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London Power Power scaling?


highpressur

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I do. I have a Stephenson LJ-10, a little 15W head built around the power scaling technology. The Power Scaling is excellent, much much better than an attenuator. I can get great tones at pretty much any volume (if you ignore the usual effect of speakers being pushed and us hearing things differently on high volumes) while with attenuators it was a tradeoff between the attenuator sucking tone and dynamics or being too loud.

So I totally recommend the Power Scaling, I really wish all tube amps came with it.

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LaXu,
I'm very interested in power scaling. I recently bought a Marshall JCM 800 50 watt amp combo, and I'd like to be able to tame it down for apartment use, and also be able to rev it up enough to get the power section all hot for live (loud) sessions.

I wonder how hard it would be to install the kit.

I wonder how well power scaling works with various kinds of amps.

Please give us the low down. When you set your amp to almost full throttle on the power section, but reduce the volume to the speakers via the power scaling knob, just how quiet can you go and still get the benefit from power section overdrive.

Isn't it true for power scaling as it is for power attenuation, the quieter you go, the more the tone suffers?

BTW, this is my first post here, cool site. I first noticed some of your posts by checking out the attenuator comparison thread.

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begin_etienne has a Plexi RI with the power scaling installed and it sounded pretty good from what i heard.

( see here - http://acapella.harmony-central.com/forums/showthread.php?threadid=828605&highlight=london+power)

(also, a clip here - http://acapella.harmony-central.com/forums/showthread.php?threadid=847996&highlight=beginetienne+malmsteen)

it doesnt degrade the sound the lower you go...but of course it will sound better louder...thats just the way it is :) with speaker breakup and all that goodness.

you will get power tube saturation at any volume

i think you probably have to get a tech to install the kit for you

with a Marshall, an amp that gets a lot of its tone from the power section, id say its DEFINITELY worth the $200 or so bucks to have it put in. It should get rid of that buz you get at low volumes and warm up real good for you. I strongly concidered buying a 2203 and getting this kit installed for a while.

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I listened to that clip, sounds great. Wish I could have seen him play some of that faster than the moving eye can see stuff. So what did you do instead of getting the 2203?

I am a bit in a fix. A few months back, I talked to Kevin OC from London Power, and when I mentioned that I would likely take the kit to a local amp guy and have him install it, he told me that he would really not prefer that I would do that. He was concerned that the amp guy would steal his ideas and use them without giving Kevin his dues.

But I have not yet done any amp mod work. I'm thinking about learning the basics and just do it myself as I would like to be able to do some amp mods myself anyway. I am "very" low on funds and so sending my amp to Stephenson's is not a viable option. 18watt dot com is a cool place to learn about amps and such. Maybe someone there would help me do the mod.

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Well, if he is selling a kit with a schematic for installation instructions then that won't really stop anyone from buying a kit and copying it, now does it?

Stephenson does do very good work though and is great to deal with so I do recommend him.

My Stephenson head doesn't really even have a regular master volume, the Power Scaling replaces it in it. I can go much lower than with attenuators and not lose high end and dynamics and still have excellent tone. The drive control is also very cool for controlling how compressed the tone gets.

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Originally posted by 1_Way

I listened to that clip, sounds great. Wish I could have seen him play some of that faster than the moving eye can see stuff. So what did you do instead of getting the 2203?


I am a bit in a fix. A few months back, I talked to Kevin OC from London Power, and when I mentioned that I would likely take the kit to a local amp guy and have him install it, he told me that he would really not prefer that I would do that. He was concerned that the amp guy would steal his ideas and use them without giving Kevin his dues.


But I have not yet done any amp mod work. I'm thinking about learning the basics and just do it myself as I would like to be able to do some amp mods myself anyway. I am "very" low on funds and so sending my amp to Stephenson's is not a viable option. 18watt dot com is a cool place to learn about amps and such. Maybe someone there would help me do the mod.

 

 

I ended up buying an Orange Rockerverb instead.

 

Yeah, if hes selling the mod w/ schematic, i dont get why hes telling you not to get a tech to do the installation. Couldnt he patent it anyway? you can just take it to a tech, so i woulnt worry about that.

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Thanks, ya, I sort of think he's sort of walking in two different directions and hoping for the best. I'm not sure if this stuff is copyright protected, or if there are patents or what, but he has stated that if someone copies his stuff for profit, then expect legal action taken against them, or something to that extent.

On the other hand, he writes entire books on these topics and as such, relinquishes many of his ideas to the public domain. Same for schematics/layouts with his kits. He takes pride in the idea that apparently, he has been a moving force in the interest and growth of boutique or homemade tube amps. Apparently, some of his books are quite popular resources.

It took me by surprise when he said that he would prefer it if I would not have the kit installed by a professional tech. He said that while our backs are turned, he could copy his ideas and then profit off of them for his own business. I think he wants guitarists to get ahold of his stuff the easiest way possible to help the word get out about his wares, but please don't clone the ideas as though it's yours. Who knows, perhaps the threat of legal lawsuit is a sufficient deterrent for his needs.

