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Old 23rd March 2010, 11:54 PM   #1
Lico is offline Lico  United States
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Default amp recommendation

I would like to try building a new amp. The son of zen and related designs look very interesting, but since I've never built anything like it I haven't the slightest idea how to start messing with the schematics.

I've done a tube amp that I love and a chip amp that sucked. However, the chip amp required a pretty expensive power transformer that I would like to reuse if possible. It is 225VA, 2x24v. Does anybody have a design that would work well with this power?

I don't have any speakers for it yet, but I will be using full range drivers in a small-ish package (sealed maybe?)

Lico
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Old 24th March 2010, 02:12 AM   #2
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If you are dead set on reusing that trafo then you will have to find an AB class amp of around 60watts/ch. The Pass forum is pretty much geared towards class A operation which generally uses much larger power supplies with lower rail voltages. You should pose the same question on the Solid State forum where you should get many proposals and suggestions. There's plenty of good sounding AB amps out there.

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Old 24th March 2010, 11:23 AM   #3
juma is offline juma  Germany
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Quote:
Originally Posted by Lico View Post
... power transformer that I would like to reuse if possible. It is 225VA, 2x24v. ...
SymAsym5 - Project

Search in Solid State section of the forum, there are numerous threads about this amp.
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Old 25th March 2010, 05:52 PM   #4
Bigun is offline Bigun  Canada
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If you want to build a design by Nelson then I don't see why the trafo you have can't be pressed into use. You can build a Class A amplifier with this trafo.

I'm not familiar enough with Nelson's amplifiers to suggest the 'best' one for you, but I would suggest that you choose one with an available pcb (again, not sure of what's available)

One option for a simple amplifier is Zen4, it recommends a 300VA trafo, but if you can accept a more limited headroom and lower bias current you could at least start with your 225VA.
http://www.passdiy.com/pdf/zen-v4.pdf

Or look at one of the Aleph's.
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Old 25th March 2010, 06:05 PM   #5
EUVL is offline EUVL  Europe
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225VA 2x24V will do ONE channel of F5 if you add a regulated power supply as per Zen Version 3.
Too much voltage and too little current for 2 channels I am afraid.

If a 225VA transformer is expensive for you, then maybe you should find something else other than Class A.
This is certainly not the only costly item and most likely not the most costly item.


Patrick
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Old 26th March 2010, 03:10 AM   #6
Bigun is offline Bigun  Canada
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this thread is so disappointing... where is the DIY spirit, can people only build things exactly as an original, nobody with any vision here as to how to make something with a given trafo ?

perhaps the Solid State forum would be a better choice afterall.
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Old 26th March 2010, 03:48 AM   #7
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It has nothing to do with the DIY spirit. It has everything to do with basic math.

34V rails with an 8ohm speaker requires 4.5 Amps per channel. x 2 x 68v total = over 600 va
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Old 26th March 2010, 05:32 AM   #8
DougL is offline DougL  United States
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I agree with Bill.
If it was a 600 VA transformer, I would suggest a regulator to lower the rails to 24V and build an F5. But 225 VA is really not enough, especially if you burn some off in the regulator. And Choke input would help, but spending $50 to use a $30 transformer seems a bit silly. On the other hand, we are silly types hereabouts!

Doug
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Old 26th March 2010, 12:20 PM   #9
juma is offline juma  Germany
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With that transformer (2x24V, 225VA) two channels of F2 could be built with somewhat lower bias - one channel per secondary. Some regulation can be added to lower the voltage to +24V (CRC or active, F3 style).
It's simple, it's class A ...

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Old 26th March 2010, 05:30 PM   #10
Bigun is offline Bigun  Canada
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That's more like it !!!
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