Hi All
I've been reading for a while, but as I didn't manage to spot a thread that helped with the question I'm trying to answer, I guess it's time for my first post.
Bit of background first so you can see where I'm coming from, please bear with me for a moment....
I have a small (2' x 1' x 9") pair of Dynastatic speakers, designed in the UK by an ex-BBC engineer, Alex Shackman, in the '70s, that have 6" cone bass drivers and his 8"x6" electrostatic HF panels. Initially I ran them passive as designed, and they do sound really gorgeous compared to my old setup, but then, because the HF panels are known to be hard to drive, I decided to play about with an active configuration. This works much better and sounds really nice to my ears.
But I do still detect the NAD 3150 power amps that drive the HF units can struggle sometimes; I believe the panels dip below 1ohm at high frequencies. Typically I believe they were normally recommended to be driven by Quad II valve amps, and I could go down the valve route, but then I started thinking about building a pair of amps and was looking at the A40.
Unfortunately there is little in the way of specs available for the Shackman panels, apart from they run at a comparatively low HT voltage of around 400v and have a *very* small stator gap - they use a cotton-like thread to space the membrane from the stators, and were designed in the era of low powered amps.
What I do know is that they sound really special, so I'd like to get them paired up with amps that don't mind an awkward load 😱
So my questions are
a/ how do the A40's like driving very low impedence loads?
b/ is there anything else I should consider when thinking of using them for driving small electrostatics (crossover frequency ~ 600hz)?
(Oh, and the reason for building amps is that the "ultimate plan" is to build the amps and panels into transmission lines based on this interpretation of the Radford TL http://homepage.mac.com/tlinespeakers/FAL/box-plans/classicTL-revisited-WD.pdf but that's another story)
Anyhow, thanks for reading this far, and would very much appreciate any thoughts and suggestions.
cheers
Nick
I've been reading for a while, but as I didn't manage to spot a thread that helped with the question I'm trying to answer, I guess it's time for my first post.
Bit of background first so you can see where I'm coming from, please bear with me for a moment....
I have a small (2' x 1' x 9") pair of Dynastatic speakers, designed in the UK by an ex-BBC engineer, Alex Shackman, in the '70s, that have 6" cone bass drivers and his 8"x6" electrostatic HF panels. Initially I ran them passive as designed, and they do sound really gorgeous compared to my old setup, but then, because the HF panels are known to be hard to drive, I decided to play about with an active configuration. This works much better and sounds really nice to my ears.
But I do still detect the NAD 3150 power amps that drive the HF units can struggle sometimes; I believe the panels dip below 1ohm at high frequencies. Typically I believe they were normally recommended to be driven by Quad II valve amps, and I could go down the valve route, but then I started thinking about building a pair of amps and was looking at the A40.
Unfortunately there is little in the way of specs available for the Shackman panels, apart from they run at a comparatively low HT voltage of around 400v and have a *very* small stator gap - they use a cotton-like thread to space the membrane from the stators, and were designed in the era of low powered amps.
What I do know is that they sound really special, so I'd like to get them paired up with amps that don't mind an awkward load 😱
So my questions are
a/ how do the A40's like driving very low impedence loads?
b/ is there anything else I should consider when thinking of using them for driving small electrostatics (crossover frequency ~ 600hz)?
(Oh, and the reason for building amps is that the "ultimate plan" is to build the amps and panels into transmission lines based on this interpretation of the Radford TL http://homepage.mac.com/tlinespeakers/FAL/box-plans/classicTL-revisited-WD.pdf but that's another story)
Anyhow, thanks for reading this far, and would very much appreciate any thoughts and suggestions.
cheers
Nick
The A40 will work, but is not the best choice. I would consider
a stock or scaled-down version of the A75 with the folded cascode
front end.
😎
a stock or scaled-down version of the A75 with the folded cascode
front end.
😎
Thankyou 
That's really useful. Looks like I have some more reading to do over the weekend.
cheers
Nick
That's really useful. Looks like I have some more reading to do over the weekend. cheers
Nick
Ok, so having done *some* reading (so many threads, so little time ;-) I also came across those for the recent F5 amplifier, and was wondering if that would be a suitable but slightly less scary alternative for a first build, especially as I read that "it will drive a 2 ohm load without burping, and 1 ohm without misbehaving" in the Op/Service Manual. I think that gets pretty close to what I need for the Shackman panels...
The sheer scale of the A75 seems a bit daunting to me (and SWMBO did go slightly pale when she looked over my shoulder at pics in the A75 gallery and ask "some pointed questions" about my sanity
)
cheers
Nick
The sheer scale of the A75 seems a bit daunting to me (and SWMBO did go slightly pale when she looked over my shoulder at pics in the A75 gallery and ask "some pointed questions" about my sanity
)cheers
Nick
<muzak>
Nearly there on buying all the parts, just the xformers now and then the soldering can begin...
</muzak>
And I've only reached page 201 of the "F5 power amplifier" thread; it seems to be growing faster than I have time to read it
Nearly there on buying all the parts, just the xformers now and then the soldering can begin...
</muzak>
And I've only reached page 201 of the "F5 power amplifier" thread; it seems to be growing faster than I have time to read it
I've finally got a full stereo F5 going (joined the "fry a channel" club and had to do a rebuild after a small error with putting the mosfets the wrong way round) and biassed it all up (easy with 3 meters clipped to the right places 😀). I also built a B1 to drive it.
I was planning to build two full F5's and keep the active setup, but thought I would revert the speakers to passive for a bit, and the F5/B1 combination is more than capable of controlling them, going louder than I need by some way, and sounding really sweet and smooth.
So can i say a huge "thankyou" Nelson. I've had a ton of fun getting back to my soldering iron after a 25 year absence, and learned a whole load of unexpected things about how amplifier layout works (or, mostly in my case, doesn't!). I still have more to do (repackage the whole lot in a wife-acceptable format, solve the transformer buzz etc) plus another amp to build so I can experiment with an active setup, and some later Shackman crossover/power supplies to create new boards for and fix up..
But first I'm going to listen to some music 😎
cheers from UK
Nick
(will post some pics when i figure out how)
I was planning to build two full F5's and keep the active setup, but thought I would revert the speakers to passive for a bit, and the F5/B1 combination is more than capable of controlling them, going louder than I need by some way, and sounding really sweet and smooth.
So can i say a huge "thankyou" Nelson. I've had a ton of fun getting back to my soldering iron after a 25 year absence, and learned a whole load of unexpected things about how amplifier layout works (or, mostly in my case, doesn't!). I still have more to do (repackage the whole lot in a wife-acceptable format, solve the transformer buzz etc) plus another amp to build so I can experiment with an active setup, and some later Shackman crossover/power supplies to create new boards for and fix up..
But first I'm going to listen to some music 😎
cheers from UK
Nick
(will post some pics when i figure out how)
<remembered>
I was worried about biassing, then came up with this, soldering short leads to the resistor legs, which made it a doddle
The meters all attach to a block just out of the bottom of the shot.
And when it was all together, I did a hi tech measurement of heat sink temp 😀
which is slightly high at 59C but seems to sit like that all day so I won't add a fan
I was worried about biassing, then came up with this, soldering short leads to the resistor legs, which made it a doddle
An externally hosted image should be here but it was not working when we last tested it.
The meters all attach to a block just out of the bottom of the shot.
And when it was all together, I did a hi tech measurement of heat sink temp 😀
An externally hosted image should be here but it was not working when we last tested it.
which is slightly high at 59C but seems to sit like that all day so I won't add a fan
- Status
- Not open for further replies.