*** The DIY Audio Thread ***

[ChrissyT88]

Mmm... amp6 build has not gone too well - one channel worked brilliantly, the other, er, not so... A lot of fiddling and an instance of smoke later and i think it may be dead. Gonna pick up some pcb cleaner and a decent multimeter and see if i can breathe some life into it, but i think it may have had it... . I have put an order in for another, and hopefully this will go a little better (no doubt my soldering skill has increased). An hey, if i can get the first one to work, i'll have 2!

Whilst it was working though it did sound really good, even through some bits of bell wire. Dug some ancient mordant short speakers out of the loft for testing and id say it was a definite improvement over my current Denon micro system, and sounded good enough to make me want to try again!

On a side note: Mike, i see your location says 'between bath and bristol' - have you been to paul green hi-fi in Bath? I was wondering whether it may be worth taking a trip up there to see what they have speaker wise... I went to sevenoaks and tried out some Monitor audio/B&Ws and they were both pretty good.

 

[adamau5]

where was the smoke? - main chip?

 

[MikeHunt79]

Mmm... amp6 build has not gone too well - one channel worked brilliantly, the other, er, not so... A lot of fiddling and an instance of smoke later and i think it may be dead. Gonna pick up some pcb cleaner and a decent multimeter and see if i can breathe some life into it, but i think it may have had it... . I have put an order in for another, and hopefully this will go a little better (no doubt my soldering skill has increased). An hey, if i can get the first one to work, i'll have 2!

Whilst it was working though it did sound really good, even through some bits of bell wire. Dug some ancient mordant short speakers out of the loft for testing and id say it was a definite improvement over my current Denon micro system, and sounded good enough to make me want to try again!

On a side note: Mike, i see your location says 'between bath and bristol' - have you been to paul green hi-fi in Bath? I was wondering whether it may be worth taking a trip up there to see what they have speaker wise... I went to sevenoaks and tried out some Monitor audio/B&Ws and they were both pretty good.

I've never been there I'm afraid, the last time I bought some speakers was at Richer Sounds in Clifton (Bristol), they had quite a few nice looking speakers, mainly mordant short ones, I went for some satillite ones that were on offer. I've heard quite good things about Monitor audio tho, so it may be worth auditioning some of them. I doubt they would let you connect up a homebrew amp tho.

By the sounds of it you may have released the magic smoke on your amp6. If you do order another kit, also order another tripath chip, that way you may be able to replace the chip and get your first board going also. I'm surprised you cooked it tho, they are meant to be pretty robust!

Also, have a look at the 41Hz.com forums, they aren't amazingly busy but theres a lot of good troubleshooting info on there which helped as my amp6 didn't work the first time I plugged it in.

Also, what PSU are you using with it?

 

[Dr.EM]

Hey MikeHunt79, thanks for the link, some useful info in that thread. May well end up using the PGA3210 chip. Expensive, but they are dual so only need 3. Hopefully a freind can help with controlling it as I don't do PICs lol, and also get PCB developed.

Sorry, it was the midrange drivers with fs 250hz, they are these;
http://www.hautparleur.fr/_audax/hm100z0.jpg
and I have about the last ones in the country by the looks of it
Bass drivers are indeed 26hz.

All pass filters, thats the ones. Saw them on here, really useful site:
http://www.linkwitzlab.com/filters.htm#4

 

[ChrissyT88]

Slight success - its not dead. The channel that worked still does, and the other channel still works a much lower volume.

AdamW - er, im not actually too sure where the smoke came from. There is a cap that looks a little, rough, although i may have hit it with the iron. Since it is very close to the chip, i wasnt actually sure of the source. I was more concerned about turning the thing off! Strangely though it didnt seem hot, and neither did the chip...?

Mike - Unfortunately they dont have any more of the chips in stock, but they have kits, so i ordered another in case this one doesnt work. Personally, im not too surprised if its dead - i am pretty poor at this, but want to learn! I may try and get hold of a cheap kit from the high street electronics store to have a go at before a new kit arrives. If anything, it has been a learning experience, but i am very annoyed that it hasnt worked.

The power supply was one of the ones from the bay - a Skynet 8080 SMPS, that has 12v and 5v lines and is capable of 6A on the 12v line. I read online that it is best for the longevity of the psu for the 5v line to draw some power, so a 10ohm resistor is connected across the 5v line so that it draws roughly 1A. When its on, it is giving me 12.5-12.8, which i think is well within the spec of the chip.

