Why these are not commonly used in tube amps

Alan, you say you can't listen to horns, maybe what you are hearing is artifacts from the amps. I use Altec's on my PP Mac MC40's and get zero listening fatigue. A lot of folks can't listen to horns on SS amps it seems. I've never tried it, sometime I will. I just know that a few watts can push them loud with no distortion and the dynamics are incredible. I've listened to some very expensive speakers and walked away very unimpressed.

BillWojo
 
Alan, you say you can't listen to horns, maybe what you are hearing is artifacts from the amps. I use Altec's on my PP Mac MC40's and get zero listening fatigue. A lot of folks can't listen to horns on SS amps it seems. I've never tried it, sometime I will. I just know that a few watts can push them loud with no distortion and the dynamics are incredible. I've listened to some very expensive speakers and walked away very unimpressed.

BillWojo
Maybe horns are for the tube amps, it just doesn't sound right to me with SS amps. To me, Klipsch sounds down right bad, I have listened to the top of the line Klipsch, the big one that was over $3000 back in the days.

I don't see any newer Altec, the ones on ebay is really really old!!! Like from the 50s!!! Doesn't speaker gone through revolution since? It's hard to find horn tweeter and big woofer speakers now a days. Choice must be very limited.
 
AC heaters are usually not a problem with indirectly heated tubes unless we're talking phono stages. Most other things, honestly you'd never hear it unless there are problems with the wire routing.
 
AC heaters are usually not a problem with indirectly heated tubes unless we're talking phono stages. Most other things, honestly you'd never hear it unless there are problems with the wire routing.
I actually had problem with the hum from heater in my kit amp, I had to put two resistors on each wire to ground to lower the hum. I don't know how much it lower the hum as the hum is from crosstalk between the power transformer and the OPT.
 
I actually had problem with the hum from heater in my kit amp, I had to put two resistors on each wire to ground to lower the hum. I don't know how much it lower the hum as the hum is from crosstalk between the power transformer and the OPT.
Considering there have been non-humming amps with AC heaters produced for 75 years, it's possible you didn't consider every possibility before drawing conclusions.
 
Considering there have been non-humming amps with AC heaters produced for 75 years, it's possible you didn't consider every possibility before drawing conclusions.
It's all about how much gain you have. Power amp is easy, you only have gain of less than 20. If you have gain fo 1000 or more, this is everything. That's why people do it differently if it is phono stage. Particular in cascade gain guitar amps, it's a different world.
 
Does your kit amp have a gain of 1000 or more? Yes, DC heaters have been used in phono preamps for 75 years as well. The point is, if you had hum in your kit amp, it wasn't from the heaters.
 
It was from the heater, I fixed it. That's the whole point.

You might not have problem with power amp that is low gain. BUT the problem is there, you just ignore it. When I run the FFT, it sure shows and it's only about -60dB or so down. This is not comforting.

Yes, it's all relative, but it's there.
 
Alan, just because speakers and drivers are newer doesn't make them better. Do a search on Western Electric and the history of Altec. My current Altec system is from around 1972 and it is very dynamic and faithful in reproducing music. Yea, I know, there are new materials, computer modeling and on and on. I have yet to hear some small woofer that sounds like a 15" woofer. I've heard speakers like that in higher end units, I just shake my head. Today they make everything small and drive the hell out of them to try and get them to sound good. Why bother when the early engineers figured it all out years ago. The only problem with the older efficient speakers is that they take up a lot more room.
See if someone in your area has tubes on Altec's and check it out. There is a reason that Altec's are still very popular even though they went out of business several decades ago. GPA still sells new drivers and speakers same as what Altec made on the same tooling so if you have to have new, you can still buy it. Horns are readily available on Ebay for not much.
The Altec Users Forum has everything you ever wanted to know about Altec's.

BillWojo
 
I don't see there is a reason why using tubes for voltage regulator can be better than SS like MOSFET. Can you name some?

As @kward documented in his bench power supply thread, using tubes as the pass elements in the regulator had a couple of distinct advantages, namely:
  1. Inherent current-limiting capability because of how pentodes work.
  2. Much more resilient to short-circuit situations that were blowing MOSFETs in his first attempt.
Not necessarily applicable to the amplifier application, but still and answer to your question :)

That said, plenty of folks around these parts are using regulators for the screen supply of pentode output stages.
 
