Quick advice on PSU for TA2024 T-amp

Ali Tait · Post by **Ali Tait** » Tue Jan 07, 2014 9:20 pm

A whole pound more each, steady on!

IslandPink · Post by **IslandPink** » Fri Jan 10, 2014 8:14 pm

Got the power supply bits and have made quite a lot of build progress this afternoon.

Anyone have any idea how much gain a TA2024 amp has , without a volume control ?
Just wondering whether to try to install one , or use some sort of voltage divider on the input to knock it down.
I have in mind that this evaluation with ta2024 might be short, if the other amp comes soon, and that one has a volume pot on the board already .

I'll go off and have a search again, see what I can find out ...

Ali Tait · Post by **Ali Tait** » Fri Jan 10, 2014 9:06 pm

I have read that Tripath chips do have some hiss at max output, certainly my Temple Audio jobbies do ( though they are not Tripath chips) so it may be best to drop the output a bit, especially given the sensitivity of what you will be using them with. At lower outputs mine are quiet. I use mine at about 70% of max.

IslandPink · Post by **IslandPink** » Fri Jan 10, 2014 9:49 pm

I'm just trying to get a useable volume level, as I don't use a pre-amp .
Just not sure how to work with the input impedance which I believe is only ~20k .

al newall · Post by **al newall** » Sat Jan 11, 2014 9:06 am

Mark.

If you're passing through Chester, i can lend you a bigger Tripath amp complete with volume control, to play with.

I do have a 2024 but its been messed about with and its not in a box.

IslandPink · Post by **IslandPink** » Sat Jan 11, 2014 11:12 am

Thanks for the offer Al , but I have my audio-buddy Len who has a 2020 unit nearer to hand ( Llanddulas ) and actually he came round last weekend to try that out on the tapped horn , I could ask him again if I need to loan . What I need is a way of using this one for a few days, then comparing with the 7297 when I get it . I'm almost at the point of wiring it into the box and listening . I did this one with a regulated power supply, so I'd like to hear how it sounds.
I believe it has about 25dB ( at least the Sonic Frontiers one does ) but that's a bit too much for direct running off my phono , I reckon I need about 10-15dB , maybe less . It's more a question of having advice on how people did the volume control . I've seen a diagram where there were a lot of fiddly modifications, and I'm not sure if they are all necessary .

IslandPink · Post by **IslandPink** » Sun Jan 12, 2014 3:14 pm

Evidence of progress shown below , just before final connections and screwing-on the top .
I checked the regulated voltage coming out : 11.94V .
I think that's close enough to 12V !
Not bad as that was based on an on-line calculator to pick the R1/R2 values for the LM338T . Used 385R and 3300R .

I just ran it with a signal generator into the tapped horn . It works !
However I think the output falls off significantly below 60Hz ( or maybe that's just the ears ...? ) . This unit seems to have 1uF as the input cap. I suppose 1uF and 20k input impedance will give an 8Hz roll-off ? Not ideal for a bass amp .

I'll do a bit more research on how to set the gain now , so I can play some music through it . I wonder if have a suitable transformer I could use ?

IslandPink · Post by **IslandPink** » Sun Jan 12, 2014 7:57 pm

Just did a comparison of this amp with the Pass F4 , both driven by signal generator .
Both options show a big dip in perceived output around 45-55 Hz . After some hunting around, it seems the output seems to retreat into the front corners of the room, either side of the bay window - very odd.

Below that , volume picks up again and sounds flat from 40 to 35 , then falls off rapidly ; however, the 40-35Hz output is relatively stronger on the Pass F4 , about the same as at 60-70Hz , so I think the TA2024 is falling off a bit below 50Hz .

I'll think I'll launch some dicussion of room modes, on my speaker thread.

IslandPink · Post by **IslandPink** » Sat Feb 01, 2014 7:07 pm

Ok, since last time, I received a couple of TDA7297 boards , so this weekend I installed one of those instead of the TA2024 . This has a volume control installed so it's more use to me generally .
I've got it working today , only on one channel at present, till I can get a couple more connectors .
First impressions are very good. Sounds quite clean overall and the bass & low bass is very nice. I haven't done all the sugggested tweaks yet, but I did increase the 0.22u input cap ( on the left channel ) to a 1uF ( electrolytic ) that I had to hand, so I hope that's extended the bottom-end somewhat .

Thanks for the tip-off on this chip - should be useful for a TV amp as well .

I'll order a few better parts from HiFi Collective now to finish off the job.

Ali Tait · Post by **Ali Tait** » Sat Feb 01, 2014 8:48 pm

Let us know what tweaks are worthwhile please Mark.

IslandPink · Post by **IslandPink** » Sat Feb 01, 2014 9:23 pm

Willdo .
I was reading this earlier - so input cap quality, plus bridging the diode ( in my case an LED ) might be worth doing .
http://www.audiocircle.com/index.php?PH ... c=122152.0
Further listening proves the top-end is not up to a good valve amp ( no surprises there ) but the low-end is very satisfying, and better than my 300B amp as far as I can tell .

steve s · Post by **steve s** » Sat Feb 01, 2014 10:11 pm

Hi mark mine are still in use whist the Px 25 is being sorted out, I've been going to short out the input cap but not got around to it yet
There is a lot of of cross talk on them. I have been using one unit per channel with a power supply for each unit. it has really cleaned up the sound, although there is nothing like the clarity of the of better valve amps

Ali Tait · Post by **Ali Tait** » Sat Feb 01, 2014 10:37 pm

Well yes, but consider the purchase price..

Ali Tait · Post by **Ali Tait** » Sat Feb 01, 2014 10:38 pm

IslandPink wrote:Willdo .
I was reading this earlier - so input cap quality, plus bridging the diode ( in my case an LED ) might be worth doing .
http://www.audiocircle.com/index.php?PH ... c=122152.0
Further listening proves the top-end is not up to a good valve amp ( no surprises there ) but the low-end is very satisfying, and better than my 300B amp as far as I can tell .

Thanks for the link Mark, useful info.

Mike H · Post by **Mike H** » Sun Feb 02, 2014 12:46 pm

45 - 55 Hz, is right on the 50 Hz mains isn't it? But OK either side - too much of a coincidence?

audio-talk

Quick advice on PSU for TA2024 T-amp

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