Please can anyone offer advice on the electrical parameters that are important for a speaker cable driving the capacitance load of an ESL from a direct drive amp?
Direct drive tube ESL amps can allegedly swing 4kV at 0.3A directly off the plates. Speaker cables could be up to 5m long.
Clearly this is a totally different load to the usual generic speaker amp driving an ESL transformer at the speaker. Obviously safety is paramount but that's about all I know 😱
What capacitance and inductance specifications will ideally match the ESL load? What is needed to look after a tube direct drive amp driving direct off the plates?
Could a coaxial cable work
eg Flexible RG_213_/U
Nom Impedance ~ 50 Ω
Nom. Inductance ~ 0.23 μH/m
Nom Capacitance ~100 pF/m
Nom operating voltage ~ 3 to 5 kVrms
Nom AWG ~13
Nom Power >1kW
Direct drive tube ESL amps can allegedly swing 4kV at 0.3A directly off the plates. Speaker cables could be up to 5m long.
Clearly this is a totally different load to the usual generic speaker amp driving an ESL transformer at the speaker. Obviously safety is paramount but that's about all I know 😱
What capacitance and inductance specifications will ideally match the ESL load? What is needed to look after a tube direct drive amp driving direct off the plates?
Could a coaxial cable work
eg Flexible RG_213_/U
Nom Impedance ~ 50 Ω
Nom. Inductance ~ 0.23 μH/m
Nom Capacitance ~100 pF/m
Nom operating voltage ~ 3 to 5 kVrms
Nom AWG ~13
Nom Power >1kW
Last edited:
It's still a matter of total capacitance tied to the output of the amplifier, So the Pf/foot of the cable adds up as the cable gets longer, assuming that the shield is grounded. 😉
See this page,
Coax Intro).
As Quoted from the above page,
"The inductance of the coax (for audio applications) is almost never a problem. However, the capacitance is often right in the range where opamps (and even emitter followers) are subject to the greatest potential for oscillation. Few active circuits like capacitive loads, and the most critical range is from around 500pF up to 10nF or so. This is exactly the range of capacitance that common shielded cables and/or 'true' coax will present to the driving circuit."
jer 🙂
See this page,
Coax Intro).
As Quoted from the above page,
"The inductance of the coax (for audio applications) is almost never a problem. However, the capacitance is often right in the range where opamps (and even emitter followers) are subject to the greatest potential for oscillation. Few active circuits like capacitive loads, and the most critical range is from around 500pF up to 10nF or so. This is exactly the range of capacitance that common shielded cables and/or 'true' coax will present to the driving circuit."
jer 🙂
Last edited:
I have a direct drive amp and spoke to Roger Modjeski about this.
That's his amp build in the pic...is it yours?
Roger recommended slicone test prod wire. less than 5-6' long. Here is a quote from him in an email to me:
"I found some nice high voltage silicone wire at a surplus place. Its lays well and the insulation is superb. Any wire will do of course. PVC has a little leakage you can feel when touched. Teflon is the next best over silicone but doesnt lay as well. The gauge is not important 22 is big enough."
The idea is to have the DD amp see as little capacitance as possible added from the wires... the load of the panels is almost purely capacitive and the tubes used are high current - the more capacitance the more current they will draw. Also it is interesting to note that if you are playing high energy music like trumpet ,for example, this will draw more current and limit the life of the output tubes.
Having said all that I have a pretty long run of silicone wires for the panels to my DD .. I don't notice any impact on high frequencies nor dynamics I run about 10' or so ... although I should make shorter... because I can.
That's his amp build in the pic...is it yours?
Roger recommended slicone test prod wire. less than 5-6' long. Here is a quote from him in an email to me:
"I found some nice high voltage silicone wire at a surplus place. Its lays well and the insulation is superb. Any wire will do of course. PVC has a little leakage you can feel when touched. Teflon is the next best over silicone but doesnt lay as well. The gauge is not important 22 is big enough."
The idea is to have the DD amp see as little capacitance as possible added from the wires... the load of the panels is almost purely capacitive and the tubes used are high current - the more capacitance the more current they will draw. Also it is interesting to note that if you are playing high energy music like trumpet ,for example, this will draw more current and limit the life of the output tubes.
Having said all that I have a pretty long run of silicone wires for the panels to my DD .. I don't notice any impact on high frequencies nor dynamics I run about 10' or so ... although I should make shorter... because I can.
This thread is actually quite repetitive to the discussion already started here 😉 ,
what type of speaker cable/ connecter do your use with your electrostatics?
FWIW
jer 🙂
what type of speaker cable/ connecter do your use with your electrostatics?
FWIW
jer 🙂
Thanks very much for the great info. That amp photo is just the stock photo from the sales website. I'm not jumping with the price at $6500. But I'm intrigued by the idea of direct drive ESL's. Are they worth it?
In what way does that thread address direct drive amp speaker cables needing to carry very high voltage low current transmission straight to the ESL stators over metres?
In my opinion they are like the F1 of electrostatics. The compromises of transformers are many, especially for electrostatic step up. The only advantages are costs and simplicity... that is enough for commercial products.
For DD, the advantage of directly feeding the stators is obvious in the sense of dyanmics. Downsides are, costs, heat , space and potentially safety if you have pets etc.
Because when you talk about running long cables to the ESL from the Step-up interface transformer or DDamp it is the same concept and the same rules apply. 😉
Although the op in that thread did not state on which side of the interface he was referring too, I should have questioned it then as well.
Not everyone has their interfaces close to the drivers (as I don't either), as they can be quite heavy and difficult to move the driver panel around easily, thus the need for longer wires to feed them with.
jer 🙂
Although the op in that thread did not state on which side of the interface he was referring too, I should have questioned it then as well.
Not everyone has their interfaces close to the drivers (as I don't either), as they can be quite heavy and difficult to move the driver panel around easily, thus the need for longer wires to feed them with.
jer 🙂
The current in to the electrostatics is mA
The capacitance is approx 1nF
So the wire can be made very thin.
I do not believe in coax unless you run double coax in parallel and let the inner conducturs go in balanced mode keeping the screens grounded.
A twinaxcable would be better and I would run an extra shield around it to be on teh safe side. The voltage is lethal!
The capacitance is approx 1nF
So the wire can be made very thin.
I do not believe in coax unless you run double coax in parallel and let the inner conducturs go in balanced mode keeping the screens grounded.
A twinaxcable would be better and I would run an extra shield around it to be on teh safe side. The voltage is lethal!
I ran a direct drive 2400 VDC at lethal currents for some decades. Very dangerous and maybe you should re-think your interest in it, esp if you have a family or cat, have two arms, or don't have rubber boots. Definitely don't proceed if any thing in the previous sentence mystifies you.
Several previous threads. Possibly search for "Sanders". The results are outstanding but few do it. Pity.
Yes, hard to beat test probe wire, exactly right for this use. No usual cable parameters matter, if you simply do the math.
Several previous threads. Possibly search for "Sanders". The results are outstanding but few do it. Pity.
Yes, hard to beat test probe wire, exactly right for this use. No usual cable parameters matter, if you simply do the math.
Comparatively, dd is in a different league altogether ime. I have doubled the dd amps on my Acoustat Monitor 3 as well as panels with spectacular results. They actually don't make a lot of heat. What they do make is fabulous sound. Well worth the effort.