Converting 6L6 to 6V6 or 7591

[Danyosound]

I have a Roland Bolt 60, the cleanest tube amp ever. It uses a pair of 6L6 power tubes and ss preamp. At the moment, I have a terrible blue Fender speaker (which I will be replacing with a Jensen Tornado). The 6L6 tubes in my amp make 60 watts.

I have been playing live gigs weekly for years. At first, I always had the volume at 5 (12:00), but now I tend to have the volume between 2-4, and it's louder than synth, bass, heavy drums, and vocals. The amp remains crystal clear to about about 6-7, and it's loud. When I play larger venues, I am always asked to turn down by the sound people because I'm mic'ed (the Echo, the Troubadour); when I play smaller venues I can turn up a little.

I seem to have a lot of headroom, if headroom is defined as loud, clean, undistorted sound. Too much!

I want clean sound, but I want the threshold lower so that I can utilize some tube overdrive when I stomp on a dirt pedal.

I'm thinking that 7591 tubes would be ideal.
I've read that there are some high current 6V6 tubes too.
Gassman writes that the newer JJ 6V6S tubes are supposed to be like 7591 tubes, but I have not read anything else to confirm his assertion (nothing on the JJ site).
https://forum.seymourduncan.com/sho...to-try-swapping-the-6L6-s-for-6v6-s-in-a-twin

I've read that 7591 tubes are extremely clean, and have lower wattage: between 6L6 and 6V6. Maybe that's what I want.

I've also watched this video comparing 6L6 with 6V6 tubes in the same amp. The 6L6 tubes sound better to me. But maybe it's because the volumes were set at the same place. I wonder if the person raised the volume on the 6V6 tubes if they would have sounded as good.
https://www.youtube.com/watch?v=_66s-FPOOXU

(A better comparison of 6L6 and 6V6 tubes would have compared the tubes at the same volume level to demonstrate the relative loudness of the tubes, and then to raise the 6V6 volume to unity with the 6L6 and compare the tones at the same volume level.)

WHAT DO I DO:

• Stick to 6L6
• Try JJ 6V6S (will I have to re-bias? will I need a new transformer?)
• Try 7591 (will I have to make socket mods? will I have to re-bias? will I need a new transformer?)

 

[jeremy]

Re: Converting 6L6 to 6V6 or 7591

all those tubes sound different and the jj6v6 is less of a classic sounding 6v6 than some others like tung sol. i use the jjs and i like them just fine. you can swap them into your amp but you will need to rebias, as you should any time you swap power tubes, even if they are the same type. it will lower the overall volume so might give you more control

 

[PFDarkside]

Re: Converting 6L6 to 6V6 or 7591

Don't you have to lower B+ as well if you go from 6L6 to 6V6

 

[Chickenwings]

Re: Converting 6L6 to 6V6 or 7591

Stick to 6l6 but order them from tube depot with your specification for minimum headroom.
If you really want to change tubes, try a set of 5881's. They will give you less output than 6l6s and will go in happily with no modification.
6v6s will require some modification and you will still have a loud amp due to the big transformers etc, but with a looser low end. Stage volume is much more a function of speaker efficiency than amp wattage.
I think you will get more benefit with some speaker swapping.
Swap that jensen tornado (and old blue fender) for an eminence texas heat to damp down the output and add some sweet tone. you can usually find these second hand so you can experiment for not a lot of dough. I find they are really excellent in high powered clean amps. I've used them in a couple of amps, but they are really great in my twin reverb (the king of clean amps!). In lower powered amps like a deluxe reverb, i prefer other speakers, but for anything running 6l6s they are a perfect match.
Inefficient, but good sounding speakers is the key.

 

[Danyosound]

Re: Converting 6L6 to 6V6 or 7591

No love for 7591s?

Sticking with 6L6 tubes might be the way to go, but one thing I did not consider too much was the speaker. Although I do know that more efficient speakers project more volume, I was thinking of getting a Jensen Tornado because I want lighter speakers: neodymium. My favorite sounding speaker is a Jensen C12K, but they are 11 pounds, compared to the 5 pound Tornados. So I'm trying to have a lightweight, clean amplifier.

So what if I got a less efficient tube, like those 5881 tubes, and a less efficient speaker?
I don't want the speaker to break up though.

I really love my amp and my sound. I just wish it wasn't so loud and heavy. Maybe a power attenuator....

 

[jeremy]

Re: Converting 6L6 to 6V6 or 7591

jj 6v6 handle plates up to at least 450, or at least thats as high as ive run them. thats about the top for most 5881's as well. do you know how high the plate voltage is on this amp?

you want a clean sound but you want tube overdrive when you step on a pedal? The tubes wont break up unless you hit the amp harder which will make it louder. i dont think you can change to 7591 without changing the pin out

 

[Danyosound]

Re: Converting 6L6 to 6V6 or 7591

Here is a picture I took under the hood.
The other picture is from the schematic notes provided by Roland.
* = Roland Bolt 30 (7591 version)
** = Roland Bolt 60 (6L6 version) [the one I have]

 

[Danyosound]

Re: Converting 6L6 to 6V6 or 7591

...not sure why it posted two pictures each...

