EL84 equivalent

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hotair
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EL84 equivalent

Postby hotair » Sun 08/08/10 10:51 am

Just curious if there was a EL84 equivalent in 7 pin as the 6AQ5 is to the 6V6?
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Postby zaphod_phil » Mon 08/09/10 2:24 pm

Never heard of anything like that myself, if it exists at all. With EL84s, probably 9-pin is considered a small enough format already for most purposes. There is however a mini-EL84 inside ECL86 / 6GW8 tubes, plus one triode of a 12AX7. Still 9-pin format, but it allows you to build a 13W version of an 18W PI and power stage with just two tubes.
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Re: EL84 equivalent

Postby Merlinb » Mon 08/09/10 3:21 pm

The EL95 is about the closest you'll get, I think. Rated at 6W max, and with about two thirds the gm.
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Postby zaphod_phil » Mon 08/09/10 3:38 pm

So not really a true equivalent in gain terms at least, but it might suffice.

Also check out the 6DZ7, which is apparently like a pair of EL84s in a single octal bottle. These EL84s are the milspec rugged type similar to 7189As, and good for 13.2W dissipation each as well as 440V.
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Postby hotair » Mon 08/09/10 9:08 pm

Have not looked over the specs yet but the EL41 might be something to look at if I was really inclined.

Basically I wanted to find something with the same signal requirements as the 84's but utilizing a cheap available tv tube.

But the 6AQ5 being an offshoot of the 6V6 family needs more signal voltage to drive than an EL84. I am shoehorning this in a small cabinet so I am height challenged and am a little limited in my heater supply. The 6AQ5 will work but since I am already loosing signal from the tone stack.
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Postby hotair » Tue 08/10/10 7:46 pm

Ultimately my thoughts are to put together a 9watt rather than an 18watt. Still new at the tube game so I do have some learning to do. But the general idea was to use a 70 volt speaker transformer as the output transformer, 120v to 240v transformer for high voltage and a a wall wart transformer for the filaments. (Online auction the trio cost me about $15)

Wanted to see if I can come up with a cheap design (relatively speaking) for someone on a budget to take the plunge in rolling their own amp. I am pretty much of the opinion there is no cheap equivalent for the EL84 as the 6aq5 is to the 6V6. Was hopping to go for the Marshall sound rather than Fender.

Will still give it a go with the 6aq5's as a winter project, maybe much of the sound is in the circuit and not the tubes.
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Postby hotair » Tue 08/10/10 7:55 pm

zaphod_phil wrote:So not really a true equivalent in gain terms at least, but it might suffice.

Also check out the 6DZ7, which is apparently like a pair of EL84s in a single octal bottle. These EL84s are the milspec rugged type similar to 7189As, and good for 13.2W dissipation each as well as 440V.
I think part of my dilemma is in finding a cheap available tube to use. I am sure I can find one in the 120v - 180v range in a TV tube but then it negates the cheap Chinese transformers as a supply. Shame they do not have a 120v to 120v. Actually the lower voltage may be an advantage for someone just starting out in tube amps. Cheaper caps and a bit safer. There I gonow, the wheels are starting to spin. May have to rethink things. Thanks for the help guys, needed someone to bounce ideas off of.
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Postby Plexi » Tue 08/10/10 8:49 pm

Posted this many years ago.. 6GK6. You can buy NOS of all different brands. Mullard, RCA sylvainia etc.. i bought many for 6 to 8 dollars each.
Same data as the EL84 except the 6gk6 are rated 330v plate and 330v screens,and about 1.5 watts more each tube,look like EL84s, small rewire of the socket to use them. Many just never seemto try them. they work and sound great.
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Postby dotfret » Wed 09/01/10 8:00 pm

I am somewhat unwell. so I am not putting any effort into checking what I say = do your own research.

The ELL800 was two EL84 in one envelope. Very rare and obsolete in the 60s.

