Ultimate screen and bias voltage source: series 9v batteries in parallel with B+?

[eschertron]

Do you guys think the the batteries will have a capacitor effect and help to quiet the power supply noise any?

I've always thought of batteries as really big capacitors with terrible internal resistance properties :O

On another note, I remember reading that batteries were used as bias supplies in the 'golden age' ... but without connecting them to B+, I presume.

[Chuck H]

Taken to the end game, it might make some sense to use a rechargeable battery system for a bias supply. With modern technology it could be very stable and clean. Fully integral with a circuit and long lasting.

[mooreamps]

You guys go ahead and play with your adjustable DC regulators. I'm still playing with my primary side AC reg....

-g

[Chuck H]

Oh Gary... You tease.

You should embrace this forum as an avenue to expediate and possibly improve on your concepts. I have no trouble with someone here saying to me "that idea is $h!t" or "that's already been done" or "maybe if you..." Contrary to your perception there is very little threat of theft here. In fact R.G. and JM have both shared innumerable ideas that might have been patent worthy without reservation. I mention these two posters because... Well, you know why. Lighten up and settle in. Your a creative guy. There's an opportunity for you to help and be reciprocated here.

So just WTF are you eluding to? It could be a fun discussion that ends to your benefit! Don't imagine for a second that you have more on the ball in every possible aspect of design than everyone else here! But you are creative. And that means that your out of the box and possibly more likely to innovate. It's best to temper that with experienced minds for the best results. The opportunity is here if you'll only take it.

Where else can you go and find like minded individuals? Oh yeah, you've actually been restricted from a couple of other forums!!! No matter. This is the best one anyhow. And you know that by now. And we haven't run you off! Embrace your inner geek. Have an eggnog (tis the season) and let's refine some of these circuits that will make your amps special. Just leave the pride at the log in. There's no room for arrogance in design.

EDIT: This thread started with an idea that dates back to old school radio. And my last suggestion proposes the use of new technologies that would implement a reliable, regulated and low impedance bias supply that has never been done before. And I'm not running off to the patent office!!! It obviously caught your attention because you posted just to say 'I've got something on the ball too!?!' Why not share your ideas and let's see where it goes. Otherwise your stuck with one perspective. Your own. If your so sure that we have nothing on the ball or can't measure up to your superior intellect then stop posting here. Your other option is to participate. Likely to your benefit.

[mooreamps]

I thought everyone already knew what an AC regulator is...
I just only working with it because of the thermal impacts of DC regulators...

-g

[R.G.]

I thought everyone already knew what an AC regulator is...

There are several ways to do AC or primary-side regulation.

Ferroresonant (or constant-voltage) transformers come to mind as the simplest conceptual design, but about the hardest to really implement because of the need for a special transformer designs. Well, or using a second primary side ferro to regulate the incoming AC before it hits the main P/T. It's possible to do a ferro for secondary-side regulation, but those would be even more special-design than primary side ferros. And ferros are just not too adjustable for output voltage, either.

Variacs are nice, but they need a trained roadie watching them all the time. Secondary-side variacs work, I guess, but there's that special-purpose thing again, and heavy.

Tap changers are the poor man's variac; not too flexible, but at least possible to automate, whether as a true tap changer or a switch on bucking transformers.

Phase controllers let you regulate, but the resulting interference and control issues are ugly in a milieu which prides itself on no-solid-state. True as primary-side or secondary-side regulators.

Synchronous rectifiers work, but have much the same problems as phase control if you're using sine waves. And drive complexities if you try to do this on the primary side, as well as needing some kind of inverter after it on the primary side.

Rectify/chop/transform/etc/etc to make regulated AC works too, but the complexity of the controller and power electronics is large, and the bias against solid state is working against you again.

Motor-alternator schemes work well, but rely on special purpose - and HEAVY - parts. The field-modulated-generator is about the best of the MG things for getting regulated AC. You can do a motor-speed-independent FMG with some post processing of an alternator output to get any amplitude, phase, and waveform you like, but the electronics are complex again.

I don't seriously consider using a Great Big Amplifier (GBA, as opposed to BAGA) to make regulated AC from a signal generator. No one - except power testing labs, I guess - is that desperate.

So, which way did you mean? Or did I miss one?

