Jim you went by the provided PCB groundings with no issues and that's fine too. Your DC offset level and bias matching between channels results are very best. Of course the M3 MOSFETS can differ a lot for IDSS and VGS in production so they are hand picked to be predictable for bias levels with the two different R10 resistor values, and to be close enough in the DCG3 channels.
How high is your bias current beyond its well matched though?
I could only find through Google's cache just a couple of your thumbnails on pink fish media. Your four normal sized ones are broken in your thread there too.
Better use the go advanced answer button that has the attachments menu so to upload pics on our server for posts. Its the only way they are to remain with us.
You can as well link from attachments here their image URL normally to other places on the web by right clicking on them and copying their location.
Attachments
Damn my ancient Leak isodynamic phones have just died on the right channel
As for the vintage Leak isodynamics, what a shame! See if it can be due to a broken connection in the cable or inside them somewhere. If nothing can be done, maybe the only 60s-70s design for looks and tonality that I can think of which is still in production and really worthwhile is the Beyer DT 150. Well priced on Amazon with free UK delivery. https://www.amazon.co.uk/d/Musical-...-AMS-DT-150-250-GREY-DT150-Headset/B000LDPP1K
I've attached input ground at one pcb ground only and output ground at one pcb point only. Should I tie the two input grounds and the two output grounds on the pcb together?
I've got 149.7ma in one side and 147.5ma on the other. A bit high?
Perfect practical bias result both for nominal target and matching. You shoot for the higher bias 150mA level with 7.5 Ohm R10s and that's what you got at a hair's distance. We allow 10% from target and 5% channels mismatch for DCG3's bias acceptable tolerances to have a picture. If you are not comfortable with the heat on your sinks but to can still keep some extra bias try 8.2 Ohm R10s.
See not to make loops between grounds. If they are circling together at the RCA rings also. Use the DMM's continuity to know if a ground wire's end beeps with general ground already for example. There are many wiring ways, follow what's handier to you, but the final pass test always is -no hum & buzz-.
See not to make loops between grounds. If they are circling together at the RCA rings also. Use the DMM's continuity to know if a ground wire's end beeps with general ground already for example. There are many wiring ways, follow what's handier to you, but the final pass test always is -no hum & buzz-.
Another thing now. Your AT headphones are 470 Ohm. Some high impedance models like those are voiced with high output impedance amps also in mind. There are popular headphone drive chips in the industry recommending 10-50 Ohm series output resistors so to protect themselves oscillating on layout and headphones wire capacitance for instance. Manufacturers know that many commercial headphone amps have significant Zo either based on chips or on discrete.
The DCG3 does not care, has proper near zero Ohm output. Maybe its handy now before you finish to put female pins at the RZ pads so to can swap zero Ohm and higher resistors to investigate if your headphones like some less damping factor subjectively. Of course anybody with a finished DCG3 of zero links at RZ can also try that when in doubt by attaching resistors in series at the HP PCB connectors or at the phones output jack.
The DCG3 does not care, has proper near zero Ohm output. Maybe its handy now before you finish to put female pins at the RZ pads so to can swap zero Ohm and higher resistors to investigate if your headphones like some less damping factor subjectively. Of course anybody with a finished DCG3 of zero links at RZ can also try that when in doubt by attaching resistors in series at the HP PCB connectors or at the phones output jack.
Thanks Salas,
Looks like another successful DCG3 build in the wild, making music.
Art Pepper and the rhythm section sounding fabulous right now with vinyl setup.
It might be a while before I button it up! I may be too busy playing music.
Thanks for the tip re headphone damping. I'll do some listening once I install the headphone jack.
Regarding power up, should I attach headphones then power up or plug headphones in once powered up. Sorry for the naive question!
Looks like another successful DCG3 build in the wild, making music.
Art Pepper and the rhythm section sounding fabulous right now with vinyl setup.
It might be a while before I button it up! I may be too busy playing music.
Thanks for the tip re headphone damping. I'll do some listening once I install the headphone jack.
Regarding power up, should I attach headphones then power up or plug headphones in once powered up. Sorry for the naive question!
Great. Nice to know. Its primarily meant to be a decent line preamp for the whole system after all. Post some pics also at a point if you may.
Me I hot plug and unplug my headphones collection to the DCG3 regularly without second thoughts and all of them are still alive. Power up has the DC settling delay relay anyway.
Me I hot plug and unplug my headphones collection to the DCG3 regularly without second thoughts and all of them are still alive. Power up has the DC settling delay relay anyway.
