*** The DIY Audio Thread ***
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Soldato
Dr. EM: Looking good. I'm also trying to sort out some sort of DIY 2.1 system as my computer speakers, so I'll be interested to see how you get on. 
Mike, thats cool, whats your requirement for them? I can't take big Hi-Fi gear to a student house but want something decent and compact. Unfortunately most commercial offerings are built very poorly and DIY is more fun!
The B3N's that I'll use for satellites (match the sub too
) are big enough and have suitable response to reach the sub crossover frequency leaving no typical low-midrange dropout; the buyoff being maximum output due to the inherent low sensitivity of such a driver. This isn't a problem for my application. Another potential issue with them is off axis response, the treble does dull off axis since these are relatively large drivers to cover up to 20khz (3"). If these arn't big issues then I'd reccomend them though, what i'm hearing so far is very clear and detailed, voices sound great
The B3N's that I'll use for satellites (match the sub too
) are big enough and have suitable response to reach the sub crossover frequency leaving no typical low-midrange dropout; the buyoff being maximum output due to the inherent low sensitivity of such a driver. This isn't a problem for my application. Another potential issue with them is off axis response, the treble does dull off axis since these are relatively large drivers to cover up to 20khz (3"). If these arn't big issues then I'd reccomend them though, what i'm hearing so far is very clear and detailed, voices sound great Those valves look sweet Adam. Very tidy work with the PCBs too, makes the high voltage issues less of an issue I guess!
So, does a valve rectifier sound different to a silicon one? I understand that thier behaviour varies under different loads unlike a silicon bridge. A college tutor had one in his guitar amp and said it improved the sound.
So, does a valve rectifier sound different to a silicon one? I understand that thier behaviour varies under different loads unlike a silicon bridge. A college tutor had one in his guitar amp and said it improved the sound.
well, i dont know yet. but apparantly it has very soft switching charateristics, which mean ultimtaley means less work for the caps to do.
The big advantage is the slow startup. It takes about 5 secs for the rectifier to warm up and pass the hgih voltage. This means the amp boards wont see the massive 260v until they too are warm.
If i used a sand recitifier then i would have had to build a delay circuit. The valves cant take 260v without the heaters active.
The big advantage is the slow startup. It takes about 5 secs for the rectifier to warm up and pass the hgih voltage. This means the amp boards wont see the massive 260v until they too are warm.
If i used a sand recitifier then i would have had to build a delay circuit. The valves cant take 260v without the heaters active.
Soldato
Well right now I'm sort of halfway there, I already have some Mordaunt-Short MS302 satillites which are pretty similar to the B3N's I imagine, apart from that they are 2-way (3" mid, + tweeter), but they sound quite nice when connected up to the Amp9B.Mike, thats cool, whats your requirement for them? I can't take big Hi-Fi gear to a student house but want something decent and compact. Unfortunately most commercial offerings are built very poorly and DIY is more fun!
The B3N's that I'll use for satellites (match the sub too
My sub right now is a Mission active sub with 8" driver. It's nasty! Lots of port noise and I get 50Hz mains hum thru it so this is the next thing to replace. I'm looking at building a smaller tapped horn that will hopefully go down to 30Hz, and I also need to make a proper crossover as the one on my soundcard is pretty poor. I'll probably so something op-amp based and crossover around 100Hz depending on how much bandwidth the sub has. Powering the sub won't be hard as I have 2 unused channels on my amp 9.
Right now I'm just happy to have a working system but I'm slowly improving it piece by piece.
Soldato
Just got my cmoy in an enclosure...changed out the power caps for 1500uF Sanyo WG and the bass seems tighter at high volumes The sound is very good through my HD-580s...I was expecting some background noise but there really is none at all! And it's running from the line-out on my onboard P5Q deluxe sound 
I have an ebay DAC that's arrived here so that's my next thing to do.
Quite pleased for my 1st project I did mess up on the LED hole though, made it too big. I might look for a larger LED to fill the hole up some more.
The sound is very good through my HD-580s...I was expecting some background noise but there really is none at all! And it's running from the line-out on my onboard P5Q deluxe sound I have an ebay DAC that's arrived here so that's my next thing to do.Quite pleased for my 1st project
I did mess up on the LED hole though, made it too big. I might look for a larger LED to fill the hole up some more.
Soldato
Thanks. And yeah my next amp project is a Millet Starving Student hybrid amp. The parts should be here next week I'm eager to hear something tube powered as I hear the HD 580s really show their true colors with tubes.
I'm eager to hear something tube powered as I hear the HD 580s really show their true colors with tubes.yes, although the starving student is a littlebit tame for the senns. Its stunning with grados, but i think you will loose a bit of top end sparkle with the Starving student.
saying that, it will be a lot better than the cmoy - and for £30 its unbeatable.
saying that, it will be a lot better than the cmoy - and for £30 its unbeatable.
I've got my Amp6 working, been listening to it all week and i can't believe the sound quality coming out of it, it's much better than my Yamaha AV amp! I know people said that AV amps are no good for music, but i didn't expect so much difference.
I've been bitten now, i want to build some thing else.
I need some help with my DAC though.
When i connect the RCA's to the input of the amp, the volume is to loud, even with every thing turned down.
I removed the op-amp from the DAC which lowered it a bit, and also wired in a 50k pot between the DAC and amp, but it only goes up and down a little (not sure if it's wired correctly).
