These are to be soldered between gnd and signal to grid, 47nF and 47R in parallell.
Soldered the pots that are cathode resistors to stargnd and set them to 68R as per the schematic. Later I'll adjust them so that I get 16Vdc between plate and gnd.
An externally hosted image should be here but it was not working when we last tested it.
Soldered the pots that are cathode resistors to stargnd and set them to 68R as per the schematic. Later I'll adjust them so that I get 16Vdc between plate and gnd.
An externally hosted image should be here but it was not working when we last tested it.
Front and sides in Oak arrived today 🙂
An externally hosted image should be here but it was not working when we last tested it.
Put in a 500mA primary fuse and fired the board up again.
Voltages are still as I set them and the fuse didn't blow.
Still haven't put any IC's on the board though, won't do that until just before the first test.
Voltages are still as I set them and the fuse didn't blow.
Still haven't put any IC's on the board though, won't do that until just before the first test.
Made a gndpoint to take signalgnd from among other things.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Ordered 50R/2W DALE resistors to use as passive I/V.
Don't know if they are the best for the job, but until I find better I'll use them.
Don't know if they are the best for the job, but until I find better I'll use them.
Hi Jonas, Looks like your getting closer to trying it out. 😀 I worked some on my second build this week. I am about 80% done on the Pedja AD844 I/V. Still need a couple small items. I built it on a vero board due to being lazy about etching a board. 😱🙄 Since I plan to try the Edcor XSM600/600 transformers for filtering I need `600 Ohm resistors and some 1 nF, 2.2 nF and 4.7 nF caps to try. I found a source for Silver Mica 120 pF caps so I bought one to try on the demodulaton pins. If that doesn't lock I will install a surface mount PPS capacitor. My cousin is going to try the transformer thing on his CS4397 DAC. He said it all looks good on his scope. I hope to hear his next week. I'm going to mount everything on a thin piece of hard board for experimenting. Once I'm happy I have a big Antec case that is 16 by 16 by 4 Inches high. A big amp case. I have 4 torroid transformers plus a power supply for the analog board (I/V). I may need to shield the Edcors also.... 😎 My first build didn't leave much extra room and I used the same Antec case for that one. Dave P.S. I think your going to really like the tube sound better 😉
Yes, if I was in a hurry to try it I could use the un-terminated end of the digitalinterconnect and screw it straight to the input on the PCB. But since I'm such a patient man I'll wait for the BNC-connector to arrive 😉
Tbh, I think I'm a little nervous about testing this DAC, considering the amount of work I've put in to it. Should it not sound at all or have problems I might need to check myself into an asylum 🙂
Tbh, I think I'm a little nervous about testing this DAC, considering the amount of work I've put in to it. Should it not sound at all or have problems I might need to check myself into an asylum 🙂
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Bought a pair of matched 3,94uF PIO caps to replace the Rifa's as outputcaps on the tube output.
.... or just send all the parts here - I'll PM my address now...hahahahahha
Don't be afraid.
I have a very long stick I used in the past for pressing the ON button with my old experiments. Sometimes this was a very good idea - oh yes - many explosions.
I think the care you have taken with this project is an absolute credit to you and I have no doubt your capacitors are all in the correct way round and it will work first time !!!
I remember switching on my valve buffer for the first time and watched the things light up - I was so shocked I switched it straight off. Then I remembered they were valves and were supposed to look like they were on fire inside.
I was nervous turning up the volume in case my speakers fried too but all was well and they sounded fine. ( OK, a little humming but I fixed my earth properly and then it was silent )
You'll be fine and it'll be fantastic
It's getting like waiting for the Olympics to start.....how many months has this been going on now ? I'm soo much older already
Can't wait much longer😀
Thanks Andrew 🙂
You'll have to get a week or so older before I test it.
Waiting for the bnc-connector as I said. I don't really worry about the caps, I'm reasonably shure they are all put in right. More concerned about IC's being dead or the dreaded "ticking" some has experienced with this dac.
Luckily I have extras of all IC's.
Tube output is not a major concern either, low voltages and alot simpler design then the amp I fixed.
Tbh, I think the dac will work...just get the jitters everytime it's getting close to the final test, especially with the time and $ that I've put into this one.
