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Threshold - SA/1 monoblocks

1-.A bit of History:

Amonst the entire
THRESHOLD range of amplifiers designed by the Master (we mean Nelson PASS), we have powerful ones, less powerful ones, big and small, white and black... But if we ask "what is the most beautiful one", surely the SA/1 monoblocks, with its huge Vu-meter, will be in the first position !

Remark: For those who have never listen to a SA/1 pair, be careful: this baby is not only a beautiful one ! it is also a first class performer...

A few weeks ago, POWER ELECTRONICS has been contacted by a SA/1 owner: this man wanted to change the main power supply capacitors and improve a few things of this venerable class A amp... We remind you that POWER ELECTRONICS specializes in high-end components repair and upgrades (although they can also repair almost everything...) and contacted us to follow their work on these SA/1 monoblocks.
You can find all the necessary information about POWER ELECTRONICS
on this page.

2-.The SA/1 monoblocks restored by POWER ELECTRONICS.

When they arrived, the SA/1 were dusty and they had not seen a service center since they went out of the factory ! please note that this also shows the reliability of the products designed by Nelson PASS...

The client has asked for the following operations:
  • replacement of the main Power Supply capacitors with RIFA capacitors
  • replacement of the main output Binding Posts by the extremely beautiful (and extremely expensive...) WBT Nextgen Cu.
  • replacement of the cables going from the output stage to the binding posts connectors.
  • replacement of a few other internal cables
  • complete adjustment of the Bias for the two monoblocks (of course).
Repairing or changing the huge power supply capacitors on a so powerful, so current capable, amplifier is not a thing that you should try to do if are not a skilled technician... Compared with the cheap "made in China" amplifiers, we are in another galaxy...

The work performed by POWER ELECRONICS has been done with a lot of care, and the best proof is to show the following photographies:

The two SA/1 monoblocks turned on after the work completion: note the 4 big RIFA capacitors

We have said that the SA/1 are beautiful: just look at them...


On the following photography, we have a perfect view on the big RIFA capacitors, decoupled by 4 small VISHAY capacitors. We can also see the care and the attention of the details: all the cabling is perfectly clean, note the gauge of the cables (we have a lot of Ampere flowing here), a metal plate has been realized to properly connect the Ground and the negative poles of the capacitors. Nothing to add: it is perfect...

The client has also asked to change the original binding posts by the excellent WBT Nextgen Cu: look at the yellow square herebelow to see the change.

The new WBT Nextgen Cu output connectors

Another view of the excellent capacitors connection

This photo shows the change of the cables going from the input RCA connectors to the amplifier input stages. POWER ELETRONICS has used an excellent and well known silver cable as a replacement of the factory original cable. You can also see the WBT Nextgen Cu output connectors.

The new silver (KIMBER) input cable installed by POWER ELECTRONICS

Well... you like these SA/1 monoblocks ? do not worry, you are normal, it is a so beautiful amp !...

This article has been written by

Creation date : 22/06/2011 @ 16:39
Last update : 09/11/2014 @ 19:16
Category : Threshold
Page read 2975 times

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Reactions to this article

Reaction #2 

by Nounours18200 09/02/2013 @ 19:08

Yes MLAS, you are right, the resulting capacity is 88.000µF instead of the original 120.000µF, but the choice of the new Rifa value has been decided by the client himself... Personnaly, I would have not reduced the total value, I always try to increased it, but the client is the king ! ...

Reaction #1 

by MLAS 24/08/2011 @ 18:15

Very nice job the RIFA PEH169 seems to be a highly regarded large can on different fora.On the first pic you can see in the left amp that the old cans (grey ones) are still in.They look like Mepco's though from the 'E' series and not the blue Mallory's that used to be in the S/1000's and SA/1's.The metal plate connecting the large caps is standard on al Thresholds from that series (SA and S) and was already there. It connects all the caps together in a parallel capacitive circuit (not only the minuses k) to make one large bank of 88.000 uF in this case of the 100V Rifa's. Original values were the 80Volts 30.000 uF blue Mallory's that gave a total value of 120.000 uF.Curious what they count for this job. If you have the parts and a good soldering skill and you know how the bias works (heatsink temp of 50 degrees Celcius, current draw from the 230V AC line of 1.5 Amps is okay) you can do it yourself quite easily. But don't try this at home kids!
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