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EL83 / 6CK6 valves in place of EL84
Posted: Sat 06/13/09 4:51 am
by DaveW
Since reading this thread ref. Rory Gallaghers modified AC30 using EL83s in place of EL84s I have been tempted to try these. I have finally done so and am really impressed. I think they give a slightly emphasised mid range and break up very well. They are also very cheap: picked up NOS Teslas off eBay for a couple of pounds each. I have had these running for a few weeks now with no problems.
Original link to Rory's AC30
http://vintageamps.com/plexiboard/viewt ... 30#p795629
Just a bit of a wiring change, didn't need to change any component values. I have now fitted a small toggle switch in between the bases to allow me to fit either. Having the switch set to the wrong position doesn't seem to do any harm either, they just don't work.
If anybody else wants to try I have listed what I did here.
http://s59.photobucket.com/albums/g293/ ... cture6.png
I ignored the screen connection on the EL83, would welcome any opinions on whether this is correct.
Re: EL83 valves in place of EL84
Posted: Sat 06/13/09 7:51 am
by zaphod_phil
DaveW wrote:I ignored the screen connection on the EL83, would welcome any opinions on whether this is correct.
If they're pentodes or tetrodes, I would have thought it would be essential to connect the screen grids.
Posted: Sat 06/13/09 8:12 am
by DaveW
Hi Zaphod,
I don't believe it is a screen grid (which I think is pin 1) , I think that it is some sort of interference screen. see base diagram and let me know if you agree.
Dave
Posted: Sat 06/13/09 8:26 am
by zaphod_phil
I just looked up the spec sheet -
www.mif.pg.gda.pl/homepages/frank/sheets/030/e/EL83.pdf
Yes, it seems to be just an internal shield (pin 8). Probably to keep interference either in or out, as this appears to be a TV valve. Personally, I would ground it, rather than just leaving it floating....
Posted: Sat 06/13/09 8:41 am
by DaveW
Thanks for the info Zaphod. I probably would have grounded it had I not gone for the switched option. Pin 1 is marked as an internal connection on an EL84 so I would have had to switch the ground connection on each valve, but I only had a 4 pole switch. If I see an inexpensive 6 pole switch or build an amp with only EL83s I would certainly do this.
That said I have had no problems to date with it left floating. I have tried Tesla and Mullards EL83s for compatibility and both worked fine.
Posted: Mon 06/15/09 8:43 am
by rayandkerry
Hi, guys.
Really cool concept! I am just about to whip together my first 18W and am really glad I read this thread before I drilled my chassis!
DaveW, you say you used a 4 pole switch. That's a 4PDT, right? Also, is it one of those mini-switches, or more heavy duty one (like a Carling power switch)? What Amperage rating?
Thanks, in advance, for your help!
Ray
Posted: Mon 06/15/09 10:03 am
by rayandkerry
For example, do I need something heavy-duty like product number 453-425 here (bottom left of the page):
http://www.rpelectronics.com/Data/RPCAT-115.pdf
Or would 451-420 suffice (middle of page).
Thanks, again!
Ray
Posted: Mon 06/15/09 10:50 am
by DaveW
Hi Ray,
I used one of these
http://www.maplin.co.uk/Module.aspx?ModuleNo=2343
I reasoned that the currents are not high and it will only be switched when the amp is off.
If I were you I would install the switch, build the amp stock and prove it works OK and then wire the switch in to the circuit and test with EL83s.
Let us know how you get on.
regards,
Dave
Posted: Mon 06/15/09 12:07 pm
by rayandkerry
Thanks, Dave!
I'm going to pick up the switch on the way home so I can plan how to drill the chassis.
You said: "If I were you I would install the switch, build the amp stock and prove it works OK and then wire the switch in to the circuit and test with EL83s."
Yes, thank you. That's a very good suggestion...one I will certainly follow (and one I would not have thought of on my own). KISS, to start...i.e. Keep It Simple, Stupid!
I think I will take that to heart with all amp modifications I try going forward. Thanks for the sound advice!
Ray
Posted: Mon 07/13/09 9:28 am
by dotfret
So I went to look at those AC30 pics - somebody noticed that one of the preamp valves was "rather large" - the one with red print in the pictures. Looks like it might be a Sylvania 12BZ7 (he guessed glibly).
Whatever, something tells me that there may be quite a lot of strange things that happened to that AC30 ...
