Which are the interesting tubes available in mesh plate versions? I'd nominate the 27 and AZ1 or AZ11 as ones I've used and liked for instance.
Any explanation why mesh plates sound good?
Any explanation why mesh plates sound good?
I believe they (and several other small pentodes) have mesh screens outside of the electrode systems rather than mesh plates?
The "modern" mesh plates are in the majority perforated metal sheet. More metal, fewer holes.
The "old" style metal mesh is rare.
The "old" style metal mesh is rare.
There was this description of the operation of Secondary Emission Pentodes on the 'Wackiest Tubes' thread ... could it be that mesh anodes are less prone to secondary emissions?
Plate dissipation is lower.
Because the tube operates with electric fields, electrically there shouldn't be any difference. Electrode spacing and arrangement determines most characteristics. Cathode (or filament) coating supplies electrons and some are more efficient than others. Impurities generally create noise, as does how hard the vacuum is.
Earlier tube designs have very low mu. But tubes don't have a sound unless they are noisy or non-linear. The "sound" of a tube will be how it's characteristics interact with the circuit it is in. When you change between tube types, you are changing how the circuit operates. Blind "tube rolling" isn't intelligent. Too many factors are changing, you are not just hearing a tube.
Just like transistors, in a good design parts with similar characteristics sound the same. With tubes, similar parts have the same designation number as a rule. Different markets have their own numbering systems, but do make similar (not the exact same) tubes. If characteristics of a tube are upgraded in some way, not always suitable for audio, the type number may change, like numbered tubes in North America. You must look at heater current ratings for some "better" tubes, military or industrial numbers may have higher current requirements.
Because the tube operates with electric fields, electrically there shouldn't be any difference. Electrode spacing and arrangement determines most characteristics. Cathode (or filament) coating supplies electrons and some are more efficient than others. Impurities generally create noise, as does how hard the vacuum is.
Earlier tube designs have very low mu. But tubes don't have a sound unless they are noisy or non-linear. The "sound" of a tube will be how it's characteristics interact with the circuit it is in. When you change between tube types, you are changing how the circuit operates. Blind "tube rolling" isn't intelligent. Too many factors are changing, you are not just hearing a tube.
Just like transistors, in a good design parts with similar characteristics sound the same. With tubes, similar parts have the same designation number as a rule. Different markets have their own numbering systems, but do make similar (not the exact same) tubes. If characteristics of a tube are upgraded in some way, not always suitable for audio, the type number may change, like numbered tubes in North America. You must look at heater current ratings for some "better" tubes, military or industrial numbers may have higher current requirements.
Just gonna say any of these new perforated metal plate tubes are not mesh plate tubes. Call out the dealers to their face if you are at an audio show where the vendors show off their tubes with holes punched in the plates.
- In Triodes: True Mesh anodes are not so stiff as sheet metal; mechanical resonances will not be so sharp.
- The surface area of apertures is quite large, allowing radiation of heat away from the cathode/filament - and maybe more importantly the 1st. Grid.
Lower grid temperature reduces the risk of grid emission, and that is certainly an advantage for good sound. It's better to say: with solid sheet anodes, the hotter grids are more likely to overheat and sound bad.
The fact that Meshies have to run at lower power anyway will reinforce the lower temperatures, and mean the risk of grid emission is very low.
I was recently given Marconi U10 and U12 rectifiers. I did not know they were mesh anodes, until I saw these. They do look very fine.
Most heat is generated in the plate of power tubes. Signal tubes should never have a plate vibrating, and a mesh is merely lower mass, the force acts on the entire electric field so it would want to move the entire plate structure, mesh or sheet. Doesn't matter.
Maybe some radiant heat might escape from the space in the mesh. I don't think it would amount to a large difference. For G1, it is very close of the cathode so it is going to be hot. What you have to avoid is cathode material on the grid as that will emit electrons. That causes large problems, just noise if you're lucky. Operating the heater at full power without cathode current will encourage cathode material being deposited on the grid wire.
