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Roll Call: Who's building, built, or thinking of building a beta22? - Page 197

post #2941 of 3166

if you're not volume matching with a DVM and test tone, all bets are off.

 

a dual-mono PS will give you best measured performance.

 

i had a hard time volume matching a balanced B22 with dual-mono PS and stepped attenuator between balanced and unbalanced - running unbalanced was wired dual-mono as well.  i heard a difference, but i also hear a difference between the balanced outputs wired for unbalanced vs unbalanced outputs from my BM DAC1 - again volume matched with various amplifiers.  the balanced XLR wired for unbalanced sounds better than the unbalanced RCAs.  identical wire.

 

stick to the BOM.  if you have a cap fetish, you could replace the ceramic compensation caps with some film or mica.  space is tight though.

 

if you feel you need extra power, and/or you feel your source sounds better via balanced, balanced could be considered.

 

if you feel the need to go high-end with wire, i would recommend various Belden at $0.30-0.40/ft.

 

personally, i would splurge on a decent pot/SA.  and if going with a single chassis, get an encapsulated/shielded custom wound TX.

post #2942 of 3166
Quote:
Originally Posted by fishski13 View Post

if you're not volume matching with a DVM and test tone, all bets are off.

 

a dual-mono PS will give you best measured performance.

 

i had a hard time volume matching a balanced B22 with dual-mono PS and stepped attenuator between balanced and unbalanced - running unbalanced was wired dual-mono as well.  i heard a difference, but i also hear a difference between the balanced outputs wired for unbalanced vs unbalanced outputs from my BM DAC1 - again volume matched with various amplifiers.  the balanced XLR wired for unbalanced sounds better than the unbalanced RCAs.  identical wire.

 

stick to the BOM.  if you have a cap fetish, you could replace the ceramic compensation caps with some film or mica.  space is tight though.

 

if you feel you need extra power, and/or you feel your source sounds better via balanced, balanced could be considered.

 

if you feel the need to go high-end with wire, i would recommend various Belden at $0.30-0.40/ft.

 

personally, i would splurge on a decent pot/SA.  and if going with a single chassis, get an encapsulated/shielded custom wound TX.

Hi fish, thanks for the reply. Nah haven't had the volume DVM'd for matching, it was using the standard 50k RK27 Alps pot before on the amb board of it's own but I felt I needed something more so I tried a spare Goldpoint mini v I had lying around, a sense of more clarity was heard but I had to move that to another fancy amp build I was doing for a friend, so I used a valab stepper that get's good recommendations from here and various other forums (Valab themselves specified that it is matched on both channels and few diyaudio posters measured it).

 

It is in separate enclosure, running off a single s22. The b22 will be for driving headphones so the single s22 will be plenty for headphone duty, should I need it for pre-amp or speaker functions then I will add in another s22 but I have other better amp's to fill in that role.

 

I love Belden, used them before for power cables, good quality stuff. 

 

Thinking of new way's to dress this b22 amp in better clothes. I was originally thinking along the lines using the LCDruino kit and use the AMB attenuator but it would be too much work especially for it to be acting like a pot.


Edited by DefQon - 5/29/13 at 4:42am
post #2943 of 3166

i've preferred the TKD pots over the RK27 and the precise volume control a pot offers over a SA, but am starting to come around to SAs.  i've not tried the Valab, but i do like the Goldpoints and Broskie's.  i have a GP in my own B22.  again, i would splurge on an attenuator/pot, TX, and larger on-board heat sinks before anything else.

 

i will have a dual-mono balanced B22 in house this summer and am excited to do some more balanced/unbalanced comparisons with my own B22.  both amps are virtually identical component wise and GP SAs.

 

if you don't need the power of a B22, with the newer generation opamps, the M3 is equally an alternative, albeit different sounding.  while you can still bias the M3 to the same stock B22 quiescent current, 120-160mA, assuming appropriate thermal management and TX sizing, it doesn't have the V-swing of the B22.  still plenty for the large majority of HPs though. you still have the option to up the o11 voltage to 32-36V and use appropriately rated opamps.  again, i wouldn't skimp on an attenuator/pot for the M3. 

post #2944 of 3166

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post #2945 of 3166

Just a note for anyone building in separate enclosures that are made of anything but steel, you will need a custom shielded transformer for your Sigma22.  I used 2 aluminum cases from parmetal and I had a little buzzing and humming until I replaced the transformer.  Aluminum doesn't offer any shielding against the EMI from the transformer, but it is WAY easier to make holes in with my limited tools :p

post #2946 of 3166

i had and i have a balanced beta-22 in one chassis.

