* The DIY Audio Thread *

Dr.EM · 29 Apr 2009 at 19:09

Well, there'd be loss of efficiency, but this will be minimal with a tweeter. Also reduced damping factor but again this shouldn't affect a tweeter too much. Make sure you're using a non-inductive resistor though.

If you were using a passive crossover it shouldn't make much difference except that tweeters are sometimes padded down in level, which is basically what you've done here (a more typical arrangement is an L-pad as opposed to a series resistor).

I am running tri-amplified. The hiss is a bit excessive but still not really audible at a distance. I hope with everything shielded more thoroughly and the proper volume control this will diminish; the amps themselves are rather quiet with grounded inputs at least.

p4radox · 29 Apr 2009 at 19:29

lol @ the clothes peg.

J1234 · 29 Apr 2009 at 22:04

Got the OPA Earth to go in my DAC today. It replaced the OPA 2604 in my Fubar II.

The OPAMP:

Extension lead:

Old OPA out:

Testing the new one, have earthed it too:

The top of the casing wont go on with it like that, hence getting the extension lead.

Isolated it with some tape, fitted the lead and stuck the case back together:

Apparently they require a while to burn in, but WOW is all I can say so far, made such an improvement. It really is a day/night change. The bass has tightened up and the mids are very colourful. Really impressed with the difference it has made.

speedyj said:
Yes I'd seen that, be interested to see how the new tubes alter things.

Have had the new Mullard EF95s in for a couple of days now, no more distortion at high volumes and is definitely a good improvement over the stock tubes. Soundstage has remained huge with really accurate bass. Much better than the EF91s I had in there to begin with.

p4radox · 29 Apr 2009 at 23:07

Oh sweet, a discrete op amp. How much did you pay for it?

What was the op amp it replaced? Have you compared it to any other "decent" op amps?

J1234 · 29 Apr 2009 at 23:14

It came to £30 inc EMS shipping from China, came in 4 days from Audio GD.

It replaced the OPA2604AP. I had tried dual OPA627s in there, but I couldn't notice any improvements so went for a discrete op amp instead which was recommended to be by someone who owns the same DAC.

It sounds like a different DAC to be honest, the sound is just amazing.

MikeHunt79 · 29 Apr 2009 at 23:37

Ooo, I like that big op-amp, I wonder how well it would work in the cheap Chinese DAC?

Dr.EM said:
Well, there'd be loss of efficiency, but this will be minimal with a tweeter. Also reduced damping factor but again this shouldn't affect a tweeter too much. Make sure you're using a non-inductive resistor though.

I'm not too worried about the loss of efficiency as the tweeters sensitivity now seems to match the woofer which is sort of a bonus as I can up the gain on my DCX2496 on the tweeter channels which gives better resolution on it's output.

I'm not sure if the resistor I used is non-inductive however, the part I used was farnell part number 4170751 which is no longer around but is a Vishay Enamelled Wirewound Resistor according to the datasheet, but no inductance rating is given in the datasheet. I'm guessing inductance would cause a strange frequency response? I guess I could measure this once I get to grips with ARTA...

Dr.EM said:
If you were using a passive crossover it shouldn't make much difference except that tweeters are sometimes padded down in level, which is basically what you've done here (a more typical arrangement is an L-pad as opposed to a series resistor).

Just googled L-pads, look a little more involved, I think I'll stick with this as it's nice and simple.

Dr.EM said:
I am running tri-amplified. The hiss is a bit excessive but still not really audible at a distance. I hope with everything shielded more thoroughly and the proper volume control this will diminish; the amps themselves are rather quiet with grounded inputs at least.

I've tried the same amp up to other speakers and it's not that hissy. I'm using the speakers as nearfield monitors at my computer desk, so am sat pretty close to them, worst case scenario I guess, this is why I'm trying to get rid of the hiss.

The speakers were originally bi-amped with a LM3886 circuit, and this gave much less hiss than my Tripath amp, but this may be due to the fact the the amps were originally inside the speakers so the speaker wires were very short...

p4radox said:
lol @ the clothes peg.

I do have croc clips but I found the clothes peg first!

p4radox · 29 Apr 2009 at 23:43

MikeHunt79 said:
Ooo, I like that big op-amp, I wonder how well it would work in the cheap Chinese DAC?

The entire output stage needs modification to be any good at all, a decent op amp would be wasted. I just bypassed it completely.

MikeHunt79 · 30 Apr 2009 at 00:24

p4radox said:
The entire output stage needs modification to be any good at all, a decent op amp would be wasted. I just bypassed it completely.

