Modding my 66 bassman

[corduroyew]

What about using one of these http://www.webervst.com/ccap.html instead of the GZ34 tubes??? I'm just want the compression and if I can get that without the extra power suply then my life would be a little easier. Anybody have experiance with them?

[Satamax]

What about using one of these http://www.webervst.com/ccap.html instead of the GZ34 tubes??? I'm just want the compression and if I can get that without the extra power suply then my life would be a little easier. Anybody have experiance with them?

Well, there's many who've used them over here. What's nice is that you could avoid punching the chassis and solder the copper cap's legs, holding it inside the chassis with a capacitor strap. Sorry but my head is in a mess, and i haven't checked the rest of your mods. Will do when i have clearer ideas.

Bye.

Max.

[Bruce / Mission Amps]

What about using one of these http://www.webervst.com/ccap.html instead of the GZ34 tubes??? I'm just want the compression and if I can get that without the extra power suply then my life would be a little easier. Anybody have experiance with them?

In this application it is a huge waste of money IMHO.
If all you are looking for is some compression then don't waste any time with a tube rectifier socket and all that crap, just put a 10 or 15 watt 100 ohm to 220 ohm resistor right in series with your wire from the SS rectifiers to the filter cap bank.
As far as I know, all those copper cap rectifiers have in them are power resistors, thermistors and SS diodes... (possibly a 5 watt zener diode in some)
The thermistor is just used as a very slight current surge absorber when the amp is first started and what is left over.... well, you all ready have if you stick that resistor in as I mentioned.

[corduroyew]

Sounds like a much better option. Is 10 watt going to be enough do you think? Anything over 10watts get very hard to find around these parts.

[Bruce / Mission Amps]

Sounds like a much better option. Is 10 watt going to be enough do you think? Anything over 10watts get very hard to find around these parts.

Well, 15 watts would be better but let's do some simple math here....
Pretend you picked a 150 ohm resistor @10 watts for sag.
Under normal playing, I'd guess you'd frequently pull over 100ma out of the B+ rail and across that resistor.
How much sag you get would be simple to figure using Ohm's Law.
.1a x 150 Ohms = 15v of sag.
Now crank that amp up to full power output with huge massive amounts of overdrive and distortion and the B+ rail is pushing 250ma of current.
.25a x 150 Ohms = 37.5v of sag... that is quite a bit but not out of line compared to say a 5U4 or other rectifier tubes supply boat loads of high power current.

And, as far as how much power is used up in the resistor,
Ohm's Laws should tell you that power is = to current squared times the resistance.

.25a x .25a x 150 0hms = 9.4 watts.
So, you can see a 10 watter is gonna get hotter then the hubs of Hell.... but, probably not gonna fail anytime soon unless you operated the amp in 100% duty cycle 100% of the time.
But if you are worried about it, use two, 10 watt, 50 to 68 ohm resistors in series.

[Satamax]

Bruce, couldn't he put two 300Ω in parallel instead ?

[Satamax]

I've done some more modding. Here is a layout of what I've done so far. It's got the AB165 to AA 864 mod and it's got the "how to make your bass chanel sound like the guitar chanel with an extra gain stage" mod that I found on the old forum.



I had changed the balance pot into a bias pot but then found out that the plate current between my tubes was 10ma different! So they were not a very good match and it meant that (for now anyway) a balance pot is the best way for me to go. Because I have to cut into the chassis to add the rectifier tube and transformer, I think I might add another bias pot so that there will be one for each output tube.


I like it the way it is now, but I still want to figure out how to add the unused tube into the mix. I've kinda got an idea about how I might do it but I don't really know. So if somebody could give me some pointers or get me going in the right direction it would be greatly apprecitated. I'd also like to make it switchable so that I don't HAVE to have the extra gain stage all the time but if it's too dangerouse or just a stupid idea then I won't do it.

I've also converted the layout onto the schematic that Satamax gave me with the rectifier tube on it. So this is what (I think) the schematic should look like once I’m done adding the rectifier tube.

Hi Corduroyew.

Well, check thoses three links. The first one being the most important.

I think your AA864 is good, i've done that in the past, but, the Andy Ruhl mod seems beter in terms of kicking but


http://blueguitar.org/new/schem/fend...4_vs_aa165.pdf

The other two are Justin's efforts to make one.

http://music-electronics-forum.com/s...ead.php?t=3667

http://music-electronics-forum.com/s...ead.php?t=3278

HTH.

Max.