el34 in a 5e3

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bigmik
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el34 in a 5e3

Post by bigmik »

about 2 years ago I built a 5e3 from a ceriatone kit I had nik upgrade the power tranny so I could run a gz34 and 6l6's recently went back to running it stock with a 5y3 and 6v6's and this got me to thinking about trying el34's in there has anyone else done this?I am thinking all I have to do is pop the gz34 back in and re bias or am I wrong.

thanks
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teletroy
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Post by teletroy »

I did this a few years a go and the amp really rocks. If I recall correctly, I did have a bigger OT and PT, because I started out running 6l6s. You should be fine after a rebias- make sure you tie 8 and 1 together on the power tubes, if they aren't already.
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zaphod_phil
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Post by zaphod_phil »

Normally you would run the EL34s at half the load impedance - ie a 4ohm speaker on the 8 ohm OT tap, or an 8 ohm speaker on the 16 ohm tap. Your PT needs to be able to handle the increased heater current as well as B+ current. And you will need to rebias.

It's usually considered better to bias EL34 suppressor grids (pin 1) negative relative to the cathode. So you would ground pin 1 in cathode-biased amps.
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bigmik
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Post by bigmik »

thanks again for the help I think I will give it a go,I think my tranny's will support the extra load but could you please explain why should the speaker's be run at half of the impedence?not that i don't trust what you are saying just because I would like to understand why.And should I do this also when running a el34 in my p1ex


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Michael
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Post by Michael »

bigmik wrote:thanks again for the help I think I will give it a go,I think my tranny's will support the extra load but could you please explain why should the speaker's be run at half of the impedence?not that i don't trust what you are saying just because I would like to understand why.And should I do this also when running a el34 in my p1ex


big mik
Phil will likely answer you, but it is just based on the output impedance characteristics of the tube type and how that affects an optimized load line.

If you review the tables, you'll see that the recommend impedances are a bit higher than half for the EL34 what they are for the 6L6/6V6, or even the EL84.
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Post by zaphod_phil »

Yes, just read the tube specs and you will see it right there.

In the P1eX you would normally run 6L6s and 6V6s with a 5k load and EL34s with a 2.5k. That's not an exact match, but in the right ball park.

http://tdsl.duncanamps.com/show.php?des=6V6GT
http://tdsl.duncanamps.com/show.php?des=EL34
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bigmik
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Post by bigmik »

thanks phil I now understand

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Phil_S
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Post by Phil_S »

Make sure you have adequate current on the filament supply. A 6V6 requires 450mA and a EL34 requires 1.5A. So you have x2 in this amp or a step up from 0.9A to 3.0A. It's a big leap.

As far as the circuit, look at the schematics for the Deluxe (5E3) and the Bandmaster (5E7). These amps are quite similar with the exception of the power section (6V6 cathode bias vs 6L6 fixed bias).
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Post by Phil_S »

Sorry, re-reading...if the PT was spec'd for 6L6, you might still have a filament supply issue. 6L6 requires 0.9A per tube, vs the EL34 at 1.5A. Can your tranny handle the difference between 1.8A and 3.0A? That's a big step up. One solution is to use an auxiliary filament transformer. These come up for sale on eBay pretty regularly for low prices. You can also just buy one retail.
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bigmik
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Post by bigmik »

wow I guess it's not as cut and dried as just swapping out the tubes ,everytime I post a question it's such a learning experience so I would like to thank everyone again,but the answers got me to thinking about a post that I made about a week ago concerning my jtm30 trannys
that also ran 6l6/5881 and phil made the suggestion that one option would be to replace the board with a 50 watt plexi style board and run el34's and I was seriously giving that one some thought but will i run into the problem of the need for increased filament current also?

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Phil_S
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Post by Phil_S »

If you are unsure of the capacity of the power transformer, contact Ceriatone. They should be able to tell you exactly what you've got.
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bigmik
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Post by bigmik »

hey phil-s i actually just finished e-mailing pics to nik right before I read your post,he told me that there was a tranny that would support the extra current ,he described it as "the thicker one"so i sent him the pics so he could see which one I had

thanks
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