Measured µPA68.
12.82\12.81
13.24\13.22
13.20\13.02
12.75\12.72
12.28\12.27
11.66\11.67
12.65\12.68
13.01\13.04
12.17\12.20
13.10\13.10
Lilian thank you very much for sharing your measurements!!. If Salas can clarify if high grade M 9-14ma IDSS or low L 5-10ma is better or if it does not matter for the preamplifier.
My order µPA68 never arrived from Aliexpess
5pcs/lot UPA68HA UP A68HA ZIP 7|Relays| - AliExpress
My order µPA68 never arrived from Aliexpess
5pcs/lot UPA68HA UP A68HA ZIP 7|Relays| - AliExpress
Hi,
I built a DCG3 with external power supply. I used VRDN boards because I already had them built. I have some UBiBs in the works to try as well, if I can fit them in the box. I was a little worried about having the regulators in another box, but it seems to work fine. Voltages are stable at the input of the DCG3 boards. I don't really know what else to test to see if having them far away is a problem.
I ran a Rightmark test and put the results here. I've seen better cross talk figures when using a good stepped attenuator and standard selector switch. This is the first time I tried using this massive attenuator board, or maybe I could have paid more attention to routing my IO cables. I kept them up high because I had the DC lines running on the bottom of the chassis.
I've only been listening to it a couple of days. It sounded a wee bit aggressive the first day, and mellowed out a little by the end of the second day. Sounds good already.
Thanks very much to Salas for design and Tea for providing boards and parts, and to hpasternack for answering my earlier question about external PS. I'm looking forward to the future Salas tube preamp I've heard rumors about.
Alan
I built a DCG3 with external power supply. I used VRDN boards because I already had them built. I have some UBiBs in the works to try as well, if I can fit them in the box. I was a little worried about having the regulators in another box, but it seems to work fine. Voltages are stable at the input of the DCG3 boards. I don't really know what else to test to see if having them far away is a problem.
I ran a Rightmark test and put the results here. I've seen better cross talk figures when using a good stepped attenuator and standard selector switch. This is the first time I tried using this massive attenuator board, or maybe I could have paid more attention to routing my IO cables. I kept them up high because I had the DC lines running on the bottom of the chassis.
I've only been listening to it a couple of days. It sounded a wee bit aggressive the first day, and mellowed out a little by the end of the second day. Sounds good already.
Thanks very much to Salas for design and Tea for providing boards and parts, and to hpasternack for answering my earlier question about external PS. I'm looking forward to the future Salas tube preamp I've heard rumors about.
Alan
Attachments
Hi
A very nice example. Good looks too. Congratulations. Can't have anything technically done too wrong when the general performance is awarded "excellent" by RightMark. I don't know if a better HF crosstalk figure would be audible or if VRDN subjectively compliments it best. Its evidently very quiet as a total build. So it can't be bad at all as is. Left channel has bit higher noise floor below 500 Hz for some reason. Usually they go along. Maybe a measurement loop quirk. Long cabling between PSU and load gives higher output impedance to the PSU is the main penalty. Also rising more at HF due to inductance. Can modulate easier in high demand swings but not so much with Class A loads which tend to draw high but steady. DCG3 is working in Class A.
What is the nominal impedance of that attenuator? What audio interface you used for measuring the build?
A very nice example. Good looks too. Congratulations. Can't have anything technically done too wrong when the general performance is awarded "excellent" by RightMark. I don't know if a better HF crosstalk figure would be audible or if VRDN subjectively compliments it best. Its evidently very quiet as a total build. So it can't be bad at all as is. Left channel has bit higher noise floor below 500 Hz for some reason. Usually they go along. Maybe a measurement loop quirk. Long cabling between PSU and load gives higher output impedance to the PSU is the main penalty. Also rising more at HF due to inductance. Can modulate easier in high demand swings but not so much with Class A loads which tend to draw high but steady. DCG3 is working in Class A.
What is the nominal impedance of that attenuator? What audio interface you used for measuring the build?
Hi,
The nominal impedance of the attenuator is 20k. The audio interface is a Prism Sound Orpheus which I bought 15 years ago for home studio recording. It is not their latest model. I can post it's loopback test if you are interested.
That left channel rise is always present no matter what device I measure, so it must have something to do with my measurement setup. I have to use cable adapters to measure since the unit only has balanced IO.
The nominal impedance of the attenuator is 20k. The audio interface is a Prism Sound Orpheus which I bought 15 years ago for home studio recording. It is not their latest model. I can post it's loopback test if you are interested.
That left channel rise is always present no matter what device I measure, so it must have something to do with my measurement setup. I have to use cable adapters to measure since the unit only has balanced IO.
The loopback for the Prism Orpheus is here. I had to use RCA to TRS adapters because I don't have balanced TRS cables. I took it away from my equipment rack to measure it because I have a rat's nest of cords and cables there. Maybe I should do the same for the preamp.
Alan
It was not necessary in the end, friend Felipe warned me not to use digital attenuator from the dac, it will erase many bits information and turn to gain and dinamics loss. So now much better at initial set 3x. A bit too much on amp output, but fine on headphone and overall is ok balanced in between. As pot, I am using stepped ladder 50k. Dale resistors.
Little update.
DCG3 withdrawal! The Aikido is a fine preamp—and "the best" in our system until DCG3 arrived—wow was it missed while on the bench getting a front panel! It's considerably more 3D in our space. Lots more music on tap it would seem—whole family agrees.
Made some knobs from scratch for this one. Headphones! YES!
Will update the Muses inside to the latest chip just for kicks—when the parts show up from Digikey.
Question about headphone connection—I ran ring to right channel, tip to left channel, ground to one of the grounds on the HP side of the preamp—do I need to connect the HP grounds on the preamp? Does it matter? I haven't tried the phones yet—someplace here Salas suggested lifting the ground at the jack if there was any hum...The amp through the monkey coffins is a ghost—zero anything to be perceived.
Huge gratitude to Salas for this fine audio-awesomery. And to Tea of course for parts/project organizational mastery.
(and huge YES<---1000pt to a secret Salas-tube pre—if such a beast exists I've been building tube guitar amps—so 100% tubes on the brain)
DCG3 withdrawal! The Aikido is a fine preamp—and "the best" in our system until DCG3 arrived—wow was it missed while on the bench getting a front panel! It's considerably more 3D in our space. Lots more music on tap it would seem—whole family agrees.
Made some knobs from scratch for this one. Headphones! YES!
Will update the Muses inside to the latest chip just for kicks—when the parts show up from Digikey.
Question about headphone connection—I ran ring to right channel, tip to left channel, ground to one of the grounds on the HP side of the preamp—do I need to connect the HP grounds on the preamp? Does it matter? I haven't tried the phones yet—someplace here Salas suggested lifting the ground at the jack if there was any hum...The amp through the monkey coffins is a ghost—zero anything to be perceived.
Huge gratitude to Salas for this fine audio-awesomery. And to Tea of course for parts/project organizational mastery.
(and huge YES<---1000pt to a secret Salas-tube pre—if such a beast exists
I've been building tube guitar amps—so 100% tubes on the brain)Attachments
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