The manual says to check if there is a 12v dc offset at the output if one channel is significantly quieter than the other, and says if there is that it is likely a transistor in the chip is dead, and its the end... I am i right in thinking i can measure this by just connecting the multimeter across the speaker terminals (+ve and -ve) when no input/output is connected? I got a decent multimeter this evening, and doing this gives numbers of around 0.5-1 in the mV scale (i think - i gave it about a minute to settle, and it drops from something significantly higher to something very small). If this is correct, this would suggest that there is nothing wrong with the chip. Certainly when running the voltages going to each terminal are between 6.11v and 6.23v, so the lack of volume (to me) would suggest a lack of current rather than voltage.

In general most of the voltages are correct - i get 2.4v on the input (the manual says about 2.5), and i get 5v over c2, and 1.12 over r7 (the manual says about 1.2). However, the manual says i should get 10v across c5 (there for charge pump output decoupling), but im reading 12 - so something is wrong somewhere. I cannot see how this is joined to the rest of the circuit, however.

My soldering in general is not brilliant, and after cleaning i can see that there are a few areas that need to be touched up, but its quite late and the light in here is poor, so i think that can wait for tomorrow. Certainly is anyone could let me know how to correctly measure DC offset, i would be most grateful.

As for the shop, i may venture as far as bristol... I was quite impressed by the monitor audios - they outshone the B&Ws for everything bar a metallica cd they had lying around in the shop, and metallica performance is quite a biggie for me! I was going to go again this weekend and give them a proper audition, so, we'll see. I did mention that there was a possibility i would be using them with a home made amp, and the bloke smiled, and im not sure he could take me seriously after that...!

Phew, long post. Thanks very much for reading, any help would be much appreciated.

 

[adamau5]

ok. I built an amp 6 and although through hole it was a troublesome build. The reason why is the board they use. They are notoriously tough to solder too - there is some sort of layer that has to be burnt off with the iron.

If you only have one channel then i would say look at the inductors. I have trouble here.

First thing is check the suspect cap. If its one of the tantalums then it may have shorted. check its resistance with you dmm.

 

[MikeHunt79]

Hey MikeHunt79, thanks for the link, some useful info in that thread. May well end up using the PGA3210 chip. Expensive, but they are dual so only need 3. Hopefully a freind can help with controlling it as I don't do PICs lol, and also get PCB developed.

Sorry, it was the midrange drivers with fs 250hz, they are these;
http://www.hautparleur.fr/_audax/hm100z0.jpg
and I have about the last ones in the country by the looks of it
Bass drivers are indeed 26hz.

All pass filters, thats the ones. Saw them on here, really useful site:
http://www.linkwitzlab.com/filters.htm#4

Nice drivers by the looks of the datasheet, they should sound good once it's finished. Be sure to keep us posted on how it goes.

Slight success - its not dead. The channel that worked still does, and the other channel still works a much lower volume.

Nice, the chip is probably ok. If it was toast I think it wouldn't work at all. I suggest check all your connections, plus use a bright torch or lamp to check there are no shorts. Also, if it's really quiet on one channel, it could be the zobel (output) resistor. Check that this has no burn marks on. Also, it wouldn't hurt to make a thread on the 41Hz.com forum. You may not get a reply straight away, but there are a few people on there that really knnow thier stuff.

Mike - Unfortunately they dont have any more of the chips in stock, but they have kits, so i ordered another in case this one doesnt work. Personally, im not too surprised if its dead - i am pretty poor at this, but want to learn! I may try and get hold of a cheap kit from the high street electronics store to have a go at before a new kit arrives. If anything, it has been a learning experience, but i am very annoyed that it hasnt worked.

I feel your pain, I've had similar thing happen in the past. I didn't know that they've run out of stock of the chips, but it's not suprising as Tripath have gone bust, so the chips are no longer being made.

Getting some random kit should be a good way to practice your soldering, plus if it works you know you're going something right.

The power supply was one of the ones from the bay - a Skynet 8080 SMPS, that has 12v and 5v lines and is capable of 6A on the 12v line. I read online that it is best for the longevity of the psu for the 5v line to draw some power, so a 10ohm resistor is connected across the 5v line so that it draws roughly 1A. When its on, it is giving me 12.5-12.8, which i think is well within the spec of the chip.

