The wattage output does NOT matter. Watts can be very high or extremely low (watts do NOT matter for this amp)
Do you know where I can find a schematic that closely meets ALL of the following objectives:
So the complexity of the schematics is not the concern. I just need to stay withing the above requirements.
Thank you so much for pointing me to any schematics that meet all the above.
I'm Eddie and I've been an audiophile since 1985 and a member of the Suncoast Audiophile Society in Tampa Florida.
My main system is a pair of Martin Logan Monolith III and Dynaco ST-120 amp, Oppo preamp/receiver. MIT wires.
Do you know where I can find a schematic that closely meets ALL of the following objectives:
- Only two (2) vacuum tubes in the entire amp
- Both tubes are 300B
- Only three (3) transformers in the entire amp
- One is the power transformer
- Two are the output transformers (L & R)
- Wattage output doesn't matter
- Very low number of electrical components (i.e., capacitors, resistors, diodes, chokes, etc)
- Minimalist approach is most desired
- highest possible sound quality given the above constraints
So the complexity of the schematics is not the concern. I just need to stay withing the above requirements.
Thank you so much for pointing me to any schematics that meet all the above.
I'm Eddie and I've been an audiophile since 1985 and a member of the Suncoast Audiophile Society in Tampa Florida.
My main system is a pair of Martin Logan Monolith III and Dynaco ST-120 amp, Oppo preamp/receiver. MIT wires.
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If that's all you need/want, why bother with an expensive 300b. Also, I've never seen/heard of anyone using this tube on it's own. They only have a gain of 4x.
jeff
If a different topology or tube choice is acceptable, you could also build a one stage EL84 amp. Probably much cheaper.
Your self imposed requirements are going to result in a much poorer quality amplifier than if you'd have spent the same money on a better design.
Why a 300b?
Why half a watt?
Why limit yourself to only one tube and why further limit yourself to one with only one section?
You're going to spend a fair ammount of money and time building something thats not particularly useful for anything in order to satisfy some design goals which are detatched from reality.
If you insist on doing it anyway, go ahead.
Youll need to provide some ac for the filament. Tie it to ground with a center tap through a resistor. (Check data sheet for value.)
Transformer primary to plate
Signal fed to grid.
Grid tied to ground through a resistor (check data sheet)
No more transformers so youll need a crcrc supply which again is easy to cobble together without a schematic.
Curious what you're driving at the half watt level that sounds so satisfying that you're ready to swear off anything above a watt?
Is the music you're hearing causing you to feel this way or is it the audiophiles wagging their jaws again?
Is there any reason that you couldn't build a 7w 300b set and refrain from driving it past .5w? You'd still be bandwidth limited but theres at least a chance of driving a few of the most efficient speakers if you limit your musical choices to anything without bass...
Why a 300b?
Why half a watt?
Why limit yourself to only one tube and why further limit yourself to one with only one section?
You're going to spend a fair ammount of money and time building something thats not particularly useful for anything in order to satisfy some design goals which are detatched from reality.
If you insist on doing it anyway, go ahead.
Youll need to provide some ac for the filament. Tie it to ground with a center tap through a resistor. (Check data sheet for value.)
Transformer primary to plate
Signal fed to grid.
Grid tied to ground through a resistor (check data sheet)
No more transformers so youll need a crcrc supply which again is easy to cobble together without a schematic.
Curious what you're driving at the half watt level that sounds so satisfying that you're ready to swear off anything above a watt?
Is the music you're hearing causing you to feel this way or is it the audiophiles wagging their jaws again?
Is there any reason that you couldn't build a 7w 300b set and refrain from driving it past .5w? You'd still be bandwidth limited but theres at least a chance of driving a few of the most efficient speakers if you limit your musical choices to anything without bass...
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Good point. I edited the original point to clarify that the wattage output doesn't matter. Therefore, a 7 watt or even a 70 watt 300B set would be great if I could just find a minimalist schematic.
I was so very hopeful to focus this topic on finding a well known schematic that is as minimalist as possible (i.e., the least number of electrical components while using a schematic that has been built by others in the past).
English is not my 1st language so I sometimes run into this problem of not choosing the right wording for my questions/comments... it's like a curse and a struggle that I'm frequently misunderstood.
So all the responses above helped me to edit my original post.
