Hi Bill,
What I meant to say is "I do not want to drill hole..." I left out the not in the sentence.
I'm looking at the AD1853 datasheet. It is page 15 showing the "Output Buffers and LP Filters"?
There is a R36 2.74K for the right channel and also a R40 2.74K on the left channel. You need to put one trimmer on each channel, correct?
Hi Salas,
If the trimmer is a 10-turn type, I think it should stay reasonably stable (I'd think it is a bit unstable if it is a 1-turn type). Looking at the circuit, there is trimmer in there too to adjust the L/R balance. So if folks at Benchmarks are not worried about using a trimmer for L/R balance, it should not be that bad to use a 10-turn trimmer for tuning out the DC offset.
What I meant to say is "I do not want to drill hole..." I left out the not in the sentence.
I'm looking at the AD1853 datasheet. It is page 15 showing the "Output Buffers and LP Filters"?
There is a R36 2.74K for the right channel and also a R40 2.74K on the left channel. You need to put one trimmer on each channel, correct?
Hi Salas,
If the trimmer is a 10-turn type, I think it should stay reasonably stable (I'd think it is a bit unstable if it is a 1-turn type). Looking at the circuit, there is trimmer in there too to adjust the L/R balance. So if folks at Benchmarks are not worried about using a trimmer for L/R balance, it should not be that bad to use a 10-turn trimmer for tuning out the DC offset.
Kuro said:
The only thing I know is that I don't hear any bass issue with the Auricaps (well run in) in my system even on various headphones.
PSU noise is not an issue according to the DAC-1 designer. Since he has a great layout and an excellent PSRR proven by shown measurements. I guess that the different impedance of another regulator in HF will sound different, and I would implement an LM317 solution if I was trying to listen to something there.
Look for Cree Schottky diodes.
salas said:
I just removed the Cerafine caps and resoldered the Auricaps by reversing the polarity (the black lead on the cap goes to the + pad on the circuit board). Now it does make a difference. The sound is a bit more focused and I regain tightness of the bass note. It is almost as if I've installed the speaker wires in the wrong direction of the signal flow. My system is actually good enough to tell if I had the speaker wires installed in the reversed direction (I've tried this before).
I went and carefully re-read the Auricap application notes, and I now have the correct installation. As far as I can tell, shielding is very important. Using an unshielded powercord vs. a well shielded one produced very different sound result on the DAC1!
My previous attempt of the Cerafine was to improve the bass note, now I don't feel the urgency to change the PSU caps, diodes or regulator.
I'll report back when I reached 120 hrs of break-in on the Auri's.
Going thru' the forums, I found a schematic for DC servo for tuning out the offset:
http://www.fullnet.com/~tomg/gooteesp.htm#2
Apparently, it is not as simple as tuning out the DC offset by a trimpot. The DC offset can depend on input/output impedance...
http://www.fullnet.com/~tomg/gooteesp.htm#2
Apparently, it is not as simple as tuning out the DC offset by a trimpot. The DC offset can depend on input/output impedance...
DC coupling
Just now getting back online since I submitted my reply:
Salas: 1. DC servo would be a good way to go to make sure it doesn't drift out of a pre-determined tolerance. I measured the offset over a short period of time, several minutes, cover off, so I cannot say if it's steady over time. Measurements with the cover on over days and trending the data would tell us if the drift were "acceptable" or not.
2. I'm using a prototype OB speaker with a JBL 2226H, a B&C 8PE21 mid, a B&C DE10-3 HF augmented by two NHT 1259 subs crossed at ~70Hz. Main power amps are modified Altec 1569A, running PP Class A with single 6550 outputs. Right now I'm going from the DAC1 right to the Altecs. The bass just seems to be more relaxed. As I listen up and down the scale, the sound of the bass guitar is more consistent. Back in 1846, when I was a tuba player, my teachers tried to get me to make my sound consistent up and down the scale, from the lowest to the highest notes. OK, maybe it wasn't 1846, more like 1970's.
I'll work on the pix, not familiar with how to do it here. The pic I posted is too glary anyway.
Kuro: 1. I really don't know which version it is, I know it's not USB, cuz I could probably put that to good use! But which earlier version, I don't know. It has the paralleled coupling caps...
2. I added the RCA jacks for my own edification, just to see, but I did not interrupt the signal flow to the rest of the board, so you could do the mod without adding the extra wires and jacks. I listened to the normal single ended output through a separate headphone amp and it was still improved over the cap coupled version. I do prefer the "new" output through the speakers though, but not by much. I actually use the normal unbalanced output to drive the subwoofer's crossover. I have not played with the balanced output yet or the onboard headphone yet, just a time constraint at this point. BTW, I should have mentioned that I had previously replaced the opamps with the National LM4562's, also a big improvement to my humble ears. This DC coupling mod finishes the job for me. Relaxes the sound.
