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PostPosted: 10 Nov 2010, 18:53 
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Hi forum

Time for something different.

For a long time, i've wanted to build something up around 12 Mos-Fet's, i've got ...6 per channel ( 2SJ50/SK135 Hitachi ) already mounted, in a large enclosure with big heatsinks. Both enclosure and heatsinks comes from a junked UPS and i find it suitable for making a Class A/B amp out of it. Primary use for the low octaves ( drive two sub's ), with simple active/passive filtering for the input. :wizard:

Alternative, if it's easy to add a few components, to get it running in Class A, offcourse it also could be fun. :mrgreen:

It goes like this:

Image

More inspiration:

Image

Image

Image

I'll add some pictures of my build soon.

( please feel free to add comments and ideas of yours ). :thumbsup:

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PostPosted: 19 Nov 2010, 02:34 
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Hey John,

the first one, coupled with an OPA2134 as input would be nice ;-).

50Volts is a lot... 18VDC +/- would fit the bill, including the OPA.

Only my :2c:.

Have fun!

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Some of my projects: TDA2050 Chip Amp, the LM3886 Gainclone Thread and the Szekeres Headamp Thread.


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PostPosted: 21 Nov 2010, 14:47 
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tombethe wrote:
the first one, coupled with an OPA2134 as input would be nice ;-).

50Volts is a lot... 18VDC +/- would fit the bill, including the OPA.

Ho tombethe

Yep, 18 VDC +/- will do it ! :wizard:

I've got some OPA134, to be used for this purpose.

I would like to see schematics ...has anyone something related ?

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PostPosted: 24 Nov 2010, 13:24 
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I assume you mean circuits for the opamp.

Take a look at the Rod Elliot High Quality Audio Preamp (Mk II): http://sound.westhost.com/project88.htm

That will work with the opamps. Check the datasheet as 18V may be near the max for the opamp.

Cheers

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[ DIY Mains AC Power Cable Cord ] - [ Gobo LM1875 Amp Kit ] - [ Tang Band D4-1 Horn Speaker Kit ] - [ Monoblock Push-Pull KT88 Tube Amp Kit ]


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PostPosted: 02 Nov 2012, 14:01 
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Hallo mr Danish man, what happened then?

I have been checking the various shops att AliExpress and have purchased some items, mainly for Mrs K, but also two pairs of the SJ50/SK135 (did I get the figures right?) just on an impuls but also had an idea to look for a suitable hybridamp to clone.
In the Elektor Electronics Sept 97, is a hybrid amp with different transistors (2SK175/176 and 2SJ55/56 described. However EE have managed to screw things up and some vital info is missing like a component list for main PSU, which also includes turn-on-delays. Also are missing the FULL set-up procedure, but never the less, parts of the amps are worth looking into.
I enclose pics of diagrams:
http://www.pastisch.se/EF/EE_9709_hyb_1.jpg
http://www.pastisch.se/EF/EE_9709_hyb_2.jpg
http://www.pastisch.se/EF/EE_9709_hyb_3.jpg
http://www.pastisch.se/EF/EE_9709_hyb_4.jpg

My idea was to use my Chinese complementary pairs, but look into a C3g-driver as I loathe SRPPs. Guess the German Post tube can deliver enough for the FETs.

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“If you don't know where you are going, any road will get you there.”
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PostPosted: 14 Dec 2012, 17:09 
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Heja Swede

Magnus, sorry about the late reply ...i'm not spending much time with electronics, at the time. I've been into bushcrafting for a while ...which satisfies me very much.

Anyway ..maybe you remember the danish construction MosTube BR398 from Brinck (?) ...it was a very good sounding hybrid. I've heard it, but never owned one. The link of the hybrid shown http://www.pastisch.se/EF/EE_9709_hyb_2.jpg, looks a bit like another mosfet construction BR392, i've got from Brinck ( built into an AKAI amp enclosure ). Different is Q1, which is a FET in my amplifier. It's possible to adjust both DC offset and bias. Powersupply is +/- 70 VDC ( 2 x 50 VAC 500 VA trafo ), 2 x 25000 uF Sprague caps and it's biased by me, to 200 mA pr. channel ( manufacturer says 100 mA ). It runs very hot ...but thanks to the 2SJ50/2SK135 thermal built-in regulation, it actually works fine and detailed.