Without thinking about the 6p14p direct replacement, there are two cheap Russki valves you can use instead of EL84 if you are gentle with them re. voltages. One is EL83 spec, I think that is a 6p15p. The other is a later development, and has a number like 6p42p/6p41p/6p32p/6p31p - this is a control amp valve, you only ever see the spec sheet from a vendor, and it does not like a high B+. OTOH it can be a direct EL84 replacement in a lot of circumstances.

If you really insist on using cheap old TV valves, look at the EL821. Sorry, I can't quote the US equivalent - but there is one!
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Re:

Postby crgfrench » Fri 04/26/19 9:54 pm

zaphod_phil wrote:
Mon 08/09/10 2:24 pm
Never heard of anything like that myself, if it exists at all. With EL84s, probably 9-pin is considered a small enough format already for most purposes. There is however a mini-EL84 inside ECL86 / 6GW8 tubes, plus one triode of a 12AX7. Still 9-pin format, but it allows you to build a 13W version of an 18W PI and power stage with just two tubes.
The ECL86 seems like the best thing since PB&J, or since chocolate met PB in the Reese's cup. Phillip's datasheet has PP power at 13.6W with a 300V supply. I am thinking this will be my first foray into long tail pair PIs. Anyone have opinions of the sound?
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geoff 1965
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Re: EL84 equivalent

Postby geoff 1965 » Fri 04/26/19 11:46 pm

hello,
i've seen ecl86 single ended "lunchbox" guitar amps but have'nt actually heard one,but here's a bogen schematic using 2 in push/pull + phase inverter.
bogen_schem2.jpg
might be worth experimenting with!
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Re: EL84 equivalent

Postby crgfrench » Sat 04/27/19 1:29 am

Thanks Geoff65 -- that inspired me to design a Class A, 2-input, 2-tube, 6W with a single Volume pot and a Twang switch (with diode Recto) tonight, just for this tube. I bet Arizona Blue Cactus would be sweet for the coupling caps, and I'm thinking it would go nicely in a little Tweed Champ cab with a Jensen P8R...
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geoff 1965
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Re: EL84 equivalent

Postby geoff 1965 » Sat 04/27/19 8:37 am

i like your "think outside the box" and have a go attitude!
not sure about your PT secondary of 290V though,mine is 275V and diode rectified gives me 360 VDC B+ so yours will be higher.
here's another schematic with ez80 rectifier and ef86 & 12ax7 preamp tubes,it might help you with the "ball park" area for voltages.
hansen1.jpg
this is a bit of a coincidence! i watch a guy on youtube who restores old valve radio's and he recently did a radio with a triode/pentode valve which gave me idea's.my concern with the ecl86 triode was the gain factor i.e. if it was like a 12au7 it would be okay for the phase inverter but not very good for the preamp so i've checked it out and it has a gain factor of 100 the same as a 12ax7,look's good!
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geoff 1965
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Re: EL84 equivalent

Postby geoff 1965 » Sat 04/27/19 6:51 pm

the more i look into these ecl86's the more i am impressed,have a listen to this amp!
https://youtu.be/GsWzUMqA5W0
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crgfrench
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Re: EL84 equivalent

Postby crgfrench » Sat 04/27/19 7:24 pm

That Frugal mini superlead sounds great even through my Mac Pro internal speaker and recorded with his videocamera. Thanks for finding and posting the video. These tubes are kind of expensive, in the $60 range for NOS but I think I'm going to play with them. This video certainly highlights their tone possibilities and they have a nice smooth breakup.

I don't see why he used dual volume controls when there is only a single input and no channel switch -- what's the point of controlling each individual tube volume if its the same signal path? I guess if the tone stack is between them that would make sense but I think this is a push pull setup that wouldn't really allow for that. Maybe he built both a pre-PI and a post-PI master volume??

(edit addition): ...Well he does say "for the 2 sides of the normal channel". I don't get that, the 2 VRs in a 1959 are fed by 2 different inputs (see attachment)
Screen Shot 2019-04-27 at 10.04.08 PM.png
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Last edited by crgfrench on Sat 04/27/19 9:07 pm, edited 1 time in total.
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