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Help with hybrid mosfet valve amp

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Gentlemen:

I believe, that we need to give Nigel, the benefit of the doubt. Maybe the thing can do 300 watts, if more mosfets are added; with the proper HT.

But that information should be made public, or someone is setting themselves up for a lawsuit.

Yet as the circuit appears, there is only the ability to produce 80 watts into a good 4 ohm load. Driving a 2 ohm load or less, is pleading for trouble.

With 80 watts per channel, approx. 160 watts total peak, in stereo. It is still along ways away from 300 watts stated in the ad.

Adding the additional 4 mosfets, could bring the the module to 240 watts. But that would give you 480 watts into 4 ohms, stereo. A very hot load indeed, for a standard home system.

How much would a good T power transformer cost today for a 480 watt unit? Around $150.00 to $260.00 dollars, is that correct.

So lets see, $120.00 for the two modules, about $50.00 for the extra mosfets, plus T power transformer approx $180.00 average. Heatsinks, case, and misc. parts.

Hell, lets just buy a Moscode 401R.

Now that would be pricey Nigel. Not a good fit.

I added the $50.00 price for the mosfets, just in case we need "matched sets".

That is why, any mosfet design over 40 watts into 8 ohms or 80 watts into 4 ohm, is not a good idea. Because you have to buy more mosfets to get match sets. And it is foolish to do that, because by reducing the design to one set, no matching is required. Therefore, you can use those funds for buying better caps, resistors, wire, and connectors.

The other issues are these

a. Some people do not know how to match mosfets. Or do not have good equipment to do a good job.

c. People in some countries, can only afford a low cost multi-meter, that does not have the high resistance ranges for the task.

So we have to keep such things in miind, in our overall plannings.

Take Care

Ivey
 
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If you don't mind, I might follow this thread too, no experience of glass, limited experience of SS but I find the idea of hybrids interesting and the idea of low cost is good too because it encourages inventiveness - it's all too often easy to think you are making a good design by throwing $ at it. This way I figure I might learn something.

I'm more familiar with BJTs, so when I say I'm coming from the SS side of things, it might turn out that I'm a complete newbie to what you are planning if you go with MOSFETs :)
 
Bigun:

I would be honored, if you followed this thread. And I welcome your participation, in anything you wish to donate.

I believe that we all have god's gift of intelligence. We just need to express it.

Learning glass, valves, or tubes, is an easy master. The only confusing part is the output impedance. Most tube jockeys will not own up to it. But one of the most content problems in tubes is their impedance changes.

You see, it is known that as the tube heats up and cools down, the metal will flex. These small changes have an additive affect over time. To where the tube will arc over. This is due to the impedance changes. Even thou the tungsten is used in most tubes. It is a metal, and suffers from fatigue.

You can see this in cathode followers, when you are trying to get a correct loading of the cathode.

But all in all, it is the nature of the beast.

Glass theory is not hard. One of the secrets in learning glass theory; is to build the basic circuits and construct your loads lines, grid control/gain load lines, cathode bias loadings, and plate gain loading.

By swapping out the grid resistor, or the plate resistor; (and even the cathode resistor you can get a real view and understanding as to what tube is doing. So that when you want a certain tube in a certain circuit. You only need to check your paperwork, to come up with a solution for your project.

By doing your own experiments, on tubes, transistors, fets and mosfets. You can catalog all that information, for future use in future projects. And it will all start to fall in place.

I have money that I could spend. I have family, (who for reasons unknown to me) who are always willing to give me thousands of dollars. I know there got to be a catch in there somewhere.

But hard times are ahead, and I would like to hang on to some of my funds.

Yet together we can build master pieces of equipment. For very little money.

I salvage 80% of my parts from TV's, monitors, disgaraded industrial electronic equipment, and huge office copiers.

I feel and believe that you will learn a great deal from this forum. There are a lot of wonderful people here. Willing to pass on knowledge and assistance that will have performing electronics on the fly.

You will do great.

Now I must see a man about a PCB package.

Take Care

Ivey
 
Nigel!!!!!!!!!!!!! Its YOU!!!!!!!!!

You are the guy selling the PCBCAD30 and 40 software CD's on UK eBay.

Please Nigel, I want one. Can you send me one for free, as a demo. Please.

Come on Nigel, help an old guy out. Allow me to save and keep my little pension funds.

I want to see what it can do or can not do.

Maybe I can even assist you in selling them. I know hectares of people in the Silicon Valley area, that are looking for an inexpensive PCB package, to replace Altium,s and Orcad's hold on them.

I will test it, pamper it, and caress it, until it performs like a humming bird.

I only request one cd; or You can even email it to me, and save on the post.

What to say to it, Nigel? Just one download. One.

I am waiting

Take Care

Ivey
 
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If you don't mind, I might follow this thread too, no experience of glass, limited experience of SS but I find the idea of hybrids interesting and the idea of low cost is good too because it encourages inventiveness - it's all too often easy to think you are making a good design by throwing $ at it. This way I figure I might learn something.

