UGS adventures

[korben69]

No worries wayne

 

[wayne325]

pot on input

My UGS is standing in as a replacement of a P1.7 clone. I kept all the
metalwork, input switching and volume control stuff. So I have my pot on
the output side and it works like a charm. The advantage of the pot on the
output is that it is attenuating noise as much as signal. THe disdvantage
(to some attenuation methods, specifically a pot) is that the output
impedance of the amp changes with the volume setting.

I think the UGS has plenty of cojones and doesn't seem to have any issue
at all with output impedance in my setup.

Boy it sounds good.

 

[Zen Mod]

it will work both ways , certainly .

you can even look at pot at output as on xconductance converting resistor

but something is wrong if you have need to attenuate noise

 

[samoloko]

Is It wrong to use 20K Pot at Input with UGS

 

[Zen Mod]

Is It wrong to use 20K Pot at Input with UGS

it isn't

 

[analog_sa]

Is It wrong to use 20K Pot at Input with UGS

It will be much more wrong to use 20k at output.

 

[wayne325]

but something is wrong if you have need to attenuate noise

Agreed. But we're talking about a UGS here, the thing is dead quiet. I don't
need to attenuate the output, it's what I had available and it works fine.

 

[wayne325]

It will be much more wrong to use 20k at output.

Why are you saying this?

 

[Zen Mod]

because output impedance of attenuator itself will define output impedance of entire combo ;

I presume that you have some interconnects right after attenuator ?

 

[samoloko]

UGS doesn't care whether will see 10 K or 20 K Pot at Input regarding his high Input Impedance
so I think that It will be better (for source) to use 20 K Pot at Input of UGS
Is It right

 

[Zen Mod]

........
Is It right

yup

 

[samoloko]

thx Zen Mod
would you share your way of driving UGS

 

[Zen Mod]

well - I don't have UGS , but ...... "proper" way is :

XLR's on input ( if you go with unbalanced signal , just tie pins 1&3 in xlr plug) , balanced relay selector , balanced volume , UGS , output

 

[samoloko]

GREAT
thank you very much

 

[wayne325]

because output impedance of attenuator itself will define output impedance of entire combo ;

I presume that you have some interconnects right after attenuator ?

Yes, there are interconnects. They have small capacitive and inductive
reactances, the input at the far end is nearly purely resistive impedance, and
the frequencies we're talking about are very low. These interconnects are
XLRs and they are well shielded and the shield is grounded. The result is that
there is basically no distortion or noise from the interconnect. My thinking is
that the distortion and noise of the preamp is higher. But I haven't
calculated it.

Have you done such calcs to come up with your conclusion? I wouldn't mind
seeing a proper analysis that says go one way or the other. It would mean
some rewiring in my amp but it's possible. Everything is modular - the
switching, volume, amp, PSU are all separate.

 

[Zen Mod]

.....Have you done such calcs to come up with your conclusion? ........

nope , I didn't ; there is no need for that

I grew up hangin' around pro equipment ...... and - this is the way to do it , considering impedances , traces etc .

it's usually best way considering sound too , but that only your ears can decide

don't let anyone else to do listening instead of you

 

[Onvinyl]

Finally, after some four years, I stuff my ugs boards

I spiced it, and played around a bit. Did anyone try to hold the fets on constant current by the use of bjt of opposite polarity clamped around it?

My sim shows a decrease in distortion roughly by ten times!

Rüdiger

 

[gl]

Could you post a schematic?

GL

 

[generg]

Lower distortion

........ would be interesting for me too, UGS lies in the corner. Could be a revival!

 

[Onvinyl]

Here you are with the relevant part...

Rüdiger