Newer version of Dual AK4399
I will need some time to assemble the board and make a A B comparison but I think I don't have sufficient spare super regulators to make the new board exactly with the same power supply as the old board. Anyway, will try.
Special thanks to NinoSimona in referring me to example 3.14 of UTO (Universal Tube Output) in making a direct connection between the Dual AK4399 to UTO. In fact, I emailed the supplier before but his answer was: -
QUOTE
HI Sunny
Yours is a very special design. The opamp converts balance to SE?
It needs very special circuit to do the conversion which is not cost effective to include that in a general purpose board. The only way is to do your own work around outside the board.
Regards
Simon
UNQUOTE
It seems their support don't even know the UTO can be configured as balance input to unbalance output. By the way, the drawing of example 3.14 is also wrong. The drawing is out-phrased.
Using the UTO output is much more superior to any of the opamps I tried - including those discrete opamps like DEXA, Op01 and HDAM. Yet, I also noticed that the Op01 and HDAM are using newer jfets like K246, J103, K30A etc. that; as alleged, not the best jfets. Since I am still having 1000+ of K107 and J74 that I bought 6-7 years ago; both GR and BL grades, I will change them and see if these two discrete opamps can perform better with the swap.
I will need some time to assemble the board and make a A B comparison but I think I don't have sufficient spare super regulators to make the new board exactly with the same power supply as the old board. Anyway, will try.
Special thanks to NinoSimona in referring me to example 3.14 of UTO (Universal Tube Output) in making a direct connection between the Dual AK4399 to UTO. In fact, I emailed the supplier before but his answer was: -
QUOTE
HI Sunny
Yours is a very special design. The opamp converts balance to SE?
It needs very special circuit to do the conversion which is not cost effective to include that in a general purpose board. The only way is to do your own work around outside the board.
Regards
Simon
UNQUOTE
It seems their support don't even know the UTO can be configured as balance input to unbalance output. By the way, the drawing of example 3.14 is also wrong. The drawing is out-phrased.
Using the UTO output is much more superior to any of the opamps I tried - including those discrete opamps like DEXA, Op01 and HDAM. Yet, I also noticed that the Op01 and HDAM are using newer jfets like K246, J103, K30A etc. that; as alleged, not the best jfets. Since I am still having 1000+ of K107 and J74 that I bought 6-7 years ago; both GR and BL grades, I will change them and see if these two discrete opamps can perform better with the swap.
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Sunsun22: interesting info about UTO....
also interesting discount Universal Stereo Tube Output Stage ....hmmm...let me think
also interesting discount Universal Stereo Tube Output Stage ....hmmm...let me think
Hi guys,
I received and Yesterday installed the Marantz HDAM modules as output stage. It sounds as great as output stage with UTC A20 transformers. I didn't noticed any difference so far without A-B test. The HDAM modules are much cheaper than those transformers. I will listen the DAC with these modules for 2 weeks and then decide which output stage finally use. Best regards. Valeri
I received and Yesterday installed the Marantz HDAM modules as output stage. It sounds as great as output stage with UTC A20 transformers. I didn't noticed any difference so far without A-B test. The HDAM modules are much cheaper than those transformers. I will listen the DAC with these modules for 2 weeks and then decide which output stage finally use. Best regards. Valeri
Partsconnexion is having good price for this UTO and it is much cheaper than what I paid for it 5 years ago. I have been using the UTO for TD1541, dual TD1541, AD1865 and it sounds great in every config. However, you can forget about the included output caps. For value/performance, I love the Auricaps. I am using MCap Supreme Silver/Gold at this moment and have received two Supreme Silver/Gold and Oil from Partsconnexion recently. I really eager to try it out.
Hi Valeri,
good to hear another happy owner , can't remember anymore if they required some burn in time or not...
Sunsun22: it's really good price for such kit...
I bought Jantzen Silver Z-Cap based on this review and later plan to try Mundorf Supreme Silver Oil, those gold seems to me too expensive for small improvement over Silver version
good to hear another happy owner
, can't remember anymore if they required some burn in time or not...Sunsun22: it's really good price for such kit...
I bought Jantzen Silver Z-Cap based on this review and later plan to try Mundorf Supreme Silver Oil, those gold seems to me too expensive for small improvement over Silver version
Hi Sunsun22
Yes, I noticed also the incorrect phase of the drawing, a little bit sloppy of the manufacturer. Glad you managed to get the tube output stage working though!
