Building a Sun Audio sv 300b Mk II clone

[doug_olitsky]

Was hoping that there are some fellow audio hounds who have built a Sun Audio sv 300b Mk II and are willing to share the wealth (so to speak).

I would really love to see the kit plans, etc. I saw what meta gizmo had on it but for a newbie, it was not enough.

I have considered the JE Labs 300b, Angela 91, and the world audio 300b PSE to name a few.

However I think 8 watts is a bit lacking, since I dont have very efficient speakers Alon MkII's 86db also have Hersesy II. 96db

I was goning to give up on the idea and came across the Sun. And I think I found what I want to build. Powerful 300b, simple design.

Does anybody know the basis of this design, all I know is that it is supposedly a classic.

I'm into tubes, newbie to DYI, know my way around a soldering iron, and got the bug to build an amp.

I know from sun they are pricey and I was planning on specing a few different parts, as I dont want to empty the bank. Plus as a shop teacher in I want to do my own chassis. and even use them in my class for a while to show my students

Thanks for you kind indulgence, Merry Christmas

Doug Olitsky

doug_olitsky@yahoo.com

 

[Andrewbee]

sun audio 300B

is here
http://www.simpletube.com/databank/SingleEnded/300B_SE_6SN7_2.5K.jpg

For the motherlode go here

http://www.simpletube.com/databank/circuit_map.htm

Andrew

 

[audiousername]

The circuit posted previously was wrong, the Sun Audio SV300B MkII is a 300B Push-Pull circuit.

An externally hosted image should be here but it was not working when we last tested it.

However I think 8 watts is a bit lacking, since I dont have very efficient speakers Alon MkII's 86db also have Hersesy II. 96db

8 Watts may be enough for the Heresey IIs (will probably get you to 108dB at 1m)

I was goning to give up on the idea and came across the Sun. And I think I found what I want to build. Powerful 300b, simple design.

It's more powerful because it uses two 300Bs per channel in push-pull, a very different topology to the more common single ended topology (which gives out about 8-9W)

Does anybody know the basis of this design, all I know is that it is supposedly a classic.

I don't see anything groundbreaking. A 6SN7 (paralleled sections) driving an interstage transformer acting as phase splitter driving 300Bs in push pull (from the output power I would guess in class A). Of course that says nothing about its performance, only that there is nothing really that unusual (or interesting) about its workings.

EDIT: I checked the Sun Audio site and the amp actually operates in Class AB. Whoops.

I'm into tubes, newbie to DYI, know my way around a soldering iron, and got the bug to build an amp.

I would recommend you try something with other kinds of valves. The EL34 has many well established designs for it, and is in current production in Russia and a few other places (if that is important to you). If NOS (New Old Stock, i.e. being sitting in a warehouse for decades) is more your style, the 807 (and its many, many, derivatives/equivalents) are quite cheap and readily available since it has been generally overlooked as an audio output valve. If you're interested in other options, ask.

Many will claim this is heresy, since neither the EL34 or 807 are directly heated or true triodes (the EL34 is a pentode, the 807 a beam tetrode). However, both can be operated in triode mode, and are much cheaper, making them a better choice for a first project if you accidentally mess something up. Anyway I don't think all the valves I have cost anywhere near the amount a matched quartet of 300B would.

I'll probably get flamed for this but the 300B is boring. There are much more interesting, beautiful and cheaper valves out there to show your students!

I know from sun they are pricey and I was planning on specing a few different parts, as I dont want to empty the bank. Plus as a shop teacher in I want to do my own chassis. and even use them in my class for a while to show my students

It will always be pricey. You need FOUR 300Bs!

I don't mean to discourage you from building the Sun amp, but you should be aware of other options out there. If you need some more explanation of the Sun circuit, ask, and I'll try to help.

Merry Christmas to everyone

 

[Andrewbee]

Sun Audio 300B pp

Oops, sorry about that.
Audiousername has corrected me.
The 300b pp amp is what you are interested in. Well..... I built a "clone" a few years ago with Electraprint iron throughout, VAlve Art C60 300B's etc. Its okay but to my mind nothing special, but remember this is a clone and not the "real McCoy". The design is simple and how things were done in the days of old e.g. the interstage transformer.
I also tried different tubes in the front end such as the original 6SN7 in //, 5842, 6N1P // and something else but I do not remember now. My favorite was the 6N1P.
I also built the "Ralph Power" 2A3 pp which is very similar, which used 6B4G's (I used these and then 2A3's) the driver / output tube and filament setup being different.

