OK, same intention, different question: whats better for a precious 300B: higher voltage, low current or lower voltage, higher current? Plate dissipation will be the same.
Depends of the OPT (recommended current) and the load of tube.
These parameters (and requiring power) strongly determines the suggested operating point.
These parameters (and requiring power) strongly determines the suggested operating point.
Thank you. Those answers are too general for my questions.
Question to Radio Yerevan: "Is it true that cosmonaut Yuri Gagarin won a red car at a charity event?"
Answer: “In principle yes, but it was not about the cosmonaut Yuri Gagarin, but the worker Alexander Putisch and he did not win a red car at a charity event, but his green bike was stolen from the parking space, but the rest is true . "😎
Question to Radio Yerevan: "Is it true that cosmonaut Yuri Gagarin won a red car at a charity event?"
Answer: “In principle yes, but it was not about the cosmonaut Yuri Gagarin, but the worker Alexander Putisch and he did not win a red car at a charity event, but his green bike was stolen from the parking space, but the rest is true . "😎
Figured out that Tango (ISO) X 2.7S is the best 300B output transformer.
Any more suggestions in the same class?
Any more suggestions in the same class?
Schmitz,
I hope we can steer you to a successful amplifier design.
And, I believe we can.
And, I believe you can build a pleasing amplifier for your system, using the Tango X 2.7S transformer.
At least it seems to be the same as the original Tango model:
FC-40-2.7S
40 W
(30Hz)
2.7K
4,6,8,16
15Hz-90KHz
100/300mA
300B
125x125x138
6,7Kg
You have asked a question about what plate voltage, what plate current, and what output transformer primary impedance.
Once you have picked an output transformer, we have a starting point.
But then best answer to the plate voltage and plate current requires more to be known about your Horn Loudspeakers.
You already do not have to worry about the 300B output power with 100dB speakers.
1. What is the range of impedance of your speakers versus frequency?
And,
2. How high of a damping factor does your woofer need to keep from "flopping in the breeze"? (An un-dampened woofer sounds awfully un-naturally booming).
If you have ever done load lines on a 300B curves from the data sheet, you can see the results of the 2nd harmonic distortion (look at the uneven spacing between the grid lines that the load line crosses).
And,
If you put the load line low on the curves, where the plate current lines are very curvy,
the plate resistance, rp, will not be 700 Ohms, it may be 1350 Ohms.
The difference in damping factor of those two on a 2700 Ohm primary would be:
2700/700 = 3.86 pretty good
2700/1350 = 2.0 pretty poor
Now, looking at the STC charts in the earlier posts (from the 1950s WE charts):
250V plate to filament
-48V grid to filament
60 mA plate current (0.060A)
2700 Ohms output transformer primary
4.1 Watts output
-30dBc 2nd Harmonic distortion
And,
250V x 0.60A = 15W plate dissipation (long long life), and not heating the whole area around it.
300B max quiescent current, 100mA; max plate to filament voltage 400V or 450V.
Purchase an inexpensive 300B for initial amplifier power-up and check out.
Purchase a mid priced 300B for listening.
And, it is not hard to get a single stage driver that can drive the 300B grid + 48V and - 48V (96V peak to peak).
Especially if you are using a CD player that puts out 2.1Vrms (3V peak, 6V peak to peak).
If the music CD puts out full scale, that is one thing.
If the music CD peaks only put out -6dB, less than full scale peaks, then the driver gain needs to be 32.
But if you only need 2.05 watts out for your speakers, and the CD max is at - 6dB, the driver gain needs to be 22.6.
If I had that transformer and was going to build a 300B amplifier, for 100dB speakers, I would build that one.
Now you will get many more who will want you to do it another way, that is OK too.
Pick one design.
I can hardly wait to hear how it sounds and works for you.
I hope we can steer you to a successful amplifier design.
And, I believe we can.
And, I believe you can build a pleasing amplifier for your system, using the Tango X 2.7S transformer.
At least it seems to be the same as the original Tango model:
FC-40-2.7S
40 W
(30Hz)
2.7K
4,6,8,16
15Hz-90KHz
100/300mA
300B
125x125x138
6,7Kg
You have asked a question about what plate voltage, what plate current, and what output transformer primary impedance.
Once you have picked an output transformer, we have a starting point.
But then best answer to the plate voltage and plate current requires more to be known about your Horn Loudspeakers.
You already do not have to worry about the 300B output power with 100dB speakers.
1. What is the range of impedance of your speakers versus frequency?
And,
2. How high of a damping factor does your woofer need to keep from "flopping in the breeze"? (An un-dampened woofer sounds awfully un-naturally booming).