Keep us posted about the jfets-swap you're planning, would be interesting to know if the old types are better.
Nino
HDAM jfet swaps
I obtained the jfet Idss figure from HDAM supplier and changed them to K170 and J74. Without burning in, the opamp sounds more airy, open and detail than before. Although, it is still not as good as the UTO; especially in terms of airy and density, I believe the HDAM will further improve over time.
The Op01 supplier is not that helpful, I think I have to dismount the J103 and measure Idss by myself later.
Please bear in mind the pin out between the new and old jfets are reversed.
I obtained the jfet Idss figure from HDAM supplier and changed them to K170 and J74. Without burning in, the opamp sounds more airy, open and detail than before. Although, it is still not as good as the UTO; especially in terms of airy and density, I believe the HDAM will further improve over time.
The Op01 supplier is not that helpful, I think I have to dismount the J103 and measure Idss by myself later.
Please bear in mind the pin out between the new and old jfets are reversed.
Attachments
Hi Terranigma,
I have tried UTC A20 transformers with this DAC connected directly to AK4399 outputs. Sound is fantastic, almost the same as with Maranty HDAM modules. I also tried cheaper Monacor LTR 110 transformer. With UTC it sounds better.
Hello Valeri100,
I know you did it. I'm curious if Sunsun22 had a chance to compare transformer output with UTO.
Can you explain how did you connect transformer output? Did you isolate 11K resistors from opamp stage and tapped positive and negative signal from these resistors?
I have V1.1 as a kit and I plan to try transformers as well.
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I just connected transformers to 11k resistors. I did not isolate the 11K resistors from DAC outputs. Maybe I should do it.
I am currently moving the DAC board in my preamplifier case which has power supply for tubes. After that I will try this http://www.tubecad.com/2006/08/12/balanced_dac_and_broskie_cathode_follower_filtered.png
I have tube SRPP board which I can modify to this schematic. I think follower will work fine because I don't need amplify output signal. it will serve as unbalancer and provide low impedance.
I am currently moving the DAC board in my preamplifier case which has power supply for tubes. After that I will try this http://www.tubecad.com/2006/08/12/balanced_dac_and_broskie_cathode_follower_filtered.png
I have tube SRPP board which I can modify to this schematic. I think follower will work fine because I don't need amplify output signal. it will serve as unbalancer and provide low impedance.
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You should isolate dac outputs from another stage that causes any load from dac outputs.
Too many capacitors on signal path? I even assume that not having an extra one at amplifier input.
Too many capacitors on signal path? I even assume that not having an extra one at amplifier input.
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I did not try transformer output for this DAC. Would Altec 15335A be a good choice?
I have a pair of Sowter i/v transformer for TDA1541 that I put it somewhere in my Bermuda Triangle. I have to find them before I can recall the model number. Could they be useful?
By the way, I have ordered a O type power transformer with OCC silver plated wires as secondary for this DAC. I always have good result with this transformer in my DIY gears. It will arrive in these few days after chasing the builder for almost three weeks. Will keep everyone informed.
I have a pair of Sowter i/v transformer for TDA1541 that I put it somewhere in my Bermuda Triangle. I have to find them before I can recall the model number. Could they be useful?
By the way, I have ordered a O type power transformer with OCC silver plated wires as secondary for this DAC. I always have good result with this transformer in my DIY gears. It will arrive in these few days after chasing the builder for almost three weeks. Will keep everyone informed.
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Altec 15335A is 15k:15k 1:1 transformer which has very high impedance in my opinion. Transformer users at V-out dac outputs generally recommending 600:600 1:1 type line output transformers.
Hi Kukynas,
I think sound with transformers a little bit better. I am going to make switch soon for A-B test and then invite a musician.
I think that is not hard to find a musician in Vienna..you can isolate the 11K resistors when connecting the transformer this time.
Yes, I agree, but it is impossible completely to get rid of capacitors in tube amplifier. I will definitely give a try of this Bronskie cathode follower. Two years ago I made his Aikido amplifier as driver stage for 300B SE tube amplifier. IT sounds great. I trust this tube guru.
P.S. Now I use this DAC with Nelson Pass F5 amplifier. There is no any capacitor in signal path (from A4399 output till output of the F5). Sound is fantastic but I need to insert buffer with low impedance between output volume control and input of the F5. Without buffer it is possible to hear small noise 50 Hz.
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