• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

What makes is stereo?

freestream

Member
2010-09-06 3:34 pm
Hi

Iam currently reading about tube amplifiers and the technology behind it. I have read several manuals and walkthroughs for different kinds of amplifiers but it is one question that i never get answered. It might be a really stupid question but i need a answer for it before i can understand the whole process. What is it that make it a stereo amplifier? first i thought it might be because of the amount of tubes. That in a stereo set both LEFT and RIGHT is treated as mono channels and is amplified separaty. But now i have now seen amplifier with one tube that still have stereo. Can someone explain this for me? :confused:
 

freestream

Member
2010-09-06 3:34 pm
Stereo by definition is two channels, Left and Right. The left and right channels drive the appropriate left and right speakers.

This allows for spatial intrepretation of the sound.

If bridged it is no longer stereo.

Can you post the schematic of the one tube stereo? or a link to it?


Right now i do not have any complete schematic, iam still working on it. So, with other words, if i only use ONE tube I can only get mono?
 
The 572B is a High Mu triode, directly heated, similar to 811A.

You will need more than that to make an amp. It is suitable as an output tube and might work well in a SET (Single ENded Triode) amp. However, it is a High Voltage tube and I would not recommend making anything with it unless you had a lot of experience.

Danger High Voltage can be lethal!
 
Thanks guys now i think i got the hang of it. If i understand it right i should first settle for what tube i want to use and from that choise make a fitting schematic.
Right now i just have a mental image of how i would like to desin the amp. I am a big fan of the big tube, like the size of 572B. I whould like to build a stereo amp (not just a pre amp, it should be strong enough to be standalone and power 2 speakers) with just 2 big tubes. If 572B is a bad choice due to it is High Voltage tube, do any of you know a big tube that is not High Voltage but can still amplify a grate deal?
 
If you are going to drive speakers, you will need more than two tubes. The 572B requires substantial input voltage to operate proeprly.

It is specified for 2400V plate supply. I can't see it operating with less than a 1000V supply, and that is not an amp I would recommend anyone building unless they have a great deal of experience with electronics, high voltage and tube amplifier design. In addition it would probably take a hundred volts p-p grid drive to operate properly, and you will need additional gain stages to get there. If I read the data sheet correctly it requires up to 100mA of positive grid drive. Another strike against it.

It sounds like you want to build a 2A3 or 300B Single Ended Triode amp. It will take at least four tubes plus a power supply rectifier tube if all tubes.

I suggest you read Valve Amplifiers By Morgan Jones before you proceed any further.
 

ChrisA

Member
2008-01-08 12:22 am
Thanks guys now i think i got the hang of it. If i understand it right i should first settle for what tube i want to use and from that choise make a fitting schematic....

I think this is backwards. Best, I think, that start with a specification for the amp you need. For example how much power do you need. is 5W enought or do you need 20W.

But you might even want to step even farther back and ask what is the puirpose of this amp? In my opinion, if this is your first amp the purpose should be mostly educational and you should pick a design that is easy to build and low cost

The biggest and most common beginner's mistake is to build your "last amp first". No, build an easy one and learn and then build a more complex amp and so on. Don't short cut the process.

Try a single ended amp based on a 6V6 tune and 12AU7 pre-amp/driver. This is easy to build and debug and the cost is reasonable, expect to pay $30 for each transformer and $10 for each tube. This amp sound good and has about 5W per channel. This can be a very good amp for playing in an office using small "full range" speakers. The 6v6 has a smooth tube sound and is cheap. It also works well on a 200V supply which is a reasonable voltage for a first tube amp. Although 200V is still dangerous
 
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M Gregg

Disabled Account
2010-06-28 11:04 pm
UK
Hi

Iam currently reading about tube amplifiers and the technology behind it. I have read several manuals and walkthroughs for different kinds of amplifiers but it is one question that i never get answered. It might be a really stupid question but i need a answer for it before i can understand the whole process. What is it that make it a stereo amplifier? first i thought it might be because of the amount of tubes. That in a stereo set both LEFT and RIGHT is treated as mono channels and is amplified separaty. But now i have now seen amplifier with one tube that still have stereo. Can someone explain this for me? :confused:

Can I just ask what have you built before?

Regards
M. Gregg
 
Do you actually want to build an amplifier for listening to music, or a piece of art/furniture for looking nice in your house?

If you want to listen to music, then you might be better off starting (if this is your first piece of DIY electronics) with a chip-based amp. Safer, easier, cheaper. Once that works OK, then learn about audio and tubes. Or buy a kit.

Ask yourself: if you build a tube amp and it doesn't work, how are you going to debug it? Sorry to sound negative, but I am trying to save you from a lot of frustration.
 
I'll just note that some 'stereo' amplifier schematics may only show one channel. So you will have to build two 'signal' sections to get both channels.

As other said, start simple. A preamp is the best way to get into tubes. Less expensive and easy to debug. Buy an old Dynaco 70 or maybe a kit amplifier - going through either will give you a good idea about wiring practice and layout.
 
You could use ELL80 or 6360 (=QQV03-10). But why?

ELL80 makes a cute little amplifier... not much power (~3/4 w in triode)

dave
 

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Two 6LU8, 6EM7, 6BM8 etc will make a complete stereo amp. I think I saw something somewhere where someone made a stereo amp out of a dual power tube using input transformers for some voltage gain to drive them. Sorry I don't remember which output tube or where I saw it.

I think that unless you have parts on hand that you want to use you should start by determining what you need in an amp and the features you desire. Then you can decide on the appropriate parts to use to achieve those goals.
 
I have done several elektronic projects before, both hi and low voltage. The thing is that I have never worked with tubes before so that is a first for me in this build.
Sure, I have no problem with building a pre amp first. I have found several schematics for thoes so that should not be a problem.

And yes, i do know how to make diagnostics on the equipment so then/if i run into a problem it will not be a dead end, just another obstacle.

I have read some guides, including the "beginners guide" from boozhoundlabs (Boozhound Laboratories). Is there any other guides you might recommend to learn more about the tubes?

The purpose of the amp should be to play music and to have stereo sound (not mono). Now then iam going to start with building a pre amp iam going to build it for a turntable. Does that sound like a better plan? like this design http://phonoclone.com/images/p6dj8_cir.gif ? or do you know any better schematic for a pre amp stereo amplifier for turntables?