6SN7/6SN7 Aikido + CS4398 DAC = HEAVEN

[john65b]

So I finally finished my 6SN7/6SN7 Aikido, and since I had a bit of room left in my Chassis (Audio Research SP type Chinese replica off fleabay), I installed one of those ubiquitous CS4398 DACs, also off fleabay.

Aikido has .22uf Russian Teflons and 10uF WIMAs. I absolutely love WIIMA Caps - cheap and always sound fantastic. I have a RCA switchbox on both preamp outputs (one from Wima and the other from the Teflons) to switch between the two caps, and am liking the Wimas (maybe because of the Bass response)...maybe use the .22uf Teflons to bypass the Wimas and call it a day...

DAC has LM4562 OPAMPS that replaced the stock OPA2134. Tried the LM6172 (too bright) and a pair of OPA627 (kinda dull...) I also bought a set of Sescom MI-14 Transformers to replace the OPAMPs (huge thread on this mod), but decided to leave the LM4562 since it was making me quite happy.

Anyway, I a happy camper.

[john65b]

Whoops, forgot the most important pic - of the Guts....

[piero7]

Very nice enclosure!!

Try russian K73-16 caps too on aikido and a couple of UTC-A20 as output on the dac side

[gabrielbecheanu]

Hi john65b
You try to measure the output tube voltage at 1Khz? you have more then 2.5V rms? I have the same DAC but i use the lampizator cathode follower. First time o listen i was very surprised about the sound but when i measure the output on DAC an tube buffer i so a big difference in voltage. The DAC has 2.5Vems ad the tube 5.5Vrms so the A/B test was unfair. i change some resistors in the tube stage to have the same output level. After that the difference was not so big. Many people do the same mistake like me compeer two devices with different output level an they are very surprised about the sound.
Where did you get the PCB I would like one to make a test
Best Regard
Gabriel

[gabrielbecheanu]

I found the board here Aikido Amplifier Octal Stereo Printed Circuit Board
Please tell me if you want the output level at 1 kHz sinusoidal at 0db

Best regards
Gabriel

[john65b]

Gabriel, I do not have a signal generator to test for you. But in the Octal Akido Manual, you will see that the 6SN7 and 6SN7 combo are low gain. I don't need much so it is fine with me.

Also, I did not remove the opamp buffers. Aikido is after the DAC, and DAC is stock (other than OPAMP upgrade to LM4562)

[Andrea:]

The LM4562 is nice with the CS4398: makes a total of 7 different numbers

And includes the 5 and 3, the "most musical" of numbers.



You could try the LM4562HA (TO99) though...as I found the LM4562NA a bit lacking smoothness & roundness in the midrange.

Otherwise, try the LME49725MA (also 7n with the CS4398 ).

Finally try the OPA1612, the dual version of my favorite the OPA1611.

[gabrielbecheanu]

Hi
To test the output level you don’t need a signal generator you must use a Test CD like Sony Test C.D. Type 4 [YEDS-18] with frequencies. I upgraded my DAC with the same OPA but I made some modification > Fikus explain how to do it. It is an improvement. For the tube stage I took the signal after the DAC not after the OPA
Best regards

[Andrea:]

And I agree that the OPA627 is "kinda dull"... even if it's a favorable combination with the CS4398 numerically. The OPA1611 is faaaaaaaaaaaar better...


And the LM6172 is kinda dull too, with the CS4398 (and per se).

[Andrea:]

Forgot... try 4x LT1028ACN8. You might be surprised...especially as you have tubes in there.