Maybe some radiant heat might escape from the space in the mesh. I don't think it would amount to a large difference. For G1, it is very close of the cathode so it is going to be hot. What you have to avoid is cathode material on the grid as that will emit electrons. That causes large problems, just noise if you're lucky. Operating the heater at full power without cathode current will encourage cathode material being deposited on the grid wire.
I use an EML mesh plate 274B rectifier in my 01A based DAC/preamp. Also tried a 5U4 and a few others - the EML had the sound most to my liking.
It would be better if they never did, but if you take a cheaper 300B variant, and run in in a room with music playing from another source, you can measure the noise generated by mechanical (microphonic) motion of the filament.
DHT power valves like the 300B are among the most likely to be found with mesh variants.
See the EMLs, for example, so this is relevant to the question.
DHTs are often built with copper grid supports and substantial radiators attached above, to minimise the grid temperature. Evidence enough that keeping the grid temperature low is no trivial concern.
Hi Rod,
Yes, you are talking about embryonic tube designs. They were improved greatly over time, as well as the circuits using them. I guess it's fun to play with single ended stuff using early tubes. I would never consider listening to this for music.
They used mesh plates into the 1960's with small base tubes. This is what I'm talking about, not the mechanical problems those very early tubes have.
I have a huge problem with people wasting no longer made tubes for new builds. I restore equipment that actually needs those tubes. The prices have been driven up and supply diminished by wasting what is a scarce resource. You can do so much better, I mean telephone companies figured this out in the 1920's and 1930's. Later designs really sound better and use technologically advanced tubes. Wasting a DHT old tube number to build something that doesn't perform well, or even as those circuits did back then doesn't makes sense - except that you can. I get they look cool, but each tube wasted in this manner relegates an old piece of equipment that could have worked to the scrap pile. An old, restored piece of history is worth so much more than a new oddity.
Oh well. "Just because you can, doesn't mean you should".
Yes, you are talking about embryonic tube designs. They were improved greatly over time, as well as the circuits using them. I guess it's fun to play with single ended stuff using early tubes. I would never consider listening to this for music.
They used mesh plates into the 1960's with small base tubes. This is what I'm talking about, not the mechanical problems those very early tubes have.
I have a huge problem with people wasting no longer made tubes for new builds. I restore equipment that actually needs those tubes. The prices have been driven up and supply diminished by wasting what is a scarce resource. You can do so much better, I mean telephone companies figured this out in the 1920's and 1930's. Later designs really sound better and use technologically advanced tubes. Wasting a DHT old tube number to build something that doesn't perform well, or even as those circuits did back then doesn't makes sense - except that you can. I get they look cool, but each tube wasted in this manner relegates an old piece of equipment that could have worked to the scrap pile. An old, restored piece of history is worth so much more than a new oddity.
Oh well. "Just because you can, doesn't mean you should".
So you have a problem with me since I designed and built a DHT tube amp using old 801A / VT25 tubes? I chose these tubes because they do exactly what I need in my amp. If you think there's something better from modern production, please let me know.
This looks like a "me too" thread...
Yes, I use 26 tubes in my daily amp and sometimes 27 mesh plate. I've also used 10Y, 46, 47, 01A, 6B4G and several other DHTs. Simply because they sound better than all the armada of post WW2 small 9 pin triodes that were designed for computers and feedback amps.
No way I'm going to compromise my precious amps for some hypothetical boffin repairing an old radio set somewhere on planet earth.
Yes, I use 26 tubes in my daily amp and sometimes 27 mesh plate. I've also used 10Y, 46, 47, 01A, 6B4G and several other DHTs. Simply because they sound better than all the armada of post WW2 small 9 pin triodes that were designed for computers and feedback amps.
No way I'm going to compromise my precious amps for some hypothetical boffin repairing an old radio set somewhere on planet earth.