If you have ever done load lines on a 300B curves from the data sheet, you can see the results of the 2nd harmonic distortion (look at the uneven spacing between the grid lines that the load line crosses).
And,
If you put the load line low on the curves, where the plate current lines are very curvy,
the plate resistance, rp, will not be 700 Ohms, it may be 1350 Ohms.
The difference in damping factor of those two on a 2700 Ohm primary would be:
2700/700 = 3.86 pretty good
2700/1350 = 2.0 pretty poor
Now, looking at the STC charts in the earlier posts (from the 1950s WE charts):
250V plate to filament
-48V grid to filament
60 mA plate current (0.060A)
2700 Ohms output transformer primary
4.1 Watts output
-30dBc 2nd Harmonic distortion
And,
250V x 0.60A = 15W plate dissipation (long long life), and not heating the whole area around it.
300B max quiescent current, 100mA; max plate to filament voltage 400V or 450V.
Purchase an inexpensive 300B for initial amplifier power-up and check out.
Purchase a mid priced 300B for listening.
And, it is not hard to get a single stage driver that can drive the 300B grid + 48V and - 48V (96V peak to peak).
Especially if you are using a CD player that puts out 2.1Vrms (3V peak, 6V peak to peak).
If the music CD puts out full scale, that is one thing.
If the music CD peaks only put out -6dB, less than full scale peaks, then the driver gain needs to be 32.
But if you only need 2.05 watts out for your speakers, and the CD max is at - 6dB, the driver gain needs to be 22.6.
If I had that transformer and was going to build a 300B amplifier, for 100dB speakers, I would build that one.
Now you will get many more who will want you to do it another way, that is OK too.
Pick one design.
I can hardly wait to hear how it sounds and works for you.
Last edited:
6A3sUMMER,
many thanks for giving so much fabulous hints on this amp.
As I've had this amp in my head for a very long time, some design center specs should be:
-8W output power (means with this 2.7K transformer approx. 330V plate voltage @60mA)
I don't want to go below that output power because my plans are for a new home with more space for speakers and listening room.
With my horn speaker, the woofers are interchangeable. It is a front and backloaded cabinet, in fact it is a bass horn Version of the Shindo Latour. Same outer dimensions, different woofers.
Here are the TSP Parameters of the Woofers:
TSP...............Nr1.......Nr2
Fs...............59.5......61.0
Rо...............6.2........6.4
Qms............15.91.....16.24
Qts.............0.506.....0.643
Qes.............0.523.....0.669
Vas.............100........97
SPL.............97.5.......96.7
Woofers may may not reach exactly 100dB, but those measures are not from my own woofers but have been found on the internet. So mine could be a little higher in efficiency, up to 99dB max. They are 8 Ohm woofers, combined with a 16 Ohm Altec 288C horn driver, coupled with autotransformer. Very dynamic system.
Unfortunately, it's not in my knowledge to calculate the damping factor of that system.
I will start with a mid priced 300B and later change for a real WE tube. That sound is what interests me and is a serious distinguishment to my pentode amp I think.
many thanks for giving so much fabulous hints on this amp.
As I've had this amp in my head for a very long time, some design center specs should be:
-8W output power (means with this 2.7K transformer approx. 330V plate voltage @60mA)
I don't want to go below that output power because my plans are for a new home with more space for speakers and listening room.
With my horn speaker, the woofers are interchangeable. It is a front and backloaded cabinet, in fact it is a bass horn Version of the Shindo Latour. Same outer dimensions, different woofers.
Here are the TSP Parameters of the Woofers:
TSP...............Nr1.......Nr2
Fs...............59.5......61.0
Rо...............6.2........6.4
Qms............15.91.....16.24
Qts.............0.506.....0.643
Qes.............0.523.....0.669
Vas.............100........97
SPL.............97.5.......96.7
Woofers may may not reach exactly 100dB, but those measures are not from my own woofers but have been found on the internet. So mine could be a little higher in efficiency, up to 99dB max. They are 8 Ohm woofers, combined with a 16 Ohm Altec 288C horn driver, coupled with autotransformer. Very dynamic system.
Unfortunately, it's not in my knowledge to calculate the damping factor of that system.
I will start with a mid priced 300B and later change for a real WE tube. That sound is what interests me and is a serious distinguishment to my pentode amp I think.
Last edited:
You might be able to get 8 Watts at -26dBc 2nd harmonic distortion (5%)
at 330Vp-f, 60mA, and 2700 Ohm primary. But probably more like 4 or 4.5 Watts at low distortion.
That is about 26% plate dissipation to output power efficiency, reasonable for SE triode.
