USSA-5 Build with Review

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manniraj

Member
Joined 2012
Thank you all I am mesmerised every bit of music being played over them. The vocals are outstanding with the mid range on my Audio Nirvana is just too good. My previous amp was (or is) M2x, which is a superb sweet sounding amplifier. I hope the USSA-5 also lives up to my expectations after 30-50 hrs of playing and I can keep my M2x for rest :)

Thanks Do, Vunce, Anthony this is a temporary cabinet as I have not mounted either the trafos or the PSU boards. This I think definitely deserves mono blocs and I am in the process of procuring the cabinets. Till that time I can use this for burn-in process. But I am still stunned that a DIY amplifier is absolutely dead silent and its just unbelievable in so far the amps that I have built like the Aleph J, V4, Sony VFET2, M2X etc.,

Thank you Fab for all the support that you provided and your manual is absolutely brilliant. Every step is clearly mentioned and explained :)
 
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Bfpca

Bfpca

Member
Joined 2007
A few measurements on my USSA5

Bandwidth was about 500khz -3db!
Power out about 32w into 8 ohms at <1%distortion.
Power out about 58w into 4 ohms at <1% distortion.
Power figures are for continuous output with both channels driven at 1khz
Wideband output noise is measuring .5mv which is higher than I would like. I have the chassis hard grounded to the power supply common, which may need to change. If I can get a quiet amplifier without using a ground isolator circuit then I prefer to do so.
We will see what future tests reveal.
I still have to tidy up a few items before I connect the amplifier to speakers, although I am curious to hear it.
 
M

manniraj

Member
Joined 2012
Bfpca said:
Congratulations Manniraj! Nice looking amplifier. With high efficiency speakers you will have effortless dynamics with this amp. It looks like you have generous sized heatsinks which is good for long term reliability.
Click to expand...

Thank you, yes I have the Audio Nirvana 96db and soon to be built Troels which are also similar sensitivity. The heat sinks are 300x150x83 and I have biased it to 65mA (1.3A) and after couple of hours playback I can still touch the heat sinks, so they are able to withstand the extra heat with higher bias.

Wiring on the amplifier, I just followed the basic principles of connecting both the PGND, GND on the amp boards from each of the PSU grounds. PSU grounds are not connected together. I have taken the speaker output ground from each of the PSU ground. No ground loop and absolutely dead silent. I have used a single NTC thermistor as a soft start in the mains AC line. Using a small EI core transformer to power the speaker protection board. I have connected the IEC earth ground to the chassis but I do not have another NTC thermistor to bypass the PSU grounds to the same chassis spot. I will get and do the wiring as a safety measure need to connect the PSU grounds to the chassis. Or maybe use a bridge rectifier as suggested on the hifisonix paper to isolate the chassis ground/AC noise getting into the PSU grounds.
 
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A

AnthonyA

Member
Joined 2017
Yup isolate the ground, using 10.ohm 5w bypass with 0.1uf or back forth diode bypass with 0.1uf

But since your using dual. Mono. You might have to do it both side.. Or both have to be ground broke from each side
. 2 sets of ground break to chasis depending if you connect the ground s of your rca or speaker together .. Only one point connection... Figure it out

Best point to use is the CT supply before the slb filter
 
fab

fab

Member
Joined 2004
fabaudio.online
Paid Member
manniraj said:
The amplifier is alive and playing beautifully in my make shift huge cabinet. I have now run it for around 2 hrs. Dead silent and I have used a big NTC thermistor as a soft start on the AC mains and no thump at all. With my Audio Nirvana super 8" drivers rated at 96db the amp is 99% dead silent and I can hear a very very slight hiss when I keep my ear close to the drivers. Otherwise I haven't build an amplifier which was so silent and that too with dual mono design. PSU's are borrowed from a friend temporarily which I built using the Prasi's CRC with LT4320 regulators.

Bias is stable 65mV with offset being <1mV even after 1 hr of playback.

How many hours should I run before making a judgement :)

.........................
Click to expand...
Hi manniraj

Nice implementation :):)
As pointed out by Pinnocchio, you need at least 50 or more hours to not hear any differences (it was my case ). But I encourage you to replace the wima input cap you have in place. I have indicated a better part number in the BOM and you can sure find better ones. I know the ones in the BOM is a good trade off quality / price.

