Pulling 2 tubes question

[core9]

I'm running a Matamp Green Legend and a new GT120 in stereo.  The GT is wayyyyy louder than the Legend, not sure why but whatever. I want to push the GT harder so my question is if you pull 2 tubes you are essentially cutting the power in half.  Which also means you have to cut the ohm's in half as well.  Here is where the problem lies.  I'm running it into 2 8 ohm cabs.  That would mean the amp would have to be set at 2 ohms correct?  Obviously the amp only has 4,8, and 16 selectors.  Any suggestions?

[Hemisaurus]

No it's actually the other way around. You pull two tubes, you want to half the current being pulled on the tube side of the transformer, so you have to double the impedance on the speaker side. I know this is a poor explanation but I'm short of sleep  

Anyhoo, your 4/8/16 selector is now an 8/16/32 selector which gives you a problem, you can no longer safely use 2 8 ohm cabs.

My suggestion would be, use one cab, and google a better explanation of what I'm saying, because re-reading what you said, and what I said, we said the same thing in different ways. Yes you'd need a 2 ohm setting on your amp, which would now be the 4 ohm settiing because of the two pulled tubes. Italicized the previous bollocks

Or, make a special serial speaker cable, so that your two 8 ohm cabs now present a 16 ohm load, and use what used to be the 8 ohm setting on your amp.

[black_out]

How would you go about making a serial speaker cable, Hemi? I can't find any tutorials on the interwebz.

[Instant Dan]

Have you thought of experimenting with lower output tubes? At worst, an attenuator?

[Hemisaurus]

How would you go about making a serial speaker cable, Hemi? I can't find any tutorials on the interwebz.

OK, I'm going to assume you don't know how to solder, not to be offensive, but because this is actually how I did it last time I made one.

You need 2 wire couplers of some kind, I used the little screw terminal ones you can get at radioshack, you could probably get away with using the ones people use for wiring your house, I just don't like 'em myself. If you can solder, replace the wire couplers with a solder joint.



Also 2 speaker cables, actually one and a half will do.

Open up the jack on one end of one cable, lets say the white wire goes to the tip, and the black wire goes to the shield.

Take the other cable and cut it, so that you now have a length of cable with a jack on one end and bare wires on the other.

Pick the point on your first cable that you want to attach this second cable, if it's a flex just cut the white conductor, if it's fully jacketed carefully peel off the outer insulation of one section and expose the white conductor and cut it.

Bare both ends of the cut conductor.

Attach the extra half cable to these bare ends, using your wire coupling device.

This is the tricky bit, to get the polarity of the speakers right, where the white conductor of the second cable is joined to the black conductor of the first cable (shield to tip) these are the ends to use on the speaker cabs. The other end should go to the amp. You can double check this by using a 9V battery on the remaining end, and check all the speaker cones move in the same direction.

If anyone cares to do a better guide for this, make some pictures or something, that would be awesome, we could put it in the tech thread.

Found this old pic I knocked up to show how to wire one Speakon to 2 1/4" jacks in series. Imagine that top speakon is the 1/4" jack that you plug into your amp.

[black_out]

Have you thought of experimenting with lower output tubes? At worst, an attenuator?

A lower output preamp tube would probably be your best bet. You can swap out the V1 preamp tube on you head with a 5751 for a ~30% power reduction.

http://tubedepot.com/nos-5751jan.html

[Hemisaurus]

An attenuator might be a better bet than a different preamp tube, if as he says he wants to be able to push the amp harder. Adding in a less gainful preamp tube will make the amp sound cleaner. Parts Express have dummy loads designed to replace speakers, using a 4 ohm load in series with his 2 8 ohm cabs would also drop half the power rather than yanking out or replacing tubes.

[core9]

Have you thought of experimenting with lower output tubes? At worst, an attenuator?

A lower output preamp tube would probably be your best bet. You can swap out the V1 preamp tube on you head with a 5751 for a ~30% power reduction.

http://tubedepot.com/nos-5751jan.html

Actually Hemi this might be the answer, I am using a fuzz, so it's not really about getting the amp dirtier, it's just that I want to push the tubes a lot harder than they are being pushed right now.  As it is, I barely put the volume over 1 and I have it on the low gain input...and it is eating my other amp alive.  I might have to try a different preamp tube...thanks guys.

[Hemisaurus]

Ah, I thought you were pushing it to make it break up more

[Blueberry Lazer]

Not to rain on anyone's parade, but when I ordered my Electric amp I asked them about pulling 2 power tubes and they said "We never recommend pulling 2 tubes for lower output in our 4 tube amp units.  That is very tuff on output transformers.  I have replaced alot of output transformers on HIWATT, MATAMP
and ORANGE because dudes do that."

This was pretty shocking to me because I have ran my 5150 with 2 power tubes for a few years now. I will probably continue to run my 5150 with 2 but not the Electric. Just to be safe.

[SpaceTrucker]

^Thats a peavey for you.

Marshalls are loud and delicate like a woman.

[VOLVO)))]

Looks like I'll be coming over to PC for band practice, then. hahaha.

[Hemisaurus]

Not to rain on anyone's parade, but when I ordered my Electric amp I asked them about pulling 2 power tubes and they said "We never recommend pulling 2 tubes for lower output in our 4 tube amp units.  That is very tuff on output transformers.  I have replaced alot of output transformers on HIWATT, MATAMP
and ORANGE because dudes do that."

This was pretty shocking to me because I have ran my 5150 with 2 power tubes for a few years now. I will probably continue to run my 5150 with 2 but not the Electric. Just to be safe.

I wonder if that's from people that pull the tubes, but don't realise they have to change the impedance selector to compensate

[Blueberry Lazer]

Yeah they didn't specify, but it concerned me.

[Hemisaurus]

I can't recall anything funny in the basic Orange schematic that would prohibit it, BUT I'd always recommend following a manufacturers recommendations above all else, for their own products at least.

Now I got to go and look at more schematics, again Oh wait, there aren't any Electric schematics  

Plus popping two tubes, doesn't really make it that much quieter, 3dB or so isn't it, or 6dB, something like that. Either way 3dB is barely audible volume wise. Personally I'd use less speakers, if you've got a 4x12 capable of stereo, run half of it (and remember to change the amp impedance selector) 2 12"s are quieter than 4, 1 is quieter still. I had a buddy used a 4x12 with his head live, and a 1x12 (Marshall FWIW) for jamming and stuff, and he got the same sound, just quieter. Now the other two guitarists are off buying 1x12's.

You could fit a switch in your 4x12 to turn it into a 1x12, and then you wouldn't even have to change the impedance selector.

[Blueberry Lazer]

Looks like I'll be coming over to PC for band practice, then. hahaha.

Anytime bro. Lets make some doom step!