Hey arcorob, I'm glad you were able to dig into your amp with enough determination, skill and insight to solve it's issues and end up with an awesome result. Just like with tubes (which ones sound better), there is no settled consensus on what constitutes DIY. Personally, I think that if someone modifies an existing/pre-built component, and makes it work better that's DIY. You set a goal and you "did it yourself." So, thanks for sharing all your intensive work and your thorough documentation. It will certainly benefit other owners of the K4040.
What I was getting at in my post above is that a tube is what it is. I certainly can't go inside a tube and modify its internal parts to make it safely operate at higher voltages or current. So, if I want to use EL84's in an amp designed for 6L6GC's I'd need to make a lot of changes to the amp - almost rebuild it. But, that doesn't mean there's anything wrong with EL84's. It just wouldn't be the right amp for them. So, a tube is what it is. Whereas, an amp can be modified, or completely rebuilt. Thanks.
What I was getting at in my post above is that a tube is what it is. I certainly can't go inside a tube and modify its internal parts to make it safely operate at higher voltages or current. So, if I want to use EL84's in an amp designed for 6L6GC's I'd need to make a lot of changes to the amp - almost rebuild it. But, that doesn't mean there's anything wrong with EL84's. It just wouldn't be the right amp for them. So, a tube is what it is. Whereas, an amp can be modified, or completely rebuilt. Thanks.
Thank you !!! It was as simple as that !! It’s like I like the sound of AT cartridges over Ortofon. Person b might like ortofon better. And I agree , what the design works best with… now factor in tube brand differences in sound.. eyyyyyyy… my journey . Lol
again many thanks
What about a toaster? honestly, as good as it may sound, I'm not impressed by the design.
If you adjust the 6L6GC and the EL34 for the same plate to cathode voltage, same screen to cathode voltage, and same total cathode current, then the plate + screen dissipation is exactly the same.
That means the plate plus screen dissipation heating total is exactly the same.
6L6GC filament 6.3V @ 0.9 Amps = 5.67 Watts.
EL34 filament 6.3V @ 1.5 Amps = 9.45 Watts.
That is 3.78 more watts filament heat in the EL34.
The glass envelope of the 6L6GC has about 1.5 x to 2.0 x the surface area of the smaller EL34 glass envelope.
Given 3.78 Watts more total heat in the EL34, which tube do you think will run hotter?
I hope you see that the EL34 will run hotter when the screen and plate dissipation is equal for both tubes.
Rules of thermo dynamics for the additive heat in a glass envelope, is a little like the rule of the additive power of two Gaussian noise sources in one circuit.
Just my opinion.
That means the plate plus screen dissipation heating total is exactly the same.
6L6GC filament 6.3V @ 0.9 Amps = 5.67 Watts.
EL34 filament 6.3V @ 1.5 Amps = 9.45 Watts.
That is 3.78 more watts filament heat in the EL34.
The glass envelope of the 6L6GC has about 1.5 x to 2.0 x the surface area of the smaller EL34 glass envelope.
Given 3.78 Watts more total heat in the EL34, which tube do you think will run hotter?
I hope you see that the EL34 will run hotter when the screen and plate dissipation is equal for both tubes.
Rules of thermo dynamics for the additive heat in a glass envelope, is a little like the rule of the additive power of two Gaussian noise sources in one circuit.
Just my opinion.
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Bah Ha! It's like how dare you claim you actually achieved the illusive satisfaction with what you've done with "an amplifier"... There must be 110 things still wrong with it.
And with a given cathode resistor, which one is going to bias up to a higher current?
Given the differences in heater power, which will have a higher current capability (at vg1=0)?
If given that either has enough current capability to drive Zload, what happens to the tube that has too much current capability? (Where does the current try to go?)
The answers might give insight into why the EL34’s blow up. Hint: look for glowing grids.
Given the differences in heater power, which will have a higher current capability (at vg1=0)?
If given that either has enough current capability to drive Zload, what happens to the tube that has too much current capability? (Where does the current try to go?)
The answers might give insight into why the EL34’s blow up. Hint: look for glowing grids.
Well I changes the driver to an LPT and put 6550's in mine. The mains transformer is generous in its rating. Got quite a lot more output power. Was very pleased with the mods.
