Zähl HM1 - Reference Headphone Amplifier
May 26, 2023 at 8:09 PM Post #916 of 1,480
anyone using the HM1 as a preamp into a power amp? any feedback on performance as opposed to going straight out of the HM1? eg with Abyss/Susvara.
 
May 31, 2023 at 12:33 AM Post #917 of 1,480
Has anyone here used the HM-1's pass through RCA sockets? I have tried it now with two different amps down-chain and in both cases had significant issues with distortion that I can only assume is due to impedance issues when connecting the HM-1 plus other amps to the same output of the DAC. (Interestingly, if I use a simple RCA splitter to connect other amps it's fine - the problem only arises when the HM-1 is in the circuit using the pass-through or RCA splitters)
 
May 31, 2023 at 3:15 AM Post #918 of 1,480
Has anyone here used the HM-1's pass through RCA sockets? I have tried it now with two different amps down-chain and in both cases had significant issues with distortion that I can only assume is due to impedance issues when connecting the HM-1 plus other amps to the same output of the DAC. (Interestingly, if I use a simple RCA splitter to connect other amps it's fine - the problem only arises when the HM-1 is in the circuit using the pass-through or RCA splitters)
What have you got the HM1's gain set to and what is the output voltage from the DAC?

The HM1 has an input voltage limit of 10.6V in 0dB gain and 2V in +15dB gain.
 
May 31, 2023 at 4:55 AM Post #919 of 1,480
What have you got the HM1's gain set to and what is the output voltage from the DAC?

The HM1 has an input voltage limit of 10.6V in 0dB gain and 2V in +15dB gain.

Running TT2 in DAC mode so 2V via RCA IIRC. No issues with the DAC connected directly to the HM-1 only and not using pass through. The distortion occurs on both amps once the HM-1 is in the chain, but either amp on its own is fine (i.e. with no splitting or pass through of the cables)

Gain on the HM-1 is 0dB
 
May 31, 2023 at 4:57 AM Post #920 of 1,480
Running TT2 in DAC mode so 2V via RCA IIRC. No issues with the DAC connected directly to the HM-1 only and not using pass through. The distortion occurs on both amps once the HM-1 is in the chain, but either amp on its own is fine (i.e. with no splitting or pass through of the cables)

Gain on the HM-1 is 0dB
Just to confirm, if you connect to the HM1, and listen through the headphone out, it's fine, but only once you connect something to the A-Thru (no other settings changed) the HM1 itself will also start to distort?

(also does the issue go away if you set the front headphone/preamp toggle to the middle setting?)
 
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May 31, 2023 at 6:19 AM Post #921 of 1,480
Just to confirm, if you connect to the HM1, and listen through the headphone out, it's fine, but only once you connect something to the A-Thru (no other settings changed) the HM1 itself will also start to distort?

(also does the issue go away if you set the front headphone/preamp toggle to the middle setting?)

Part 1 is correct. I'll have to check the pre-amp toggle
 
May 31, 2023 at 7:43 AM Post #922 of 1,480
Part 1 is correct. I'll have to check the pre-amp toggle
If it's only happening when something is connected but you're not actually changing any settings that implies some sort of severe impedance issue, is the device you're connecting to it turned on?

But also yeah make sure the preamp section is turned on. I think that has to be enabled for the A-Thru to work.
You can set it to preamp only, headphone only, or both
 
May 31, 2023 at 7:03 PM Post #923 of 1,480
I removed the HM-1 entirely from my desk last night for some B-roll footage and have re-inserted it this morning with no such problems as previously. I can only assume that I had a loose interconnect or poor contact somewhere that was enough to cause problems when the input impedance reduced from having two amps connected. Same track, same amp, same headphones and no issues today.

It is a shame that the pass through doesn't work when the HM-1 is switched off though :frowning2: Also, for those interested, the output toggle switch (headphones, pre-amp, both) makes no difference to the pass through.
 
May 31, 2023 at 7:35 PM Post #924 of 1,480
I removed the HM-1 entirely from my desk last night for some B-roll footage and have re-inserted it this morning with no such problems as previously. I can only assume that I had a loose interconnect or poor contact somewhere that was enough to cause problems when the input impedance reduced from having two amps connected. Same track, same amp, same headphones and no issues today.

It is a shame that the pass through doesn't work when the HM-1 is switched off though :frowning2: Also, for those interested, the output toggle switch (headphones, pre-amp, both) makes no difference to the pass through.

Super wierd. Glad it fixed it's self at least I guess
 
Jun 16, 2023 at 10:17 PM Post #928 of 1,480


What's up with the use of low quality, low reliability Jamicon caps in an 8K USD amp, instead of going with Panasonic or Nichicon at least?
 
Jun 16, 2023 at 11:30 PM Post #929 of 1,480
anyone using the HM1 as a preamp into a power amp? any feedback on performance as opposed to going straight out of the HM1? eg with Abyss/Susvara.

When you use it as a pre-amp into a tube amp, it's magical, especially when you adjust the soundstage knob to +1. I currently use my HM1 as a pre-amp into a Nautilus. Sounds fantastic with 1266, Stealth and D8KP LE. Haven't tried Susvara yet.
 

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