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5881 power tubes VS. 6v6....

55GibsonLPJR

Member
Messages
751
Hello,

I have an amp that has 6v6 power tubes and I am wondering if anyone out there has switched their 6v6 amps to run on 5881 to make their amp LOUDER???
 

drbob1

Gold Supporting Member
Messages
28,303
You have a couple of problems, there:
1. Without changing the B+ voltage (the plates) you're not going to get a lot more volume out of the 5881s than the 6V6s. You'd need to change the power transformer for that.
2. 5881s will draw more heater voltage and there are very few 6V6 amps that can provide what's needed, so the tubes will brown out and sound bad.
3. The OT will cause an impedance mismatch with the speakers, you'll need to plug your 8 ohm speaker into a 16 ohm tap to get the right balance (if I have that right).

There are amps designed to do this: the Groove Tubes Soul-o 75 and Dual 75s, some single ended amps like the THD or Emery ones, London Power and so on. All of them have PTs designed to supply whatever heater and B+ voltage needed, plus wide adjustments for bias and in some of them switchable output impedance...
 

bamboo633

Member
Messages
90
+1 on drbob1's post.

I have replaced the 6V6s in a tweed Deluxe with 5881s. The transformer I used had multiple taps so I could increase the B+ and was capable of supplying the heater current required. In the end you are still limited by your OT. Not to be thwarted, I upgraded the OT as well but didn't like the way the amp sounded in the end and changed it all back.

Increasing wattage is an inefficient way to increase volume anyways, you need 10 times the wattage to get twice as loud. You are much better off going to a more efficient speaker, or better yet, multiple more efficient speakers to get more noise out.

In short, I don't think its worth it to upgrade to a 5881 because even if you do the work to allow your amp to take advantage of the extra power you may not be happy with the sound of it anyways.
 

swiveltung

Senior Member
Messages
14,486
So, here's a question that's related: How do the amp makers that advertise using 6V6, or 6L6 etc in the same amp deal with the Output Tranny primary impedance issue? (not to mention some other things) I've often wondered.... do they just live with what comes out?
 

Figaro

Silver Supporting Member
Messages
12,929
Not much difference between 5881s and 6V6s without changing anything else, a little fatter tone. But there is more of a difference between 6L6s and 6V6s. I've changed a Deluxe Reverb to 6L6s, just a re-bias and it sounds just a little louder and cleaner.
 
Last edited:

55GibsonLPJR

Member
Messages
751
So 5881's are very close to 6L6's...it seems the little boost in volume prob isn't work all the rest. I wonder if I get 2 new 6V6 power tubes it may make a difference? ..my goal is more volume.....

6v6 - I've had the ones in there tested (JJ's) and they seems to still be strong if not perfectly new- funny thing, is one of the tubes reads a little bit less than that other and they are a pair = is this an issue in a class a/b amp ?
 

Franktone

Gold Supporting Member
Messages
3,101
I've got an amp that can run any of them in pairs or as singles. To me the 6V6's sound OK but just do not have the fat sound that the 5881's can kick out with the strat and the Gibson guitars.

To me the Tung Sol 5881 tubes have the perfect sound between the 6V6 and the 6L6, and the 5881 slides right in the middle. The 6L6 has the big blunt scooped sound if you need all that power but you have to really run them up high in volume (power) to get its best. The 5881 just really does it for me for a beam tetrode tube.

Other than that I'd actually probably rather have the EL34's in there with their big raspy pentode design.
 

wyatt

Member
Messages
4,167
So 5881's are very close to 6L6's...it seems the little boost in volume prob isn't work all the rest. I wonder if I get 2 new 6V6 power tubes it may make a difference? ..my goal is more volume.....
Then you need a more efficient speaker or an extension cab. Adding 3db speaker sensitivity is the same as doubling output wattage (which is WAY more than you can do by tube rolling). Changing tubes isn't ever going to get you a significant change in stage volume.

Or you can use a re-amp device like a Bad Cat Unleash or the new Fryette equivalent (name?).
 

Franktone

Gold Supporting Member
Messages
3,101
I would check with the manufacturer of the amp whether it is OK to substitute in the larger octal tubes and which ones can be used if any. You can always put it up on a chair to hear it better and mike it through the PA. And yes a speaker that puts out more power for each watt in is not a bad idea, but each speaker will have a different personality, and speakers are not cheap. I'd just start looking for a more powerful amp that has the sound you want with the larger tubes you desire.
 

