Tripath TA2022 Amp project [Archive] - The Art of Sound Forum

activexp

22-12-2011, 16:35

This is a little project I've started to construct a power amp using the TA2022 chip. The board and component kit are from eBay seller zoe_tsang, case and other hardware from CPC/Farnell and the 300W 24V toroidal transformer from Airlink. Grateful thanks to Reid Malenfant (Mark) for providing a suitable heat sink for the chip. :)

http://a2.sphotos.ak.fbcdn.net/hphotos-ak-ash4/s720x720/397887_10150636911819832_528289831_11807400_418058 082_n.jpg

The board is quite small and curiously has only 3 mounting holes :scratch: It's marked V1.1. Two resistors and one diode are already soldered in place which I believe is an update to V1.3 according to a post by the designer LJM on the DIYaudio forum.

http://a6.sphotos.ak.fbcdn.net/hphotos-ak-ash4/s720x720/408954_10150636912114832_528289831_11807402_201537 0571_n.jpg

After a dry run laying out the parts in the case, I found that some of the heat sink fins fouled the transformer and had to slice about half an inch off 5 of them. Despite that, I'm confident that heat dissipation will be adequate.

http://a8.sphotos.ak.fbcdn.net/hphotos-ak-ash4/s720x720/405736_10150636911934832_528289831_11807401_711515 522_n.jpg

The finished rear panel with fused IEC inlet/outlet for providing AC mains to my DIY pre-amp. I've yet to finish the front panel which will pretty bare with an on/off switch, LED power indicator and a volume control.

Over the holiday I'll start on assembling the board and will post later.

Cheers,
Steve

Reid Malenfant

22-12-2011, 16:38

Nice neat rear panel Steve :) Would be rude not to follow this one, looking forward to your updates, good luck with it :D

rusty bearing

22-12-2011, 17:20

:popcorn:

activexp

24-12-2011, 11:26

:popcorn:

:cocktail:

Ant

24-12-2011, 11:34

Nice neat rear panel Steve :) Would be rude not to follow this one, looking forward to your updates, good luck with it :D

Me too :)

activexp

30-12-2011, 17:21

Finished populating the PCB with no major problems apart form getting solder into an empty hole meant for a cap. This proved impossible to remove even with a desoldering pump. Other methods also failed such as poking it through with a hot piece of wire. In the end I had to resort to drilling it out with a 1mm drill, the smallest I had available. This was actually oversize and left very little tinned contact for the cap but I think I've got away with it :rolleyes:

One curiosity is that the relay has 8 tags but there are only 6 holes on the PCB. The 2 'unused' tags I snipped off as there's no way the thing will fit onto the board with them in place. Hope I did the right thing :scratch:

http://a1.sphotos.ak.fbcdn.net/hphotos-ak-ash4/s720x720/403078_10150656332319832_528289831_11903692_102810 0409_n.jpg

Next stage is wiring up the transformer and applying some juice to the board. I shall be keeping my fingers crossed that nothing untoward occurs. I suppose I should use a dummy load on the speaker outputs for the initial test.

Will post later with further updates.

Cheers,
Steve

Reid Malenfant

30-12-2011, 17:37

Hi Steve, looks good fella :) I suggest before applying power you put a low value resistor in series with the transformer secondaries. 10 ohm 2 Watt should be ok. These will go up in smoke if there is a serious fault, rather than the amp itself. If no fault there should only be a low voltage drop accross the resistors & the amp will idle.

A dummy load is a good idea for testing, though I'm not sure you'd need it just to check powering up is ok...

E2A:- I can see where the relay sits & yes you did the right thing cutting the extra legs off ;)

activexp

30-12-2011, 17:58

Thanks for the tip Mark, think I've got some suitable resistors somewhere. One point I'm not too sure about is the purpose of the 'mute' jumper. I assume it puts the amp into a 'standby' mode.

Reid Malenfant

30-12-2011, 18:05

Sounds like it does exactly what it says & mutes the output. My guess is you could do that with a switch if you wanted to, but the amp will be muted until the chip reaches a certain equilibrium. There will no doubt be all sorts of under voltage detection circuits that shut down the switching output stage until the under voltage lockout signals that the thing is ready to operate.

Effectively it should prevent thumps from the loudspeaker on power up & hopefully power down to ;)

Ali Tait

30-12-2011, 19:44

Desoldering braid is good for clearing PCB holes.

activexp

05-01-2012, 12:51

Temporarily wired up the transformer and switched on. LED lit up and relay clicked, no smoking components or blown fuses. All appeared normal :D

http://a5.sphotos.ak.fbcdn.net/hphotos-ak-ash4/s720x720/384003_10150671288574832_528289831_11984030_171857 7159_n.jpg

It's a bit of a tight squeeze to get everything to fit and with hindsight I should have mounted the board nearer to the back to allow more clearance for the power leads. The terminal block could do with being larger to accommodate heavier gauge wires. Likewise with the speaker outputs.

Next and final step is to complete the assembly which I hope to get done today.

