Help needed with Tripath Board

I tried building a power amp based on the Tripath 0104 eval board and incorporating RLJones' and C. Brodersen's suggestions/tweaks.
My original goal was to build a no-compromise power amp, that's why I shopped around for the best components I could find.

Now that I've assembled evarything, though, I can't power up the amp without having it blow up in a few seconds.
I already blew up a board (the MOSFETs on one channel shorted out).

Now that I've gotten a replacement board, it looks like this is blowing up too. The MOSFET of one channel have already blown, and I've replaced them using the surviving ones from the old board. Once repaired, I've turned it on briefly (a couple-three seconds) before having to turn it off because something was smoking (I didn't have time to understand what).

I've already checked the power rails (without any load applied), and they are at +/- 75V. On the scope I don't see any big AC residue. The trouble is that I can't keep the amp on long enough to measure anything!

Is there anybody that can help me out with this?

On a different thought, I begin to suspect that I don't have all the necessary equipment/skills to troubleshoot this project. Does anybody know somebody that could troubleshoot this for me? I could ship him/her the amp...

Ideas, anybody?
 
Variac Power Limiting

Hello All,
A method I use when running up rebuilt TV swichmode supplies and rebuilt audio output stages is to to power them from a power limited variable AC supply with the circuit arrangement as follows -

240 into variac, 40 0r Watt switchable lamp in series between the variac output the primary of an isolation transformer, all built onto a suitable board.

On turning up the variac output voltage, if there is a fault condition, the lamp will glow brightly and dissipate mostly all of the power, therefore not enough energy dissipated in the circuit under test to cause damage.

I have used this arrangement in my day to day servicing work for many years, and this has saved me from expensive grief many times - I highly recomend this for running up new constructions.

I hope this can help you,
Regards, Eric.
 
I have used similar method (but no variac or isolation transformer) of hooking up a light bulb in series with the amp under test and if there is a short somewhere in the amp, the bulb would glow very brightly ........ to tell you to pull the AC plug right away and thus little or no damage done to the amp.
 
Thanks Mrfeedback and fcel, but I've got a problem with the filter capacitors.

I've got over 140,000 uF in the power supply section, and by the time they are full discharged the damage's already done!

I don't understand how is it possible that by just changing a couple of capacitors and resistors following the footsteps of others that have tried it before me I can cause the board to fry.

The modifications I made were:
a) changed the input resistors and associated filter capacitor to raise the input sensitivity.

b) I included an RC network on the input for preventing the circuit from oscillating. This is suggested by both Tripath and Jensen Transformers

c) I changed the value of four capacitors to 0.22 uF and the value of the associated resitor to 22R along the guidelines of Tripath, for preventing the circuit to go into self oscillation when the load is absent or removed.

d) I added some bypass capacitors (0.22uF and 1000PF in parallel) to the chassis ground on each the output terminals, following the advise of Tripath.

Can anybody spot anything particularly dumb I could have made?
:confused:
 
m.parigi said:
I tried building a power amp based on the Tripath 0104 eval board and incorporating RLJones' and C. Brodersen's suggestions/tweaks.
My original goal was to build a no-compromise power amp, that's why I shopped around for the best components I could find.

Now that I've assembled evarything, though, I can't power up the amp without having it blow up in a few seconds.
I already blew up a board (the MOSFETs on one channel shorted out).

Now that I've gotten a replacement board, it looks like this is blowing up too. The MOSFET of one channel have already blown, and I've replaced them using the surviving ones from the old board. Once repaired, I've turned it on briefly (a couple-three seconds) before having to turn it off because something was smoking (I didn't have time to understand what).

I've already checked the power rails (without any load applied), and they are at +/- 75V. On the scope I don't see any big AC residue. The trouble is that I can't keep the amp on long enough to measure anything!

Is there anybody that can help me out with this?

On a different thought, I begin to suspect that I don't have all the necessary equipment/skills to troubleshoot this project. Does anybody know somebody that could troubleshoot this for me? I could ship him/her the amp...

Ideas, anybody?

You should check if the ouput board is delivered the good DC fotr the gates of your mosfets.....by running the front end alone and take your multimeter.
If you find more than 20 V / theoric Gate source voltage for the Fets,then it is normal you blow them.
I suppose you have enough heatsinking.....
 
If you look at my original post, or one of the follow-ups, I alluded to a similar problem. The 'smoking gun' was a burnt out cap on the output filter (C21 as I recall, but double check as I'm going from memory). Another piece to this puzzle was running without a load. If an 8 ohm load was attached, I did not experience this problem. At no time did I damage a Mosfet, however. This is why I then added a 470 ohm/5W resistor in parallel to the output load in order to always have some sort of load present. Once I replaced C21 with a greater voltage rated polypropylene, I no longer experienced any smoke.

