*** The DIY Audio Thread ***

[Founder_film]

The holes were not too bad to cut, I used a stepped bit going from 4 mm to 22 mm. Just used my cordless drill, worked a treat.

Okay here is an internal photo. The case is grounded via the stand off in the centre of the PCB, between the two tube sockets.

 

[Founder_film]

I have noticed that if I touch any part of the case, the hum note changes and gets quieter. I re-soldered the POT and made sure the centre ground stand off was secure but the hum is still there.

One tube is definitely still brighter

 

[Founder_film]

Photo of the tubes:

 

[Founder_film]

Shameless bump to see if anyone has any suggestions about my hum problem.

I have resoldered the pot ground wire and also taken a wire straight from the power socket ground to the case. Still get the hum

 

[p4radox]

I'm not familiar with the SSMH, but are the FETs (if that's what they are) correctly isolated from the chassis if they should be?

 

[saitrix]

I don't seem to be having any joy with it, does anyone have any suggestions for a first diy built dac? Has anyone modified one of those ebay dac's to improve them?

 

[p4radox]

I don't seem to be having any joy with it, does anyone have any suggestions for a first diy built dac? Has anyone modified one of those ebay dac's to improve them?

I've played with the "noodle" Chinese DAC, and have been using it for about 2 years or so. I bypassed the output stage and replaced a few caps, as well as enabling the high-bitrate mode (which I've never used...). To my ears it sounds excellent.

 

[saitrix]

How difficult was it to do? I'm trying to work out whether I'd be better to go for something like an AlienDac/BantamDac/GrubDac or modify something like that ebay dac's.

 

[Founder_film]

I'm not familiar with the SSMH, but are the FETs (if that's what they are) correctly isolated from the chassis if they should be?

Just took everything apart and checked all the connections to ground. Made sure there were no dry solder joints and also made sure the centre ground stand off was connected properly.

The FETs are properly insulated and isolated from the chassis.

Turned it on again and the hum is quieter but still there. The pot makes an interference type noise when I turn the volume up and down. Also I am using a different power supply to the one on the BOM. It is a wall wart style one and is "switch-mode" is that the cause of the hum?

 

[p4radox]

If it's a constant 50Hz hum then it does sound like a ground loop sort of issue. The only reason I mention the FETs is that I wondered if the bolts could be linking them electrically to the case, but I can't tell if you're using insulating washers.

You could perhaps try using a different pot?

saitrix: it was pretty straightforward, I followed this site:

http://www.lampizator.eu/lampizator/LAMPUCERA/CD DAC Lampucera lampizator.html

It's mostly surface-mount, which is easy if you're careful.

Although I love it, you might find it more fulfilling building something from scratch like the Alien or GrubDAC.

 

[Yaka]

you know it just hit me, i did the same thing with the beta board rather than solder directly on to the board i whent down the wire way, think you need to put the resistor on one of the fet legs rather than on the board, i think there are r3 and r9 which should not be on the board but on one the fet legs

 

[Founder_film]

If it's a constant 50Hz hum then it does sound like a ground loop sort of issue. The only reason I mention the FETs is that I wondered if the bolts could be linking them electrically to the case, but I can't tell if you're using insulating washers.

You could perhaps try using a different pot?

I am using insulating washers on the FETs. Might see if I can source a different pot.

you know it just hit me, i did the same thing with the beta board rather than solder directly on to the board i whent down the wire way, think you need to put the resistor on one of the fet legs rather than on the board, i think there are r3 and r9 which should not be on the board but on one the fet legs

I will try this when I next get a chance to get my iron out, it seems like gurusan did this as well. I wish I could have soldered them straight to be board but their legs were too short and I kept making mistakes with the case work.

 

[Dr.EM]

You have 2 routes to ground that I can see. One via the cable connecting to the PCB (black cable) and one through the case directly to the DC jack which isn't isolated from it. This exact issue caused hum on my crossover prototype, insulating the DC jack eliminated it, however that run from AC power.

Still, worth a try. Disconnect the black cable to see if it reduces the hum, if it does then reconnect it and isolate the DC jack from the case

 

[Founder_film]

You have 2 routes to ground that I can see. One via the cable connecting to the PCB (black cable) and one through the case directly to the DC jack which isn't isolated from it. This exact issue caused hum on my crossover prototype, insulating the DC jack eliminated it, however that run from AC power.

Still, worth a try. Disconnect the black cable to see if it reduces the hum, if it does then reconnect it and isolate the DC jack from the case

Ah yes I see that now! Just ran back through the SSMH build instructions, looks like they have used an insulator on the DC jack. Thank you for bringing it to my attention

 

[MikeHunt79]

This thread seems to be a bit unpopular now!

In my defence, I haven't been on OCUK much recently, for once it's been sunny outside so I've been making the best of it.

Anyhow, the speakers to go with the above amp are just finished:

[mg]http://img716.imageshack.us/img716/2849/finishedpair2.jpg[/img]
[mg]http://img694.imageshack.us/img694/5478/finishedpair3.jpg[/img]

Full details here:

http://www.diyaudio.com/forums/full-range/165604-unusual-design-desktops-wedge.html

Nice job, I've heard good things about those Monacor drivers, and by your comments it looks like they live up to the hype! I'd be quite tempted to try adding a sub even just as an experiment, you may be surprised what a difference it can make... It does add complication though, can I can appreciate the benefits of all your sound coming from a single source (like headphones).

I'm tempted to get a pair as I want to make a (tiny) boombox type thing, can I ask where you got them from? I have yet to find a UK source but I've heard that the same driver may be sold under another brandname but I'm not sure what it is!

Shameless bump to see if anyone has any suggestions about my hum problem.

