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Power Scaling WORKS!
#1
Hello Citizens

I must say that Power Scaling works very well. When you go from playing a large pyramid to playing in a small pyramid, you just set the dials lower and the tone is the same.

Not to mention protecting the Pharaoh's ears!

Kudos (yes, the Pharaoh knows Greek)
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#2
(08-22-2018, 03:54 PM)King TUT Wrote: Hello Citizens

I must say that Power Scaling works very well. When you go from playing a large pyramid to playing in a small pyramid, you just set the dials lower and the tone is the same.

Not to mention protecting the Pharaoh's ears!

Kudos (yes, the Pharaoh knows Greek)

Hi!
I totally agree! Big Grin

I put Power Scaling in my Marshall amp and it's fantastic. It was a master volume amp already so I left out the Drive Compensation control and use the MV for that.Like the kit notes said to do, adjusting both controls keeps the sound the same dialling up and down. Sometimes i like to just turn down the Power scale control and have mega distortion - haha Cool

Thanks for such a cool product!
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#3
(09-10-2018, 03:42 PM)nauta Wrote:
(08-22-2018, 03:54 PM)King TUT Wrote: Hello Citizens

I must say that Power Scaling works very well. When you go from playing a large pyramid to playing in a small pyramid, you just set the dials lower and the tone is the same.

Not to mention protecting the Pharaoh's ears!

Kudos (yes, the Pharaoh knows Greek)

Hi!
I totally agree! Big Grin

I put Power Scaling in my Marshall amp and it's fantastic. It was a master volume amp already so I left out the Drive Compensation control and use the MV for that.Like the kit notes said to do, adjusting both controls keeps the sound the same dialling up and down. Sometimes i like to just turn down the Power scale control and have mega distortion - haha Cool

Thanks for such a cool product
Hi Nauta,

That's a really worthwhile comment, coming from someone who already had a master volume control in his amp. I'd thought about just installing a good MV in an amp I'm building, but I think I'll go for the PS alternative now. Thanks for the information!
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#4
Another happy customer here, I had PS installed into my 50W Mesa Rectoverb, it's brilliant! I can get it down to around 5W before it becomes fizzy. Every amp should have it!
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#5
Hi Guys

Glad you're happy, Josh.

I suspect the power level is substantially lower than 5W if you are judging based on the sweep of the Power Scale control? You don't hear a loudness decrease until you get to the power level you are actually using. As a reference, when the Power Scale control is set halfway, there is about one-tenth of the voltage and one-hundredth the power, so your 50W is putting out a half-watt tops.

To maintain the tone you have to set Power Scale and Drive Compensation (or your MV) about the same. Some players find this works down to a certain point and then they just use the Power Scale control, but it depends on the amp and speakers.

If you dial just the Power Scale control, the sound will get distorted just below the point where you hear the loudness reduce.

Have fun
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#6
Count me as a very happy user of Power Scaling too.

I put it on a 50W amp I made for myself (I shared info and pics on it here in the projects area) and it works great. I put a switch in so I can switch power scaling on or off and then I can use it without and just as a vintage style turn it up louder amp if I want.

I put power scaling in an amp I built for a customer too, but I ended up pulling it out of that one. This amp was around 20W and I couldn't quite get the transitions dialed in right and the customer wanted the amp and didn't want to wait for me to get it dialed in. Both amps have a MV and the power scale control.

Greg
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#7
Hi Guys

Greg, the "transitions"?

Have fun
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#8
Greetings Citizens!

The Transitions were a band Mamoon Ra had during the Third Epoch... how to convert to Gregorian calendar?... anyway, they had a really good reed player.

The Pharaoh rocks Smile
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#9
Hi Kevin,

I'd say you're right there, I can definitely get down to bedroom volumes. I thought it was 5w as that's what my amp tech told me it was. Regardless, absolutely loving it! After reading your reply I might have another play with the mv and ps controls too, I has the ps dialled right down and adjusted the overall mv and channel mv
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#10
Hello,

Let me admit that I put two Power Scale circuits in the JTM45 and JCM800 copies I built and they work like a charm. With the JTM I was able to supply the SV1 from the spare 70V winding I had on the PT, but on the 800 I had to use the RBX module. Zero problems with installation in both cases whatsoever.
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#11
Hi Kevin,

Maybe I wasn't clear enough about what I meant. On this particular amp I found I had a harder time dialing in the power scaling compared to the amp I made for myself in reference to when it was full on vs having it off (I added a switch to be able to turn it off). This particular amp was similar to a Deluxe Reverb but with 6L6GC tubes and a lower voltage than I would have liked. It would sound a bit too fizzy when the power was down and master volume and volume controls were adjusted to try to emulate all the way up with power scaling off tone. I could have got it dialed in eventually but the customer wanted the amp quicker, and he eventually had me take power scaling off it entirely because he wanted bias modulating trem and I had trouble getting that to work with power scaling installed. I'm sure that could be done too, but it would have to be scaled on it's own in reference to the main power scaling. He supplied me with the parts for this amp, so I was locked into certain choices. He had some other guy building it originally but that guy took too long so he came to me, and I redesigned some things and started off with a fresh cosmetic design and circuit design, but using his transformers and chassis.

The other amp I made for myself with power scaling incorporated was 50-55 watts and made out of a Bogen transformer set and tubes and then I added my own circuit and changed a couple tube types, etc. Maybe the higher headroom amp is a little easier to dial in.

Greg
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#12
Hi Greg

If the Power Scale is set to a low level, the MV or DriveComp have to be adjusted accordingly to maintain the cranked tone. If this was a combo amp, there will be issues achieving a quiet tone that is "full".

