so how can 11 watts have at least TWICE the headroom as 28 watts?

[pedalcr8z]

In fairness to the brand I will leave the 28 watt amp nameless but it is the supposed reference 28 watt clean combo out there. How is it that my /13 CJ-11 with 2 (6V6) rated at 11 watts could have twice the clean headroom of the 2 (6L6GC) 28 watt amp? How is this possible and what factors are responsible for this?

[Franktone]

Originally Posted by pedalcr8z

In fairness to the brand I will leave the 28 watt amp nameless but it is the supposed reference 28 watt clean combo out there. How is it that my /13 CJ-11 with 2 (6V6) rated at 11 watts could have twice the clean headroom of the 2 (6L6GC) 28 watt amp? How is this possible and what factors are responsible for this?

Are you comparing both amps with using the same speaker cabinet. Different speakers have different sentivities. A difference in speaker sentivities of 3 dB or more can create a radical difference in headroom.

One and a half years ago I got together with my old band. I played the Traynor Bass Mate 2-6V6 cranked all the way up through my 2x12 G1265 Celestion cabinet. Later I plugged in my Stephenson 30 head into the same cabinet and used the switches at the back of the head to shut off 3 output tubes and left only a single 6V6 output tube running which should only be about 6 watts and I couldn't not get it up past about 2/3 volume. I tried to run it that way full up but it was way too loud. Both amps do not run tube rectifiers either. It is possible that the big transformers have something to do with it. Also it may have something to do with the ability of an amplifier to focus its power on to its mid range frequencies.

[pedalcr8z]

Originally Posted by Franktone

Are you comparing both amps with using the same speaker cabinet. Different speakers have different sentivities. A difference in speaker sentivities of 3 dB or more can create a radical difference in headroom.

One and a half years ago I got together with my old band. I played the Traynor Bass Mate 2-6V6 cranked all the way up through my 2x12 G1265 Celestion cabinet. Later I plugged in my Stephenson 30 head into the same cabinet and used the switches at the back of the head to shut off 3 output tubes and left only a single 6V6 output tube running which should only be about 6 watts and I couldn't not get it up past about 2/3 volume. I tried to run it that way full up but it was way too loud. Both amps do not run tube rectifiers either. It is possible that the big transformers have something to do with it. Also it may have something to do with the ability of an amplifier to focus its power on to its mid range frequencies.

Excellent answer, thank you. In this case it was a Greenback in the /13 and a Eminence Wizard Red Coat wizard in the 28 watt combo. However now it even get's more perplexing as the Greenback's sensitivity is 98 vs 103 for the Wizard! So we still have an 11 watt amp with a 98 sensitivity speaker with at least twice the headroom as the 28 watt amp with it's 103 sensitivity speaker

[Franktone]

Originally Posted by pedalcr8z

Excellent answer, thank you. In this case it was a Greenback in the /13 and a Eminence Wizard Red Coat wizard in the 28 watt combo. However now it even get's more perplexing as the Greenback's sensitivity is 98 vs 103 for the Wizard! So we still have an 11 watt amp with a 98 sensitivity speaker with at least twice the headroom as the 28 watt amp with it's 103 sensitivity speaker

Is one of the cabinets closed back and the other open back? Generally closed back cabinets are louder out front. Are there other cabinet design features such as one of them being ported? A totally detuned cabinet will not gain any resonance while a cabinet designed with some resonance in mind should be louder. Try plugging each amp into the others cabinet, if that is possible and there are no bad impedance mismatches.

[Webfoot]

Maybe something is biased cold. I put a new output transformer and bias circuit in my amp but accidentally used my old bias table and had the tubes running at 5 watts. I was bummed thinking the xformer was a waste of money because the amp did not sound much different.. in fact even weaker. While putting things away I discovered I did not bias using the new output transformer calculations. Corrected it (rebiased) and increased the output by 60%... actually could of increased the output 100% but I don't like to run output tubes really hot.

[pedalcr8z]

Originally Posted by Webfoot

Maybe something is biased cold. I put a new output transformer and bias circuit in my amp but accidentally used my old bias table and had the tubes running at 5 watts. I was bummed thinking the xformer was a waste of money because the amp did not sound much different.. in fact even weaker. While putting things away I discovered I did not bias using the new output transformer calculations. Corrected it (rebiased) and increased the output by 60%... actually could of increased the output 100% but I don't like to run output tubes really hot.

