1101 Audio custom crafted headphone amps
Feb 21, 2021 at 12:21 PM Post #571 of 793
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I found those meters :wink: We had a bit of "trial and error" getting them to work properly, but I'm glad Mischa did as they do look nice.
Maybe I should add one of those to my rack... :thinking:
1613927608977.png

Poor man's VU meters...

You are teasing us tho..... by only showing one...
My "interesting" amps (i.e. not counting pedestrian Lyr3 and the such) are 2 Glenns (6EL3N and GOTL), 2 Cavallis, and a custom 2-in-1 eStat amp :L3000:
 
Feb 21, 2021 at 1:28 PM Post #572 of 793
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Feb 21, 2021 at 1:41 PM Post #573 of 793

A2029

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Mischa - are you using a stereo 1/4" male (into BH headphone jack) --> 2 x mono 1/4" males (into M4's "LINE IN" on the back)?
Something like: https://www.amazon.com/Tisino-Stereo-Y-Splitter-Return-Insert/dp/B07K59P692/

That cable will work. On your amp you also need to provide a load similar to what the amp will see. An easy way to do this is if you have a 4pin XLR out as well as the 1/4" out on your amp, then you can buy a male 4pin XLR connector and solder in some 300 ohm resistors for each channel (to mimic a 300 ohm Sennheiser or ZMF load). Plug that 4pin XLR connector with resistors in at the same time as you are running the 1/4" out to the Motu.
 
Feb 21, 2021 at 4:46 PM Post #576 of 793
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That cable will work.
If you recommend a different one - I am all ears! :wink:

On your amp you also need to provide a load similar to what the amp will see. An easy way to do this is if you have a 4pin XLR out as well as the 1/4" out on your amp, then you can buy a male 4pin XLR connector and solder in some 300 ohm resistors for each channel (to mimic a 300 ohm Sennheiser or ZMF load). Plug that 4pin XLR connector with resistors in at the same time as you are running the 1/4" out to the Motu.
Wait... Why not just use a 300 Ohm headphone instead of dummy load on the XLR jack?
 
Feb 21, 2021 at 8:09 PM Post #578 of 793

A2029

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If you recommend a different one - I am all ears! :wink:

Nope, that one should work great!

Wait... Why not just use a 300 Ohm headphone instead of dummy load on the XLR jack?

You can definitely do that as well if you are only testing each tube or amplifier swap at a specific frequency. That would give you the particular distortion measurement at that specific frequency for that specific headphone. But as jonathan says, the impedance of a headphone will vary with frequency, so a frequency sweep (for measuring frequency response and distortion measurement across frequencies) would be affected by the headphone plugged in.
 
Feb 21, 2021 at 8:28 PM Post #579 of 793

bcowen

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Feb 21, 2021 at 10:15 PM Post #580 of 793
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You can definitely do that as well if you are only testing each tube or amplifier swap at a specific frequency. That would give you the particular distortion measurement at that specific frequency for that specific headphone. But as jonathan says, the impedance of a headphone will vary with frequency, so a frequency sweep (for measuring frequency response and distortion measurement across frequencies) would be affected by the headphone plugged in.
Got it. Maybe I should build a load box, like the one @L0rdGwyn uses... :thinking:
 
Feb 22, 2021 at 1:17 AM Post #582 of 793

Xcalibur255

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I rather like the decibel meter implementation on my Luxman amp. I feel as far as meters go this is one of the more practical ones to have as it shows you visually how much headroom you have left at the volume level you are currently playing at.
 
Feb 22, 2021 at 2:00 AM Post #583 of 793
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You can definitely do that as well if you are only testing each tube or amplifier swap at a specific frequency. That would give you the particular distortion measurement at that specific frequency for that specific headphone. But as jonathan says, the impedance of a headphone will vary with frequency, so a frequency sweep (for measuring frequency response and distortion measurement across frequencies) would be affected by the headphone plugged in.

Got it. Maybe I should build a load box, like the one @L0rdGwyn uses... :thinking:
Keep thinking about this... So, any advantage or disadvantage of using such box as a dummy load on the 2nd headphone jack vs. being a pass-through between the headphone amp and the Motu M4?

This?
Dummy load.jpg


Or this?
Dummy passthrough.jpg
 
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Feb 22, 2021 at 2:20 AM Post #584 of 793

A2029

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Keep thinking about this... So, any advantage or disadvantage of using such box as a dummy load on the 2nd headphone jack vs. being a pass-through between the headphone amp and the Motu M4?

This?
Dummy load.jpg

Or this?
Dummy passthrough.jpg

As long as the 4pin XLR and the 1/4" outputs are the same (i.e. you aren't trying to measure an amplifier that has separate balanced and summed single ended outputs), then either of these will be equivalent. If you plan to measure solid state amps that are inherently balanced but have summed single ended, then go with scenario 2. If just using for single ended tube amps, then you can go with either :)
 
Feb 22, 2021 at 2:53 AM Post #585 of 793
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As long as the 4pin XLR and the 1/4" outputs are the same (i.e. you aren't trying to measure an amplifier that has separate balanced and summed single ended outputs), then either of these will be equivalent. If you plan to measure solid state amps that are inherently balanced but have summed single ended, then go with scenario 2. If just using for single ended tube amps, then you can go with either :)
Thanks Mischa. For the dummy load resistors - would 5W resistors be enough? I know @L0rdGwyn used much more substantial resistors, but then again he plugs it to the speaker taps. Not headphone out...
 

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