The damping factor of an amplifier is defined in terms of its output taps rating/its actual output impedance.
8 Ohm Tap/2.67 Ohms output impedance = damping factor of 3.
I do not know the minimum damping factor your speaker requires.
If you have a solid state amplifier, try putting a 2.5 Ohm resistor in series between the amplifier's hot output tap and the loudspeaker's hot lead.
Connect the amp common to the loudspeaker common.
That may give you a rough idea of what a damping factor of 3 on the 8 Ohm tap of the 300B amp will give you.
at 330Vp-f, 60mA, and 2700 Ohm primary. But probably more like 4 or 4.5 Watts at low distortion.
That is about 26% plate dissipation to output power efficiency, reasonable for SE triode.
The damping factor of an amplifier is defined in terms of its output taps rating/its actual output impedance.
8 Ohm Tap/2.67 Ohms output impedance = damping factor of 3.
I do not know the minimum damping factor your speaker requires.
If you have a solid state amplifier, try putting a 2.5 Ohm resistor in series between the amplifier's hot output tap and the loudspeaker's hot lead.
Connect the amp common to the loudspeaker common.
That may give you a rough idea of what a damping factor of 3 on the 8 Ohm tap of the 300B amp will give you.
Last edited:
Thanks a lot. I will inquire for this output transformers and start collecting the necessary parts.
Do not forget to do the cheap test for your loudspeakers.
It will give you the knowledgeable and proven knowledge that you should continue the plan to use a 2700 Ohm primary.
A simple 2.5 Ohm 5 Watt resistor, and almost any solid state amplifier
will allow you to hear what your speakers sound like when driven from an amplifier that has a damping factor of 3.0.
It will affect the time of the woofer to follow a transient bass music event that is followed by a fast collapse of the sound.
Examples, a stand up bass that is plucked, followed by a hand slap to the vibrating spring,
or a bass drum that is struck, and then the soft hammer touches the drum head, dampening the resonance.
You can think of your own examples.
Damping factor will also affect the effective frequency response of your horn loudspeaker, from lowest bass to highest tweet.
I bet it will all sound good in terms of damping and frequency response, but of course the other characteristics and timbre of the sound will be completely different with the 300B amp versus with the 2.5 Ohm resistor in series with the solid state amp.
I do not know how expensive they are in your country, but Monolith Magnetics builds real premium performance output transformers (known to many in our vacuum tube club here). $$$ (sorry Euros).
It will give you the knowledgeable and proven knowledge that you should continue the plan to use a 2700 Ohm primary.
A simple 2.5 Ohm 5 Watt resistor, and almost any solid state amplifier
will allow you to hear what your speakers sound like when driven from an amplifier that has a damping factor of 3.0.
It will affect the time of the woofer to follow a transient bass music event that is followed by a fast collapse of the sound.
Examples, a stand up bass that is plucked, followed by a hand slap to the vibrating spring,
or a bass drum that is struck, and then the soft hammer touches the drum head, dampening the resonance.
You can think of your own examples.
Damping factor will also affect the effective frequency response of your horn loudspeaker, from lowest bass to highest tweet.
I bet it will all sound good in terms of damping and frequency response, but of course the other characteristics and timbre of the sound will be completely different with the 300B amp versus with the 2.5 Ohm resistor in series with the solid state amp.
I do not know how expensive they are in your country, but Monolith Magnetics builds real premium performance output transformers (known to many in our vacuum tube club here). $$$ (sorry Euros).
Last edited:
Thank you, 6A3sUMMER.
Never done this "cheap test" before but it could be done, of course.
Never heard any products from this relative new company Monolith Magnetics but as this is a cost no object project I won't cut on output transformer performance. Thats why it should be a DIY project. Actually I hear with Tamura permalloy and its an obsession to hear music with that. Not less is possible for me, I would have trusted Tribute from Netherlands, too. But not any new company on the market which hasn't a reputation for building the best possible. Life is too short for doing such a project and go for second best and unfortunately I can't go for transformers just to try out (or do a "shoot out"). The choice must be first class, reputable, with a legendary sound. The best or nothing.
Never done this "cheap test" before but it could be done, of course.
Never heard any products from this relative new company Monolith Magnetics but as this is a cost no object project I won't cut on output transformer performance. Thats why it should be a DIY project. Actually I hear with Tamura permalloy and its an obsession to hear music with that. Not less is possible for me, I would have trusted Tribute from Netherlands, too. But not any new company on the market which hasn't a reputation for building the best possible. Life is too short for doing such a project and go for second best and unfortunately I can't go for transformers just to try out (or do a "shoot out"). The choice must be first class, reputable, with a legendary sound. The best or nothing.