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"The Wire" Official Boards for All Projects Available Here! BAL-BAL, SE-SE, LPUHP

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#481
Silly question here. Can you hook up a DC-coupled DAC to a DC-coupled amp? My guess is that the answer is yes, with a small amount at the output. If so, does that NTD1 version have the option for attenuation or will I need a preamp?
 
#483
Brought forward ...

Powderclear: once OPC sees your order he'll move it over to the list below & will PM you a payment request... remember its in Canadian Dollars 🙂


opc said:
Hi Guys,

Well, it's the time we've all been waiting for... payment and shipping time!

Everyone on the list will receive a PM by the end of the day today with my email address for Paypal, a copy of the instructions below, and a link to this post. Please wait until you get the actual request to make payment.

The only significant change is that the NTD1 boards have been removed from the order sheet, and I have noted those orders in a separate spreadsheet. I am doing some major rework on that circuit, and I don't want to sell people a bunch of boards and then release a brand new version a month later. I will deal with the NTD1 orders at a later time.

Please follow the instructions below very carefully, as deviating from them makes everything much more difficult for me, and will result in your order being delayed! Please be sure to read all of the instructions before making a payment.

Step 1:

Go to the following shared spreadsheet and confirm your order:

https://docs.google.com/spreadsheet/ccc?key=0AnMLwB9mdXl2dFlBRGZZX1BNZGRSM1FnZGw5V3gyVWc&usp=sharing

You are welcome to make changes to your order by adding or removing boards, or cancel your order entirely by removing your name and order from the list.

The list will automatically calculate your new total, so please make all necessary changes and get your correct total before making payment.

Note that this list is not for new orders, but simply to summarize and track existing orders. If you have a new order to place, please do so on the original list linked in the first post.

Step 2:

Make payment for the total given in the list via Paypal to the email address provided in the PM or email you received.

Be absolutely sure to do the following when you make payment:

1 - Always include your diyAudio username in the "notes" or "message" section
2 - Always include your full address, exactly how you want it written on the envelope, in the "notes" or "message" section.

Step 3:

Check back on the list posted above to see the status of your order in the "paid" or "shipped" column.

All orders will be processed in the same order as payments are received. That means people who pay first, will have their orders shipped first, regardless of the order of the list.

Please do not make order changes on the list after you have made payment. If I see a discrepancy between the payment made and the total listed in the spreadsheet, I will not ship the order until things have been clarified which will result in long delays.

That's all!

If you have additional items with your order, I will include the additional amount to be paid in the note I send to you. This only applies to the few people who bought leftover lateral fets or LME49830 drivers.

Cheers,
Owen
Click to expand...

|-O-|

Loving the multiple choices for the NTD1 ... which variant is used with the DAC?

Paul
 
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#485
opc said:
I'm also considering doing a P-channel variant that is DC coupled and doesn't use caps or an op-amp on the output. The downside is that output voltage swing is limited to about 500mVRMS. This might be perfect for some headphones, so it will probably be done separately as a headphone specific option.
Click to expand...

Summary/TLDR: this post is all about praising the P-Channel no caps no amp op NTD1 version that Owen is considering.

I'm gonna try soon a SE and Balanced Wire with unity gain - that should be the ultimate objective performance of op-amp powered headphones amplifier.
But as an open minded curious guy, I'm already thinking what else I could try next for subjective performance, and the P-channel for Headphone Application is exactly what I was looking for: a high performance circuitry for headphones with no aop and no caps in the signal path, usable straight out of current output dacs.

I know it might not be very commercially popular... where "MOAR POWER" is always the rule. But I stated that my current setup has at least 40DB of wasted gain... and I guess I'm not alone in that case.

So I'm looking for a "perfectly tailored mate" for a circuitry such as
Usb => ESS Dac (Wire Dac ? 😀 ) => High current / Low voltage / Very low Z-out for
high-end / high sensitivity Headphones. A diy box with no "redbook" line level outputs - just a pure high end all in one mate for headphones.

My Fostex TH-900 has a Sensitivity of 100dB / mW, Low impedance of 25ohms and 1.5 Tesla magnet to move (they needs current and very good damping factor)...
This kind of setup might also be popular among the always increasing high end (custom) IEMs owners.

Thanks for reading my noobish 2 cents.
 
#488
Hi, following all the praise I could read about the LPUHP on a french forum, I added myself to the spreadsheet for those.
Also interested with the regulator boards when these will be made ready to order. What would be the expected timeframe for those?
 