It was from the heater, I fixed it. That's the whole point.

You might not have problem with power amp that is low gain. BUT the problem is there, you just ignore it. When I run the FFT, it sure shows and it's only about -60dB or so down. This is not comforting.

Yes, it's all relative, but it's there.
Inaudible hum is not a problem, it's inaudible. If you had hum it wasn't because the heaters were AC, on a line-level amp there should be ZERO audible hum from AC heaters on indirectly-heated tubes. My speakers are 100dB sensitive. I built a 60-watt amp this summer (a fifty year-old design), with AC on all ten tubes in the amp, and on my 100dB speakers there was no audible difference between the amp being on and being off, with my ears one inch from the speaker drivers. Sensitivity was 1.5V for 60W output. How you manage to generate audible hum from AC heaters in your amp I don't know, but you seem to have figured out all the answers anyway.
 
As @kward documented in his bench power supply thread, using tubes as the pass elements in the regulator had a couple of distinct advantages, namely:
  1. Inherent current-limiting capability because of how pentodes work.
  2. Much more resilient to short-circuit situations that were blowing MOSFETs in his first attempt.
Not necessarily applicable to the amplifier application, but still and answer to your question :)

That said, plenty of folks around these parts are using regulators for the screen supply of pentode output stages.

I can easily design current limiting for that circuit and still is going to be a lot cheaper, a lot more reliable than the tube. It's all about the design, it's easy. The circuit I showed is the barebone working circuit. there are so many examples of current limiting design.

If you have a short, the tube is going to blow also. It's not as if the tube regulator is safe. It's going to be a lot more expensive to replace the tube.
 
I had to put two resistors on each wire to ground to lower the hum.

Proper design includes this. It balances the heater to ground and stabilizes the heater-cathode voltage. I have a preamp sitting in front of me with a small amount of hum, tacking in resistors stops it.
 
If you have a short, the tube is going to blow also
Not necessarily true. In fact, given as the pass device just a single power pentode vs. a single power mosfet, and with no additional aids in current limiting, it can be demonstrated that the tube will be able to easily handle a short circuit, whereas the mosfet can not. The key lies in the use of the pentode's screen.
 
Maybe horns are for the tube amps, it just doesn't sound right to me with SS amps. To me, Klipsch sounds down right bad, I have listened to the top of the line Klipsch, the big one that was over $3000 back in the days.

I don't see any newer Altec, the ones on ebay is really really old!!! Like from the 50s!!! Doesn't speaker gone through revolution since? It's hard to find horn tweeter and big woofer speakers now a days. Choice must be very limited.
Actually, in some ways Hi efficiency speakers are kind of the rage again. Yes, because of the popularity of single ended tube amps, which means low power, the pendulum has swung back the other way. I picked up a pair of Altec 19 about 2 years ago and it is so much better with low watt amps that i really don't think i will go back to panel speakers of 3 way boxes again.
Using a single driver tube and a single power tube makes everything more visceral in terms sound presentation. With so little circuitry and components in the signal path, very little signal is loss. The big drawback is the size of the speaker cabinet to load the bass driver. But in a small room a small fairly efficient speaker will work well.
 
Inaudible hum is not a problem, it's inaudible. If you had hum it wasn't because the heaters were AC, on a line-level amp there should be ZERO audible hum from AC heaters on indirectly-heated tubes. My speakers are 100dB sensitive. I built a 60-watt amp this summer (a fifty year-old design), with AC on all ten tubes in the amp, and on my 100dB speakers there was no audible difference between the amp being on and being off, with my ears one inch from the speaker drivers. Sensitivity was 1.5V for 60W output. How you manage to generate audible hum from AC heaters in your amp I don't know, but you seem to have figured out all the answers anyway.

All I can tell you is even I fixed the heater and reduce the 60Hz by half, the transformer coupling still cause an audible hum with my speaker. I can hear it within 8" from the speaker, so it's not exactly quiet.

I don't know how much the filament contributes after I fixed it as it's drown out by the transformer coupling.