I've built up two Tripath amps (one 103 and one 104) and they're both running at my home 24 hrs/day without problems. I only changed what I originally indicated on my original posts, nothing more or less.
 
Eric,

I bought the boards directly from Tripath, as I recall it was about $400 apiece. Each board is a stereo unit. I then used a ParMetal chassis ($100) and built up a nice power supply for high voltage and one for the 5V bias supply ($200 or so for these). The cream was adding my usual Jensen input transformer (JT-11P), which runs around $150 for a pair. The amp total cost was thus about $800 to $900. (Again for details, please search this forum for a series of very complete postings that I did.)

The WAF and FAF was phenomenal: all like it. I kept the front panel very simple: 3 LEDs in a triangular shape: one red for power, one blue for signal and one yellow/amber at the top of the triangle for warning (distortion). The sound is very good, bettering many other amps I had on hand for comparison.

Robert
 
tripath testing

hi.

maybe i can help ; here is what we do;

use external power supply for the +5v and floating 12v (sitting on v-) , these supplies can be switched on before the +/- main supply.

then turn on the main supply gradually (with a variac), or preferably with a current limited vaiable power supply.

have a signal connected to the input and a scope on the output, if you like you can have a resistor of sau 1 kohm on the output.

you can use the setting for longest deadtime if you like but it should work with shorter settings as well.

the board has an undervoltage shutdown and will first start operating at around +/- 35v dc , with 4 ohm load and an error this could be very short , with our setup it should be safe unless you have a dead short in the output , if you do it will show at low voltage (i.e. before the amp starts operating)

our boards runs fine without output load and i doubt this will be cause for any problems (i have tested at least 50 boards), we suggest to use linear supplies for the mentioned +5 and +12 supplies , if you need more feel free to email me.

bye and good luck - k madsen - www.cadaudio.dk

$400 is somewhat more than what we charge :)
 
Hello Robert, thanks for your reply.
I use cheap auto-sound audio isolation transformers on the input of my power amp.
I have DPDT switches wired as reversing switches on the primaries to give audio polarity switching.
I find polarity normal/inversion to be mandatory, and the transfomers give a nicer sound than directly coupled.

What effects do the Jensen transformers give on youir system ?.
Can you describe a little more the sound of your amps ?.

Also I have had a brief listen to B&O ICEpower modules in a pre-production system, and found the sound to be dead clean, non load dependant, and NO IM distortion, but somewhat uninvolving, even a bit cold sounding.
I still need to get back with some music that I know and have a better listen.

Also I have been told of PWM amps causing RF interference problems - any problems with this ?.

Regards, Eric.
 
Eric,

Difficult to describe sound of Jensen transformers. I'd say it is a clean, smooth sound with them in the circuit; perhaps this is due to less external noise getting into the system. There are several manufacturers who use transformers, such as Jeff Rowland. I know a fellow who is in the recording industry (movies actually, and not too long ago got an academy award for his work); anyhow he tells me that many studios--at least those he uses--are beginning to change back to using transformers. They are great devices to remove hum and RF. If you get some that are not so well made, however, then the linearity and distortion will not be so good. (Most of the time, you get what you pay for, right?)

I have no problems with RF (maybe the transformers help; almost all my equipment, whether DIY or bought, has them or I added them).

As for describing the Tripath amp, it obviously depends on one's system. The Tripath 104 has outstanding bass control with very good low end resolution. Stage depth and width is also very good. The amp is very detailed, but does seem to border at times on being too detailed (I hesitate to use the word 'harsh'). I've heard smoother amps (DIY Alephs that I've built), but without the control. The 104 I built has a very large power supply and on the bench the amp delivered, as I recall, over 750 watts into a 4 ohm load (the exact figure was in my previous posting on another thread). I have no other amp around with that much power and so it is probably not surprising for it to have very good control. I think you'd be hard pressed to find a less expensive, high powered amp that is so efficient. I build other amps and like listen to various designs, but this one I plan on keeping for some time.

Over the Christmas holidays, a friend of mine who manufactures high end speakers was visiting with us and we sat around one day comparing amps. We listened to the Tripath 103 and 104, Aleph DIY (class A mostfet, 30W/ch), Millenium amp (60W/ch; danish kit, bipolar), and Le Amp (TDA 7294V mosfet IC at 100W/ch), using his demo CD he was going to use at WCES. The preference was 104 > 103 > Aleph >= TDA 7294 >> Millenium. For price and performance, Le Amp is hard to beat (pre-assembled and ready to roll); for more money, the DIY Tripath was superior; I'd skip the Millenium (the kit was a fair amount of work and the effort wasn't worth the results). (As for kit building, the Tripath is relatively simple, just add a power supply and chassis.)

