Toggle sidebar Toggle sidebar
  • You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
  • The Retevis Holidays giveaway winner has been selected! Check Here to see who won!

how much drive into an old tube amp w/ straight 4 x 6LQ6

M

mr_fx

Sr. Member
Oct 8, 2011
1,536
172
173
Kansas City
how much drive into an old tube amp w/ straight 4 x 6LQ6

Further more what kind of power out should a 4 tube 6LQ6 be putting out?

I have heard 100, 150, 200, 400, 500, 600, and even 800. so I really just don;t know

My buddy swears up and down any more than 3-4 watts on SSB will kill it. But most old sweep tune amps had a driver (i.e. 1x2, 1x3, 1x4) I know my buddy has an old Palomar Skipper 300 (1x3 6LQ6) and he claims 450 on SSB with only 4 watts of drive... I tried to explain that a straight 4 is a totally different animal and that the driver is most likely pumping 20+ watts into the 3 final tubes... but he does not seem to get it
 
  • Like
Reactions: Busboy

mr_fx -

I have an old boat anchor tube amp, an SBE SB2-LA. It uses six 6JE6 tubes operating Class AB1. SBE rated this amp at 1000W SSB, 300W AM, or 400W FM/CW, with 65 watts drive (maximum). To get the advertised output, I had to change the input impedance of the amp from 75 to 50 ohms. A little math shows that (maxed out) it's doing 166W per tube in SSB, and 50W per tube in AM, with roughly 10W drive per tube. I never drive it that hard. Usually 30W drive for 500W out in SSB.
If your amp is Class C grounded grid, then the input and output figures will vary slightly. However, since the 6JE6 and 6LQ6 tubes are interchangeable, the numbers for the SBE amp should be in the ballpark. 73s

- 399
 
For me, a good rule of thumb is 5 watts input per tube with 6LQ6`s, so I would limit it to about total 20 watts (pep) drive for SSB use.
AM is real tough on old sweep tubes, even 6LQ6`s....and they are a very robust tube.
I would limit AM dead key to 100 watts and no more than 400 watts total output.
They "can" handle almost 200 watts of plate dissipation for a short period of time, I think GE said not to exceed 30 seconds.
The thing is, they are really getting hard to find in good shape, and expensive.
Anyone running sweep tubes now should limit the drive just to keep them alive as long as they can.
You used to be able to get these tubes for around 8 dollars each at the local store, so it was not a big deal to lose one, but now.....


73
Jeff
 
That is really cool and I never thought about stock somewhere outside of the US.
I got rid of my 300A ( i considered it a very good amp) because sweep tubes became too expensive, and I have passed on many good deals on sweep tube amps because of the same reason.
The only tube Amp i run now has 811`s in it because the are very reasonable in cost and easy to get.
I even sold off all of the spare tubes I had, String-bean here on the forum got the last few that I had.
Kudos, If I were you, i would stock up on a few spares.


73
Jeff
 

dxChat
Help Users
  • No one is chatting at the moment.


      Top Bottom