Marshall branded EL34s

parker_knoll

ICBM said:

boz_h said:

I have a an bit of an issue with these valves in a THD Bivalve, they can only run on the low voltage setting (around 330 volt).  If I use them on hi voltage (470 ) the HT fuse blows.  Derrick at Watford Valves was really helpful and sent me a replacement set (still had the same issue) a set of Harma EL34s (which worked fine on Hi voltage) and a big box of 5 amp fuses.  He seems to to think its because they are running in Class A (ish) mode and cannot handle the extra stress.  They sound decent enough, but I am not convinced of their robustness. 

I think we’ve just found out why Marshall didn’t want them.

I've put a set in a Laney PA100 which runs very high voltages. I was previously running Shuagang EL34Bs in it as well, but a mis matched set. They are visually identical to these. I've only put an hour of playtime on them and so far so good. If any faults appear I will update. 

jpfamps

boz_h said:

I have a an bit of an issue with these valves in a THD Bivalve, they can only run on the low voltage setting (around 330 volt).  If I use them on hi voltage (470 ) the HT fuse blows.  Derrick at Watford Valves was really helpful and sent me a replacement set (still had the same issue) a set of Harma EL34s (which worked fine on Hi voltage) and a big box of 5 amp fuses.  He seems to to think its because they are running in Class A (ish) mode and cannot handle the extra stress.  They sound decent enough, but I am not convinced of their robustness. 

I suspect that these are older production EL34Bs.

OK, the earliest versions of the Chinese EL34B had a fault in the wiring.

In a pentode there is a grid between the screen grid and the anode called the suppressor grid that is (usually) referenced to the cathode voltage, and whose function is to prevent electrons emitted from the anode (by secondary emission) from reaching the screen grid.

In an EL34 the suppressor grid is connected to pin 1 and the cathode connected to pin 8, and in virtually all amps these pins are tied together externally to the valve; thus the suppressor grid is at the same potential as the cathode, but the cathode current doesn't pass through the suppressor grid.

In the earlier EL34B versions, the cathode was internally tied to one end of the suppressor grid, and the other end to pin 8 of the valve base; thus all the current passing through the valve passes through the suppressor screen.

The suppressor screen is not designed to pass large currents and hence the higher rate of failure, especially in cathode biased amps who habitually are biased at higher current draw.

This fault has been corrected in  current production EL34Bs.

How can you tell which is the older faulty version?

Look into the valve and see if there is anything connected internally to pin 1; if there isn't then this is the older EL34B version.

parker_knoll

Thanks Frank. 

The man from Del Monte he say "yes". There is something connected to pin 1.

Definitely EL34B and I would say Shuagang with certainty. 

Frank knows how many volts the Laney puts through the tubes as he's serviced it. 

Anyway, £8.50 each from Watford for those that want 'em

jpfamps

parker_knoll said:

Thanks Frank. 

The man from Del Monte he say "yes". There is something connected to pin 1.

Definitely EL34B and I would say Shuagang with certainty. 

Frank knows how many volts the Laney puts through the tubes as he's serviced it. 

Anyway, £8.50 each from Watford for those that want 'em

Indeed the Laney's are fairly tasty at around 600 VDC.

My personal best was a Dynacord amp with around 810 VDC on the anode: 90W from 2 x EL34s.

Keiko

Here are the Marshall valve codes:

VLVE-00007 12AT7/ECC81 No selection White Logo

VLVE-00009 12AU7/ECC82 No selection White Logo
VLVE-00010 EL34 Svetlana
VLVE-00033 SV6550C Svetlana White Logo
VLVE-00038 6V6GT Shuguang White Logo
VLVE-00039 KT66 Shuguang White Logo
VLVE-00042 EL34B Shuguang Gold Logo
VLVE-00047 12AX7B/ECC83 Shuguang Low Microphony Gold Logo
VLVE-00049 12AX7B/ECC83 Shuguang High Microphony Gold Logo
VLVE-00055 12AX7B/ECC83 Shuguang No Selection White logo
VLVE-00063 12AX7B/ECC83 Shuguang A Low Microphony White Logo
VLVE-00064 12AX7B/ECC83 Shuguang B Low Microphony White Logo
VLVE-00065 12AX7B/ECC83 Shuguang Gain Selected >=4V White Logo
VLVE-00066 ECC83S JJ Low Microphony Red Logo
VLVE-00066S ECC83S Microphonic Selection A
VLVE-00067 ECC83S JJ Low Microphony Red Logo
VLVE-00067S ECC83S Microphonic Selection A
VLVE-00068 EL84 JJ Graded Low Anode Current Red Logo
VLVE-00069 EL84 JJ Graded High Anode Current Red Logo
VLVE-00070 EL34 JJ Graded Anode Current Red Logo
VLVE-00071 EZ81 JJ No selection Red Logo
VLVE-00077 KT66 Shuguang Graded Anode Current Gold Logo
VLVE-00080 KT88 Shuguang Graded Anode Current Gold Logo
VLVE-00083 5881/6L6WGC Shuguang Graded Anode Current Gold Logo replaces VLVE-00006
VLVE-00087 EL34B Shuguang Graded Anode Current White Logo
VLVE-00088 GZ34/5AR4 JJ No selection Red Logo Replaces VLVE-10043

parker_knoll

It's these ones:

VLVE-00087 EL34B Shuguang Graded Anode Current White Logo 

https://watfordvalves.com/product_detail.asp?id=5640

compare to:

https://www.karltone.co.uk/shuguang-el34-b-628-p.asp

It's a bargain. 

soma1975

I've chucked some of these in my Astoria and it sounds glorious. Not as hifi as with the KT66s and with a nice bark. 

NelsonP

Reviving an old thread but I just bought some EL34Bs to put into a Marshall DSL20CR. The code is VLVE-00087. The look different from the EL34s that are in there. These have a red base, rather than black and are slightly larger than the originals.

Are they OK to use?

ICBM

NelsonP said:

Are they OK to use?

Yes. They’re Shuguang EL34Bs, standard fitting for Marshall EL34 amps at one time.

NelsonP

Thanks!