Depending on the MV used, most have limitations of tone versus sweep. TUT shows a simple amendment to make the traditional MV much more even in this respect. The LP-MV shown in the kit notes for SV1 is essentially transparent. However, depending on what specific circuit demands were in place by the player, things can be made a bit difficult.

When a customer wants an amp built for a certain tone, he should leave it up to the builder to decide on parts and circuits. Most players are too ignorant of electronic methods to feel anyway justified in dictating circuit parameters beyond how it should sound.

Apart from that, in conventional circuits there is no difference installing Power Scaling in a low-watt amp versus a high-watt amp as far as the range of loudness sweep and the ability to retain cranked tone. For example, Mark Stephenson's 1W Stage Hog is Power Scaled because it can be too loud when played directly through a cabinet, and it dials down very smoothly. At the other extreme, my old 700W Spectrum was Power Scaled and could play at a whisper. That was the amp I developed the optical regulator for, due to the very high voltages.
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#13
(11-06-2018, 10:47 PM)K O\Connor Wrote: Hi Greg

If the Power Scale is set to a low level, the MV or DriveComp have to be adjusted accordingly to maintain the cranked tone. If this was a combo amp, there will be issues achieving a quiet tone that is "full".

Depending on the MV used, most have limitations of tone versus sweep. TUT shows a simple amendment to make the traditional MV much more even in this respect. The LP-MV shown in the kit notes for SV1 is essentially transparent. However, depending on what specific circuit demands were in place by the player, things can be made a bit difficult.

When a customer wants an amp built for a certain tone, he should leave it up to the builder to decide on parts and circuits. Most players are too ignorant of electronic methods to feel anyway justified in dictating circuit parameters beyond how it should sound.

Apart from that, in conventional circuits there is no difference installing Power Scaling in a low-watt amp versus a high-watt amp as far as the range of loudness sweep and the ability to retain cranked tone. For example, Mark Stephenson's 1W Stage Hog is Power Scaled because it can be too loud when played directly through a cabinet, and it dials down very smoothly. At the other extreme, my old 700W Spectrum was Power Scaled and could play at a whisper. That was the amp I developed the optical regulator for, due to the very high voltages.


Hi Kevin,

Yes I realize the MV has to be adjusted in order to get the tones you are after if you turn the power scale control down. It was a combo amp, but it wasn't a lack of bass...it was more that the tone went from decent and mildly overdriven to fizzy depending on where the MV and PS controls were set. It just needed more dialing in, but as I said, the customer was impatient. I agreed to do the work for him using his parts, and the amp turned out well and he is happy with it now. If I would have chosen the parts I would have made some different choices for sure. For instance, Mercury Magnetic transformers are extremely expensive and don't give any added benefit over other such as Heyboer for example. So I would not have used Mercury Magnetics if it were up to me, but that was what the customer had. It would have been nice if I could have gotten PS to work the way I wanted on it as that was the original concept, but he decided to not use it. I'll incorporate it into a future amp I am sure because I was able to make it work well on my other amp that I put power scaling on. 

Its good to know that there shouldn't be any difference in using power scaling with large amps vs small amps. 

Greg
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#14
Hi Greg

For the bias modulated trem, use TREM and apply the modulation signal to SV1 as the kit notes show. This scales the tremolo signal and modulates bias as desired.

Have fun
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#15
Hi Kevin,

Is the TREM module a new one? That wasn't available as far as I know when I was working on the amp in question. That would have been in 2013-2014. I figured that the trem signal would have to be scaled and modulated as you have done here, and I was going to do it for that amp but didn't have time to work something up before the customer became impatient.

Greg
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#16
Hi Greg

Yes, TREM is new compared to 2014 - out for a year or so.

TREM was designed initially to be used in Vox amps as so many of their models have global tremolo applied via the grid-leaks of the output stage. Fender has their newer Princeton with bias-modulated tremolo in a fixed-bias format similar to what you described.

Scaling the trem oscillator does not work in most cases as the oscillators tend to be a bit sensitive to supply voltage to function properly. TREM attenuates the modulation signal in step with the Power Scale setting.
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#17
Hi Kevin,

When I was working on that amp I was able to determine how a Trem scaling would have to work and it would just apply some of what you already did with power scaling on the trem signal, but I didn't have time to design anything to do it. Since you have a TREM kit available now I could just use that if needed, so that is cool. I guess the EE school was helping me visualize the circuit in better detail so I was able to determine what needed to be done. That and your books and working with Power Scaling already. I'll  have to see if the owner of the amp in question wants me to put power scaling on it along with trem scaling again or if he is happy the way it is now without it.

I know if you tried to scale the oscillator that would not work very well, since it needs a certain amount of gain to keep oscillating. Lower the voltage down a bunch and that wouldn't be able to maintain its gain.

Greg
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#18
Hi Kevin,

I decided to get a couple of the TREM kits before your new site comes. Should be an easy way to make the concept I described above work well in future projects.

Greg
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#19
At some point I must have adjusted the bias with PS at just under 50%. I cranked the comp and PS all the way up when a bass player was using the amp and could not heard. Got pretty stinkin' hot. I believe that is what happened. Bias check later proved way too high for the 6V6s involved. I had used the amp for quite some time without changing the PS and comp before this.
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#20
Hi Guys

In a Power Scaled amp bias is set at full voltage, just as the kit notes state.

One reason for this is that you do not have Power Scaling otherwise.

A second reason is to avoid the trouble sinusoids encountered.

Have fun
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A warm welcome to those interested in tube and hi-fi audio! Fans of Kevin O'Connor's The Ultimate Tone (TUT) book series form a part of our population. Kevin O'Connor is the creator of the popular Power Scaling methodology for amplifiers.
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