Who pulls a pair of tubes on their 100w Splawns?

skullfxr

Well-known member
I have ran my Nitro, QR, and PM for probably longer than 10 years with just two power tubes (half tubes thus half ohms) . Still a shit ton of power and bottom end. No complaints. At the time I liked it. So I just put a quad in the QR and thought it was just about the same, pulled two of them, and decided to keep it at one pair.

What do you all do/think?

If you have not done such, I recommend giving it a shot and see what you think. Let us know what you think.

DISCLAIMER: pairs are either inner or outer, bias up if you are going to keep it that way.
 

War_in_D

Active member
I'm assuming these are Splawns that do no have the half power switch? Would be interesting if you could pull a pair of tubes, and then hit the half power switch. Would theoretically make it a 25 watt amp, and you could really get those power tube cranked up and hot! LOL
 

311splawndude

Well-known member
I've been running my 100w QR in half power mode for a long time now. I couldn't really tell a difference either. I have more bottom end and power than I need. I figured a little power tube distortion is not a bad thing (for what I'm doing) but more importantly - I like to save on buying tubes where I can though primarily.


I'm assuming these are Splawns that do no have the half power switch? Would be interesting if you could pull a pair of tubes, and then hit the half power switch. Would theoretically make it a 25 watt amp, and you could really get those power tube cranked up and hot! LOL
Take this with a grain of salt as I may not be 100% on this -as it has been probably 10 years since Scott told me this but here is what I remember of it.

If you take a 100 QR and flip the switch to half power it will disable the two outer pair tubes and you can play at half power with all 4 power tubes still in the amp. Temporarily. Like for some songs. Or a gig.

If however, you want to run like that all the time then go ahead and pull that outer pair out and rebias the amp (if needed).

So there is no 'doubling' affect to get to 25 watts. In a Class A/B amp like this the power tubes work in pairs as far as voltage. Come to think of it, I don't think I've seen an amp that can run on a single EL34. I'm sure there are some Class A amps out there that can though.
 

kmanick

Active member
I've always wondered why smaller amps go to el84's and not just a single El-34, is there a reason that power tubes need to run in pairs?
 

311splawndude

Well-known member
There are some amps that can run on a single power tube. I think Class A amps can if designed to do so. I'm not an EE nor a Tech though. There are some good resources and websites out there I just can't think of them at the moment.

What I remember is that Class A/B amps (like most of the amps we talk about on these forums) run in a push-pull fashion which means the voltages get split in half and then combined again in the output transformer for the ultimate signal going to your speaker.

That said, I still can't think of a Class A amp that runs a single EL34 but again I'm sure there are some out there.
 

War_in_D

Active member
I've been running my 100w QR in half power mode for a long time now. I couldn't really tell a difference either. I have more bottom end and power than I need. I figured a little power tube distortion is not a bad thing (for what I'm doing) but more importantly - I like to save on buying tubes where I can though primarily.



Take this with a grain of salt as I may not be 100% on this -as it has been probably 10 years since Scott told me this but here is what I remember of it.

If you take a 100 QR and flip the switch to half power it will disable the two outer pair tubes and you can play at half power with all 4 power tubes still in the amp. Temporarily. Like for some songs. Or a gig.

If however, you want to run like that all the time then go ahead and pull that outer pair out and rebias the amp (if needed).


So there is no 'doubling' affect to get to 25 watts. In a Class A/B amp like this the power tubes work in pairs as far as voltage. Come to think of it, I don't think I've seen an amp that can run on a single EL34. I'm sure there are some Class A amps out there that can though.

Hmm, I wonder if this is true? My Quick Rod stays on half power all the time, I might need to look at pulling the tubes and rebiasing.
 

311splawndude

Well-known member
Hmm, I wonder if this is true? My Quick Rod stays on half power all the time, I might need to look at pulling the tubes and rebiasing.
Pretty sure.
Again, not an amp tech.

You'll notice when on half power the outer 2 power tubes are still lit up. That is because the voltage 'heaters' are still active. I believe that would simply cause undo wear on the tubes and not hurt the amp. But if you've ever heard of 'tube poisoning' it would be similar to that. Like if you leave your amp on for long periods of time? Not good for the power tubes in the long run. You won't hurt the amp doing that though I'm sure. But rebiasing will help on tube life and could change the tone a bit.
 

hitmanguitar79

New member
Have a QR from 2008, always ran in 50W mode. Plenty of sound from it. Only uses the two inside power tubes, outside sockets stay empty on mine, flip the switch to half power mode. One thing I will say about Scott is he will give you more ideas and info about his amps, pretty cool you can call the phone number and get the guy himself.
 
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