Nice, I just wanted to check as some 12v PSU's give a higher voltage with low load. That SMPS is perfect, as should always give a solid 12v out.

The manual says to check if there is a 12v dc offset at the output if one channel is significantly quieter than the other, and says if there is that it is likely a transistor in the chip is dead, and its the end... I am i right in thinking i can measure this by just connecting the multimeter across the speaker terminals (+ve and -ve) when no input/output is connected?

Almost, you need to short the inputs, the easiest way of doing this is by building a 3.5mm plug with all the pins joined togther in the plug. With this plugged in, then meansure the voltage of your speaker terminals (+ve and -ve) on DC mode on the meter. It should be less than 100mV, the lower the better. If it's over 500mV, don't plug it into any speakers otherwise it's bye bye voicecoil.

As for the shop, i may venture as far as bristol... I was quite impressed by the monitor audios - they outshone the B&Ws for everything bar a metallica cd they had lying around in the shop, and metallica performance is quite a biggie for me! I was going to go again this weekend and give them a proper audition, so, we'll see. I did mention that there was a possibility i would be using them with a home made amp, and the bloke smiled, and im not sure he could take me seriously after that...!

Hehe, I think people who work with or use only commercial stuff think us DIY'ers are a little eccentric. There are commercial amps that are similar to the Amp6 tho, some of them are pretty pricey but it would be good if they had one in the shop that has the Monitor Audios...

 

[Col_M]

Hi, the soldering experience will help a great deal. Unless you plan on soldering SMD parts you shuold have no problems.

The diyaudio wiki has some good info, but far from complete:
http://www.diyaudio.com/wiki/

Have a look on the forum also, there is plenty of info there, have a look at existing projects for some inspiriation...

Cheers, I've had a quick look while I was at work but will have a better look now

 

[ChrissyT88]

Thanks for the advice guys - I'll give the soldering a good going over tomorrow and let you know what's going on. Adam, thanks for the inductor tip, I will check it and cheers for the DC offset information.

 

[ChrissyT88]

Success! I had a closer look at the inductors and you were right - one of them wasnt properly connected (although i must admit, it looked like it was joined correctly, but the multimeter, but the multimeter showed it up as a poor joint). Both channels now function correctly (or at least at the same volume). Thanks very much for the pointers guys - it sounds really good!

I also measured the DC offset (properly this time - i have actually bee using rca input jacks so shorting the inputs was really rather easy), and recorded about 3-4 mV on one channel, and roughly 60 mV on the channel that has been dodgy. I understand that this is an acceptable level of DC offset, although is by no means brilliant on one channel. It certainly hasnt yet blown any speakers. I think i mentioned that i has ordered a second amp in case of failure, and i still plan on building this, hopefully to a higher standard, and hopefully will have the choice between 2! I have been looking at the 41hz forum, and there are some suggested mods, so i may try a few of these out as well once the second is up an running.

One small follow-up question - the manual states that a heatsink is needed for continuous use, and for testing i have been using the sink from an old AGP radeon gfx card w/ some arctic mx2 paste. I do not know the C/W rating of the sink, but its a fin array measuring about 4 cm x 4 cm. Do you think this will give adequate cooling, or will i have to butcher the sink from an old athlon system?

Once again, thanks very much guys - you have helped make me very happy this morning!

 

[MikeHunt79]

Success! I had a closer look at the inductors and you were right - one of them wasnt properly connected (although i must admit, it looked like it was joined correctly, but the multimeter, but the multimeter showed it up as a poor joint). Both channels now function correctly (or at least at the same volume). Thanks very much for the pointers guys - it sounds really good!

I also measured the DC offset (properly this time - i have actually bee using rca input jacks so shorting the inputs was really rather easy), and recorded about 3-4 mV on one channel, and roughly 60 mV on the channel that has been dodgy. I understand that this is an acceptable level of DC offset, although is by no means brilliant on one channel. It certainly hasnt yet blown any speakers. I think i mentioned that i has ordered a second amp in case of failure, and i still plan on building this, hopefully to a higher standard, and hopefully will have the choice between 2! I have been looking at the 41hz forum, and there are some suggested mods, so i may try a few of these out as well once the second is up an running.

One small follow-up question - the manual states that a heatsink is needed for continuous use, and for testing i have been using the sink from an old AGP radeon gfx card w/ some arctic mx2 paste. I do not know the C/W rating of the sink, but its a fin array measuring about 4 cm x 4 cm. Do you think this will give adequate cooling, or will i have to butcher the sink from an old athlon system?

