[tacitapproval]

Quote:

Originally Posted by runeight /img/forum/go_quote.gif I don't use DACs from computers so I am far from expert, but it seems that wiatrob's solutions may be the only ones. This is really a ground noise problem and the only way to fix it is to break the ground connection between the dac and the amp. At least that's the only way that I can think of. Perhaps some others can offer other, better solutions.

Thanks for your help. It is actually nearly fixed--despite my not knowing why. It must be magic.

 

[wiatrob]

Quote:

Originally Posted by tacitapproval /img/forum/go_quote.gif Update: Now the noise is nearly non-existent. I didn't do anything, other than leave it running for some time now (a property of warming-up?) I can hear it only with iems and not with my HD650 or DT770 all of a sudden. Why would it fluctuate like this? I guess I should't look gift horses in mouths.

Hmmm. I'd say let it burn in a while more and see if there's a consistency. I am going to assume that the your IEMs are the most sensitive/lowest impedance 'phones you have. My test phones (cheaper earbuds) always pick up a wee bit of noise that I never hear on my other cans...

Posts Crossed. Keep listening. Maybe it was the tubes??

AFA Dac ground loops:http://www.head-fi.org/forums/f46/be...um#post4396311

Looks like it happens with Dacs better than ours.

 

[Hayduke]

Quote:

Originally Posted by runeight /img/forum/go_quote.gif BTW, thanks for the request to put indicators on the e12. As you know I used them on the compact hybrid. It's a very cool feature.

x2

I just returned home from a trip out of town. All my parts are sitting here waiting. I'm hoping to have music through this thing this weekend. Casework may take much longer.

Edit:
Bah! I just looked in my digi key box and I got a silver Hammond case

I wanted black. Oh well I think this will be another push to use the hammer tone paint like Grendel23 did. Of course I'll have to put some black on first. Oh well, casework is always the challenging part

 

[Uncle Bob]

Quote:

Originally Posted by runeight /img/forum/go_quote.gif Uncle Bob you haven't said anything lately about your hiss problem. Is it still there? And have you had a chance to measure voltages? BTW, thanks for the request to put indicators on the e12. As you know I used them on the compact hybrid. It's a very cool feature.

I'm still here, and unfortunately I still have the hiss problem - I just haven't had the opportunity to sit down and work on the board. I will keep you posted on progress - I still have to make an enclosure for it. I can't consider it a finished project until it's all cased up.

I'm really glad that the LED idea has proved popular. I was grateful for the time you took to work out a solution when I requested it and the fact that other people think it's a cool feature makes the time spent worthwhile. Not that I've had time to make the board for mine yet

 

[Hayduke]

Quote:

Originally Posted by Uncle Bob /img/forum/go_quote.gif I'm really glad that the LED idea has proved popular. I was grateful for the time you took to work out a solution when I requested it and the fact that other people think it's a cool feature makes the time spent worthwhile. Not that I've had time to make the board for mine yet

hmmm on a board huh? I was planning to sort of air wire it. I'm only using a single LED to indicate that the circuit is active, so my plan is to have an LED on one end and 2 wires on the other. All the parts will be bundled together into some heatshrink. Heat shouldn't be an issue with these, right? I guess I'll now in the next couple of days. I can't wait to start building. I came back to work early from a trip and I'm wishing I had just stayed home and worked on my amp

 

[wiatrob]

Quote:

Originally Posted by Hayduke /img/forum/go_quote.gif x2 Edit: Bah! I just looked in my digi key box and I got a silver Hammond case I wanted black. Oh well I think this will be another push to use the hammer tone paint like Grendel23 did. Of course I'll have to put some black on first. Oh well, casework is always the challenging part

Which model case is it? I have few black hammonds, PM me if you want to swap...

 

[wiatrob]

Quick followup on the dac noise. OT but it's bugging me. Obtained isolation transformer. Hooked up my Imac and Dac/SohaII to it. Ran only a usb cable from the mac to the dac. Soha has noise when usb cable is plugged in , but only after 3/4 volume travel. Dead silent all the way to max without the cable. Swapped USB cables. Same result.

Very happy TacitA's noise went away though!

 

[tacitapproval]

Quote:

Originally Posted by wiatrob /img/forum/go_quote.gif Quick followup on the dac noise. OT but it's bugging me. Obtained isolation transformer. Hooked up my Imac and Dac/SohaII to it. Ran only a usb cable from the mac to the dac. Soha has noise when usb cable is plugged in , but only after 3/4 volume travel. Dead silent all the way to max without the cable. Swapped USB cables. Same result. Very happy TacitA's noise went away though!

Sorry to hear that your noise remains.