Fab
 
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fab

fab

Member
Joined 2004
fabaudio.online
Paid Member
manniraj said:
Thank you all I am mesmerised every bit of music being played over them. The vocals are outstanding with the mid range on my Audio Nirvana is just too good. My previous amp was (or is) M2x, which is a superb sweet sounding amplifier. I hope the USSA-5 also lives up to my expectations after 30-50 hrs of playing and I can keep my M2x for rest :)

Thanks Do, Vunce, Anthony this is a temporary cabinet as I have not mounted either the trafos or the PSU boards. This I think definitely deserves mono blocs and I am in the process of procuring the cabinets. Till that time I can use this for burn-in process. But I am still stunned that a DIY amplifier is absolutely dead silent and its just unbelievable in so far the amps that I have built like the Aleph J, V4, Sony VFET2, M2X etc.,

Thank you Fab for all the support that you provided and your manual is absolutely brilliant. Every step is clearly mentioned and explained :)
Click to expand...
You are welcome !:):)
Fab
 
M

manniraj

Member
Joined 2012
fab said:
Hi manniraj

Nice implementation :):)
As pointed out by Pinnocchio, you need at least 50 or more hours to not hear any differences (it was my case ). But I encourage you to replace the wima input cap you have in place. I have indicated a better part number in the BOM and you can sure find better ones. I know the ones in the BOM is a good trade off quality / price.

Fab
Click to expand...

Thanks Fab, as per your manual the latest one the C2 is listed as "3.3UF ECW-FD2W335J or 4,7UF ECW-FD2W475J" or other better cap. And I am using the second one 4.7uF with Mouser part # MKS2B044701K00KSSD
So which one do you suggest I need to go with for best performance cost no bar :)
 
pinnocchio

pinnocchio

Member
Joined 2010
quebecdiy.forumactif.com/
Hi manniraj,

Depends greatly on your budget... The Panasonic (dipped) is very good, but then if you want much better you have many alternatives. What’s your max budget?

Keep in mind that the bigger the cap, the more emi/rfi it can pickup since it might not be shielded with the PCB anymore... You can always wrap a copper foil around the cap and solder a wire from the copper foil to the gnd lead from the PCB. If you’re able to find which lead of the cap is connected to the outer foil then you can connect it to the load side on the amp for better shielding.

Have fun and enjoy the music!
Do
 
M

manniraj

Member
Joined 2012
Thanks Do, I do not want to go the route of wrapping up the cap with copper foil and soldering a wire to the ground lead :)

Can you suggest like good ones with all round performance and goes with Troels Gravesen speakers and pairs well with a Korg B1 around $100 for a pair of caps? By the way what is that you have on your USSA5 amp?

Thanks again.
 
pinnocchio

pinnocchio

Member
Joined 2010
quebecdiy.forumactif.com/
I would stick with 4.7uF value, maybe 3.3uF (ask Fab). On my personal build I'm using Jantzen Alumen, Z-Cap 4.70µF. I've never been a fan of PIO caps. PIO were originally designed for very high voltage caps (if I remember correctly) and I never really liked the sound of them, but it is personal taste anyways. You may like them very much.

It's hard to give advice when audio taste is very subjective.

FWIW, I also very much like the ClarityCAP CMR, some of the Audyn caps and some of the Mundorf (without oil).

Do
 
M

manniraj

Member
Joined 2012
pinnocchio said:
I would stick with 4.7uF value, maybe 3.3uF (ask Fab). On my personal build I'm using Jantzen Alumen, Z-Cap 4.70µF. I've never been a fan of PIO caps. PIO were originally designed for very high voltage caps (if I remember correctly) and I never really liked the sound of them, but it is personal taste anyways. You may like them very much.

It's hard to give advice when audio taste is very subjective.

FWIW, I also very much like the ClarityCAP CMR, some of the Audyn caps and some of the Mundorf (without oil).

Do
Click to expand...

Thanks Do, how about the Mundorf EVO series which I linked in my above post. They are available locally and I know its genuine. Also did you wrap any copper foil on your Jantzen? Something like this - Jantzen 4.7uF 400V "Crosscap Series" MKP Capacitor
 
M

manniraj

Member
Joined 2012
Most of the WIMA or other caps I need to source it from either US or Europe which increases the cost manifold. Hence the reasoning to try Mundorf EVO or the Jantzen MKP which I can get it locally in India linked above which could come at the same cost as the WIMA MKP10 series that Vunce suggested if I include the shipping and customs :)

Thanks
 
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