Output Impedance Switch Kit on SEX 2.0?

[Cary]

Can the Output Impedance Switch Kit be installed on the SEX 2.0?

Wishing everyone a Happy New Year!

Cary

[kgoss]

I believe you have to install the 2.1 output transformers and chokes first.

[fullheadofnothing]

No. Even with the upgrade iron it is still incompatible with the way the transformers are wired.

[DDDamian]

That's a shame as I just ordered the 2.1 iron upgrade for my S.E.X 2.0 w/C4S upgrade.

I was just looking at other upgrades and have a shopping cart with some Mundorf Supremes (2.2uf and 0.1uf) to replace the interstage and parafeed caps.

Was thinking with the 2.1 iron it'd be possible to install the impedance switching kit?

If not, what's my easiest way to go balanced with this gal? My primary source is a TEAC UD-501 DAC which has balanced XLR outs, along with RCA's. My primary objective is making my LCD2.2's sound their best.

I was thinking of:
a) removing the 120ohm headphone jack resistor and replacing the 1/4" jack with an XLR or
b) using the speaker taps and a banana-jack to balanced XLR connector

What's my easiest path here for full balanced from input to output?

Cheers!

[Doc B.]

Balanced output to the headphones is pretty simple if the headphone is set up for separate right and left signal cold connections. You just do what we do, float the cold signal rather than grounding it to safety ground, and add resistors from hot to ground and cold to ground.

Making the input accomodate true balanced connection would require installing an input transformer. But to what end? Unless it is a differential output (aka push-pull) from the output of the DAC chip the balanced output of the TEAC quite possibly adds circuitry in the signal path that really isn't necessary and chances are it sounds better out of the RCA output. And then of course you would have an extra transformer in the signal path at the SEX.

The notion that "balanced" is automatically better is one of the more insidious audiophile myths. It often as not adds complexity and the possibility for additional coloration of the sound.

[DDDamian]

Thanks Doc. The Teac does have a pair of Muses op-amps in push-pull on each output channel to XLR's on the back, and supposedly sounds better (more dynamic, deeper bass) run that way.

I've seen a lot of posts by members who use the virtual ground method you mention, so was curious about a fully balanced path back to the DAC. No biggie - as you suggest the differences may be very subjective although many swear they prefer balanced. All my main three cans (HD-650, HE-400 and LCD2.2) can be wired either way. Then again, the meaning of the acronym for this amp is not totally lost on me 

This is my main go-to amp for 90% of my listening, with the Crack + SB second for use with the 650 when I want the OTL sound. I'm just trying to squeeze all the goodness I can from it. It already has the C4S kit installed, caps and iron upgrade on the way, and plans for a ladder-style pot in the works.

The mainline will be my winter build to complete the trio

Thanks for your comment and all the wonderful sound you've brought us!

[Paul Birkeland]

You'll need to "undo" the autoformer wiring to get the balanced output on the SEX 2.0.

If you go with a very literal installation of the Impedance Switch kit, you will end up removing all the current wires that leave the secondary windings of the output transformer, which is part of what you need to do.  Other than that, the red primary OPT wire needs to make it to the terminal where the 1.0uF Solen parafeed cap connects, and the black primary wire connects along the bare ground buss. 

On the headphone jack, you'll end up removing the resistors on the jack and converting the jack to a switching jack (speakers off when headphones are plugged in).  This is made pretty clear in the manual as well.

Having accomplished all of this, you'll now have balanced outputs available at the speaker jacks.

-PB

[DDDamian]

Thanks PB! I think that I'm overdue to sit down and sketch this schematic out lol. My brain works better translating the point-to-point back to a circuit diagram.

My understanding of the Impedance Switching kit is that it implements the virtual ground for the 16ohm and 32ohm taps when switching to balanced, along with providing switching for the secondary taps?

EDIT: And is the post further above incorrect when it says the Impedance Switching kit cannot be used on a 2.0 with upgraded iron?

[Doc B.]

I'll note that this thread has created a bit of consternation among our own ranks, and justifiably so. I was remiss in mentioning what PB did, that converting the 2.0 to balanced out is rather involved because you have to first reconfigure the amp from autoformer output to transformer output. That's why the 2.0 upgrade kit is different than the 2.1 (2.1 comes set up for transformer output) - and why we offer the impedance switch kit for 2.1 only. It's doable on a 2.0, but not just a connect the dots kind of modification. You do need to have some understanding what is involved and convert the amp first.

[DDDamian]

That strikes fear into me - I'm unlikely to tackle it unless I had a very clear idea of what the end-circuit should look like. Part of the problem with point-to-point instructions is they may not consider all factors like the various upgrades (in this case iron and the C4S kit, then presumably the Impedance Switching kit for the virtual ground and convenient impedance switching)...

Edit: no biggie here - I don't NEED this Not wanting to distract the ranks there with something the amp is just not designed to do. I am perfectly happy to upgrade the iron and a few caps and call it a day until I get around to the mainline build.

[Paul Birkeland]

That strikes fear into me - I'm unlikely to tackle it unless I had a very clear idea of what the end-circuit should look like. Part of the problem with point-to-point instructions is they may not consider all factors like the various upgrades (in this case iron and the C4S kit, then presumably the Impedance Switching kit for the virtual ground and convenient impedance switching)...

This is really a good idea.  I am pretty good at waiving my hands about how one might go about doing something, but if things don't quite go right, it becomes difficult to support a product that is now a one-off.

-PB

[DDDamian]

This is really a good idea.  I am pretty good at waiving my hands about how one might go about doing something, but if things don't quite go right, it becomes difficult to support a product that is now a one-off.

-PB

I'll play with the other mods first and by the time they settle in and I adjust to the new sound the Mainline will be calling

Thanks for the advice, and the second more sagely advice