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Post subject: 6L6's in a DRRI?
Posted: Mon Jul 28, 2014 4:24 pm
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I've ordered a matched pair of 6L6's from Eurotubes that I'm going to install in my DRRI. When I ordered them I asked him a few pertinent questions. Thought you would like to know his answers. Here's my email mixed with his replies to each of the questions:

Hi Bob,
Last Friday I ordered a matched pair of 6L6's from you that I want to install in my 2008 DRRI. I just have a couple of questions. I know folks do this but:
a) Does the difference in the design of the tubes mean that the final impedance in an otherwise unmodified Deluxe Reverb will require a different impedance speaker?
Bob's Reply:
No, even though the 6L6GC’s have a little different impedance you don’t need to change a thing. We’ve been doing this for decades in both original and as long as the RI’s have existed.

b) I love the tone of the AB763 circuit that the DRRI and TRRI are based on. Will changing to 6L6's drastically change that tone?
Reply:
6L6GC’s will sound slightly different than 6V6’s, the tone will be extremely close but the 6L6’s will sound bigger.

c) Is there enough resistance in the bias adjusting pot so that I won't have to modify the circuit? I'm hoping I won't have to do any circuit mods so that it will remain in original condition (aside from tubes).
Reply:
We rarely have an issue with getting the bias up and I’ve put a personal note in on your order to pick a hotter grade to help with this. I do highly recommend experimenting with the bias to see where you like it best. You will be choosing between a warmer tone and the headroom you want, it will be a compromise.

d) Will the 6L6's give me more clean headroom? (that's the rumor and the purpose for the change)
Reply:
Yes, a bit more headroom and a bigger sound. If you want more headroom then consider going with a 5751 in the channel you most often use. If you use the second channel all the time then a 5751 in V2 will get you more headroom.

So I'm hot to trot to do this when the tubes arrive!!!


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Post subject: Re: 6L6's in a DRRI?
Posted: Mon Jul 28, 2014 6:20 pm
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Sounds interesting, definitely post the results. :arrow:

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Post subject: Re: 6L6's in a DRRI?
Posted: Mon Jul 28, 2014 7:05 pm
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Lynn, one other thing --- check the heat of the PT. A pair of 6L6GC draws about 1 amp more heater current than a pair of 6V6GT's.

Good luck! Keep us posted.


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Post subject: Re: 6L6's in a DRRI?
Posted: Mon Jul 28, 2014 7:21 pm
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Thanks for the encouragement, guys. I'm looking forward to it. It would be cool to have a 22 Watt or so version of the Twin Reverb. I Like the sound of a pushed 6V6, but I just really dig a Twin! I have both, but that 85 watts in a man-cave makes my ears ring for hours!! Wish there was a better music scene here in eastern Oregon, so I could put a band together and gig with the Twin, but there just isn't. I'll keep you posted.


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Post subject: Re: 6L6's in a DRRI?
Posted: Mon Jul 28, 2014 11:38 pm
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:shock:

You will see some minor improvements with 6L6's, but not much as one would expect. The output tranny is there preventing the tubes to sound much 'bigger' with more headroom.

I have extensively tested a few types of tubes in my 1966 BF DeLuxe. Settled with JJ's 6V6s's.

Very nice tubes for the amp indeed!! :lol:
viewtopic.php?f=12&t=92598&start=30

\ :wink:


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Post subject: Re: 6L6's in a DRRI?
Posted: Wed Jul 30, 2014 5:59 pm
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YES!!! Got those JJ 6L6's from Eurotubes today. According to Bob at ET, 6L6's are rated at 25W plate dissipation. Using that value in the formula Plate Dis/Plate Volts*.7= Bias Current, then 25/386*.7= 45 ma. So I set mine at 47 ma and I now have a mini Twin Reverb! The sparkling clean AB763 comes through up until about 7 on the volume knob. After that you get a little of that sweet 6L6 crunch. And it's LOUD for 22 or so watts...much louder than 6V6's that start clipping at around 4.5 to 5 on the volume knob. I'm a crappy hamper...er...ah...a happy camper!!


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Post subject: Re: 6L6's in a DRRI?
Posted: Wed Jul 30, 2014 6:47 pm
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Hard to believe:

- you have an AB763 in DRRI

- that you gained much power increase with 6L6, as the output tranny is still the same

:mrgreen:


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Post subject: Re: 6L6's in a DRRI?
Posted: Wed Jul 30, 2014 7:48 pm
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Nick, I do not believe that I'm getting more output power by simply installing the 6L6's in place of the 6V6's. With the original tubes the amp would start clipping sooner than with the 6L6's, so I actually gained more clean headroom which translates to more volume with the same amount of power. Then you can add whatever distortion/overdrive if that's what floats your boat. I happen to like that sparkling clean Twin Reverb 6L6 sound and accompanying headroom before the amp starts distorting. It makes a better platform for pedals.

And, if I'm not mistaken, the original 65 Twin Reverb, Deluxe Reverb, and Super Reverb amps, and some others were all based on the AB763 circuit, and the reissues strive to reproduce that circuit/sound or whatever you call it. The 65 Princeton and maybe some other smaller amps were not AB763, but were similarly updated. I don't have the exact history details memorized. :)


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Post subject: Re: 6L6's in a DRRI?
Posted: Thu Jul 31, 2014 5:03 am
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If you insist on doing this, i'd use a small battery powered fan (like the little hand held ones to keep you cool on the beach). Use it to draw air out on the tranny side of the amp.

Heres the one i use......batteries last a loong time.
http://www.amazon.com/O2COOL-Battery-Op ... attery+fan

I use this all the time set upside down on the back of the amp over the power tubes.............even with 6V6's, this keeps the tranny (and tubes) from getting schorching hot.


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Post subject: Re: 6L6's in a DRRI?
Posted: Thu Jul 31, 2014 6:36 am
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I will only use the exact same type of fan that Leo included on any of his amps. :wink:

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Post subject: Re: 6L6's in a DRRI?
Posted: Thu Jul 31, 2014 10:29 am
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shimmilou wrote:
I will only use the exact same type of fan that Leo included on any of his amps. :wink:


+1

And the same brand of "jock strap" to hold my power tubes.

:lol:

Arjay

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Post subject: Re: 6L6's in a DRRI?
Posted: Thu Jul 31, 2014 2:09 pm
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Are there any Fender tube amps that have a fan installed from the factory? I can't think of any. :idea:

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Post subject: Re: 6L6's in a DRRI?
Posted: Thu Jul 31, 2014 2:39 pm
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The only Fender amp I can think of that *deserved* a fan is the 400PS. But no, it didn't have one. It was however fitted with vents for convection cooling, as were a number of other Fender models in the late '70s and early '80s.

Arjay

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Post subject: Re: 6L6's in a DRRI?
Posted: Fri Aug 01, 2014 2:44 am
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A tube amp that has enough room in its design & heavy enough chassis doesn't need a fan. Solid-state amps may need fans, as they are more sensitive to heat.

If I have several amps sitting next to each other, I use a floor fan, pushing air upwards to help the air convection flow.


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Post subject: Re: 6L6's in a DRRI?
Posted: Fri Aug 01, 2014 4:09 am
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But he's going to be taxing that tranny using 6L6"6, making excessive heat.
For $9 and a couple D batteies, I'd use the fan i mentioned....or a fan like you use.


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