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Zen SE84A Tube Compliment - Options? (Read 4918 times)
Lonely Raven
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Zen SE84A Tube Compliment - Options?
07/24/08 at 15:42:42
 
I'm wondering if it's safe to swap out the tubes on my 10 year old Zen amp with different tubes. I know the preamp is wired for the 6N1P family of Russian tubes, but can I swap the SV83 for EL84 and what about the Rectifier?

I ask because I have several vintage guitar amps and I have all sorts of 50's and 60's vintage tubes. I'm not sure if the older SE84A was locked in to run only the SV83 and JAN 5Y3GT that Steve gave me.

I have no stock tube compliment right now as I gave my set to a friend, so I'm starting fresh. I just thought it might be fun to try out some NOS and ANOS I have around while I wait for a tube order to come in!

Thanks in Advance!
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« Last Edit: 07/25/08 at 05:18:35 by Lonely Raven »  
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Eli Duttman
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Re: Zen SE84A Tube Compliment - Options?
Reply #1 - 07/24/08 at 23:47:10
 
Dude,

EL84s are fine instead of SV83s.  The EL84/6BQ5 works in sockets wired for the SV83, but not the other way around.

In addition to the 6n1p, all 6DJ8 family tubes are fine in the voltage gain "hole".

You could get in trouble using a rectifier that's not a member of the 5Y3 family.  The forward drop in the 5Y3 family is very large.  Do you have a 6106 or a 6087 in your collection?  Those are 5Y3s with cathode sleeves.
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Eli D.
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Lonely Raven
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Re: Zen SE84A Tube Compliment - Options?
Reply #2 - 07/25/08 at 05:18:12
 


Ahh, typo. I know the EL34 are octals. Thanks for catching that.

I have a bunch of NOS EL84 and 6GK6 I might want to try out on the SE84. I know 6GK6 would require a rewiring of the pins.

The only difference I see between the pin outs of the SV83 and EL84 is pin 1. I'm wondering how the SV83 would sound in a guitar amp...probably too high-fi.

I don't have the 6087 or 6106 tubes, just the more common 5V4 5U4GB and 5AR4 types.

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Eli Duttman
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Re: Zen SE84A Tube Compliment - Options?
Reply #3 - 07/26/08 at 01:12:09
 
Dude,

All of the rectifiers you mention have a smaller forward drop than a 5Y3 does.  The only one I'd be willing to take a chance on is the 5U4.

SV83s will FRY in a guitar amp.  The screen grid is way too fragile.  Look carefully at the 6p15p/SV83 data sheet.  Both pin 1 and pin 6 are connected to an internal shield and the suppressor grid.  Also, notice that g3 is not internally tied to the cathode.

BTW, you could use the SV83 in a guitar amp specifically engineered for it.  Pentode mode "finals" and 0A2 regulated screen grid B+ are what it takes.
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Eli D.
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Lonely Raven
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Re: Zen SE84A Tube Compliment - Options?
Reply #4 - 07/26/08 at 02:28:37
 

Hmm, sounds like I'm in over my head on converting/building a guitar amp to run on both SV83 or EL84. I didn't follow anything in that last line.

I've built a half dozen kits, cobbled a couple guitar amps from scratch, and serviced several dozen Fender amps...but all of them I had a layout to follow...it was just like paint by numbers to me. I just copied what I saw in front of me with no understanding besides basic safety. Every amp I've built and serviced fired up the first time, but that doesn't mean I learned anything.   Tongue

If I have a two EL84 amp I wanted to change over to SV83, is that possible or would I require all new output transformers? If I had an example to follow, I could easily wire the pins to what was needed, but as I said, I'm not sure I follow you.
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Eli Duttman
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Re: Zen SE84A Tube Compliment - Options?
Reply #5 - 07/26/08 at 19:11:01
 
Dude,

Look at the 6p15p data sheet.  Please notice that the screen grid limit is 150 V.  The 0A2 is a 7 pin mini, 150 V., gas discharge regulator type.  ;)  Regulating screen grid B+ happens to extract max. linearity from pentodes.  If you set an amp up for 6p15p/SV83s, it will definitely function, when EL84s are installed.  What it will sound like is TBD.
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Eli D.
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Lonely Raven
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Re: Zen SE84A Tube Compliment - Options?
Reply #6 - 07/26/08 at 20:04:41
 
Yeah, I'm honestly not expecting such a linear tube to sound great for guitar, this is more of an excercise for me to learn something. I learn best when I have a problem in front of me and I figure my way through it.

Once I figure out how to design a simple tube circuit without just following a layout, that opens up a whole new world of experimentation for me, both in simple guitar amps and in audio listening.

I have an itch to try a Zen amp with a 12BZ7 and SV83 with a nice big coke bottle rectifier tube. I just don't know how to start.....yet.  :)
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