I just only working with it because of the thermal impacts of DC regulators...

Yep, linear DC regulators with a high input-output differential are power eaters. Switchers aren't though.

Still, in a tube amp where 2/3 of the power into the amp is wasted as heat even for "efficient" Class AB amps, one wonders whether just using a fan or better heat sink is all that big an issue.

[g1]

So, which way did you mean? Or did I miss one?

When he said "primary side AC reg.." the first thing that came to mind was Carver's PM1.5 "Magnetic field coil power amplifier" .

[R.G.]

... and you remind me: I forgot one. Magamps. Low gain magnetic amplifiers can regulate AC power, although normal magamp practice (at least as it was back when people used magamps) would make them similar to phase control.

The Carver MFCPA was a design using a DC power supply with big sag on it, as I remember. Could have been phase control. I'll have to go look it up.

[Austin]

Rg, I am planning to try a variac on the secondary of a power supply in the next few weeks, I just won a couple cheap ones on ebay. I can think of many ways to use a movable tap like that... I wonder about the higher than 120v ac voltage but I think it will be ok, and anyway worse case it will just blow the fuse. Anybody else already try this?

[Chuck H]

I'm pretty sure that's what these guys do. Mojave Dirty Boy Amplifier Overview

The original amp was designed for player "Blues Sareceno" by his father. If you consider the nature of it, it's the first incarnation of power scaling. Which is now greatly refined and more cheaply and easily with SS devices than variable transformers.

[R.G.]

Rg, I am planning to try a variac on the secondary of a power supply in the next few weeks, ... I wonder about the higher than 120v ac voltage but I think it will be ok, and anyway worse case it will just blow the fuse.

Transformers, including variacs, are really funny about input voltage and frequency. You can saturate a primary (but not a secondary!!) by applying too much voltage times time to it. The designers set transformers up so that they work right at the maximum voltage-times-time most of the time.

If you apply too much voltage at the rated frequency, that kicks it over into saturation; likewise, running at LOWER frequencies even at the right voltages.

Putting significantly more voltage at the proper line frequency into a variac input will probably make it saturate. Saturation means that it quits doing a couple of things that are critical in transformers, those being the primary inductance keeping huge currents from flowing in the primary and not getting into the secondary, and a loss of coupling into the secondary. So if you're trying to put, say, 330Vac into a variac rated for 132Vac input, it almost certainly will saturate and will blow primary fuses.

That's fine if your fuses catch it before the variac or whatever is driving it die from overheating. The bad thing would be if the PT driving it dies before the fuse blows. I'd be really, really tempted to try this with a light bulb limiter first.

If you're hoping to use this in an amp, the better thing to do would be to use the variac on the primary side and put in a second small transformer to drive only the heaters. This lets you run the heaters on the correct voltage all the time, independently of what the variac is doing to plate and screen voltages.

[Chuck H]

If you're hoping to use this in an amp, the better thing to do would be to use the variac on the primary side and put in a second small transformer to drive only the heaters. This lets you run the heaters on the correct voltage all the time, independently of what the variac is doing to plate and screen voltages.

+++

Something like an "18 watt" PT that has a meaty 6V wind could be used for the preamp and filaments. Then a second HV transformer just for the plate and screen voltages. The Variac would go on the primary side of the plate and screen HV transformer. This MAY be what the "Dirty Boy" amp does. I dunno. I only know it uses a variable transformer to control the HV.

[Austin]

That makes sense and I already have an extra power supply so that is what I will plan to do.

So only theoretically speaking, a higher than rated voltage on a transformer primary or variac may be ok if it were also at a higher frequency to reduce the time? I find this stuff very interesting, thanks for the info guys.

[R.G.]

So only theoretically speaking, a higher than rated voltage on a transformer primary or variac may be ok if it were also at a higher frequency to reduce the time?

Yes. It's really linear - double the voltage, halve the time (by doubling frequency) and you're OK in terms of saturation.

Higher frequencies also let you put more power through. Power throughput is about linear with frequency too, until secondary stuff gets in the way. Aircraft and other military stuff used to run on 400Hz. That lets the put through the same power with a smaller transformer.

[Chuck H]

Just as a side note/inquiry... Anyone know WHY the standards of 50Hz/60Hz frequency?