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December 05, 2019, 04:52:02 AM

Author Topic: Impedance switch for SII?  (Read 898 times)

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Offline Deke609

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Re: Impedance switch for SII?
« Reply #15 on: October 16, 2018, 02:01:43 PM »
Minimum current rating for the DPDTs?
Derek
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Roon Intel NUC ->  Yggdrasil DAC -> BeePre (w/ BeeQuiet and EML 300B)  -> Kaiju (w/ DCFil and EML 300B) or Stereomour II (2A3 [EML Mesh] and 45 Conversion [EML 45B])  -> Audeze LCD4

Online Paul Birkeland

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Re: Impedance switch for SII?
« Reply #16 on: October 16, 2018, 02:11:44 PM »
Ohm's Law can tell you this:

The amp makes 3.5W into 8 Ohms.  Solve for current, then add some safety margin.

(Repeat as necessary for other impedance taps, all of which will make 3.5W but into a different load)
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Deke609

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Re: Impedance switch for SII?
« Reply #17 on: October 16, 2018, 02:23:31 PM »
Hah!  Thanks PB. That was dumb!
Derek
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Roon Intel NUC ->  Yggdrasil DAC -> BeePre (w/ BeeQuiet and EML 300B)  -> Kaiju (w/ DCFil and EML 300B) or Stereomour II (2A3 [EML Mesh] and 45 Conversion [EML 45B])  -> Audeze LCD4

Offline Deke609

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Re: Impedance switch for SII?
« Reply #18 on: October 19, 2018, 11:04:30 AM »
I'm going to build the impedance switches this wknd and have a few questions:

(1) If I were to leave out the bal/unbal part of the circuit and only build for impedance switching, I can leave out the resistors, right?  Their only purpose is to provide hot and cold references to ground in balanced mode?
 
(2) Is there any performance advantage (sound, health of the amp, etc) in implementing balanced at the OTs rather than at the speakers? If there is an advantage to balancing at the OTs, what value of resistor should be used? Anything in the same 50-100 Ohm range that applies when balancing at the speaker outs?

Many thanks,

Derek
Derek
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Roon Intel NUC ->  Yggdrasil DAC -> BeePre (w/ BeeQuiet and EML 300B)  -> Kaiju (w/ DCFil and EML 300B) or Stereomour II (2A3 [EML Mesh] and 45 Conversion [EML 45B])  -> Audeze LCD4

Online Paul Birkeland

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Re: Impedance switch for SII?
« Reply #19 on: October 19, 2018, 12:50:18 PM »
(1) If I were to leave out the bal/unbal part of the circuit and only build for impedance switching, I can leave out the resistors, right? 
In the schematic PJ posted, a resistive center tap is provided for two of the balanced impedance settings, while the other two use the junction of the two secondary windings as the center tap.   

(2) Is there any performance advantage (sound, health of the amp, etc) in implementing balanced at the OTs rather than at the speakers? If there is an advantage to balancing at the OTs, what value of resistor should be used? Anything in the same 50-100 Ohm range that applies when balancing at the speaker outs?
You're talking about putting resistors that handle very little current on one side or the other of a few inches of wire. 
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Deke609

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Re: Impedance switch for SII?
« Reply #20 on: October 19, 2018, 01:39:45 PM »
Thanks PB.

I'll stick with balancing at the speaker outs and build two 2 DPDT boards (sans resistors) for impedance switching.
Derek
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Roon Intel NUC ->  Yggdrasil DAC -> BeePre (w/ BeeQuiet and EML 300B)  -> Kaiju (w/ DCFil and EML 300B) or Stereomour II (2A3 [EML Mesh] and 45 Conversion [EML 45B])  -> Audeze LCD4

Offline Deke609

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Re: Impedance switch for SII?
« Reply #21 on: October 20, 2018, 06:23:51 PM »
I built and installed the impedance switching boards today and they work! Very cool.

My only issue is that flux found its way to the contact pads of the DPDT slide switches. I was able to get most of the flux off the throws, but the poles at the center are inaccessible without opening up the switch. Does anyone know a trick for cleaning the center poles of slide switches?

cheers and thanks,

Derek
Derek
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Roon Intel NUC ->  Yggdrasil DAC -> BeePre (w/ BeeQuiet and EML 300B)  -> Kaiju (w/ DCFil and EML 300B) or Stereomour II (2A3 [EML Mesh] and 45 Conversion [EML 45B])  -> Audeze LCD4

Offline Deke609

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Re: Impedance switch for SII?
« Reply #22 on: October 21, 2018, 03:21:06 AM »
And here is how I implemented PJ's ingenious 2-DPDT solution for impedance switching, in case anyone is interested. I dealt with balancing separately.

I believe my implementation is correct, but can't vouch that it is. But it sounds good, other than 16 Ohms which is too quiet and distorted on my LCD4s - I think the current is too low to drive them. 
Derek
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Roon Intel NUC ->  Yggdrasil DAC -> BeePre (w/ BeeQuiet and EML 300B)  -> Kaiju (w/ DCFil and EML 300B) or Stereomour II (2A3 [EML Mesh] and 45 Conversion [EML 45B])  -> Audeze LCD4

Online Paul Birkeland

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Re: Impedance switch for SII?
« Reply #23 on: October 21, 2018, 07:24:04 AM »
But it sounds good, other than 16 Ohms which is too quiet and distorted on my LCD4s - I think the current is too low to drive them.
No, this is likely a wiring issue with the proto board.  16 ohms should be noticeably louder than the lower impedance settings. 
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Deke609

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Re: Impedance switch for SII?
« Reply #24 on: October 21, 2018, 07:46:39 AM »
Thanks PB. Hmm. Weird that 2, 4 and 8 sound great.  I'll re-evaluate the 16 Ohm config. I must have goofed something specific to the 16 Ohm wiring.
Derek
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Roon Intel NUC ->  Yggdrasil DAC -> BeePre (w/ BeeQuiet and EML 300B)  -> Kaiju (w/ DCFil and EML 300B) or Stereomour II (2A3 [EML Mesh] and 45 Conversion [EML 45B])  -> Audeze LCD4

Offline Deke609

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Re: Impedance switch for SII?
« Reply #25 on: October 21, 2018, 07:58:41 AM »
Update: checked my wiring, and couldn't find a problem in my implementation, so I tried switching to 16 Ohms again ... and lo and behold it sounds great and louder than at 8 Ohms.  Not sure what was going on last night when I tested it. Last night it sounded horrible. Maybe the flux on the switch pads prevented good contact?  16 Ohms was the first config I tried last night.  Maybe subsequent switching cleaned the switches?  Dunno. But it's working now.

« Last Edit: October 21, 2018, 09:12:58 AM by Deke609 »
Derek
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Roon Intel NUC ->  Yggdrasil DAC -> BeePre (w/ BeeQuiet and EML 300B)  -> Kaiju (w/ DCFil and EML 300B) or Stereomour II (2A3 [EML Mesh] and 45 Conversion [EML 45B])  -> Audeze LCD4