Mullard 3-3 information required
 

How many Forum members are there with a Mullard 3-3 amplifier?
I wonder if if there are any who have made their amplifier in recent years.
Can you still get a kit of parts to assemble yourself?

I have seen the period adverts in Practical Wireless from the fifties & I have looked at them closely to find mention of the wound components.
Fortunately there is a constructional guide here: http://www.r-type.org/static/3-3.htm

That guide mentions several makers of transformers who had output transformers for a EL84. I don't know if the 3-3 circuit must have a really high quality output transformer and a good power transformer too.
Those original makers aren't in business today, apart from Partridge.
I see there are other people like Sowter & VVT who make transformers.
Who bought new & who re-used old transformers?

I would like your comments, please.

Re: Mullard 3-3 information required
 

Hello Neil,

my 3-3 uses a Partridge Power Transformer and Output Transformers from a Grundig unit of some description. The seller did not specify other than that they were specifically for the EL84.

Apart from the Casework, Socketry, Volume Control, I/P Switch and Wiring all components were second hand of varying vintage.

I have purchased from VVT for another Amp I made based around the 3-3 circuit but 'tweaked' to take the EL33 as the O/p Valve.
The Transformers for this Amp (O/P and Mains) were all from VVT and perform very well. I can recommend the company very highly. I had quite a few technical questions which I asked via email. Many were answered in the evenings and at weekends by a very helpful Gentleman (David).

I take it you are about to start upon constructing a 3-3? I hope it goes well, you will not be disappointed. Please keep us posted on your progress.

Kind regards,

James.

Re: Mullard 3-3 information required
 

How about https://www.vintage-radio.net/forum/...ht=mullard+3+3

And a PM has been sent.

Re: Mullard 3-3 information required
 

Here's one I started to build a year or so ago just for a laugh on a baking tin that was lying about. Many of the components came from the audio section of some old radio that I used to use with a crystal mic as a general purpose shack amplifier and tone controlled Heising modulator for a 5watt 80 mtr transmitter.

The transformer I had in mind was tall and narrow and just fitted nicely in the available space. Unfortunately it had a shorted turn so never got fitted. That little one you see in use does work quite well but won't fit so I'm still on the hunt for a tall thin output transformer. Of course if I'd used a tall thin mains tX there'd have been plenty of room, which tells you of course even if you make something from junk make sure the junk fits first.

Jim

Re: Mullard 3-3 information required
 

Just for fun, I also built one of these on a scrap chassis using all scrap parts. I used an old radio chassis that already had the mains transformer and EZ80 mounted. The original EL84 output transformer was also used. It works although the hum level is higher than it should be and clearly the output transformer is struggling to cope with bass. The quality is surprisingly good and only distorts badly towards full volume clearly because the small output transformer cannot cope.

If you are serious about building one, you need to use a good output transformer and you won't be disappointed with the results.


Rich.

Re: Mullard 3-3 information required
 

Hi There,

I have a pair of EL84 output transformers salvaged from an Armstrong stereo amplifier which I have no need for, which may be of use if nothing else purpose made comes to light. The size is 2 ¼ x 1 x 2" so there is a decent amount of iron in them so they should be ok at LF.

I also have the instructions for the Sterns 3-3 kit, which I can scan and post if it’s of interest. Also from memory one of the Caxton Radio servicing books (can’t remember which volume) had a page or two on the 3-3 amplifier circuit.

I have a Sterns 3-3 amplifier and I have to agree it does sound rather nice. I did find to get the best I had to use good EF86 and EL84’s. The Sterns 3-3 kit was very popular along with the 5-10 kit.

Regards
Terry.

Re: Mullard 3-3 information required
 

Sideband:What o/p transformer were you using?
I have one, but it has a secondary for 4 ohms. It's by JB Electronics: Who were they? Definately not in the league of Parmeko, never mind Partridge!
Was the Parmeko o/p transformer the one you see that is very tall, while having quite a small 'footprint' on the chassis?
If it is that one, quite a few used it or a facsimile of it. I suppose that other makers might have made something with the same 'footprint', but it was a small space to fit a transformer on.

