Don't want to get off topic here, as this thread deals with the big DAC...
However I have hooked up a pair of Cinemag transformers to the output of the small DAC too (CS4397 chip) and bypassed the opamp circuit with good results.
I used only 500ohm resistors to load the primary side, and using no other R/C circuits on the inputs or outputs.
The sound with the transformer output is much better than the opamp circuit, however not nearly as good as the big DAC with transformers. And with a lot less mods than the small DAC needs to have just to get it to sound decent.
Cheers
Hello Friends
My finding after months of testing and comparing, even with vinyl sources:
Use this DAC with good output trannies. No filter.
BUT:
Add a fine line driver and use it's built in low pass filtering.
Actually, I am using a JC2 clone as line driver.
Boahhh!
For me, the second breakthru, after using transformers instead of classical DAC output circuits.
Merry christmas
Franz
P.S.
On this picture, you can find the JC2 and its power supply on top of the white board, the flying pcb's and the open torroid. No childrens in my appartement today...
My finding after months of testing and comparing, even with vinyl sources:
Use this DAC with good output trannies. No filter.
BUT:
Add a fine line driver and use it's built in low pass filtering.
Actually, I am using a JC2 clone as line driver.
Boahhh!
For me, the second breakthru, after using transformers instead of classical DAC output circuits.
Merry christmas
Franz
P.S.
On this picture, you can find the JC2 and its power supply on top of the white board, the flying pcb's and the open torroid. No childrens in my appartement today...
An externally hosted image should be here but it was not working when we last tested it.
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Yes, exactly. Don't use an opamp circuit!
Mark Levinson JC-2 (John Curl). You can find almost everything about it here in this forum, also with participation of John Curl!
I have a chinese JC2 pcb and built it with carefully selected JFETS and caps.
Why did I further experiment?
Because I changed my phono pre from a phonoclone to an Aikido with stepup transformers.
Beginning from this day all my different DAC's sounded worse compared to the vinyl. Thin mids, weak bass.
So, I thougt to fiddle around with line drivers, to use the "natural" low pass filtering and to be more cable independent.
Full success! Now some recordings with the DAC are sounding better, some recordings are better on vinyl.
Today I definitely built the line driver into the DAC's enclosure.
Franz
It's not "against". It's an alternative. I hate opamps and I'm struggling to eliminate any opamp from my system's signal path, and I'm succeed. I have all tube signal path. I have absolutely no opamps in my signal path. I even have no opamp built into DAC chip, because my chip is Burr-Brown PCM1798 now. It's current output DAC, so there's no opamp at the output.
But it's my way, my choice, and one has to choose his own way. Or same way if he likes
Hi fordgtlover
would you please share your Impression from discrete output stage Rock Grotto Audio Forum - For Headphones - Headphone Amps - Amplifiers - X-Can V2 - Musical Fidelity - headphone Discussion - Amplifier Discussion - DIY - Amplifier Kits - Projects - SCHA - Sennheiser - Beyer - Grado - Audio Technica - Headphone amp
I will try to build - any difference between jfet and bc550
how Is compared to passive output using transformer
would you please share your Impression from discrete output stage Rock Grotto Audio Forum - For Headphones - Headphone Amps - Amplifiers - X-Can V2 - Musical Fidelity - headphone Discussion - Amplifier Discussion - DIY - Amplifier Kits - Projects - SCHA - Sennheiser - Beyer - Grado - Audio Technica - Headphone amp
I will try to build - any difference between jfet and bc550
how Is compared to passive output using transformer
Exactly!
I prepared some time ago a board with a tube (a 6111WA, I think I showed it somewhere in this thread), a plate follower, but for my tests in the last days it was quicker to build up a psu (LM317 based) for the JC-2 than for the plate follower.
One day (who knows?), I will compare the two solutions.
Imho, the most important thing is to avoid a 1:1 global feedback, like used in unity gain opamp circuits.
Franz
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McGyver
this is the calculation I made for 6N6P. Can you tell me if this is right? Does this means Rp and Ri is not needed?
Is the Anode supply is really as high as 230VDC?
An externally hosted image should be here but it was not working when we last tested it.
No, it's not right. You must use a capacitor at output. Rp is unneccesary. You should do it like that. Calculate it from the beginning.
Attachments
Agree totally: with a passive it lacked body or density of sound, was a bit thin. I tried a few old preamps which I have and the best was an old ASR Collector line section which uses Hitachi JFETS for output purposes. [As does JC's JC2!!] The result is superb! But in my case I am using filtering with UTC transformers. The only problem is that it is a bit too high volume and I have to cut the volume pot to lower levels tahn I like to use......but my horn speakers are around 95Db sensitivity.
And a happy Christmas to you Franz.
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McGyver
Sorry I don't have the method of calculating the right circuit. Perhaps maybe you can give the formula as a hint for me to correct this circuit...
The tutorial about triod is very good. But the schematic is different.
An externally hosted image should be here but it was not working when we last tested it.
from your cathode follower circuit
I found a website similar to your buffer circuit The Tube CAD Journal, August 1999 pg 1
But there's no tutorial and guides for R, I, V calculation like from the link you given. Perhaps you can show us the calculation...!