I can't thank you enough @Midnightmayhem and everyone that responded so far
In that case i'd suggest picking your flavor of SET 300b and building one.
It will have a driver tube but a driver of some sort is required to get the 300b to play music.
Ill leave further commentary to the SET people. Im a builder of push pull amplifiers...
It will have a driver tube but a driver of some sort is required to get the 300b to play music.
Ill leave further commentary to the SET people. Im a builder of push pull amplifiers...
I could not resist the temptation to show here a most simple push-pull EL84 amp (not showing power supply)...
About 0,7W with 1V input. With 8V imput it would be more of course. And no phase splitter neccesary. One stage pp amp.
Again, why?
You're using like 5% of the capacity of the transformer and tubes...
You could probably make a decent 15w amp out of that but once again it needs more than one stage to be useful.
You're using like 5% of the capacity of the transformer and tubes...
You could probably make a decent 15w amp out of that but once again it needs more than one stage to be useful.
If I would need the remaining 95% I'd use a powerful preamp, maybe I will some time, no problem there. Like the OP, I do not need much power and just like it this way, there is no rationality but it sounds d@mn good to me without the drivertube or phase splitter and only one capacitor and one resistor in the signal path -ultimate purity. Single ended could be possible, but then you really have no power so pp is a good compromise. The 0,7W output gives me >100dB sound pressure @ LP from the horn it is connected to, that is enough. I like the EL84 too. I hope OP will not give up his dream only because from an engineering pov it is futile to build something like what he had in mind.
I know it doesn’t necessarily need to be a typical tube based inversion scheme but, by definition, doesn’t push pull require some form of phase inversion?
Could also be accomplished with an input transformer or with balanced outputs from a preamp or DAC but don’t the signals sent to each tube need to be inverted phase?
It seems like what’s pictured would be some sort of parallel single ended but with each tube loaded by half the primary of a PP OT which, presumably, doesn’t have an air gap like a typical SE OT.
Wouldn't that require an XLR input? The amp shown has a normal RCA jack.
Such a design would yield 24mw into 8 ohms using 2.5K transformers.
If you had REALLLLLLLLY efficient speakers (say 102db), you might get ~85db out of them.
Could also be ok at being an amplifier for IEMs or really efficient headphones.
If you had REALLLLLLLLY efficient speakers (say 102db), you might get ~85db out of them.
Could also be ok at being an amplifier for IEMs or really efficient headphones.
Seems like a waste of a perfectly good 15 watt ultralinear transformer and 2 perfectly good tubes and tube sockets.
Add a 12ax7 to the mix as a voltage amp and splitter and you could easily have those 15 watts too!
Put a few DB global feedback around the whole thing and you'd have a perfectly usefull amp, capable of driving a variety of speakers and enough power that you'll feel the bass...
Add a 12ax7 to the mix as a voltage amp and splitter and you could easily have those 15 watts too!
Put a few DB global feedback around the whole thing and you'd have a perfectly usefull amp, capable of driving a variety of speakers and enough power that you'll feel the bass...
I hear you, but I won't repeat my previous reply to you if you don't mind. I have a tube pre-amp that puts out 30V at a load of 10kOhm so I can hook that up any time I need more power. This particular amp has a twin, it powers the tweeter of a coaxial compression driver, the above one powers the midrange. Sensitivity of the CD is >110dB so even if the amps may put out 15W, I will never use it, but the noise and distortion level will rise.
By the way, would you say the same to those people who build >100W ss amps that will be used with only 10 W max in an average home? That it is a waste of a perfectly good big power transformer, big elco's and power transistors? I guess not.
If you mean using the 300B in a spud design, I think it is not really useful indeed.
If you want to use 300B in SPUD, for 0.5W output requires at least 40Vpp grid swing, so another gain stage (tube or appropriate SUT) is requiring.
A hundred watt amplifier used at 10% capacity is at least useful.
Its useful anywhere on earth and to a variety of users.
Half a watt of power from a non inverting power stage is only useful when you engineer a situation where its useful.
Not useful anywhere outside your carefully engineered situation...
I tend not to comment on solid state stuff and i rarely comment on single ended tube stuff because these are not my lanes. You brought a pseudo push pull into the mix and that can't work either, besides perhaps as a pleasant distortion generator in a carefully engineered system.
I can't honestly recommend anyone trod that path, but if you've got money burning a hole in your pocket, i cant exactly stop ya.