New HQ DIY DAC

[Deleted]

Hi Shaun
If it works as well as mine does, it would be a shame to lose the added inputs and push buttons. I'm not great with metal work either , but the front turned out O.K.
If I had to do it again though, I would get a complete Altronics kit with prepunched and labelled case.
The push button LEDs are small blue ones, and not overpowering.
I use one Optical input from my 40"LED TV, and the coax SPDIF from my Oppo DVD-A/SACD player.I occasionally use the other optical input for the WD TV Live via USB stick plugged in, or for the odd BluRay movie from my LG BR player. Movies like Avatar fill the whole room with sound via this DAC, despite only front stereo speakers.
Alex

P.S.
At least a JLH for the +-15V supply to the DAC PCB is a must with this DAC, otherwise it sounds pretty flat, and no better than a reasonable CD player.

[Deleted]

Apr 24, 2011 10:21:27 GMT @sandyk said:

Hi Shaun
If it works as well as mine does, it would be a shame to lose the added inputs and push buttons. I'm not great with metal work either , but the front turned out O.K.
If I had to do it again though, I would get a complete Altronics kit with prepunched and labelled case.
The push button LEDs are small blue ones, and not overpowering.
I use one Optical input from my 40"LED TV, and the coax SPDIF from my Oppo DVD-A/SACD player.I occasionally use the other optical input for the WD TV Live via USB stick plugged in, or for the odd BluRay movie from my LG BR player. Movies like Avatar fill the whole room with sound via this DAC, despite only front stereo speakers.
Alex

P.S.
At least a JLH for the +-15V supply to the DAC PCB is a must with this DAC, otherwise it sounds pretty flat, and no better than a reasonable CD player.

Hi Alex

point taken with the push buttons but the thought of getting those buttons lined up on the front panel neatly just gives me the shivers. maybe I'll order six front panels to give myself an even chance of success.

only two JLH Alex no no no

on the JLH front i count 2x 15V +/- (4 of Wills boards) and 2x 5V +
(2 of Wills boards). i think that Will's nice JLH will really come into their own here ans save plenty of space when stacked. so i have just enough Toshiba's and transistors for that. so looking good.



take care

[Deleted]

Hi Shaun,
I read this thread yesterday and might be tempted to go along with you on this one.
My hope would be to go my way as much as possible. However most of what the lads are doing along with Alex is way beyond my ken. I'd rather have a final modded circuit to work with but it certainly looks as if this could be fun to attempt.
I tried a quick and dirty hookup of Alex's preamp and my Quad 405.....nearly blew the roof off so I'll need to implement the line level control into the Quad to throtttle it back and get some explicit instructions from you all on what I should be doing between the preamp and power amp. The great Alex Kethel sound was there but I've got a fair bit of noisey hum along with it.
Alan

[Deleted]

Apr 25, 2011 14:28:17 GMT drymdrum said:

Hi Shaun,
I read this thread yesterday and might be tempted to go along with you on this one.
My hope would be to go my way as much as possible. However most of what the lads are doing along with Alex is way beyond my ken. I'd rather have a final modded circuit to work with but it certainly looks as if this could be fun to attempt.
I tried a quick and dirty hookup of Alex's preamp and my Quad 405.....nearly blew the roof off so I'll need to implement the line level control into the Quad to throtttle it back and get some explicit instructions from you all on what I should be doing between the preamp and power amp. The great Alex Kethel sound was there but I've got a fair bit of noisey hum along with it.
Alan

Hi Alan

i don't remember the 405 being that sensitive but it's possible that it is. I'll have a look round to see if i can find some specs for it,

I've got 120 (more voltage swing less drive current)for the HA and 68r (more current drive and less swing) (have i got that right guys) for the pre with a relay switcher. I'd be really surprised if it was the OP load resistor and would think that the IP sensitivity of the amp may be at play here, just out of curiosity how have you got the HA/PRE hooked up to the quad? is it through the 5 pin din connector or through the tape or Aux?i know for sure that the tape monitor section was more sensitive to allow for the low OP of most tape machines.

I've not tried the Class A as a pre yet so can't comment on how it would work. but i don't remember the Class a having loads of gain X 3 if i remember rightly but i cant be sure on that so if anyone is more clued up some input would be great.

so I'll bob of to try and get some specs on the quad and get back to you.

take care

[Deleted]

Hi Alan

I've just checked out the IP sensitivity for the 405 and it's HOT @ ,5V for full OP. i did find some mods to bring it down to a more usable 1.5V so I'll dig round and see what i can find.

take care

[Deleted]

Hi Alan

i found this place which goes into QUAD mods in quite some depth

www.quadmodsusa.com/405upgrades.html

but it depends how far you wand to go with it. it's an interesting read all the same,

Quick and dirty?

if your not inclined to open the box then a simple Lpad (voltage divider) may do it.

what I've done in the past is to buy a cheap log pot and wire it between pre and power. start with it set low and turn it up slowly until you get the desired OP level and then disconnect the pot (switch off the pre/power first ).

measure the resistance between wiper and input and wiper and ground. this should put you in the right ball park for making the Lpad. then go by some nice resistors @ the measured values and make up the Lpad and job's jobbed.

