Bridging tube amp combo with Solid state power amp

[tele_player]

Only problems I see with that analysis are that the box isn't very big, and doesn't seem to have large input and output transformers.

Ho doesn't supply much technical info, only "The Enhancer improves your tone and can increases a 50watt amp to 100w."

What I'm seeing in that box looks pretty small for a 50 watt amp.

I'm curious, but not curious enough to pay $225 to trace the circuit.

Robert

[GERPUD]

By the way, I've done several research on different forum and this topic does not have been discussed before.
It is very surprising that trying to boost the power a small amp has not been discussed before.

In a car tuning forum, I'm pretty sure that Post #1 at Day #1 at the beginning of internet was: How can I put 600HP in my Honda Civic ?.

So putting 50W in a 9W combo seems to me a normal and basic quest!!

[Leo_Gnardo]

In a car tuning forum, I'm pretty sure that Post #1 at Day #1 at the beginning of internet was: How can I put 600HP in my Honda Civic ?.

Late 60's there was a spate of mechanics who put V8's into Volkswagen bugs... a labor of love to be sure (or booze, pill & powder-fueled madness) to make something impractical (no room left for payload.) But they sure looked cool, and could drive well into the speed range where the VW chassis became unstable.

It's a lot less hassle to do what you're trying to do, at least you won't get your hands all filthy & greasy for days at a time. But how to get from here to there?

FWIW last summer I was given the world's heaviest Princeton Reverb to work on. Some bright spark had converted it to hi power @ 50W all right. 6L6's in the output tube sockets. Big military power transformer crammed into the corner of the box supplied B+, stock PT provided all other power. Fist-sized OT crammed onto the chassis. Rectifier tube: gone - replaced by a filter cap can. One good thing - they found an Altec 10" and bolted that in too. Well I spent one Sunday, all day long, getting that thing working and it DID sound terrific!

Then - the customer told the store where he dropped his prize off - "restore to stock." All my work down the drain, oh well, not the first time that's happened. In the end, the customer got his amp back, stock. So stock it was, except for that Altec - wow did it sound a treat even with a mere 12 watts of clean power.

[GERPUD]

To continue the analogy, putting a V8 in a Volkswagen bugs is like putting 4x6L6 in a Blues Junior. It's, in fact, major work.
What I'd like to do, is to keep the current engine but adding an electric motor (SS power Amp) to get an hybrid car, knowing that the transmission and tires can handle the extra power (speaker).
More like a modern car tuning design...

[tele_player]

To continue the analogy, putting a V8 in a Volkswagen bugs is like putting 4x6L6 in a Blues Junior. It's, in fact, major work.
What I'd like to do, is to keep the current engine but adding an electric motor (SS power Amp) to get an hybrid car, knowing that the transmission and tires can handle the extra power (speaker).
More like a modern car tuning design...

Why don't you just buy the box from Ho, and see if it works for you?
Nobody here seems to have an idea of how to do it for less money.

Robert

[GERPUD]

JMFahey said yesterday that he may have a solution. He explained how Ho's device was probably working.

Buying Ho's box is a boring DIY project, no work = no fun.
I'd like to try the "Power Booster" design of tubecad. See the schematic attached. I'd like to see if anybody has recommendations on that design, or any better ideas. IF this thing works, it is very cheap and simple to do, and could give big results.

By the way, this Power Booster uses a little bit the concept of the title of this post: bridging a tube amp with a solid state amplifier, but he's adding a IMC (impedance multiplier circuit) to make it work. My schematic was wrong, but the idea wasn't totally out.

[JMFahey]

Well, I've been thinking about it, I'm more certain now that my original idea is reasonable, found that on specific cases I do not even need the output transformer at all , as long as I am happy with "just" quadrupling original power , that's why I said my solution would be lighter.

Probably Mr Ho's excellent idea needs input and output transformers to make it truly "universal" (any input impedance to any output impedance), my goals are more modest.

I'll draw a raw schematic, but forget specific parts values, even less a "ready to build" project , any working design requires development, sourcing of special parts, etc.

And real world testing rules, I'll probably design and wind the input transformer to be able to experiment live, both at the Lab and onstage .

As said before, the goal of turning a 9W/8 ohms amp into a 36W/8 ohms amp , still letting the tube amp drive the speaker looks very possible.

Something that worries me (that's why real world testing is needed, simulation is an excellent tool but does not replace it) are 2 safety concerns:

1) the SS amp output will be in parallel with the tube amp output ... which to boot has an output transformer, this device also has an input transformer, both are by definition inductive and kick back voltage, it may be destructive to SS parts.

2) what happens if it's connected but SS amp loses power ? , either by forgetting to turn it on, blown fuse, whatever.
The tube amp output can easily kill output transistors if they are not closely tracking it, which is the normal situation.

Mumble mumble, I guess I might test something in February, when workload lowers (middle of Summer holidays here in Argentina).

[GERPUD]

I'll be very happy to see your design. Keep me informed!

I'd really like to have some comments on the "Power booster" from Tubecad.
No transformer, one cheep IC gainclone, 12 resistors and 4 capacitors...
Too good to be true?
Would it work as shown or it is simply a theoretical design that makes a nice blog?

[tele_player]

It would also need a +/- 30v DC power supply of sufficient current capability.

Robert

[shane]

Our good friend Steve Connor did a cool thing along the lines of what you're wanting
check this on his site:
http://scopeboy.com/scopeblog/?page_id=96
Cheers
Shane

[teemuk]

Would it work as shown or it is simply a theoretical design that makes a nice blog?

Find out.

At the moment it's nothing but a schematic of a circuit that could work. Turning that to a solid reliable design will take tremendously more time than drawing schematics that could work.

I love TubeCAD site: refreshing think-outside-the-box ideas, but unfortunately the site is more about throwing around new ideas than about the extra steps of turning them to reality.

It's easy to draw a little triangle on a paper and say it's a flawlessly performing, ideal power amp. But if that ideal power amp doesn't work in practice it nullifies all the clever ideas of the circuit.

[GERPUD]

Shane : RIGHT ON!!!
Exctly what I was looking for!
Give a big thanks to your friend Steve, and tell him he did something really cool!!

It is definitely similar to Tubecad, BUT he did it for real and it is working!!!

Thanks for sharing!

[RWood]

All this discussion is very interesting and I'm enjoying it very much... but at the end of the day it is just trying to make something into what it is not.
Everything is a tradeoff.
Since I started playing(1969) I've not found a resistive divider load into a power amp that duplicates the tone as well as a good, well placed mic in front of the original amp into a very clean power amp.
Some have been close but none better...although that could be my preconceived biases coming through.

That being said, it is still fun to throw OHM's law into a blender and see what comes out.

[tele_player]

The tubecad schematics aren't a voltage divider into a power amp.
Whether they work, and how it sounds for guitar, are unknown.

Robert