc can be added to the 58Vdc supply after the rail fuses and then regulated. This ensures that both the low current and high current supplies go down together.
The Leach voltage amp in my assembly has never been damaged throughout any of my stupid testing errors when I have inserted the drivers swapped PNP for NPN and shorted out the drivers and swapped +ve supply for -ve supply (no damage due to using the lightbulb which was bright while I ). The VAS protection as designed by Leach seems to work and also holds the output at near zero offset even with the drivers blown and rail fuses blown.
The one to avoid is the small fuses in the voltage stage. If only one of these blows then there is a more significant offset at the output. A CCS with shunt regulator would solve this completely for the front end supply. This gives short circuit protection and regulated supply and low HF noise and avoids the need for fuses and keeps the front end running when all else has shut down.
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Old 11th September 2007, 04:46 PM   #54
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Default Re: Re: Jens Rasmussen Leach clone group buy

Quote:
Originally posted by hags

I think this is turning into more than just a group buy of an established design. If we have qoutes for the 10 transistor version as stated in the original post then let's order them, if not I don't feel like playing around.
If people are going to play around with the design, changing this, adding that, deleting this, and they don't resemble the boards here http://delta-audio.com/Leach-Clone.htm I'm simply not interested.

hags,

please keep your cool. and remember though, that this is a DIY community and not a one man's decision and likes. there are reasons why these improvements were suggested. if there are discussion with potential improvements, i would gladly lend my ears and time. that's how we "learn" here.

please do not get me wrong, i am with you. i prefer that the original board will be carried over. but we should not overlook potential improvements. and since there is no final decision yet, just hold you breath and be cool...

time to get back to the GB...
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Old 11th September 2007, 05:29 PM   #55
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I don't think these are going to work for what I want to use them for. So nevermind about the 6 boards.
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Old 11th September 2007, 05:31 PM   #56
hags is offline hags  United States
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Default Re: Re: Re: Jens Rasmussen Leach clone group buy

Quote:
Originally posted by soltari_knight



hags,

please keep your cool. and remember though, that this is a DIY community and not a one man's decision and likes. there are reasons why these improvements were suggested. if there are discussion with potential improvements, i would gladly lend my ears and time. that's how we "learn" here.

please do not get me wrong, i am with you. i prefer that the original board will be carried over. but we should not overlook potential improvements. and since there is no final decision yet, just hold you breath and be cool...

time to get back to the GB...
I'm cool, but, this was a group buy for an existing design and board. There are other forums for discussions on what should and shouldn't be done to this design. That was my point.
If we are purchasing the boards as shown and designed on http://delta-audio.com/Leach-Clone.htm then I'm in.
That's why I'm interested, I'm not interested in a discussion on or purchase of a redesign.
Things can and usually do get way out of hand and turn into something else entirely when going down this road.
I'm eager to build this amp, not talk about what I'd like to do to the circuit.
Let's keep it simple and straight forward. That's why I seconded the idea of contacting a production house that has already made boards of this design. Let's be consistent and stick to what works with predictable results, at least with regard to a "group buy".
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Old 11th September 2007, 05:53 PM   #57
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Default This group buy

When I started this thread I originally wanted to gauge interest in the board. I am quite happy with the original layout that Jens designed and am not quite experienced enough to change it.
I have another quote coming from a Advanced circuits for the original 10 transistor version. I am probably going to order 75 boards and pay in advance. Then if anyone wants the board this way feel free to purchase them at my cost plus shipping. The quote as it stands is for .090 board, 3 oz. copper, green color, with silkscreen, and soldermask, with standard pad finish.
ANDREW You currently have a working Jens board I presume from your comments. How does it sound, are there any unusal oscilations or bad habits. Also, would it be possible to provide a complete separate power supply to the front end transformer, regs, caps totally independent of the output section. I am new to this so be patient with my questions. Learning by doing and asking.

Now anyone with a good source on output transitors for a 40 to 60 device project do not be shy and hold back. This project is going to destroy my priorities. How nice it is. Thanks for everyones input Tad
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Old 11th September 2007, 06:17 PM   #58
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Hello,

IMHO someone should take control and provide an offer, either of the original board from the first GB or on an updated version.....

Mind you, there is a lot of work getting a layout to come together and then the thing needs to be tested....

A seperated input and output stage holds some benefits, but I like to keep things tight in my layouts, so I always prefered the single board layout for the 6 and 10 transistor versions.

I don't really think the size of heatsink is a problem, all you need is a 30 cm long HS. IMO you will need a HS this size anyway if you want to use the full potential of the amp..

Happy GB!
\Jens
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Old 11th September 2007, 06:22 PM   #59
AndrewT is offline AndrewT  Scotland
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Hi,
if you go for the 5pair (10 output Q) then ensure you have the version that takes the NFB feed from the speaker output end and NOT from the nearest end of the output trace.

Jens,
it's not so much the length of the heatsink it's the height that is large (~130mm). Where most would choose 75 to 100mm high to fit a low height case 2u to 3u. But I think this needs a 5u case.
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Old 11th September 2007, 06:46 PM   #60
farl is offline farl  United Arab Emirates
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Default Re: Re: Re: Re: Jens Rasmussen Leach clone group buy

Quote:
Originally posted by hags


I'm cool, but, this was a group buy for an existing design and board. There are other forums for discussions on what should and shouldn't be done to this design. That was my point.
If we are purchasing the boards as shown and designed on http://delta-audio.com/Leach-Clone.htm then I'm in.
That's why I'm interested, I'm not interested in a discussion on or purchase of a redesign.
Things can and usually do get way out of hand and turn into something else entirely when going down this road.
I'm eager to build this amp, not talk about what I'd like to do to the circuit.
Let's keep it simple and straight forward. That's why I seconded the idea of contacting a production house that has already made boards of this design. Let's be consistent and stick to what works with predictable results, at least with regard to a "group buy".
I agree.... and in fact the title of this forum is "Jens Rasmussen Leach clone group buy".
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