Both open back cabs as for bias being cold at $2500.00 for a boutique amp it had better have been biased perfectly out of the box. I sent it back and I'm keeping the /13 as not only was there a headroom difference the /13 had far more clarity and was simply more alive and 3D sounding even allowing you to hear the neck wood resonating whereas the other amp was dead sounding as well as harsh at the same time and basically had no cajones to speak of, very mushy in fact.

[Halsey]

Aha that nameless amp is pretty easy to guess!

[nivek_yoccm]

couldn't it also be that the front end was breaking up on the 28W amp? were you hitting them with somewhat high output pickups or pedals? this may not have anything to do with the power section, right? I've played amps that had some distortion just from the front end at very low volumes

[katuna]

I believe the 28 watt amp was designed to be fairly soft while the CJ was designed to be stout and stand up tall. I also believe that the 11 watt rating of the CJ is a bit of a put on, kind of like an aww shucks, I'm just a little 11 watt (firebreather from hell...). I agree that the Divided by is a better amp if you like to crank, spank and rock and roll.

[pedalcr8z]

Originally Posted by nivek_yoccm

couldn't it also be that the front end was breaking up on the 28W amp? were you hitting them with somewhat high output pickups or pedals? this may not have anything to do with the power section, right? I've played amps that had some distortion just from the front end at very low volumes

Custom shop[ Strat with '69 p/u's and a Nocaster and the Strat had NOWHERE near the headroom as the CJ and it's p/u's are lower in output than the Nocaster!

[RJLII]

I've always wondered how companies arrived at their ratings. My old Fender DRRI had two 6V6 tubes and was rated at 22 watts while the CJ11 has the same tube complement and is rated at 11 watts. I had a Fender Blues DeVille with two 6L6 tubes rated at 60 watts, but my Carr Rambler with the same tube complement is 28 watts.

I'm guessing the CJ11 has a very conservative rating.

In any case, is the observed headroom difference based on the perceived volume level (sound pressure) when tube breakup starts or the position of the volume knob? I was surprised that my Rambler started to break up as early as it did with respect to the volume knob position (about 1:00 if using humbuckers as I recall), but in all fairness it's loud as hell when the clean goes away. P-90s allow me to turn it up a bit more before tube grind starts.

[slider313]

Is the 28 watt amp cathode bias and the :/: 13 fixed bias? The power supply voltage plays a big part in clean headroom. I bought a used Carr Rambler and held on to it for only four days. I tried different tubes and speakers but when I sat it next to my Deluxe Reverb, and I ran it through its cab and speaker also, it was really no contest. I'll take a DR every time.

[pedalcr8z]

Originally Posted by slider313

Is the 28 watt amp cathode bias and the :/: 13 fixed bias? The power supply voltage plays a big part in clean headroom. I bought a used Carr Rambler and held on to it for only four days. I tried different tubes and speakers but when I sat it next to my Deluxe Reverb, and I ran it through its cab and speaker also, it was really no contest. I'll take a DR every time.

Both are cathode biased. Rob I was not judging by the position of the volume potentiometer, I was judging by the fact that the 28 watter lost all it's clean headroom at at least half the perceived volume of the CJ. I was totally unprepared for that as the Strat's p/u's are not very high at all. It almost didn't sound like a Strat anymore, nowhere near as "quacky" on positions 2 & 4 (I realize power had nothing to do with that).I suppose I shouldn't be too suprised as in my previous life in the hi fi industry there were plenty of examples of lower powered amps outperforming amps with far greater power ratings. Bob Carver's original company Phase Linear and his Carver company commonly had their 200 & 400 watt per channel amps embarrassed by well made 50 & 100 watt per channel amps.

[pickslide]

I have a 63 Gibson Falcom 2 6v6 combo that is rated at about 15w and it stays clean all the way up....I guess it has to do with the way the amp was built ie the circuit itself?

[RJLII]

Originally Posted by pedalcr8z

I was not judging by the position of the volume potentiometer, I was judging by the fact that the 28 watter lost all it's clean headroom at at least half the perceived volume of the CJ.

That's what I assumed but I thought I'd ask anyway . That's a real puzzler, especially in light of the changes in how your Strat sounds.