#1
So i've heard something about pulling half the power tubes in an amp head to reduce wattage, specifically it working one peavey XXX's one of which i have

how exactly does this work, how would you do it, and why does it work?

NOTE: i also recall that this doesn't really affect loudness, which is fine, it would just be preferable to do since my cab is rated at 120 watts, so be cutting wattage i could not worry about blowing speakers

thanks
Ibanez RG5EX1
Ibanez RG7321
Peavey XXX-->Avatar 4X12(2 V30's 2 G12H30's)

BARE KNUCKLE PUPS RULE!
Quote by gumbilicious
thanks for making an old dude feel like his advice is actually taken into consideration
#2
Unless you're turning your amp up to max all the time, I wouldn't worry about blowing the speakers.
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#4
Quote by AcousticMirror
Completely unnecessary.

It's completely unnecessary to run all four power tubes. Might as well save the cost/energy and run on two.
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

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#5
except when your amp isn't designed from the get go to run two. you're mismatching the transformer and causing stress on other parts of the circuit.

plus it's not a class a amp bro. if you have the volume knob down it doesn't run as hard as the volume up so the savings are negligible.
Prs se Holcomb is the answer
#7
Quote by Kanthras
It's completely unnecessary to run all four power tubes. Might as well save the cost/energy and run on two.


That's only if your amp can do it, though, which I'm not sure the XXX can do.

Besides that, more power tubes = more headroom, so it could always affect the sound in an undesirable manner if you take 'em out, so it goes both ways.
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#8
Thanks just wondering, if I'm concerned I may look into changing tho ohm on my cab
Ibanez RG5EX1
Ibanez RG7321
Peavey XXX-->Avatar 4X12(2 V30's 2 G12H30's)

BARE KNUCKLE PUPS RULE!
Quote by gumbilicious
thanks for making an old dude feel like his advice is actually taken into consideration
#10
Not on the cab. On the head. You just turn the impedance selector one click to the left, i.e. from 8 ohms to 4.
You should only pull tubes if you've got 4 push-pull power tubes. The XXX is push-pull but I don't know what model you have. Some only have two, I believe.
#12
There's no problem if you compensate for the impedance difference. The amp won't know the difference. The only parts that would be effected by the impedance change are the OT and the power tubes and by halving the impedance you're fixing that. It's as good as a new amp.

Go nuts.
#13
There's really no point in pulling tubes. My Mark IV is 85 watts. Flick a few switches (half power, triode, class A) it goes to 30 watts. So now it's at 30 watts. Still SUPER loud, and I still have to get it above bedroom level for a usuable thick tone.

Basically, if I have my amp pretty loud in my room at 85 watts, switch it to 30 watts, it DOES cut the volume significantly, but the low volume fizz and sterile tone comes back, and I have to crank the volume more to reach the volume I was at to get that thick saturated sound.

So I just leave it in full power 85 watts because it sounds better and has more punch. Plus it does have pretty usable bedroom levels anyway, as should most tube amps with a master volume.
#14
Quote by Raijouta
That's only if your amp can do it, though, which I'm not sure the XXX can do.

Besides that, more power tubes = more headroom, so it could always affect the sound in an undesirable manner if you take 'em out, so it goes both ways.


TS: You can pull tubes on the XXX. But honestly, it's not worth the trouble. You're not going to notice a decrease in volume...and it's got a master volume knob.
#15
Quote by eyebanez333
TS: You can pull tubes on the XXX. But honestly, it's not worth the trouble. You're not going to notice a decrease in volume...and it's got a master volume knob.
The "trouble" is pulling out two tubes and flicking a switch.
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

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~ BUM: For all things extinguishing

Rackmount Tube Amp Project <<< Updates!
#16
Quote by Kanthras
The "trouble" is pulling out two tubes and flicking a switch.


Still...the gain/overall result from the 'trouble' is pointless.
Last edited by eyebanez333 at Sep 30, 2010,
#17
Quote by eyebanez333
Still...the gain/overall result from the 'trouble' is pointless.
The point is, you don't notice the difference, but are using half the tubes.

Do it for the environment.
Or your wallet.
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

Bugera Users Militia. We are horrible people. With a sprinkler fetish.
~ BUM: For all things extinguishing

Rackmount Tube Amp Project <<< Updates!
#18
Some amps cant handle it. I cant give technical details but i understand older amps are better at dealing with it down to generally having better quality transformers and parts.

Running my amp like this blew the output transformer in my old Laney...

£100 + new set of power valves frankly isnt worth the 3db decrease of volume.

Besides, speakers are rated conservatively, just like amps are, especially the case with celestions, the 25 watt greenback can handle 50 watts peak. It isnt usually necissary to have a higher wattage cab than the head. On top of that when do you push 120+ watts out of your amp anyway?
#19
Quote by beckyjc
Some amps cant handle it. I cant give technical details but i understand older amps are better at dealing with it down to generally having better quality transformers and parts.

Running my amp like this blew the output transformer in my old Laney...

£100 + new set of power valves frankly isnt worth the 3db decrease of volume.
Sorry for your loss, but you must've done something wrong. Doing it properly does not increase the load on the amp. IIRC, some amps do have a power section where you can't do it (the Valveking supposedly is one of them), maybe your Laney was one of them? I can't remember what the reason was that you can't do it with VKs.
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

Bugera Users Militia. We are horrible people. With a sprinkler fetish.
~ BUM: For all things extinguishing

Rackmount Tube Amp Project <<< Updates!
#20
Quote by Kanthras
The point is, you don't notice the difference, but are using half the tubes.

