Hey Helix... I have one question about Crescendo? - diyAudio
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Old 8th March 2002, 09:20 AM   #1
Eccu is offline Eccu  Finland
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Default Hey Helix... I have one question about Crescendo?

Helix,
You send couple of pictures about your Cresendo Amp in following thread:

Crescendo Millenium amplifier (ELEKTOR magazine ¹4 2001 p.36-45)?

1. I quess that your amps transformer have four (2+2) output wires so how many rectifiers do you have in power supply?
One or two?

If you have four outputs, have you attach transformer wires(zero/ground/something) as picture 3. shows?
Or have you made power supply like picture 2. shows?

I have transformer with four output wires.

Or which way is the BEST way?
Or is there some better way?

Thanks...


Yes... I have very bad English...
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Old 8th March 2002, 09:21 AM   #2
Eccu is offline Eccu  Finland
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dam... too big pictures....

take some time.....


weird... This kind message:

The image that you have attached is too big. Please make it no bigger than 800 x 600.


And my pictures is lot of smaller than Helix pictures?!
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Old 8th March 2002, 09:31 AM   #3
Eccu is offline Eccu  Finland
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pic 1 again
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File Type: jpg pic1.jpg (12.0 KB, 1467 views)
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Old 8th March 2002, 09:33 AM   #4
Eccu is offline Eccu  Finland
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pic 2
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Old 8th March 2002, 09:34 AM   #5
Eccu is offline Eccu  Finland
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pic 3
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Old 12th March 2002, 09:39 AM   #6
Eccu is offline Eccu  Finland
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Old 12th March 2002, 05:57 PM   #7
Kay is offline Kay  Germany
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Try pic2, but think about the GND-wires.
The Gnd-wires are bad painted.
Add all together at one point, may be the best at the elkos
Greetings
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Old 12th March 2002, 07:41 PM   #8
Helix is offline Helix  United Kingdom
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Ok

First of all, i am sorry about the pics, i only relized there size after posting them. I get kind of forgetful of how lucky i am about this T1 connection i have.

Eccu,
Quote:
1. I quess that your amps transformer have four (2+2) output wires so how many rectifiers do you have in power supply?
Yes that is right, the transformer has two seperate secondarys hence 4 output wires.

The actual transformer is just a standard RS part, 223-8279

I currently have 1 bridge rectifier in the suppy at the moment, so it is connected much like your pic. 1 (you can see it just inbetween the transformer and the bank of caps)

I think i am right in that saying the BEST way to wire it is as in pic. 2

However, i dicided to wire it as per pic 1 because of the protection board's AC detect circuit. At the moment i do not have the magazine with me so i can't remember why i thought this, but i did. I think maybe i was wrong and you can use 2 bridges but don't take my word for it! I was worried about some expensive burn-up or something so went for the 1 bridge and made sure it was a rugged one (35A 400V).

Also i think it would be better to move the loudspeaker ground from the point indicated (Amp board) to the center of the smoothing caps? is that right? that way you don't get large currents on the ground that the front-end and signal is using

2) The pics are just links to my website, maybe the 800x600 limit was introduced because of me

3) I got ALL of the devices that have to be heatsink mounted including the output FETs and the op-amp fromCricklewood Electronics which is based in the Uk and has a fairly basic website, but if you phone them they are extremly quick in searching for components and very helpful (IMHO)
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Old 22nd March 2002, 02:22 AM   #9
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Hi all

Just a Question:
Is there any point in having 1 single (2 output wires) transformer with 2 rectifiers and aditional caps?

Just another Question:
How big caps do I need for about 7 Amps? Will 40.000 do the job?

Thanx in advance

Bill.
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Old 22nd March 2002, 09:15 PM   #10
syl is offline syl  Sweden
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I would go for pic 2.

Reason ? The ground of a system is extremely important. Pic 1 will send the huge charging current spikes for the Electrolytics right through your system ground. Having that point as your reference is like trying to thread a needle standing up in a small boat in high waves - it is never calm and you can“t deal with fine stuff. The sonic signature of this grounding scheme is a very annoying harshness and a significant lack of low level detail. The harshness is there whatever you do with the amp itself. The only way to solve this is to make the ground quiet.

Pic 2 will lead those current spikes directly back to the transformer, completely outside the system ground. You have now your quiet ground. I once turned a very good amp to a VERY VERY good amp by just making this change to the grounding scheme.

It is interesting to note that a typical tube amp with a single supply and a single full-wave recifier will have this type of quiet ground also.

Considering the cost penalty of just one extra rectifier the payback in sound quality is huge. I would never consider designing audio PSU“s without this grounding scheme.

Regards

Syl
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