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Old 14th November 2012, 11:53 AM   #7571
a.wayne is offline a.wayne  United States
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Quote:
Originally Posted by dvv View Post
I am now slowly wrapping up my power amp project, and have come to the last, but by no means the least section, the power supply.

I'd like to hear your comments on what I have in mind.

The first thing I am set on doing is slightly spreading arund the filter caps. So, instead of putting all power amp filters on one board, I intend to put 2 10,000 uF caps on their own board, but also a 4,700 uF cap (same model, same manufacturer) on the actual power amp board, followed by 100 uF and 0.1 uF caps. It seems to me it's practical to have it as near the output stage as possible. Views? Opinions? Experience?

The voltage gain stage will be fully regulated, as I have been doing since the early 80ies. The questions which now arise are:

1. Should these regulated lines also feed the predriver only, or predriver AND driver, leaving only the output section to run off capacior fed lines?

2. Or should I go for full voltage/current regulation of the power section as well, separately from what precedes it?

Remember, I am very flexible. It can be a single case stereo amp, or two separate monoblocks, meaning PCB real estate is very flexible.

I am not bound by any price constraints, this is for me and my pleasure, so cost is relatively unimportant.

I have a relative abundance of serious power devices (all by Motorola/ON Semi, MJ 21195/21196 TO-3 250W devices, MJL 3281/1302 plastic pack 200W devices), so there's no problem in using 2, 3 or 4 pairs of power devices, on a separate hefty heat sink.

So, I plan to use 3 or 4 pairs of output devices in the audio section, and it's not a problem to use exactly the same number and type of devices in the regulator, because remember, I do want it to be capable of some rather serious current peaks.

All ideas and views invited.
On top of what you plan to use , I would use one 4700 uf per output device and place them 20 -25mm away from the ouputs, CRC WITH full regulation for vas, obligatory soft start , leave out all sonic degrading protection BS limiters , use gold plated high grade fuses ...

Regards

Last edited by a.wayne; 14th November 2012 at 11:59 AM.
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Old 14th November 2012, 12:00 PM   #7572
dvv is offline dvv  Serbia
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Originally Posted by a.wayne View Post
I would use one 4700 uf per output device and place them 20 -25mm away from the ouputs...
So would I - if I had a room to dedicate to just this, Wayne.

Work it out yourself - that takes a lot of space, add a large power transformer, the basic capacitor block (4 10,000 uF caps), the not at all insignificant heat sinking I need to use and so forth, and it becomes overwhelming all too soon.
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Old 14th November 2012, 12:05 PM   #7573
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I agree with all of that ( fas42 + a w ) . It is also an economical way to do it ( a . w ) . Stability should be enhanced .

My own experiments also show to try under voltage to driver stage . You can have the option of optimum voltage also ( power out ) . Call it soft clip if you like . Do it on the scope , you will see what I mean . At clipping you should find less harmonics if driver stage clips first ( 1 V under will do ) . That way you get great book figures for power . Bet you anything the customers choose soft clip . I found it by accident . I was using my ears one day and the oscilloscope said my ears were right . I took so much trouble to build my clean high voltage supply , only to find I ran it as before or lower . Worth a thought ?
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Old 14th November 2012, 01:46 PM   #7574
a.wayne is offline a.wayne  United States
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Originally Posted by dvv View Post
So would I - if I had a room to dedicate to just this, Wayne.

Work it out yourself - that takes a lot of space, add a large power transformer, the basic capacitor block (4 10,000 uF caps), the not at all insignificant heat sinking I need to use and so forth, and it becomes overwhelming all too soon.
Err ok , so when you said this ....!!!

"Remember, I am very flexible. It can be a single case stereo amp, or two separate monoblocks, meaning PCB real estate is very flexible. I am not bound by any price constraints, this is for me and my pleasure, so cost is relatively unimportant."



What you really meant was .........
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Old 14th November 2012, 02:12 PM   #7575
dvv is offline dvv  Serbia
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Originally Posted by a.wayne View Post
Err ok , so when you said this ....!!!

"Remember, I am very flexible. It can be a single case stereo amp, or two separate monoblocks, meaning PCB real estate is very flexible. I am not bound by any price constraints, this is for me and my pleasure, so cost is relatively unimportant."



What you really meant was .........
... in terms of cost, not space. My room has only 12 m2 of area (about 109 sq. ft).

My fault, I wasn't specific enough, sorry.
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Old 14th November 2012, 02:42 PM   #7576
a.wayne is offline a.wayne  United States
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Put the speakers outside the amps in the room , life is too short for compromises

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Old 14th November 2012, 04:40 PM   #7577
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You guys sure complain a lot! '-) I use 9 output pairs and 100,000uF/channel for the JC-1.
Certainly you can afford to do 1/2 or 1/4 that effort, and put it in a reasonable space.
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Old 14th November 2012, 05:06 PM   #7578
dvv is offline dvv  Serbia
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You guys sure complain a lot! '-) I use 9 output pairs and 100,000uF/channel for the JC-1.
Certainly you can afford to do 1/2 or 1/4 that effort, and put it in a reasonable space.
Who's complaining?

John, the key difference between you and me in this case is that you have manufacturing capabilities, both via the Parasound company and as a private citizen, that I can only dream of.

Just to illustrate the point, it is not possible for me to obtain locally manufactured anodized aluminium plates. I have to import them from Slovenia, which is a hassle and a half, believe me. And, because of taxes and levies, does become quite expensive in the end. The best I can hope for is painted aluminium, and even that is of mediocre quality only. I am not particularly consoled that the paint is an ecological, water based imported Italian paint.

By pure blind luck, a friend of mine does aluminium shaping using his own CNC machine, and he spent 20 years making gyroscopes, so a deviation of one micrometer is enormous to him (in the aiming gear of a T84 tank, that deviation is the difference between hitting and missing the target).

Don't worry, I'll figure out a way with a little help from my friends, but it will never look like an industrial product because of lack of support of local manufacturing facilities.
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Old 14th November 2012, 05:10 PM   #7579
dvv is offline dvv  Serbia
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Originally Posted by john curl View Post
You guys sure complain a lot! '-) I use 9 output pairs and 100,000uF/channel for the JC-1.
Certainly you can afford to do 1/2 or 1/4 that effort, and put it in a reasonable space.
Sorry, I forgot.

As for the output stage, I plan on using 4 pairs of Motorola/ON Semi MJL 3281/1302 200W devices per channel. According to Data Sheet specs, at 85 deg. Centigrade, these four should still be capable of delivering 950 Watts of power, which I reckon is just about right for a nominally 100 Watts into 8 Ohms power amp, even with doubling down to 2 Ohms.

I plan on a total of 69,400 uF per channel, as you could have seen from previous posts.

That's about 44% of what (the transistors) you use in JC-1. I don't know its power rating, so I cannot compare that. A link to it would be appreciated.
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Last edited by dvv; 14th November 2012 at 05:13 PM.
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Old 14th November 2012, 05:45 PM   #7580
a.wayne is offline a.wayne  United States
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Its DIY DVV, you can build what you want , space is there for what was suggested . turn the trans on it's side, layer tower style on the inside...

Go for it ....
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