I'm more familiar with BJTs, so when I say I'm coming from the SS side of things, it might turn out that I'm a complete newbie to what you are planning if you go with MOSFETs :)

Hey, nobody can track you following this thread (as long as you're wearing your tin foil hat that is) so have no worries regarding your participation :)

Frikkin edit: tube hybrids are usually just simple source/emitter followers after VAS stage, because one want to getr rid of the OPT. There's no magic in it.
 
Doing the Dew

Alright now Gentlemen:

Those that are skilled in electronics, know that Tube/MosFet Power Amplifiers are somewhat simple. They are made up of the following sections

1. A vacuum tube voltage gain stage
2. A vacuum tube voltage impedance stage/w voltage gain less than .999.
3. Some have a bias circuit.
4. The Final Main Amplification stage.

There is also the PSU's. reguators either solid state or tube. Plus the heater circuit.

The one advatage that hybrids gives its owner, is the combination of the anolong smoothness of tube and the fast switching of solid state.

This combo can provide the listener with good bass and sharp clean highs and mids.

I have found a schematic of the MosCode 300, on the Web. And I am posting it.

Look it over, and for those who are not heavy into electronics at this time.
Talk it through with someone who is.

Later, I will post the original schemtic of the MOSCODE 300. So that we can compare them.

Take Care

Ivey
 

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Hi Wavebourn:

I do not think that the MosCodes would sound better than any other power amplifier actually.

It does sound good. Great..., that is a horse with a different color.

I am not pushing hybrids because I care for them more than other power amplifiers. I am pushing them because they sound more linear than BJT's power amplifiers. They use some vacuum tubes and they are less expensive to build than an "all tube" power amplifier.

Vacuum Tubes pricing have gone through the roof. And it is all because the items are no longer made in the USA. And I feel that it is a crime that retailers are fleecing those that desire to use vacuum tubes.

It cost no more to import items from one country to another. The Free Trade Act, reduced tariffs, and reduced import fees and government incentives towards Imports and Importers, have reduced the cost of imported goods to America.

The problem today in our nation, is that Manufactures, Importers and Retailers; are passing not only their overhead costs on to the customers. But any and all costs that they may incur.

They have started this ripple effect throughout the commercial system. That is draining the savings and the life out of most citizens in this country.

I enjoy the sound of good iron and glass. But at the prices being charged today; I can not afford it. So my hobbies and past time is being threaten by the greed of Wall Street and their BMW driving crowds of yuppies.

So I am trying to get people to think hybrid. To think cost cutting, in an effort to keep the hobby affordable. I am thinking promote "through the hole" electronic parts. Because it is too difficult to remove and reuse SMD parts.

I am a jazz guitar player. I love a good sounding tube amp. But it costed me close to $100.00 to re-tube the Super Six Fender Amp, I once owned. So I sold it.

And I built a 100 watt, hybrid unit. It uses one vacuum tube.

If we can get people into designing more and more hybrids. We can produce better and better units. Until we have designed the best that we can produce.

I want these young men and women to see that with a little knowledge. They can do great and wonderful things.

Take Care

Ivey
 
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If you are trying to get people to think hybrid, you are knocking to widely open gates. There are many hybrids here on Vacuum Tube forum.
If to speak of the classical understanding of "Hybrid", that means tube input / SS output, I myself started a thread about my Tower amp design.
The purpose of it is not just to push prices down; it is to push down price / quality of sound ratio.

How did I come to hybrid amps?

From PP amps with power tube outputs to SE amps with tube outputs. Then, to SE amps with tube cathode followers loaded no CCS with parafeed transformers, then to a tube output amp loaded on aCCS with uto - transformer. All the way I was getting better and better sound quality, especially fine details like reverberation and sound decay, but the biggest improvement was when I used a source follower loaded on CCS with no transformer at all. The schematic diagram of that very old my experiment is attached.
Then I started improving the source follower itself minimizing modulation of parameters of the MOSFET with voltages and currents. The first amp was called Tower - 1, because it had very tall heatsink. Currently, I am working on my Tower-V model, with the same tall heatsink. I hope if will serve as a prototype for production: kits for DIYers and assembled, tested and supported High-end power amps.
You can find description of the project on this forum, with pictures and other details.

The bottom line is: instead of trying to pull the weakest point of SS amps -- complementary output followers -- to the tube world spoiling it such a way, it is better to concentrate on improvement of sound quality that combination of tubes and solid state devices offer.

I myself have a MS of EE degree; I am not a novice both on stage and in listening rooms, so I know what I am talking about.

Now, here is the schematic of that my hybrid that many years ago inspired my on further work in this direction:

Tower-I.gif
 
Wavebourn:

I reviewed your thread on the building of your Tower III power amplifier unit. It was indeed a very nice thread. Your methods and constuction, took me back to 1944. When as a child of 10, I met my first Russian techs, at a weapons factory around Philly. They were sent there to help in the making of the Russian submachine guns PPHS. It did not look as beautiful as the Tommy Guns that I grew up knowing.

