Bottlehead Seduction with TX102 TVC?

jdunham · « **on:** 10 Oct 2003, 08:09 pm »

Is anyone using their TX102's with a Seduction phono stage?

Before I order a kit, I just wanted to make sure that the o/p impedance of the Seduction is not going to cause a drastic frequency roll-off in the extreems. I do think that I should have enough gain though to drive my amp directly.

Kind regards,

Jonathan

John Chapman · « **Reply #1 on:** 10 Oct 2003, 11:04 pm »

Hello!

It's very rare to find a source with a high enough output impedance to cause problems. I don't think it would end up 'drastic' but I seem to recall Dan saying the output impedance of the seduction is rather high so we should check what the actual value is. If you can get the figure for output impedance of the seduction and also the input impedance of the amps then we'll run through it.

Many Thansk!

John Chapman
www.bentaudio.com

rodneyAB · « **Reply #2 on:** 11 Oct 2003, 07:45 am »

according to manual, Seduction output impedence is aproximately 7K ohms.

John Chapman · « **Reply #3 on:** 11 Oct 2003, 04:48 pm »

Hello!

Thanks - that is on the high side for sure. I will be cranking up my test gear in the next few days and can run some experiments.

jdunham - do you know what the imput impedance of your amps are? That will let me re-create as best I can your setup.

Thansk!

John Chapman
www.bentaudio.com

clivem · « **Reply #4 on:** 12 Oct 2003, 12:12 am »

Jonathon,

Paul Joppa (Seduction designer) has replied to your post on the Bottlehead board.

http://www.audioasylum.com/forums/bottlehead/messages/70834.html

Sounds like you might get away with just increasing the output cap size on the Seduction.

CliveM

John Chapman · « **Reply #5 on:** 12 Oct 2003, 10:37 pm »

Hello!

Thanks Clive! I happened on that while looking for VSAC updates. Paul has a good point. The recomended coupling cap for a 102 in Thorsten's white paper is 2.2uf - the inductance of the 102 is a bit higher than the value Paul J. used. I would go between 2uF and 4 uF for that cap.

I cranked up the test gear and ran an 8K output impedance into the tx102 with a 100K load (typical tube amp load). No visible prolems result. The hf resonsnace (above 100K) changes a bit as I'd expect but the 20 ohms output impedance and the 8K ohms output impedance track exactly up to well beyond 20Khz.

Might be worth a go...

Many Thanks!

John Chapman
www.bentaudio.com

jdunham · « **Reply #6 on:** 13 Oct 2003, 02:43 pm »

Thanks for the help guys, it looks as though this combination may well be ok.

John, the input impedance of my amp is 100Kohms (actually, a bit higher, I've just measured it) so thanks for that. Certainly the o/p cap on my Tube Dac is 2.2uF and that works well with the TX102. It seems that it will be worth experiementing with a few different values of cap in the Seduction to see what works best.

What I love about this hobby is that so many people I meet and speak to are so helpful! Many thanks once again,

Jonathan