Do it for the environment.
Or your wallet.


you do understand that the same signal is hitting the pi...
instead of getting fed to 4 tubes...it's now being fed to 2 tubes so those 2 tubes will now wear out
twice as fast.
Prs se Holcomb is the answer
#21
Faster, yes. But not twice as fast.
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

Bugera Users Militia. We are horrible people. With a sprinkler fetish.
~ BUM: For all things extinguishing

Rackmount Tube Amp Project <<< Updates!
#22
Quote by beckyjc
Some amps cant handle it. I cant give technical details but i understand older amps are better at dealing with it down to generally having better quality transformers and parts.

Running my amp like this blew the output transformer in my old Laney...

£100 + new set of power valves frankly isnt worth the 3db decrease of volume.

Besides, speakers are rated conservatively, just like amps are, especially the case with celestions, the 25 watt greenback can handle 50 watts peak. It isnt usually necissary to have a higher wattage cab than the head. On top of that when do you push 120+ watts out of your amp anyway?



yeah the valveking is one amp that you can't pull tubes on....the tube heaters are wired so you can't.

Quote by Kanthras
The point is, you don't notice the difference, but are using half the tubes.

Do it for the environment.
Or your wallet.


Well, right now he's already using 4 tubes, so he's not going to save any money there. Sure, he could use the pulled tubes as spares...or only buy 2 power tubes when it's time to retube. But for the reason he's wanting to pull them in the first place...theres no need to. Still pretty pointless. If it isn't broke, why **** with it?

If you do decide to pull them...just do it right so you don't **** your amp up doing something that wasn't necessary to begin with
Last edited by eyebanez333 at Sep 30, 2010,
#23
Quote by eyebanez333
^yeah the valveking is one amp that you can't pull tubes on.
Do you know why? Wasn't it something with the poweramp having a wacky topology?
Nevermind, you answered in an edit.
Well, right now he's already using 4 tubes, so he's not going to save any money there. Sure, he could use the pulled tubes as spares...or only buy 2 power tubes when it's time to retube.
Well, yeah, exactly. If you don't think that's a good reason, fine.
But for the reason he's wanting to pull them in the first place...theres no need to. Still pretty pointless. If it isn't broke, why **** with it
Why not? I love ****ing with things.
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

Bugera Users Militia. We are horrible people. With a sprinkler fetish.
~ BUM: For all things extinguishing

Rackmount Tube Amp Project <<< Updates!
Last edited by Kanthras at Sep 30, 2010,
#24
I halved the impedance and pulled one tube from each pair.

IIRC, i did nothing wrong in the process.

It wasnt an instant thing, i ran it like that for a month or so, till one day at band practice it overheated, the channels were switching themselves, and all the volume died.

Most companies reccomend against this in the first place (Laney does...), get in touch with peavey. Ask them about it rather than trusting some random strangers on the net. If they reccomend against it, then be weary they arent going to be very willing to repair it if you try it out and something dies.

As far as i can see if an amps designed to see 4 output valves, it isnt going to be very comfortable seeing two empty valve sockets.

This is probably the reason my vc died.

To everyone, never pull tubes on a Cathode biased amplifier unless the manufacturer says you can.

The reason is, if all 4 tubes share the same cathode resistor,
this value will be too low for 2 tubes.
AC30= 50 ohm resistor for 4 tubes.
You would need a 150 ohm resistor for two in this amp.
#25
Here's what Roger Crimm (Peavey Customer Service) recommended to do with the XXX on the Peavey forum:

We recommend that you remove the two outside power tubes and reduce the impedance setting on the amplifier to one value below the rating of the speaker cabinet.
For example, set the impedance selector to 8 ohms for a 16 ohm enclosure.
#26
Quote by beckyjc
I halved the impedance and pulled one tube from each pair.

IIRC, i did nothing wrong in the process.

It wasnt an instant thing, i ran it like that for a month or so, till one day at band practice it overheated, the channels were switching themselves, and all the volume died.
Doesn't sound like pulling the tubes was the cause of your problems, tbh.
Most companies reccomend against this in the first place (Laney does...), get in touch with peavey. Ask them about it rather than trusting some random strangers on the net. If they reccomend against it, then be weary they arent going to be very willing to repair it if you try it out and something dies.
Most companies also tell you there are no user serviceable parts inside amps. I don't think most companies give very reliable information concerning this kind of stuff.

If you look up schematics of these amps where you can do it, you'll see the power sections should work perfectly fine when you pull tubes (provided the bias is still safe). Unless the heaters are wired in series, like in the VK.
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

Bugera Users Militia. We are horrible people. With a sprinkler fetish.
~ BUM: For all things extinguishing

Rackmount Tube Amp Project <<< Updates!
#27
Becky, your amp died because it's cathode biased, and the power tubes shared cathode resistors. That's why you can't pull tubes from cathode biased amps, because it will increase the current delivered to the tubes and you'll blow them out.

Fixed bias amps do not share cathode resistors so you can pull as many tubes as you like, provided you compensate for the impedance change. You can actually pull three tubes out of a four tube amp if you like, though it won't sound very good.
#28
Yeah thats what i was saying by the quote i posted.

Most companies will say dont do this or this to save their ass incase you break something/kill yourself, not just to be dicks, imo.