Hi all !!
I ask a question.
Some say that an amp with only two stages is better, perhaps because it has fewer components, it achieves a better sound than with three stages.
In any case, the two stages may need preamp.
And the three stages may not need a preamp.
We lose sound quality with one more stage in the amplifier?
Maybe two drivers can work with less distortion than just one driving a 300B with 200vpp?
Santiago
I ask a question.
Some say that an amp with only two stages is better, perhaps because it has fewer components, it achieves a better sound than with three stages.
In any case, the two stages may need preamp.
And the three stages may not need a preamp.
We lose sound quality with one more stage in the amplifier?
Maybe two drivers can work with less distortion than just one driving a 300B with 200vpp?
Santiago
Attachments
santitrucco,
The first problem seems to be that you want to build a 300B amplifier that has -100V grid bias.
The original design of the 300B tubes did not include the use of grid current.
So . . . the driver does not need to do 200V peak to peak, look and see why:
Take a look at a set of 300B grid curves, and try to find a linear portion that goes from 0V to -200V on the grid.
If you want to operate the 300B that way to get more linear power out of it . . .
Then consider using a more powerful tube.
The above discussion is only my opinion.
And . . . "All Generalizations Have Exceptions" - Me.
Now that we have eliminated the need for 200V peak to peak driver to drive a 300B . . .
Your original question that asks is 2 or 3 stages better for a 300B amp . . . remains unanswered.
I will let someone else discuss that age old 2 or 3 stage question.
The first problem seems to be that you want to build a 300B amplifier that has -100V grid bias.
The original design of the 300B tubes did not include the use of grid current.
So . . . the driver does not need to do 200V peak to peak, look and see why:
Take a look at a set of 300B grid curves, and try to find a linear portion that goes from 0V to -200V on the grid.
If you want to operate the 300B that way to get more linear power out of it . . .
Then consider using a more powerful tube.
The above discussion is only my opinion.
And . . . "All Generalizations Have Exceptions" - Me.
Now that we have eliminated the need for 200V peak to peak driver to drive a 300B . . .
Your original question that asks is 2 or 3 stages better for a 300B amp . . . remains unanswered.
I will let someone else discuss that age old 2 or 3 stage question.
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6A3sUMMER thanks.
Think of a 300B amp, which has an exciter valve that delivers what it takes to get the most out of the 300B.
Maybe 200vpp is too much.
But I was thinking of a 2 or 3 stage amp that uses 300B.
Santiago.
Think of a 300B amp, which has an exciter valve that delivers what it takes to get the most out of the 300B.
Maybe 200vpp is too much.
But I was thinking of a 2 or 3 stage amp that uses 300B.
Santiago.
What is a "preamp"? Often, just one more stage.
"the two stages may need preamp" so 1 + 2 = 3
"the three stages may not need a preamp" so just 3
Electrically the same.
Electrically the same but better with the integrated, four less connections per channel plus whatever cable in between. Shorter AC current loops and .. well anyway, its better.
HK
HK
The problem with three stage 300B amps like the one you posted is that there's too much gain. You can make a second stage a cathode follower to get around that, but a tube like the 5687 doesn't have enough gain for that architecture to work properly either. For modern HiFi systems, a driver gain of 30x-50x tends to work pretty well driving a 300B. A single 12AT7 will do this nicely.
The 845 is a little different because it needs +/-150V peak drive to make full power. The 6HV5 has a very high mu, so you can get away with a two stage amp by using this driver tube, but normally a three stage amp is mandatory to make a 20 WPC 845 amp.
The 845 is a little different because it needs +/-150V peak drive to make full power. The 6HV5 has a very high mu, so you can get away with a two stage amp by using this driver tube, but normally a three stage amp is mandatory to make a 20 WPC 845 amp.
Work backwards when designing an amplifier. Determine your power output, that will define the gain you need - then you can decide how (two or three tubes, IT, preamp, integrated) you want to achieve that.
Hi, i have, 6E6P-DR, 6E5P, D3a, 6S45p, 46, 56, 76, for use like driver or input tube.
I have Mundorf Silver Gold oil caps for use like coupling , and i have Lundahl LL1671-30mA interstage transformer with Option 1:2.
Maybe 6E6P-DR ( 33 Factor Gain ) and 1:2 Interstage Transformer would be enough.
Sometimes I think to use 6E6P-DR input tube, Capacitor coupling, 46 driver tube, Lundahl 1: 1 Interstage transformer, and 300B.
At other times i think I could use 6E6P-DR then 1:2 transformer and 300B, it would be as few components as possible.
I would like to know if using few and good components would be an advantage, over using more components.
Assuming that the voltage gain obtained was the same.
Santiago
I have Mundorf Silver Gold oil caps for use like coupling , and i have Lundahl LL1671-30mA interstage transformer with Option 1:2.
Maybe 6E6P-DR ( 33 Factor Gain ) and 1:2 Interstage Transformer would be enough.
Sometimes I think to use 6E6P-DR input tube, Capacitor coupling, 46 driver tube, Lundahl 1: 1 Interstage transformer, and 300B.
At other times i think I could use 6E6P-DR then 1:2 transformer and 300B, it would be as few components as possible.
I would like to know if using few and good components would be an advantage, over using more components.
Assuming that the voltage gain obtained was the same.
Santiago
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Have a look at the thread on "300b SE with a DHT driver" where we have been discussing just this. My solution is opamp 5.5x gain > 46 > 300b. Ale Moglia is step-up input transformer > 47 > 300b. I would use the 46 and then add gain on the input in either of these ways. I personally prefer DHTs and don't like 3 stages of tubes, others vary. As has been said, only use the amplification you need, nothing more.
My preferred approach now is to use a pentode input stage with a high-impedance load to get lots of gain and then burn off any excess gain with a local feedback loop and increase linearity.
I could easily 2-stage an 845 amp with very low distortion and whatever sensitivity I want that way. I just completed an SE breadboard amp with 2 amplification stages that drives a transmitter tube to 19W on 0.7Vrms input. Distortion at 1W was 0.027%.
If you want gain in one stage, make it. If you want to cascade more lower-gain stages together, then do that. Decide what you want and make it happen.
I could easily 2-stage an 845 amp with very low distortion and whatever sensitivity I want that way. I just completed an SE breadboard amp with 2 amplification stages that drives a transmitter tube to 19W on 0.7Vrms input. Distortion at 1W was 0.027%.
If you want gain in one stage, make it. If you want to cascade more lower-gain stages together, then do that. Decide what you want and make it happen.
santitrucco,
Try to relax.
Stop looking for the perfect 300B amplifier.
What is perfect for you, may not be perfect for someone else.
Decide, get the parts, lay it out, and build it!
You might be surprised, you may love it.
Then report back to us.
Try to relax.
Stop looking for the perfect 300B amplifier.
What is perfect for you, may not be perfect for someone else.
Decide, get the parts, lay it out, and build it!
You might be surprised, you may love it.
Then report back to us.