Any interest in measuring a loudspeaker/amplifier A-B switcher?

[vkhong]

Duok Audio VU3 (100W max per channel due to VU meter max position)
Dual Analog VU Meter 2-Way Amplifier/Speaker Audio Switcher Box
AC 250V 5A large current relay, micro-USB 5VDC power source, remote controller included

I am curious as to any measurable degradation when quality relays are in use. My collection of loudspeakers is growing and am looking for an easy way to switch between loudspeaker pairs. Amplifiers: Bob Carver Crimson 275, B&K ST-140. Loudspeakers: Klipsch KLF-30, Paradigm Studio 100 v3/ Studio 20 v3 / Monitor 11 v2, 7se Mk II, and B&O Beovox RL140.

 

[Kal Rubinson]

My concern about this is whether it switches both leads in each channel or does it switch only the (+) lines while shorting all the (-) lines, as does their other speaker/amp switches. The latter is not compatible with the many amps with non-ground-referenced outputs.

 

[vkhong]

I have a unit on the way. I will use the multimeter continuity test to check one (-) post against all other (-) posts. Hopefully all will fail except for the switched (-) post.

 

[Wolf]

I agree with Kal. I built a common neg 3-pair switcher, but I don't switch amplifiers with it.

Also of concern, if you are using tube amps, make sure the switch is make before break on the speaker side, or if not as it is likely is to switch on the amp side, that the amplifier always has a load termination. In my implementation, I used avalanche devices on the outputs to limit arcing, and placed a CR filter across the input of the switcher from the amp to keep them loaded while under switching operation.

You'd think these devices would be built to avoid issues, but most are simple switches.

 

[Wolf]

Oh, and be vigilant to not switch while playing and at higher volumes. While I built the safeguards into mine to make it theoretically possible in the case of incident, it does not mean the device can handle it.

 

[vkhong]

The unit arrived today. I tested with the multimeter continuity test. Open = OL, closed = 0.000V. Testing from the amp side, the speaker (+) and (-) are switched respectively. There is no common (-).
Testing from the amp site, the speaker switch seems to break then make. I used a set of B&W DM601 to connect to the speaker posts 1-Left and 2-Left. Testing from Amp A-Left, continuity shows 0.001V (closed). When switching speakers, it drops to about 0.003V (+/- 0.001) and returns to 0.001V.
Based on this two points. It switches speakers correctly (both + and -), but breaks before making the next speaker connection, so tube amps will have to be powered off between speaker selection. Is that correct?

 

[Kal Rubinson]

The unit arrived today. I tested with the multimeter continuity test. Open = OL, closed = 0.000V. Testing from the amp side, the speaker (+) and (-) are switched respectively. There is no common (-).
Testing from the amp site, the speaker switch seems to break then make. I used a set of B&W DM601 to connect to the speaker posts 1-Left and 2-Left. Testing from Amp A-Left, continuity shows 0.001V (closed). When switching speakers, it drops to about 0.003V (+/- 0.001) and returns to 0.001V.
Based on this two points. It switches speakers correctly (both + and -), but breaks before making the next speaker connection, so tube amps will have to be powered off between speaker selection. Is that correct?

Can you measure with the ohmmeter settings?
Can you post some pix of the innards, please?

 

[vkhong]

Can you measure with the ohmmeter settings?
Can you post some pix of the innards, please?

I'm thinking the speaking switching process is break/make 8Ω --> ∞Ω --> 8Ω, instead of the ideal 8Ω --> 4Ω --> 8Ω. I will retest with 2 pairs of 8-ohm speakers and the ohm meter.

My digital ohm meter has a slow reaction time, so I don't know if it will accurately measure the break/make during speaker selection. It may not reflect a momentary open circuit. The unit has a factory sticker seal, so I can't open it without voiding the warranty.

 

[Kal Rubinson]

Thanks.

 

[Wolf]

My gut reaction would be to power down a tube-amp before switching. The B&K won't care.

 

[vkhong]

Can you measure with the ohmmeter settings?

Measuring across the B&W DM601 high-frequency binding posts yielded 4.1Ω. Same when measuring the same posts through the switch. Both loudspeakers in the pair measured the same 4.1Ω. When I switched between Speaker 1-Left and Speaker 2-Left, and I measured across Amp A-Left. The digital ohm meter stayed at 4.1Ω. The meter does not react quick at all. Occasionally, I'd catch a 4.2Ω or 5.1Ω , but for the most part, it stayed at 4.1Ω at the Amp posts when switching between Speaker 1 and 2.

