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Old 19th Mar 2012, 9:12 pm   #21
Valvepower
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Default Re: Mullard 3-3 information required

Hi,

I've up loaded the scans of the Sterns 3-3 amplifier assembly manual.

Terry

Quote:
Originally Posted by Neil Purling View Post
I have seen plenty of adverts by Sterns for their 3-3 kit in Practical Wireless.
This would be of interest here I think.
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File Type: pdf Sterns_3_3_CCT.pdf (181.9 KB, 120 views)
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Old 20th Mar 2012, 2:04 pm   #22
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Default Re: Mullard 3-3 information required

Hi,

I've up loaded more scans of the Mullard 3-3 amplifier from The Radio Constructor magazine and the Caxton Radio and TV book.

The Caxton book describes the DC conditions of circuit.

Terry
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File Type: pdf 3_3_RC.pdf (1.02 MB, 105 views)
File Type: pdf 3_3_Caxton_Book.pdf (686.2 KB, 98 views)

Last edited by Valvepower; 20th Mar 2012 at 2:08 pm. Reason: Add PDF Copy of Caxton Book
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Old 21st Mar 2012, 8:10 pm   #23
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Default Re: Mullard 3-3 information required

The circuit referred to in post #1 is the Mullard prototype.
Interesting that the Sterns kit has two inputs, with filtering of some kind on the input.
I guess it's purpose is to cut surface noise experienced with shellac 78's,more 'hiss' than a snake pit. I don't play 78's very often, so I won't be bothering with the filtration.
Very, interesting that the cutting template for the prototype denotes the completed chassis was 8x6x2 (inches). How wonderfully compact.
I am restricted by the space I have available on a shelf (see post #8). Every input, output and control MUST be on the front of the chassis. I have kept any AC mains conductor well away from any signal stage, and that will continue to be so.
I am going to have to remember to make the tag board up as a mirror-image of that illustrated in these constructional guides and mount the 'pots' in the different order too.

Has anyone done the circuit with Octal base valves, like EF37a and EL33 output?
As this is about Components choice a simple 'Yes' or 'No' will do to express if it is possible without expanding any further. Just in case anyone else wants to have a go at making a 3-3 of what is to hand.

Sideband: I'd love to see your effort on the scrap chassis.
I guess it makes you want get a better o/p transformer or start from 'scratch'.
You said it was "deafeningly loud'" in the workshop, so that'd be enough for there, but not fit to venture into 'respectable' areas of the house.
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Old 21st Mar 2012, 8:52 pm   #24
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Default Re: Mullard 3-3 information required

Hi Neil, the 3-3 was a vey neat design, Mullard in their original article did not skimp on the chassis size, but it could be made much more compact. Note that is was originally used with speakers that were much more sensitive than thaose of today, so apparently much louder.
It was designed by Mullard as a marketing tool to sell their EF86/EL84/EZ80 valves; there is no reason at all that it cannot be built using octals that have similar characteristics (some research needed in the valve data books).
As ever with an amp like this a lot is down to the op trans.

Ed
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Old 21st Mar 2012, 9:52 pm   #25
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Default Re: Mullard 3-3 information required

Quote:
Originally Posted by Neil Purling View Post
Sideband: I'd love to see your effort on the scrap chassis.
I guess it makes you want get a better o/p transformer or start from 'scratch'.
You said it was "deafeningly loud'" in the workshop, so that'd be enough for there, but not fit to venture into 'respectable' areas of the house.
..not sure you would! I built it on the scrap chassis of the B3G63A Philips radio. I'd left the mains transformer, rectifier and output transformer in place and built the 3-3 around them. Not tidy at all.

It's certainly a possibility that I'll build two for stereo but I don't know when. Far more likely that I'll build a couple of 5-10s

Rich
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Old 22nd Mar 2012, 6:20 am   #26
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Default Re: Mullard 3-3 information required

Oh, go on. Don't be shy!
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Old 22nd Mar 2012, 6:35 am   #27
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Default Re: Mullard 3-3 information required

Hi Neil,

as I mentioned in my post (#2) I made a 3-3 but using EL33's. It needed a bit of tweaking (I had lots of help regarding this from kind people on here) but works wonderfully.

James.
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Old 22nd Mar 2012, 12:28 pm   #28
Neil Purling
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Default Re: Mullard 3-3 information required

For visual presence you can't beat the 'G' type valve envelope.
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Old 22nd Mar 2012, 3:56 pm   #29
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Default Re: Mullard 3-3 information required

Definitively beautiful.

Simple and beautiful.

I think the Mullard 3-3 must be the beginning milestone to reach for everybody who love valve electronics. I'll see if I can build one of them someday (too many projects by now)
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Old 22nd Mar 2012, 4:51 pm   #30
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Default Re: Mullard 3-3 information required

Hi Neil,

Not forgotten about your transformers, but I realized there are no connection details, and I need to measure them to ascertain the primary and secondary connections before sending them to you .

I’ll take a photo of my Sterns 3-3 but it’s not as nice as the octal based units above.

I suppose you could use a 6V6.

To connect with another thread on the Forum, Gilbert Davey featured the Mullard 3-3 in the Fun With hi-fi book.

PM sent

Regards
Terry.

Last edited by Valvepower; 22nd Mar 2012 at 4:54 pm. Reason: Add Fun With hi-fi .....
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Old 22nd Mar 2012, 6:00 pm   #31
Neil Purling
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Default Re: Mullard 3-3 information required

I have appealed in the proper audio forum in case any Members have a Armstrong Stereo 44 & may be able to say where the coloured wires go to.

Even Premier listed a Mullard 3-3 amplifier, though whether it was their own I am not sure as they were selling some Sterns items at the time.
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Old 23rd Mar 2012, 8:25 pm   #32
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Default Re: Mullard 3-3 information required

Hi Neil,

Iíve measured the transformer windings and arrived at the connections in the uploaded drawings. There is a drawing of the connections on the actual transformer along with a copy of the 44 amplifier with the connections marked on the diagram.

Iíve also included a scan of the 3-3 amp in the Gilbert Davey Fun with hi-fi book from 1973 ; youíll note he really rates this amplifier. Sorry for the upside down scans.

Regards
Terry.
Attached Files
File Type: pdf 44_SCH.pdf (110.7 KB, 83 views)
File Type: pdf Trans_Con.pdf (39.1 KB, 71 views)
File Type: pdf 3_3_FWhifi.pdf (344.9 KB, 103 views)
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Old 24th Mar 2012, 5:46 am   #33
Neil Purling
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Default Re: Mullard 3-3 information required

I have been looking through some papers and I came up with some sheets from the Mullard Technical Service Department, Mullard Hse, Torrington Place, London, WC1.
They show the 3-3 and the two-valve pre-amplifier.
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Old 24th Mar 2012, 7:49 am   #34
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Default Re: Mullard 3-3 information required

Hi Neil, these will be the circuits that are in the Mullard "Circuits for Audio Amplifiers" book published in the 60's, well worth getting and often seen on e-bay for not too much.

Ed
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Old 24th Mar 2012, 1:14 pm   #35
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Default Re: Mullard 3-3 information required

The eariler one is here http://www.vvttransformers.co.uk/drb...b12919_dhn.htm
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Old 24th Mar 2012, 3:32 pm   #36
Neil Purling
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Default Re: Mullard 3-3 information required

Yer right Ed. Seem on ebay and bought for 'not too much'.
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Old 8th Apr 2012, 7:04 pm   #37
Neil Purling
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Default Re: Mullard 3-3 information required

I followed the Sterns manual in the making of the group board etc. I omitted the filtration for the input though.
I was re-using an existing chassis, just punching new holes for the two Noval bases and extra control pot.
I bought a pair of Svetlana (Winged 'C') EF86 with 'cheese-grater' anode structures, dated 07/85.
I am not able to spend money like a sailor on a run ashore.
Partridge power & output transformers & Telefunken valves are waay out of my league.
Fellow Forum members have been a great help with parts.
You know who you are: I don't know if it is okay to name names, but you know who you are.
I had only one EL84. You will have seen my appeal for Soviet EL84 on the Forum. Among thos I was offered was a pair of 6P14P out of a Rigonda dated 1968 & 1969 respectively. They are perfectly OK.
This thread brought about the offer of some Hinchley output transformers.
The Sunday weather wasn't very promising, so I got stuck in.
Sure-enough I made two wiring mistakes. I fixed one & tried again to discover I had created a Banshee. It howled ferociously.
I was ready for that! I think that it was the Sterns manual that mentioned it. You reverse the connections to the output transformer Primary.

In operation you can't see the EF86 heater is working except a dim glow in a blacked-out room. The tone controls are very effective.
Maybe someone can enlighten me as to what harmonic distortion sounds like?
If it makes the amplifier tinny sounding, then that was what afflicted my previous effort. Not so with the Mullard 3-3.

Another 3-3 is born.....
I need a set of matching knobs and proper decals for the controls, but the beggar is working well without them.
Enjoy the pictures.
I have made changes after those images were taken during construction. The white ceramic 3W 330R resistors were removed & a extra piece of earth bus to reach pin #2 of the EF36
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Last edited by Neil Purling; 8th Apr 2012 at 7:08 pm. Reason: Extra Text
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Old 9th Apr 2012, 7:24 am   #38
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Default Re: Mullard 3-3 information required

Nice one Neil, why is it that the feedback is always the wrong way round first time.
Quote:
Maybe someone can enlighten me as to what harmonic distortion sounds like?
Lift the feedback and have a listen then.

I think it is only people afflicted with a (or even a pair) 'Golden Ear' need to buy expensive valves. Remids me of the line in a Flanders & Swan song, 'Oh we never listen to music much, it's the Hi Fidelity!'
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Old 9th Feb 2014, 9:02 am   #39
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Default Re: Mullard 3-3 information required

Hello.

I have just built a 3-3 amplifier, but I noticed there are two different circuits. One was published by the Radio Constructor and the other by Mullard. I began with the RC one, and was dismayed to find it unstable. The DC feedback path from the EL84 cathode to the EF86 screen, which consists of a 1M resistor in parallel with a 0.1uF, means that a small amount of signal passes to the EF86 screen at low frequencies. Far better is the Mullard design that has a capacitor directly to ground from the EF86 screen. In fact I don't know how the Radio Constructor ones ever worked. Just thought I'd share that, as I spent quite a few hours tracking down the problem.
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Old 12th Feb 2014, 10:15 pm   #40
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Default Re: Mullard 3-3 information required

Useful info.
I'm about to embark on a stereo 3-3 project having obtained a pair of radiospares "high quality" SE output transformers. I shall Use the Mullard circuit now that I have that gem of information.
I have no connection info for the radiospares transformers, they look to be a sort of "Universal" unit with different winding taps. Is there an online resource where I can get the wiring info?

I was going to use an EZ81 rectifier but as there's only one 6.3V secondary on the mains transformer I think I'll use a couple of UF5408 diodes and adjust the voltage with a filter resistor. I don't see any issues with this.
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