ZV9 or F2 for Fostex?

kenev · 9th March 2007, 08:19 AM

I need your help deciding on which transconductance amp is most suited for driving a pair of Fostex drivers.

I have a pair of FE167E in TQWPs (aka Voigt Pipes) and also a pair of FE206E waiting for a pair of BLHs to be built. Having read Nelson Pass's paper on current driven full-range drivers, I have already built a vacuum tube transconductance amplifier, which sounds absolutely marvellous with the Fostexes.

But, I also want to build a solid state transconductance amplifier. So, having read a large number of posts here, I will have to decide which of the two mentioned (ZV9 or F2) would be better suited for my case.

Any help from the experts here will be welcomed.

Regards,
Evangelos

vitalstates · 9th March 2007, 09:23 AM

Hi Kenev

I'm sorry I can't answer the question but I'm about to finish an F2 to drive a pair of 206E voigt pipes (see web page).

But I am intrigued by your mention of transconductance valves....any chance of some detail??

Regards

Ed

kenev · 9th March 2007, 10:37 AM

Hi Ed,

Here is a link to the mentioned amplifier:

http://www.audioasylum.com/scripts/t...nequest&m=5167

I have made a change to the original schematic: I use a ccs fed shunt regulated voltage supply for the screens, using Gary Pimm's CCS and a stack of 0A2 and 0B2 VR tubes, for about 255 volts between screen and cathode. Sounds much better this way.

Originally, I had built the lower power EL84 version (ca. 2.5W)

http://www.audioasylum.com/scripts/t...nequest&m=2553

but there was a lack of power, more evident on loud passages and dynamic parts, so I went for the higher power version. Note that, even it is titled a "9W amp", to get those 9 watts, you have to increase B+ to a much higher voltage in order to increase the tube's power dissipation to 36W. With a B+ of 450V, as shown, power dissipation is 24W, so output power is around 6 watts, not bad for a Fostex. I'm using KT88s. Had tried EL509s, but there were producing a lot of distortion.

Regards,
Evangelos

Vix · 9th March 2007, 12:57 PM

ZV9, if you can obtain the Jfets. If not, an F2 will work.

Brett · 19th May 2007, 12:34 PM

Evangelos, I'm curios about your tube amps, but can't get into the AA links provided. Could you post here or provide other info on them please?

stefanobilliani · 19th May 2007, 03:26 PM

The ZEN V9 is cool becouse with a couple of switches you can alternate between current source and voltage amplifier . And choose for yourself or sometime also for the music you are listen to . In courrent source mode dont forget to load the output with a power resistor wich is 22ohm for the FE206E .
Use the best ( non inductive ) power resistors avaiable , and match well the J fets

kenev · 20th May 2007, 04:58 AM

Quote:

Originally posted by Brett
Evangelos, I'm curios about your tube amps, but can't get into the AA links provided. Could you post here or provide other info on them please?

Brett, I just tried the links mentioned above and they work fine. I don't know why you can't open them. Maybe you could try again.

Brett · 20th May 2007, 08:39 AM

Works fine now. It asked for username and password before and then rejected my valid AA info.

Cheers.

kenev · 20th May 2007, 07:28 PM

Quote:

Originally posted by Brett
Works fine now. It asked for username and password before and then rejected my valid AA info.

Cheers.

That's good. Have a nice reading!

Regards,
Evangelos

9th March 2007, 08:19 AM	#1
kenev diyAudio Member Join Date: Oct 2002 Location: Athens, Greece	ZV9 or F2 for Fostex? I need your help deciding on which transconductance amp is most suited for driving a pair of Fostex drivers. I have a pair of FE167E in TQWPs (aka Voigt Pipes) and also a pair of FE206E waiting for a pair of BLHs to be built. Having read Nelson Pass's paper on current driven full-range drivers, I have already built a vacuum tube transconductance amplifier, which sounds absolutely marvellous with the Fostexes. But, I also want to build a solid state transconductance amplifier. So, having read a large number of posts here, I will have to decide which of the two mentioned (ZV9 or F2) would be better suited for my case. Any help from the experts here will be welcomed. Regards, Evangelos

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9th March 2007, 09:23 AM	#2
vitalstates diyAudio Member Join Date: Jan 2006 Location: uk	Hi Kenev I'm sorry I can't answer the question but I'm about to finish an F2 to drive a pair of 206E voigt pipes (see web page). But I am intrigued by your mention of transconductance valves....any chance of some detail?? Regards Ed

9th March 2007, 10:37 AM	#3
kenev diyAudio Member Join Date: Oct 2002 Location: Athens, Greece	Hi Ed, Here is a link to the mentioned amplifier: http://www.audioasylum.com/scripts/t...nequest&m=5167 I have made a change to the original schematic: I use a ccs fed shunt regulated voltage supply for the screens, using Gary Pimm's CCS and a stack of 0A2 and 0B2 VR tubes, for about 255 volts between screen and cathode. Sounds much better this way. Originally, I had built the lower power EL84 version (ca. 2.5W) http://www.audioasylum.com/scripts/t...nequest&m=2553 but there was a lack of power, more evident on loud passages and dynamic parts, so I went for the higher power version. Note that, even it is titled a "9W amp", to get those 9 watts, you have to increase B+ to a much higher voltage in order to increase the tube's power dissipation to 36W. With a B+ of 450V, as shown, power dissipation is 24W, so output power is around 6 watts, not bad for a Fostex. I'm using KT88s. Had tried EL509s, but there were producing a lot of distortion. Regards, Evangelos

9th March 2007, 12:57 PM	#4
Vix diyAudio Member Join Date: Nov 2003 Location: Somewhere on Planet Earth	ZV9, if you can obtain the Jfets. If not, an F2 will work.

19th May 2007, 12:34 PM	#5
Brett diyAudio Member Join Date: Jan 2002	Evangelos, I'm curios about your tube amps, but can't get into the AA links provided. Could you post here or provide other info on them please?

19th May 2007, 03:26 PM	#6
stefanobilliani diyAudio Member Join Date: Jun 2002 Location: Italy	The ZEN V9 is cool becouse with a couple of switches you can alternate between current source and voltage amplifier . And choose for yourself or sometime also for the music you are listen to . In courrent source mode dont forget to load the output with a power resistor wich is 22ohm for the FE206E . Use the best ( non inductive ) power resistors avaiable , and match well the J fets

20th May 2007, 08:39 AM	#8
Brett diyAudio Member Join Date: Jan 2002	Works fine now. It asked for username and password before and then rejected my valid AA info. Cheers.

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