[IPodPJ]

Quote:

This is something that I've been curious about regarding the Beta 22. It seems that hum which is noticeable with very sensitive headphones (such as IEMs) is a common problem even when the PSU is in a different chassis. I wonder why, and what's special about builds that don't have this problem.
 

Wire routing issues, and capacitive coupling issues with the chassis panels to name two.  Also, if you are going to use IEMs you want to have the gain set as low as possible.  I personally wouldn't use IEMs for anything other than portable use, in a studio, or live on stage, so it's not something I would ever purposely tailor a home headphone amp to.  That's not to say you can't use them, but why would you instead of full sized headphones?
 
When I used to use IEMs, I only used them with portable amplifiers, whether at home or on the go. Once I got into desktop or home amps though, full-sized was the only way to go.

 

[visualguy]

Quote:

Wire routing issues, and capacitive coupling issues with the chassis panels to name two.  Also, if you are going to use IEMs you want to have the gain set as low as possible.  I personally wouldn't use IEMs for anything other than portable use, in a studio, or live on stage, so it's not something I would ever purposely tailor a home headphone amp to.  That's not to say you can't use them, but why would you instead of full sized headphones?
 
When I used to use IEMs, I only used them with portable amplifiers, whether at home or on the go. Once I got into desktop or home amps though, full-sized was the only way to go.

On multiple different Beta 22 amps I heard hum with IEMs (even when the gain was set to 2x and the attenuator was in the off position). On some amps the hum is in both channels, and in some in just one. It seems like the Beta 22 is particularly susceptible to this... I guess it would be nice if there was information out there on how to avoid the different causes of this problem.
 
IEMs may not be the type of headphones that you would normally use with a Beta 22, but they should work without hum as they do with many other amps...
 
Anyway, this is off-topic, but wanted to ask since the subject came up.
 

 

[MacedonianHero]

How about a B22 with a High (10X) and Low (5X) gain switch? Is it possible?

Could drive the HE-6s down to my Ed. 8s.

 

[baka1969]

Quote:Originally Posted by MacedonianHero 

"How about a B22 with a High (10X) and Low (5X) gain switch? Is it possible?

Could drive the HE-6s down to my Ed. 8s."


When I was having my b22 rebuilt I asked this same question and Corey (who did the work) posed that question to Ti and was told it's not recommended.

 

[MacedonianHero]

Quote:Originally Posted by MacedonianHero 

"How about a B22 with a High (10X) and Low (5X) gain switch? Is it possible?

Could drive the HE-6s down to my Ed. 8s."


When I was having my b22 rebuilt I asked this same question and Corey (who did the work) posed that question to Ti and was told it's not recommended.

But we can send people to the moon and robot missions to Mars....it would be a fantastic product that would really get my attention. I know, I want it all.

 

[fishski13]

Quote:

How about a B22 with a High (10X) and Low (5X) gain switch? Is it possible?

Could drive the HE-6s down to my Ed. 8s.

difficult to do without a custom reworking of the boards - you have multiple compensation caps and resistors to switch for each gain setting.  adding signal distance with an off-board switchable gain in the feedback loop has it's own problems as well. 
 

 

[MacedonianHero]

difficult to do without a custom reworking of the boards - you have multiple compensation caps and resistors to switch for each gain setting.  adding signal distance with an off-board switchable gain in the feedback loop has it's own problems as well. 
 

True, but not impossible. I think it would help make the B22 a more "one size" fits all amp.

It would need a fab spin, and a few other components. But I think there could be a market for it.

 

[baka1969]

Quote:Originally Posted by MacedonianHero 


"But we can send people to the moon and robot missions to Mars....it would be a fantastic product that would really get my attention. I know, I want it all."


This isn't science. It's audiophilia. Lmao! That just sounded wrong didn't it?

Seriously the question and response is still on the AMB site. Don't ask me to explain. Maybe Corey or someone else can explain it in detail?

