7591a tube

[stanb]

has anybody used a 7591a for a power tube ?
what would you need to do to put them in a 18watt lite??
I have some stereo amps with 7591 that I could use
my 18watt liteIIb has octal sockets wired for 6v6

stanb

[Shrapnel]

http://www.nj7p.org/Tube4.php?tube=7591A http://www.nj7p.org/Tube4.php?tube=7591A

See there for the data on your tube/valve.

Can't seem to locate a replacement type other than the 7591.

[PeterS]

They have a unique pinout so you'd have to rewire tube sockets for them. Really they should be more popular than they are --- a pair gets you 25 watts or so, just the right size for a bar gigging amp, and in the gap between 6V6 and 6L6...

[morcey2]

I built a plexi with them and I really like it. It puts out about 30 watts. I think they would sound awesome in a 18-watt lite type circuit and plan on doing that someday. They have a higher voltage gain than most of the other octals, more like the EL84, so the stock PI should work quite nicely.

Matt.

[Shrapnel]

According to the link I gave earlier, they gave the basic specs for Cathode Bias 28watt P-P, & Fixed Bias 30watt P-P, Fixed Bias 45watt P-P, and [Fixed Bias] 11watt SE. RCA Recieving Tube Manuals RC23 & RC25 confirm. (My Sylvania manual would need to be dug out to double check with it.)

I'm sure there's a way to get it into the 18watt zone.

Double checked in my 1964 SAMS Tube Substitution Handbook and the only sub mentioned there was a 7591A for a 7591 (and not vice-versa.)

[jimipage33]

my recipe:

plates at 450v
screens at 400v
cathode bias resistor at 180-200 ohms
bypass cap at 100 - 220uf

solder neatly
serves a clubfull

[StarGeezers]

That is a very interesting tube , affordable too...Hmmm?

[tubetek]

"AFFORDABLE??"
Only if you use the EH/SOVTEK modern "equivalent"
The originals are priced like GE6550a or GEC KT88. They are/were a GREAT tube used in the outputs of countless stereos (Pioneer, Fisher, etc.) and many AMPEG combo guitar amps. Many years ago, a group of people from "overseas" bought up virtually all of the remaining stocks...Prices went up accordingly. Until recently there was no substitute/replacement. In my limited experience, the EH tube works well but doesn't hold a candle to the originals (in my Fisher 500C) Haven't tried to build a new amp with 'em, though.
Tom

[StarGeezers]

Tube AES has the JJ 7591s for 15.50 USD...

[PeterS]

I've used the JJ 7591 in a Gibson amp, they sound fine, although they are somewhat microphonic, so I put O-rings on them...

[stanb]

thanks guys I just mite try it , I have a fisher 500c , scott , and a sansui
tube amps with good tubes and Iron . they all use 7591a out put tubes,
my fisher 500c is my main stereo, nothing plays back good guitar made with good tube amp than a tube stereo.
so the PI in the 18watt liteII has gain to power the 7591. I was thinking
I would need to lower cathode res. or maybe the tail res.

stanb

[Shrapnel]

my recipe:

plates at 450v
screens at 400v
cathode bias resistor at 180-200 ohms
bypass cap at 100 - 220uf

What kind of output power do you figure you are getting with that recipie? 6k6 primary?

[Alexo]

my recipe:

plates at 450v
screens at 400v
cathode bias resistor at 180-200 ohms
bypass cap at 100 - 220uf

What kind of output power do you figure you are getting with that recipie? 6k6 primary?

Those voltages will get you 45 watts in fixed bias, but you have to go a little more conservatively on the screens (slightly lower voltage, larger screen resistors) in a guitar amp or else they will glow, at least that's my experience. Check the RCA datasheet for cathode bias values, I think they recommend a higher primary Z and you'll of course get less power out. These tubes can sound fantastic though.

[jimipage33]

my recipe:

plates at 450v
screens at 400v
cathode bias resistor at 180-200 ohms
bypass cap at 100 - 220uf

What kind of output power do you figure you are getting with that recipie? 6k6 primary?

Actually using OT's with a 4k2 primary, but running them at 8k4. I'm guessing upwards of 30 watts. Believe me, it's plenty loud.