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Mirand TSSA V4 and V8 Lateral mosfet amp

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sonnya

sonnya

Member
Joined 2001
mirand-audio.dk/?post_type=product
Classic PSU versus SMPS1200A180/400 (Hypex)

Hi, we have done some testing here on the SMPS1200A400 supply from hypex. Our expectation was very high given the positive feedback from others who have used the Supply from Hypex.

At first it does sound fine, but compared to the classic psu i used before it lacks energy and dryness in the low end of the frequency spectra. It does got even worse when you compare those two PSU i have been testing with.

DUT is TSSA V4 with one common supply only.

Item 1) Hypex SMPS1200A400 is an 1.2KW supply with +/-63VDC output which let us produce 210Watt into 8R load.
Item 2) 500VA Noratel potted transformer + 60.000uF ALC10 capacitors + Fairchild Stealth diodes with +/-50VDC which let us produce 120Watt into 8R load.

Normally an higher headroom will help us to get more control. But the the stiffness of the supply plays an important role here. The RMS value of the hypex module is 10Arms which is on the paper more than the 7Arms value of the toroid used here.

I suspect that the current limiter in the SMPS plays an important role here. In the classic supply we do not have an current limiter.

The performance using the SMPS1200A400 is not bad in the mid and higher register frequency spectra .. it is equal to the Classis supply.

If we look at it from the builders point of view. The SMPS1200A400 is easier to get up and running than a classic supply, and also cheaper.

If you are going to go classic, you will need high quality capacitors (RIFA, BHC, Vishay, EC) with low ESR and ESL values preferable below 40mOhm. and a softstart and good quality toroid or R-core.

An classic supply can easily set you back by 400€. If you cannot afford good quality capacitors it is better to stick with the SMPS1200A400.

The heat from the SMPS1200A400 compared to the classic is more or less the same when running at 200mA idle. (Long run spec for idle on the SMPS1200A400 is 500mA - Or two modules running at 250mA of idle).

Shield the SMPS1200A400!!! If not and you are using passive volume control you will pick up noise from the SMPS (His and NOT white noise from the tweeter)... Like on most class D solutions (Sorry but that is the truth)

I hope this will give you an idea of what to choose. In this test i used Block RKE500/2x35VAC or noratel 500VA 2x35VAC, my Capbank with Fairchild stealth diodes, My softstart module.

Toroid from RS components RKD 500/2x35 130€
Capbank module 60.000uF ALC10 63VDC + Stealth diodes 147€
Softstart + fittings 114€
------
391€
====

SMPS1200A400 + fittings (Realistic) 276€
====

For europe i would suggest Multi-CB... They produce custom transformer

Transformer Centre Potted Pricing- Multi Circuit Boards

With TSSA V2 the SMPS1200A180 is the choice if not classic supply.

BR Sonny
 
H

hop.sing

Member
Joined 2009
Thank you Sonny for your observations!
As you know I use the v4 with one hypex smps and could not be happier. I did not find the specs for the max. idle current for the 1200/400 smps on the web and it is also not specified in the data sheet, but the data sheet says it can deliver 1/8 of its maximum power long term (though with a sine wave) and I figured that is a little above 1A. So I thought it is save to power two modules set to 400mA each.
The heatsink of the smps is still easy to touch under those conditions (around 20 degrees Celsius above the surrounding temperature)
It would be a pity if I had to run the amp cooler, because it sounds best biased as hot as the main heatsinks allow. Getting a second power supply would be an option, of course.
One thing I worry about is the temperature of the shunt regulator heatsinks, they are ca 45 degrees Celsius above the surrounding temperature (a little more than 70 degrees absolute)
That seems very hot.
Bass quality is not that important for me since I use two powered subs for frequencies under 80Hz, so I will probably stay with the smps. I did not shield anything but since I do not us a passive volume control and have short cabling to the connectors, it might be OK. There is no hiss, just noise which is barely noticeable with the ears right on the tweeter.
 
sonnya

sonnya

Member
Joined 2001
mirand-audio.dk/?post_type=product
hop.sing said:
Thank you Sonny for your observations!
As you know I use the v4 with one hypex smps and could not be happier. I did not find the specs for the max. idle current for the 1200/400 smps on the web and it is also not specified in the data sheet, but the data sheet says it can deliver 1/8 of its maximum power long term (though with a sine wave) and I figured that is a little above 1A. So I thought it is save to power two modules set to 400mA each.
The heatsink of the smps is still easy to touch under those conditions (around 20 degrees Celsius above the surrounding temperature)
It would be a pity if I had to run the amp cooler, because it sounds best biased as hot as the main heatsinks allow. Getting a second power supply would be an option, of course.
One thing I worry about is the temperature of the shunt regulator heatsinks, they are ca 45 degrees Celsius above the surrounding temperature (a little more than 70 degrees absolute)
That seems very hot.
Bass quality is not that important for me since I use two powered subs for frequencies under 80Hz, so I will probably stay with the smps. I did not shield anything but since I do not us a passive volume control and have short cabling to the connectors, it might be OK. There is no hiss, just noise which is barely noticeable with the ears right on the tweeter.
Click to expand...

