Subbing EL86 (6CW5) for EL84 - diyAudio
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Old 29th November 2004, 07:51 PM   #1
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Default Subbing EL86 (6CW5) for EL84

I finally got round to replacing EL84s with EL86s in my modded Leak TL12+s. Very interesting. Remember that the anode-cathode max for the EL86 is 275v and the screen max is 220v. I'm running them at 225v B+ with 375R cathode resistors, giving 21v on the cathode, i.e. 56mA. Max current rating is 110mA so I could afford to increase the HT to about 245v and bump up the current to 60mA at least. I have a 2.2uF cap into the first choke, so this suggests 3uf or 3.3uF. I'd like to run the input at 300v HT so I'll try to re-arrange the HT setup. I have 2 chokes to play with...... . I asked chris found about using a -50v bias as earth for the two input valves. He said that he'd tried it in Beard amps and while it worked for the first valve (diff pair), it took too much current for the second. Crowhurst suggests using this for one diff pair (he suggests using the output valves' neg bias as earth for the diff pair, and grounding the grid of the second half of the valve direct to earth.) My circuit is 2C22 (6J5G) into 12b4 concertina. Anyway, the sound. I'm using NOS GE EL86s. They all measure really well - close and strong, clearly a good production run. Well - the sound is leaner than the EL84, more detailed, clearer vocals, more delicate treble. Bass is lighter, which is a drag. The warm fat EL84 sound is gone. At the present operating points I find them slightly sharp at higher volumes - I'm not using global NFB and using UL at 6.6K. fine for EL86, low for EL84. Needs a few more turns on the volume for the same output. I'd say at lower volumes I'd give it to the EL86s. I need to look at the circuit a little to make sure I'm hearing the best out of the EL86.
Anybody else used the EL86 (6CW5)?
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Old 29th November 2004, 10:22 PM   #2
mcs is offline mcs  Denmark
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Default Re: Subbing EL86 (6CW5) for EL84

Quote:
Originally posted by andyjevans
Anybody else used the EL86 (6CW5)?
Only in my Philips AG9015 amp (one of the 800 ohm OTL amps).

Best regards,

Mikkel C. Simonsen
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Old 30th November 2004, 12:29 AM   #3
RE 604 is offline RE 604  Germany
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Hello ,
yes , I use the EL 86 very often in regulated power supplies and in my Klein + Hummel TS 60 poweramp , which I rebuild many years ago .
Philips had several amps with this tubes for their 800 ohm speakers and also Telefunken had an amp with EL 86 , but with transformers .
Regards , AlexK .
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Old 30th November 2004, 04:26 AM   #4
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Hi,

If you want the sound of the EL84 with the mids and hifghs of the EL86 in an amp that was designed to use the EL84 in the first place try the Russian EL84M.

This is a military version of their EL84.
I haven't checked whether or not it's still available but in case you can't find any and by chance find a vendor that sells some NOS Siemens E84Ls I'd recommend giveing them a try.

Those E84L have always been my fav EL84 and as they last forever they're not that expensive for the quality they offer.

The European made EL86s have high transconductance which is in part what you're hearing compared to the EL84s.

Keep in mind that these tubes aren't really interchangeable and that you're really comparing apples to oranges by subbing them without further adjustments to biasing.

Quote:
yes , I use the EL 86 very often in regulated power supplies
It's about the best small current pass tube on a noval nase you can find for this application, again thanks to its high transconductance and high perveance.

Cheers,
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Old 30th November 2004, 06:59 AM   #5
drcy is offline drcy  Hong Kong
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Default A circuit is worth a thousand words!

Would you be kind to share your circuit with us? Thank you in advance!
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Old 30th November 2004, 03:50 PM   #6
RE 604 is offline RE 604  Germany
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Hello ,
if you mean the regulator and power amp circuits , send me a mail . Mail adress is on my homepage .
Regards , AlexK .
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Old 28th May 2005, 06:13 AM   #7
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Pretty tricky situation. They're very different tubes.The EL86 seems to be easy to drive, just like its cousin, but they draw more current, about 50% more. I put a pair to the test. I ran the plates at 330 volts through a 3500 ohm load, with the screens locked at 200 volts and grid bias, and got 20 clean watts, 30 to 30kHz. The thing is, current was 150 mA @ 20 watts. Just some food for thought.
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Old 15th April 2013, 03:45 PM   #8
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Quote:
Originally Posted by tubularjoe View Post
Pretty tricky situation. They're very different tubes.The EL86 seems to be easy to drive, just like its cousin, but they draw more current, about 50% more. I put a pair to the test. I ran the plates at 330 volts through a 3500 ohm load, with the screens locked at 200 volts and grid bias, and got 20 clean watts, 30 to 30kHz. The thing is, current was 150 mA @ 20 watts. Just some food for thought.
Great data! I wanted to build an audio PA for a friend! A cathodyne ps with 6SN7 will work great, I think. Is it a fixed bias or a cathoded bias amp?
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