Hello,
from what I can read many SE Tube amps like high efficient speakers. My RH84 should theoretically never drive my 87db monitor speakers. 🙂
They do but but as I am hungry for new project I would like to try something more accurate for those speakers.
What tube or hybrid amp would you recommend for speakers with lower range of efficiency ? Are push-pull amps a way to go ? Or it is hybrid/ class D task?
Thank you for suggestions
from what I can read many SE Tube amps like high efficient speakers. My RH84 should theoretically never drive my 87db monitor speakers. 🙂
They do but but as I am hungry for new project I would like to try something more accurate for those speakers.
What tube or hybrid amp would you recommend for speakers with lower range of efficiency ? Are push-pull amps a way to go ? Or it is hybrid/ class D task?
Thank you for suggestions
Let's apply Paul Joppa's 102 dB. rule to those 87 dB. sensitive speakers. For a "typical" listening space, the speakers need upwards of 32 WPC. A respectable damping factor is (likely) a good idea too.
Darned tootin' push/pull is they way to go, less bankruptcy set in. IMO, using the Harman-Kardon Citation V (a superior Mullard style topology implementation), with 6L6GC O/P tubes, is a good place to start the project.
Darned tootin' push/pull is they way to go, less bankruptcy set in. IMO, using the Harman-Kardon Citation V (a superior Mullard style topology implementation), with 6L6GC O/P tubes, is a good place to start the project.
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I've only ever built one SE amp. It uses tubes for voltage and a MOSFET for current. It puts out 8 watts per channel, uses 400W from the wall, and runs at 95 degrees Celsius.
My push pull amps use all tubes, run at around 65 degrees, and put out between 15WPC and 110WPC.
Unlike Eli, I prefer Williamson topologies, and I rarely ever use anything but triode or triode-strapped output tubes.
FWIW, I have a pair of 83 dB speakers for nearfield - 8 watts SE is fine unless there is a lot of subsonic bass. 50W is loud. 80W will bottom them out.
This is an example of my Williamson-esque design using 6P 36S tubes for output. It will deliver ~50W of triode power. I have circuit boards for the VA/PI/Driver and boards for 6P 36S, 6P 45S, and 6P 31S (or 6BQ6, 6L6, EL34, KT***) are on the way.
My push pull amps use all tubes, run at around 65 degrees, and put out between 15WPC and 110WPC.
Unlike Eli, I prefer Williamson topologies, and I rarely ever use anything but triode or triode-strapped output tubes.
FWIW, I have a pair of 83 dB speakers for nearfield - 8 watts SE is fine unless there is a lot of subsonic bass. 50W is loud. 80W will bottom them out.
This is an example of my Williamson-esque design using 6P 36S tubes for output. It will deliver ~50W of triode power. I have circuit boards for the VA/PI/Driver and boards for 6P 36S, 6P 45S, and 6P 31S (or 6BQ6, 6L6, EL34, KT***) are on the way.
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Another option with similar output power:
EL34 Baby Huey Amplifier
Lauded design from a forum member. PCB's are sometimes available in group buy (you can join me in the waiting😉)
GB for Baby Huey PCB
I will build one for my acoustats.
EL34 Baby Huey Amplifier
Lauded design from a forum member. PCB's are sometimes available in group buy (you can join me in the waiting😉)
GB for Baby Huey PCB
I will build one for my acoustats.
Williamson style is fine, but it is very vulnerable to low frequency instability and costly, low phase shift, O/P "iron" seems "required". OTOH, Mullard style is somewhat forgiving of limited O/P "iron" quality and is comparatively "idiot resistant".
Careful execution of either Mullard or Williamson style topologies gets you excellent results. Both are "classic" for very good reasons.
A very good point. In my case the very good iron comes in the form of of the shelf power transformers 😀
Get a classic ! get a vta70 from tubes4hifi.com 2x35w clean power and
all tubes in current production, good documentation and spares available for teh coming 50 years
If you will design and build from scratch (even using a proven schematic, but where you have substituted different output transformers) . . .
In that case, I recommend you get some test equipment, including a signal source and an inexpensive digital scope (to be able to do things like see the wave shape of a sine wave on a tube stage that might be having a problem, a square wave ring, or square wave high frequency roll off, etc.).
And, you can use a square wave and scope to adjust the negative feedback compensation.
Purchase the scope first . . . . Even before you purchase a single part for your new amplifier.
With that scope . . .
Test your current amplifier and speakers:
Connect the 10X probe across your speaker terminals and see just how large (or just how small) the voltage peaks are.
That tells you something about the signal levels you are needing to get to a certain sound level in your room.
I can not understand how some persons with a scope have never done this.
And even the inexpensive digital scopes have a Persistence feature, that lets them easily show the voltage peaks over a long time (Put music on, adjust the volume, and then go get a cup of coffee, come back, and see All the peaks that happened while you were gone).
Inexpensive digital scopes also have an FFT feature. A free spectrum analyzer is included.
If you find an inexpensive digital scope, do not purchase it until you are sure the Persistance feature, and the FFT feature are included.
In that case, I recommend you get some test equipment, including a signal source and an inexpensive digital scope (to be able to do things like see the wave shape of a sine wave on a tube stage that might be having a problem, a square wave ring, or square wave high frequency roll off, etc.).
And, you can use a square wave and scope to adjust the negative feedback compensation.
Purchase the scope first . . . . Even before you purchase a single part for your new amplifier.
With that scope . . .
Test your current amplifier and speakers:
Connect the 10X probe across your speaker terminals and see just how large (or just how small) the voltage peaks are.
That tells you something about the signal levels you are needing to get to a certain sound level in your room.
I can not understand how some persons with a scope have never done this.
And even the inexpensive digital scopes have a Persistence feature, that lets them easily show the voltage peaks over a long time (Put music on, adjust the volume, and then go get a cup of coffee, come back, and see All the peaks that happened while you were gone).
Inexpensive digital scopes also have an FFT feature. A free spectrum analyzer is included.
If you find an inexpensive digital scope, do not purchase it until you are sure the Persistance feature, and the FFT feature are included.
If low output power then efficient speakers are desirable
But now your situation is exactly opposite because you already have low efficient speakers. Your speakers would receive more power from a class AB push-pull amplifier. Or, you could build an Ankoru style huge SE amplifier.
As Eli Duttman already said, you probably want a 32 W amplifier.
1 W → 87 dB
2 W → 90 dB
4 W → 93 dB
8 W → 96 dB
16 W → 99 dB
32 W → 102 dB
Single-ended class A amplifiers perform best at low signal levels, and they are usually also low-power amplifiers. So, an efficient speaker would be preferred.
But now your situation is exactly opposite because you already have low efficient speakers. Your speakers would receive more power from a class AB push-pull amplifier. Or, you could build an Ankoru style huge SE amplifier.
As Eli Duttman already said, you probably want a 32 W amplifier.
1 W → 87 dB
2 W → 90 dB
4 W → 93 dB
8 W → 96 dB
16 W → 99 dB
32 W → 102 dB