Alex_UK

05-01-2012, 18:37

:thumbsup: Nice work Steve, look forward to seeing the finished article (and you telling us how it sounds. :))

Reid Malenfant

05-01-2012, 18:43

I popped in here earlier & should have found my way back again, thanks to Alex I just did :D

Glad it worked out for you Steve, looks like everything appears to be in order :)

Great work for your first kit of bits :eyebrows: Hope it spurs you on to other things fella!

activexp

06-01-2012, 15:21

All wired up and working nicely :)

Before connecting to speakers I adjusted the DC offset with the 2 tiny presets on the PCB. When I first got the board I was very much in the dark about this and had no idea how to measure it or what voltage it should be set to. After doing some Googling I found that it was a simple matter of connecting a millivoltmeter across the speaker terminals and adjusting for 0V or as close as possible on each channel. Well I think this is what you do!

http://a2.sphotos.ak.fbcdn.net/hphotos-ak-ash4/s720x720/397666_10150674068384832_528289831_11994036_850725 788_n.jpg

For the moment knobless ;)

http://a7.sphotos.ak.fbcdn.net/hphotos-ak-ash4/s720x720/378120_10150674068494832_528289831_11994038_113535 8958_n.jpg

With no signal input and connected to my very efficient Gusto2 4ohm 3-ways, there's a small amount of hiss just audible when I put my ear right up to the tweeter. I'd prefer total silence but it's so low I can live with it.

In the brief time that I've had to do some serious listening I'm not disappointed :) It sounds very similar to my diminutive Muse TA2024 but with better dynamics and bottom end weight. Both amps seem to have the ability to pull out fine detail to the point where individual instruments are easily identified and not lost in the general background.

One thing I have noticed is that the LM7805 voltage regulator runs very hot. Dunno if this is something to be concerned about?

To be continued....

Cheers,
Steve

Reid Malenfant

06-01-2012, 15:36

Nice one Steve :) Bang on with the DC offset by the way :D

If the regulator is running hot then give it a small heatsink, something like this would be perfect (http://www.ebay.co.uk/itm/3-X-TV5-Black-Anodised-Heatsinks-TO-220-21-6-C-W-/390377033237?pt=UK_BOI_Electrical_Components_Suppl ies_ET&hash=item5ae448ce15) ;)

Or as an alternative simply cut a small bit of aluminium sheet & bolt it on :)

activexp

06-01-2012, 18:03

Hi Mark, thanks for the link re heat sinks. I've seen these too:

http://www.ebay.co.uk/itm/10-x-ANODIZED-ALUMINUM-HEATSINK-HEAT-SINK-220-F-/330610959122?pt=UK_BOI_Electrical_Components_Suppl ies_ET&hash=item4cf9f2e312

Ten for £1.22 inc shipping, can't be bad. Not that I need that many but they might come in useful one day :)

Reid Malenfant

06-01-2012, 18:09

activexp

11-01-2012, 17:41

Forgot to mention that the board I received is marked 15 - 26 Volts on the AC input, not 18 - 24 Volts as quoted in the specs and confirmed by zoe_tsang. Could have got away with a 2x25V transformer from CPC after all :doh:

Generally very pleased with the performance so far. Lasted longer than an Onkyo Mini System that went up in poof of smoke after only 30 minutes use while playing Elton John :steam:

Reid Malenfant

11-01-2012, 17:46

Live & learn, the important thing is it's working & I'm assuming sounding OK :D

spendorman

11-01-2012, 18:24

Lasted longer than an Onkyo Mini System that went up in poof of smoke after only 30 minutes use while playing Elton John :steam:

Must be a joke in there somewhere

Apologies

activexp

23-01-2012, 15:49

Take a look around the regulator to check that you have the room for one of those, as it looks like the fins will be on the back of the regulator & they may well be tall enough to almost reach to PCB level.

If they'll fit they'll do the job though :)

E2A:- looks like there is a 1W resistor directly behind it. You may need to cut some of the sink off, but again it'll still have a good load more surface area - go for it :D

You're right, there's not enough clearance for those heat sinks from ebay. There's a capacitor on one side of the 7805 and the resistor you mention on the other. However, mounting it upside down might work but it'll sit on top of the cap, not good.

According to ljm_ljm on the other forum, the temperature of the device is within limits and not something to be concerned about, so I'll leave it 'as is' for now.

As for sound quality, I'm generally very satisfied but at times I do get the impression that sibilants on vocals are slightly exaggerated. That's compared to the only amp I know well, NAD C325BEE which has a 'softer' presentation. Which one is more accurate I wouldn't like to say :scratch:

Cheers,
Steve

activexp

10-02-2012, 16:10

Is it normal for smoothing caps to get hot? The 2 x 4700uF/35V are getting pretty darn warm and one of them appears to be bulging :( Not a good sign.

Puffin

10-02-2012, 19:54

Is it normal for smoothing caps to get hot? The 2 x 4700uF/35V are getting pretty darn warm and one of them appears to be bulging :( Not a good sign.

No, they should not get hot!

Sounds like polarity is wrong. If they are they will blow:stalks:

activexp

11-02-2012, 11:28

Thought as much :(

Polarity is correct.