This was not necessarily a fair comparison: powers were different (the Aleph was underpowered, but more musical than the ones it beat despite their greater power; I would think the greater powered Alephs or NP's newer designs would probably beat the Tripath). The interesting feature was all had different designs or output devices and they sounded different and displayed different levels of control.
 
Thanks Robert for your lengthy response.
I have had lengthy sessions with an Aleph 0, and although very nice did not quite do it for me.
With my engineering and ecological ideologies, I can not and will not, abide the terrible efficiency of the NP designs.
90% + efficiency seems rather more ideal to me.

Regarding transformers, yes many in pro audio are going back to line level transformers - indeed a PA hire colleage insists on using TX coupled gear in his live work.
Also a 30yrs experienced muso friend commented to me that why is it after recording and mixdown, that the final 2 track master has to go through a finaliser box (internal TX coupling) to undo digital harshness !.
He hates the sound of digital recoding !.

750/4 is pretty serious !
I have always found that a big clean amp beats a small clean amp.
Thanks for you appraisals - The Tripath soloution seems good to me for the application I have in mind.

Regards, Eric.
 
hi.

robert , what fets are you using in your 0104 amp?

the 0104 and 0103 is the same chip , the 0104 just has a higher voltage rating and im a bit puzzled you seem to find that the 0104 sounds better.

the 0103 with lower voltage and lower gate-charge fets outperforms the 0104 in everything but the current capability (and even this doesnt seem to have too much influence on the lo bass performance).

i agree that the jensen transformers can solve problems with noise and hum but it also adds to the overall sound of the system (not to mention the cost), and if you dont have the problem you may not need to cure it....

does your driver chip and the fets get kind of hot? ( i think i have a qualified guess....)

did you measure the actual efficiency? (for normal listening it could be closer to 50% than to 90%) ;)


it would have been interesting if your "test" had included a few more amplifiers but thanks for sharing anyway....

bye k madsen - www.cadaudio.dk / pwmaudio

re. the b&o modules it sounds like they were not the same we listened to :)

ps, we are discussing here if there would be a market for high quality class-d/pwm amplifiers (in kit or module form) , please give me a bit of feedback if you can in this respect.
 

kuribo

Member
2002-01-13 9:19 am
digital amp shoot-out....wouldn't it be nice?

Recently there have been many new digital entries to the market: there is the new Tact amps coming soon, the PS Audio digital amp is out, the Icepower amp from AV Reality, and of course the Bel Canto Evo (new version coming soon), Veritas amp, and Spectron. As usual, they all claim to be the be all end all; I would be very interested in some kind of comparison between all of these; anyone know if this would be at all possible to work out?
 
hi.

just saw the av reality site ;

im not sure the intention was to be amusing nevertheless.....

k madsen - cad audio dk

ps. there is more to good sound than good static measurements , a lot more ;)

ps. being biased of course i still think these is a bit of interesting info in my posting at the av reality board titled "listening tests"...
 
hi.

ok i have been told that the av reality forum is "private area" , hmm. a bit strange for a msg board...

seems he is a bit sensitive to comments about comparisons between b&o icepower boards and our boards , comparisons with the designer of the b&o boards present and with a result that goes to show that good (or better) specs isn't the same as good or better sound quality :)

carl , thanks for the nice words, about tweaks i think the subject was up here some time ago and i suggest that you work a bit with the "std" board first (they are quite ok)

a few tweaks could improve (or at least change) the overall sound quality, basically i think the power supply plays an important role in this (as in any) amplifier, good quality transformer, fast rectifier diodes, good decoupling caps "almost anywhere" with a low path to center ground is good practice.

bye k madsen - www.cadaudio.dk
 
whats wrong with people

hi.

i have had an "interesting" mail talk with peter from acoustic reality.

i asked on his board if he had made a/b comparisons with other types of pwm amplifiers (like we have here) or if he has an interest in such comparisons.

i frankly think that the results we had was a bit surprising even more so for the designer of the icepower boards (he was present at one of the tests and it was very relaxed and friendly)

you frankly wouldn't believe the load of bull i got from peter (acoustic reality) , a glimpse on his msg board could give you an indication.

i dont know him , he doesnt know me , did that stop him from calling me a liar , finding the lowest motives for my posting etc.
no sir!!

good luck to anybody thinking of dealing with him is all i can say....

bye k madsen - www.cadaudio.dk
 
Hot air and Icepower ?

Ok Kim, let's have it, let's have the evidence of your discussion with Peter of Acoustic Reality. :)
I looked on the AR site and could not find this discussion - did I look over it ?.
I am (and I am sure many others are) keen to hear of comparisons between your boards and the Icepower modules.(and Peters responses).

Regards, Eric.

BTW - I know the OEM prices for the Icepower modules, so to me the complete eAR amplifiers seems overly seriously expensive.