Quan,
I have a side question.
What have you done with the input section of the tube buffer.
I see C42 and C24 are out plus L3 and L4 look to be resistors.
What was the improvement/change of this modification?
Jeroen
I have a side question.
What have you done with the input section of the tube buffer.
I see C42 and C24 are out plus L3 and L4 look to be resistors.
What was the improvement/change of this modification?
Jeroen
I fine tuned the LPF by ears. Those chokes (L3 and L4) sounded grainy to me. I have done quite a few DAC and I believe there is no need for a heavy LPF.
I use only one 1nF Polyestyrene cap per channel (NOS made by TRW), replaced the chokes with good 20 ohm resistors. The DAC sounded a lot more transparent this way.
If you look into details you may see that I replaced many other parts in this DAC e.g all bypass caps on the DAC board, I/V resistors.
I think the most important modification is removal of the cathode caps for the ECC88 tubes. 4x 240 ohm original resistors were replaced with 680 ohm carbon resistors. I don't know the brand of these resistors but they sound better than KIWAME resistors that I tried in the same position.
Cheers
I use only one 1nF Polyestyrene cap per channel (NOS made by TRW), replaced the chokes with good 20 ohm resistors. The DAC sounded a lot more transparent this way.
If you look into details you may see that I replaced many other parts in this DAC e.g all bypass caps on the DAC board, I/V resistors.
I think the most important modification is removal of the cathode caps for the ECC88 tubes. 4x 240 ohm original resistors were replaced with 680 ohm carbon resistors. I don't know the brand of these resistors but they sound better than KIWAME resistors that I tried in the same position.
Cheers
JeroenVl said:
I have music! 🙂
a big thanks to Quan Tran, Jeroen and Thomas, and also for assistance some months back to Julien and Shane for their help. I am very grateful to you.
Before signing off for a bit, please help me understand 2 things:
1. The LED. Is the attached pic the blue LED? If it is not, any guidance in what spec I should seek? I will connect it to SK8
2. On the dac board, also shown in the pic, SK6 (SYN) is blank, and R39 and R47 are blank. Is this deleterious to the sound, or will it harm the dac?
Thank you
a big thanks to Quan Tran, Jeroen and Thomas, and also for assistance some months back to Julien and Shane for their help. I am very grateful to you.
Before signing off for a bit, please help me understand 2 things:
1. The LED. Is the attached pic the blue LED? If it is not, any guidance in what spec I should seek? I will connect it to SK8
2. On the dac board, also shown in the pic, SK6 (SYN) is blank, and R39 and R47 are blank. Is this deleterious to the sound, or will it harm the dac?
Thank you
Connection on SK6 is optional. It does change the sound but not necessarily for the better.
R39 and R47 are optional I think they make no audible difference.
Try to find a LED that look like this http://www.pololu.com/products/misc/0341/big.jpg
R39 and R47 are optional I think they make no audible difference.
Try to find a LED that look like this http://www.pololu.com/products/misc/0341/big.jpg
Dear all,
I would like to inform you that my friend Tube-lover (Thomas) has been re-admitted to the hospital again owing to the inflammation of his leg after surgery.
He cannot respond to any enquiries for some days until he returns.
Regards,
T.C. MA
25 Sep. 2006
I would like to inform you that my friend Tube-lover (Thomas) has been re-admitted to the hospital again owing to the inflammation of his leg after surgery.
He cannot respond to any enquiries for some days until he returns.
Regards,
T.C. MA
25 Sep. 2006
I have a rocket logo 6H23/6922 and Amperex Bugle Boy. Are all 6922 and 7308 tubes drop in replacements for 6dj8?
Also, I took others' lead and removed the inductor (L3/L4) and 1st cap (C23/C48) out of the signal path on the tube board, as well as removing the cathode bypass cap. The sound did open up. But the noise floor has risen. There is some HF hash now. I'm planning to try a good quality resistor (to replace inductor) and replace the remaining cap. What value would you guys recommend for this resistor and cap?
What is very interesting is that, prior to this project, a lot of folks praised the 6s45 output stage for tda1541, but few if any prefer it to the 6dj8 in Thomas's configuration. Any thoughts?
Also, I took others' lead and removed the inductor (L3/L4) and 1st cap (C23/C48) out of the signal path on the tube board, as well as removing the cathode bypass cap. The sound did open up. But the noise floor has risen. There is some HF hash now. I'm planning to try a good quality resistor (to replace inductor) and replace the remaining cap. What value would you guys recommend for this resistor and cap?
What is very interesting is that, prior to this project, a lot of folks praised the 6s45 output stage for tda1541, but few if any prefer it to the 6dj8 in Thomas's configuration. Any thoughts?
the 6922 and 7308 have slightly different specs compared to 6dj8 and can substitute for 6dj8 as they are very close.