Been thinking about this. As the supply voltage to the board is 24V AC, after rectification that's 34V, rather close to the rating of the caps.

The voltage regulation of the transformer is quoted as 6% so it's possible that it's giving 25V in which case the DC will be over 35V.

Looks like I'll have to replace them with 50V ones, if I can find any that'll fit the board.

Reid Malenfant

11-02-2012, 19:26

A switching amplifier that is single ended (IE not a bridge) will cause what is known as "bus pumping". Energy that is stored in the output inductor has to go somewhere when the output stage switches & as it is can't run in a continual loop like the current could in a bridge amp it over charges the main reservoir capacitors :rolleyes:

I don't know why I never saw this coming. The higher the volume level you listen at the worse it is likely to become.

It might be interesting to stick a DVM on the storage caps at a reasonable listening level & see what voltage they are getting charged to. This will give you a good idea of the kind of capacitor voltage you are likely to need.

I have a box of 200 x 80V 5600uf capacitors on the way shortly (to help beef up the PSU in a monster of a Parasound amp I have just bought). These are 35mm diameter & 35mm tall Nichicons. If they are of any use please let me know & you can have a few. If you can remote mount a pair you can have 4 of them :) Not sure if they'll fit though... Measure & let me know ;)

activexp

12-02-2012, 13:50

Oh :scratch: From the description of 'bus pumping' it certainly seems to be the case with this amp. Not sure how this effects the sound quality. Bass seems fine but I don't listen at high levels although I have noticed an increase in hum & noise :(

Some of the other TA2022 amps I've seen have 50V caps and I've found a source of 5600uF ones that are the required 22mm diameter to fit on the board.

I'll give them a try and hope they do the job.

P.S. Are switch mode power supplies more suitable for class D amps or do they suffer from 'bus pumping' problem too?

Cheers

Ali Tait

12-02-2012, 13:54

My Bantam Golds sound much better with their linear power supply.

Reid Malenfant

12-02-2012, 16:45

P.S. Are switch mode power supplies more suitable for class D amps or do they suffer from 'bus pumping' problem too?
An SMPS would still have the bus pumping problem on it's capacitors given that the amplifier you have there is not a bridge amp.

All the little class T amps available appear to be bridge amplifiers, so won't suffer the same problem..

activexp

13-02-2012, 11:09

Right............so if I used 2 x TA2022 boards in BTL, the bus pumping would no longer be an issue?

Reid Malenfant

13-02-2012, 15:59

Yes, you'd need to make sure that the power supply was shared though.

Wouldn't be too difficult to connect + to + & - to - & the grounds together.

The only other thing is depending on what speakers you intend to use, you might need to alter some of the output reconstruction (low pass) filter components.

Other than that I can't think of any other difficulties :scratch: Tell a lie :eyebrows: You'd need to invert the input to the second amps! Also I seriously doubt they'd like 4 ohm speakers as the current draw would be the same as hooking up a 2 ohm speaker to your amp as it is at present :eek:

activexp

13-02-2012, 17:43

Thanks for your valuable input Mark :)

Think I'll forget that idea seeing that the speakers I use most often are 4 ohms.

Now that I've been bitten by the amp bug, what is your opinion of LJM L12-2?

http://www.ebay.co.uk/itm/120744995234?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

I assume that it'll be OK with 4 ohms.

Reid Malenfant

13-02-2012, 18:00

If the circuit is basically the same as the L20, which looking at it, it probably is then all I can say is it could be a good bit better ;)

It's quite a simple circuit with some good points, however I would have done a few things a little differently :eyebrows: I did actually think about purchasing a couple of L20 amps & modifying them, it wouldn't take a lot of work to bring them up to a very good spec, or should I say the kind of spec that I would want to produce superb music rather than just have a superb spec :D

Lets just say that for the money they'll be excellent VFM & sound fine, but with some work on them they could be very good indeed :)

Yes that'll be fine with a 4 ohm load...

activexp

14-02-2012, 20:06

That's encouraging :) I might take this one up as a BIG AMP project.

For the PSU + Speaker protection I've got my eye on this:

http://www.ebay.co.uk/itm/F6-Universal-Power-Supply-15-36V-10A-Amplifier-Board-Speaker-Protection-/220925776483?_trksid=p5197.m7&_trkparms=algo%3DLVI%26itu%3DUCI%26otn%3D5%26po%3D LVI%26ps%3D63%26clkid%3D6329624530820428411

Looks like it'll do the job.

activexp

18-06-2012, 10:18

:( After a few months of relatively infrequent use, the TA2022 amp has died in a puff of smoke, not entirely unexpected due to the heat issues with the voltage regs, inductors and smoothing caps.

I was surprised to see that the only visible damage is a burnt out 6.2 ohm 1 watt resistor, circled in red below:

https://fbcdn-sphotos-a.akamaihd.net/hphotos-ak-ash3/s720x720/556210_10151198786939832_753137291_n.jpg

As the designer ljm has not made available schematics it's difficult for a layman such as myself to diagnose the cause of the failure and attempt a repair. Probably uneconomic anyway.

So it's the scrapheap for this board, a shame really as the sound quality was excellent.