IM4Tone

Member
Messages
3,769
So 5881's are very close to 6L6's...it seems the little boost in volume prob isn't work all the rest. I wonder if I get 2 new 6V6 power tubes it may make a difference? ..my goal is more volume.....

6v6 - I've had the ones in there tested (JJ's) and they seems to still be strong if not perfectly new- funny thing, is one of the tubes reads a little bit less than that other and they are a pair = is this an issue in a class a/b amp ?
Re-amp it. This device can function as either an attenuator or a re-amp.....rave reviews.
http://www.fryette.com/power-station-integrated-reactance-amplifier/
https://www.thegearpage.net/board/index.php?threads/fryette-introduces-the-power-station.1517894/
 

IM4Tone

Member
Messages
3,769
Yes the Power Station is your ticket but you are probably going to need another speaker cabinet that will be fed by the Power Station.
Perhaps. That depends on the rating of the current speaker. The Fryette puts out 50 watts.
 

IM4Tone

Member
Messages
3,769
The cabinet I'm using is a 2x12 with 2 vintage G12-65 speakers.
That should be no problem then. If you're loving the amp, it's the way to go; otherwise sell it, add the $$$ of the Fryette PS and get a 6L6 platform amp and then you can use 5881's if you prefer.

Of course, the volume variation with your existing amp attenuated or pre-amped will be hard to match.
 

Franktone

Gold Supporting Member
Messages
3,101
And don't listen to everything I said about tubes because the circuit and components, transformers, have perhaps even more sway on your sound besides the tubes.

A lot of those dumble and dumble fashioned amps are running 6L6 tubes and have tone to die for.

So try out many amps if you can and remember that generally all power tubes have their strengths depending on which amp they are in.

But if you are really happy with the tone that you have with your present already, then the Power Station has the ability to attenuate and reamp the sound of your present up to 50W and the Power Station can be adjusted to put you into your amps sweet spot for almost any room, large or small.
 

Laurent Brondel

Silver Supporting Member
Messages
2,998
Hello,

I have an amp that has 6v6 power tubes and I am wondering if anyone out there has switched their 6v6 amps to run on 5881 to make their amp LOUDER???
What amp? I've replaced the 6V6's in m SFDR's with Sylvania 5881's (after a rebias of course), and while the tone is a bit different and has possibly a bit more headroom, it is not louder. The limiting factors are usually the OT and PT, so it really depends on the specific amp. Besides with 5881's or 6L6's the speaker impedance is going to be half of 6V6's with the same OT, so you'll want to match different speakers to get maximum efficiency.
 

Blue Strat

Member
Messages
30,192
What amp? I've replaced the 6V6's in m SFDR's with Sylvania 5881's (after a rebias of course), and while the tone is a bit different and has possibly a bit more headroom, it is not louder. The limiting factors are usually the OT and PT, so it really depends on the specific amp. Besides with 5881's or 6L6's the speaker impedance is going to be half of 6V6's with the same OT, so you'll want to match different speakers to get maximum efficiency.
This! The POWER SUPPLY in an amp is the limiting variable for power (and clean headroom requires power), not the power tubes.
 

mad dog

Silver Supporting Member
Messages
10,990
Even if the amp setup and transformers permit, the swap may or may not be to your taste. My Allen Encore head is fine with 6L6s, 5881s or 6v6s. Can't remember if you have to swap the rectifier to go down to 6v6s. Whether or not, it's no biggie. I tried many 6L6s, including a great old pair of RCA blackplates. Then tried my favorite 6v6s. Finally, got a pair of NOS Tung Sol 5881 in there. The 5881s are staying. At least for this particular amp, that's where my favorite sound and feel is. The 6v6s weren't bad in any way ... just a matter of taste.

I know you can swap the other way (to 6L6 or 5881) with the Allen Accomplice, which typically comes stock with 6v6s. Wondering if that amp sounds better with 6v6s or more powerful tubes.
 

cap47

Member
Messages
2,272
So, here's a question that's related: How do the amp makers that advertise using 6V6, or 6L6 etc in the same amp deal with the Output Tranny primary impedance issue? (not to mention some other things) I've often wondered.... do they just live with what comes out?
I use 6V6s and 6L6s in my 5E3. I have a Bandmaster 35W OT in it with stock PT. Mag Comp OT 40-18088. I use the same speaker tap for either.
 




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