"The Wire" Ultra-High Performance Headphone Amplifier - PCB's - Page 134 - diyAudio
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Old 17th January 2012, 05:03 PM   #1331
qusp is offline qusp  Australia
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yeah pretty much, its what i had in the post above before cutting it out because i couldnt be bothered and because i'm sick of looking like a grumpy bastard for trying to make people do the most basic thing, i simply cannot begin to understand the psychology at play here.

other than the wiki, but even with the wiki its been repeated here that at the minimum they would have to wait in line after previous requests and till after the current GBs were all sent out and the dust settled. plus the other GB's have said sold out for ages and it doesnt stop it...

but yes, now that i know there is nothing at all left, i can safely ignore it and hope they eventually find the info right in front of them, instead of repeating the request


definitely time to start a new build thread though!! this ones so full of useless posts including mine in response and preemptive strikes, frustrated aaaargghhs hehe. when my kits show up i'll do it, hey havent heard from you on my email, did you send my headamp pcbs in the same batch as hochopeper? his arrived mid last week and hes just up the road. or did you hang on to ship with the poweramp afterall? all good, i've just been hangin out for them since his arrived, just checking, but if you are sending all together i'd like to arrange and pay for express or similar if possible. Chris will throw in a few bucks i'm sure

Last edited by qusp; 17th January 2012 at 05:14 PM.
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Old 17th January 2012, 09:57 PM   #1332
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Quote:
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this ones so full of useless posts including mine in response and preemptive strikes, frustrated aaaargghhs hehe.
Don't forget the SIGHS!!

Quote:
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but if you are sending all together i'd like to arrange and pay for express or similar if possible. Chris will throw in a few bucks i'm sure
Just send word what my share is for the pcbs and it'll be sorted.
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Old 19th January 2012, 05:48 PM   #1333
opc is offline opc  Canada
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Hi Guys,

Several people have asked about the output impedance on the LPUHP amps and the headphone amps so I took some time to measure them. What is presented here was measured on a BAL-SE amp, but it applies equally to the SE-SE. I didn't get a chance to measure the BAL-BAL, but I'll try to get to it tomorrow.

I used the dV/dI method to measure this which is the most accurate method I know of. You basically set the output voltage to a known level with no load, then connect a load and measure the difference in voltage at the output. This is then divided by the difference in current between no load and load, and that gives you the output impedance of the amplifier.

This method is most accurate when more voltage and more current is used, but it's also important not to clip or current limit the amplifier. In this case, I used an output voltage of 6 VRMS into a 37.4 ohm load. It's also important to measure the actual current and not just calculate it based on the voltage and resistance. Here are the results:

V (open load) = 5.998 VRMS (measured with AP and a calibrated Agilent meter)
V (37.4 ohm load) = 5.996 VRMS (measured with AP and a calibrated Agilent meter)
I (open load) = 0A
I (37.4 ohm load) = 0.16018 ARMS (measured with a calibrated Agilent meter)

So we have 2mV of voltage delta and 0.16018A of current delta. This gives:

output impedance = dV/dI = 0.002V/0.16018 = 12.5 milliohms.

That gives a corresponding damping factor of 2560 with a 32 ohm load or 48000 with a 600 ohm load.

All measurements were done at the actual output terminals of the amplifier. To get the damping factor with actual headphones attached (at the driver), you would need to account for the DCR of the cables and connectors in series with the output impedance.

Overall, the output impedance of the amplifier is completely insignificant in comparison to the resistance of the cables, connectors, and likely even the copper leads of the driver itself.

