• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Used int amp please help to figured out?

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arrjmai

Member
Joined 2013
Hi,

I am newbie here and I would like to ask for a favor for some help to figuring out what are these parts for.

I am recently bought used Unison research Simply four.

I could not contact the former user since this unit was third hands own by me.

The first owner modified the unit by replaced coupling caps and some electro caps on the pcb board and also bypass coupling at the speaker terminal jack.

I have replaced those power coupling bu Mundorf and took off the by pass.

I still wonder Are these part in the picture I marked by red circle were original function by the original Unison research or just some tweak modification.

I am not good at electrical and have just a few experiences on modification.

Could you guys please explain me what are these caps work for and do they actually just work for some tweak and the unit could actually do not need them.

Thank you so much.

Kind regards,

ar




img_5589.jpg
 
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arrjmai

Member
Joined 2013
azazello said:
Maybe caps 200 uF/400V and 0.47uF/400v are addition to PS filter to decrease hummm-50 or 60 Hz /I don't know where You live/....If it is like I thing, better don't remove caps.
Click to expand...

Thank you so much azzazello. If it's to help decrease hum I will leave them. I only thought that it might also decrease sound quality too that why I thought about to remove these caps.
 
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arrjmai

Member
Joined 2013
Thank you again. It means power send from toroidal to 4700uf 400v caps to supply the amp unit then between this supply cap is by pass by 220uf400v and 0.47uf400v to cut off hum. Am I right? So these caps acts like high pass filter?

I could see former user has hum problem he even by pass at speakers terminal. Be fore I took those caps by pass at speakers terminal. The sound was bright and lean but after I removed the sound was fuller and sound stage was wider.

I wonder if I remove these caps filter at power supply stage. it would bring more open sound.
 
azazello

azazello

Member
Joined 2008
You can try to see where goes the wire from +point of every cap. If it goes to another el. cap in PSU with nominal uF and 400-450 v or to two green resistors, that are added, this cap is for filtering. Don't forget to switch off amp and disconnect it from wall, when You check. /Connect big cap between output connectors is very bad decision.../.
 
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A

arrjmai

Member
Joined 2013
Thank you Azazello for your help. I have checked. The negative from el. jensen cap is go to negative route where big black(to spealers terminal), small black(to the board), brown (to transformer) cables has joined at solder point and positive goes to the red cables(to board,to transformer). This means the el. caps act as LF right and the film caps act as HF filter right?

I wonder of these caps's value. If they are help smoothing out or also decrease sound bandwidth as well.
 
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