Regarding the passive filter after the DA chip I recommend that you remove the second cap not the first one then you can tune your filter by changing the resistor value (substitute for the choke). No need to change the cap value. You can start with 20ohm and increase it slowly up to a point where you feel that the top end is under control.
6c45pi or 6dj8? Only you can decide. I found that different types of 6dj8 sound very different so it's difficult to compare with 6c45pi.
If you use 6c45pi, you probably need to use some choke or CCS for B+ as someone has posted before.
Regarding the passive filter after the DA chip I recommend that you remove the second cap not the first one then you can tune your filter by changing the resistor value (substitute for the choke). No need to change the cap value. You can start with 20ohm and increase it slowly up to a point where you feel that the top end is under control.
6c45pi or 6dj8? Only you can decide. I found that different types of 6dj8 sound very different so it's difficult to compare with 6c45pi.
If you use 6c45pi, you probably need to use some choke or CCS for B+ as someone has posted before.
hi quantran,
I funish the 5687 HV cathode follower Tube buffer for full balance 1541a dac already. will test with the Pre- amp OPT this week. after test OK. I will send to your sister take to U to test. Since some of the ver.2 dac Tube buffer had little bit hum which was cause by the false imprint of the factory. I change another one already. I will compensate to all the old User.
thx
thomas
I funish the 5687 HV cathode follower Tube buffer for full balance 1541a dac already. will test with the Pre- amp OPT this week. after test OK. I will send to your sister take to U to test. Since some of the ver.2 dac Tube buffer had little bit hum which was cause by the false imprint of the factory. I change another one already. I will compensate to all the old User.
thx
thomas
Hi Thomas
If you would like to send it to me for testing please send me an email to discuss about delivery method. My sister has left HK.
If you would like to send it to me for testing please send me an email to discuss about delivery method. My sister has left HK.
Thomas,
You mentioned 5687 cathode follower tube circuit? What tube does this follow, and is it srpp? I'm considering building a new tube stage with 5695 or 6072a in srpp with 5687 cathode follower.
You mentioned 5687 cathode follower tube circuit? What tube does this follow, and is it srpp? I'm considering building a new tube stage with 5695 or 6072a in srpp with 5687 cathode follower.
hi riotubes,
its a HV cathode follower output stage. signal from Op-amp>>>> tube buffer >>> caps output or 5687 tube buffer to 1:1 outp[ut trans.
thx
thomas
its a HV cathode follower output stage. signal from Op-amp>>>> tube buffer >>> caps output or 5687 tube buffer to 1:1 outp[ut trans.
thx
thomas
hi all,
most tube buffer such as the cathode follower will use 6dj8.
Cost was low voltage low or middle current, less dynamic but will smooth with less detail. in 24/96 or 192 will Ok. but if for 1541a or coming 1865 will not because 16bits & 18 bits need more dynamic less lose of detail. So I prepare this high voltage & current cathode follower for the coming 1865 & full balance dac.
take a looks. I had over 1K pcs of 1950's NO 5687 on hand, ever dac will follow with NOS 5687 tube.
This HV & HA cathode can use with capacitor output or use the pre-amp trans follow with the kit.
thx
thomas
most tube buffer such as the cathode follower will use 6dj8.
Cost was low voltage low or middle current, less dynamic but will smooth with less detail. in 24/96 or 192 will Ok. but if for 1541a or coming 1865 will not because 16bits & 18 bits need more dynamic less lose of detail. So I prepare this high voltage & current cathode follower for the coming 1865 & full balance dac.
take a looks. I had over 1K pcs of 1950's NO 5687 on hand, ever dac will follow with NOS 5687 tube.
This HV & HA cathode can use with capacitor output or use the pre-amp trans follow with the kit.
thx
thomas
Attachments
Member
Joined 2002
I finally got around to lowering the voltage on the B+ and the EZ80 rectifier filament.
Thomas spec'd 200V for 6dj8. I now have 170V at the tube pins. Is this too low?
The EZ80 rectifier filament is spec'd 6.3V. I have 6.0V. I think this is OK?
Is it bad to run the Dac under the specified voltages?
Finally, did anyone try to nano amorphous core pulse transformer on the digital input and decide to keep it there? It has 6 pins and the board looks like it accepts 4 pins.
Thomas spec'd 200V for 6dj8. I now have 170V at the tube pins. Is this too low?
The EZ80 rectifier filament is spec'd 6.3V. I have 6.0V. I think this is OK?
Is it bad to run the Dac under the specified voltages?
Finally, did anyone try to nano amorphous core pulse transformer on the digital input and decide to keep it there? It has 6 pins and the board looks like it accepts 4 pins.
Hi Thomas,
I would like to order the DAC V3.0 with usb input, so i send you an e-mail via diyaudio.hk but i didn't received any answer. Is it the best way to contact you?
😀
I would like to order the DAC V3.0 with usb input, so i send you an e-mail via diyaudio.hk but i didn't received any answer. Is it the best way to contact you?
😀
- Status
- Not open for further replies.