Super Scaler Amplifier from London Power-Can we build something similar ? How ?

[kagliostro]

The Power Super Scaler from London Power is something that acts (at my eyes) as a Linear Amplifier for Radio Frequency but in Audio Frequency range

they say that the output of an existing amp is increased without affect the tone or can have an over-drive if the power of the Super Scaler is decreased

to decrease the power I think they use a VVR

and about input I can only think they use an interstage transformer that has 4 or 8 ohm on primary and an adequate impedance on the secondary

What do you think about ? How do you figure it to be done ?

http://www.londonpower.com/products/sscaler.htm

Kagliostro

[Merlin]

It's done along these lines:
http://www.tubecad.com/2008/12/blog0153.htm

Quick reference:

[LooseChange]

With all the desktop amps I've built I've been wanting to build a Super Scaler (about 50 watts) for some time.  Just two 6L6's would do it.  I have a bunch of spare iron too.

[kagliostro]

MANY THANKS MERLIN 

that was exactly the info I was looking for

now I can confirm to me the architecture of those contrivance

........ so also the Weber AB200 Kit contain in it that architecture

and those section of that schematic can be used as reference

for a practical Super Scaler project

or so it seems to me

http://taweber.powweb.com/store/ab200_schem.jpg

thanks again

Kagliostro

[FYL]

........ so also the Weber AB200 Kit contain in it that architecture

Weber uses a small transformer as a phase splitter and driver, just like a number of vintage bass amps. It's not exactly a Super Scaler.

[kagliostro]

Hi FYL

Weber uses a small transformer as a phase splitter and driver, just like a number of vintage bass amps. It's not exactly a Super Scaler

but apart the NFB control which other big differences do you see ?

what do the difference ?

Oh ... YES

the output transformer is connected to the cathode instead of the plates

and OT CT is connected to ground

with this arrangement I presume the OT impedance will be different from the usual

say 1,750/2,000ohm for 4 x EL34 as usual

which will be with this arrangement ?

Thanks

Kagliostro

[FYL]

but apart the NFB control which other big differences do you see ?

SE drive of an AB2 output stage. Classic Fender x00PS-style with a couple of twists.

the output transformer is connected to the cathode instead of the plates

???

and OT CT is connected to ground

???

The power section is fairly standard.

[kagliostro]

The power section is fairly standard

Sorry

I mean, in this schematic

Kagliostro

[HotBluePlates]

The problem is that is not how a Super Scaler works.

Instead of a small input transformer feeding the power tubes' control grid (G1), a Super Scaler uses an output transformer which feeds the power tubes' screen grids (G2).

You take a typical output transformer and turn it backwards, so that the input is on the (4 or 8 or 16 ohm) secondary, and the usual primary is used to deliver high voltage and some current to the screen grids. The screens are considered quite linear, and need both a voltage and current input, which is power, and is why O'Connor says they function in the power domain.

How much power? The idea is to take a Champ-style amp with a few watts of output power, and use it to feed a pair of 6L6's to make the larger power output. The screen voltage determines the plate current, and (if I recall correctly) the screen is near d.c. ground. The control grid is also near 0v, but the tube can't pass current (or much current) without screen voltage. That means almost no idle current in these tubes. When there is an input signal (which is roughly 200vac or so), the rising screen voltage allows for a big rise of plate current. These things run in roughly class B, but work well.

You can't just make a large-voltage input signal, because the screens also draw current. So you need a power input. The end result is claimed to be a very accurate increase of power output from a small 4-10w amp to a total of 50-60w.

The schematic (in TUT 3, maybe?) is quite simple and the parts count is low compared to a complete amp. This is just a power supply and output stage, but you do need 2 "output transformers." One is an actual output transformer, and the other is for the input power.

[FYL]

I mean, in this schematic

OK. This one is a cathode follower. Gain slightly below unity but plenty of drive. All voltage must be provided by the driving amp.

Not a Super Scaler, which is a plain Jane plate follower driven by a smaller amp thru an OT.

[SoundmasterG]

To decrease the power O 'Connor uses something similar to the VVR, but VVR came after power scaling and was a take off on power scaling, and not the other way around. O 'Connor used to use a slightly different method than he does now for power scaling, and personally I think he may have changed it in response to what some of the copy cats did, but who knows. I will be putting it into two amps if I get the time and I have two of his simpler power scaling kits that work with fixed bias. The advantage of power scaling over VVR is that it works past 50 watts whereas the VVR only works to 50.

Greg

[kagliostro]

for HBP

Thanks, your infos add knowledge to the matter

as from the link posted by Merlin the use of one OT as Input Transformer and of another OT for the output was established

For FYL

As I've never seen a real world Power Scaler schematic I assumed that the schematic on the link posted by Merlin was a "standard" architecture schematic for a Super Scaler (or Boost amplifier)

With the OT connected to the cathodes I'm very confused about the primary impedance of the OT (I mean the transformer used for the output, not that used for the input)

so every further info (especially about OT impedance) will be highly appreciated

if I don't understand badly, you are saying that Power Scalers amps has a more usual architecture (with B+ on plates) than those of the example from the link posted by Merlin

For SoundmasterG

Yes I know VVR and scaler are to decrease power

here we are talking about to increase power with something like a "audio Linear Amplifier"

my be a bit of confusion because of the name London Power assigned to this kind of amp the name Super Scaler instead of Boost Amplifier (and I wrote Power Scaler instead of Super Scaler - now I correct it)

I think the action of a VVR on this kind of amp will act as the VVR insertion in an usual amp at level of only the output stage

you can read that "between lines" here:

http://www.londonpower.com/products/sscaler.htm

A variable boost ratio allows the SUPER SCALER to be over-driven if desired, or to stay muscular and clean and simply go louder.

