OT-2 switch question

TadS · 2781

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Offline TadS

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on: December 03, 2011, 04:05:46 AM
Hi Folks--
I am getting ready to assemble my SEX2.1 kit and can't decide on whether to wire for 8 or 32 ohms.  I may end up using mostly for 300ohm headphones, but probably some duty with 8ohm speakers.  I was thinking about using a DPDT switch on each transformer as shown in the attached jpg.  I would certainly make sure the amp is unplugged and the caps are drained before switching, but are there other considerations (like sonic quality) when switching the OT?  Also, this schematic is "back of the envelope" for me.  I think this should work okay, but I would appreciate any alerts to why it would not--or should not--be done. Thanks, for any input you might have!
--TadS.


Offline Jim R.

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Reply #1 on: December 03, 2011, 05:39:47 AM
Tad,

If you can be patient for a bit longer there will be some BHswitch boards for these transformers that will allow you to easily change output impedance settings, as well as switch between single-ended and balanced mode.

HTH,

Jim

Jim Rebman -- recovering audiophile

Equitech balanced power; uRendu, USB processor -> Musette DAC -> 5670 tube buffer -> Finale Audio F138 FFX -> Cain and Cain Abbys near-field).

s.e.x. 2.1 under construction.  Want list: Stereomour II

All ICs homemade (speaker and power next)

Offline Doc B.

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Reply #2 on: December 03, 2011, 07:08:36 AM
Meantime, the 8 ohm tap will work fine with 300 ohm headphones since the S.E.X. can swing so much output voltage. We've been using ours that way as we are alternating between headphones and Blumenstein Orcas in our listening station.

Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.

Offline TadS

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Reply #3 on: December 04, 2011, 06:06:39 AM
Thanks, Jim and Doc!

I am now even less sure of whether I want to incorporate a switch or not.  I guess my initial question was really to get info about whether the scheme that I posted for wiring the switch was viable, or perhaps there was a better way to do it.  I am also wondering about how robust the switch would need to be.  It looks like the hookup wire is 20-gauge so I probably wouldn't need some high amperage-rated switch.  Also, a simple DPDT switch is something I could find locally. 

The BH switch is intriguing in that I might want to play with balanced outputs in the future.  But I think for now, a simple switch between 8 and 32 ohm output impedance would suit my needs.  From Doc's post, it sounds like that may not even be needed.  As long as I am not stressing the amp and the sound quality does not suffer from it, using my HD-650s with it wired for 8-ohm output would certainly be the simple solution.  I have a few more days to contemplate this as I am still finishing the chassis plate and base.  Thanks, again for your replies.

--Tad


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