I really love how the expert officials police have chimed in ( having of course never worked on one or heard one). Their design will always be a better design. Who cares if the net result sounds like crap. At least it is engineered correctly and uses the tubes they want and not the ones that give better sound across the spectrum, great soundstage and separation. Bunch a geeks.
reminds me of the story of sound city. A recording studio that the room should have been acoustically awful, is a legend. Go watch the documentary some time.
Bottom line, you can cast stones all you like, but I am not the one losing out.
Oh and the toaster comment ? Because I said it looked good? But you think that’s it. Well Martin Logan’s are ugly as sin but go ahead and debate their phenomenal sound.
piece of advice for the naysayers. Get your head out of the schematics and really listen. Then and only then can you experiment. Good night all.. seems I came back to one of the forums I left for damn good reason years ago
reminds me of the story of sound city. A recording studio that the room should have been acoustically awful, is a legend. Go watch the documentary some time.
Bottom line, you can cast stones all you like, but I am not the one losing out.
Oh and the toaster comment ? Because I said it looked good? But you think that’s it. Well Martin Logan’s are ugly as sin but go ahead and debate their phenomenal sound.
piece of advice for the naysayers. Get your head out of the schematics and really listen. Then and only then can you experiment. Good night all.. seems I came back to one of the forums I left for damn good reason years ago
I know your a bit critical about the opinions. I liked the amp and modified it which taught me much about valve amp circuits. Putting in 10KHz sinewave and getting out a triangle horrified me.
Discovering the shortcomings is interesting. It also encouraged me on to try designing and building for myself. Its not always about the audio but the electronics too.
Discovering the shortcomings is interesting. It also encouraged me on to try designing and building for myself. Its not always about the audio but the electronics too.
Arcorob,
If you are still there. I am happy that you like it! I saw several people at this forum building nice things and the suddenly disappearing. I like to think they are so happy listening to the music that they forget the forum. I also once read a comment that if you ask 10 specialists about the best 300B amplifier, you will get 11 responses. So this is what happened here as well? And, also develop an understanding why a certain valve, generally good in audio, does bad in the Velleman?!
Best, erik
If you are still there. I am happy that you like it! I saw several people at this forum building nice things and the suddenly disappearing. I like to think they are so happy listening to the music that they forget the forum. I also once read a comment that if you ask 10 specialists about the best 300B amplifier, you will get 11 responses. So this is what happened here as well? And, also develop an understanding why a certain valve, generally good in audio, does bad in the Velleman?!
Best, erik
I'm sorry for making fun of its looks. I am sure it sounds great, and I wish I had one. enjoy it!
Of course. Supposedly Jim Marshall opted for ECC83 as the PI 'cause he didn't want to stock more than two different tube types to make his amps. Other manufacturers, such as Fender and Hiwatt, instead used 12AT7's in their LTP's.
Best regards!
Hopefully this was just a typo. Or did you really want to compare apples with, say, currant?
Best regards!
wg_ski,
Where does the extra current go?
What extra current?
I am not sure what you meant.
No tube puts out more current than:
The combination of the plate to cathode voltage, screen to cathode voltage, and control grid to cathode voltage 'dictate' to the tube to put out.
A tube that has a cathode and plate that is capable of 1/2 Amp peak current will not put out any current at all, if the control grid to cathode voltage puts the tube into cut off.
The motor in most cars does not automatically set itself to 7,000 rpm, and 200 Horsepower.
When you floor the gas pedal, then it attempts to put out the max rpm and maximum horsepower.
If it is in neutral, it puts out maximum rpm, but it does not put out full horsepower, it needs the exact correct torque load to put out maximum horsepower.
The numeric value of horsepower, bhp, and the numeric value of foot-pounds of torque are equal at approximately 5250 rpm.
Likewise, a light load on a tube amplifier will not allow the amplifier to put out its maximum power (maximum voltage yes, max power no).
And, if there is no signal to the control grid, most amplifiers do not put out anything except hum and noise.
So much for all that 'wasted' current capability.
The wasted 'excess' current capability is there if the signal level, amplifier design, and the load dictate that full current capability.
Glowing grids?
It has to be extremely far into class A2, AB2, B2 to make the control grid glow. Ouch!
It has to be exceeding the maximum screen dissipation. Ouch!
Some screens have deformed enough to short to either the control grid, or the suppressor grid / beam former plates. Ouch!
Where does the extra current go?
What extra current?
I am not sure what you meant.
