I need a schematic for a tubed crossover that can cope with 10k load impedance?!? - diyAudio
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Old 8th March 2001, 05:24 PM   #1
hifi is offline hifi  Sweden
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hello!

have anybody done such a design or know any schematic?....preferably a balanced design but that is not required the load of the aleph amp is low 10kohm...but i would like to use a tubed crossover anyway...


/micke
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Old 9th March 2001, 02:43 AM   #2
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Micke,
Balanced crossovers are rare creatures, no matter what kind of load you're talking about. However...
You can 'roll your own.' I'd recommend 6DJ8s, as they are capable of much more output current than, say, a 12AX7. Start with a differential, followed by the filter network, and finish with cathode followers. The cathode followers are important because, like an emitter or source follower, they have lower output impedance and more drive capability. You'll need to go into this having a clear idea of what crossover slopes and frequencies you will need.
There are some tube crossovers (none balanced, mind you) at http://www.tubecad.com. There are other tube crossovers out there, but again, none balanced that I can recall. Hit the links section here in DIY and fan out from there.
It is also possible, if you are building from scratch, to work the crossover slope into the amplifier itself. There are several ways to do this, but it's best to keep it flexible in case you decide to change speakers (or amps) later.

Grey
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Old 9th March 2001, 07:52 PM   #3
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Hi there.
What an interesting site, even for an solid-state guy like me. Will be using some ideas from there in my balanced RIAA-project. Nice things there.
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Old 15th August 2004, 09:41 PM   #4
v-man is offline v-man  United Kingdom
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if your looking for all types of active crossovers that work, have a look at this site. www.marchandelec.com
v-man.
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Old 15th August 2004, 10:55 PM   #5
SY is offline SY  United States
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No reason to use balanced (though you can use a balanced in, convert to single-ended, do the filtration, then back to balanced). I'd heartily second GR's suggestion of 6DJ8s or similar.

I've got a couple of the Marchand boards. They look very nice, but they don't take standard 9 pin PC sockets.
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Old 16th August 2004, 08:00 AM   #6
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Konnichiwa,

Quote:
Originally posted by hifi
have anybody done such a design or know any schematic?....preferably a balanced design but that is not required the load of the aleph amp is low 10kohm...but i would like to use a tubed crossover anyway...
The Marchand Tube crossover schematics are in their downloadable manuals. They can be made balanced I/O by using suitable Transformers. By using a 4:1 Line Input transformer and changing the first buffer stage to one that combines a gain of 16 and a buffer stage you can get the whole X-over to work at a higher level.

Then add suitable output transformers with stepdown (S&B, Jensen and Sowter have nice ones in their pro ranges) and use a follower valve with more current (eg ECC82 instead of ECC83 and reduce th cathode resistor in the marchand design by a factor 5 - 6).

That way you have an output that will tolerate 10K load easily and is balanced. Using a 4:1 stepdown you will have a 10K load translated into 160KOhm in the transformers primary.

Sayonara
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Old 16th August 2004, 06:17 PM   #7
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You mean like my active preamp?

http://webpages.charter.net/dawill/I...e%20Preamp.gif

Cathode follower output will easily cope with 500 ohm loads, although gain will be a bit lower. You can fudge around with the tone stack and add as many stages as you want... a Spice simulator might help ease analysis though...

Tim
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Old 16th August 2004, 07:26 PM   #8
Franz G is offline Franz G  Switzerland
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There was an article how to design tube crossovers in the german magazine ELEKTOR 2/03 with free crossover design
software:

http://www.elektor.de/dl/dl.htm

To download the software, choose:

Frequenz-Weichen mit Röhren 020297-11 Design-Software

I think, the software comes from www.glass-ware.com

Franz
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