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Old 5th December 2009, 12:03 PM   #1
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Default Sun Audio SV-300B MKII DIY

Hi All,

I do really like to get a pair of Sun audio SV-300B MKII, but have not enough money for that...(http://www2.big.or.jp/~sunaudio/sv/sv300bmk2_e.html)

Does anybody know where I can find any schematics to DIM (Do It Myself) ?

thanks,
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Old 5th December 2009, 05:14 PM   #2
kmtang is offline kmtang  Canada
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The Sun Audio 300B is very similar to the Audio Note one. Derek Walton's web site has very good information in building 300B SE amps which includes schedmatics, layout etc.

300B Mk1 Triode Amplifier


Johnny
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Old 5th December 2009, 05:36 PM   #3
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Hi Johnny,

Thanks for reply. But Sun audio SV 300B MKII has got a pair of 300B tubes.
It seems it isn't really the same no ?
I'm quite a newbie in tube amps...

I sew some schematics given by Dr Gizmo :
SUN AUDIO SCHEMATIC

But they seem quite unreadable...
Regards,
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Old 5th December 2009, 11:37 PM   #4
BHD is offline BHD  United States
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If you're using Windows, right click on the image and select "Save picture as..." then save in "My Pictures". You can then open it and blow it up and it then becomes more readable. Do the same for the layout drawing.

It really shouldn't be that hard to figure it out - its a pair of 300B's being run push-pull with an interstage transformer/phase splitter. Unless both triodes in the driver tube are being used in parallel I bet there's a significant step up in order to get a 6SN7 to drive two 300B's. Unless the interstage is something spectacular, its likely limiting bandwidth. Personally I think it'd be better to use an input transformer as a phase splitter, but what do I know?

The power supply is a bog standard "Pi" filtered full wave tube rectified supply.

Nothing exotic in this amplifier except maybe the transformers. The picture down below the schematic even gives you the parts values and layout.

If you can find out the specifics on the transformers you can build this amp. Run a simulation of a CLC power supply using Duncan's PSUD with the values listed and substitute values of chokes you can get your hands on until you get a power supply that you like.

Good luck!

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Old 6th December 2009, 12:34 AM   #5
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Quote:
Originally Posted by BHD View Post
If you're using Windows, right click on the image and select "Save picture as..." then save in "My Pictures". You can then open it and blow it up and it then becomes more readable.
Or on a Mac drag the picture onto PhotoSHop

dave
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File Type: gif sunschematic300B-PP.gif (56.2 KB, 580 views)
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Old 6th December 2009, 12:49 AM   #6
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That looks much better. You can see that they're definitely using both sections of the 6SN7 in parallel to drive the 300B's.

Dave, what do you think the phase splitter transformer ratio is? 1/1+1 or higher?

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Old 6th December 2009, 07:10 AM   #7
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It is definitely a step-up transformer, probably a 1:2+2. The 6SN7 is simply a very poor choice in this position and makes the requirements for the transformer rather extreme.
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Old 6th December 2009, 07:24 AM   #8
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Thanks all for reply,

The fact is Dr Gizmo put this simple mono PP 300B to heaven in terms of timbres and musicality.
The fact is that I'm a newbie (I'll be able sold or screw or cut or anything else...) without much money.
I do know good transfos are expensive, good capacitors also and tubes (good 300B) too.
But on sun audio's website they sell the pair of these MKII at 888000 Yen(kit). That is nearly 10.000 USD.
Then, I though I could, with good schematics, and some tools and some (a lot of) work achieve some thing that can make good sound around the third of this price.(As a newbie I'd need clear schematics).

Now I feel like it is strange : If this mono amp is so good then why there is no literrature about it but on Dr gizmo website ?
If sold in kit, a detailed schematics should exists, then why are there any good plan ?
Here is Dr gizmo article about this amp :
THE SUN RISES IN AMERICA©

Regards,
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Old 6th December 2009, 09:31 AM   #9
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Originally Posted by blackjack2 View Post
If this mono amp is so good then why there is no literrature about it but on Dr gizmo website ?

Some time ago i had the opportunity to buy a pair of these really cheap. I checked all opinions on-line and some were less enthusiastic. What really discouraged me was the non-standard Tamura iron and especially the outputs with no 4ohm taps. This is certainly not an issue with a clone. You may find though that getting a 1:2+2 interstage is quite difficult.

A few years ago i built a very similar topology using 2A3, a Lundahl 1660 for splitting an 83 for rectification and a 6S45Pi driver. The circuit is somehere at diyaudio. It was a very nice amp. The 1660 is far from ideal for splitting phase and unloaded rings like crazy. Took me a while to find a suitable snubber for the secondaries which killed the ringing but still let it sound ok. Apparently the Tamura splitter also requires loading.
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Old 6th December 2009, 02:04 PM   #10
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I like to agree with analog-se
Had a Friend around to listen to my PSE300B Amp
Design my one i design all TX and wound Them,
he could not belief overall very nice Sound next Time
he brought his Wife to listen 6 Weeks later he told me
i got a Sun 300B he brought it around we was a bit disappointed
last Ding i know he is selling it.
My design 5842-interstage TX 5k-fixed Bias-300B 380V 150mA
Rudi
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