I guess I am unpopular then. Really unpopular.
Yes, newer tube and circuit designs perform much better than any DHT or early heater type tube., I know, I was apprenticed on that stuff and restore very old electronics. Now if you prefer that particular distortion, I can't argue that. But the second you speak about performance, you're sunk.
Modern tubes are enhanced over old design (or they would still make old designs). The only single ended designs from the 1930's up to the 1970's existed in the least expensive radios, record players and ham/communications equipment where sound quality wasn't as important. I know, I own some of that stuff. But the higher quality and MUCH better sounding equipment was push-pull. That's floor standing radios and console stereos. For separates, all but the cheapest, nasty stuff was push-pull. Sorry man, that is reality.
Do I like some of those old radios? Sure I do, but high quality they aren't. Same for the single ended expensive stuff I get in for service today. Many of my clients use them for kicks, but their daily drivers are either push-pull or good solid state.
The fact remains. Using old tubes with no modern manufacture is irresponsible and questionable. Figure something else out, you can probably degenerate a modern tube to the same level of poor performance. If they made new 2A3 and 45 tubes (and similar), I could care less. Play away. But don't tell me they are superior, because they are not. If you're honest and simply say you like that sound, okay, No problem, but you are still wasting a resource. Some of that early stuff is engineered way beyond what I have seen in new designs. You'd be further ahead restoring and slightly improving those old good ones.
Preference is not superior performance. Not always.
Yes, newer tube and circuit designs perform much better than any DHT or early heater type tube., I know, I was apprenticed on that stuff and restore very old electronics. Now if you prefer that particular distortion, I can't argue that. But the second you speak about performance, you're sunk.
Modern tubes are enhanced over old design (or they would still make old designs). The only single ended designs from the 1930's up to the 1970's existed in the least expensive radios, record players and ham/communications equipment where sound quality wasn't as important. I know, I own some of that stuff. But the higher quality and MUCH better sounding equipment was push-pull. That's floor standing radios and console stereos. For separates, all but the cheapest, nasty stuff was push-pull. Sorry man, that is reality.
Do I like some of those old radios? Sure I do, but high quality they aren't. Same for the single ended expensive stuff I get in for service today. Many of my clients use them for kicks, but their daily drivers are either push-pull or good solid state.
The fact remains. Using old tubes with no modern manufacture is irresponsible and questionable. Figure something else out, you can probably degenerate a modern tube to the same level of poor performance. If they made new 2A3 and 45 tubes (and similar), I could care less. Play away. But don't tell me they are superior, because they are not. If you're honest and simply say you like that sound, okay, No problem, but you are still wasting a resource. Some of that early stuff is engineered way beyond what I have seen in new designs. You'd be further ahead restoring and slightly improving those old good ones.
Preference is not superior performance. Not always.
Awkward comparison: curcuits vs tube parts.
I still wonder which modern tube would perform as linear as an 801A or VT25, and could replace these. I'd be super happy if your claim were true and such a part would exist.
The armada of post WW2 small 9 pin tubes made for computers and feedback amps were cheap and mediocre. They had to be cheap because millions were used in computers. In push-pull feedback amps these mediocre tubes didn't matter so much, and the 12A*7 designs became popular not because they were superior but because they were widely used in guitar amps which kept production going. We still have mountains of post-Williamson P/P designs masquerading as top quality amps and using these guitar amp tubes. So much for imagination and creativity.
But you're wrong - they still make the best of the classic DHTs. New production 2a3, 300b, 845, 211 etc. and small tubes like 801A, probably the best driver tubes ever made, now produced by Elrog. There have been significant new design features for these DHT designs, like filament regs from Rod Coleman, filament bias and nice transformers from winders like Monolith, Ogonowski and Muse.
It's a shame that you had all this under your nose for so many years and didn't think to make a top quality DHT amp with them for your home listening enjoyment, using the innovations described above.