Quick advice on PSU for TA2024 T-amp

[IslandPink]

Hi Chaps
My buddy Len gave me a TA2024 amp board ( from EBay ) a while back .
I'm intending to use it for TV use or just low-bass duty for the tapped horn for my 4-way speaker .
I've located a box that I think is just big enough ( if I strap the transformer to the outside ! ) , so I ought to get a few bits now to make up a power supply .
I've done some searching but not found much useful detail anywhere on how to make up a passive supply . However, PSRR looks quite good so I don't think it needs to be great .
It appears all I need is to make a single +supply around 12 to 13V , perhaps 3A peak ?
I'm intending to use a 50VA toroid ( 2x 12V ) ; then CMC > Diode Bridge > 4700u ( 5 to 6A ripple ) > 1R > 10,000u . This should give about 100mV Pk-Pk ripple on the output .

Anyone got any advice , alternative ideas, etc ?

[Nick]

Cant say for certain with your board, but I have found them to have very poor PSRR, so I would suggest as much smoothing as you can get. I would conside a three pin 5A regulator.

[IslandPink]

Ah OK - thanks .
Something like a 338T then ?
http://www.rapidonline.com/Electronic-C ... 8T-47-3322
I assume it just needs Bridge then big ( 10,000u ) cap then regulator ?
The case is a heavy aluminium RS box, so plenty of heatsinking there.
The amp board is like this one :
http://www.ebay.co.uk/itm/2x15W-MKll-TA ... 3988wt_958

[Nick]

Yep, that sort of thing. Try them and see what sounds better.

[IslandPink]

I bought a few bits from Rapid last night . LM338T , some hefty 4700u/25 caps and an encapsulated transformer that I can mount on the outside of the case . Only 30VA , 12+12V - not enough for full power without the regulator dropping out, but I think that'll cover my requirements for the tapped horn . Given I'm using both channels bridged (mono ) I can probably get 10-15W before any problems. The tapped horn is ~96db/w .

I can test with some sine waves from the sig.gen and see how loud it goes, anyway .

Thanks again Nick .

[Nick]

Yep, those things only draw a low idle current.

[IslandPink]

Given I'm using both channels bridged (mono ) I can probably get 10-15W before any problems.

Actually I probably can't do this, but if I run one channel I should still be able to get over 10W - my power is more limited by the transformers and the LM338T dropout voltage than it is by the amp .
How do people double-up SS amps without one amp seeing the other's output impedance as the load ?

[steve s]

confessions... since i got back from owston i've only used the tda 7297 based amp in my listening room, i got hold of some ex led power supplys which run at around 13 vt/ 3a which were to be scrapped, they sound very good, although not quite a px 25..

the power supplies are basic 4 diodes with caps between and a biggish cap on the output, but to be honest i cant tell the difference between battery use and them, i have a 2020 based amp, and this is much cleaner and all for 2.50 each..

[al newall]

TDA7927 eh, something else to try.

Mark.

The TA2024 probably has the weakest bass of all the T-amps, though it may suit your application.
I used a decent 12v SMPS with mine, as it was supposed to be the best option. Never heard any improvement with linear supplies. Cheap enough to try both though.

[Paul Barker]

Isn't bass uncontrolled with a T amp?

[steve s]

Isn't bass uncontrolled with a T amp?

The bass is actually quite good on my larger speakers,
The best thing about the amp is the relative lack of grain in the sound. Its open and quite detailed,
Any one messing about with lesser valves and transformers .. It make you wonder about the point of it all.. Good valve amps beat it of course..
If your ever down my way...

[al newall]

Isn't bass uncontrolled with a T amp?

I have no idea Paul. Somebody else will have to answer that one.

My post is based on some experience of using these things, and little else.

Mark will perhaps do better with a TA2020 amp, or Steves TDA 7297 idea, which isn't a T-amp.

[IslandPink]

Thanks for the advice guys.
I will just see how it goes on this . The background is that I was given a 2024 T-amp circuit board , and have an Ali RS box that is just big enough to hold a simple power supply board and the circuit board ; so it's a relatively quick & simple project to build it up.
If it doesn't work to my satisfaction on the bass speaker , it'll be a neat solution to driving a pair of 'bookshelf' speakers for the TV . Then I can build another, using one of the bigger chips, or something else .

I guess a 2020 would be a bit better , with the extra power reserve, although, as I say above, the tapped horn is 96 dB/w .
Yesterday by audio buddy Len ( who gave me the board ) came round and we tried his 2020 T-amp on that speaker , using music and a signal generator . It didn't seem to be having any problems driving the speaker down to 35Hz and much louder volume than I would need, so I'm hopeful for the 2024 chip .

Once I've got it built up, I'll compare against a valve amp + Pass F4 .

[al newall]

Just out of interest, I bought a TDA 7297 amp kit as mentioned by Steve earlier.
http://www.ebay.co.uk/itm/181282733842? ... 1439.l2649


Took about an hour to build, once i'd straightened the chip pins enough to fit in the holes.
Temporarily hooked it up to a decent 12v SMPS.
Have to say i can see why Steve likes it.
It's punchier and in many ways more convincing than the 50w Tripath amp i've been using.

Pretty good for less than a tenner.

[IslandPink]

Interesting . So you reckon it's better in the bass then ?
I should just buy one really - I only need one , so that's a fiver !
Edit : ( Sorry that's a stereo board isn't it ! )
I can trial both on the tapped horn and the OB midbass unit & see what I think, if they both need a single +12V supply .