It is my mistake, i was looking at the iout AUX .. Sorry. With the right cooling it can continuously deliver 325W.

The Shuntregulator heatsink is under observation. If you wants to lower it, R4 and R56 is 68R giving 9mA opamp outputstage idle. They can safely be changed to 120R giving 5mA.

R8 and R55 is 100R, they can be changed to 150R

This will lower the temperature by around 5 degrees on the black heatsinks when running of +/-65VDC.

The shielding has nothing to do with the amplifier module itself, only SMPS in general. High impedance signal lines picks up the emission from the SMPS.

"Bass quality" in most cases it will just be fine with the SMPS1200A400, but i think there is a little improvement here to my ears by using classic supply.

BR

Sonny
 
meanman1964

meanman1964

Member
Joined 2006

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pdb

pdb

Member
Joined 2007
sonnya said:
... "Bass quality" in most cases it will just be fine with the SMPS1200A400, but i think there is a little improvement here to my ears by using classic supply. ...
Click to expand...
Thanks for the writeup on smps vs classic psu. Have you any experience with or interest in trying the Connexelectronic SMPS500 or bigger? They look neat and Christi seems to know what he is doing. He also has several capacitor modules to give the smps a bit more grunt for subwoofer duties etc But whether they can sustain a high bias class A I don't know.
 
L

livingstone

Member
Joined 2009
Really interesting and important question of power supply.
Would be nice here to have a choice to buy transformers of non-toroid types for reasonable prices. But market does not offer this.
Toroids are considered by many serious audio engineers as available but not a good choice for audio applications.
 
sonnya

sonnya

Member
Joined 2001
mirand-audio.dk/?post_type=product
Temperature margin on small 38mm height heatsinks

hop.sing said:
Thank you Sonny for your observations!
As you know I use the v4 with one hypex smps and could not be happier. I did not find the specs for the max. idle current for the 1200/400 smps on the web and it is also not specified in the data sheet, but the data sheet says it can deliver 1/8 of its maximum power long term (though with a sine wave) and I figured that is a little above 1A. So I thought it is save to power two modules set to 400mA each.
The heatsink of the smps is still easy to touch under those conditions (around 20 degrees Celsius above the surrounding temperature)
It would be a pity if I had to run the amp cooler, because it sounds best biased as hot as the main heatsinks allow. Getting a second power supply would be an option, of course.
One thing I worry about is the temperature of the shunt regulator heatsinks, they are ca 45 degrees Celsius above the surrounding temperature (a little more than 70 degrees absolute)
That seems very hot.
Bass quality is not that important for me since I use two powered subs for frequencies under 80Hz, so I will probably stay with the smps. I did not shield anything but since I do not us a passive volume control and have short cabling to the connectors, it might be OK. There is no hiss, just noise which is barely noticeable with the ears right on the tweeter.
Click to expand...


I was measuring the heatsink at me. My room temperature is 25 degrees Celcius. The heatsinks are 60 degrees Celcius. Leaving an temperature rise of 35. The heatsink is 10K/W which also is the case for the transistors.

So the internal temperature rise is also 35K.

In total is it a temperature rise of 70 degrees. The die max temperature is 150 degrees celcius leaving us with an margin of 80 degrees celcius ambient temperature. The ambient temperature in the amp should newer get that high.. in fact in no amp.

BR

Sonny
 
H

hop.sing

Member
Joined 2009
sonnya said:
I was measuring the heatsink at me. My room temperature is 25 degrees Celcius. The heatsinks are 60 degrees Celcius. Leaving an temperature rise of 35. The heatsink is 10K/W which also is the case for the transistors.

So the internal temperature rise is also 35K.

In total is it a temperature rise of 70 degrees. The die max temperature is 150 degrees celcius leaving us with an margin of 80 degrees celcius ambient temperature. The ambient temperature in the amp should newer get that high.. in fact in no amp.

BR

Sonny
Click to expand...
My mistake might have been to underestimate the heat in the closed box... I opened it right before I measured the temperature on the sink... 35 degrees seems reasonable in a enclosure with 50 degrees heatsinks, so everything is just fine and the smps runs even cooler, than I thought...
 
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