By these descriptions, I'm more determined to have one of these PSK's installed.

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I spoke to Kevin...he is a nice guy, but kinda weird. He was trying to give me advice on stuff I didnt want or ask for. I bought an effects loop kit from him. While it is a great design, I feel like I go ripped off...the kit was $105 and it only came with limited parts...it forces you to buy more parts from either him or another store.

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Originally posted by psychodave

I spoke to Kevin...he is a nice guy, but kinda weird. He was trying to give me advice on stuff I didnt want or ask for. I bought an effects loop kit from him. While it is a great design, I feel like I go ripped off...the kit was $105 and it only came with limited parts...it forces you to buy more parts from either him or another store.



Kevin is very passionate, and opinionated sometimes :)

He's got a real wealth of knowledge, it's amazing.

What kind of loop was it ?

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begin_etinne,

I live in Northern Indiana, USA. I've considered sending my amp to Stephenson amps, but from what I gather, he does top quality high-end work for high-end prices. I'm very poor and necessarily seek modest arrangements. I'm willing to pay to have the kit properly installed, but not if I can reasonably become competent enough to do the install myself. I simply can not afford to overlook the cost savings by doing the labor myself, but I have my doubts that I could become well enough trained to do such a mod without any problems.

 

Also, there is a reputable amp builder slash service tech local to my area, and I believe that he would do a fine job installing the kit, and of course I would extend Kevin's warning about not cloning his kit for profit in his own business. Who knows, maybe this amp builder might end up becoming an authorized service center or dealership for London Power stuff. Although in general, he did not seem to keen on the idea "volume attenuation" or "power scaling".

 

 

psychodave,

Chuckles, ya, Kevin seems to be a unique character, but for the most part, he seems like a reputable business man who simply can't afford to be ripping people off. He does have a tendency to stretch people into learning more about amps instead of just accepting what someone may tell you (including himself!). I'm finding that amp techs tend to really appreciate hands on experience.

 

Even the power scaling kit does not come with everything you need. It's missing some things most likely because of various alterations that are inevitable from different amp designs and personal or optional needs. I understand that the Power Scaling Kit comes stock without a circuit board of all things! And without mounting brackets or sufficient heat dissipation in many cases as well. But these are reasonable omissions as some folks have their own stock of raw CB's and each amp would likely need custom built mounting brackets and some amps are lower wattage and may only need passive airflow cooling.

 

So I challenge you to examine how it is that you actually feel you got ripped off. How would you feel if you paid for materials that might work well for some amps, but not yours? Maybe you did not understand this reasonable customizable aspect of your purchase up front, but the converse is necessarily a rip off, paying for something that you may not be able to use.

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begin_etienne,
Man, thanks for the support info about power scaling. I'm mostly over at 18watt dot com and I'm having trouble getting info about power scaling there.

Ok, but which pictures, I am new to this forum, but I do remember seeing some pics somewhere. I'll have to go do a search again.

I have only barely broached the topic of power scaling to my amp tech, the holes drilled comment/objection seems to come from others on a different website, but thanks for the reminder that the power scaling kit can be installed in a very clean and non destructive way. I think he mostly is weary of power attenuators because they are known to give amps problems especially if they are not set up right or the user tries to do too much with it and does not properly care for the additional heat and such.

My amp is a 50 watt amp. And it sounds great at loud volumes, but I've never had it up past 4.5 yet!

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Who did your install?

I'm thinking of doing it myself. But will probably pay to have someone else put it in, or at least help me out if I run into problems.

I'm also thinking about swapping out the PCB with a PTP. I didn't know they made one until this guy told me about it over at 18watt dot com. I'm posting about it over at metro amp forums.

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Originally posted by 1_Way

Who did your install?


I'm thinking of doing it myself. But will probably pay to have someone else put it in, or at least help me out if I run into problems.


I'm also thinking about swapping out the PCB with a PTP. I didn't know they made one until this guy told me about it over at 18watt dot com. I'm posting about it over at metro amp forums.



Mark Stephenson did it (www.stephensonamps.com)

I'm not a big fan of PCB vs PTP in a Marshall. I'm more leaning towards changing the OT for overrall improvement in tone.

take a look a www.obsoleteelectronics.com.

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begin_etienne
I'm at a cross roads concerning doing one of two things. I will either do Power Scaling, or Power Attenuation (and optionally proceed from a full dummy load setting through a line out into a clean sounding slave amp, whatever works best).

My question about Power Scaling is about what the amp sounds like before and after the mod has been done. The skeptics say that when you install the Power Scaling Kit, it changes the amp such that it is no longer the same amp. This change might not be a significant change, I am wondering if it is noticeable or not.

