# Have any of you installed London Power "Power Scaling"?



## Gordie (Mar 22, 2014)

I can't understand the confounded instructions, if anyone knows how to "insert" this kit into a Fender Twin Reverb, please answer! I'd really appreciate it. Or else I'll have to sell this stuff. (Not the Twin...)


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## Paul Running (Apr 12, 2020)

Just to confirm...you have the fixed-bias kit?


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## KapnKrunch (Jul 13, 2016)

Just call Kevin: (807) 473-0952.

I just take it there and watch him do it. While he does it he is speaking some electronic language from another planet. I don't think he appreciates that not all of us are up to speed, so you have my sympathies. LOL. Quiet type, but very nice. He will talk to you all day, and won't leave you hangin'. 

I have another friend, very technical, taught refrigeration at community college, he gave up eventually, so there is always that option.


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## Gordie (Mar 22, 2014)

I have the optional fixed bias kit with the extra bias goodies, which was suggested is good to have... I haven't looked at this stuff for a while but I'll dig it all back out. I'm way out west in the Okanagan Valley, so I can't take it in to Kevin's. Maybe I'd better phone him.


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## RBlakeney (Mar 12, 2017)

Gordie said:


> I have the optional fixed bias kit with the extra bias goodies, which was suggested is good to have... I haven't looked at this stuff for a while but I'll dig it all back out. I'm way out west in the Okanagan Valley, so I can't take it in to Kevin's. Maybe I'd better phone him.


Does it come with instructions? A picture of those may be helpful to see if so


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## Gordie (Mar 22, 2014)

It comes with instructions. First of all you must build the whole works into its circuitboard just like building a real convoluted pedal. It'll take me a while to post a picture or attachment of the instructions. I can build the whole thing, but I'd rather sell it. I'd especially like to hear from someone who has installed one. I'm doing up this Twin Reverb for my cousin, and thought Power Scaling would be the answer. I'll try to put the instructions up. Thanks


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## jb welder (Sep 14, 2010)

Gordie said:


> I'm way out west in the Okanagan Valley, so I can't take it in to Kevin's.


One of the licensed installers listed on Kevin's website is in Castlegar.


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## Gordie (Mar 22, 2014)

Yes, I noticed that. I hail from that area! 400 kms away


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## Latole (Aug 11, 2020)

Voltage Scaling in Amplifiers - Power Scaling / VVR


Dana Hall's VVR3 PCB kit. Power Scaling (a London Power trademark) and VVR, which stands for Variable Voltage Regulator, (Dana Hall of ...




revolutiondeux.blogspot.com





Power Scaling circuit is wired in series in amp Power Supply











You may also need a Raw auxiliary power supply :









RBX Raw Bias Supply Kit: When to Use It - London Power Tube Amp Kits


London Power's RBX Raw Bias Auxiliary Supply kit, and its role in Power Scaling mods. Most stock bias supplies are inadequate to the task. RBX will help!




londonpower.com





*Two Problems With Stock Bias Supplies*
First, they are usually “high impedance”, which means they are derived from the plate winding through very high value resistances (100-220k) or through capacitors. A high-impedance bias supply cannot support proper bias-set networks nor will it support a bias regulator.

The second issue is that they lack enough voltage range to properly control all samples of tube that may be plugged into the amp. Resistively derived bias supplies can have this range, but will lack the current needed for a bias regulator. Decreasing the series resistance creates a high amount of waste heat, and the bias regulator could be damaged by excess voltage to its input. Capacitively coupled bias supplies are inherently limited in both their voltage range and current output.


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## diyfabtone (Mar 9, 2016)

Gordie said:


> It comes with instructions. First of all you must build the whole works into its circuitboard just like building a real convoluted pedal. It'll take me a while to post a picture or attachment of the instructions. I can build the whole thing, but I'd rather sell it. I'd especially like to hear from someone who has installed one. I'm doing up this Twin Reverb for my cousin, and thought Power Scaling would be the answer. I'll try to put the instructions up. Thanks


I've installed two of them, the Cathode Bias version in a KOC AC-30 project and a Fixed Bias in a YBA-1a. Both work well if you install as per instructions. They make almost any amp usable at low volume levels!


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## WCGill (Mar 27, 2009)

I've done London Power's and Dana Hall's, probably have a few in stock. Although I'm in the OK, not doing any amp work at present due to health issues. Apologies but the circuit works well. The last few builds I did used the PPMV, very similar and much less expensive and complicated.


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