[trains are bad]

I have a Total Bithead, one of the old ones without the gain switch. I also have a MicroDAC, both purchased used several years ago.

I just now tried to run the Total Bithead using the analog output from the microDAC. The red clipping light blinks often even with the volume control barely cracked.

Now I know the microDAC has a really healthy output level based on the relative volume level I get with it compared to other sources. Could it be the Total Bithead is not compatible with the high input levels the microDAC puts out?

To find out I played a 500Hz tone at -0dB and the multimeter showed 150mV out of the Total Bithead. The RCAs from my Technics surround processor with no attenuation (volume at -0) are 123mV. So this isn't a large difference. Also the Total Bithead running off the analog output from the Technics does not clip! I can turn the volume slider up quite high before getting any blinkage. Whereas the MicroDAC causes the blinkage with the volume barely cracked, at much much lower volumes.


I'm quite confused.

 

[tpc41]

are the batteries in the bithead fully charges? it tends to clip a lot when they are low

 

[trains are bad]

I but brand new ones in. But still, that doesn't explain why the microDAC clips it, but my other dac doesn't. It's actually very weird.

 

[Herandu]

It's a long shot, but I suspect that the DAC is oscillating outside the audio spectrum. The only way that I know of to check that is by using a scope to look at the analog output waveform.
If it is oscillating, don't connect it to your amp for playing through your speakers!!! It would take out your tweeters.

 

[Chri5peed]

Vairy odd, it sound like a broeked MicroDAC.


...btw, trains is good. Especially the song of that name by Porcupine Tree.

 

[lexnasa]

The output of the MicroDAC is really hot. I've just switched to the 2007 Micro Amp with optional DAC... (I don't use the amp, just the DAC) a big improvement all round, plus variable line out... hurrah!

 

[trains are bad]

If the reason the amp clips with with microdac and not my other dac is due to the microdac's line out being higher ( which it's not that much higher-15%or so) then I would think that it would just cause the amp to start clipping at slightly lower volume settings, since the input would be slightly higher. But it doesn't do that, it clips at any volume level besides 0, I mean as soon as you turn the volume up from zero, it starts blinking.

And if the amp is oscillating, then why does it do it with the microdac and not with my other sources? As far as I can tell, the microdac is functional. It sounds fine plugged into my tube amp, and it sounded fine when it was hooked up to my speakers.

edit: someone suggested that the DAC is oscillating. In that case, it could sound fine when hooked up to my other amps, because the clipping could be below audible, but still enough to blink the Bithead's light.

 

[Golden Monkey]

My Total Airhead clipped just like that when I connected it to my line out on my DVD player, but not when I connected it to an older Denon CD player I have. I noticed that the VD has significantly higher output levels in comparison, so your DAC may just be to "hot".

 

[Herandu]

Quote:

Originally Posted by trains are bad /img/forum/go_quote.gif edit: someone suggested that the DAC is oscillating. In that case, it could sound fine when hooked up to my other amps, because the clipping could be below audible, but still enough to blink the Bithead's light.

I suggested that, but what would I know about the ins and outs of DACs other than that I have fixed them for a living and modded a couple as well. But seriously though, you need to find someone with a scope to check out the output signal. You can do it with some of the digital multimeters by putting the meter onto the AC 2 Volts setting, stick the metal part of black meter lead on the outside of the RCA socket, and the metal part of the red lead on the inside of the analog out RCA socket. Now turn the volume up and see if the meter starts indicating the presence of a AC voltage that is at least 1V or more with even just a slight turn of the DAC volume control. If it does, then the DAC needs some repair atention.

 

[Dominat0r]

might want to post this in the headroom forum so Jorge or Tyll can answer.

 

[trains are bad]

I didn't know there was a headroom forum. If a mod would like to move it, that would be fine.

I have access to scopes, but the DAC doesn't have a volume control.

 

[Golden Monkey]

No, HL means on the HeadRoom site, but i couldn't find any forums. Here's the link to the contact info though...give them a call, I'm sure they can address your concerns: Products - HeadRoom - Right Between Your Ears

 

[Dominat0r]

HeadRoom Premier Sponsor Forum - Head-Fi: Covering Headphones, Earphones and Portable Audio

 

[Chri5peed]

PM Tyll, he is a nice chap and will answer a headroom query.

 

[trains are bad]

I contacted Headroom, and they said it was clipping because the output level of the microDAC is so high. I made a voltage attenuator last night and it's working fine now.