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The Beta 22 Thread - Page 5

post #61 of 86
2 channel is single ended passive ground
3 channel is single ended active ground
4 channel is balanced
I don't know if someone has made a 5 channel one
6 channel is balanced with two active ground single ended amps

the price of my parts from glass jar audio for my 6 channel beta22 and 2 120VA S22's was ~$750 not including pot or case
post #62 of 86

{HOPING TO REVIVE THIS THREAD....}

 

Quote:

Originally Posted by m11a1 View Post

Hey guys, I'm new to this stuff, is the Beta 22 a DIY only amp?

It is not available assembled - like from a dealer or retail store- it is designed to be DIY. HOWEVER, there are "pro builders" who will build one for you upon request ( and payment)

 

Also there are usually one or two used ones for sale here in the Head-Fi FOR SALE section.

 

It's not a hard kit to build, although there are a lot of parts to solder in, so it takes time to make.  Then, too, you have to house it in some kind of chassis. Most folks get a chassis from Par-Metal, and it requires some metalworking skill to drill the holes needed to mount the circuit boards, the power transformer, the volume control and so on.  So really it's not hard but takes some skill and patience.

 

I've built one a while back and recently I ended up with all the parts to build a second one - how that happened is a long story- and so I'm building it right now, decided to make the chassis pretty, with a front panel milled from  aluminum billet and so on, as well as using a fancy stepped ladder-type attenuator and other upgraded parts. I will end up selling one or the other of my Beta 22's, either the pretty new one or the plain one I built two years ago.  I'll post pictures of the new one once it's done.

 

Here's the front panel "hot off the CNC mill" - rather raw, still quite a few finishing steps left.  The photo doesn't really give you an idea here of it's three-dimensionality- it's  quite chunky, 3/4" thick with some sculptural aspects to it.

 


Edited by milosz - 7/1/13 at 5:20am
post #63 of 86
Quote:
Originally Posted by m11a1 View Post

Sorry to keep asking, but is there any sound quality difference between the 2 channel and the 3 channel with one being a ground?

And also, does 2 channel mean that it's not balanced and 4 channels means that it's balanced?

I believe "3-channel" is technically wrong - doesn't do the right thing technically on several of the counts that proponents put forth - simple engineering fact

 

of course in audio land the response is "but it soundz different" - which to my mind is further evidence of incorrect implementation - the differences should be too small to hear by comparing engineering numbers with psychoacoustic thresholds

and I have yet to see that "soundz different" applies when necessary psychoacoustic/perceptual science established controls are used when listening

 

long before the faddish enthusiasm for "3-channel" - "dual mono" was the considered "the ultimate" - 2 isolated power supplies - the 2 channels ideally don't connect anywhere but the input signal gnd - for headphones this requires "balanced" 4 wire cable termination instead of TRS

Dual mono, 4 wire output does effectively address those concerns the "3-channel" enthusiasts cite but technically fail to improve

 

for a 2-channel, single ended input amp  I would spend the money on a 2nd power supply, changing my headphone connector to 4-wire instead of wasting the money on "3-channel" 3rd amp board

 

 

but to keep the differences in perspective - if you gave me any competently built B22 of any configuration I would just plug in and listen - despite having the tools, disliking the technical/conceptual errors of "3-channel"

I am serious about believing the differences couldn't be heard in properly controlled listening comparisons


Edited by jcx - 7/1/13 at 10:35am
post #64 of 86
Quote:
Originally Posted by jcx View Post

I believe "3-channel" is technically wrong - doesn't do the right thing technically on several of the counts that proponents put forth - simple engineering fact

 

 

 

but to keep the differences in perspective - if you gave me any competently built B22 of any configuration I would just plug in and listen - despite having the tools, disliking the technical/conceptual errors of "3-channel"

I am serious about believing the differences couldn't be heard in properly controlled listening comparisons

 

That may be true, but building a "three channel"  (i.e., "active ground") version will likely SELL more quickly if you decide to part with it, and that's the kind of sound many prefer-  the sound of MONEY coming in.

 

I think it can actually be shown that using a "three channel" (active ground) or four channel (fully balanced) version actually increases distortion - using more than one amp section per headphone channel results in the distortion from the gain stages being ADDED together, so a balanced (4 channel) Beta 22 would have TWICE the distortion and noise of a single-ended two channel version.  Of course, the distortion in this amp is so vanishingly low that even doubled it is not audible.  Still, I tend to agree that all the complexity of 3-  4-  and even 6-channel builds do not result in measurably or audibly better sound- with one possible exception: damping factor is higher in the "multi channel" versions, and this might be audible.

 

I don't think a dual power supply version would sound any different.  The sigma power supply is so stiff, so low in impedance and so well regulated that current demands from a Beta 22 amp board driving headphones is unlikely to produce any droop on the rails, no matter how short a duration;  and the Beta 22 amps themselves have such high common-mode rejection that even if something were present on the rails it would not make it to the output.