I've got 12 more of those babies from Hitachi ( never been used ) ...mounted on large heatsinks. What a waste of good mosfets ...well, some day in the future, i hope to bring them life. 8-)

Some old pictures:
Image

Image

Image

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PostPosted: 15 Dec 2012, 04:03 
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Dear Verdens mest tilfreds mand,

Thanks for your answer. This is first time I see the MosTube and I will look deep into the design and see how I can adopt it to my needs. I only got two of each SJ/50/SK135, and I don't need full 100W.
One thing that strikes me is that many (old) designs from Elektor, ETI etc looks very complicated, whereas there are simple designs for Aikido drivers. Reading the descriptions to tehse complicated designs it they seem so very reasonable, why do the Aikido designs look so simple then??
I will definitely look into this and try to find a solution with tube driver. I have 1 1/2 transistor amp in the project basket already and don't need one more, especielly not one more in pieces.
If you're interested, by the way, we are planning for a DIY/Triode-fest here in Vänersborg, Sweden around 11-12 May next year.

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“If you don't know where you are going, any road will get you there.”
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PostPosted: 15 Dec 2012, 06:09 
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Soundbrigade wrote:
Dear Verdens mest tilfreds mand,

Thanks for your answer. This is first time I see the MosTube and I will look deep into the design and see how I can adopt it to my needs. I only got two of each SJ/50/SK135, and I don't need full 100W.


Hi Magnus, snälla nabo :D

Yep, it will work absolute fine with only four transistors instead of eight. No need for so much effect.
Note: I've heard that people are wanting/searching for Hitachi's mosfets ...because they were convicted that copies not sounds very well ( i don't know if that is right ).

Quote:
One thing that strikes me is that many (old) designs from Elektor, ETI etc looks very complicated, whereas there are simple designs for Aikido drivers. Reading the descriptions to tehse complicated designs it they seem so very reasonable, why do the Aikido designs look so simple then??


You're right, i've often been thinking the same. You can put a lot of components together and measure nice curves ...but that doesn't mean it's good to listen. Often simplicity sounds great, but doesn't have the nicest curves. I would always go for simplicity. The Aikido as you mentioned is a good example of that.

Quote:
I will definitely look into this and try to find a solution with tube driver. I have 1 1/2 transistor amp in the project basket already and don't need one more, especielly not one more in pieces.


I know that problem ...i guess thats why my projects never being finished. I think i've got at least 10 half/unfinished projects laying around ( sorry, i hate myself for that ). :bawling:

Quote:
If you're interested, by the way, we are planning for a DIY/Triode-fest here in Vänersborg, Sweden around 11-12 May next year.


Sounds great, thanks ...i'll remember that. :up: When searching for Vänersborg i've found that Trollhättan is near by. Trollhättan, which has been my favorite place for many years ... i love to come there on vacation year after year, alone or with my oldest son. I/we always finding peace and relaxation in Sweden. ;)

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PostPosted: 15 Dec 2012, 08:02 
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More about the DIY-fest here: http://www.diyaudio.com/forums/clubs-events/225332-diy-triode-fest-west-sweden-may-2013-a.html.
Would be great if you could come. Trollhättan is just 15km away.

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“If you don't know where you are going, any road will get you there.”
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PostPosted: 15 Dec 2012, 20:29 
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Soundbrigade wrote:
More about the DIY-fest here: http://www.diyaudio.com/forums/clubs-events/225332-diy-triode-fest-west-sweden-may-2013-a.html.
Would be great if you could come. Trollhättan is just 15km away.

Is this any any way related to triode fest? - Sorry very OT.

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