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Cheap ebay pre amp, opinions please
Cheap ebay pre amp, opinions please
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Old 20th August 2013, 04:45 PM   #1
davym is offline davym  Scotland
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Default Cheap ebay pre amp, opinions please

Hi folks, I came across a cheap pre amp on ebay, (zoe tsang) same seller as the dual TDA7293 boards that are being praised on here.

Nice looking dual layer board, parallel class A, i'll try to link to it but I don't know if the link issues have been sorted yet.

Parallel Class A power Preamplifier kit-19 | eBay

Looks like the rectifier is on the amp board so maybe not so good!

Ebay rover failed again

They must hate selling things/making money.

Last edited by davym; 20th August 2013 at 04:50 PM.
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Old 20th August 2013, 05:44 PM   #2
davym is offline davym  Scotland
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Click the image to open in full size.

I made a copy of the sellers pic off ebay, I do like the selectable gain feature.
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Old 21st August 2013, 02:05 PM   #3
mrWagner is offline mrWagner  Hungary
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Why is it a problem to have the rectifier on the board?
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Old 21st August 2013, 02:09 PM   #4
KatieandDad is offline KatieandDad  United Kingdom
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Beware of a seller using the fact that the pre-amp runs in Class A as a selling point. The very low power output of a pre-amp enables most good designs to run in Class A.

I second the comment above too, there is no drawback to having the PSU on the same PCB as long as the layout is correct.

The only advantage of having a separate PSU is that you can play with the supplies to the pre-amp.

Last edited by KatieandDad; 21st August 2013 at 02:16 PM.
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Old 21st August 2013, 03:00 PM   #5
davym is offline davym  Scotland
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I was told some time ago that it is preferable to have the PSU diodes on an external board to reduce switching noise.

I agree it is better to have a well designed track layout than a average one with external PSU however and class A doesn't mean much at that low a level output.

The fake looking alps pot doesn't help much either.
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Old 21st August 2013, 03:14 PM   #6
KatieandDad is offline KatieandDad  United Kingdom
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IME the LM3886 is only a mediochre amp anyway so any good NE5532 will serve well as a pre-amp.

It has its followers, its a good bang for the buck, it's cheap to build. But with a few more bucks it can be surpassed by quite a substantial degree.

Those on a limited budget should try the JLH Class A amps as a starting point. OK the JLH, being only 10W isn't as powerful, but most of us use our amps at less than 10W anyway.

Last edited by KatieandDad; 21st August 2013 at 03:18 PM.
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Old 21st August 2013, 05:57 PM   #7
davym is offline davym  Scotland
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Funny you should sat that, I've got a JLH 10W in my watch list on epay, i'd link to it but this forum has issues with ebay links.

I was thinking about building it next but i'm still building my LM3886 and a passive preamp so it'll have to wait a bit.
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