#489
BuildMeSomething said:
Couldn't find any anomalies and took a chance on plugin-in the Senn HD-650s... There is a 'Tick' on power up and 'Pshhh...' on powering down, but not at a level I'd consider damaging to the phones. So full speed ahead.
Click to expand...
hi opc,
curious what your take on this is - have you scoped it out and confirmed that it's at a safe level? it seems so to me, but there's also an excursion sound that precedes the pshhh at power off that might be some dc.
thanks,
-matt
 
#491
psu trouble

hi,
i had a working wire+psu, and... i swapped out the clip on heatsinks i was using for those in the bom, along with isolation pad + washer.
two blown 50ma fuses later, i'm not sure where the issue is. initially i'd measured a high varying resistance (2kohm) between the tab and gnd due to the capacitors i guess, but now i'm seeing ~8-9ohm tab to ground 😕. i'd see 0 if there was a short, right?
if i did short it out, is there any probable damage to the attached se wire i have?
-matt
 
#493
That is some very odd behaviour. Are you using an insulating washer and being careful not to snug things up too tightly?

The anodized coating on the heatsinks can present a few ohms of resistance when the tab of the regulators short to it.

Perhaps try a new pad, and make sure you're measuring in the 1000 ohm rage or more.

Cheers,
Owen
 
#495
yep i was using the pad/washer per the bom.
i got it going with the spare pad and nylon screw/nut. seems ok.
maybe it was over torqued, or there was a slight angle, or perhaps the pad was faulty. close tolerances there, closer i think than my construction techniques provide. i think a longer washer would help.

in terms of how it affected the wire downstream, should i just imagine an 8ohm resistor placed between the v+ output terminal and ground? i worry about the amp seeing 0v where it expected 15v, and the potential issues there.
thanks,
-matt
 
#496
I wouldn't worry about the amp downstream... lack of one rail won't hurt anything.

I would imagine the regulator just went into current limit and blew the fuse.

Glad you got it back up and running!

Cheers,
Owen
 
#497
here's the completed build. i went with a gigaworks stepped attenuator which provides good channel balance and has a nice feel. still need to find a suitable knob, though 🙂.
it's running in unity gain and is fed by a subbu dac. i scoped out my normal listening level and found that i'm actually listening below the output level of my dac with my akg 271 cans, about 1.2v rms vs the 2.0rms they provide. on my other amp i was throwing away most of the signal. cranking it to max at unity gain feels like it'd blow out the headphones honestly, i'm at about 50-75% max.
the board level connections are standard .064" square post headers using ampmodu wire interconnects. they aren't as snug as i'd like but pass the signal just fine.
one thing that would've made things easier is marking the holes for the standoffs before completing the boards 🙂 maybe next time i will remember to do that.
thanks for a great amp.
-matt
 

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#498
Great looking build! I like the signal input, output and volume on the front 🙂

Overall the layout is very good, and everything looks nice and tidy.

As a "top tip" twisting wires together helps reduce the amount of noise picked up and the amount of noise radiated out, so if you ever have it apart, it would be worth twisting the AC inputs and outputs of the transformer together tightly in current-carrying pairs.

If you can't hear any 60Hz hum as it is though, then it's probably not worth the trouble.

As for the gain setting, I congratulate you on sticking with unity. As you mention, it's usually more than enough for almost any setup, and unless you have a DAC with very low output, or headphones that are very hungry, unity gain is probably more than enough. If you consistently listen around 75%, then you're right where you should be for system gain.

Cheers,
Owen
 
#499
i ought to be able to twist the secondaries - but that thick yellow wrap talema put on the primaries would make it difficult to get a good twist on primaries. maybe it could be carefully removed but operations like that tend to take insulation with them in my experience.
sticking everything on the front panel was an attempt to minimize any 60hz pickup. so it'd make sense to take care of the secondaries. i can't hear any hum, i bet my adc would though ;-)
-matt
 
#500
A nice & tidy looking build, glad to see you were able to successfully trouble shoot the PSU problem 🙂

|-O-|

Big weekend ahead... Had the first play of the miniSHARC front-end this morning & will finish wiring in the 2nd DAC tonight... New 8" woofer speakers will be in working order tomorrow... Then full on listening with the 2-way set-up in place, with the LPUHP amp powering the FH3 speakers ... can't wait 🙂

Paul
 
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