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Tube gear opinions

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SIY

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#81
I don't use tubes for the phono section because of the noise and characteristics that change with age, making accurate RIAA response difficult to maintain long term. Line stage is their best place to shine.
That is very much not the case with the phono stages I've designed and built. And not just mine, but those are the ones I have experience with.
 

H-713

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#82
The cheapest tubes in my SET amp are the 845 radio transmission tubes. They should obviously cost the most, but since they're radio transmission tubes...

I have been eyeing the Russian GM70 tubes for some real SET hifi.

I'm not aware of the 845 ever seeing very much use in radio transmitters- they were mostly used in really big audio amps from that era. If I remember right (and it's been a while since I studied the 845 datasheet), the 845 is extremely low mu and has internal capacitances that make it somewhat useless for transmitting. I know the 211 did see a reasonable amount of amateur service early on- my tube history is a little rusty, but I want to say this would have been the 1920s or 1930s.

Also, any competent engineer should know that you *never* want to depend on tube or transistor parameters for RIAA equalization. With tube gear, it will vary as tubes are inevitably replaced (though tube replacement is generally not a frequent thing), and with transistors it makes the device a royal PITA to manufacture.
 

Helicopter

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#83
I'm not aware of the 845 ever seeing very much use in radio transmitters- they were mostly used in really big audio amps from that era. If I remember right (and it's been a while since I studied the 845 datasheet), the 845 is extremely low mu and has internal capacitances that make it somewhat useless for transmitting. I know the 211 did see a reasonable amount of amateur service early on- my tube history is a little rusty, but I want to say this would have been the 1920s or 1930s.

Also, any competent engineer should know that you *never* want to depend on tube or transistor parameters for RIAA equalization. With tube gear, it will vary as tubes are inevitably replaced (though tube replacement is generally not a frequent thing), and with transistors it makes the device a royal PITA to manufacture.
I heard 845 is a transmission tube, but I can,'t vouch for that.

As for tube RIAA... interesting historical overlap in the tube to SS tech and the implementation, but I am not sure tubes cannot handle the deemphasis. I will not yet draw a conclusion on that.
 

MakeMineVinyl

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#84
I heard 845 is a transmission tube, but I can,'t vouch for that.
Out of curiosity I looked in my 1938 RCA Air Cooled Transmitting Tubes manual and the 845 is listed as an "A-F Amplifier, Modulator".

It says that you can go up to 1,250 VDC on the plate in amplifier service, so you can boost the voltage in your SET up to a respectable voltage. Only wimps go with only 1,000 VDC. :D
 

H-713

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#85
Out of curiosity I looked in my 1938 RCA Air Cooled Transmitting Tubes manual and the 845 is listed as an "A-F Amplifier, Modulator".

It says that you can go up to 1,250 VDC on the plate in amplifier service, so you can boost the voltage in your SET up to a respectable voltage. Only wimps go with only 1,000 VDC. :D
Like I thought- audio service. For those who aren't well-versed in the world of RF, the modulator in a big tube transmitter is essentially just a large tube audio amplifier.

It may be able to go up to 1200 V, but that doesn't mean that there is a performance incentive to doing so. It would certainly increase the cost.
 

mhardy6647

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#86
Then not necessarily having anything to do with High Fidelity, some people like all sort of distorted messes.
De gustibus non est disputandum.
I mean, I'm sure there's, e.g., a Borgward Owners' Club.
OK, I'm pretty sure.
I mean... it's not impossible, you know?

:cool:

1620352975734.png
 

MakeMineVinyl

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#87
It may be able to go up to 1200 V, but that doesn't mean that there is a performance incentive to doing so. It would certainly increase the cost.
That was my sad attempt at a joke. :confused:
 

Sal1950

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#88
But thoriated filaments are so pretty.

I keep the amp up high enough no one should fall on it, and I do not leave it on.
Pictures, or it never happened. :p
 

Helicopter

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#89
Pictures, or it never happened. :p
20210509_165816.jpg

Had to grab some speakers and hook it up. The 60Hz hum is gone now. :) I wonder where it was coming from before.

I hooked up some Panasonic RE-7070 speakers, and boy do they sound good. These are rated 16 ohm and go with my fairly big collection of consumer grade Panasonic stuff from before wood grain went out of style.

20210509_171722.jpg


Maybe I should try to clone them. The crossover is just a capacitor. I have a few pairs that are just a single 'full range' driver too. They all use RCAs as speaker cables, kind of a predecessor to Speakon in a way. I wonder why the backs are vented like this:

20210509_165953.jpg
 

MakeMineVinyl

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#90
View attachment 128882
Had to grab some speakers and hook it up. The 60Hz hum is gone now. :) I wonder where it was coming from before.