Re: Mullard 3-3 information required
 

You can get replacement chassis for various Marshall & amps on-line.
They are not pre-punched with control & valve holes.
The effort depicted in the photograph was made with such a chassis.
Can I re-cycle it? The present output transformer suits a 6V6 to 8 a ohm speaker. New o/p transformer? The power transformer seems to be capable.
I am just worried about lengths of wires, so punching new holes for the Noval valve-holders might be a better idea rather and disguise the old holes with aluminium plate cut & shaped.

Re: Mullard 3-3 information required
 

It was the orginal output transformer fitted to the scrap radio. The only thing it had going for it was the fact that it designed for an EL84. It was just a small Philips output transformer covered in pitch (I think from a B3G63A). Not enough ironwork or copper to work well with a 3-3 design!



Rich.

Re: Mullard 3-3 information required
 

Is a output transformer of inadequate dimensions going to struggle with bass-heavy passages at any volume or just when turned up?

Re: Mullard 3-3 information required
 

Bit of both, with enough negative feedaback (as the 3 3 has) it will be OK until things limit after that it will get worse.

Re: Mullard 3-3 information required
 

This is a related question. In this topic a Member mentioned some EL84 transformers & I am interested in them. They have a Secondary with tags for 4 & 16 ohms, not 8. Thing is; my speakers are all 8 ohms excepting a 5" Celestion salvaged from a Pye Portable.
The transformers are meaty enough. Wondering about the mis-match on the output to the speakers though.

Re: Mullard 3-3 information required
 

Hi Neil, If you use an 8 ohm speaker on the 4 ohm tap there will be a reduction in max power and a small increase in distortion, The other way round (8R on 16R) will also work, but probably a slightly greater increase in distortion.
Neither connection will damage the amp.

Ed

Re: Mullard 3-3 information required
 

Thank you for the information Ed.

Re: Mullard 3-3 information required
 

Hi,

I run mine with the 4 Ohm tap and they drive a pair of 8 Ohm KEF 3 way speakers ok, all right if you wind the wick right up on something like Led Zeppelin they do struggle a bit!

Terry.

Re: Mullard 3-3 information required
 

Here's mine.
Built on a home-made aluminium chassis, using tag boards and whatever components I had to hand. The EM84 is just a bit of fun and moves in time to the audio output level.

It uses the VVT stereo 3-3 transformer set and acquits itself reasonably well. As said previously, it runs out of steam pretty quickly in the bass department, especially when using big speakers, e.g. 3-way KEF Q65.2 floor standers.

Still, a highly recommended construction project though.

Steve.

Re: Mullard 3-3 information required
 

Steve, nice amp. but you should put that fan closer ;)

I used VVT-iron throughout a 2C34 push-pull AB2 amp that I made some time ago and they sound really good. Not the cheapest iron around but performance is tops.

rgds,

/tri-comp

Re: Mullard 3-3 information required
 

That's a lovely picture of your Mullard 3-3 Steve.
What are the dimensions of the chassis top?
My present finances do not allow me to buy an o/p transformer brand new, so I have taken up Valvepower's offer & I will be recycling a transformer. Thanks Terry.
I have seen plenty of adverts by Sterns for their 3-3 kit in Practical Wireless.
This would be of interest here I think.

Re: Mullard 3-3 information required
 

Hi,

I believe the transformers I’m offering Neil could have been made by Hinchley in the 1950’s as these transformers have the same 4 number identification code used by Hinchley on the Leak and Rogers transformers – it’s a long shot but it’s likely.

I’ll dig out the Sterns info and scan it and post it on the forum next week.

Regards
Terry.

Re: Mullard 3-3 information required
 

Chassis is 308 x 140mm and is 45mm high.