Anyone try this?
Ok, I'm going to open up this old discussion again-pulling tubes.
I've had a 5150 head for a few years now. I don't play out and I'm not in a band...so why have a 5150 and 4 x 12? Don't ask, you know how it is. Anyway, I've never been able to play the damn thing really. Well, a couple of times for a few minutes, only to have a neighbour show up at my door. So I bought a Pod, went through the learning curve, found some good sounds with it, and used the power section of my 5150 to power it to the 4 x 12 and play at tv volumes using, you guessed it, the 5150 model from the Pod.
Anyway, I was bored tonight and was cruising around the HC forums when I stumbled upon the old pulling tubes discussion. Did some digging, read a lot of old threads, remembered VHolic who used to post here, and he was running one of his Marshalls on 1 tube. So, I did it, I pulled the power tubes from the 5150, leaving only 1 in there, and I have to tell you, it works! I played for about 90 minutes tonight on 1 tube...no smoke, no overheating, no funky issues going on. The 5150 sounds pretty much the same and behaves pretty much the same except the volume is much more manageable. I've got a delay and EQ in the loop, with the Phase 90 in front. My post is on about 3 and the volume is very reasonable, like a loud tv volume. Let me tell you, one tube can be really loud, because anything past 3 on the post and it gets really loud again. I think I've found a way to use my 5150 at home now. I'll try again tomorrow and keep a close eye on it. I kept a close eye on that single tube tonight and it seemed fine, looked fine etc.
So what do you think? I can't post clips as I have no mics or recording software, but trust me, it sounds like a 5150, or as good as one can sound without moving some serious air.
Am I crazy doing this?
you could also try an attenuator. Check out the mass 150 from www.tedweber.com, its what i use and its great!
Yes, go with an attenuator. I use a THD Hotplate on my 5150 combo and it works very well.
I'm surprised that it works at all with just one tube.
I have run a Marshall head many times with just two tubes in it instead of four. My understanding is that one tube is "pushing" while the other is "pulling". So, with a four-tube head, you pull out the outside pair of tubes and knock it down to fifty watts from 100. I don't know how the Peavey is working at all with just one tube. It must work differently from a Marshall.
When you mess around with the power section of an amp, you always run the risk of blowing up the power transformer. That's basically like blowing up the engine in your car, it can wind up costing you lots of money. I might be able to pull out some spark plugs from my car and have it run "fine" on just one cylinder, but I'm taking a big risk by doing it.
As far as attenuators go, I've always enjoyed the Marshall Power Brake. A lot of people hate them because they seem to change the sound of the amp, but it's never been a big problem for me. I usually just have to dial the bass down a bit.
I already have a Weber Mass 100 and stopped using it because it sounds terrible at tv volumes. The one tube in the 5150 sounds much better. I also did a lot of research before pulling the tubes and according to many knowledgeable people, running a push/pull type amp. I'm thinking specifically of someone like Kevin O'Connor at London Power. Here's his take on pulling tubes:
Q: In a magazine Q-A, a player wanted to pull tubes to reduce power, but the "expert" said this would cause a meltdown of the remaining tubes. Of course, it was suggested that the expert's attenuator product was the preferred way to go. Is any of this true?
A: This is a person who should know better!
Removing tubes from a multi-tube fixed-bias output stage is never a problem. You can remove any number of tubes, and yes, that means you can take one tube out of a two-tube amp; one, two, or three out of a four tube stage, et cetera. This sounds heretical to techs stuck in the mire of convention, but it is something that has been known since tubes were invented.
The even-number tube extractions reduce power symmetrically. Neither the tubes nor the transformer will be damaged. Power will be reduced and so will frequency bandwidth - you will lose some bass and some treble. This is the point that switching the impedance selector to a less-than-load setting is supposed to correct, but it is completely subjective whether you should. The only 'should' of the matter, is do I like it this way, or do I like it that way?
In the uneven tube extractions, asymmetric power reduction occurs. Conventional thought says "the one tube on one side of the circuit will be trying to match the output of the two tubes on the other circuit half". This is wrong. The single tube can only produce so much power, and that's all it does. It doesn't melt down. The transformer does not blow up.
So, what's missing from conventional thought? The realization that tubes are "self-limiting power governors", which was stated in The Ultimate Tone (TUT), and explored in more detail in TUT2 and TUT3. TUT4 explores all of this in great detail. Our "expert" should get a copy.
In the end, you can pull tubes to reduce power, unless the amp is cathode biased - then you have to split the bias resistor. In any case, you do not have to worry about the impedance selector either.
Seems to be working for me so far. I'll keep a close eye on the amp and continue using it this way for now. Keeps me busy and out of trouble at least, and I'll save some money on tubes or other attenuators.
You already know more than I do about it, so I'll shut up now.
Have you ever tried it without any tubes? I have. It's really quiet that way!
Originally Posted by Bullwinkle
Quiet and killer tone! LOL! Actually, I know absolutely nothing about the inner workings of an amp other than what I read from experts. I know how to change tubes in my 5150, and I've used an attenuator, that's about it. I'm not happy with the Mass 100 and 5150, but maybe other attenuators sound good? So I did some research and gave it a shot. So far so good. And that one single tube is still plenty loud if I go past about 2 or 3 on the post. I think it's 30 watts with just one tube, which is still very loud, but I have managed to find a sweet spot on the post gain that gives me good tone at tv volumes, whereas with all 4 tubes I could never hit that spot, it always went from crappy sound at 1 or lower to absolutely way too much volume and no in-between.
Anyone else willing to give it a shot? I'd be interested to hear other experiences.