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Old 25th January 2004, 01:21 PM   #21
Mad_K is offline Mad_K  Norway
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Here's another closeup
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Old 25th January 2004, 01:43 PM   #22
Mad_K is offline Mad_K  Norway
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Some technical info:

-The circuit used is Henrik's XSOZ circuit, with 6,8R power resistor (Arcol HS50) instead of the 7,5ohm.

-Rails are at +/- 20VDC

-Bias is slightly greater than 4A per channel.

-MOSFETs are IRFP140A from Fairchild

-Dual discrete bridges made of 8 ISL9R3060G2 (30A, 600V Stealth Diode to247, Fairchild)

-Psu caps are Evox Rifa PEH200 22000uF/25V.

-220uF caps are Elna RJH bypassed with 0,15uF Evox Rifa PHE426.

-Light AC filtering with Evox Rifa PZB 300 in delta-arrangement.

-Circuit ground is connected to the chassis/AC GND via a ntc thermistor. I have also used a ntc to supress the turn on surge.

-Chassis temp is about 70'C. The heatsink carrying the MOSFETs is 77'C. The one carrying the power resistors is 112'C.
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Old 25th January 2004, 02:23 PM   #23
Fuling is offline Fuling  Sweden
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112 degrees C? Thatīs damn hot!!!
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Old 25th January 2004, 02:27 PM   #24
Henrik is offline Henrik  Denmark
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Hi Mad_K, sorry for calling you Kad_K.

Quote:
Originally posted by Mad_K
The penalty for this is a firebreathing hot amp that runs all of the components on its limits, I doubt that it will last very long in its present condition, but tweaking/tuning will take care of that (I will have to scale it down a little power-wise).
My XSOZ runs at the same railvoltage, but my regulators eats about 6v, so I have a little more heat to dissipate than you.
Yes I know some people donīt like to use fans, but in my oppinion it is not a big deal, I have had an SOZ and XSOZ running with fans for more tan 3 years now, it dosenīt bother me at all. But you need to use some silent fans. I ended up with 4 x 220V slimline sleevebearing fans, 2 X 2 in parallel to reduce the airflow and the noice, and this is verry effectieve. You have to start the fans non paralleled in order to start the up, and then couple them in paralleled mode.
I can touch my heatsinks, i guess they are 50*C for the mosfetsinks and 60*C for the resistorsinks.

My fans measures 120 x 120 x 25 mm.

I also build my first XSOZ with the rectifires mounted at the same plate as the PSU-caps, but now i have mounted them at the mosfetsinks.

I have had an SOZ with only 15V rails, that were not enough for my 15 Ohm 90db speakers, i missed some headroom at the higer volume.

You have done a vonderful job, real nice, and i sincerely hope you will find a cure for this hot darling, one way or the other.

I have attached a pic of my fans.

Regards Henrik
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Old 25th January 2004, 02:28 PM   #25
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Default A more sober statement

After nearly 9 hours of listening to the XSOZ last night, here's my highly subjective opinion of what this thing sounds like:

The sound of the XSOZ is just amazing. First of all, it's bass control is a lot better than that of the SOZ. The crisp, sharp treble of the SOZ seems a bit damped, but the depth is still there. Still, I can't help but miss the mid-range sound of the GC. The details are certainly there, but they seem to fall a bit down in the back.

In total, the depth and width of the total soundstage is the best thing I've heard. The resolution is amazing. Neil Young sat in front of us playing Heart of Gold, Dire Straits played the guitar on the MTV like never before, and Pink Floyd never sounded that good. The division bell was everywhere. The wall was coming down. The experience is better than anything else I've heard.

This is high fidelity, and I'd sure like it to come to my livingroom as well.
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Old 25th January 2004, 02:50 PM   #26
Mad_K is offline Mad_K  Norway
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Thanks for the nice words, and I really appreciate your suggestions Henrik

I am sitting here contemplating my options on how to get the temps down.. I thought I was going to get away without using fans, but it seems that was just a nice dream..

-How do you power your fans? separate supply or regulated from the main rails?
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Old 25th January 2004, 03:09 PM   #27
Henrik is offline Henrik  Denmark
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Hi again.

My fans are running at 220V AC.
Once I tried 12VDC ballbearing fans, but they made too much nocie, and i ran the from a separate supply. Sleevebearing seems to make less nocie than ballbearing.

And donīt use fans at 120 x 120 x 50mm if you can avoid that.

As I see your heatsinks, they have pretty deep fins, which makes them more effective than mine.
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Old 25th January 2004, 04:38 PM   #28
moe29 is offline moe29  United States
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the bypass cap is a neat idea... hadn't thought of that.

thanks for posting the closeups of the FETS... i was really interested
to see if what i had done looked anything like what someone
who knows what they're doing did!

i take it the blue material is a dampening device? to keep the
capacitors from just hanging there? What is that stuff? I think i'd
like to try that on my amp.

i like the symmetry that your amp has on each channel...
PassLabs makes a point of that in their X amps.

it's really cool to see some more X-SOZ's being made. More of you
should try building this wonderful amp, you won't be let down!!
(as long as your speakers are up to it!)

((FirstWatt dare not make an X-SOZ... it may eat into the sales of the real stuff!!)) ha ha
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Old 25th January 2004, 05:19 PM   #29
Henrik is offline Henrik  Denmark
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In post #24 i wrote:

"I ended up with 4 x 220V slimline sleevebearing fans, 2 X 2 in parallel to reduce the airflow and the noice, and this is verry effectieve. You have to start the fans non paralleled in order to start the up, and then couple them in paralleled mode"

It shoud have ben:
I ended up with 4 x 220V slimline sleevebearing fans, 2 X 2 in series to reduce the airflow and the noice, and this is verry effectieve. You have to start all the fans in parallel in order to start them up, and then couple them in 2 x 2 serial mode.

Like in the scematic in post #27

Sorry for the confusion.
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Old 25th January 2004, 05:42 PM   #30
Mad_K is offline Mad_K  Norway
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-You're welcome moe29!

The "blue stuff" is called Blue-Tac and is primarily used to damp vibrations, but it also helps in keeping them in place. It is made for hanging posters on walls, but also makes a very good dampening material.

I understood what you meant Henrik Thanks for the info. I'm curious; what's the reason for your pseudo ground psu?

I think I will just bite the bullet and order a new trafo; they're not that expensive (as opposed to the amp blowing up my $3000 speakers). This will degrade the power rating to about 5W per channel. I have lots of heatsinks and another trafo just like the one I have currently installed that I can use later for making even more powerful XSOZ monoblocks (~15W).
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