3. yes, one pot for each opamp.
I should really get more data on DC drift. If we quantify it, then we can decide if the drift is too much to tolerate, whether a servo would be required. I'm thinking the advantage of the 10 turn pot is "set-ability" and not DC stability. The drift would likely come from changes in temperature. After several minutes warmup, I set the offset to within 0.1 mV (resolution of my DMM) and hooked it into the system just to see if it would be worthwhile. Then I got excited and had to tell someone!
I will open the unit up and take more pix, and will figure out how to post them. I will also find some time to trend the DC offset data over several hours with the cover on and report back. Oh, and if it's OK with you all, I'll listen a bit more too ;~)
Bill
Just now getting back online since I submitted my reply:
Salas: 1. DC servo would be a good way to go to make sure it doesn't drift out of a pre-determined tolerance. I measured the offset over a short period of time, several minutes, cover off, so I cannot say if it's steady over time. Measurements with the cover on over days and trending the data would tell us if the drift were "acceptable" or not.
2. I'm using a prototype OB speaker with a JBL 2226H, a B&C 8PE21 mid, a B&C DE10-3 HF augmented by two NHT 1259 subs crossed at ~70Hz. Main power amps are modified Altec 1569A, running PP Class A with single 6550 outputs. Right now I'm going from the DAC1 right to the Altecs. The bass just seems to be more relaxed. As I listen up and down the scale, the sound of the bass guitar is more consistent. Back in 1846, when I was a tuba player, my teachers tried to get me to make my sound consistent up and down the scale, from the lowest to the highest notes. OK, maybe it wasn't 1846, more like 1970's.
I'll work on the pix, not familiar with how to do it here. The pic I posted is too glary anyway.
Kuro: 1. I really don't know which version it is, I know it's not USB, cuz I could probably put that to good use! But which earlier version, I don't know. It has the paralleled coupling caps...
2. I added the RCA jacks for my own edification, just to see, but I did not interrupt the signal flow to the rest of the board, so you could do the mod without adding the extra wires and jacks. I listened to the normal single ended output through a separate headphone amp and it was still improved over the cap coupled version. I do prefer the "new" output through the speakers though, but not by much. I actually use the normal unbalanced output to drive the subwoofer's crossover. I have not played with the balanced output yet or the onboard headphone yet, just a time constraint at this point. BTW, I should have mentioned that I had previously replaced the opamps with the National LM4562's, also a big improvement to my humble ears. This DC coupling mod finishes the job for me. Relaxes the sound.
3. yes, one pot for each opamp.
I should really get more data on DC drift. If we quantify it, then we can decide if the drift is too much to tolerate, whether a servo would be required. I'm thinking the advantage of the 10 turn pot is "set-ability" and not DC stability. The drift would likely come from changes in temperature. After several minutes warmup, I set the offset to within 0.1 mV (resolution of my DMM) and hooked it into the system just to see if it would be worthwhile. Then I got excited and had to tell someone!
I will open the unit up and take more pix, and will figure out how to post them. I will also find some time to trend the DC offset data over several hours with the cover on and report back. Oh, and if it's OK with you all, I'll listen a bit more too ;~)
Bill
Better pics? of DC offset pot
See if this works for higher resolution pictures. http://phoenixhifi.com/Projects.html
Our audio club here in phoenix uses this website from time to time. Haven't lately, time to rejuvenate.
Bill
See if this works for higher resolution pictures. http://phoenixhifi.com/Projects.html
Our audio club here in phoenix uses this website from time to time. Haven't lately, time to rejuvenate.
Bill
A diversion from topic, but has anyone compared the DAC1 to DACs from Wavelength Audio?
http://www.usbdacs.com/Products/Products.html
The Brick is I think about 1/3 more $ than the DAC1, but fwiw got a class A in Stereophile
http://www.usbdacs.com/Products/Products.html
The Brick is I think about 1/3 more $ than the DAC1, but fwiw got a class A in Stereophile
Hey salas, transformer coupling has kept me happy until boredom called for a reversion to amber bliss mode. Having the box open recalled another simple mode of potential interest. Lift the toroidal transformer off the chassis with a small rubber grommet at the bottom of the bolt and fit another one beneath the capture nut. It greatly reduces the chassis vibration due to the rectifier current pulses. Is it audible? Beats me, but if you're looking for a reason to play....
After 5 minutes of listening.....
Less immediate, less detail, less dark (or more forward), slightly more depth (or more ambiguous imaging), more mechanical. The Blackgates have been in a parts box for a year+ already. Ouch. While not a true believer in break-in I am of giving manufacturer's recommendations a fair chance. At this very early stage it's not a bad sound as much as it is boring, certainly less attention focusing than the Ouncers. I need the latter for a tube splitter project though, so BG it is for now.
