*** The DIY Audio Thread ***

Ah ok, fair enough.

I'm still gonna go ahead with using the case as a heatsink, as long as I get hold of my Kapton pads soon.
 
p4radox said:
Ah ok, fair enough.

I'm still gonna go ahead with using the case as a heatsink, as long as I get hold of my Kapton pads soon.
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Yep I was going to use kapton pads also, but I don't have any and I didn't want to wait for them to be delivered... Plus my chassis is steel anyway, which makes a poor heatsink. :)
 
Amp9 inputs now rewired and it's sounding great. :cool:

Ok, I'm trying a new output stage for the DAC, but the blue transformer is getting a little warm for my liking, probably because I'm powering 6 op-amps from it....

Didn't someone (Damien?) use a different toroid to power the DAC? What secondary voltages did you get (9V?) and where did you get it? :)

Failing that, could I just use some sort of rail splitter from my 24V SMPS which powers my amp9?
 
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when you say a little warm, how warm? IF you can keep your hand on it, i wouldnt worry.

check the output is still under regulation, if so just leave it - as long as its fused not much will happen.
 
Adam W said:
when you say a little warm, how warm? IF you can keep your hand on it, i wouldnt worry.

check the output is still under regulation, if so just leave it - as long as its fused not much will happen.
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I can keep my hand on it, I'd guess around 40 - 50 degrees maybe?

It's still under regulation, and the voltage reg heatsinks are not hot also... I guess it's just the 7VA rating on the transformer that's worrying me a little. :)
 
Right my LM1875 kits (two mono boards) are waiting for me to collect at the royal mail distribution office :)

However I have a few questions. They need an input voltage of +/- 25V and they are 20W each, therefore what toroid should I be looking to buy? This might seem a stupid question but I am a novice ;)

Also I will need to make myself a rectifier right. Therefore can I just follow the schematic seen here with a different toroid to give me +/- 25V:

unreg_PS.gif


Also what smoothing capacitor values should I be looking at using?

I have loads more questions about this build so be warned! :p
 
You will need a toroid with dual secondaries, each of around 17-18V. This is because 18V * root2 = 25.5V (when rectified). I'm not sure about the smoothing caps, but I'd use a couple of GBU802 bridge rectifiers, rather than doing it with discrete diodes.:)
 
for all those with a cheap ebay dac.

This looks very interesting
balanced_dac_and_broskie_cathode_follower_filtered.png


This is from the chap that designed the aikido preamp, a design which cancels power supply noise. In this case it should cancel all the noise from the dac, producing a very clean single ended signal. This combined with some cheap 6n6p's should make the amp dac truly special. I think this will be the next project!
 
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Erm, very embarrassing. I think I shorted 240V onto one of the DAC's rails. I'm beyond frustrated, I'm devastated. This thing might not see the light of day until Christmas now. It was all functioning perfectly last night, and today I was assembling it in the box. Something went wrong somewhere.:(:mad:
 
ouch.

How did you short 240V? you really must ensure that is the one connection to get right, you could have shorted to the case, and then your goodself!!!

only way you will find out whats been damaged is to power it up and check the ouputs of he powersupply board. IF any are 240V the dac is dead too.
 
Right I think I am getting my head around powering my LM1875 from the mains. Just got to order all the bits.

I was thinking could I use a CMoy circuit as a pre-amp to the LM1875? Would it have much effect on the audio quality?
 
yes, dont do it.

headphone amp does not equal preamp.

Headphone amps are designed to see 32 - 300 ohm load.

Preamps are deisgned to see 10k plus, and present 10k plus load to the source.
 
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