tubes in class d?

beamnet · 11th December 2005, 04:47 PM

Hello there,

I am looking at class D amps and wonder:

"Could i use tubes?"

It seems like it would make tubes unsuitable for analogue audio worth a try in class d...

Output using tubes i can see, maybe even the ocillator?

Bas

Oh, and i am not into tubes because they sound good, i am into tubes because they are cool

Pano · 11th December 2005, 07:12 PM

Quote:

Originally posted by beamnet
"Could i use tubes?"

Don't see why not. I used to work in a theater that used tube dimmers. Low switching frequency, to be sure, but very high power. You'd have to find tubes that can switch fast and handle a bit of power.

So come up with a circuit for us! I may not be pactical, but it might be fun.

BTW, tubes aren't cool- they're hot.

poobah · 11th December 2005, 07:25 PM

use RF tubes... whole new line of thinking...

beamnet · 11th December 2005, 07:45 PM

That's what i had in mind...all those rf tubes lying around...

I am a total zero on class D

I could not even begin to think about making a circuit

The easiest way would be to just adept an output stage for tubes..

Bas

raintalk · 12th December 2005, 04:42 AM

This would definitely be a fun thing to do!

Somewhere I recall that some gaseous lamp dimmers were high frequency. I wonder if some old circuit could be adapted?

el`Ol · 12th December 2005, 04:52 AM

I read somewhere that switching tubes were used in high-power, high-voltage applications before the IGBTs were invented (which are very slow and not suitable for switching).

hermanv · 12th December 2005, 06:24 AM

The advantage of class D designs is efficiency. To make class D sound good requires some extraordinary effort. Since tubes can not saturate the efficiency is mostly gone.

Switching frequencies of at leat 1 MHz with a current of say 5 Amps to have any useful power.

It would be difficult if not impossible to use a transformer (high degree of DC imbalace) so an inductor impedance match would be neccessary. To do it right you need to drive both positive and negative directions so you need one of those PNP tubes, alternatively you bias the speaker up at some positive voltage leading to a whole other set of problems.

None of this is impossible but about now it should be starting to sound like it's not the best idea ever conceived.

For this much effort a first class conventional tube amp could be built. There's nothing wrong with that as it takes advantage of the tube being a transconductance devide instead of a current mode device.

If you just want to drive high currents with vacuum tubes, then consider an OTL amp.

IVX · 12th December 2005, 09:06 AM

The major benefit of the tubes is better linearity ( many other properties is worse), but if they will work like switch ON/OFF only, the linearity will not so important.

mzzj · 12th December 2005, 09:12 AM

Quote:

Originally posted by el`Ol
I read somewhere that switching tubes were used in high-power, high-voltage applications before the IGBTs were invented (which are very slow and not suitable for switching).

And are still used where extremely high power and fast switching times are needed. Thyratrons, ignitrons and so on...

beamnet · 12th December 2005, 11:09 AM

cool, some good response.

a few things

- a HAVE a huge 70+watt puspull tube amp.

- I never implied it was a sane thing to do

- except for the output, lots of other tasks could be done with tubes.
I seem to recall tubes that can function like comparators, but i don't know whee i saw that..

pnp tubes..... there's no such thing

can't you just use a normal (or even limited bandwidth, to cut off any hf) pushpull OPT? My guess is that it would filter the 1mHz quite adequately..

Bas

11th December 2005, 04:47 PM	#1
beamnet diyAudio Member Join Date: Jun 2004 Location: enschede	tubes in class d? Hello there, I am looking at class D amps and wonder: "Could i use tubes?" It seems like it would make tubes unsuitable for analogue audio worth a try in class d... Output using tubes i can see, maybe even the ocillator? Bas Oh, and i am not into tubes because they sound good, i am into tubes because they are cool

12th December 2005, 09:06 AM	#8
IVX diyAudio Member Join Date: Jul 2003 Location: Everywhere (Buddhist's context)	The major benefit of the tubes is better linearity ( many other properties is worse), but if they will work like switch ON/OFF only, the linearity will not so important. __________________ Best regards, E1.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
813 RCA amplifier - 25w, class A1, single ended,2 tubes,Rout~1ohm	audiodesign	Tubes / Valves	5	19th September 2010 07:34 PM
Hybrid Class D with 6n6p tubes	Koifarm	Tubes / Valves	9	22nd February 2009 10:47 AM
Just an idea: Tubes and Class D	NeoY2k	Class D	5	6th September 2008 07:43 PM
Class-T with Tubes?	beepx1	Class D	2	11th August 2004 06:41 PM
Tubes in Class D amplifiers	Polimorph	Tubes / Valves	45	30th July 2004 11:37 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

11th December 2005, 07:25 PM	#3
poobah diyAudio Member Join Date: Nov 2005	use RF tubes... whole new line of thinking...

11th December 2005, 07:45 PM	#4
beamnet diyAudio Member Join Date: Jun 2004 Location: enschede	That's what i had in mind...all those rf tubes lying around... I am a total zero on class D I could not even begin to think about making a circuit The easiest way would be to just adept an output stage for tubes.. Bas

12th December 2005, 04:42 AM	#5
raintalk diyAudio Member Join Date: Jul 2004 Location: Seattle USA	This would definitely be a fun thing to do! Somewhere I recall that some gaseous lamp dimmers were high frequency. I wonder if some old circuit could be adapted?

12th December 2005, 04:52 AM	#6
el`Ol diyAudio Member Join Date: May 2005 Location: Bavarian Forest	I read somewhere that switching tubes were used in high-power, high-voltage applications before the IGBTs were invented (which are very slow and not suitable for switching).

12th December 2005, 06:24 AM	#7
hermanv diyAudio Member Join Date: Apr 2004 Location: Northern California	The advantage of class D designs is efficiency. To make class D sound good requires some extraordinary effort. Since tubes can not saturate the efficiency is mostly gone. Switching frequencies of at leat 1 MHz with a current of say 5 Amps to have any useful power. It would be difficult if not impossible to use a transformer (high degree of DC imbalace) so an inductor impedance match would be neccessary. To do it right you need to drive both positive and negative directions so you need one of those PNP tubes, alternatively you bias the speaker up at some positive voltage leading to a whole other set of problems. None of this is impossible but about now it should be starting to sound like it's not the best idea ever conceived. For this much effort a first class conventional tube amp could be built. There's nothing wrong with that as it takes advantage of the tube being a transconductance devide instead of a current mode device. If you just want to drive high currents with vacuum tubes, then consider an OTL amp.

12th December 2005, 11:09 AM	#10
beamnet diyAudio Member Join Date: Jun 2004 Location: enschede	cool, some good response. a few things - a HAVE a huge 70+watt puspull tube amp. - I never implied it was a sane thing to do - except for the output, lots of other tasks could be done with tubes. I seem to recall tubes that can function like comparators, but i don't know whee i saw that.. pnp tubes..... there's no such thing can't you just use a normal (or even limited bandwidth, to cut off any hf) pushpull OPT? My guess is that it would filter the 1mHz quite adequately.. Bas