No tube puts out more current than:
The combination of the plate to cathode voltage, screen to cathode voltage, and control grid to cathode voltage 'dictate' to the tube to put out.
A tube that has a cathode and plate that is capable of 1/2 Amp peak current will not put out any current at all, if the control grid to cathode voltage puts the tube into cut off.
The motor in most cars does not automatically set itself to 7,000 rpm, and 200 Horsepower.
When you floor the gas pedal, then it attempts to put out the max rpm and maximum horsepower.
If it is in neutral, it puts out maximum rpm, but it does not put out full horsepower, it needs the exact correct torque load to put out maximum horsepower.
The numeric value of horsepower, bhp, and the numeric value of foot-pounds of torque are equal at approximately 5250 rpm.
Likewise, a light load on a tube amplifier will not allow the amplifier to put out its maximum power (maximum voltage yes, max power no).
And, if there is no signal to the control grid, most amplifiers do not put out anything except hum and noise.
So much for all that 'wasted' current capability.
The wasted 'excess' current capability is there if the signal level, amplifier design, and the load dictate that full current capability.
Glowing grids?
It has to be extremely far into class A2, AB2, B2 to make the control grid glow. Ouch!
It has to be exceeding the maximum screen dissipation. Ouch!
Some screens have deformed enough to short to either the control grid, or the suppressor grid / beam former plates. Ouch!
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Sounds to me like you know exactly where it goes. Once you make the plate eat all the current it can given the load, any increase in vg1 results in an increase in Ig2. None of which contributes to more output power.
If one tube poops out at 300 mA and another at 400 mA, with a given fixed Vg2 two things can happen. If you ask for 400 mA, the one that can only deliver 300 will limit, while the other will increase it’s output until you‘re getting your 400. If the load won’t eat more than 300 mA, the one that can deliver 400 will have its screen heat up and the one that stops at 300 mA won’t. The way to prevent these problems is to adjust Vg2 so that you run out of current at the right place. The same Vg2 setting will not work well for both tube types. It’s not just plug and play, and the 6L6 and EL34 will have different optimal loads given a fixed Vg2 (or vg2 relationship to plate, if you’re running UL). You don’t take this into account, something non-optimal happens. In the worst cases, melted screens which short everything out internally. Large screen stoppers can help because it drops Vg2 dynamically as you draw g2 current, but it is a high distortion mode of operation. It’s what you do in a guitar amp when 5 or 10% is welcome.
Hi, no typo. It's just an extreme example I used to illustrate how using the wrong fruit in a particular amp recipe doesn't mean the fruit is bad.
Scratch that, I meant to say tubes and amp circuits. That was a typo.
wg_ski,
I am glad that you explained that the g1 and g2 currents were what you were talking about.
As long as we are talking about extra currents, do not forget the current in the Suppressor Grid or the Beam Formers.
I think this thread's original post was about a Velleman Hi Fi Stereo amplifier that was designed and intended to operate in AB1.
You can operate such amplifiers into AB2 if you wish. Just be ready for Bias Shifts if you do.
You can remove the regulator of a 1978 Jetta engine, and then you can get way more than the formerly regulated 7000 maximum rpm.
Just be ready for the "distortion" of the engine parts that you get at higher rpm.
As to Guitar amplifiers, the output tube stages certainly are allowed to, and are used to put out 5% or 10% distortion.
And . . . do not forget about the undersized output transformers that are saturated, adding their own distortion to the tube distortion.
Hi Fi / Stereo playback
Guitar Amplifiers
Apples
Oranges
Just my opinions
I am glad that you explained that the g1 and g2 currents were what you were talking about.
As long as we are talking about extra currents, do not forget the current in the Suppressor Grid or the Beam Formers.
I think this thread's original post was about a Velleman Hi Fi Stereo amplifier that was designed and intended to operate in AB1.
You can operate such amplifiers into AB2 if you wish. Just be ready for Bias Shifts if you do.
You can remove the regulator of a 1978 Jetta engine, and then you can get way more than the formerly regulated 7000 maximum rpm.
Just be ready for the "distortion" of the engine parts that you get at higher rpm.
As to Guitar amplifiers, the output tube stages certainly are allowed to, and are used to put out 5% or 10% distortion.
And . . . do not forget about the undersized output transformers that are saturated, adding their own distortion to the tube distortion.
Hi Fi / Stereo playback
Guitar Amplifiers
Apples
Oranges
Just my opinions