If i plug the DAC into my AV amp, then use the pre-outs to my Amp6, everything's fine, but i would prefure not to use my AV amp.
Could someone point me in the right direction please.
I've been bitten now, i want to build some thing else.
I need some help with my DAC though.
When i connect the RCA's to the input of the amp, the volume is to loud, even with every thing turned down.
I removed the op-amp from the DAC which lowered it a bit, and also wired in a 50k pot between the DAC and amp, but it only goes up and down a little (not sure if it's wired correctly).
If i plug the DAC into my AV amp, then use the pre-outs to my Amp6, everything's fine, but i would prefure not to use my AV amp.
Could someone point me in the right direction please.
Soldato
I've got my Amp6 working, been listening to it all week and i can't believe the sound quality coming out of it, it's much better than my Yamaha AV amp! I know people said that AV amps are no good for music, but i didn't expect so much difference.
I've been bitten now, i want to build some thing else.
I need some help with my DAC though.
When i connect the RCA's to the input of the amp, the volume is to loud, even with every thing turned down.
I removed the op-amp from the DAC which lowered it a bit, and also wired in a 50k pot between the DAC and amp, but it only goes up and down a little (not sure if it's wired correctly).
If i plug the DAC into my AV amp, then use the pre-outs to my Amp6, everything's fine, but i would prefure not to use my AV amp.
Could someone point me in the right direction please.
Which DAC are you using?
You might find some strange things happening if you put the pot between the DAC and the amp, related to impedance matching.Maximum power is transferred from one stage to the next when the output and input impedances match, so using something like a 50k potentiometer could throw the impedance way out of line if the input impedance of the next stage is something much lower or higher.
A buffer might be what you need, or just to put the pot at the earliest possible stage.
Soldato
p4radox....I'm a bit confused regarding this circuit. In the tangentsoft article he says "For now, assume that it's better to have just one before the active "rail splitter"." Then at the end of the article he talks about disadvantages of putting caps across the output and vGround...but I got confused.
Do I want caps on the output or just a single on the input? I see you have two? :/
I'm using the "Chinese" DAC, the same one as Damian666.
It says you can use a 50k pot in the assembly instructions for the amp, but I'm not sure if I've done it correctly.
Soldato
Gurusan: this is my project log if it's any use:
http://forums.overclockers.co.uk/showthread.php?t=17860076&page=3&highlight=cmoy
This is my circuit as it ended up:
The two black electrolytic caps you can see in the photo are simply in parallel across the battery input, to give better "big hit" response. Not sure if they made any difference really.
edit: the large blue caps are 0.1uF coupling caps to prevent DC offset reaching the op amp circuit. They allow the AC sound signal through though.
http://forums.overclockers.co.uk/showthread.php?t=17860076&page=3&highlight=cmoy
This is my circuit as it ended up:
The two black electrolytic caps you can see in the photo are simply in parallel across the battery input, to give better "big hit" response. Not sure if they made any difference really.
edit: the large blue caps are 0.1uF coupling caps to prevent DC offset reaching the op amp circuit. They allow the AC sound signal through though.
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Soldato
That's the one I'm playing with too. It'd be easy to simply stick the pot between the DAC and the op amp output stage, if it wasn't for the fact that the output stage uses a differential amplifier with 4 inputs! I'm going to simply disconnect the output stage and build a separate preamp/headphone amp which will then feed my power amp.
Like I said earlier, I think the best thing to do would be bypass the output stage on the DAC. Take the ouputs from R- and L- and feed them through the potentiometer. Then place a buffer between there and your AMP6.
Something like this:
Which would hopefully bypass the problem of impedance matching. It's what I'm thinking of doing with mine.
Soldato
Not stupid at all, the jargon is the worst part about electronics.
A buffer is basically an op amp with negative feedback and a gain of 1. In theory it does nothing to the signal, simply passes it from one circuit to the next, without giving you the problems of "impedance matching". If you remove the DAC's output stage, you can use the op amp from it as the buffer if you like. Personally I'd recommend a better op amp like an OPA2132.
For the potentiometer you should wire it as shown. The signal comes in one side and out of the "wiper". The other side is grounded to a ground point on the DAC board, I think middle pin on the ribbon cable is marked "G" for ground. It acts as a potential divider: as the wiper moves "up", a greater proportion of the signal's voltage is dropped across the wiper and the next part of your circuit, thus increasing the volume.
edit: I should add that I'm not certain this will work, and it may need some tweaking. But it's almost identical to what I'm planning to do with mine.
A buffer is basically an op amp with negative feedback and a gain of 1. In theory it does nothing to the signal, simply passes it from one circuit to the next, without giving you the problems of "impedance matching". If you remove the DAC's output stage, you can use the op amp from it as the buffer if you like. Personally I'd recommend a better op amp like an OPA2132.
For the potentiometer you should wire it as shown. The signal comes in one side and out of the "wiper". The other side is grounded to a ground point on the DAC board, I think middle pin on the ribbon cable is marked "G" for ground. It acts as a potential divider: as the wiper moves "up", a greater proportion of the signal's voltage is dropped across the wiper and the next part of your circuit, thus increasing the volume.
edit: I should add that I'm not certain this will work, and it may need some tweaking. But it's almost identical to what I'm planning to do with mine.
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