 

[Kal Rubinson]

Measuring across the B&W DM601 high-frequency binding posts yielded 4.1Ω. Same when measuring the same posts through the switch. Both loudspeakers in the pair measured the same 4.1Ω. When I switched between Speaker 1-Left and Speaker 2-Left, and I measured across Amp A-Left. The digital ohm meter stayed at 4.1Ω. The meter does not react quick at all. Occasionally, I'd catch a 4.2Ω or 5.1Ω , but for the most part, it stayed at 4.1Ω at the Amp posts when switching between Speaker 1 and 2.

Thanks but I am confused. I want to know what an amp sees when it is not selected. Also, I want to know what a speaker sees when it is not selected. Thanks.

 

[vkhong]

I want to know what an amp sees when it is not selected..

390 kΩ

Also, I want to know what a speaker sees when it is not selected. Thanks.

No continuity or ∞ Ω

 

[RichB]

Duok Audio VU3 (100W max per channel due to VU meter max position)
Dual Analog VU Meter 2-Way Amplifier/Speaker Audio Switcher Box
AC 250V 5A large current relay, micro-USB 5VDC power source, remote controller included

I am curious as to any measurable degradation when quality relays are in use. My collection of loudspeakers is growing and am looking for an easy way to switch between loudspeaker pairs. Amplifiers: Bob Carver Crimson 275, B&K ST-140. Loudspeakers: Klipsch KLF-30, Paradigm Studio 100 v3/ Studio 20 v3 / Monitor 11 v2, 7se Mk II, and B&O Beovox RL140.

View attachment 147276
View attachment 147277

This device looks very cool. I am using this switch which is break-than-make and does not use a common ground:
audio switcher amplifier speaker switch converter 2 input 1 output/ 1 in 2 out 2 | eBay

I measured this with an voltmeter and the ground are separated.
They offer another version for tube amps that require a load.

It would be nice to get it measured.

- Rich

 

[restorer-john]

Testing from the amp site, the speaker switch seems to break then make.

Relays are used so it will be break before make and DPDT (no common ground). There are also two large resistors which look like 1K 10W wirewounds. Perhaps for some kind of loading.

As it's running from 5V and the relays are 5V coil ratings, unless there is a DC-DC converter on board, the relays will be getting less than 5V (loss over switching transistors) and may not be pulling in hard enough to achieve their 5A rating. We need to see more shots of the interior.

 

[vkhong]

Relays are used so it will be break before make and DPDT (no common ground). There are also two large resistors which look like 1K 10W wirewounds. Perhaps for some kind of loading.

Single-pole, double-pole, single-throw, and double-throw. Learned something new, thanks!

SPST, SPDT, DPST, and DPDT Explained

 

[vkhong]

@Kal Rubinson

After using it for a few weeks, my impressions are:
- No discernible loss in sound quality (vs direct wire to loudspeakers)
- When the amplifier is selected on the switcher, the amp sees the loudspeaker resistance, or 664 Ω if no loudspeaker is connected to the switcher
- When the amplifier is de-selected on the switcher, the amp sees 390 Ω

I have not switched loudspeakers on the fly. I power down all connected amplifier before any amp or loudspeaker switching.

Per the manufacturer:
Amplifier type supported: all kinds of type (BTL /Class A /Class AB /Class B / Class D digital amp / tube amp etc.)

Do you think it is safe to use as long as switching is done with amplifier powered down, solid-state or tube?

 

[Rick Sykora]

See Amir’s review… https://www.audiosciencereview.com/forum/index.php?threads/douk-vu3-review-vu-meters.26827/

 

[escksu]

See Amir’s review… https://www.audiosciencereview.com/forum/index.php?threads/douk-vu3-review-vu-meters.26827/

Looking at the measurements vs OP's observation. Perhaps we can say there is some minor but likely inaudible degration.

 

[jcgriff]

Is there a switch that anyone recommends that is set up correctly so as not to damage anything nor impact SQ adversely? I don't care about meters, I want to switch 2 amps, a SS and a tube, with 2-4 sets of speakers. OSD has some stuff but I don't think they have any impedance protection.