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Roll Call: Who's building, built, or thinking of building a beta22?
Apr 23, 2012 at 1:40 PM Post #2,881 of 3,218
I still can't see how "3-channel" ever gained popularity over dual mono - there's simply no comparison - "3-channel" is wrong on nearly all counts that are claimed as tech advantages
 
Apr 23, 2012 at 3:44 PM Post #2,882 of 3,218
jcx - have you substantiated your convictions from any formal testing, both objective and subjective?
 
Otherwise...
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Apr 23, 2012 at 11:01 PM Post #2,884 of 3,218
from the popcorn icon I doubt you're truly interested in following the intellectual argument - if so I suggest forum search
 
Ti had to concede my TRS common gnd crosstalk argument when he finally did the measurement properly - on the headphone side of the connector - the milliOhms of common gnd jack/plug contact resistance totally obscures his published crosstalk numbers (measured on the amp board)
 
NwAvguy/RocketScientist has measured the flaws I point out in arguing against "3-channel" gnd - admittedly with "lessor" amps than the B22
 
if you are serious about "gnd contamination" then 4-pin "balanced" headphone cable termination is the only choice
 
add dual mono PS and the only common point is the source signal gnd connection
 
keeping TRS with its compromises you can replace the 3rd board with a few $ of Cu roof flashing for a uOhm technical gnd - and the Cu won't have distortion (which doesn't cancel - another false "3-channel" claim)
 
 
 
Apr 24, 2012 at 7:33 AM Post #2,886 of 3,218
Non-technical, subjective opinion from having compared my 2-ch (not dual-mono) vs. 4-chl/balanced β22 builds (+ comparing the 2-ch to 3-ch in meet settings) - think most would be hard-pressed to hear a difference amongst the topologies.  Especially when not doing proper A/B/Xing. 
 
For my 2-ch vs 4-ch comparison I feed them w/same source, used a 1/4" -> XLR adapter on the 2-ch so was able to almost instantly switch the same headphones between them.  Won't say I didn't perceive the slightest difference but not confident I could pick each out reliably even w/proper A/B/Xing.  YMMV and others w/better ears, the best source + source material could fare differently.
 
With the cost/complexities involved IMO build 2-ch for unbalanced, 4-ch for balanced.
 
Apr 24, 2012 at 9:45 AM Post #2,887 of 3,218
I quite agree that my expectation is the the differences in good builds are likely inaudible with B22 - so "3-channel" is a waste of time and resources
 
and most of the technical claims justifying "3-channel" simply wrong on engineering principles
 
 
the PSRR (power supply rejection ratio - how much of a change in power supply V show up in the amp output) argument could be partially true, other system noises are worse with "3-channel" - you are adding a whole amp between signal gnd and your headphone's gnd - in "3-channel" the "output gnd" amp has added noise, distortion in series with your headphones
 
the B22 circuit uses a number of design techniques to give it unusually high PSRR, combined with half decent regulated supplies there is no reason to think PSRR performance needs improving
 
Apr 24, 2012 at 10:07 AM Post #2,888 of 3,218
 
Quote:
jcx said:
from the popcorn icon I doubt you're truly interested in following the intellectual argument - if so I suggest forum search
 
Ti had to concede my TRS common gnd crosstalk argument when he finally did the measurement properly - on the headphone side of the connector - the milliOhms of common gnd jack/plug contact resistance totally obscures his published crosstalk numbers (measured on the amp board)
 
NwAvguy/RocketScientist has measured the flaws I point out in arguing against "3-channel" gnd - admittedly with "lessor" amps than the B22
 
if you are serious about "gnd contamination" then 4-pin "balanced" headphone cable termination is the only choice
 
add dual mono PS and the only common point is the source signal gnd connection
 
keeping TRS with its compromises you can replace the 3rd board with a few $ of Cu roof flashing for a uOhm technical gnd - and the Cu won't have distortion (which doesn't cancel - another false "3-channel" claim)
 
 
Click to expand...

 

I apologize for my sarcasm, but I don't follow this forum regularly, and when I see a statement like yours, with no proof offered, I tend to be skeptical. I'll search the forum for your posts so I can further understand the technical side.
 
I have no intention of going to a balanced system at this time, so I may well just do a two-board version. I like your suggestion for replacing the 3rd board with copper - I happen to have a slab of .09" thick copper, about the size of the amp boards. I'll just slap that in the case along with the amp boards.
 
Apr 24, 2012 at 10:39 AM Post #2,889 of 3,218
Quote:
beerguy0 said:
  <snip> I may well just do a two-board version. I like your suggestion for replacing the 3rd board with copper - I happen to have a slab of .09" thick copper, about the size of the amp boards. I'll just slap that in the case along with the amp boards.
Click to expand...

 
Now maybe someone can enlighten me how a slab of copper a few inches long for ground would make much difference given the headphone cable's "ground" lead gauge & length (and proximity to L&R hot leads).  Would think using heavier gauge ground wire (e.g. 18 -> 14) than the PS's +/- and L&R channel wire should suffice, but I guess everything is some sort of compromise:)
 
Apr 24, 2012 at 1:04 PM Post #2,890 of 3,218
 
Quote:
cfcubed said:
 
Now maybe someone can enlighten me how a slab of copper a few inches long for ground would make much difference given the headphone cable's "ground" lead gauge & length (and proximity to L&R hot leads).  Would think using heavier gauge ground wire (e.g. 18 -> 14) than the PS's +/- and L&R channel wire should suffice, but I guess everything is some sort of compromise:)
Click to expand...

 

If I understand jcx's theory, the idea is to have a low impedance ground (low capacitance, low inductance, low resistance). Wire has inductance, capacitance, and resistance, while a sheet of copper has less of all three.
 
May 31, 2012 at 1:00 PM Post #2,893 of 3,218
I am starting mine next week. It will be a fully balanced build to go with the Buffalo 3 that I am working on now. Still undecided on the attenuator though. It will either be a Goldpoint, DACT, Khozmo, or δ1. The plan is to use Plitron transformers, PRP resistors, and Nichicon FG caps. Hopefully it will all come together in the next two months.
 
Jun 2, 2012 at 7:02 PM Post #2,894 of 3,218
I am going to start a fairly minimal Beta 22 build soon.  I am having trouble finding enclosures that are not way too big for a 2 channel build.  What are some enclosure options for a 2 channel build?  I will be using another of the same enclosure for the Sigma 22 if it is the right size.  Does anyone have any suggestions?  I also have no idea how people get their front/rear panels machined.  Do people just have really good skills with front panel express?
 
Jun 2, 2012 at 7:34 PM Post #2,895 of 3,218
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