Jonas
You'll have to get a week or so older before I test it.
Waiting for the bnc-connector as I said. I don't really worry about the caps, I'm reasonably shure they are all put in right. More concerned about IC's being dead or the dreaded "ticking" some has experienced with this dac.
Luckily I have extras of all IC's.
Tube output is not a major concern either, low voltages and alot simpler design then the amp I fixed.
Tbh, I think the dac will work...just get the jitters everytime it's getting close to the final test, especially with the time and $ that I've put into this one.
Jonas
Was thinking mainly about the tube buffer. Dac pcb is grounded to the chassies on more than one point I think. Tubebuffer stargnd, lifted or not? I guess the best way is to try regular stargnd and then lift it if I get hum issues with it?
hmm, might not be a good idea after all.
That would change the cathode resistors value and in turn change plate voltage?
Anyhow, I'm getting ahead of myself. There will hopefully be no hum at all 🙂
That would change the cathode resistors value and in turn change plate voltage?
Anyhow, I'm getting ahead of myself. There will hopefully be no hum at all 🙂
Grounding
I am no expert but I'll share my approach which is dead quiet. On a 1541a dac with 6n2p tube output cascade of star ground points mostly starting with each tube. In fact on the neg of the RCA output. Tube grounds all to this point on each channel. Dac ground also taken to same point on each channel. Nothing grounded to the case. I then take a fairly heavy ground wire back through the tube b+ filter and ultimately to the safety earth 3rd pin on the IEC plug. At that point and that point only the case is solidly grounded also to the safety ground. My understanding is you don't want current running around the case. It is just used for safety.
As I said, no expert. I defer to others better schooled than I.
Don't forget to ground
the dac
the rca
the b+ power
the filament power supply
the tube
all to the star ground. otherwise you'll get ground loops and hum.
I've done the dac and a couple of cdp's with tube output with this scheme. All dead quite with the volume on full and ear to the speaker. All you hear is some hiss which may be tube noise. Remember to keep ac lines short and away from DC. twist all your power wires nice and tight. Sometimes you need to move them around a little to eliminate a little noise, but no hum.
Good luck. When you first fire it up it will be lovely but tight and constrained. after 10 hours it will open up and after 100 hours it will be magic.
I am no expert but I'll share my approach which is dead quiet. On a 1541a dac with 6n2p tube output cascade of star ground points mostly starting with each tube. In fact on the neg of the RCA output. Tube grounds all to this point on each channel. Dac ground also taken to same point on each channel. Nothing grounded to the case. I then take a fairly heavy ground wire back through the tube b+ filter and ultimately to the safety earth 3rd pin on the IEC plug. At that point and that point only the case is solidly grounded also to the safety ground. My understanding is you don't want current running around the case. It is just used for safety.
As I said, no expert. I defer to others better schooled than I.
Don't forget to ground
the dac
the rca
the b+ power
the filament power supply
the tube
all to the star ground. otherwise you'll get ground loops and hum.
I've done the dac and a couple of cdp's with tube output with this scheme. All dead quite with the volume on full and ear to the speaker. All you hear is some hiss which may be tube noise. Remember to keep ac lines short and away from DC. twist all your power wires nice and tight. Sometimes you need to move them around a little to eliminate a little noise, but no hum.
Good luck. When you first fire it up it will be lovely but tight and constrained. after 10 hours it will open up and after 100 hours it will be magic.
The DAC-pcb has it's own starground and is grounded to the chassis through the mounting screws and bolts.
I have not grounded the RCA-jacks yet.
B+ PS is grounded to stargnd, or rather will be.
Connect dc for heaters to stargnd? I'm using external smps supplies for heaters and B+ (though B+ has additional capacitance etc inside the chassi)
How to I ground the tube? In my case an ECC86.
Schematic I'm using, the one on the right is for OS, on the left for NOS.
Also in the schematic heaters doesn't have their own PS, but B+ voltage is lowered with a power resistor.
An externally hosted image should be here but it was not working when we last tested it.
Just finished one of a pair of braided silver signalcables.
4x1m of 0,2mm silverwire in PTFE tubing braided to make this:
One more of these to go...😱
4x1m of 0,2mm silverwire in PTFE tubing braided to make this:
One more of these to go...😱