Posted: Wed 10/21/09 1:53 am
by dgriff
Hi, I'm going to try some El83's in my lite 2b this weekend. Dave, how have they held up since your last post on the subject? Have you experienced any problems, or needed to tweak any component values yet? Any advice or opinions are apreciated.
Posted: Sat 11/28/09 3:05 pm
by PepeJara
I have done the mod in my 18 watt, and have installed a pair of Valvo el83, I couldn´t be happier...my other el84 amps are well equiped (mainly with Mullard el84) and this Valvo el83 are in the same league
Posted: Sun 11/29/09 2:03 am
by dgriff
I have have Telefunkens and Siemens which sound great. Just waiting for the Mullards to arrive
Great mod to use cheap NOS. I will have to try some Valvo's, my supplier has some.
Posted: Mon 01/04/10 8:56 pm
by PepeJara
Just two questions about the wiring:
Since the pin 6 isn´t used by El84, is there a reason for not leaving pin 3 and 6 conected permanently? I mean, without switch...
And the same question for pin 9 and 1...In el84 mode, pin 9 is used and 1 without connection, in el83 mode, the inverse, why not a wire between 9 and 1 permanently? Will I damage anything if doing so?
Posted: Tue 01/05/10 3:11 am
by DaveW
I did try leaving the other pins connected but it caused problems, after this time I can't remember what these were but I did in the end have to switch all the pins. I guess there are some internal connection issues.
Re: EL83 / 6CK6 valves in place of EL84
Posted: Mon 11/24/14 2:39 pm
by Seppola
DaveW wrote:Since reading this thread ref. Rory Gallaghers modified AC30 using EL83s in place of EL84s I have been tempted to try these. I have finally done so and am really impressed. I think they give a slightly emphasised mid range and break up very well. They are also very cheap: picked up NOS Teslas off eBay for a couple of pounds each. I have had these running for a few weeks now with no problems.
Original link to Rory's AC30
http://vintageamps.com/plexiboard/viewt" onclick="window.open(this.href);return false; ... 30#p795629
Just a bit of a wiring change, didn't need to change any component values. I have now fitted a small toggle switch in between the bases to allow me to fit either. Having the switch set to the wrong position doesn't seem to do any harm either, they just don't work.
If anybody else wants to try I have listed what I did here.
http://s59.photobucket.com/albums/g293/" onclick="window.open(this.href);return false; ... cture6.png
I ignored the screen connection on the EL83, would welcome any opinions on whether this is correct.
Hello!
I have both 6P15P-er and EL83 tubes, and I want to try this. Sadly, that photobucket picture does not open. The figure would understand better how the connection is made. EL83 datasheet says that the maximum screen grid voltage would be 150 volts, while EL84 withstand 300 volts. Have had durability problems?
Seppo
Re: EL83 / 6CK6 valves in place of EL84
Posted: Mon 11/24/14 2:49 pm
by davidw
Old Image
Haven't got that amp anymore but ran it with EL83s for quite a while and had no problems and sounded great. You could always hardwire for EL83s and try them before adding the switching.
Hope this helps, Dave
Re: EL83 / 6CK6 valves in place of EL84
Posted: Tue 11/25/14 2:20 am
by Seppola
Thanks, it helps a lot!
[/quote]Haven't got that amp anymore but ran it with EL83s for quite a while and had no problems and sounded great. You could always hardwire for EL83s and try them before adding the switching.
Hope this helps, Dave[/quote]
Re: EL83 / 6CK6 valves in place of EL84
Posted: Thu 12/04/14 12:05 pm
by niCko
I'm thinking of trying El83 as well. Seppola please report how it goes. I guess the only way to really find out the sound difference from EL84 is to try them out. If they sound good I will probably try to make adapters.
Re: EL83 / 6CK6 valves in place of EL84
Posted: Fri 12/05/14 11:36 am
by niCko
I was looking at datasheets and 6p15p is not directly equivalent with EL83, they have different pinout and characteristic data is measured at different voltages. Also I found the Tesla EL83 datasheet and they claim that "Tesla EL83 replaces foreign type 6CK6, CV2726, Soviet equivalent 6p14p."
So if this isn't a misprint this tesla el83 valve is closer to 6p14p than 6p15p.
I wonder how is the headroom of the EL83? Does it distort earlier?