Once again, thanks very much guys - you have helped make me very happy this morning!

Nice, I'm glad you got it working.

60mV is nothing to worry about in terms of cooking voicecoils, I've got 42mV on another one of my amps and have no problems. Checking DC offset is a good idea with any amp tho, be it commercial or DIY.

Finally, the heatsink. What speakers are you using? You only really need a heatsink with 4ohm speakers, this thing gives off very little heat.

Your 4x4cm heatsink will be fine. Better to have it than not. If you want, find some 4ohm (or 6 ohm) speakers, crank it up with some loud music, the heatsink will only get warm (if that!).

These chips also have over temp protection, but you'd only have this happen if you used no heatsink at all.

EDIT: This chip is 90% efficient, and at peak power (sine wave?) it will kick out 50W. So that's 5W of heat, worst case scenario. This is often why people just use an Alu chassis as a heatsink.

 

[adamau5]

my chip has honestly never got much above ambient, even cranked up its barely warm - thats with no sink.

Thought it wwould be the inductors. IF you dc offset i would look at the caps - they should block all of it.

 

[ChrissyT88]

Mmm... seems there may be some slight reliability issues with the terminal joints - they seem to have gotten worn and need re-doing (curse my poor soldering). However, yeah, it still works - using some old speakers that i think are 6 ohm (although have tested with a pair briefly that are 6 ohms) and its not getting warm - i did smell burning and thought something terrible had happened but it turns out it was the resistor set on the 5v rail melting a piece of wire on the desk. I may get an uprated resistor to help with the temp issue. Its a little off putting when you walk into the room and it smells 'warm', but i guess this is a problem that can be easily solved.

Since my second is one the way, i have been looking for possible mods. I understand that changing the caps and inductors is one of the best ways to change the sound (also easiest), but as i am new to this, obviously i have no experience. Have you guys replaced the caps at all?

EDIT: I also spent some time this afternoon looking for some preamp kits (not sure if preamp is the right word - i really would only like to have input select and volume control). I guess i would like to replace the amp i am currently using with a DIY solution, and that means it needs some additional functionality! Some folks on DIYaudio (im not a member) had mentioned some kits by Dantimax, and these would seem to do what i am after, but i can see that potentially they could be difficult to build. Has anyone bought a decent preamp kit that they could recommend?

 

[adamau5]

aikido!!!!!

meant to be awesome preamps.

Only issue is, get it wrong and its 200vdc you are playing with.

 

[Mr. Brightside]

Finished soldering up an Alien DAC the other week. Plugged it in, not detected.

This is my first time doing SMD work and the result is pretty embarrassing tbh.

My suspicion is that the regulators (IC2 & IC3) have been heat damaged because I made a mess of my first board and had to desolder them so I could transfer them to a new board.

Can anyone suggest where to start with troubleshooting it?

 

[MikeHunt79]

^ Would it be worth trying to get it to work unregulated? Run straight from the 5v USB power?

 

[Mr. Brightside]

OK I'm officially an idiot, misinterpreted the assembly instructions; I had intended to build it in unregulated USB configuration.

Just getting out the soldering iron now... will post back in a bit.

Cheers

 

[MikeHunt79]

Kk, good luck. You've done more than me... Mine still sat in a mint tin, totally unsoldered. I really need to make start but the whole SMD thing is putting me off.

 

[p4radox]

SMD's not too bad, as long as you have a fine tipped iron, some tweezers and a flux pen. And a steady hand helps quite a bit too...


Anyway, some goodies arrived this morning:

AMP10 kit, all the way from Sweden.

cheap DAC, all the way from Hong Kong.

Black PCBs all round. \o/

Time to get building I think. Ill have to put in a Farnell order at some point, when I finally decide upon all the stuff I'll be needing. I've run out of a few basics.

 

[Mr. Brightside]

OK, I've now correctly configured it in unregulated USB mode. Didn't work at first so I had to check the voltages and found a dry joint on L12. Fixed that and it's now working!

Haven't had chance to properly assess the quality yet... need to move things like toolbox etc. out of the way of speakers, but so far it seems pretty good. Will try out ASIO driver then aswell.

Just need to drill and file holes in the enclosure now then it's all done. Will put another pic or two up then.

Thanks for the pointers guys