[Dreadhead]

Quote:

Originally Posted by amb /img/forum/go_quote.gif It will be a futile exercise trying to measure frequency response with any computer sound card, because both amps will exhibit ruler-flat response, and they extend far below and above that of the sound card itself. The only feasible way to measure this would be with a good function generator and scope (e.g., β22's frequency response is 0Hz - 2.5MHz +0, -3dB).

I figured as much. Thank you for the quick and informative reply.

I tried this with the GS-X in SE mode and actually saw a tiny drop (less 0.05 db or even smaller) in the high frequencies (beyond 18kHz) with the GS-X vs straight out of the headphone port of the DAC1 but there are other things at play that make that a flawed measurement (ie the load impedance, blanced input to the GS-X driving the SS, and using the headphone port). This was all done using RightMark Audio Analyzer. The M-Audio Transit (USB based) is a 24/96 system and was stone flat up to 22 kHz in loop back (can only run 96 as input or output so when not using the DAC1 as source I was limited to 24/44.1). I got the idea from your website actually and It was not an all out assault on knowledge but pretty much playing around

.

I figured it was worth a try but I won't bother. I'm pretty sure I can't hear 2.5 mHz

 

[Computerstud]

Quote:

Originally Posted by Dreadhead /img/forum/go_quote.gif First Impression I have spent about 5 hours listening to both the beta22 and the GS-X after spending some time volume matching the two. After listening to several pieces again and again and switching back and forth between amps with the same headphones when I noticed a particular detail all I can say is right now I can not tell the difference between the two amps. I have tried this with both pairs of headphones of course... Of course this is my first impressions but it is what it is. I will be doing a lot more listening over the next several days but work has been nuts so it may take a while. MORE TO FOLLOW

Did you volume match using a SLM meter or played it by ear?

Unless you have supernatural hearing (some think they do) it's not a reliable method for a fair comparison without a SLM meter. A slight increase in volume or decrease in volume can make a world of difference in this arena referred to as Head-fi.

I'm contemplating going balance so any more impressions are greatly appreciated.

 

[Dreadhead]

Quote:

Originally Posted by Computerstud /img/forum/go_quote.gif Did you volume match using a SLM meter or played it by ear? Unless you have supernatural hearing (some think they do) it's not a reliable method for a fair comparison without a SLM meter. A slight increase in volume or decrease in volume can make a world of difference in this arena referred to as Head-fi. I'm contemplating going balance so any more impressions are greatly appreciated.

I did it by ear which I know is not the most accurate. I considered stopping and picking up a RadioShack SPL Meter but I decided it wasn't worth it to me since I don't buy things to know I'll return them a day later and I'm not aware of many other uses for the SPL meter on the horizon. To volume match I did several back and forth trips varying the stepped attenuators on the beta22 by a single notch when I had the GS-X in the same range. I then went back and forth a couple more times and pretty much convinced myself they were very close. I also switched the channels between ears (a lot easier with balanced connectors) to check to make sure there was little effect on that. Also I do checks once and a while to just make sure the two beta22 channels are in balance and those generally come out spot on when I count detents (I was off by one detent once right at the beginning of listening to the beta22).

I can not say that I have super human hearing but I tried to account for my just human hearing by being careful with my technique. If people can give me a good excuse to have a SPL meter outside this comparison then I'd be interested.

In the end if there is something in particular I'm listening for (particularly fast drum hit, a cymbal, a high note, a recording engineer talking etc...) I generally try at several volume ranges as well. This also limits the effect of any volume mismatches.

Cheers,
Chris

 

[Computerstud]

You have over $3000 worth of AMPs in front of you...I think that's reason enough to put out a few dollars more to eliminate some variables from the experiment.

You can always use the SPL if you decide to move to a speaker set-up, home theater, change source, or anything that is sound related. If this is not your final destination in audio gear, an SPL meter will serve you well in audiophile land.

 

[amb]

Rather than a SLM, you can set the volume of the amps to approximately where you would normally listen at. Then, unplug the headphones, play a sine wave tone and measure the output voltage (using your DMM in AC Volts range) across pins 2 and 3 of the output XLR jacks. Fine-tune the volume knobs so that you get the same voltage reading on the two amps. Test tone sound files can be found here. The 1000Hz sine wave file would be a good choice to use.

 

[Dreadhead]

Quote:

Originally Posted by Computerstud /img/forum/go_quote.gif You have over $3000 worth of AMPs in front of you...I think that's reason enough to put out a few dollars more to eliminate some variables from the experiment. You can always use the SPL if you decide to move to a speaker set-up, home theater, change source, or anything that is sound related. If this is not your final destination in audio gear, an SPL meter will serve you well in audiophile land.

Yeah I know it's lame to nitpick over $65 but hey.... It's likely I'll use my amps nearly every day for 5 years (or more). I'll that spl meter once or twice and put it away in my bloody speaker boxes. It just seems wasteful to me. I'm the kind of guy who drives his wife's civic to work instead of my Subaru Legacy GT just on the priciple of not wasting resources and money on things that don't matter (I can assure you in traffic the car your are sitting in just doesn't matter

).

I guess I may stop at my local Radioshack on the way home. I can also use it to equalize my stereo if I feel like it. Hey and I can in the Subaru as well so there we go 3 uses.

Maybe I can also use it next time my wife claims I'm yelling: "it's not your volume it's your tone...".

Still not a definite but I'll think about it.

 

[Dreadhead]

Quote:

Originally Posted by amb /img/forum/go_quote.gif Rather than a SLM, you can set the volume of the amps to approximately where you would normally listen at. Then, unplug the headphones, play a sine wave tone and measure the output voltage (using your DMM in AC Volts range) across pins 2 and 3 of the output XLR jacks. Fine-tune the volume knobs so that you get the same voltage reading on the two amps. Test tone sound files can be found here. The 1000Hz sine wave file would be a good choice to use.

