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F'n cool!


ps won't the speaker mags wipe/damage the VHS tapes?
 
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How much does this differ from a JCM800 2203 running 6550's, in terms of output? We figure my bandmate's 2203 is about 180W haha.
 

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Yeah, you're going to ruin your copy of Dr. Doolittle!

Freakin' nice way to do it, though. Congratulations!
 

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Well, the 2203 has a 100w OT and the Major has a 200w OT and 650v plate voltage.
There's a huge difference in wattage between the two amps.
My '83 2203 has the same OT (to my knowledge) but measured 120W when it had to get serviced last. I also wouldn't doubt that the 200W rating of the Major is a conservative number haha. That being said, my 2203 (EL34) needs to be at 8 on the dial to match the volume of the 6550 powered 2203 at 4.

I don't know if the OT of my bandmates 2203 is stock either, come to think of it.
 

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How much does this differ from a JCM800 2203 running 6550's, in terms of output? We figure my bandmate's 2203 is about 180W haha.
My '83 2203 has the same OT (to my knowledge) but measured 120W when it had to get serviced last. I also wouldn't doubt that the 200W rating of the Major is a conservative number haha. That being said, my 2203 (EL34) needs to be at 8 on the dial to match the volume of the 6550 powered 2203 at 4.

I don't know if the OT of my bandmates 2203 is stock either, come to think of it.
The 2203 is a hundred and change at best (quad of EL34s can't do more). Even if you switch out the power tubes for 6550s you're not doubling the power since you'd need to change the circuit (not just the bias) to get all the power the 6550s can put out. What you will get is more headroom and a different character. Now it is possible that the amp was fully converted (it would require a new OT, yes), but unless you're using the same cab/speakers on both amps the gain knob comparison proves nothing (speaker efficiency differences can easily explain the volume matching you describe).

Also, the Major is ultralinear and the 2203 isn't. If just a basic tube switch then it is still probably about 100 watts, if done proper (expensive; not sure worth it unless the OT was toast anyway) then it would be more, but it is rather unlikely that it was converted to proper 6550 ultralinear mode (much more expensive OT) to match the Major's output (and tone) unless someone was literally trying to convert it into a Major/Superbass power section. Possible but unlikely.
 

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@Granny Gremlin like I said, my 2203 was measured at 120W. I trust the guy who keeps Monster Truck going when he says what my amp puts out.

As for the comparison between the 6550 and EL34 2203's we use - we both run stock orange PPC412's rewired to 4 ohms. Both heads are the Canadian CSA models without 16 ohm taps. He definitely has more headroom, I'm just wondering if he has a lot more wattage. I'm not sure how he would have twice the headroom at a very similar wattage.
 

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@Michael R/T thank you for the information!

Would you be able to answer the question of headroom regarding my bandmates 6550 loaded (and we don't know what other changes) CSA 2203 versus my stock EL34 CSA 2203?
 

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The only difference will be the tone but as far as headroom they should both have the same amount.
It's not an absolute 50% in terms of being measured, but he runs his head at 4/10 and I run mine at 8/10 for the same perceived volume.
 

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There's any number of factors that could cause that. Speaker differences where just the first thing off the top of my head. Could be the preamp tubes. Also how hot is the signal coming in (pedals; boosts); yours vs his? Is one of you running compression (which can make something psychoacoustically sound louder)? Remember that 4 or 8 of 10 is the preamp gain. The list goes on.

If you really want to get to the bottom of this and understand how great the difference is due to the power section change, use a pedal as a preamp and try going in to the return fx loop jack on your amps (bypass the entire preamp). Use the same PI tube (is there a tube-driven buffer on the FX loop? if so that too) and cab when doing this. Measure with an SPL meter (you probably don't have one; you can make due with micing up the cab to a preamp/mixer that has a VU meter or LED bar graph). Switch out the head and repeat with the other one, note the difference in SPL. Control all the variables that can be controlled. I'm assuming there are modern ones with the fx loop here, which may not be the case.​
 

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Fair enough, I see the current models do. the point was to explain that there are a number of factors at play, and they'd need to be isolated to draw specific conclusions.
 

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Fair enough, I see the current models do. the point was to explain that there are a number of factors at play, and they'd need to be isolated to draw specific conclusions.
No disagreement here haha.

The other thing is, we dont know what all was changed on the 6550 loaded 2203.
 
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