 

[Danyosound]

Re: Converting 6L6 to 6V6 or 7591

And this

 

[Chickenwings]

Re: Converting 6L6 to 6V6 or 7591

So what if I got a less efficient tube, like those 5881 tubes, and a less efficient speaker?
I don't want the speaker to break up though.

less efficient speaker means less volume. The max (sound pressure level) of a speaker is measured in db (decibels).
The max spl of the speaker is not related to its wattage rating.
The wattage rating is purely the ability of the speaker to work within its safe range without overheating causing a coil burnout.
The texas heat has a large coil and can handle 150 watts. Your amp will not even get it close to "breaking up". Speakers that tend to break up are generally the lower wattage speakers such as greenbacks which are both low wattage and inefficient.
The big coil in the texas heat however is offset by a relatively small magnet, hence its inefficiency. So you get a speaker that can handle anything you can throw at it (up to 150 watts) but, due to its magnet size to coil ratio it takes its time transferring that energy into sound. They can feel a little stiff for small wattage amps but something with a bit of grunt (like a pair of 6l6s) gets the speaker moving nicely.
If you want to save weight tho, you can also get a texas heat with a neo magnet. It displays similar sound and response to the regular ceramic texas heat. It is called the "lil texas".
Another option that might suit you is a similar speaker with a built in adjustable attenuator. It is called the maverick.
It is only personal opinion, but tonally i would take a texas heat any day of the week over a c12k. the c12k is an honest, loud workhorse with a big magnet, but to my ears it can be somewhat hard, present and with a metallic spike in the high end. I don't think any of these characteristics will help tame the volume of your amp and warming the tone.

 

[jeremy]

Re: Converting 6L6 to 6V6 or 7591

i agree, i have a c12k sitting in a box that is waiting to be sold. its right next to a c12n that is in line for the same fate

 

[Lake Placid Blues]

Re: Converting 6L6 to 6V6 or 7591

So what if I got a less efficient tube, like those 5881 tubes, and a less efficient speaker?
..

5881s are 6L6s but do have a bit less headroom. The advantage of using 5881s instead of 6V6 are that they will be closer to your amp's original sound. Combined with a less efficient speaker it might get you what you want. As mentioned earlier, speaker efficiency will affect volume noticeably, but be aware that speakers have a profound impact on tone.

Changing to 6V6 will change the tone.

Changing the speaker will change the tone.

Using an attenuator will change the tone.

 

[Lake Placid Blues]

Re: Converting 6L6 to 6V6 or 7591

l
Another option that might suit you is a similar speaker with a built in adjustable attenuator. It is called the maverick.

This is a very interesting option especially if it sounds like a Texas Heat. Has anybody here tried this?

 

[Danyosound]

Re: Converting 6L6 to 6V6 or 7591

5881s are 6L6s but do have a bit less headroom. The advantage of using 5881s instead of 6V6 are that they will be closer to your amp's original sound.

The original tubes were RCA tubes. They were in the amp when I bought in the mid-90s. I wish I would have kept them. There was nothing really wrong with them. I installed GrooveTubes 6L6S tubes probably some 10 years ago (I've learned that they are repackaged JJs).

I play the amp all the time and rehearsals, gigs, and at home. I don't really understand the notion of tubes burning out. My tubes have always worked well. The amp is about 35 years old and has only had two pairs of tubes, it sounds awesome (clean as can be), and louder than I need for gigging.
Now if only I had a 25-30 watt that was just as clean with a pair of 10" speakers that weighed... 30-35 pounds...

 

[Danyosound]

Re: Converting 6L6 to 6V6 or 7591


Babes
[for some reason all of my iPhone attachments are double]

The Maverick looks cool and might be a good solution, but I also want light. I suppose it's lighter than a separate power attenuator.
Maybe Lil Texas instead of Tornado.
Maybe 23 watt 6L6 tubes.
Maybe the transformer is too much...

Thanks for all ideas. Of course, I'm searching for an unattainable perfection in my sound and equipment. So close!

 

[Chickenwings]

Re: Converting 6L6 to 6V6 or 7591

The other more elegant, more gorgeous sounding, but unfortunately more expensive solution is just to bite the bullet and get a deluxe reverb

 

[Danyosound]

Re: Converting 6L6 to 6V6 or 7591

Deluxe Reverbs are equally as loud. In my other band the guitarist plays a deluxe reverb and I play a 600 watt Genz Benz amp into a 212 cab, and she kills my sound after 2 1/2.

I know you're teasing with the "gorgeous sound" of the Deluxe after I made my claim that the Bolt 60 is the clean king, but the Bolt sound is way nicer and cleaner than the Deluxe. It's lighter too.

I just don't get these crazy high output amps. How can anyone deal with an amp over 50 watts when you can't crank it past 3 without drowning everyone out? - especially vocals.

20-30 watts. That's what I'm after. No EL34s. Clean clean clean. I'll probably keep my amp and tubes -- maybe switch to lower output 6L6 -- but I'm still going to change the speaker to a neodymium driver just so I can shave 5 pounds off.

 

[GoldenVulture]

Re: Converting 6L6 to 6V6 or 7591

What sort of music do you play , out of curiosity ?

 

[Danyosound]

Re: Converting 6L6 to 6V6 or 7591

My favorite bands are the Cure, Nirvana, Sonic Youth, Tones on Tail, Siouxsie and the Banshees, and I love new wave, postpunk, and 90s rock. My current band recently opened up for Missing Persons, which might be the highest profile gig I'll ever play. I play Jaguar-type guitars. Recordings will be available soon (I'm not advertising, I just mean that if I had a link I would offer it).

 

[hamerfan]

Re: Converting 6L6 to 6V6 or 7591

i own a Bolt 30 and i tell you its loud, too. It won't cure your problem.

There is a much easier solution, which really works. Our Bolts are hybrids, FET preamp and tube output. So they have an inverter tube stage. Try to locate the inverter tube. Its easy, yes the small one beneath the big tubes. This should be surprisingly a 12at7. If you use a 12ax7, you get into distortion much faster on a lower volume level. Try and report back.