[insyte]

Quote:

Originally Posted by oneplustwo /img/forum/go_quote.gif I'm in the process of building both a 4 and 2 channel so I'll give you my impressions when I'm done. Might be a while as I have a couple other projects in the works as well, but I will get it done as I've been looking for a definitive answer (at least to my own ears) to this question as well.

Looking forward to your impressions

 

[keyid]

interested as well

 

[amb]

Quote:

Originally Posted by fishski13 /img/forum/go_quote.gif does Ti have any measurements of passive ground vs. active ground?

I have made measurements in the past but I can't find the results specifically for the β22 now. However you could look at the results of my M³ (which, of course, is 3-channel active ground) and my β18 amp (modified SDS Labs amp -- basically a 2-channel passive-ground M³), both loaded with 33 ohms.

One of the most striking difference in RMAA is 3-channel active ground's lower stereo crosstalk. This makes sense because the headphone load's return current doesn't contaminate signal ground. If the signal ground, which is the zero-volt reference for both channels, is allowed to "wiggle" as a result of return current from one channel, that would result in an effective leakage of signal into the opposite channel.

M³:

β18:

But reduced stereo crosstalk isn't the only benefit. Real headphone loads are reactive rather than purely resistive, which means that the return "ground" current can become phase shifted compared to the swinging voltage. If that current is allowed to pollute signal ground (which might be the case in a passive-ground 2-channel setup), it would induce a voltage wiggle that is also phase shifted from the main signal voltage, when the two are summed together you get a form of dynamic distortion. This phenomenon becomes worse with low-Z headphone loads due to the increased current.

 

[smeggy]

While technically better, do you think it would this be audible under normal circumstances at the levels measured? I doubt I could detect it myself, but most have younger ears than mine.

 

[fishski13]

thanks Ti.

 

[rshuck]

Quote:

Originally Posted by smeggy /img/forum/go_quote.gif While technically better, do you think it would this be audible under normal circumstances at the levels measured? I doubt I could detect it myself, but most have younger ears than mine.

I wouldn't assume that... I took a hearing test, and the balance between my ears is terrible. I can hear 22k with my left... but only 14k with my right.

Just a guess here, but at normal listening levels, I would make the assumption that it would not be audible.

 

[rds]

Any comments on the output power using a single s22 with 100 VA transformer to a 2 channel B22 to 6 ohm speakers?

 

[ting.mike]

Quote:

Originally Posted by oneplustwo /img/forum/go_quote.gif I'm in the process of building both a 4 and 2 channel so I'll give you my impressions when I'm done. Might be a while as I have a couple other projects in the works as well, but I will get it done as I've been looking for a definitive answer (at least to my own ears) to this question as well.

Thanks! please do!

Quote:

Originally Posted by amb /img/forum/go_quote.gif I have made measurements in the past but I can't find the results specifically for the β22 now. However you could look at the results of my M³ (which, of course, is 3-channel active ground) and my β18 amp (modified SDS Labs amp -- basically a 2-channel passive-ground M³), both loaded with 33 ohms. One of the most striking difference in RMAA is 3-channel active ground's lower stereo crosstalk. This makes sense because the headphone load's return current doesn't contaminate signal ground. If the signal ground, which is the zero-volt reference for both channels, is allowed to "wiggle" as a result of return current from one channel, that would result in an effective leakage of signal into the opposite channel. M³: β18: But reduced stereo crosstalk isn't the only benefit. Real headphone loads are reactive rather than purely resistive, which means that the return "ground" current can become phase shifted compared to the swinging voltage. If that current is allowed to pollute signal ground (which might be the case in a passive-ground 2-channel setup), it would induce a voltage wiggle that is also phase shifted from the main signal voltage, when the two are summed together you get a form of dynamic distortion. This phenomenon becomes worse with low-Z headphone loads due to the increased current.

Thanks, Ti!

Quote:

Originally Posted by smeggy /img/forum/go_quote.gif While technically better, do you think it would this be audible under normal circumstances at the levels measured? I doubt I could detect it myself, but most have younger ears than mine.

Ditto. Someone should really make a comparison thread.

 

[indikator]

why not compared it yourself?
it is modular right? you can build it 4 channel first, then compared it to 3 channel one (hanhan's?), any change later to add aditional board will be easy to make

 

[ting.mike]

Quote:

Originally Posted by amb /img/forum/go_quote.gif I have made measurements in the past but I can't find the results specifically for the β22 now. However you could look at the results of my M³ (which, of course, is 3-channel active ground) and my β18 amp (modified SDS Labs amp -- basically a 2-channel passive-ground M³), both loaded with 33 ohms. One of the most striking difference in RMAA is 3-channel active ground's lower stereo crosstalk. This makes sense because the headphone load's return current doesn't contaminate signal ground. If the signal ground, which is the zero-volt reference for both channels, is allowed to "wiggle" as a result of return current from one channel, that would result in an effective leakage of signal into the opposite channel. M³: β18: But reduced stereo crosstalk isn't the only benefit. Real headphone loads are reactive rather than purely resistive, which means that the return "ground" current can become phase shifted compared to the swinging voltage. If that current is allowed to pollute signal ground (which might be the case in a passive-ground 2-channel setup), it would induce a voltage wiggle that is also phase shifted from the main signal voltage, when the two are summed together you get a form of dynamic distortion. This phenomenon becomes worse with low-Z headphone loads due to the increased current.

Since my 3 boards build is finished and running (minus a case for now), I did a comparison b/w 2 boards and 3 boards set up, and it is very very evident, that the 3 boards give a much larger soundstage. I initially didn't think the differences would be that big, but turns out it's quite night and day in terms of soundstage. Like having a different amp.

 

[linuxworks]

how did you compare the 2board and 3 board versions?

I question the comment about it being night and day. knowing the numbers, it seems unlikely that what you've heard is JUST the 3rd channel in effect.

however! if you have before/after graphs, I'd love to see them

 

[linuxworks]

Quote:

Originally Posted by indikator /img/forum/go_quote.gif why not compared it yourself? it is modular right? you can build it 4 channel first, then compared it to 3 channel one (hanhan's?), any change later to add aditional board will be easy to make

easier than that.

build a 3channel version and simply switch the ground (on the phones jack) to be power supply ground (for 2ch) or 3rd channel amp module output if 3ch mode. just 1 wire to be switched.

 

[ting.mike]

Quote:

Originally Posted by linuxworks /img/forum/go_quote.gif easier than that. build a 3channel version and simply switch the ground (on the phones jack) to be power supply ground (for 2ch) or 3rd channel amp module output if 3ch mode. just 1 wire to be switched.

that's exactly how I did the comparison.

this is still with cheap parts and potentiometers, I haven't even mounted the ALPS blue velvet that came with the kit. The difference is so evident. Oh, and the source is only an Ipod too... can't wait when I properly solder a good RCA to connect to my CEC CDP.

I'm just sharing my find, fine by me if you don't buy it.

But now I'm seriously thinking that the 4 Boards idea needs to be upgraded to 5 boards, or scrap it altogether.

 

[linuxworks]

I don't mean offense, but there isn't a good technical reason for why things would sound SO different. I do think other stuff is going on. you may be hearing some diff but it should be a 'test gear' diff and not an ear diff.

oh well.

 

[DoYouRight]

Hm, for low ohm cans is the active ground more or less necessary?