Threshold SA/1 monoblocks cap issues, perhaps?

No need to bother the big man. I figured it out already

Ask Nelson Pass at DIYAudio.

I know this is an old thread. Does anyone here know the rail DC voltage is on these amps? I am thinking of changing my S/500 to strictly a class A amp and would need to reduce the voltage from the 76vdc it runs at now. 

Thank you 

Several months ago I borrowed these amps from a local audio dealer in Minneapolis. They had been on consignment for $3k many months and I commented to the salesman several times that I should take these home and give them a try. Each time he politely told me to try other amps as in his view, these were not so good.....not at all incredible like many other used amps his shop had for sale over the last year, in particular, a pair of Goldmund mono amps that were sold for $4k in just a matter of days. But finally my curiosity got to me. He did however tell me not to do any critical listening for 24 hours. Once I turned them on, I was to leave them on.

I had been on the hunt for a solid state amp to drive a pair of Sonus Faber Amati Futura speakers for the times when I did not want all the heat from using CAT JL-3 amps. I tried Odyssey and Belles amps with marginal success with these speakers. The tonality was coherent but was rather flat dimensionally, and the bass was not at all powerful like I had heard these speakers at the Chicago dealer showroom with the dealer’s suite of multiple top-level amps and speakers.

I was on the lookout for Plinius 102/103, BAT 600/655 and Symphonic Line RG1/4/7/Kraft amps. But all of these are hard to find so I finally decided to just give the SA/1’s a try. My room has three 20A circuits. Each CAT amp uses one circuit and the rest of the audio system along with a couple of floor lamps uses the third circuit. I disconnected the CAT amps and plugged the SA/1’s into those circuits with Dream State Dream Catcher power cords.

Upon power-up, each SA/1 had a low-frequency thump, not loud, but still noticeable. And unlike all other amps I had tried, there was a 60 HZ hum that I corrected by putting a cheater plug on one amp....not a solution I like to use for the long term but it was ok for the audition. There were no other noises at power-up, or buzz or hiss from the speakers. The system was dead quiet with no source and volume set very high (preamp is Aria WV5).

I played some music briefly to assure all was working and then did not listen until the next day as instructed by the salesman. The amps remained powered on. I checked the heat sinks late that night and they were cool to the touch which was a great surprise as I expected them to be at least warm during the idle operation.

The next day I was eager to try out the amps. A quick no-source test showed silence with the volume control very high. And the envelope please.......

....I have tried many amps, solid state and tube, with dynamic and electrostatic speakers, and never, I mean never, experienced an amplifier that was so forward in the mids. We typically associate brightness or fatigue with exaggerated treble, but not in the mids. Piano strikes were horrible, ringing, fatigue. The top frequencies too were exaggerated but this was moot with the midrange coverage. I tried multiple LPs, and switched to digital (Lampizator B6) and after just an hour or so, I could not listen to these amps any more. However, with all of the above "negative" observations, the bass performance was as outstanding as I heard at the Chicago dealer. These amps took control of the woofers like no other solid state amp I had tried at home up to that point. This was mighty impressive but moot based on the rest of the amps’ performance. I left the amps on for another 24 hours and tried again the next night. A quick listen here was all it took to confirm the sonic signature of these amps was the same.

When I took the amps back to the store, the salesman asked me about my observations. When I replied with my comments of midrange and treble forwardness and fatigue, he and his associate looked at me and both nodded. What once (30 years ago) may have classified this amplifier as the state of the art, well, unless this is to be used as a bass amplifier, I would not consider it. There are far too many amps at a fraction of the cost here that far outperform the SA/1’s. And with their size and weight, this requires even more justification to own these amps.

After this experience, I tried a VAC 70/70 which was wonderful in all but the lower bass as this amp has no chance at all to drive the Amati woofers. I then tried Wolcott P220 mono amps which drove the woofers very well but not quite to the level as the SA/1’. The Wolcotts, even with their mediocre resolution, were impressively tonally coherent. A return to the CAT JL-3’s and everything special about these speakers returned.

A few months later, just last week, I tried a Symphonic Line RG1 and this was absolutely stunning with the SF speakers. WOW would be an understatement. Still not the last word in bass like the CATs or SA/1’s but very impressive and awesome clarity.

I don’t know the age of the caps in the SA/1’s I tried, but the power supply with its ability to continuously drive the very demanding woofers in the SF Amati speakers indicated no issue here.

With all of the discussion in this thread about capacitors, perhaps the OP’s amps indeed need the caps replaced. But based on the previous post, I would not be in a hurry to invest in cap replacement. Instead, try some other amps before any additional expense is made to these amps.

E36D101HPN333ME92M 33000uF/100V 76mm In diameter about 4 inches long you need longer screws 10.32 US standard. These you can get at mouser they will ship to India $240 plus shipping.

E36D101HPN333ME92M   33000uF/100V 76mm In diameter about 4 inches long you need longer screws 10.32 US standard. These you can get at mouser they will ship to India $240 plus shipping.