good simple SE circuit please

[James D.]

The 300B is a hugely overrated tube IMO/IME.

I have to agree with Brett. Unless you really must use a 300B, it is better to get neutral performance using something else.

I like 845 at low to medium voltage to get 300B type power output. A matched pair of 845s is available from JacMusic at around 70 euros the pair...

If you don't need a lot of power then an ECL/PCL82 or 86 in triode mode takes a hell of a lot of beating. My one has seen off four different 300B amplifiers and a couple of 2A3 ones too. My 2A3 IT PP beats it but my 845 doesn't - it just about equals it... You can make a world class SE amp for £100:00 a side with this valve.

ciao

James

[AKSA]

I have listened to perhaps four 300B SE amplifiers, and only one really impressed me, and even then it lacked the engagement I hear with the 211 and the 845 (my preferred output triode).

However, on basis of reports alone - I've not heard them yet - I believe the 813 in triode mode, championed in Britain by Paul Le Clerq, and the SV811-3 from Svetlana (described by Bob Danielak in NJ) are amongst the best SE tubes around. I have two of the latter, no longer available, and will one day build it, but it certainly looks the part, VERY pretty.

One further point; it is not just the output tube one is hearing - the driver is pivotal in the sound. I really like triode strapped EL84s and the indirectly heated 6BX7, used in the Cary 805. Excellent driver.

Cheers,

Hugh

[Paul Barker]

I've used the 813 triode connected. Though ti does do what it does very forcefully and this is very seductive, when you build a 211 amp you realise the 813 is massively coloured and coarse. Yes it sounds very nice indeed, as do old paper in oil coupling caps. Yes it's a greta way to tune in a sound you happen to find uphoric, but as linear as the 211 it is not.

[Raj1]

Hi Hugh and Paul,

Do you have any links for good 845 and 245 se amps? Hugh I think you've just hit the magic sound word - 'engagement', that's what I'm after........
I've done a search and have found a few, Paul I know you're a fan and have experience with various SET's, can you reccommend a design?

Thanks
Raja

[Paul Barker]

Hi Raj.

I don't actually look at what circuits are about on the web these days, so I'm not up to date on what's available, but I'll follow the thread and comment if you find any.

Generally a single ended amp design is about mixing compromises to suit your pocket and margin of safety required.

I wouldn't recommend my style of building to anyone. One mistake and your dead.

Thinking back to when I used more sensible voltages, a very good sound can be made quite cheaply and relatively safely.

For instance a SV811-10 design of Eric Barbour's. I long since lost the article, someone could maybe find it for you. 6EM7 voltage amp direct coupled to 6em7 cathode follower cap coupled to SV811-10, which is operated at 0v bias 500v anode, or there abouts. With the added complexity of a plus and minus dedicated supply to the driver this could be altered to 6em7 voltage amp cap coupled to 6em7 cathode follower direct coupled to SV811-10. A better topology but slightly more complexed and level of difficulty, but a good learning experience.

I have to go now, more ideas later if you want.

[Raj1]

Hi paul,

searched the web and found this,

http://www.geocities.com/bobdanielak/se_sv811.html

what do you think?

Thanks
Raja

[Paul Barker]

yes Bob's stuff is all good.

Strange he needs so much voltage amplification.

You can follow Bob's schematic exactly or you can take out the 6sn7 stage with no other changes. Each way would work and you have the benefit that someone else has done the graft for you.

[Mohan Varkey]

We are only a few kilometeres apart and do we have to go right around the world to say hello!! Thanks Hugh and nice to hear from you again and watch you in action. I shall call you later this week for a chat.

Mohan

[navin]

raja you said you want 90 db at 1m? 2m?

I find 90db at 1m will really only be about 85db at 2m. normally i am about 3-4m away from my speakers.

my speakers are 87db. i am lookng at 95db at 2m. so i get about 90db at 4m.

how much power would i need. 25W? anyone know a 845 SE ckt that can do this. any other alternatives.

[navin]

how about 3-4 EL34 in parallel