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Old 26th March 2020, 02:45 PM   #1251
AnthonyA is offline AnthonyA
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Sexay..

Like that wooden box.
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Old 26th March 2020, 02:49 PM   #1252
brianco is offline brianco  Ireland
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@Bfpca

Nice job.

BUT one thing worries me. It appears that there is an UNventilated glass/perspex cover over the heatsinks. BUT it could well be that the pic. has not transferred well. Also You really do need - in case they are not attended to - ventilation below the heatsinks.
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Old 26th March 2020, 06:24 PM   #1253
Bfpca is offline Bfpca  Canada
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Quote:
Originally Posted by brianco View Post
@Bfpca

Nice job.

BUT one thing worries me. It appears that there is an UNventilated glass/perspex cover over the heatsinks. BUT it could well be that the pic. has not transferred well. Also You really do need - in case they are not attended to - ventilation below the heatsinks.
Thank You. The pictures did not turn out well. iPad camera with low light in the room. Sorry for that. I just wanted to get something out there as a documentation of another USSA5, albeit an unusual one.
The top is actually covered in aluminum window screen. The top cover is mostly a frame to support the screen. This allows maximum ventilation for the heat sink array in the rear section. In the front I could have a much smaller opening. The 800va transformer and other parts do not get more than a little warm. The rest of the box is all aluminum except for the front panel which is 1/2” mdf.
It is heavy, with all the iron in the chokes and big transformer. I will likely do a better job on the chassis in the future. I added a relay to short out the NTC surge suppressor as I could smell that it was hot and it dropped 1-1.5 volts AC. This amp will do over 60w into 4 ohms which should be enough for most of my listening on the speakers I currently use. I also have an Aleph J which is about 30w into 8 ohms but only 16 into 4 ohms, so this amp offers a big increase in power at 4 ohms.
I have yet to install the amp on my main speakers. I am going to put the PI3s away and get out a set of GR Research OB7s (88db and 8 ohms) that I have in storage and let the new amp loose on them for a while. I did seem to notice that the sound improved as the amp warmed up. Probably about 20 hrs on it now.
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Old 26th March 2020, 07:31 PM   #1254
ggetzoff is offline ggetzoff  United States
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Bfpca,

What are you using for C2? It certainly does make a noticeable difference.

Cheers,

Greg
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Old 26th March 2020, 07:52 PM   #1255
brianco is offline brianco  Ireland
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2Bfpca,

Thanks for your response; I am delighted that my vision was poor!! Certainly seems a good beast...ggetzoff has a lot of experience on these amps and I am sure that his advice is solid regarding C2 .. and, elsewhere, a really good run in period.
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Old 26th March 2020, 10:47 PM   #1256
Bfpca is offline Bfpca  Canada
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Quote:
Originally Posted by ggetzoff View Post
Bfpca,

What are you using for C2? It certainly does make a noticeable difference.

Cheers,

Greg
Hi Greg

I am just using the basic 4.7uf Wima that is cube shaped. I’m not sure what else I have in stock to replace it with. Solens for sure, A pair of the basic red Mundorfs but I think they are 2.2uf. Best cap is no cap in my books. The amp has DC protection but still I don’t like to push my luck too far when an expensive set of speakers are hooked up. I could go smaller than 4.7uf. My main system uses 2 subs to cover below about 45 hz.
My daily driver amps are monoblock f5T3 first watt amps with separate power supplies. 120w 8 ohms ,400w 2 ohms. Class A to 70w at 8 ohms. A hard act to follow. They are setup for dominant H2 distortion and sound fantastic IMO.
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Old 26th March 2020, 11:41 PM   #1257
fab is offline fab  Canada
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Hi Bfpca
You have a nice chassis implementation and you have put a lot of attention to careful heat dissipation
Why do not use the input cap indicated in the BOM? It is non-inductive Polypropylene film type and very not expensive ( a few dollars only) and definitely much better than the Wima...
I use 3.3uf in my USSA5.1.
The USSA5 is not meant for high power “boom boom” but more for delicacy...
Ussa5 is also H2 dominant (at least from low to medium power).

Fab
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Last edited by fab; 26th March 2020 at 11:44 PM.
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Old 27th March 2020, 12:34 AM   #1258
Bfpca is offline Bfpca  Canada
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Quote:
Originally Posted by fab View Post
Hi Bfpca
You have a nice chassis implementation and you have put a lot of attention to careful heat dissipation
Why do not use the input cap indicated in the BOM? It is non-inductive Polypropylene film type and very not expensive ( a few dollars only) and definitely much better than the Wima...
I use 3.3uf in my USSA5.1.
The USSA5 is not meant for high power “boom boom” but more for delicacy...
Ussa5 is also H2 dominant (at least from low to medium power).

Fab
I got the part number for that cap from the BOM!? It will do for a start.
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Old 27th March 2020, 01:30 AM   #1259
fab is offline fab  Canada
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I think you have the original one from an old manual....
Since no one really used this cap which I found was not up to the task I found another one which is still not a boutique cap but good sounding (at least to my ear)... it is surely not the best but still a good start.
See latest manual extract.
You can only get better with a better cap.
Fab
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