Gotcha, thought as much... I know someone who used some transformers instead of op-amps as an output stage and has had good results, it's good but a little daunting how many options there are for an output stage...

visibleman · 3 May 2009 at 14:36

Hi all,
has anyone purchased (or had experience with) the cMoy amps from the ebay seller 'biosciencegeek'?
Looking at purchasing one, but just wondering if the £40(odd) is worth it considering you can purchase the kit for a lot lot less. Although the review and ebay feedback suggests that it's very good.

Also, does anyone know places to purchase iPod LODs (uk if possible)? Has anyone used the ebay 'Hong Kong' iPod dock with jack socket connector?

cheers all

Yaka · 3 May 2009 at 14:49

he is a well known cmoy seller, his builds are very good. i got my first cmoy from him, lost it 2 weeks in fact, further 3 i built i lost as well. :/

as for ipod lods i got mine from Qable.com from B section with some visable scuff marks for £9 but when i use it on my iphone i get a airplane mode pop up

p4radox · 3 May 2009 at 19:43

Biosciencegeek makes excellent cmoys, and if you don't have any of the necessary components, tools or patience his amps are pretty reasonable value.

Cristian · 4 May 2009 at 12:24

I'm not sure if this is the right thread, but here goes.
I've ended up with a pair of speakers that were damaged during transit by the lovely parcelforce. One of them works fine, apart from the scratches in the corner, on the other the tweeter doesn't work, although both drivers look intact.
they are a pair of B&W 302.

Now, I'm gonna open them at work this week (haven't got hex keys here), haven't got that much experience in terms of electronics either, so I was wondering if it's okay to connect the tweeter and bass driver directly to my nad c315 to see if they actually work after I strip them down. the amp is rated 4-16 ohms, so should be okay but I thought I'd ask first before I make something go boom. If both do, then I'll probably have a dead crossover? Can I find one to replace that?

Dr.EM · 4 May 2009 at 12:31

Do not connect a tweeter directly to an amplifier! You may connect the woofer directly though. Hopefully it'll be something visible, like a broken connection to a driver or on the crossover PCB. They use a simple/minimal crossover I believe, it'll be attached to that rear connection plate

Cristian · 4 May 2009 at 14:23

well the tweeter seems the one not working, would there be any way to test it?
indeed the crossover looks kinda small, as I've removed the rear connection plate that has normal screws but it's glued lower on the wall that makes the back of speaker so I can't see or reach much of it, probably be more lucky looking from the front after removing the bass driver.

Dr.EM · 4 May 2009 at 16:44

If you have one by any chance, connect it in series with a capacitor of value 2-4.7uF, no larger. Ideally not electrolytic but metallised plastic. Keep signal levels low

Cristian · 8 May 2009 at 13:41

right, I opened everything up (not bad built quality, and damn they used a lot of insulation.

) and found out what the problem is.

in case somebody can't see, the wire is broken and soldering it in there would be rather... let's just difficult. provided I can find a tiny soldering iron(which I don't have) and manage to solder it without burning the foam around it, I don't know if it's would work either.

I've emailed B&W which have been surprisingly prompt and they said:

"You can purchase both parts directly from us.

The price for 1 x DM303 complete tweeter (diaphragm and magnet - ZZ12475) inclusive of carriage and VAT is £29.36.

The price for 1 x DM303 diaphragm (diaphragm only - ZC12475) inclusive of carriage and VAT is £19.57."

The magnet should be alright (any way to test it?), should I order the diaphragm or go for the whole tweeter? any idea if it's gonna come with the whole plastic part or not?
I'm sorry if this sounds rather noobish, but I've never built a speaker so I'm not that sure on technical terms.

Yaka · 8 May 2009 at 23:48

antec do very fine thin tips for thier soldering irons they may have what you need

p4radox · 9 May 2009 at 09:33

Yaka said:
antec do very fine thin tips for thier soldering irons they may have what you need

Do you mean Antex?

Most soldering irons can be bought with thin tips, although Antex tend to be the cheapest. This is reflected in their quality obviously, but if you don't plan on using it frequently then I'm sure it'd be fine.

Yaka · 9 May 2009 at 15:10

opps yes i meant antex. i didnt realise they are of questionable quality they tend to fail more than others?

Founder_film · 17 May 2009 at 14:22

I have finally completed my new PSU board for my gainclone. Etched the PCB at home using one of the cheapo kits you can get, worked out really well.

BEFORE:

AFTER:

Close ups of the PSU board:

A bit neater than with my old PSU boards done on strip board. Reduced the number of diodes too which is good on budget. Still think some of the wiring could be shorter but I don't think this effects performance too much.

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