I hooked up some Panasonic RE-7070 speakers, and boy do they sound good. These are rated 16 ohm and go with my fairly big collection of consumer grade Panasonic stuff from before wood grain went out of style.

View attachment 128884

Maybe I should try to clone them. The crossover is just a capacitor. I have a few pairs that are just a single 'full range' driver too. They all use RCAs as speaker cables, kind of a predecessor to Speakon in a way. I wonder why the backs are vented like this:

View attachment 128883
That amp uses 300Bs as driver tubes? Definitely massive. :p
 

Helicopter

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#91
It looks way cooler now that the sun has set.
20210509_205318.jpg


I think it is 90 pounds. Interestingly it has a pair of OTs and then one power transformer for high voltage and another for mid voltage, even though it looks a little dual mono in configuration.

I really need to find some decent speakers that present an easy load for it and then get some of the mesh plate 300b tubes so the heater glow is brighter.
 

mhardy6647

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#92
The little Panasonics are, effectively, open baffles.
As a not entirely irrelevant aside -- I had a pair of Panasonic loudspeakers rather similar to those at one point. The pair that passed through here used Mitsubishi "fullrange" drivers with AlNiCo magnets... but, unfortunately, they didn't have that "Diatone P610" DNA! ;) I wasn't too favorably impressed, FWIW (and I have pretty catholic tastes when it comes to small/full-range/high-sensitivity loudspeakers). Glad you're liking yours!



Panasonicspeaker1.jpg

panasonicspeaker2.jpg

panasonicspeaker3.jpg
 

Helicopter

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I kinda figured the vented HDF made them effectively open. My full range (one way) Panasonics always sound bad, but I also use them in the basement and up here the room is excellent. I can certainly hear problems with these 2 way Panasonics, especially female vocals, and cymbals, but they are way better than the other 16 ohm rated speakers here.
 

Sal1950

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#94
It looks way cooler now that the sun has set.
Thanks, That's an incredibly handsome amp, specially for the money.
Mated to a pair of Klispch Heresy might be fun. :)
 

Helicopter

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#95
I've got an old pair of HBRs that work great with it, but I am a little sick of them right now. maybe I should try heresy IV or CW4.
 

Jim Matthews

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#96
How could anyone "hate" tube gear ? It's just so cool to look at in the dark sitting on the audio shrine..
Fine and dandy, if the AC is working.

No central air in my house, so 4 months out of each year required my "back up" amps. I deliberately chose the coldest room in my house for tubes.
 

mhardy6647

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#97
I kinda figured the vented HDF made them effectively open. My full range (one way) Panasonics always sound bad, but I also use them in the basement and up here the room is excellent. I can certainly hear problems with these 2 way Panasonics, especially female vocals, and cymbals, but they are way better than the other 16 ohm rated speakers here.
There've been a good many pretty decent sounding 16 ohm loudspeakers, though, you know? ;)
P1020753.jpg


edit:
PS. I thought I posted this last night, but apparently I failed. Here's my excuse for a failed "post" execution -- I was helpin' my son-in-law & his dad install a trailer hitch receiver on the latter's Tesla 3. This wasn't exactly hard, but it required removal of the bumper fascia and the actual bumper crash plate (which was subsequently replaced with the hitch/receiver structure). Made for a fun-filled mothers day afternoon for us... while the three wives/moms had a most pleasant one -- since we were out in the S-I-L's garage! ;)
 

DonH56

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#98
Side note to any tube amp newbies: Do NOT run a tube amplifier without a speaker (or some reasonable load) attached. The transformer coupling requires a load to keep the amp stable (i.e. to keep it from blowing up). Tripping over the speaker wires (e.g. at a party) and pulling them loose from the amp or speaker is a common tube amp failure mechanism.

FWIWFM - Don
 

Gorganzola

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It's a pity that I had to leave my tube amps in boxes when I moved here. They're fun and I miss playing with them. Soon again, perhaps.

I am under no illusion that there's any such thing as "tube sound," as regards the actual sound. It's a psychological/sociological artifact.
SIY, you have made the point a good many that there is no reason that tube sound should differ from S/S; further the you have designed but circuits, (though for what reason you'd have to explain), that sound different than S/S in no particular way.

I don't doubt what you say for a fleeting instant, however not every designer designs circuits with the maximum technical perfection, (say lowest THD+noise), as the goal. Many, probably most tube designers design for a "flawed" goal in mind -- that's also true of S/S designers, such as Nelson Pass. I'm not an engineer so I don't know, but I have conjectured a good many times myself that most tube circuits have high 2nd and/or 3rd order harmonic distortion and that the source of the so-called "warmth" mentioned by the OP (-- who has long since abandoned the thread, BTW). That might not be a "tube sound" but is one that was designed into the circuit.

Not all perceived sound differences are imaginary.
 

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