Pye Mozart HF10 stereo pair

[mik_rik]

I haven't heard your Radford but other than that I strongly disagree with everything you said I'm afraid...

Fair enough,agree to disagree ,can't remember if I took it to NEBO AT Seaton Carew ,if I did ,good chance you heard it there.Again ,just my experience of valve rolling...cheers

[spendorman]

Mullards are recognisable by a code etched onto the glass[usually starting with the letter b denoting Blackburn plant,a double seam on top ,and a hole in the locating spigot.Towards the end of valve production,there was quite a bit of cross buying going on but I have no Brimar or Mazda Mullard made,including Ecc and Ef types. Mick

Yes, I remember about the hole in the end of the spigot. Anyone remember Bentley Acoustic? Supplied many makers valves under their own name.

[Arkless Electronics]

Yes, I remember about the hole in the end of the spigot. Anyone remember Bentley Acoustic? Supplied many makers valves under their own name.

Yep and "Zearux valve mail order" (not sure about spelling), Pinnacle, Edicron and there were a few others.. some of these (most!) were dodgy as fuck! I've gone through a pile of Pinnacle EL84's sticking em in a Leak stereo 20 and watching them self immolate within a minute when fitted as sets of four! Some however were Mullards remarked as these brands! Or Tungsram etc.. I reckon it all depended on what they could get their hands on at the time!

About 6 months ago I needed a new GZ34 for my Stereo 20 (the Mullard hadn't failed.. I'd been made an offer I couldn't refuse for it by a guitar player!) so i turned to a bag of Edicron ones I'd picked up for next to nowt .. and found out why.... 5 failed. Some lasting as long as 2 days... otherss little as 2 minutes... the sixth is giving sterling service after 6 months... Caveat emptor

[Arkless Electronics]

Fair enough,agree to disagree ,can't remember if I took it to NEBO AT Seaton Carew ,if I did ,good chance you heard it there.Again ,just my experience of valve rolling...cheers

No offence intended Mick. I'm just blunt as you will have realised... The 6p3s is roughly equivalent to the 6L6 but has much reduced ratings. It would be fine in a 6L6 based amp giving 20-25W but in one giving 40 it would have a life in single digit hours probably. they are though (or were) very cheap. Yes there are other rated types available that get near to USA types in rating. The e or b (Russian e or V) normally mean long life rating or harsh environment rating and are often (if you're lucky!) military NOS, which if you get the pukka thing are as good as Mullard. I wouldn't trust the "OTK" in purple on the envelope much any more as resellers/charlatans have cottoned on to it and it's easy to fake!

Philips (Dutch owners of Mullard since about 1930-ish IIRC) had a patent on the pentode well before RCA came up with their answer in the "beam power tetrode". Their "new big thing" was the 807, which was a top anode RF rated valve that did sterling service in WW2 for us and the yanks and was knocking on a bit by then... The 6l6 was a cheapened version optimised for audio amps but based closely on the 807. There are loads of variants of the 6L6! probably more so than any other valve. The KT66 is indeed a "kinkless tetrode" ie beam power tube by a different name to get round RCA's copyright. It's a further improved and higher rated SQ version of the 6L6 but British basically.. The KT77 is a GEC/Marconi/Osram answer to the EL34 and although a beam tetrode is optimised to be as pentode like.. and EL34 to be specific.. as possible, and again was intended as a higher rated better quality version of the commonly used EL34 of course.

5881 is a military spec version of 6L6 and there is a lovely Russian version of this which may be based on the 6p3s.. it has a very thin "button base" to cut down on the height of the valve... rumours are they were used in the servo of the bomb doors of Russian cold war era bombers and they had to be reduced in height to fit in the available space... possibly apocryphal! These, if pukka, are superb and I'd take them in preference to non military spec/SQ/selected Brimar, GEC (USA GEC of course. Unrelated to UK GEC AFAIK) etc..

All from memory, as google would be cheating.... and weds are pub night... hick... so if wrong I apologise

I've done loads of conversions from one type to the other on guitar amps in the past and for proper operation the screen grid resistor needs changing from 470R to 1K and the bias voltage is sufficiently different for optimum operation that only in some models of amp will it come within the adjustment range of the bias pot.. on some amps a resistor needs changing as well to get it in range. The Pye is fixed bias... sort of cathode bias ish I guess (you can't adjust it IIRC) but it's an interesting design! After rebuilding and modernising a pair a few years ago I was quite surprised by their sound... At reasonable levels quite SS like in many ways (in a good way), much more detail and precision than you may expect! However... it all went a bit Pete Tong well before they reached anywhere near clipping from memory. Rated at 10W (or was it 8?) I would not want to use them much above say 4W for best results. Leak Stereo 20 trounces them on max volume and slam etc but at low volumes I recall them being at least the equal of the Leak and maybe better

The transfer characteristics are fairly different and they therefore sound pretty different.... for good or bad depending on taste and amp model...

[spendorman]

I used to buy quite a lot of Zaerux (Z&I Aero Services), they were cheap, but not always good. Picked them up from their shop in Edgware Road (I think). Just picked one out of my (very large) box of spares. Zaerux.jpg

[spendorman]

When the Radford STA25 was reintroduced in 1984 (I think), the GEC KT77 was chosen, as good quality EL34's were difficult to obtain.

I have a set of these GEC KT 77's, they go for silly high prices these days.

[spendorman]

Surely it's the GE 5881, I have some of these as replacements for KT66's in my Quad II's, though I have not used them yet (in about 40 years!)

I believe that at one time Quad supplied these for the Quad II.

In the 80's I worked for GEC (Marconi), in the staff shop we could buy GEC products, including Hotpoint, as GEC owned them, strangely, GE (American) products became available too in the shop, there was some tie up between the two companies.

[Arkless Electronics]

Surely it's the GE 5881, I have some of these as replacements for KT66's in my Quad II's, though I have not used them yet (in about 40 years!)

I believe that at one time Quad supplied these for the Quad II.

In the 80's I worked for GEC (Marconi), in the staff shop we could buy GEC products, including Hotpoint, as GEC owned them, strangely, GE (American) products became available too in the shop, there was some tie up between the two companies.

Yes USA GE... I'd forgotten that they were often differentiated by the C being missed off the yank one... 6L6 and the mil equivalent 5881 are interchangeable with KT66 as KT66 was a later, British, improved answer to the 6L6....

[Arkless Electronics]

I used to buy quite a lot of Zaerux (Z&I Aero Services), they were cheap, but not always good. Picked them up from their shop in Edgware Road (I think). Just picked one out of my (very large) box of spares. Zaerux.jpg

That's the buggers yes!

[spendorman]

That's the buggers yes!

Their EL34's were a bit of a bomb, not all, but quite a lot.