NOW that's a great idea. I don't have a DMM but an old analog one but I'll give it a try with that one first but if I have problems I'll get a DMM. Now that's something I'll buy, a new DMM is useful beyond this.

Thanks again for the great idea. I have tone generation software already.

Cheers,
Chris

 

[Dreadhead]

Quote:

Originally Posted by Dreadhead /img/forum/go_quote.gif NOW that's a great idea. I don't have a DMM but an old analog one but I'll give it a try with that one first but if I have problems I'll get a DMM. Now that's something I'll buy, a new DMM is useful beyond this. Thanks again for the great idea. I have tone generation software already. Cheers, Chris

Well my analog multimeter will not do the trick. The smallest range it allows is 10 volts AC and I need to have the GS-X to max to even get a volt and a half. It's not in the listenable range of volumes. I guess either it's busted (it measures AC at the wall just fine) or all this talk about needing 10 pp seems to be overstated. I'll stop and get a DMM tomorrow I guess.

Cheers,
Chris

 

[naamanf]

Try a 60hz tone.

 

[vvs_75]

Quote:

Originally Posted by Dreadhead /img/forum/go_quote.gif Well my analog multimeter will not do the trick. The smallest range it allows is 10 volts AC and I need to have the GS-X to max to even get a volt and a half. It's not in the listenable range of volumes. I guess either it's busted (it measures AC at the wall just fine) or all this talk about needing 10 pp seems to be overstated. I'll stop and get a DMM tomorrow I guess. Cheers, Chris

I have DMM if you willing to wait.

 

[Dreadhead]

Quote:

Originally Posted by naamanf /img/forum/go_quote.gif Try a 60hz tone.

I did that before I posted but no luck. I also cranked the volume and tested the reading vs frequency and it didn't seem to change at all between 60hz and 1000 Hz. Very odd.

 

[amb]

Quote:

Originally Posted by Dreadhead /img/forum/go_quote.gif Well my analog multimeter will not do the trick. The smallest range it allows is 10 volts AC and I need to have the GS-X to max to even get a volt and a half. It's not in the listenable range of volumes. I guess either it's busted (it measures AC at the wall just fine) or all this talk about needing 10 pp seems to be overstated. I'll stop and get a DMM tomorrow I guess.

I found that for casual listening levels, I would set the volume control such that a sine wave output would yield slightly at or below 1V rms (2.828Vpp) on the HD600. HD650 should be similar. Your DMM will measure the RMS value.

However music is not sine wave, so it's not unreasonable to want to have a healthy amount of voltage headroom for transient peaks, maybe even as much as 20dB (that's 10x the voltage). So that makes 28Vpp. The balanced β22 could deliver over 80Vpp which is clearly much more than necessary for the HD650, but try some of the 600 ohm AKGs or Beyers and the voltage swing requirement goes up quite a bit...

 

[Dreadhead]

Quote:

Originally Posted by amb /img/forum/go_quote.gif I found that for casual listening levels, I would set the volume control such that a sine wave output would yield slightly at or below 1V rms (2.828Vpp) on the HD600. HD650 should be similar. Your DMM will measure the RMS value. However music is not sine wave, so it's not unreasonable to want to have a healthy amount of voltage headroom for transient peaks, maybe even as much as 20dB (that's 10x the voltage). So that makes 28Vpp. The balanced β22 could deliver over 80Vpp which is clearly much more than necessary for the HD650, but try some of the 600 ohm AKGs or Beyers and the voltage swing requirement goes up quite a bit...

Thanks for the explanation. I'd forgotten that the multimeter took the RMS but that make sense.

I'm thinking that it may be an issue with my meter because when I use it and set the Vrms on the amp to .8 volts I am more than 1/4 a turn past what I consider too loud on the GS-X. I haven't even plugged in phones at that setting because I know my tinnitus would be back with a vengeance.

I'll make up my mind between a new multimeter or a SPL meter tomorrow. I'm leaning towards a DMM but the Radioshack ones look fairly crappy and expensive.

 

[Dreadhead]

I did a longer listening session yesterday listening to a whole song several times on each amp and then several songs on each amp and I was just floored by the sound quality of both of these amps all over again. (I know it's gross but you can hear James Blunt's tongue slapping around in his mouth and his lips smacking etc as well as every little nuance of his voice and the reflections of it off the walls. Both of these amps are truly amazing at their ability to resolve the smallest detail but they do not force them out front either.

I've got a natural knack (for a sighted person, most blind people's hearing is absolutely amazing) for noticing the smallest noise so that's why I mention such things.

To be honest I still have not heard any difference between the two but I will do a more careful volume matching soon (I have house guests today so tonight is not likely). For these impressions I used a 1000Hz test tone and went back and forth 3 times matching by ear. I'd say the volume is very close but I don't think it will end up exactly the same because of the fact both amps are using stepped attenuators which makes the job easier and harder at the same time. We'll see what a exact (instrument measured) volume match does.

Right now this showdown seems to have two winners and no losers which is a good thing in my book. This weekend Vlad should be coming over with his beta22 (actually a 4 sigma22 speaker setup with premium parts) and edition 9's so it should be interesting to see if anything turns up then. I guess once I make up my mind at to what I'm hearing I'll do a full summary post.

Cheers,
Chris

 

[Dreadhead]

Well guys and gals I ended up buying the SPL gauge and checking my volume match and it's as close as I can get it with my stepped attenuators. They both read 67 db. I guess I do have superhuman ears