Mine seems to fluctuate, sometimes it is there, sometimes not. It is also only evident past 3/4 travel, so it doesn't affect listening volumes.

What about using a ground lifter on the laptop--is this a bad idea?

 

[luvdunhill]

what about including a CL60 thermistor from analog ground to earth?

 

[wiatrob]

Quote:

Originally Posted by tacitapproval /img/forum/go_quote.gif Sorry to hear that your noise remains. Mine seems to fluctuate, sometimes it is there, sometimes not. It is also only evident past 3/4 travel, so it doesn't affect listening volumes. What about using a ground lifter on the laptop--is this a bad idea?

I can't hear it, so i don't let it bother me. I understand there are those with more sensitive ears here.

Does your laptop power adapter cord have a grounded plug? Many don't...

EDIT: Me thinks this is veering a little off topic here, maybe we should move this thread to the one I referenced earlier if it's truly a DAC grounding issue?

 

[tacitapproval]

luvdunhill -- what about including a CL60 thermistor from analog ground to earth?

I've got a paralleled 10ohm resistor and .1uf cap as a ground loop breaker on the amp's board ground. Is this a different tack? (sorry, I'm still a noob)

wiatrob --I can't hear it, so i don't let it bother me. I understand there are those with more sensitive ears here.

Does your laptop power adapter cord have a grounded plug? Many don't...

EDIT: Me thinks this is veering a little off topic here, maybe we should move this thread to the one I referenced earlier if it's truly a DAC grounding issue?

Yes, sorry for the off topic, but that thread is on the benchmark. Perhaps a new thread?

Yes, my laptop is three-pronged. Is it unsafe to use a ground lifter on a laptop?

 

[wiatrob]

Quote:

Originally Posted by tacitapproval /img/forum/go_quote.gif Yes, my laptop is three-pronged. Is it unsafe to use a ground lifter on a laptop?

The grounds are there for a reason... To keep you and your gear safe and to keep your house form burning down. A real Electircal Engineer and/or expert in the National Electric Code could answer all the technical reasons.

It's all a a matter of risk - if you poured some water on the power adapter, it would be more dangerous without a ground. Will it become an electrocution hazard on it's own? Unlikely...

 

[Hayduke]

Since most (all?) laptops have a power block, the ground on that third prong ends there. Once it hit's the transformer, it's not doing anything. Waitrob has it right. That third prong is to help avoid a shock of something goes wrong. So short answer, it's fine to run the laptop that way. If you have an extra of the cord that goes between the power block and the wall, just break off that third prong. I did this to the power source for my Starving Student to try and get rid of hum, but it had no effect

/\_/\_/\_/\_/\_/\_/\_/\_/\_/\_/\_/\_/\_/\

Well I finished building my amp tonight, sorta. Other then the part I missed in my order

Funny part is, it was mentioned that P1L and P1R were missing from the BOM. It got added, but it is listed incorrectly as P2R and P2L. There are 2 items for those locations. When I was building my BOM I think I deleted the 200ohm trim pot thinking it was something that had been changed. I didn't notice there was no P1R or P1L.

Oh well, I was really hoping to listen to it this weekend, but I'm too cheap to pay for 2 day shipping for $5 in parts lol I guess it will be sometime midweek before I get to hear it. I already placed an order with Digi-Key for the trim pots. Naturally I was able to find other things to order.

FYI, if anyone is thinking about socketing Q1-8, it's a major PITA! The sockets for Q6 and Q7 aren't too bad, but I used the same DIP sockets as the test points for all the TO-92 transistors. So 6 per channel, 3 pins each. That's 36 tiny little sockets to solder

Also I discovered my tube sockets don't have a hole through the center for the LEDs

There are some silver circles where the holes should be. I poked at them hoping it was just some thin foil-like cover, but no luck. I might take a drill to them if I decide I have to have the LEDs under the tubes. Otherwise, I might just use the 3 LEDs to light up the inside of the enclosure and have it shine through the ventilation holes.

 

[rds]

Wiatrob -

You've probably already gone through this, but I'm wondering if the one of the standoffs might be in contact with the DAC's ground plane? That could create a ground loop with the earth grounded case. Similarly could the usb jack or exposed part of the usb cable be touching the case?


Quote:

So short answer, it's fine to run the laptop that way. If you have an extra of the cord that goes between the power block and the wall, just break off that third prong.

I have to take exception that. That is bad advice. The power supply is grounded for a reason. It is there in case the neutral were to get broken at some point (in the cord, the wall, a power bar etc).
Also, just having a 3 conductor cord with the ground removed laying around is a hazard in itself. Who knows what someone else might try to use it for not noticing that the ground has been cut.

 

[Beefy]

Potentially stupid idea coming up......

Is it possible to transformer-couple a USB connection?