Cheers,
Owen
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Old 19th January 2012, 06:21 PM   #1334
qusp is offline qusp  Australia
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what say you to those that say such a low impedance output will cause resonance with some headphones due to electromechanical impedance of the output->headphone driver interface? at the moment it is being claimed that Grados perform better with an output that puts it closer to a current source

i cant see how an open back 28ohms driver could present any meaningful resonance as to create distortion artifacts due to having essentially perfect damping factor
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Old 20th January 2012, 06:40 PM   #1335
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Hi Owen,
I just wanted to take a quick opportunity to thank yourself for organizing the GB, my neat package arrived safe and sound last week here in Sydney.
Problem is I have so many projects going on at the moment I haven't started the build process yet.
I am really looking forward to listening to this wee beastie.
Thanks again guys and qusp I am feeling for you having to constantly repeat things, I'm surprised that some people are members of these forums yet are so much against actually reading.
For must of us that were not here from the start of this thread it took a number of days to catch up to the present day , but I guess some people just want the juicy bits.
Thanks guys

Archie
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Old 23rd January 2012, 12:59 PM   #1336
zeffa is offline zeffa  Australia
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Default Need some help with SE-SE build

Hi guys, first of all thanks to Owen for providing these awesome amps! I'm nearly done with mine, but have run into some trouble, so its time to ask the diyaudio hivemind for some troubleshooting advice...

I've finished putting together my boards complete with temporary wiring (while waiting for the final case to arrive). I tested the PSU yesterday which to be seemed working correctly. I adjusted the voltages to +ve & -ve 12.5v, which held fine. The heatsinks didn't get particularly hot when not loaded.

Today, I finished wiring the SE-SE board to the PSU and inputs and outputs. I plugged it in a pair of sacrificial headphones but all that I could hear was a loud hum out of both sides. Adjusting the pot made no difference and no music came out. I also noticed the PSU heatsinks and the transformer itself were getting very hot (>60 degrees C), though the LME49600s were hovering under 40 deg C. I turned it off and rechecked the PSU and it was still putting out +/-12.5V. I checked for cold solder joints & reflowed a few on the PSU. The joints on the SE-SE seemed ok? I've included some photos below.

I'm not quite sure where to go from here in terms of troubleshooting. Any suggestions? Cheers!

Photos
PSU:
Click the image to open in full size.
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SE-SE:
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Old 23rd January 2012, 01:42 PM   #1337
qusp is offline qusp  Australia
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can you reload those pics at higher resolution?

have you tested for shorts to ground ie test with your multimeter across both the power supply inputs + -> G and - -> G and the same for the signal inputs and outputs. we had a similar sounding problem a couple pages back with the same amp (SE->SE) where there was a borderline short to ground due to a scratch made in the soldermask and clearance being too low when combined with a little too much solder

Last edited by qusp; 23rd January 2012 at 01:46 PM.
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Old 23rd January 2012, 01:48 PM   #1338
qusp is offline qusp  Australia
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also check your standoffs arent causing a short, they look a bit large

did you check for DC at the output at any point before connecting the headphones?

what is the discoloured ring around this right side top heatsink post? is that just flux?

Click the image to open in full size.

also @ Archie, thanks for the condolences =)

Last edited by qusp; 23rd January 2012 at 01:55 PM.
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Old 23rd January 2012, 02:01 PM   #1339
agdr is offline agdr  United States
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Quote:
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have you tested for shorts to ground ie test with your multimeter across both the power supply inputs + -> G and - -> G
zeffa - if qusp's test shows that one of your power supplies is dead shorted, check to see if the solder on one side of C29 on the back of the board has accidentally slopped over onto the via hole in front of it. That happened to me! Luckily I did test power supply to ground resistance before applying power and caught it in time. I didn't do a very good job centering that capacitor on the pads the first time.

As it turns out most of the via holes next to the caps on that board seem to just connect to the cap ends, so less of a problem if the solder bridges. But for that cap and the similar one on the other channel one of those two via holes next to the cap is ground.
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Old 23rd January 2012, 02:50 PM   #1340
zeffa is offline zeffa  Australia
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qusp - Larger images here. The standoffs don't appear to be shorting anything. Ring around the top right heatsink post is flux. Power supply out at the PSU wasn't shorting when I tested it unconnected to the amp. Power supply in at the SE-SE is also not shorting when unconnected to the PSU. With them both connected, I measure around 2k resistance between both +ve and G & -ve and G?? With power on, the DC offset >200mV both outputs :S (but strangely measure 0 when I switch the multimeter to 2v DC?).

agdr - C29 doesn't seem to be shorting to the middle via (of the three next to it).
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