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Author Topic: Can I throw a 5k autoformer in a Smack?  (Read 4743 times)

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Offline xcortes

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Can I throw a 5k autoformer in a Smack?
« on: September 23, 2011, 04:14:48 PM »
Of course I'm thinking a TL 404. I know I'd need to do my switching arangements for impedances and, of course, find how to fit it. I don't need balanced.

thanks
Xavier Cortes

Offline Doc B.

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Re: Can I throw a 5k autoformer in a Smack?
« Reply #1 on: September 24, 2011, 06:35:34 AM »
You wouldn't be able to take the lower leg of the autoformer coil to the cathode of the tube, which is what we have found to sound best and what we do with the OT primary in the Smack. It would have to connect to ground instead. That is why we used the "WE" arrangement that has a negative rail in the original S.E.X. and in the big 6C45 headphone amp, so the bottom leg of the autoformer can attach to the cathode of the tube, which is connected to ground potential. The bottom of the cathode resistor goes to a negative supply.

Also, the TL-404s aren't going to fit on the stock chassis.

I also have to say that balanced operation has me quite impressed.
Dan "Doc B." Schmalle
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Bottlehead Corp.

Offline xcortes

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Re: Can I throw a 5k autoformer in a Smack?
« Reply #2 on: September 24, 2011, 06:54:25 AM »
So the short answer is: not a good idea!

Thanks though.
Xavier Cortes

Offline xcortes

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Re: Can I throw a 5k autoformer in a Smack?
« Reply #3 on: September 24, 2011, 02:59:48 PM »
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I also have to say that balanced operation has me quite impressed.

My main headphones, Sony MDR-R10 are not balanced. I guess I can have them recabled. In your experience, is the change from balanced Smack to unbalanced Sex (Ni MQ) significantly better?

In my past experience the improvements going to MQ iron have been extreme. I guess it would be a long shot asking for MQ Smack iron, right? That would be a no brainer for me?

Thanks
Xavier Cortes

Offline Doc B.

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Re: Can I throw a 5k autoformer in a Smack?
« Reply #4 on: September 24, 2011, 07:28:45 PM »
Yes, in my experience going to balanced Smack from MQ'd single ended S.E.X. is a big jump. I've only listened to four pairs of headphones wired balanced - K1000s, HD600s, HD650s and my ribbon prototypes. Based on what I hear in those I think rewiring something as good sounding as the MDR-R10 to balanced might be pretty phenomenal. 
Dan "Doc B." Schmalle
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Bottlehead Corp.

Offline xcortes

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Re: Can I throw a 5k autoformer in a Smack?
« Reply #5 on: September 25, 2011, 02:44:01 AM »
No more questions on th R10s. I'll have them recabled.

Question about the k1k. You say you heard them balanced. Was that through the Smack too? How did that compare to listening them through the unbalanced Paramounts?

Thanks again!

Xavier Cortes

Offline Doc B.

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Re: Can I throw a 5k autoformer in a Smack?
« Reply #6 on: September 25, 2011, 06:53:20 AM »
Hmm, that's an interesting question to post to PJ. Peej, can we derive a CT from the taps on the OT-1 secondary wired for 16 ohms, and run it true balanced? If not I can try the virtual CT that we do on the lower impedance settings on the Smack. As it is the signal colds for the two channels are only connected to ground back at the preamp so we may already be getting most of the benefit of balanced operation.

I've also used the S.E.X. 2.1 on the 32 ohm tap, which would not have isolated grounds unless the secondary safety grounds are lifted. Suppose we might be able to do the same trick there, and we do plan to offer the impedance switch board for the S.E.X. 2.1. That by the way seems to be enough power to run the K1Ks reasonable well. I haven't tried Smack because I don't have the right termination for the K1K cable, they came with bare ends that I simply attached to bananas. I suspect that Smack won't have enough drive.
Dan "Doc B." Schmalle
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Bottlehead Corp.

Offline Paul Joppa

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Re: Can I throw a 5k autoformer in a Smack?
« Reply #7 on: September 25, 2011, 11:24:03 AM »
I'm pretty sure the OT-1 can be configured for center-tapped output into 4 or 16 ohms, but not 8 ohms. The virtual center tap should work well, though.

Incidentally, Mike does sometimes make an 8K:500CT version of the B-7.
Paul Joppa

Offline xcortes

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Re: Can I throw a 5k autoformer in a Smack?
« Reply #8 on: September 26, 2011, 04:28:49 AM »
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As it is the signal colds for the two channels are only connected to ground back at the preamp so we may already be getting most of the benefit of balanced operation.


That's precisely what I was thinking. I would expect that most of the benefits from the "balanced" connection come from not sharing the cold in both channels. The other benefit would be less pick up noise which in such a short cable shouldn't be critical or even noticeable.

Xavier Cortes

Offline Doc B.

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Re: Can I throw a 5k autoformer in a Smack?
« Reply #9 on: September 26, 2011, 05:17:35 AM »
It would be interesting to study what is happening when we go to balanced. The first time I heard balanced vs. SE on HD 650s we noticed a more 3D soundstage, things were less "in the head". When we made the change on my HD600s last week it was a little more controlled experiment, as we just changed the connector on the same cable rather than listening to two different cables, and we were in the listening room rather than a meet environment with its elevated background noise. In that we case noticed that the bass really improved in dynamics and clarity as well as the soundstage getting better.
Dan "Doc B." Schmalle
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Bottlehead Corp.

Offline xcortes

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Re: Can I throw a 5k autoformer in a Smack?
« Reply #10 on: September 26, 2011, 04:52:32 PM »
here's another theory:


Actually most all of the crosstalk is due to the common ground contact resistance of the TRS plug/jack combination.

In other words, even single-ended output amplifiers benefit from a 4 pin XLR with the common ground accomplished via a good low resistance solder connection inside the chassis.


http://www.audioasylum.com/forums/head/messages/179.html

Xavier Cortes

Offline keto

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Re: Can I throw a 5k autoformer in a Smack?
« Reply #11 on: September 27, 2011, 05:48:40 AM »
Hey Xavier,

how would you go from a balanced-out linestage to two balanced-in monoblocks, using the single 4-pin approach?
A 4-pin XLR out, a "4-pin to dual 3-pin" custom cable, and dual 3-pin XLR inputs?
Second, how would you do a monoblock power amp balanced out to speakers?
A 3-pin out, with a centertap created from two resistors?
I find all this intriguing and confusing!

--keto
Tom Jones