Thank you for the link. They look a good buy. Would I need to change anything as I am currently running[no pun intended] with three times gain and the 10R resistor giving 126 & 130 ma of current?
No. They are 250 Ohm least load and 104.9dB/V wide band sensitive tested. They gonna fly on your DCG3 as it is set.
and final pictures
have installed buttons for volume and menu controls of DAC (I'm using internal volume control of AK4490)
It looks like I have some ''smudge'' on the glass in front of new installed VFD display...but who cares
I think that's it...no more taking it apart
Thanks Salas & Tea
have installed buttons for volume and menu controls of DAC (I'm using internal volume control of AK4490)
It looks like I have some ''smudge'' on the glass in front of new installed VFD display...but who cares
I think that's it...no more taking it apart
Thanks Salas & Tea
Attachments
and final pictures
have installed buttons for volume and menu controls of DAC (I'm using internal volume control of AK4490)
It looks like I have some ''smudge'' on the glass in front of new installed VFD display...but who cares
I think that's it...no more taking it apart
Thanks Salas & Tea
Stunning!!!
and final pictures
have installed buttons for volume and menu controls of DAC (I'm using internal volume control of AK4490)
It looks like I have some ''smudge'' on the glass in front of new installed VFD display...but who cares
I think that's it...no more taking it apart
Thanks Salas & Tea
Excellent DAC/AMP aesthetic result. Are you happy with the tonal synergy of those two?
Thanks people
about sound ( compered to mobile and laptop/PC headphone output) ;
I would say it's less ''stresfull''
I don't have that audiophile vocabulary to describe richness of the sound, heights that tickles your inner ear with the space 3D dimension
It does sound nice, right now I'm lessening at lower volumes that I have used to via PC
It have everything, nothing screams out, it's very well balanced
one thing, which I can't determine right now,is it good or bad, is that I would like it to have a little more bas...but just a little...like in scale on 1-100% I would like to have 5%...maybe I should go with SK170
but the amp haven't play like more than 30h so...
And then again, most of the music I play are mp3
one of those days I'm gonna take it to a friend which have some collection of diy headphone amplifiers and compare it...don't know is it vise idea as he have all those chines kit from ebay (have collection of like 10 of them)...will report results
but really, it's nice balanced dac/headamp combination, very neutral and it's not like stres to listen it for long time...me happy
The heat ''problem''
yesterday was really hot day in Croatia and the amplifier did get really hot after 3 hours of playing...and I was really thinking to make better ventilation on the case
but now that I'm in the office with air condition on (like 22-24*) it's back in ''normal'' (50-60*) so I will leave it this way
about sound ( compered to mobile and laptop/PC headphone output) ;
I would say it's less ''stresfull''
I don't have that audiophile vocabulary to describe richness of the sound, heights that tickles your inner ear with the space 3D dimension
It does sound nice, right now I'm lessening at lower volumes that I have used to via PC
It have everything, nothing screams out, it's very well balanced
one thing, which I can't determine right now,is it good or bad, is that I would like it to have a little more bas...but just a little...like in scale on 1-100% I would like to have 5%...maybe I should go with SK170
but the amp haven't play like more than 30h so...
And then again, most of the music I play are mp3
one of those days I'm gonna take it to a friend which have some collection of diy headphone amplifiers and compare it...don't know is it vise idea as he have all those chines kit from ebay (have collection of like 10 of them
)...will report resultsbut really, it's nice balanced dac/headamp combination, very neutral and it's not like stres to listen it for long time...me happy
The heat ''problem''
yesterday was really hot day in Croatia and the amplifier did get really hot after 3 hours of playing...and I was really thinking to make better ventilation on the case
but now that I'm in the office with air condition on (like 22-24*) it's back in ''normal'' (50-60*
) so I will leave it this way
About bass. The AKG K semi-open studio line has beautiful qualities but its lean enough. Clean and open for the price, efficient, has treble extension, great for Jazz, voice, guitar, has a midbass hump area that helps it round out the mids but its still rolling off more than average in the lows. In other words wait to listen with other headphones too before tweaking anything in the electronics.
About the heat maybe you could cut a large window on the top and attach a black metallic mesh. It will let it breath and the led bars will glow on the ceiling when the lights are low
About the heat maybe you could cut a large window on the top and attach a black metallic mesh. It will let it breath and the led bars will glow on the ceiling when the lights are low