We are civilised folk here on Tubes-Valves; we try not to take things personally.
Still, your account of the 300b and Power DHTs in general requires numerous corrections.
300B, like the Marconi Osram PX25 is not embryonic. That adjective should be reserved for the DeForest Audion, or maybe the R-Type. Instead, the 1930s Power DHTs should be regarded as the high-water mark of Power Valve design. Both PX25 & 300B were expressly designed for good sound, and the transfer function shows it. What came after was designed for higher power, and lower cost. And smaller size. Miniaturisation does not improve the transfer function of a valve - it degrades it . I explained this in detail in a recent thread comparing Directly with Indirectly heated Power devices.
Have a look around at current production of power valves. If you do, you'll see that 300B, 2A3, 845 and many others of this type are supported by numerous new designs. After a shaky start in the 1990s, some of these are now reliable and good sounding.
Production of these, including the Western Electric 300B restarted just because the good sound was rediscovered by many designers, as well as listeners.
So don't worry about us competing with you for old stocks on these.
Hi mbrennwa,
They are grouped together as they were designed together. The circuits evolved to best use the device at that time. Tubes evolved to operate better under those conditions. I study the history of electronics and have several period, original books. Really cool stuff.
Hi Andy,
Those tubes were designed for economy and longevity, plus higher performance. One major difference over here is we went from a 4 watt heater to a 2 watt heater maintaining performance. Power tubes went from Triode to Tetrode for improved performance, Tetrode to Pentode to solve some problems. Then we went to Beam Power tubes for another increase in performance and efficiency.
I grew up with this stuff, was apprenticed on tube equipment. Later I serviced the modern interpretations and still do. I am exposed to the supposed best quite often, and I have a very good sound system on the bench I can audition this equipment on. I am pretty familiar with this design style in fact. It isn't my cup of tea. Measured performance is exactly what you would expect.
Again. If this is your preference, that is perfectly cool. I have no problem with it. But the fad has driven supply of tubes into the basement and new manufacture has become stupid expensive (because it's an audiophile fad). I've repaired this equipment now for over 5 decades including my pre being paid for fixing stuff time. I have watched parts prices and supply over that time period.
The basic design of these older tubes has been superseded. The basic engineering has moved forward. Yes, they may have improved these old types, but the basic design is still antiquated even if manufacturing has improved. Otherwise you would have a new tube, a modern one.
They are grouped together as they were designed together. The circuits evolved to best use the device at that time. Tubes evolved to operate better under those conditions. I study the history of electronics and have several period, original books. Really cool stuff.
Hi Andy,
Those tubes were designed for economy and longevity, plus higher performance. One major difference over here is we went from a 4 watt heater to a 2 watt heater maintaining performance. Power tubes went from Triode to Tetrode for improved performance, Tetrode to Pentode to solve some problems. Then we went to Beam Power tubes for another increase in performance and efficiency.
I grew up with this stuff, was apprenticed on tube equipment. Later I serviced the modern interpretations and still do. I am exposed to the supposed best quite often, and I have a very good sound system on the bench I can audition this equipment on. I am pretty familiar with this design style in fact. It isn't my cup of tea. Measured performance is exactly what you would expect.
Again. If this is your preference, that is perfectly cool. I have no problem with it. But the fad has driven supply of tubes into the basement and new manufacture has become stupid expensive (because it's an audiophile fad). I've repaired this equipment now for over 5 decades including my pre being paid for fixing stuff time. I have watched parts prices and supply over that time period.
The basic design of these older tubes has been superseded. The basic engineering has moved forward. Yes, they may have improved these old types, but the basic design is still antiquated even if manufacturing has improved. Otherwise you would have a new tube, a modern one.
Too bad you live in Canada, or I'd invite you to New Jersey, USA to hear what the old DHTs can do. The offer still stands if you're ever in the area...
Interestingly, although vinyl sounds very good through my homemade DHT pre and DHT amp, top-notch digital upsampled to DSD512 through my DHT-output DAC is mind-boggling. The clarity, detail and smoothness surprised even me!
To echo Andy, judicious use of modern SS tech (so-called "gyrator" loads, CCS, shunt regulators) helps to reveal the true capabilities of these old tubes, for sure!
