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I kinda like the idea of a guitar amp using the 6BQ6 but don't know where to begin. How much B+ could I put on this thing? What would it like for a primary impedance in push pull? Could you do Ultra Linear? Etc,etc. I just think a 100 watt or so bass amp head with top cap style tubes would look really cool and be something no one else has.

Don

This might help:
http://www.diyaudio.com/forums/showthre ... did=105724

Cheers!

I must have been waaaaayyyy too sleepy, I saw 6BQ6 but read it as 6BQ5 Duuuhhhhhh.......

So, I'll erase the past, and start over again.

The 1965 ARRL radio amateur's handbook had a 6BQ6 modulator construction , it ran a B+ around 300-325V, and the OPT was 4K CT. Standard pentode mode, cathode biased. Good for around 40 watts.

If you can locate some EL36s, so much the better...

FWIW, the 6BQ6 and 6AV5GA have nearly identical operating characteristics, though the 6AV5GA apparently can take higher power operation in stride.

For a PPP output stage, a 1.9 or 2K CT OPT would be good, and give you about 70-80 W out.

Going along these lines, probably just about any decent horizontal sweep tube will do the job. I've got several 6GT5s and 6GE5s, for future experiments in sonic terror


Any decent driver / LTPI should be able to handle either 6BQ6 or 6AV5GA .

/ed B

6BQ6 are a bit wimpy for a 100W Bass Amp.
If you really want a top cap tube for 100W of bass then 2 tubes come to mind.
The 6CM5 (EL36) and the 6DQ6B. A quad of either of these tubes will give you 100W whereas you would need 8 6BQ6 for 100W.

There should be plenty of 6CM5 circuits around - there are probably some on the link below. I have an old Philips Guitar Amp sitting on the shelf waiting for a repair/restoration which managed 150W from 6 off 6CM5

Here is some data and a vintage OZ Circuit for 6DQ6A
http://ozvalveamps.elands.com/6dq6generic.htm

The link to 6DQ6B Class AB1 Operating Conditions at that page clearly shows that you can easily get 70W from a pair of 6DQ6B so you should manage 140W from a quad.

Cheers,
Ian

Thanks guys! I will definitely look into those options. There is a local antique dealer who has 1000s of tubes and sells them for the prices in the Antique Electronics catalog. 6BQ6 goes for $3.85, sweet!

I prefer fixed bias just because of how easy it is to adjust the operating point but it does have its weaknesses for sure.

This one is going on the back-burner for a while because it's summer, which is not tube season but TR6 season



Don

Then you need to have tube sounds in the TR6

Back in the very early '70s I had a '64 Austin Healey Sprite (same as MG Midget). It was fun, but kinda scary, tooling around the Big Sur highway and being just about the smallest thing on four wheels. It was a fun diversion from "playing Army" at Fort Ord. It was definitely the most "bare bones basic" car I've ever owned...

/ed B

I've been thinking about making a 120W+ amp with a pair of 6DQ6's (for bass and guitar use)... they're nice because they're plentiful and cheap (about $6 each most places) and they only take 1.2A heater current, unlike their bigger sweep bretheren. Plus they were used to great effect in Australian guitar amps in the 60's.

This is the power supply I'm planning on using:
(bad schematic removed - see update below)
This gives you 165V for the screen, 330V for the preamp tubes and 495V for the plates; with a 5k p-p load a pair will put out about 70W at these voltages (I'll use 2 pairs and a 2k5 ~150W OPT, probably have to be custom as the standard 1k9 is too low). The transformers are either three 75VA 1:1 isolation types or a custom 1:1:1:1 toroid.

HI,

The way you have it drawn you have three 165 volt supplies . The negitive links need to be removed between the supplies and the the negitive end of the 330 volt supply needs to be tied to the positive of the 165 volt supply and the negitive of the 495 volt supply needs to be tied to the positive of the 330 volt supply . Very good Idea .

Mark

Of course you're right... I need to check a little closer before I post things . This is what I meant:

Speaking of 6DQ6 (and its derivitaves), I found this triode-strapped data for the 6DQ6A:

Use an SE OPT with a 3K to 4K primary:

gm = 4.4 mA/V
rp = 1000 ohms
mu = 4.4

They like to run with a plate to cathode voltage differential of about 260VDC, and 60 mA curreht..


For fixed bias:

VP = 260V
IK = 60 mA
vg1 = -45V
PO = 3.4W

For cathode bias,

VP = 305V
IK = 60 mA
RK = 750 ohms, bypass with 100-220 uF / 100V.
PO = 3.4W

Similar in function to 6B4G, 2A3, 6A3, 6A4G, etc. Pseudo-SET on the cheap...

6AV5GA, 6BQ6GA, 6GE5, 6GT5, 6GV5, etc will behave similarly.

Try them in UL SG mode for even more power output!

/ed B

Don't hang around here much lately but I happened to run across this thread. Check this out. Might be of interest:

http://www.vacuumtubes.com/6BG6.html