Did you have your amp long before you had the kit installed and did you notice any sonic changes after having the kit installed?

Opps, if I remember correctly, you also upgraded one of the transformers... Did that happen at the same time? If so then I suppose that it would not be possible to discern which mod made any sonic differences. Any help here would be appreciated.

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Originally posted by 1_Way

begin_etienne

I'm at a cross roads concerning doing one of two things. I will either do Power Scaling, or Power Attenuation (and optionally proceed from a full dummy load setting through a line out into a clean sounding slave amp, whatever works best).


My question about Power Scaling is about what the amp sounds like before and after the mod has been done. The skeptics say that when you install the Power Scaling Kit, it changes the amp such that it is no longer the same amp. This change might not be a significant change, I am wondering if it is noticeable or not.


Did you have your amp long before you had the kit installed and did you notice any sonic changes after having the kit installed?


Opps, if I remember correctly, you also upgraded one of the transformers... Did that happen at the same time? If so then I suppose that it would not be possible to discern which mod made any sonic differences. Any help here would be appreciated.



I have done plenty of testing, not with an SLP but a 1987x. Mark Stephenson did the mod to my friends 1987x way before my SLP.

The amp sounds exactly the same, and will still give the available maximum output. Marshall Maniac (over at www.vintageamps.com) had issues when he installed it and documented that problem. He had installed the kit himself and did something wrong, not sure if he updated his document.

The amp sounds extremely different at low volumes, compared to its unmoded version at low volumes. Between .5 and 1 watt, the speakers are getting pushed, and you will get all the thickness and harmonic richness. On the other hand, at the same (low) volume, the 1987x w/o the PSK sounded extremely bright, punchy and thin.

The transformer upgrade made the amp MUCH smoother, no need to clip the bright cap, the OT was added to the 1987x months after the PSK. This could be a long shot, but I thought the amp sounded much more like a REAL plexi.

After I was done studying what was best for me using my friend's 1987x, I have asked to have all the mods done in a batch: PSK,JJs,OT and loop.

It's hard to say that the amp sounds exactly the same, they would have to be at the same volume, but the PSK keeps the power tube distorsion as you lower the volume, thus making it different, am I making sense ?

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I see. When you Power Scale, you naturally tend to include power tube saturation in the mix even at lower volumes, but not so with quiet playing w/out the PSK, it's basically just preamp tube distortion.

Ok, how about at somewhere like practice volume with a miked drummer, where the power section is somewhat cranked. Would the amp sound about the same or would it sound somewhat different...

... with
and
without Power Scaling? Say MV around 8 or so on both amp settings w/and w/o PSK.

See, you and others have said that changing the transformer can and does make a sonic difference. Such a claim is well established, different transformers can make a significant difference. On the other hand, it's my understanding that Power Scaling changes what is going on with the (power or output) transformer.

Some amp techs I've been chatting with online say that once you alter the B+ voltage (that's what a PSK alters), you are essentially changing the sonic character of the amp. It's no longer the same amp, at cranked or less than cranked levels. They are into making clones of the Marshall 18watt amp, and so I tend to suspect that they understand what it takes to remain faithful to the original sound. I think this is a suspicion of theirs as they have not tried power scaling (yet), although they seem very knowledgeable and skeptical.

I've heard your sound samples and I've heard some others from that guy who helped develop the use of the drive compensation control as a post PIMV (post phase inverter master volume).

Here's a link to a post you might be interested in.
CLICK HERE for more on quiet cranked amp sound

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Originally posted by 1_Way


Here's a link to a post you might be interested in.

 

 

You will find good info at the VA forum, especially from Marshall Maniac.

 

To me, if you attenuate to 90db, you should hear no tone alteration. At 90db your speakers will be pushed hard enough.

 

But remember, with no PSK and the volume at 8, it is SO loud that you cannot really tell what it sounds like unless you isolate the cab ! You can get permanent earing damage !

 

The PSK is more a power suply mod, the OT doesn't have to be modded. I might be wrong since I'm no techy !

 

Go check out thegearpage.net and do a search on the user "kevinoconnor", you will find good information there too.

 

E-

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begin_etienne
Hey, it's been a while! Hope you are doing fine. Are you still living in the temporary hotel arrangement? And how's things with your most excellent power scaled amp?

I'm interested in a specific issue that maybe you can help me with. I'm wondering about your ability to dial in singing sustain from feedback, the sonic relationship between your speakers and the guitar's pickups. And can you do that at lower volumes.

I used to own a solid state amp, the Marshall Lead 12 and I could get that thing to feedback at just about any volume, pretty cool stuff, but it lacked bottom end. Some at another forum are trying to discourage me from getting the power scaling kit if I hope to get low volume sustaining feedback. Also, do you ever use a distortion pedal up front, some say that might help me get the low volume sustaining feedback effect.

What are your thoughts and suggestions?

Thanks!

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