I have resoldered the pot ground wire and also taken a wire straight from the power socket ground to the case. Still get the hum

What pot are you using? I've that with some of them the metal case can act as shielding, and in this case I've soldered a ground wire to the case and this has reduced the noise floor, believe it or not! It's also worth reading Rod Elliots article on ground/earthing if your haven't already: http://sound.westhost.com/earthing.htm

Finally, I've finally got the TH wired up again, it's crazy the way it shakes stuff at the other end of the house! I should have some more pics of my 90% done active set up to post sometime soon, I'm still tweaking my setup, I seem to be one of this people who can't ever finish anything, it's just in a perpetual stage of tweaking!

 

[Dr.EM]

In my defence, I haven't been on OCUK much recently, for once it's been sunny outside so I've been making the best of it.

Don't blame you there! I try to as much as I can if people are around to go with.

Nice job, I've heard good things about those Monacor drivers, and by your comments it looks like they live up to the hype! I'd be quite tempted to try adding a sub even just as an experiment, you may be surprised what a difference it can make... It does add complication though, can I can appreciate the benefits of all your sound coming from a single source (like headphones).

I'm tempted to get a pair as I want to make a (tiny) boombox type thing, can I ask where you got them from? I have yet to find a UK source but I've heard that the same driver may be sold under another brandname but I'm not sure what it is!

They are really neat little fullrangers imo, good balance of parameters. I'd recommend the notch filter (as I am using on mine) for the 10kHz peaking, though in a boombox where you'll be off-axis mostly it may not be required. I may experiment with a sub at some point, I do already have one afterall!

The drivers will perform in small enclosures so your boombox should be viable. Mine came from the bay, "connect audio". I've seen a cheaper identical looking driver on a German site before too, but I can't remember the link!

Finally, I've finally got the TH wired up again, it's crazy the way it shakes stuff at the other end of the house! I should have some more pics of my 90% done active set up to post sometime soon, I'm still tweaking my setup, I seem to be one of this people who can't ever finish anything, it's just in a perpetual stage of tweaking!

Sounds good

 

[Founder_film]

Okay so I have tried insulating the DC jack on my SSMH. Still get hum. I have also moved R3 and R9 to the legs of the FETs from the PCB and still there is a hum.

Another thing I have noticed is that if I move my hand near to the tubes the hum gets louder, is that normal?

 

[MikeHunt79]

They are really neat little fullrangers imo, good balance of parameters. I'd recommend the notch filter (as I am using on mine) for the 10kHz peaking, though in a boombox where you'll be off-axis mostly it may not be required. I may experiment with a sub at some point, I do already have one afterall!

The drivers will perform in small enclosures so your boombox should be viable. Mine came from the bay, "connect audio". I've seen a cheaper identical looking driver on a German site before too, but I can't remember the link!

I ended up getting a pair from Germany in the end, at least I think the shop was German, it was called Europe Audio I think. I'm still waiting for them to arrive however, I'm not 100% sure I'm going to do a boombox type thing with them but I really want to see what half decent fullrangers sound like so I thought I'd give these a go.

FWIW, Someone at the 41Hz forum posted a quite a nice bit of info about some sort of notch filter, I think it involved using a trafo and a cap, I'll see if I can find the post.

Okay so I have tried insulating the DC jack on my SSMH. Still get hum. I have also moved R3 and R9 to the legs of the FETs from the PCB and still there is a hum.

Another thing I have noticed is that if I move my hand near to the tubes the hum gets louder, is that normal?

What power supply are you using? It sounds to me like something isn't properly earthed...

 

[Dr.EM]

Yeah, Europe Audio (formerly BMM Electronics) is the big distributor of drivers and associated components for Europe, based in the Netherlands I think. Pretty sure with postage and VAT they cost more from there than the ebay seller though? Hope you enjoy them, they have a lot of potential I think, about the least obstructed rear side of any 3" driver i've seen, which I think is important, along with the relatively high efficiency and smooth response. I have a 'spare' 4ohm one which I may try to correct the 2kHz broad peaking with some cone treatments on.

Here's the passive notch I used on my wedge speakers. I read the driver impedance at this frequency as closer to 12ohm and in practise I've found this notch works well, still plenty of high treble. You'll want to implement baffle step correction passively if at all (my wedges intentionally sit so close to the wall as to gain acoustic BSC).






Founder_film, that's a shame that didn't help, thought I might have nailed that there! Do you have any other power supply you could test with?

 

[MikeHunt79]

Yeah, Europe Audio (formerly BMM Electronics) is the big distributor of drivers and associated components for Europe, based in the Netherlands I think. Pretty sure with postage and VAT they cost more from there than the ebay seller though?

19% VAT. Still, they were £20.57 each before the VAT and delivery so they came to around £55 delivered so there's not much in it really! I did need a new other parts from there also so I decided to go with them. I went for 4 ohm versions myself, as all of my T-amps seem to work better with a 4 ohm load.

Speaking of T-amp's, I've recently ordered a 41Hz Amp7 kit, and so far I've soldered around 50% of the parts. I think it's safe to say I've been bitten by the bug! I'll upload some pics when I can find my card reader.

Here's the passive notch I used on my wedge speakers. I read the driver impedance at this frequency as closer to 12ohm and in practise I've found this notch works well, still plenty of high treble. You'll want to implement baffle step correction passively if at all (my wedges intentionally sit so close to the wall as to gain acoustic BSC).

Thanks for posting that notch filter, I'm guessing the notch filter may need different values with a 4ohm driver? I still need to work out what I'm going to do with them and what enclosure I'm going to use... I'm quite liking the Ikea bowl enclosures after seeing the thread over at DIY audio, but I haven't really decided on vented or sealed yet, I'm kind of leaning towards vented right now.