Donuts are good. :0
Less immediate, less detail, less dark (or more forward), slightly more depth (or more ambiguous imaging), more mechanical. The Blackgates have been in a parts box for a year+ already. Ouch. While not a true believer in break-in I am of giving manufacturer's recommendations a fair chance. At this very early stage it's not a bad sound as much as it is boring, certainly less attention focusing than the Ouncers. I need the latter for a tube splitter project though, so BG it is for now.
Donuts are good. :0
Hi all,
I'm happy to report that the 2.2uF Auricaps are now residing permanently in my DAC1 (Salas: the impedance is around 8K ohm on my DAC1).
There is no significant sonic change after the 120 hrs break-in period. Most of the differences were heard in the first 2 hrs.
Together with a new powercord (Accustic Arts Ferrite II), the mod is pretty much a done deal for me. The powercord made as much of a difference as the film caps. This is one sonically balanced powercord and it improves pretty much everything. Bass is more dynamic and tight. Vocals are smoother than ever.
I even went in to my dealer friend and compared the sonic signature of my system against a full blown high-end Accustic Arts system (transport, DAC, pre and power amp, all AA hardware with full balanced connections) driving a pair of Triangle Magellan Cello speakers (the entire system price is probably 3-4 times the price above mine) and the sonic signature is remarkably similar.
I just received my Elna Silmic II 1000uF 50V caps. I wonder if I really need to replace the PSU caps in the DAC1 with these...
I'm happy to report that the 2.2uF Auricaps are now residing permanently in my DAC1 (Salas: the impedance is around 8K ohm on my DAC1).
There is no significant sonic change after the 120 hrs break-in period. Most of the differences were heard in the first 2 hrs.
Together with a new powercord (Accustic Arts Ferrite II), the mod is pretty much a done deal for me. The powercord made as much of a difference as the film caps. This is one sonically balanced powercord and it improves pretty much everything. Bass is more dynamic and tight. Vocals are smoother than ever.
I even went in to my dealer friend and compared the sonic signature of my system against a full blown high-end Accustic Arts system (transport, DAC, pre and power amp, all AA hardware with full balanced connections) driving a pair of Triangle Magellan Cello speakers (the entire system price is probably 3-4 times the price above mine) and the sonic signature is remarkably similar.
I just received my Elna Silmic II 1000uF 50V caps. I wonder if I really need to replace the PSU caps in the DAC1 with these...
volume knob on these
Is anyone using the variable volume control on these?
Does anyone know what components are used to implement the variable volume?
Has anyone tracked the minor version changes over the years to these. And whether the DAC1 is improving in quality or what production changes have been made over the years?
Is anyone using the variable volume control on these?
Does anyone know what components are used to implement the variable volume?
Has anyone tracked the minor version changes over the years to these. And whether the DAC1 is improving in quality or what production changes have been made over the years?
Kuro,
The 8k impedance is what I recalled in one of my earlier posts, it seems that we have the same circuit in the place of interest. As you saw, my Auricap recommendation was not hasty. Happy we helped.
As for the Silmic IIs, you can parallel them and report if you like. Since you are having them maybe its worthy just to check. You can get them in and out very easy.
Daveis,
I have used the variable, and its noticeably inferior in transparency, thicker too.
I don't know.
I haven't tracked more than that the V1 couples about 10x the impedance of V2 which is 8k DC.
The 8k impedance is what I recalled in one of my earlier posts, it seems that we have the same circuit in the place of interest. As you saw, my Auricap recommendation was not hasty. Happy we helped.
As for the Silmic IIs, you can parallel them and report if you like. Since you are having them maybe its worthy just to check. You can get them in and out very easy.
Daveis,
I have used the variable, and its noticeably inferior in transparency, thicker too.
I don't know.
I haven't tracked more than that the V1 couples about 10x the impedance of V2 which is 8k DC.
Kuro said:
I played with the orientation too, and tried to listen for those differences on Grado headphones. With small music works I could not tell. Then I used Prokofiev's Romeo and Juliet (Valery Gergiev - Kirov).
Yes when the musical plot thickens there is appreciable gain in focus, slam, and 3D. So the black lead, goes to +pad.
Coupling caps on DAC1 USB
I just got a capacitance meter today (nice unit, brand is called UNI-T, can measure up to 20000uF and only costed me US$22).
Just for the record, I measured the 3 caps in the output coupling stage, they are:
Lytic: 1000uF (this one is labelled)
Film cap (the white one in block shaped): 0.47uF
Tiny ceramic: 100nF
I just got a capacitance meter today (nice unit, brand is called UNI-T, can measure up to 20000uF and only costed me US$22).
Just for the record, I measured the 3 caps in the output coupling stage, they are:
Lytic: 1000uF (this one is labelled)
Film cap (the white one in block shaped): 0.47uF
Tiny ceramic: 100nF
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