any tube guys out there have exp with el506's?

[kepeb]

i have an old selmer amp which i've never used. i bought it a while back as a project but realised after how sparse el506 seem to be, they arent produced anymore it seems.

anyway, i was comparing the specs of el506 to el84s and they dont appear THAT far away. little bit less output/maximum voltage etc.
it would mean adjusting some voltages obviously, but would the OT be ok with less power going through?

would a conversion be worth it?

the amp is a selmer compact 30, i think it would be pretty cool as a head

[Robert M. Martinelli]

Hi,
Time ago I had an old ( late '60s-early '70s ) amp with two EL504s in it, I used a couple of Russian 6P36S with good results; 6P36S are pin-to-pin compatible with EL504s, but NOT with the EL506 ( no anode cap and different pinout ) but, since they're cheap and can be rather easily found ( I bought 'em on eBay ) I think they're worth a try, even if you'll have to rewire the sockets and maybe alter the operating conditions some.

As to EL 84s, their max plate dissipation is 12W, while the EL504 and EL506 are around 16-18W AFAICR.

I see no problems in running the OT at a lower power, just take care about the correct impedance matching, even though slight mismatches are not a big problem IMHO.

Hope this helps

Best regards

Bob

[kepeb]

i've not seen that one before probably a much better idea, i'll check it out.
thankyou

[stokes]

If you have to rewire the sockets anyway,I would say go for the EL84's.If the reflected impedance the tubes see with that OT is too far off,you can always use a different speaker load to get it closer.You really have a lot of leeway with speaker load/primary impedance with tubes.

[Robert M. Martinelli]

Hi Stokes,
The problem is that, AFAICR, EL506s have a MAG-noval socket, similarly to EL500s, EL504s, ( they have an OD of about 27-28 mm ), while EL84s have a "standard", smaller 9 pin socket, so, by choosing EL84s he would be forced to change the sockets, and not only rewire them. The matter would be complicated by the socket holes being much bigger than the new sockets.

Though 6P36S are not pin-to-pin compatible, they share the same
( MAG-noval ) base of the EL506, and at least the heater's pins are the same, so giving them a try shouldn't be much of a hassle IMHO.

JM2CW

Cheers

Bob

[stokes]

Thats what happens when I assume.... didnt bother to look at pin out or diagram,he made a comparison to an EL84 so I assumed it was an option.

[olddawg]

Tube sockets are cheap. If you are going to rewire the sockets it will be a much more pleasurable experience to hook up new sockets. The thing I would be concerned with the EL84s would be the B+. You usually don't want it too much more than 350v. What is the B+?

[kepeb]

hey.
so b+ is the plate voltage right?

i believe this is the schematic.
http://www.freeinfosociety.com/elect...ompactsv30.pdf

i am convinced i could make the physical changes. i.e. the tube sockets/wiring
but the voltage changes i would be unsure of.

kev.

[olddawg]

i am convinced i could make the physical changes. i.e. the tube sockets/wiring, but the voltage changes i would be unsure of.

The B+ is the filtered high voltage supply coming from the bridge rectifier in this case at 460v. There are people on this board much more experienced in tube designs than I am, but I would say that is much to high for EL84s by about 100v. I would suggest 6V6s. I would probably gut the amp at this point and make a new turrent board following a known good schematic for a popular 6V6 amp. There is a variation of the 18 watt Marshall that uses 6V6s. It's a screaming amp and very plexish.

[kepeb]

hmmm.
ok, well that sounds a heck of a lot more complicated than just a different set of tubes but i guess as it is a project and not a job i can only stand to learn from it.
i might weigh up if its really worth doing that some more first then.

if i am to build practically from scratch would it not be best to start with a different chassis and new components too?

where do you think i should draw the line?

i bought the amp as just the chassis and the front panel. (i have pics) it is from the 60s/70s and the tubes just glow too hot when i turn it on. i figured i'd replace them but then found out about 506's and then suggested el84's here on the board.

it cost £65 a couple months back before i moved house. presuming there will be no collectable value after it's been gutted and re-designed, are the transformers/ other parts worth the initial outlay if i do as you suggest?

thanks for your help
kev.

[olddawg]

hmmm.
ok, well that sounds a heck of a lot more complicated than just a different set of tubes but i guess as it is a project and not a job i can only stand to learn from it.
i might weigh up if its really worth doing that some more first then.

if i am to build practically from scratch would it not be best to start with a different chassis and new components too?

where do you think i should draw the line?

i bought the amp as just the chassis and the front panel. (i have pics) it is from the 60s/70s and the tubes just glow too hot when i turn it on. i figured i'd replace them but then found out about 506's and then suggested el84's here on the board.

it cost £65 a couple months back before i moved house. presuming there will be no collectable value after it's been gutted and re-designed, are the transformers/ other parts worth the initial outlay if i do as you suggest?

thanks for your help
kev.

More than likely you can use the chassis, the transformers, the preamp tube sockets (although I would suggest using new ceramic ones, they're cheap), and probably the control pots. You just populate a turrent board with new components, wire it up, and mount it in the old chassis. In the U.S. it wouldn't cost much more than $100 if that. I should stress though that there are lethal voltages present in tube amps, even when unplugged. (that 460v line is one of them) If you do not know how to safely navigate and understand the process, I would suggest that you read up and learn first or differ the project to someone that does.

[Wakculloch]

I would be very reluctant to advise anyone to gut an old selmer. They are starting to go for silly money. Fitting 6p36s's involves a couple of wires changed on the base and getting hold of some top caps, all easily undoable when some idiot waves a wadge of cash about.

[olddawg]

I would be very reluctant to advise anyone to gut an old selmer. They are starting to go for silly money. Fitting 6p36s's involves a couple of wires changed on the base and getting hold of some top caps, all easily undoable when some idiot waves a wadge of cash about.

Sorry, I have no idea what the value of an old Selmer chassis would be. I was concerned with making a usable amp. The obvious solution then is to sell it and start again with something more servicable.
Cheers

[kepeb]

ok.

i dont think the high voltages would ever become less of a concern for me.
until recently i have only experimented with low voltage effects. there was a lot more room for error there, safety wise, obviously.

i have picked up quite a lot with the help of some cool guys here on the forum and i think i have developed some good habits for when i'm testing stuff.

i do want to pursue a deeper knowledge though, and cant think of a better way.
i am building up my test gear and learning more. especially with the great feedback here.

i would hope, as I'm not really in a desperate rush to complete the project, i would benefit a lot more. and hopefully with some pointers could keep it safe.

I do have lots of questions, but that's what forums are for right?


so on another note...
i was looking at the tube sockets and i'm awaiting my member approval from 18watt.com so i can get a look at their forums/schematics and check it out.

[kepeb]

so you think sell it on, or bring it back to stock would be better?

if that is the case, i'm pretty interested in still starting an 18watt project now...
would i be able to get as decent a starting point (ie. chassis, transfrmers etc) for the same outlay?