 

[scottiebabie]

Quote:

difficult to do without a custom reworking of the boards - you have multiple compensation caps and resistors to switch for each gain setting.  adding signal distance with an off-board switchable gain in the feedback loop has it's own problems as well. 
 

difficult but not impossible. hows this for a solution - make a TRS male to TRS female adapter cable & drop a 22-33ohm resistor on the +signal conductor side. if im not wrong, output impedance on B22 are sub 1ohm so an additional 20-30ohm on top shouldnt make much difference in load matching. the drop in voltage (ie.gain) should provide enuff vol headroom for low z cans. just a thought ya.
 
 

 

[IPodPJ]

Quote:

On multiple different Beta 22 amps I heard hum with IEMs (even when the gain was set to 2x and the attenuator was in the off position). On some amps the hum is in both channels, and in some in just one. It seems like the Beta 22 is particularly susceptible to this... I guess it would be nice if there was information out there on how to avoid the different causes of this problem.
 
IEMs may not be the type of headphones that you would normally use with a Beta 22, but they should work without hum as they do with many other amps...
 
Anyway, this is off-topic, but wanted to ask since the subject came up.

It's a definite possibility I imagine.  I haven't tried IEMs on my amp yet but I have tried low impedance and high impedance full size phones with high sensitivity.  Some IEMs have incredibly high sensitivity ratings, so I don't know how they will sound.  I can't imagine there being any problem, but a lot of people have mentioned that issue with the Beta22 in general, you are correct.
 

 

[IPodPJ]

Quote:

difficult to do without a custom reworking of the boards - you have multiple compensation caps and resistors to switch for each gain setting.  adding signal distance with an off-board switchable gain in the feedback loop has it's own problems as well. 
 

 
Quote:

Quote:

difficult to do without a custom reworking of the boards - you have multiple compensation caps and resistors to switch for each gain setting.  adding signal distance with an off-board switchable gain in the feedback loop has it's own problems as well. 
 

True, but not impossible. I think it would help make the B22 a more "one size" fits all amp.

It would need a fab spin, and a few other components. But I think there could be a market for it.

Agreed.  I wish the Beta had this option, too.
 

 
Quote:

difficult but not impossible. hows this for a solution - make a TRS male to TRS female adapter cable & drop a 22-33ohm resistor on the +signal conductor side. if im not wrong, output impedance on B22 are sub 1ohm so an additional 20-30ohm on top shouldnt make much difference in load matching. the drop in voltage (ie.gain) should provide enuff vol headroom for low z cans. just a thought ya.
 
 

That's different than changing the gain on the boards.  People have made switches using resistors at the output for variable volume levels, but adding resistance here is quite different than doing it where it needs to be done properly.
 
BTW, the Beta's output impedance is 0.01 ohm.
 

 

[visualguy]

Quote:

It's a definite possibility I imagine.  I haven't tried IEMs on my amp yet but I have tried low impedance and high impedance full size phones with high sensitivity.  Some IEMs have incredibly high sensitivity ratings, so I don't know how they will sound.  I can't imagine there being any problem, but a lot of people have mentioned that issue with the Beta22 in general, you are correct.
 

Try Shure SE530 or SE535 which have a sensitivity of 119dB and impedance of 36 ohm. It seems that many Beta 22 amps (particularly 4-board) hum with these...
 

 

[IPodPJ]

Quote:

Try Shure SE530 or SE535 which have a sensitivity of 119dB and impedance of 36 ohm. It seems that many Beta 22 amps (particularly 4-board) hum with these...

That's extremely sensitive, but I see no reason if it's properly built and set to a gain of 2 why it should, especially in two chassis.  You could always send me a pair of those IEMs and we can find out.

 

[fhuang]

maybe that's why rp030 cast so much?  my jh16 didn't hum with music or no music(pause or stop).  nobody besides me and a couple guys heard of this amp and people here just keep "talking".  mods don't seems to care at all.  good job

 

[winzzz]

^ a lot of cheaper desktop amps doesn't hum with iem so whats your point ?

so people can charge as much money as they like just because their amps doesnt hum with iem ? how idiotic is that..:rolleyes: