Mystery stereo valve amp and pre...

[ff1d1l]

Anyone any idea on identity?
Car boot find...
Thanks!
http://i1304.photobucket.com/albums/s535/ff1d1l/end_zpsa0yh02an.jpg (http://s1304.photobucket.com/user/ff1d1l/media/end_zpsa0yh02an.jpg.html)
http://i1304.photobucket.com/albums/s535/ff1d1l/Untitled-1_zps6iyp8ywb.jpg (http://s1304.photobucket.com/user/ff1d1l/media/Untitled-1_zps6iyp8ywb.jpg.html)
http://i1304.photobucket.com/albums/s535/ff1d1l/pre3_zpsjbctlwis.jpg (http://s1304.photobucket.com/user/ff1d1l/media/pre3_zpsjbctlwis.jpg.html)http://i1304.photobucket.com/albums/s535/ff1d1l/pre4_zpsdmyxhw81.jpg (http://s1304.photobucket.com/user/ff1d1l/media/pre4_zpsdmyxhw81.jpg.html)http://i1304.photobucket.com/albums/s535/ff1d1l/from-top_zpsyaz27ufz.jpg (http://s1304.photobucket.com/user/ff1d1l/media/from-top_zpsyaz27ufz.jpg.html)
http://i1304.photobucket.com/albums/s535/ff1d1l/innards1_zpsjefdmgnx.jpg (http://s1304.photobucket.com/user/ff1d1l/media/innards1_zpsjefdmgnx.jpg.html)
http://i1304.photobucket.com/albums/s535/ff1d1l/innards2_zps41soj1sx.jpg (http://s1304.photobucket.com/user/ff1d1l/media/innards2_zps41soj1sx.jpg.html)
http://i1304.photobucket.com/albums/s535/ff1d1l/Pre1_zpshad5fubv.jpg (http://s1304.photobucket.com/user/ff1d1l/media/Pre1_zpshad5fubv.jpg.html)
http://i1304.photobucket.com/albums/s535/ff1d1l/overall_zpsvt8g7lei.jpg (http://s1304.photobucket.com/user/ff1d1l/media/overall_zpsvt8g7lei.jpg.html)
http://i1304.photobucket.com/albums/s535/ff1d1l/Pre2_zpsy0h2uxne.jpg (http://s1304.photobucket.com/user/ff1d1l/media/Pre2_zpsy0h2uxne.jpg.html)

[Arkless Electronics]

Possibly home made or bodged from defunct commercial chassis.... Single ended, probably EL84 output valves and about 3-4 WPC. Quite likely to be Mullard "3Watt Amplifier" design and EF86 used at input. Decent Parmeko transformers. Will need rebuild to be usable, I can see several capacitors that will be dud by now = sell on again at next booty!

[BTH K10A]

..

[Firebottle]

As above.
Dulci maybe? Go on spill the beans, how much did it cost you?

Always on he lookout for something like this :scratch:

[ff1d1l]

I don't think its home made - the front panel on the Pre is not within those parameters! There's an umbilical like a Leak which you can see in one pic - all very professional. My mate (who is up your way Jez) said he thought just possibly a kit? He's quite knowledgeable about old gear, designs and makes amps, and has, or has had a lot of obscure stuff, but he had no idea either.
Dulci is an interesting suggestion....thanks.

I got the Pre and Power, a Leak Varislope Pre missing some panels and a kit valve tuner (can't remember make - mono) for £20, all missing their valves though. One of those stalls which is just lines of boxes of junk, prob from skips. I once got a pair of Stax earphones on a similar stall...but that's another story.

[Arkless Electronics]

£20 is just about ok for the transformers.... The mains transformer could be useful for a valve pre. There was indeed a lot of kit amps on offer at this time to Mullard (and other) designs and also many magazine articles on making them, but there were also many "second league" manufacturers pretty much unheard of nowadays making such amps and selling them through the likes of "Practical Wireless".

The power amp may just be worth rebuilding if you have some very sensitive speakers to use it with but unless you DIY it would cost more than its resale value to do so. It will probably sound pretty good at low volumes as in spite of being single ended it will have a lot of negative feedback.

[Macca]

What is the name under the treble knob? Can't read it all because of the angle of the photograph.

[Arkless Electronics]

I would say it doesn't matter what make it is.... as I said so many were offering both kits and ready made examples of Mullard designs as to make it irrelevant. Better ones would claim things like "Parmeko/Gardners/Elstone transformers used in accordance with Mullard specs"

[spendorman]

As above.
Dulci maybe? Go on spill the beans, how much did it cost you?

Always on he lookout for something like this :scratch:

Dulci came to my mind too.

[Arkless Electronics]

Whilst it's irrelevant..... I have I believe identified them as kit amplifiers made to Mullard designs by Stern Radio Ltd around 1962.

[spendorman]

Whilst it's irrelevant..... I have I believe identified them as kit amplifiers made to Mullard designs by Stern Radio Ltd around 1962.

Excellent, I remember Stern, then presumably later Stern-Clyne

[ff1d1l]

What is the name under the treble knob? Can't read it all because of the angle of the photograph.

Its "Dual Stereo"

Stern...excellent...any Pics anywhere, Jez?

Thanks all!

[Arkless Electronics]

Its "Dual Stereo"

Stern...excellent...any Pics anywhere, Jez?

Thanks all!

From an ad in a 1962 Practical Wireless. Pics are tiny, blurry and B&W but it appears to be the same as the control layout and positions of the 1/4" jacks on the front panel are the same. The power amp is as I guessed and the pre is two of the Mullard "Two valve pre amp" design, for stereo. if correct it would have had 2X EF86 per channel.

[BTH K10A]

..

[ff1d1l]

It would be a Stern Radio Ltd Dual 3 - 3 stereo amplifier then, with the 4 valve dual channel control unit which should contain 4 EF86 valves.

Both Mullard circuit designs

The input sensitivities are:
Aux 330mV
Mic 3mV
Pickup 5-15mV &70-220mV
Tape 4mV
Radio 330nV

Amp is obviously 3 Watts per channel with the single ended EL84
Frequency Response is 35 to 30kHz

Absolutely without a doubt. Just googled, and although the exact ringer for the power amp isn't there, the mono version is same gold chassis and same trafos with the same voltage selector on top. Well, now I know - thanks very much to everyone. If and when I get it going - probably the power rather than the pre - I'll report back. Cheers again guys!

[Barry]

Design and construction of the Mullard 3-3 amplifier: http://www.r-type.org/articles/art-003h.htm.

The 3-3 was a mediocre-sounding circuit and nowhere near as good as the later 5-10 and 5-20 designs.

[Firebottle]

If and when I get it going.....

When I rebuilt the Dulci into a stereo single ended amp I used the following driver stage circuit, with very good results as Martin will confirm.

http://i601.photobucket.com/albums/tt97/Paramotorpilot/Dulci/Valve%20driver%20stage.jpg

Use a medium mu valve such as the ECC81 and don't forget the heater bias (2 resistors at the right).

Just a suggestion :)

[BTH K10A]

..

[Macca]

When I rebuilt the Dulci into a stereo single ended amp I used the following driver stage circuit, with very good results as Martin will confirm.

[:)

I do confirm. One of the most beautiful sounding amplifiers I have ever heard. A bit limited on power which is the only reason it is not my daily driver (big room) but that is the nature of the beast.