My next encounter with Russian citizen was in 1993. I was part of a team that went to Vladivostok, to check out a problem there.

You are an electronic engineer, so this is what have to say.

In your design, you are using CCS, Gyrators, and a host of other circuits that far above the forum members that I am trying reach. I am trying to guide these persons toward audio electronics understanding at a level that they will feel comfortable at.

Example:

You are using the tube that we in the USA call the "6BM8". The screen grid is being used to convert it into a triode. Which is normally not good practice. But the CCS will insure that the plate voltage remains somwhat stable. Allowing good current draw and protecting the tube.

What about a newbie? Will they understand what they see?

You have years of designing and construction to draw from. And that is outstanding. So, can I count on you to assist me in trying to bring some lost souls up to our speed.

To teach and train them over the internet, to the world electronics that you and I enjoy, and draw solace from.

I can talk of servo amps, synchro amps, magnetic amplifiers, forward feed shunt regs, and host of other things. But I am here for them, as are you.
Lets work together. Please.

I saw in your thread, where you made your PCB boards. It brought a smile to my face. It reminded me of my days in 1957 when we making PCB boards that way. Only a little more refined.

I am going to tell you a secret/trick that we used back then. A drafting eraser templet, blue masking tape, and a razor blade.

Use the masking tape to cover the board. Make mirror drawing of your circuit. Place the drawing over the board. Label the board, east, west north, and south. Which an awl. Punch a small hole through the paper into the tape and on to the copper board side.

Next lay the drafting eraser templet from hole to hole. The templet has straight lines in two widths sizes, curves, circles, for using the razor blade for cutting out the pattern on the tape. Once you have done that. Peel the cut tape, out of the pattern.

Now instead of paint, we used the paint that you can obtain from silk screening supply houses, a paint made for PCB's to paint the pattern in with.

Once the paint has dried. Peel off the blue masking tape. The blue tape is designed not stick and hold on to the surfaces. It will come up very easy.
Leaving no glue behind on the board.

Etch the board, clean it, and it is done.

Here some of my circuits that I made for this thread. With lots of Wima Caps.

Take Care


Ivey
 

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Thank you Ivey, indeed there were different ways to make nice looking PCBs, the same way like to develop black and white films manually, when other technologies were not available. But my purpose was just to make a functional board, not for sale, not for a show, so I used old good fast method: a paint and a feather. For production run I will use computer software and order boards in China.

If you follow the forum carefully, especially some old threads, you can see that there are very well educated DIYers here, who have no degrees in Electronics. For example, I considered SY as an electronics Engineer, but when met him personally I've discovered that he is a Chemist! And other folks, who taught me many new approaches and tricks here on the Forum; all of them are here, and I am still learning! So, gyrators, current sources, voltage regulators, and other things that you call complex, are well known here, and well accepted already.

I agree with you about helping and teaching; you are knocking to the open gates again! But I am here to learn, as well...
 
Trade!!!!!!!!!!

As you guys and dolls can see, I have lots of Wima Capacitors for trade. I like Wimas, I prefer Illinois MKS or MKP capacitors, at 5 to 10%

My Wimas are MKP10 250 volts, 400 volts, 600 volts. 5 and 10%

There are a lot more.

Take Care


Ivey
 

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Wavebourn:

Some day, I hope to meet you in person. Being in Pleasant Valley, you go to Carson City, at times? A nice place.

Of all my time in California, over the many years that spent there/here. I never went to Pleasant Valley. Heard about it, yes. Been there, no.

At this time, I am in San Diego. I will not be here long. I will return to my eastern home. I love the seasons. Besides California has always upset me with its very strange and none sense laws. I just vacation here now.

Yes, I agree with you that quick and easy, down and dirty; does have its callings. But perfecting a quick and easy method to near beauty, is also a good calling.

I have worked for the government, for a very long time. Retired I am, now. But I miss some portions of my career.

If we meet, we will have a lot to talk over. My fields were mainly aircraft electronics, and submarine anti-submarine electronics, from the view of the submariner. Silent electronic warfare.

No, I do not consider those circuits complex, from my stand point. I was viewing them from the vantage point of a new comer to electronics. Some will catch on quickly. Others may not.

I guess I've been around the military too long. We leave no man or woman behind. So when I think of helping someone, I do not want to lose that person because I will not come down to their level of education. It is an honor to me, that someone is willing to allow me to add something to their life. Regardless how small or in some cases, unimportant.

When I was young, I was like a rooster in a hen house, just showing off my stuff. Now at my age, it is just a pleasure to have young people look to you for wisdom.

I will try to be on this forum as long as I can. Gods willing. So we can talk and exchange ideas and views on many a topic. I would like to be a friend in your corner. As you a friend in mind. God bless you Wavebourn.

Take Care


Ivey
 
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