6L6 tubes vs. 5881??

55GibsonLPJR

Member
Messages
797
So I have a 20w amp that has 2 6v6 power tubes in it and I am going to take them out and replace them with either 6L6 or 5881 tubes. I am looking for more headroom and volume ...which would you pick?
 

mangoman

Gold Supporting Member
Messages
2,278
first guess would be 6L's. Ive always heard that some 6v6's (EH??) run almost like a 6L. Also, the 5881 is a little earlier on breakup and not as loud as the 6L's.

But a great question. Subscribing to this thread.
 

JB6464

Member
Messages
5,168
If you go with 6L6's , the 7581 is the highest output 6L6 ( 35w) with headroom from hell available .
I use the Tungsol 7581's in my Soldano and love them .
 

55GibsonLPJR

Member
Messages
797
I will def work with my amp tech on a rebias for the amp.......so, 7581's as an option Hmmm, interesting! The amp is a greer special 20, and they suggested a Tung Sol 6l6gcstr pair but I was also told the 5881 tubes are warmer sounding. I really need the KICK in output more than anything. Amazing sounding amp stock but I just need some more headroom and power for the project i'm in.
 

JB6464

Member
Messages
5,168
7581 Hmmm, interesting! The amp is a greer special 20, and they suggested a Tung Sol 6l6gcstr pair but I was also told the 5881 tubes are warmer sounding. I really need the KICK in output more than anything. Amazing sounding amp stock but I just need some more headroom and power for the project i'm in.
The 7581A is completely interchangeable with any regular 6L6 with no mods needed , you just need to rebias the amp . I like to run them about 65% max dissipation .
 
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7,411
So I have a 20w amp that has 2 6v6 power tubes in it and I am going to take them out and replace them with either 6L6 or 5881 tubes. I am looking for more headroom and volume ...which would you pick?
Are you sure your amp is designed to handle 6L6 type valves safely? These draw higher heater current, have a different plate impedance and could over tax your OT if not carefull. Amps desigend for 6V6s or EL84s usually don't have so much headroom for starters and though a higher rated bottle could give you the impression of more headroom you would have to bias it colder to stay within range.

If you're looking for headroom and volume then even if you have the PT for it the OT is going to be a huge limiting factor so you may want to look into a replacement here. Then of course the plate voltage is still going to be quite low and some potential headroom is going to be lost right there.

A simple mod you could do is making sure you use a 12AT7 in the PI/ Balanced valve position. That would increase headroom in a rather critical stage in the signal path where most AX7s or other would compress or even distort.

Other than that - and I don't wish to rain on your parade - but if you want to run 6L6s or other larger glass bottles then you really want an amp designed with these in mind.
 

CRUE

Member
Messages
830
Are you sure your amp is designed to handle 6L6 type valves safely? These draw higher heater current, have a different plate impedance and could over tax your OT if not carefull. Amps desigend for 6V6s or EL84s usually don't have so much headroom for starters and though a higher rated bottle could give you the impression of more headroom you would have to bias it colder to stay within range.

If you're looking for headroom and volume then even if you have the PT for it the OT is going to be a huge limiting factor so you may want to look into a replacement here. Then of course the plate voltage is still going to be quite low and some potential headroom is going to be lost right there.

A simple mod you could do is making sure you use a 12AT7 in the PI/ Balanced valve position. That would increase headroom in a rather critical stage in the signal path where most AX7s or other would compress or even distort.

Other than that - and I don't wish to rain on your parade - but if you want to run 6L6s or other larger glass bottles then you really want an amp designed with these in mind.

This. And check with the maker of the amp, some will tell you it's ok to switch out and rebias but some amps you can't from my understanding.
 

Rumble5

Member
Messages
1,677
If you can find a speaker that's more efficient than the one currently in your amp by 3db or more, it will essentially be like doubling the wattage of your amp which will probably be safer and more effective than trying to run bigger tubes.
 

JB6464

Member
Messages
5,168
If you can find a speaker that's more efficient than the one currently in your amp by 3db or more, it will essentially be like doubling the wattage of your amp which will probably be safer and more effective than trying to run bigger tubes.
That would be good for overall volume but different if he needs more AMP headroom before the amp starts distorting .
 
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JB6464

Member
Messages
5,168
OP , another way you can get more amp headroom before it distorting is use 5751 preamp tubes .
Lower preamp gain and allows you to open up the power section more .
 




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