I'm making up a T amp in a few days so I'll try the class a as a pre for sure. I'll let you know how that goes.

hope that is useful and makes some sense.

let us know how it goes

take care

[Deleted]

Hi Shaun
think this topic is better in the AKHA thread
going there now
Alan

[Deleted]

Hi All

I'm just about getting to the PSU testing stage and was wondering what sort of current i should be looking to pull through the AK cricket?

any tips would be greatly appreciated.

take care

[Deleted]

May 2, 2011 11:05:59 GMT @shaun said:

Hi All

I'm just about getting to the PSU testing stage and was wondering what sort of current i should be looking to pull through the AK cricket?

any tips would be greatly appreciated.

take care

Shaun
Ididn't check the current draw, but if it is the dual Cricket, I would expect <30mA per section.Just feel how warm the I.C. gets.
To be on the safe side I attached a mini heatsink, but I don't believe it was necessary.
Alex

[Deleted]

May 2, 2011 11:10:56 GMT @sandyk said:

May 2, 2011 11:05:59 GMT @shaun said:

Hi All

I'm just about getting to the PSU testing stage and was wondering what sort of current i should be looking to pull through the AK cricket?

any tips would be greatly appreciated.

take care

Shaun
Ididn't check the current draw, but if it is the dual Cricket, I would expect <30mA per section.Just feel how warm the I.C. gets.
To be on the safe side I attached a mini heatsink, but I don't believe it was necessary.
Alex

Hi Alex

Thanks for the advice I'll keep the temperature in mind when i fire her up.

so just the control panel to do now and then I'll start testing the PSU's and JLH. if all goes well i should be up and running within the next few days.

I'll post some pictures and report back

take care

[Deleted]

Hi All

i had my first power up of the PSU today and all seems to be fine.

all of the voltages where within tolerance and the crickets are working well with 3.29v on each of them (un loaded). i did cheat slightly by using some VR's set to 2k7 and initially got 3.29 on one side and 3.25 on the other so just tweaked up the low side sightly.

it's been running for around 4 hours and it's rock solid.

all of the boards are built and i only have the Grey cables to sort so should be good for the final test procedure tomorrow.

so looking good.

take care

[Deleted]

Hi Shaun
Carefully align the IDP cables before crimping, and squeeze the plugs fully closed with gentle pressure from the jaws of a vice.
They can cause lots of niggly little problems if you aren't used to assembling IDP cables.
Alex

[Deleted]

May 4, 2011 21:49:34 GMT @sandyk said:

Hi Shaun
Carefully align the IDP cables before crimping, and squeeze the plugs fully closed with gentle pressure from the jaws of a vice.
They can cause lots of niggly little problems if you aren't used to assembling IDP cables.
Alex

Hi Alex

thanks for the advice as the cable assembly was becoming the worry of the day.

I've allowed time for that task with no distractions so I'm hoping that it goes well.

I'll buzz all of the pins before i go anywhere near powering up the boards.

take care

[jeffc]

Hi guys,

Shaun now building this SC-DAC kit has embarrassed me into finally lifting mine off the board it's been sitting on for the past year or so and doing something about getting it into one of those 4 vt4c cases I bought when I needed one for the AK Class HA. As usual this is proving a big test of my patience. That aside, I have a BNC socket for coaxial SPDIF input I was thinking to install in addition to an RCA socket so that I have the option of using either. The problem is that unlike the RCA socket, the BNC socket does not have washers to insulate the return/screen wire from the chassis. As I don't know, is insulation from the chassis essential? And I suppose this might be influenced by whether the IEC earth wire is connected to the chassis.

cheers.. jeffc

[Deleted]

Jeff
If you are using a through hole mounting type of BNC socket, with a 9.5mm clearance hole,e.g. something that looks like Jaycar PS0658 you should be able to use the insulators from a Jaycar PS0275,6,7,8 Gold RCA chassis socket.
You could also use a PA3564 BNC plug to RCA socket adaptor for leads with RCA plugs. Don't forget though that if you are going to the trouble of a BNC socket for better matching to 75 ohms, that Jaycar and Altronics aren't too helpful with whether they are 50 ohm or 75 ohm types. You will need a lead with 75 ohm BNC plugs too.
Perhaps Element 14 or R.S. for the sockets ? Look for 75 ohm types.
Alex

[jeffc]

Thanks Alex,

That Jaycar BNC socket looks the same as mine, and I have a stack of gold/nickel plated RCA sockets with plastic insulators I could pilfer, however these are ~1 mm too small in dia to work with the thread dia of the BNC socket, which BTW is specified as 75 ohm. I’ll see what I can bodgie up. The reason I’m somewhat confused though is why all BNC sockets don't come with insulators, and why my Trends UD10 USB-SPDIF converter uses an insulated RCA but the BNC socket isn't insulated ?

diykits.com.hk/Trends%20UD-10.htm

cheers.. jeffc

[Deleted]

The reason I’m somewhat confused though is why all BNC sockets don't come with insulators, and why my Trends UD10 USB-SPDIF converter uses an insulated RCA but the BNC socket isn't insulated ?