I don't have all the answer, BUT I sure try as hell to figure things out and learn while I am on it. If people doesn't want to engage in the discussion, it's ok with me. I just throw it out so I can learn, AND also some other that is interested can join in and they can learn also. Doesn't people want to dig a little deeper instead of " I have been doing this for xxx many years and I don't have a problem, why are you bringing all this up"!!!!

This is a discussion forum, no one has all the answers, that's what we use this forum to share ideas.
 
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All I can tell you is even I fixed the heater and reduce the 60Hz by half, the transformer coupling still cause an audible hum with my speaker. I can hear it within 8" from the speaker, so it's not exactly quiet.

I don't know how much the filament contributes after I fixed it as it's drown out by the transformer coupling.

I don't have all the answer, BUT I sure try as hell to figure things out and learn while I am on it. If people doesn't want to engage in the discussion, it's ok with me. I just throw it out so I can learn, AND also some other that is interested can join in and they can learn also. Doesn't people want to dig a little deeper instead of " I have been doing this for xxx many years and I don't have a problem, why are you bringing all this up"!!!!
With all due respect, I dig the fact that you are trying to learn, and I am certainly not a guru, but you'd probably stand to benefit from paying attention to the people that *have* been doing this a little while. Not all of your statements reflect a willingness to learn, you've brushed aside a lot of comments from people with a lot of experience.

The problem with not knowing is that you don't know what it is that you don't know, and I don't mean that in any kind of derogatory sense. It's a bit early to be declaring that you've optimised something or determined something or eliminated variables or are sure of something.
 
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With all due respect, I dig the fact that you are trying to learn, and I am certainly not a guru, but you'd probably stand to benefit from paying attention to the people that *have* been doing this a little while. Not all of your statements reflect a willingness to learn, you've brushed aside a lot of comments from people with a lot of experience.

The problem with not knowing is that you don't know what it is that you don't know, and I don't mean that in any kind of derogatory sense. It's a bit early to be declaring that you've optimised something or determined something or eliminated variables or are sure of something.
Towards the later posts, mainly is on the regulated supply. I honestly cannot agree to stay with the tube rectifier. I posted the MOSFET alternative that is cheaper and will provide a stiffer rail that doesn't sag as much. It is not about learning, it's about discussion. It is not that I know it all, it's about talking out advantage and disadvantage. It is easy to do current limiting in the MOSFET circuit so you don't burn things. Even if you don't do current limiting, believe me, the MOSFET is so robust it will pull the power transformer down and blow the main fuse before anything will blow in case of a short.

Again, this is a discussion, people present their points why not using regulated supply, I present the counter point. It's is not I don't listen, I do have knowledge AND successfully designed and implemented into two guitar amps with this type of MOSFET circuit already. I don't see people actually stop and read my circuit and comment. Instead, accusing me of knowing it all. Particular for SE, this is a big advantage that the regulated circuit filter out the 60Hz and give you a quiet rail from the start. It is frustrating that if I have a different opinion and people say I don't listen and learn.
 
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Not to be blunt, you use tube rectifier, you lost about 25V of over head voltage, that is extra power wasted as heat. Then you have the filament of the rectifier tube that pull like 3A at 5V, that's another 15W wasted. You can save money on the rectifier tube and the power transformer without the wasted heat doing nothing using SS rectifiers. The money saved from the tube and smaller transformer let you pay for a little higher voltage filter caps to withstand the extra voltage before all the tubes turns on!!! SS rectifier is NO maintenance, not even "low" maintenance.

You want to have the softer rail of the tube, add a series resistor after the SS rectifier to soften the rail!!! This is electronics, not black magic!!!

Using MOSFET regulated supply, you get rid of the heavy and expensive choke, it's a lot cheaper, performs better and again NO maintenance. The circuit I show has soft start also in case people worry about to hard a start.

tell me what's wrong with all these?
 
Some people just like tube amps despite their known inefficiencies and flaws. If you can design a better tube amp, by all means have at it. But there are reasons things were and still are done a certain way with tube amps. Not all of those reasons are still valid with modern technology, but tube amp enthusiasts tend to be purists about it and enjoy using the same circuits from sixty years ago. I'm not saying it's a rational thing, but damn I like my old crappy, inefficient tube amps.
 
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