WORLD DESIGNS VALVE AMP WANTED

[Mike H]

I'm obviously looking at different listings!

[SimonC]

Didn't Simon C have the 6550 version?

KEL 84 is 15W per channel, should be loud enough in a living room?

Sorry for the delay, I've only just caught up with this thread.

My WAD amp is not a 6550, its a mk1 5881 with a few tweaks (fast diodes, poly-something feedback caps, a few other cap upgrades - nothing mega expensive though, and some sovtek 5881's). Classic WAD P-P sound, doesn't quite match the 300b P-P for out and out dynamics, buts its surprisingly close for the money. It pushes out an honest 20W per channel and is not that fussy about the speaker loading.

The only downside is that the input sensitivity is too high if you have anything that pushes out over about 0.5v, even running a passive pre-amp it takes some taming. I've been meaning for years to convert it to a triode first stage to knock the sensitivity down to something more manageable, might even add a bit of triode character to the sound, but on the other hand it may sound crap. Only one way to find out....

You don't see many WAD 5881's for sale anymore though, but if you do its worth giving it a good listen.

Simon C

[IslandPink]

It is a good amp - I heard one years ago, Dave Dove ( Elson ) on our board had one.
If we could see the circuit it would probably be possible to reduce the gain without upsetting the circuit layout too much . I'm assuming it's some sort of pentode gain ( EF86 ? ) stage if you are talking about 'converting it to triode' - so maybe another noval pentode with slightly different resistors may be all it takes.

[Mike H]

It is a good amp - I heard one years ago, Dave Dove ( Elson ) on our board had one.
If we could see the circuit it would probably be possible to reduce the gain without upsetting the circuit layout too much .

I was thinking that, simply reduce the feedback ratio?

[IslandPink]

MIke -you know that discussion about talking bollock about things you don't know about ? - I just went looking for the circuit and found old WD threads where people ( including Dave Dove ) were saying the amp as a whole was a bit 'unfocused' and the driver stage was 'pants'

I think I'll get me coat .....

[Neal]

The EF86 fronted one was ok on sensitivity it was when they went to the SRPP input on the MkII that things went boobs up...

[SimonC]

MIke -you know that discussion about talking bollock about things you don't know about ? - I just went looking for the circuit and found old WD threads where people ( including Dave Dove ) were saying the amp as a whole was a bit 'unfocused' and the driver stage was 'pants'
I think I'll get me coat .....

I'd agree with Neil that the driver stage for the MkII was pants, the SRPP was brutal. Mine is the classic MkI EF86 - ECC83 combo, much nicer to my ears after the brief listen I had to a MkII.
We did a back to back with either Nick's 300b or t'other Simon's 2A3 at the end of the last SimonFest (can't remember which amp as it was a good while back). Surprisingly close results, it definitely has P-P character but I would have not said 'unfocused' or 'pants' by any stretch of the imagination.

Sorry about the tweaking plans, I was typing my thoughts in a rush. I meant to say I want to triode strap the output stage for starters to get the overall gain down to something more manageable. Pretty quick and easy to do, but getting my head into the feedback calcs is whats holding me back to be honest. I know its only a couple of hours with MJ to get it done, just finding the time and motivation in among all the other things needing to be done around the house.
If that didn't help things then I'd look at the input stage. I've always wanted to do a multistage triode driver with a concertina phase splitter. No reason, just like the elegance of the concertina design. It just looks right...

Sorry about the thread hijack Adamski

Simon C

[simon]

We did a back to back with either Nick's 300b or t'other Simon's 2A3 at the end of the last SimonFest (can't remember which amp as it was a good while back). Surprisingly close results, it definitely has P-P character but I would have not said 'unfocused' or 'pants' by any stretch of the imagination.

Goodness me that takes me back! I had a look back at an old defunct place I no longer have control of, but I wonder if it was Dave's 2A3 amp? Nearly 7 years ago now. And Madness still isn't in a box.
http://www.atrj13.dsl.pipex.com/na-meet-SimonC.htm

[dave dove]

going to bump this thread
i didn't have a 2a3 but a nice 300B
my k5881 was a 5881 pse - parallel single ended - 17wpc
and the driver stage was pants - can't even remember what it was
i tricked it out with an Aikido driver stage - night and day
is for sale now - i have a different life and i can't see to solder anymore
sounds bloody good but won't drive my ATCs

dave

[simon]

i can't see to solder anymore

That really sucks dave. You were a stalwart on the old WAD board and I always read your posts with interest. Missing your 300B amp with pentode Aikido that James D helped design is one of the audio regrets I have.

[Mike H]

Bum.

[Adamski70]

no longer looking WAD 300b pp souning fab in th eliding room
cheers