never had problems with noise or buzz or hum...

post #2947 of 3166

I think it partly depends on what headphones you are using.  I was using Denons which are pretty low impedance and high efficiency so I could hear some of the transformer noise.  In fact, I could hear it VERY clearly with my IEMs and I can still hear much less noise if I try with IEMs, but I can't hear any of the noise with the Denons after I changed the transformer for a sheilded one.  People seem to have a lot of mixed results with single case builds and transformer noise, so there are probably more factors at play than I know about.  The bottom line for me is if you can't hear it, you're good!

post #2948 of 3166

i tried some headphones and never had problems.

only with the jvc dx-1000 a little hum in the second version of my beta with lower gain.

very strange

post #2949 of 3166
an encapsulated/shielded TX is cheap insurance to prevent EMI in a single chassis build. using shielded wire for longer runs of input wiring to the pot and from the pot to the boards helps with RFI even if housed in a 'shielded' chassis IME.
post #2950 of 3166
Quote:
Originally Posted by fishski13 View Post

i've preferred the TKD pots over the RK27 and the precise volume control a pot offers over a SA, but am starting to come around to SAs.  i've not tried the Valab, but i do like the Goldpoints and Broskie's.  i have a GP in my own B22.  again, i would splurge on an attenuator/pot, TX, and larger on-board heat sinks before anything else.

 

i will have a dual-mono balanced B22 in house this summer and am excited to do some more balanced/unbalanced comparisons with my own B22.  both amps are virtually identical component wise and GP SAs.

 

if you don't need the power of a B22, with the newer generation opamps, the M3 is equally an alternative, albeit different sounding.  while you can still bias the M3 to the same stock B22 quiescent current, 120-160mA, assuming appropriate thermal management and TX sizing, it doesn't have the V-swing of the B22.  still plenty for the large majority of HPs though. you still have the option to up the o11 voltage to 32-36V and use appropriately rated opamps.  again, i wouldn't skimp on an attenuator/pot for the M3. 

By dual mono balanced b22 you mean by 2 boards configured into mono config or ?? 

 

The M3 with bass boost is still on my to build list to see how well it complements my SA3k which supposedly matches very well. But tbh I'm done with all headphone gear, just planning to get a good source and possibly the 007 MK1's and call it a permament end game for me.

post #2951 of 3166
Quote:
Originally Posted by fishski13 View Post

an encapsulated/shielded TX is cheap insurance to prevent EMI in a single chassis build. using shielded wire for longer runs of input wiring to the pot and from the pot to the boards helps with RFI even if housed in a 'shielded' chassis IME.

my amp has nullaudio power cables from the power section to the boards and the moon-audio black dragon in the amplifier section.

this cable is very good and does not cost a fortune

post #2952 of 3166
Quote:
Originally Posted by DefQon View Post

By dual mono balanced b22 you mean by 2 boards configured into mono config or ?? 

The M3 with bass boost is still on my to build list to see how well it complements my SA3k which supposedly matches very well. But tbh I'm done with all headphone gear, just planning to get a good source and possibly the 007 MK1's and call it a permament end game for me.

i meant to say dual-mono PS, as in a single o22 and TX driving a single balanced channel (2 boards), for a total of 2x o22 and 2x TXs to drive both channels (4 boards).
post #2953 of 3166

I wonder if it's possible to configure a 2 channel or 3 channel into a balanced setup. I know there are some discussion over the past 2 years with the passive configuration (i.e. 2 channel) already having a dedicated ground to itself I wonder if you one use this for the isolated ground from each board plus the signal in/out for balanced operation. Or a 3 channel, with the 3rd active dedicated board to handle both the other channel ground.


Edited by DefQon - 6/1/13 at 7:08pm
post #2954 of 3166
Quote:
Originally Posted by fishski13 View Post


i meant to say dual-mono PS, as in a single o22 and TX driving a single balanced channel (2 boards), for a total of 2x o22 and 2x TXs to drive both channels (4 boards).

correct,  but is possible one sigma22 for 4 boards, right?

post #2955 of 3166
Quote:
Originally Posted by alota View Post

correct,  but is possible one sigma22 for 4 boards, right?

I've built a b22 using 1 sigma for 4 boards. Not speaker duty though. Still plenty of power.

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