Kagliostro

[VMS]

The schematic (in TUT 3, maybe?) is quite simple and the parts count is low compared to a complete amp. This is just a power supply and output stage, but you do need 2 "output transformers." One is an actual output transformer, and the other is for the input power.

The schematic is in TUT 5:

http://www.londonpower.com/catalog/product_info.php?cPath=3&products_id=8

and here is an Q & A page about Super Scaling:

http://londonpower.com/sscaling.htm

[FYL]

With the OT connected to the cathodes I'm very confused about the primary impedance of the OT (I mean the transformer used for the output, not that used for the input)

Cathode followers show a small output Z, typically 10 to 40 times less than plate followers. As the supplied schemo doesn't state which tubes are used, there's no possible answer...

if I don't understand badly, you are saying that Power Scalers amps has a more usual architecture (with B+ on plates) than those of the example from the link posted by Merlin

Yes. Check TUT for more details.

[kagliostro]

Thanks VMS

Hi FYL

OK I'll try to have a copy of the TUT5

(for the last order of a book to Pentode Press, I've wait something like 4 mounts - the book was the Power Amps of Richard Kuehnel - a very good one but less accessible to me than the book from Merlin who really is able to explain things in a very easy to understand way - hope there is a way to have the TUT in less time)

seems there aren't other schematic on the web for this architecture to be seen

---

referring to the Super Scaler with cathode followers I was thinking that this arrangement will be the way to use in a more safety mode also tubes like the 4CX250B with 1,000v - there is a galvanic insulation from the pilot amp and the OT isn't connected to B+, so I think this will help for safety if B+ is High - is this correct ?

Cathode followers show a small output Z, typically 10 to 40 times less than plate followers. As the supplied schemo doesn't state which tubes are used, there's no possible answer...

4CX250B at 1,000v B+ need 3,500ohm OT if Plate followers connected .................

10 to 40 times less is a large range, difficult to estimate to a (interested) neophyte ...................

 
also project with 50/100W like those thought by LooseChange are very intriguing and not to be underestimated

Kagliostro

[FYL]

I've wait something like 4 mounts

Poste Italiane as well as Dogane Italiane are really slow when it comes to international packages, with a couple of months of backlog, sometimes more.

referring to the Super Scaler with cathode followers I was thinking that this arrangement will be the way to use in a more safety mode also tubes like the 4CX250B with 1,000v - there is a galvanic insulation from the pilot amp and the OT isn't connected to B+, so I think this will help for safety if B+ is High - is this correct ?

1 KV is lethal in any amp configuration.

[kagliostro]

Poste Italiane as well as Dogane Italiane are really slow when it comes to international packages, with a couple of months of backlog, sometimes more.

YES you are right

we LOVE them     

Kagliostro

[Willabe]

kagliostro,

TUT 4 has a very good discussion on Super Scalers. Chapter 7, 35 pages. He realy covers a lot of ground on them.

You can even cascade them for even more power boost. KOC also talks about using a line-matching and/or multy tap  (say, 2,4,8,16 ohmn) input trans, remember this input trans is realy an output trans fliped backwards, so the speaker taps can be used for different power boosts.

More power,much safer voltages,off the shelf trans, not a bad deal.

TUT 4 has 12 chapters total, including a 97 page discussion on Power Scaling, IMHO well worth the $$. YMMV.   

   Brad     

[PRR]

The TubeCAD plan is a big clean triode-wired cathode-follower. Not real efficient. Maybe too clean for rock-n-roll. Does not reflect speaker impedance to the driver.

I'm pretty sure what Kevin is selling is Screen-Driven. This will give a high output impedance and the load will affect the driver.

Screen-driven SE amp with curves:
http://www.reocities.com/bobdanielak/technoteNo33.html

Push-pull screen drive with MOSFET drivers:
http://www.tubelab.com/Universal%20Driver.htm

> tubes like the 4CX250B

Not good in either the TubeCAD plan or a screen-driven plan: in true tetrodes the screen steals all the current when plate swings lower than screen. It would "work" in triode except the screen would melt.

> I think this will help for safety if B+ is High - is this correct ?

Not really. You are still relying on transformer insulation, and you have more transformers.

I think the BLOWER needed to work 4CX250 is a big problem for audio, even as a stage amp.

[Willabe]

Hi All, 

It is screen driven.

   Brad

[kagliostro]

I was looking for an 8552 (6146) SE amp schematic (that I have not yet found)

and I find this crazy thing 

http://www.montagar.com/~patj/tubeart.htm

The PS project is complicated because of the use in a vehicle

but the schematic of the booster is very simply

as LooseChange told, a 50W / 60W booster will be a nice toy

to be used with little amps

Kagliostro

[PRR]

> I was looking for an 8552 (6146) SE amp schematic

6146 makes HIGH current at LOW screen voltage.

Not a good Class A SE tube. You want reasonable current and screen voltage about the same as plate voltage.

You know what the schematic looks like... every other simple pentode SE audio amp.

Try 230V supply, 1.6K load, 220 cathode resistor.

[kagliostro]

Thanks PRR

so that tube is better used in a PP amp

or in a RF amp

I received the 8552 as a present from a friend

and it comes with a 6DK6 tube and a QB3/300 tube

unfortunately the QB3/300 has a little piece of material (gaphite ??) going around inside it

so I can use only as a nice desktop ornament

(may be I'll use as night lamp, don't know who can have put this idea in my mind  )

Thanks again

Kagliostro