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Old 13th November 2005, 04:07 AM   #1541
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Default Try Shindengen D25XB60 SIP Bridge rectifiers

Found these at Mouser. Going to try in my mono-blocks. They are overspeced. But are cheaper than the 8 amp used before.
Many friends feel higher current diodes sound better due to lower voltage loss. Cannot comment, but cannot hurt.

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Old 13th November 2005, 06:54 AM   #1542
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Quote:
Originally posted by BrianDonegan
You don't need a 10A trafo for a 3886. Your 24-0-24 (8 amps) trafo should be perfect for this amp (2 channel).
Brian, thanks for the clarification. After reading Nordic's post, I went out and ordered a 22-0-22 400VA trafo.
I'll try it out on the amp when I build it and see if there's anything beneficial.

BTW, how do you rate the My ref kit (as put up on Twisted Audio's website) against something like the Aleph3 or 30. If you don't want to post it here plese mail me as I am most interested in opinions. That goes for anyone who has built and auditioned this amp and willing to share that bit of info. I'll be most grateful to hear from you guys.

Thanks.
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Old 13th November 2005, 10:37 AM   #1543
Nordic is offline Nordic  South Africa
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Yes you don't need it but in my defence I'll quote the datasheet
Typical max output current = 11.5A. You can't output what you didn't put in. However yu could have a weak chip as the limit (worst case) is 7A, so the 8A one could also be ok.
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Old 13th November 2005, 11:37 AM   #1544
mikelm is offline mikelm  England
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The transformer rating of 8A means that you can run it continuesly at 8A average output without it getting too hot.

It does not mean that you cannot get a 10A or 11A peak.

At either 8 or 10 amps the voltage will drop compared to 1A output but good sized reseviour caps and feed back will minimise the effect of this.

so, no worries about getting max power from chip...


mike
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Old 13th November 2005, 12:18 PM   #1545
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One of those cases where everyone is right. Peak current is 11A, but that will be a rare achievement while listening to music, and the 20kuF will take care of thoe musical peak current.

That's a nice bridge. Let us know if you can hear a difference. I am open to changing it, but would need to be sure not to upset the kit cost.
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Old 13th November 2005, 02:59 PM   #1546
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Nordic, no worries, man. relax. It's all good. I appreciated the advise and that's why I ran out and ordered the trafo. It didn't dent me too much. In fact I am looking forward to experimenting with it and at least I know I am not underpowering the amp. Tuition fees...
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Old 13th November 2005, 07:52 PM   #1547
protos is offline protos  Greece
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Well I was mainly right that you don't need a huge trafo to listen to this amp at low volume levels and you guys were right that it is an excellent amp.
Let me explain.
When I switched the 120va 18v trafo for two 220va 12v trafos with the secondaries in series (24V) I saw a few improvements but not very big.First of all it could go louder without strain.This is to be expected.At lower volumes things were not that different.A little bit clearer in the bass and slightly wider soundstage BUT the annoying quality in the upper midrange was still there.Again a lack of air and some graininess that did not feel natural.
It was not until I started playing with the biasing of the zeners that I got the sound I was more or less expecting.When I went from the 1k resistors to about 680 ohm there was a dramatic IMHO change in the sound.Suddenly there was more space depth and air and smoother high freq extension.
I finally settled on 600 ohms which I found gave an even better presentation in the mids and highs.
I cannot for the life of me understand why this should affect the sound as much as it does.After all we are not talking about biasing a signal carrying device.But all I can say is that it does in a big way.
Now this amp sounds really really good.Very hard to choose between it and the Aleph X (which in my book sounds much better than the normal Aleph I had before ).I need to listen a bit more and split some hairs.
I also find that in my set up it does not need an active pre like some other amps.It has plenty of gain and does not really lose dynamics with a passive pre.The active pre takes away some transparency.

Now tomorrow if everything works out I may take it to Audiopax a couple of blocks away and plug into their reference system and see how it fares .
Heh, heh ...would anybody here like to know the results?
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Old 13th November 2005, 08:06 PM   #1548
t. is offline t.  United Kingdom
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Quote:
Originally posted by protos
Well I was mainly right that you don't need a huge trafo to listen to this amp at low volume levels and you guys were right that it is an excellent amp.
Let me explain.
When I switched the 120va 18v trafo for two 220va 12v trafos with the secondaries in series (24V) I saw a few improvements but not very big.First of all it could go louder without strain.This is to be expected.At lower volumes things were not that different.A little bit clearer in the bass and slightly wider soundstage BUT the annoying quality in the upper midrange was still there.Again a lack of air and some graininess that did not feel natural.
It was not until I started playing with the biasing of the zeners that I got the sound I was more or less expecting.When I went from the 1k resistors to about 680 ohm there was a dramatic IMHO change in the sound.Suddenly there was more space depth and air and smoother high freq extension.
I finally settled on 600 ohms which I found gave an even better presentation in the mids and highs.
I cannot for the life of me understand why this should affect the sound as much as it does.After all we are not talking about biasing a signal carrying device.But all I can say is that it does in a big way.
Now this amp sounds really really good.Very hard to choose between it and the Aleph X (which in my book sounds much better than the normal Aleph I had before ).I need to listen a bit more and split some hairs.
I also find that in my set up it does not need an active pre like some other amps.It has plenty of gain and does not really lose dynamics with a passive pre.The active pre takes away some transparency.

Now tomorrow if everything works out I may take it to Audiopax a couple of blocks away and plug into their reference system and see how it fares .
Heh, heh ...would anybody here like to know the results?

Very interesting, was the lower value resistors you used the same type material as the 1k's? carbon or metal
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Old 13th November 2005, 08:43 PM   #1549
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I'm glad you got it to an enjoyable point. I don't thin you need a big trafo either, just the right voltage. Interesting about your change, I'll try that.

I would always be interested in peoples experiences with it. Keep going man!
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Old 14th November 2005, 05:27 AM   #1550
Byrd is offline Byrd  South Africa
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Ok - as promised. The amp is now assembled sans chassis. This only took a day, so quick assembly - and no problems encountered. Pics are available on my project pics gallery.

Initial impressions from my side are that it sounds good, but I still prefer my new version Leach Amp that I have also recently built. There seems to be more texture to the mids. That "annoying quality in the upper midrange" rings true for me so I will try the resistor value change suggested - well maybe...

The female camp however prefers the MyRef to the Leach. It was described as smoother and clearer or more intelligable with more tunefull bass.

Either way - I am happy with the overall sound, it is certainly better than alot of commercial amps I have heard and would have no problem recommending the amp to others - especially less experienced builders. It does not run hot which is a big plus - especially if you are looking at multichannel.

Thanks Mauro, Russ & Brian for bringing this creation to the community.
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