The Doddington Special

[andrew ivimey]

Just another little amp, casually thrown together, experimented with and now swimming along in the great mysterious sea of sound.

Nine chokes, three transformers and precious little else to go wrong. I started with silicon rectifiers but couldn't resist valves; 6D22S from the steppes of the Urals. All for a few pleasant watts.

[acorn]

Thats a bit of a Steam train one you have there Andrew, were do you get the time to make so many interesting projects , it takes me weeks to think about them then some thing more pressing comes up and it goes on the back burner for another day, Ah well I will have to disapline my self a bit more and neglect the garden for a moment.

Cheers Acorn

[andrew ivimey]

1. I get the bits - except one or two essentials.

2. I spend a month thinking about what goes where and how.

3. I do it in a couple of hours, hence the bleeding is often part of the drilling, filing, cutting, spraying, screwing and soldering. This is when I remember the missing essentials. -> bodging

4. They always work (I am getting blase about this) but they don't always work too well.

5. Mods - this can take a lot of time, sweat, stress etc.

This one really is very promising indeed.

James Doddington gave out this circuit, minus PSU and I don't think anyone else has tried it (yet). I had some anode chokes that I'd bought in Hongkers for a few dollars each. They aren't quite the specc'd values but I have never let that sort of thing worry me. (I could see that it would work) I started with solid state rectumfires just to be able to switch on quickly. These valve jobbies really make a lovely difference and the amplifier is settling into something 'not bad at all, actually'.

Solen coupling cap though (and some see this as the devil's spawn) due to size and space but crimminy! though my preferred cap for such is the outstanding Mundorff supreme, the solen ain't bad.

I've spent most of the day going through lots of music (always a good sign) and using two pairs of very different speakers.

OTOH I do have a 'few' amplifiers on the shelf even though I do recycle lots too.

I have already begun some serious exploring of push pull amps (having run them down for years) and that could be a whole new thread. One quick for instance though was having the chance to acquire, for a song, a Music Angle EL34 jobbie that lasted a few hours before recycling (I am not kidding. It was loud - it was ****) and a KT88 Music Angle that isn't bad at all (valve rectums to boot). I will be comparing it directly next weekend with WDKT88. I expect to be the honourable loser in the contest, but we'll see.

[IslandPink]

6D22S's , sorted, respect due
( as Stufa might say )
Sounds good then ?
What discs does it show really well with , so far ?

Mark

[The Shadow]

Hey Andrew

You're getting all neat and tidy these days
First the copper OTL and now this fine example
of industrial chic

Steve

[andrew ivimey]

Witham can decide whether or not it sounds good.

I think it is worth moving onto Blackgates in the PSU (there is only a cheapie 200mfd at the mo' yuk; choke loaded is good.)

My friend up the road has loaned me a couple of booteek coupling caps small enough, I hope to squeeze in.

I need 1mfd at no more than 200volts at the very most but all I have are far too big!

An example. I love Siegfried's Death march (Wagner, Gotterdammerng). All minor chords brass and bombast with a great deal of pathos too, provided by strings and woodwinds. But I'd never heard all the twinkling harps in the background, before. This amp is very detailed and reveals los of quiet stuff while teh big guns are blasting away. It may not be quite right yet but ...

A DVDaudio of Daniel Barenboim at his worst doing Ludwig van's no9. The amp shows all that is wrong with the performance and okay Dan B. pulls it together for the fourth movement and so it draws me in and I makes listen and listen good. Male vocals are lovely.

I have been through a pile of rock CDs and tried two very different kinds of speakers.

This amp is worth it.

I doubt that the blackgates will be worn in by Witham. That's an excuse!

But it is worth going the extra mile.

Actually the 6D22s are very easy even though the cathode is the top cap, ... that made me slow down and have a 'senior moment'. I would have used RG1-250s because they are truly beautiful (who cares what the amp sounds like - a small price to pay for beauty) but there is no room for and extra 2-0-2transformer (and I haven't got one, though a Hammond, suitably tailored will do in a future project)

James D said this was his favourite amp. My cheap imitation is 'getting there'.

[andrew ivimey]

Oh and Steve, it isn't as neat as it looks in the pic!

She who must be obeyed has just called my special, 'stodgy!'

I can't cope with that. :-(

[Ianm2]

looks great andrew, you do the most interesting things

what's the output iron? any good?

and what's the one valve to rule them all? 211?

[andrew ivimey]

AE twin C core, so not bad.

VT4C would be my choice!

here's a larff though, old Jehovah 'avin' a go. My 300B amp has conked out. There is no apparent reason and the voltages I have measured so far are in the right area for playing baseball. I checked the caps and they seem right but something fishy is going on at the input stage (I think(causing horrible whictling, motorboating and general hum - with no signal at all) six months ago this was a fine amp. Now it has thick dust and a distressed owner.