 

Now, if you were using a Beta 22 for a speaker amp - then maybe you  might need two Omega power supplies; bigger heatsinks on the Beta 22 output devices too.

post #65 of 86

while you can do almost as good with just 4-pin "balanced" headphone cable connector and 2 channel, single supply - full "dual mono" completely separates R,L channels - there is no "cross contamination" from shared load ground/return because nothing is shared

 

and as near as possible when comparing engineering estimates, psychoacoustic knowledge of human hearing - the B22 is so good on all of noise, distortion, PSRR that any competent build shouldn't have audible differences from any other in level matched blind listening comparisons

 

it is likely power supply details like pri-secondary parasitic capacitance in the transformer(s), line entry filters, details of PS, gnd wiring and all input/output connector gnding wiring details, even volume control choices are more important than amp channel count

post #66 of 86
Quote:
Originally Posted by jcx View Post

while you can do almost as good with just 4-pin "balanced" headphone cable connector and 2 channel, single supply - full "dual mono" completely separates R,L channels - there is no "cross contamination" from shared load ground/return because nothing is shared

 

and as near as possible when comparing engineering estimates, psychoacoustic knowledge of human hearing - the B22 is so good on all of noise, distortion, PSRR that any competent build shouldn't have audible differences from any other in level matched blind listening comparisons

 

it is likely power supply details like pri-secondary parasitic capacitance in the transformer(s), line entry filters, details of PS, gnd wiring and all input/output connector gnding wiring details, even volume control choices are more important than amp channel count

Certain aspects of the build can be quite important in reducing noise.  It can be quite tricky to create a "one box" Beta 22 that is free of hum, the amp boards of the Beta 22 seem unusually susceptible to inductively-coupled 60 Hz hum from the power transformer. Mounting the transformer inside a steel can or box along with careful layout can eliminate this.

 

Another good practice is to put the volume pot or switched attenuator in the back of the chassis, right next to the input jacks, and use a shaft extension to couple it to the volume knob on the front.  This keeps the input signal wiring as short as possible.


Edited by milosz - 7/5/13 at 1:46am
post #67 of 86
looking pretty milosz. reminds me of Jeff Rowland. since all of my customers have nicer chassis than my own, i decided to splurge on a FPE for my own B22 for my b-day and should have it next week.

for a single chassis build, i would want a shielded/encapsulated TX, GL-breaker, and shielded wire on the high impedance signal runs. this is how mine is configured.
Edited by fishski13 - 7/5/13 at 6:19pm
post #68 of 86
Quote:
Originally Posted by fishski13 View Post

looking pretty milosz. reminds me of Jeff Rowland. since all of my customers have nicer chassis than my own, i decided to splurge on a FPE for my own B22 for my b-day and should have it next week.

for a single chassis build, i would want a shielded/encapsulated TX, GL-breaker, and shielded wire on the high impedance signal runs. this is how mine is configured.

Yes the GL breaker is important.  I have some non-inductive 10 watt 10 ohm resistors to use for this.  

 

That Rowland look is just an artifact of the milling machine, it's not the final finish.  Those milling marks don't look all that great in person; they'll be buffed out and then the top part of the panel will be bead-blasted to give a "frosted" look with a slight texture.  The bottom "stripe" -  which includes the Beta 22 logo -  will be mirror polished.  The panel is 3/4" thick, very chunky.


Edited by milosz - 7/8/13 at 3:58am
post #69 of 86

Glad to see this thread back up and running.  I should be getting my B22 re cased and adding a few goodies to it as well. 

 

Are there any advantages a RK50 pot has over a Goldpoint SA?

post #70 of 86

The RK50 looks prettier, and probably has a longer MTBF. And from Alps point of view, the RK50 certainly offers more profit....  :cool:

 

The Goldpoint SA might sound better- some people claim they can hear a difference between the contact-on-conductive-plastic of a pot and the more direct contact of the switch in an attenuator.

 

-------------------------------------------------------------------------------------

 

Recently completed Beta 22 build

 

      


Edited by milosz - 10/30/13 at 9:08pm
post #71 of 86
Quote:
Originally Posted by devin_mm View Post

2 channel is single ended passive ground
3 channel is single ended active ground
4 channel is balanced
I don't know if someone has made a 5 channel one
6 channel is balanced with two active ground single ended amps

the price of my parts from glass jar audio for my 6 channel beta22 and 2 120VA S22's was ~$750 not including pot or case

 

That's not as scary as i thought it would be, especially when i would be more than happy with a 4 channel version.  hmm..

post #72 of 86
Quote:
Originally Posted by devin_mm View Post

2 channel is single ended passive ground
3 channel is single ended active ground
4 channel is balanced
I don't know if someone has made a 5 channel one
6 channel is balanced with two active ground single ended amps

the price of my parts from glass jar audio for my 6 channel beta22 and 2 120VA S22's was ~$750 not including pot or case

Yeah, I think if you include the price of pot the cost could be quite a bit higher.....   :evil:

post #73 of 86

Yeah that is true with Goldpoints @~$200.  Still though, i was under the impression 1k was the entry fee if you wanted to play.  Its actually something i can realistically think about now...

post #74 of 86

The Valab attenuators available through eBay are a very good low-cost alternative to Goldpoint and Khozmo attenuators. I've used them in a number of projects- they sound good and have been very reliable. Valab has both ladder and series type attenuators;  I prefer the ladder type.

 

Others who have used them have also reported good results.

 

 

Valab ladder-type attenuator.  I paid about $30 on eBay.

  • 1% KOA metal film resistors used, 
  • Silver/Copper/Tin solder used (lead free)
  • Switch seems high quality, I have not had any reliability issues with these

 

 

Processed By eBay with ImageMagick, z1.1.0. ||B2

post #75 of 86
Quote:
Originally Posted by milosz View Post
 

The Valab attenuators available through eBay are a very good low-cost alternative to Goldpoint and Khozmo attenuators. I've used them in a number of projects- they sound good and have been very reliable. Valab has both ladder and series type attenuators;  I prefer the ladder type.

 

Others who have used them have also reported good results.

 

 

Valab ladder-type attenuator.  I paid about $30 on eBay.

  • 1% KOA metal film resistors used, 
  • Silver/Copper/Tin solder used (lead free)
  • Switch seems high quality, I have not had any reliability issues with these

 

 

Processed By eBay with ImageMagick, z1.1.0. ||B2


I have just assembled a similar attenuator kit i bought on ebay, good bit of kit for the price but next time i will probably go for a proper goldpoint.  Just a shame they no longer offer ladder style versions.

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