Plucking Tubes

Theoretically it is possible to pull a pair of tubes, but you must a) pull the correct pair of tubes, and b) flip the impedance selector switch to half (or was that twice?) of the cabinet's rating.

Unfortunately, the amp will still be very very loud, and you still won't be able to drive it into the distortion you seek....I have a V4 myself.

So, it's not a good idea. There was a thread that discussed this a month or so ago, Passinwind made some good observations....

 

...buy a headphone amp...

~S~

 

Power brake!
http://www.musiciansfriend.com/srs7/g=home/search/detail/base_pid/483191/

 

you should look for a Ampeg master volume pedal on ebay, or search on usedampegs for directions on how to make one.

it plugs into the external amp jack and lets you turn down the 'master' while cranking the volume on the amp. its like having a master volume mod without hacking the amp.

why not just use a good overdrive pedal?

 

Jesus people, master volumes and overdrive pedals do not get power tube overdrive!!!!


What I might suggest are looking into a ZVex Nano Amp, it's a 1/4 watt clean, and a full one watt cranked. And all tube. Only about 400 bucks new too, I think.

 

the amp uses 4 power tubes, right?
you can certainly pull two of them.

the output transformer matches a primary impedance to a secondary. let's call the primary "X" for now. do you know what load your amp is running now? I'm going to assume 8.

If the transformer is currently giving the ratio X:8, when you pull two power tubes, you'll want 2X on the primary.

this can be achieved by taking your 8ohm load and putting it on the 4ohm jack.

if you normally use a 4ohm load, you can switch ot the 2ohm jack. (shown on the schematic, your amp does have this, right?)


Additionally, make sure you pull the correct tubes!!!

according to the schematic, you can pull
EITHER V5 or V6
AND
EITHER V7 or V8

(so pulling V5 and V8 is fine... don't pull V5 AND V6)


yes, this will cut your power in half (possibly a bit more), but it probably isn't as much of a volume decrease as you're hoping for... give it a shot and see if it's ok.


shelling out 400 bucks for a nanohead is really pretty pointless.

a marshall powerbrake is a terrible design too. (if you're going to the attenuator route, your best bet is a weber product... either the load dump or the MASS...)

see if pulling two tubes (and changing the output impedance setting) does it for you. if it doesn't, there are other things you can do. (especially if you can move t a single less efficient speaker).

 

What about a THD (i think?) hotplate?

 

a thd hotplate is another insanely expensive idea.

if you're going the commercial attenuator route, you should drop to two power tubes first... it'll stress the attenuator less.

anyway, the hotplate isn't really the most reactive load on the market, so it's like sticking a big (adjustable) power resistor as a load to eat up some wattage.

IMO, at that point, the weber load dump is a much better (and cheaper) alternative.

 

Was just making a suggestion, ive never looked at the Weber, never had to worry about volume myself

 

Matt H,


I used to be in the electronics game many years ago. Building and repairing commercial and ham stuff. Changed careers many moons ago but still have most of my stuff except my tube tester as I knew i would never need it again Just took up the bass and am loving it. Have been bitten by the tube bug and am looking at at a bassman or a Ampeg v4 to rebuild. Just wanted to thank you for your very informative posts; I have enjoyed and learned much by reading them.

Thanks

 

Tom, thanks for the kind words. this if the first i've been on the board in over a week, and i find your message today! ha!

anyway- i think it's hilarious you're from the cape, that's where I am (from and currently) visiting my family for the next few days.

i actually have a couple of tube testers, unfortunately, they're at home. hehe