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Old 10th December 2007, 09:25 PM   #21
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I'm sorry to hear about your blown up Tripath, I've been heartbroken 5 times now!

Currently I'm running it from a modified HiFiDIY.net mini TDA1543 DAC, driven by a squeezebox 3 over TOSLINK. I just bought the ~$40 DAC kit, stacked another 3 X $2 TDA1543 chips on top, tweaked the I/V resistors accordingly and it sounds absolutely stunning. I hope I'm not prompting a TDA1543 war, but my setup definately sounds best with 4 or 5 chips, just 1 sounds twitchy and more than 7 sounds a bit dull.

The non-NOS DAC that I was considering is this one http://us.hifidiy.net/Article.asp?articleid=203 Does anyone know if it will sound nice or not?

For anyone interested, I'm continuing exploring the exploding Tripath phenomenum here, since it relates to the 41hz AMP10 basic amplifier: http://41hz.com/Forums/topic.asp?TOPIC_ID=1567
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Old 11th December 2007, 01:11 AM   #22
john65b is offline john65b  United States
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I have that same TDA1543 Mini DAC and was jut OK stock. Like you, I bought three more of theTDA1543 chips to stack on the original, but haven't been able to get at it with all other stuff on my plate.

Hmmm, maybe I will try her tonight - I have that little TDA1543 program that calculates new I/V resistor combos for different output voltages, etc, but curious as to what you set yours at...

Let me know.
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Old 11th December 2007, 09:47 AM   #23
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Before I get slated for messiness, I do realise that I need to invest in some flux cleaner but here are some photos of the DAC and the minor modifications that I made.

Basically I just piled the chips on top, added that resistor on the bottom, and a trimmer on the top (1K trimmer would be better probably). To be honest that resistor on the bottom isn't needed, you just need the trimmer pot. I have it there because I couldn't find a 1K trimmer

I have also removed a resistor to give me a vref of around 9.3 volts which appears to be fine. It's running from 12.6v from a homemade smoothed supply. All driven by a baby 9v torroidal tranny.

I would recommend not trimming the I/V pot whilst connected to the amplifier, it can result in some nasty output and you might blow up your amp (...see above)

Click the image to open in full size.

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Click the image to open in full size.
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Old 11th December 2007, 01:24 PM   #24
john65b is offline john65b  United States
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Be careful with that voltage - I think the TDA1543 was good for no more than 8V - 9V.

I like the 1K trimmer. I plan on redoing the R2 on the LM317 to get 7.25V instead of the standard 5V.

Also remember the increase in voltage and addition of three more chips willl get that unit HOT...may need some heatsinking...or won't sound good for very long

Sorry for hijacking the thread...
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Old 11th December 2007, 06:19 PM   #25
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Oddly enough it's ok at this voltage with 4 chips and air gaps between them. They do run rather warm but it seems able to dissipate the heat ok, I had it running for 3 hours solidly without problems last night.

I did some experimenting a while back and experienced overheating with 7 chips stacked at 9v, it played fine initially but started to distort and make bad squeaky noises after 5 mins. I also have managed to blow a channel on one of these DACs when my amp exploded, but generally they seem very resistant to abuse.

Once I get around to putting all this gubbins in a nice shiny case, I think I will epoxy some horizontal aluminium/copper strips between the chips to get the heat down a bit. I guess that running them hot is bound to reduce their service life considerably.
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Old 11th December 2007, 07:04 PM   #26
Pano is offline Pano  United States
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Quote:
Originally posted by bongoman
A Micromega Stage 5 / Quad 444 / Quad 405 stack sounds lifeless and boring in comparision.

No surprise there. The Quad 405 is one of the most lifeless and dull sounding amps I've ever heard. The Quad 303 was a little better.

Sure hope your TA2022 holds up!
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Old 11th December 2007, 07:54 PM   #27
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We've had one mute so far, I nearly soiled myself but it came back ok after a power cycle fortunately. I'm sick of swapping chips out!

Having listened to this thing for a bit, it's still outstanding and seems to be improving with use! There is much much better stereo separation and general instrument definition than anything else I've ever heard. Even listening to tracks I've listened to many many times in the past and on many different setups, you pick out things in the music that suprise you. I'm well chuffed, and at around $200 for the DAC, amp and transformers it is a remarkable bargain.

I think most of the "magic" involved with how this thing sounds is down to the DAC, I noticed while setting it up and running tests on spectralab that the TDA1543s easily outsmarted the DAC built into my THX Altec Lansings. Running the speakers through the TDA1543 and into their analog input sounded far far better than running the speakers over S/PDIF. I was shocked, I thought those were pretty good sounding speakers before I did that.

I'm running all this through some Richard Allan RA 8 series II reference monitor speakers btw.
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Old 14th January 2008, 07:52 AM   #28
frammis is offline frammis  United States
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Hi Bongoman,

I used to be really familiar with the TA2022 and torture tested it on the Tripath eval boards many times (yep, I used to work there). It is supposed to withstand +/33V rails and even short circuits without blowing up. However there are a few things to watch out for, which I'll list in no particular order:

1. Watch out for open zobel resistors (the 5.6Ohm 2W ones in the output filter circuit). When you put high power into an open load, these can sometimes blow up, and if they do, you will probably blow up the part every time the speaker relay opens.

2. Supply pumping could occur if both outputs get a big low frequency signal at the same time. Basically, the TA2022 kicks current up through the highside FETs back into the power supply caps and increases the voltage temporarily above 33V. The same thing happens to the -33V rail on the low side. I kind of doubt this is your issue, though. The 10000uF caps that AMP10 uses should be sufficient to absorb a lot of charge. Over voltage tends to be a non destructive event anyway. It would just shut off harmlessly and come back on.

3. The part is sensitive to PCB layout. It really wants to have very close decoupling caps between VPP and VNN and close protection diodes near the outputs (especially the lowside diode from VNN to out). We blew up parts during short circuit testing when that diode was removed, the wrong type, or too far away.

4. Did your speakers sustain damage when the part blew up? Do they still sound good? We had a guy blow up a bunch of 2022's when his speaker's crossover failed and he had a 0.5Ohm short. I would try some dummy loads or maybe another set of speakers just to be sure. The over current protection does a better job with hard shorts (+wire to -wire) than with softer shorts.

5. This part uses a bootstrap gate voltage driver for the highside FETs. That means it has to keep switching in order to continue to replenish the gate drive supply voltage. If a big sustained clipping signal appears, it could lose enough charge to stall out the driver. Pulling the inputs out while it is running could produce that kind of signal if the input stage saturates. I wouldn't say that would normally blow it up. I'd think it would just tend to stop producing audio. It would kind of sit there and sulk about 10V above the negative rail.

6. In general, lower voltage is safer, so if you can find a variac you could reduce your supply voltage a bit, though the amp would clip sooner. This is kind of a last resort, since you don't really want to decrease your power output.

Even with high gain and heavy clipping the amp should be robust, so I hope you can find this problem and get up to full power without fear!
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Old 16th January 2008, 12:15 PM   #29
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Many thanks for your ideas/comments Frammis!!

I haven't touched this amplifier for a while, but once I get back to it I'll give it a serious looking over and post back anything that I find.

I am still pretty sure that all of the chip failures were when I was running the chip with a high gain, hopefully with the "general" gain setting I won't have any more chips popping.
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