I must confess that after building several DHT amps both pp and se using the more common 300B, 2A3 and 6B4G tubes I am not a DHT "fan". Sure they sound okay or "nice" but just not my cup of tea.
I find them to be too "smooth". If you are into vocals or jazz etc then they are great but I think they "gloss" over the music too much (flame suit is now on).

I seem to prefer tetrodes / pentodes especially the KT66 and EL84.
I presently have on the bench the beginnings of Allen Wright's PP1C
amp which uses triode connected EL34's and a differential front end
with a C.C.S. but I will be trying it in U.L. as well.

Audiousername has given some good advice I think, especially with regards to expense.
Why not try something like a Williamson circuit using EL34's or KT 88's? Lots of power there and lots of circuits as well.

I too have been thinking about the 807's as well but I have so many tubes now.
BTW, the 807's use a top cap where the high voltage lurks closest to idle / unaware fingers so if the kids in your class are young and inquisitive or you have young ones at home then I would stay away from it.
There is an equivalent tube without the top cap called
CV391 or 5B-255M.
Best of luck.
Andrew

 

[doug_olitsky]

sun audio sv 300b mk II

Thanks folks for all the great insight.

I have been looking at other options and I do realize the expense of the 300b's, however I WILL NOT be buying WE's and just looking a tubedepot real quick shows a matched pair for 179. Plus from what I gather they should last quite a long time.

Andrewbee- do you recall what spent building yours?

I was kinfd of looking for something different since I already have a McIntosh 2102 running eight KT-88's and a copland cta-505 running four 6550's and a Fisher 400 running 7868's ( which btw are availible again from EH). I never owned a real triode amp.

Plus from what I read this type of typology is not in vouge in the USA. COOL. I looked at the JE Labs 300b project an I would of been happy with it but at 8w I know my Alons would be pulling up to the buffet table!

Perhaps there are other DHT's I should consider? Ideas?

The other thing I liked about the Sun is that is a old, nothing special design, what I'm looking for, I like things that the next kid up the block dont have ;-)

Plus its time proven and I dont need the tube version of techno-geek, some of the schematics out there are wild.

My criteria are:

Its design is simple (less is more) Sun is quite simple

I want something around 20w

I need to be able to have assess to not only the schematic and parts list but the build documentation. I do want to build from scratch but I think having build plans would guide me on critical things like grounding planes, orientations etc.

I am open to ideas, I looked at kits but I want to have a bit more parts choosing freedom, and things like iron are pricey and maybe i could live w/ a Hammond choke here and there instead of a James or MagneQuest.

Lets keep this ball rolling I'm learning!!!!


Happy Christmas to all;
Doug

 

[Andrewbee]

I don't remember the cost but maybe ~US$1000.00 I just got home and took a look at them (I built monoblocks) and the opt's were not EP's but some I scrounged from a Fisher X-202C I think it was, it used 7591's as output tubes. I had posted a pic of them and i am going to try to post the link so at least you could see how I laid them out. They sit on a shelf collecting dust now. Soon (yeah right!) I will play with them again.

http://www.audiocircle.com/circles/...lery&file=index&include=view_album.php&page=1

Andrew

 

[audiousername]

Re: Sun Audio 300B pp

Audiousername has given some good advice I think, especially with regards to expense.
Why not try something like a Williamson circuit using EL34's or KT 88's? Lots of power there and lots of circuits as well.

I too have been thinking about the 807's as well but I have so many tubes now.
BTW, the 807's use a top cap where the high voltage lurks closest to idle / unaware fingers so if the kids in your class are young and inquisitive or you have young ones at home then I would stay away from it.
There is an equivalent tube without the top cap called
CV391 or 5B-255M.
Best of luck.
Andrew

Yep. The safety concerns about topcaps are probably part of the reason why almost every valve with a topcap is unpopular (and hence comparatively cheap). Sorry, I should have mentioned that.


Doug,

True DHT PP at 20W... hmm... You may be able to close to that with a parallel push pull arrangement of 2A3s in class A (or very heavily biased AB)

I have two articles from AWV Radiotronics in 1937 (yes, from 67 years ago), one describing a Class A PP circuit with 2A3s for 7W, and the other describing a Class AB PP circuit with 2A3s for 13.5W, both were kindly scanned in by David Crittle of Retrovox. Email me if you're interested.

There are probably other weird DHTs out there which I have never heard of which might satisfy what you're looking for though. As you probably can tell from my posts, I personally believe that DHTs are rather overrated, but if that's what you want, go for it!