Hi Jeff
It doesn't make sense, does it ?
I am guessing that they more than likely used the BNC socket that way because it didn't come with insulators, especially if the RCA socket has the same function, and is insulated from chassis !
Alex

P.S.

Unique digital outputs (optical x1, coaxial x2 (RCA & BNC), AES/EBU x1)

Don't forget that these are individual outputs, each with it's own output transformer.
They are not in parallel like you would need to do with the SC DAC.
Doing that would destroy any advantage of using a true 75 ohm BNC connector.

[jeffc]

Don't forget that these are individual outputs, each with it's own output transformer.
They are not in parallel like you would need to do with the SC DAC.
Doing that would destroy any advantage of using a true 75 ohm BNC connector.

Hi Alex, yer the Trends UD-10 is confusing. To your comment above, even it I run separate wires from the RCA socket and from the BNC socket direct to the PCB attachments points for the PCB-mouint RCA socket I've now removed? That was my plan to use either/or RCA- or BNC-terminated coaxial cables. Not that I expect BNC to sound better, but technically it should meet the SPDIF standard more accurately.

cheers.. jeffc

[Deleted]

Hi Jeff
I would suggest using only the 75 ohm BNC socket, and use the adaptor to connect RCA leads.
Alex

[jeffc]

OK Alex,

Plan B, connect the PCB to RCA socket with wires long enough to also reach the BNC socket for when I should I ever get the desire and BNC cables to pay about with this. Bodgie washers to insulate the BNC socket from chassis, move on and get this DAC cased and working so can enjoy my DML panels again.

cheers.. jeffc

[Deleted]

Plan B, connect the PCB to RCA socket with wires long enough to also reach the BNC socket

Twisted of course .

[jeffc]

Bugger you Alex , I was hoping to use naked, untwisted, 0.5 mm dia solid core silver.

[Deleted]

Nice to know I'm not the only one dragging my butt on this one.

Well some good activity today. After consulting with Alex I've brought mine almost completely up to full tweak spec!

The only things missing are BNC digi in, ( which may never happen after a few years of making up leads for piggin' Naim amps, I got to hate BNCs )
The Xtal mod, which I was deliberately leaving to last to see if it, alone, actually makes an improvement.
Plus the small matter of a proper chassis and a major tidy up of leads etc.

So I have just replaced the LM7805 with a 5v JLH, added to extra JLHs and replaced the two 3.3v feeds with JLH backed "AK Crickets".

I did these individually in stages but in close succession. It was really good to hear the sound so obviously improve with each mod. I reckon the JLH/Crickets is the biggest jump though, a sudden turbo boost of energy/life/control/accuracy.

One very happy bunny!

So here it is in all its fugliness. Does it qualify for the "snake pit" contest

[jeffc]

Hey Chris,
Excellent work there, looks great with all those stacked JLHs and the AK Cricket that looks to be a dual PCB. Makes my p-to-p Crickets look a little bodgie in comparison. Are there any more hiding in your closet. And glad you took the time to listen to how each reg improved the sound, its been so long for me I've pretty much forgotten, but I remember it being a fun time.

I'm going all out with casing, boards are being mounted to a 5 mm thick aluminium plate that will be 3M tape damped underside with wool felt damping between it (with 10 mm stand offs) and the case bottom, which is flimsy 1 mm thick steel. I wouldn't have been so concerned but the case is so large I didn't like the idea of mounting PCBs directly to the flimsy case bottom plate.

For digital, I like the idea of as 'acoustically dead and ringing/resonance free' as possible, which I hope I can achieve, particularly as my SC-DAC is destined primarily for use with my panel speakers. Might take me a week or so before I'll be happy to show pics. Bloody day job keeps getting in the way.

cheers.. jeffc

[Deleted]

AK Cricket that looks to be a dual PCB. Makes my p-to-p Crickets look a little bodgie in comparison. Are there any more hiding in your closet.

Jeff,

Yes I do have another dual pcb. Is your work address still the same as when you sent the Xtal and good to send to?

Bloody day job keeps getting in the way

A bugger that, innit!


Cheers,

Chris