BTW, I've recently gutted and remodeled my listening room/home theater, and this experience convinced me that the room itself is probably the biggest limitation of any system. Going from 8' to 11' ceilings, from asymmetrical to symmetrical, recessing the components into the wall, and designing with sound in mind makes a very big difference! New setup:
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Hi Andy. They are Infinity RSIIb, circa 1985. I completely rebuilt them, removing the crossover to external boxes, using much higher quality crossover components, bracing the cabinets, replacing the EMIM midrange diaphragms with the far superior replacements made by Apogee Acoustics in Australia, using Cardas copper litz for all wiring.
Here's a shot with the covers off, albeit in my old setup:
Here's a shot with the covers off, albeit in my old setup:
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I fully respect your deep knowledge of the history of tube equipment, and I do agree that in practical terms a small PP amp with EL34 outputs - like my stage amp for instance - would not have been possible in the old days. I have tried out a lot of old European radio tubes in modern SE designs, in fact, since I once had 100 of them. Some were very good sounding, like REN904, TDD4, ABC1 for instance, though I was glad to see top caps disappear from tube production. In the end I sold them all, mostly to the Far East. Only a small handful went to radio restorers - there was little interest there.
But I continue to use the 26 tube from the 1920s because it just sounds so marvellous - all the clarity and tonality I fail to get to the same degree with modern tubes. Of course it's obsolete - who would sell a tube with a gain of 8 and a 1.5V filament demanding 1 amp of current? Nuts. But it's a superb tube and fortunately plenty still about.
Anyway, back to mesh plates - I'd still be interested to know why the mesh plate 27 sounds so good. Another totally impractical tube, and much rarer these days. Interestingly the square mesh Philco type sounds better than the more common round mesh RCA type. I was lucky to buy a few from the USA so I have some stock. It sounds lovely.
Indirectly heated valves are more susceptible to high temperatures on the grid (smaller cathode, higher heating power density). Like for like, Mesh anodes cool better, and so they are far less likely to encourage grid emission.
Early IDHTs were held back by grid emission problems (see *), well known to the valve physicists, and using mesh anodes is a good solution to it.
* Keith Thrower: « History of The British Radio Valve to 1930. » London ISBN: 9780952068402
Early IDHTs were held back by grid emission problems (see *), well known to the valve physicists, and using mesh anodes is a good solution to it.
* Keith Thrower: « History of The British Radio Valve to 1930. » London ISBN: 9780952068402
HI....You grew up with the tubes...you did a lot of repairs. Did you build anything yourself?
Hi hooman,
I have built a TON of stuff, and still do. My first "stereo" was a single ended amp I pulled from a console driving a pair of 12" full range speakers, open back cabinets. Large cabinets.
I've built and repaired just about everything. Having formal and apprenticeship training, I have been forced to be very practical and factual. Like I've said, some stuff is fun. No problem.
I have built a TON of stuff, and still do. My first "stereo" was a single ended amp I pulled from a console driving a pair of 12" full range speakers, open back cabinets. Large cabinets.
I've built and repaired just about everything. Having formal and apprenticeship training, I have been forced to be very practical and factual. Like I've said, some stuff is fun. No problem.
Hi Andy,
I suspect the mesh plate tube differ in characteristics from the others. I've never examined each in detail.
One thing that is true, a circuit is normally designed to minimize distortion and create the desired gain. That occurs with a set of tube characteristics and deviation from that changes distortion and gain. I use number 27 tubes, they are popular in old radios. I also use '01 tubes and everything else. Each tube has a circuit where it is "happy". Why the mesh plate tube should sound better? Well if they were truly identical in characteristics to a solid plate, you couldn't hear or measure any difference between them. Tube elements (grids, plate, cathode / filament) all work on electric fields. A mesh is as effective as a solid plate in that regard.
I suspect the mesh plate tube differ in characteristics from the others. I've never examined each in detail.
One thing that is true, a circuit is normally designed to minimize distortion and create the desired gain. That occurs with a set of tube characteristics and deviation from that changes distortion and gain. I use number 27 tubes, they are popular in old radios. I also use '01 tubes and everything else. Each tube has a circuit where it is "happy". Why the mesh plate tube should sound better? Well if they were truly identical in characteristics to a solid plate, you couldn't hear or measure any difference between them. Tube elements (grids, plate, cathode / filament) all work on electric fields. A mesh is as effective as a solid plate in that regard.