Solupeak RC-11 Review (Passive Volume Control)

[amirm]

This is a review and detailed measurements of the SOLUPEAK RC-11 passive volume control. It was kindly drop shipped to me by a member and costs US $17.

As you see, this comes in a nice little aluminum enclosure as opposed to the typical plastic post. This should help with interference. Being passive, the back just has the requisite RCA jacks:

SOLUPEAK RC-11 Measurements
I fed the unit 2 volts and set its volume to max:

This is the same performance as not having the unit. So if you don't attenuate, it is transparent. I dropped the level by 10 dB and performance hovered around 112 dB so even then, results are very good.

I was pleasantly surprised that impact on frequency response was negligible:

Crosstalk is good for the class:

Finally, channel matching was good as as well:

As usual, your mileage may vary.

Conclusions
Compared to the last passive volume control I reviewed (LC-1), the RC-11 performs much better. It also comes in a much more home stereo packaging. And without RCA cables to break, it is likely more reliable as well. As I result, I am happy to put RC-11 on my recommended list should you find yourself in need of a passive volume control.

---------
As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/

 

[JSmith]

$17 and transparent... nice! Thanks for testing.


JSmith

 

[respice finem]

Fine. Simple, straightforward, affordable.

 

[Ra1zel]

Wonder how will frequency response look like with 2 meter cable

 

[Peternz]

Output impedance? Input impedance? Does it kill the dynamics by not being able to drive downstream components properly? This stuff does actually matter. I have used active and passive preamps and I prefer active all day every day.

 

[amirm]

Wonder how will frequency response look like with 2 meter cable

The input to it was a 2 meter cable, output about 1 meter.

 

[Blumlein 88]

Output impedance? Input impedance? Does it kill the dynamics by not being able to drive downstream components properly? This stuff does actually matter. I have used active and passive preamps and I prefer active all day every day.

He said 9.1 kohm pot so that should be the input impedance. Output will vary with volume level chosen. Should be a max output impedance of 2275 ohms or so at - 6db and less at any other setting.

 

[Loathecliff]

At last! The perfect ampli ...... Oh damn

 

[restorer-john]

The input impedance of the AP is 100k along with a wide bandwidth.

A typical power amp will be ~25k with significant capacitance and various RC filters. The frequency response when driving a typical real world amplifier will not be remotely flat at typical volume positions (attenutated).

 

[DSJR]

Can that be simulated by somebody please? Some power amps don't mind, but others react badly to being 'fed' that way...

I worked with a passive 'preamp' (pot in a box with input switching) and at first, the pots were 47k log, later reduced to 10k log (the sound 'seemed' toppier with the 10k pot, but that's subjective and not properly verified). The power amps they were used with had high sensitivity inputs (it was claimed the 'line buffer' was put on the amp input instead of in the preamp) and input sensitivity was also claimed to be around 47k

 

[miero]

AP settings: output impedance 20 Ohm and input impedance 100 kOhm.

Might not work so well with all devices.

@amirm Could you retest it with 100 Ohm output and 20 kOhm input please?

 

[amirm]

@amirm Could you retest it with 100 Ohm output and 20 kOhm input please?

Test what?

Folks, these are passive volume controls and should be used as a last resort. They will have negative consequences which you can compute yourself based on gear you have. I am doing a quick test with a fixed setup. I can't emulate any and all systems out there.

 

[Blumlein 88]

Can that be simulated by somebody please? Some power amps don't mind, but others react badly to being 'fed' that way...

I worked with a passive 'preamp' (pot in a box with input switching) and at first, the pots were 47k log, later reduced to 10k log (the sound 'seemed' toppier with the 10k pot, but that's subjective and not properly verified). The power amps they were used with had high sensitivity inputs (it was claimed the 'line buffer' was put on the amp input instead of in the preamp) and input sensitivity was also claimed to be around 47k

A big part would be length and parallel capacitance of the cable on the output. Best to keep those as short as possible, and use low capacitance cables. Input of the amp will have some effect too.

Still in general with short cables on the output, and an input impedance of 47 k ohms or more it shouldn't be too weird. Might result in a little softening of the treble with some amps.

 

[Peternz]

This can be the best thing in the world since sliced bread but at the end of the day it has to work in a system and it has to sound good at any volume setting you wish to use. I have had a few and some have been arguably better than the item discussed here but I have never been satisfied. I am using a Topping Pre90 now and I could not be happier...

A discussion

Passive and active preamp - benefits/losses?

Hello all! I had an issue recently with my tube pre-amp and sent it for repair, so in the mean time I've got a passive preamp to fill the gap...

forums.stevehoffman.tv

 

[jasonhanjk]

A 2V line that attenuate 10dB and feed to an amp with 20dB gain; with 8 ohm load the power would be 5W.

 

[Rja4000]

Thanks for this

Stupid question maybe : Is there any higher voltage limit for those ?
I mean: Is THD or IMD increasing suddenly when you push more Volts at the input, as when an amp is saturating ?

 

[Blumlein 88]

Thanks for this

Stupid question maybe : Is there any higher voltage limit for those ?
I mean: Is THD or IMD increasing suddenly when you push more Volts at the input, as when an amp is saturating ?

Effectively no.

 

[Rja4000]

Out of curiosity, I've done some measurements with my Radial Engineering SAT-2
RME ADI-2 Pro fs R Mono is used for measurement

Here is the SINAD at -10dB "Gain"

Here is the bandwidth at 768kHz sampling rate, still at -10dB"gain"
(Grey is the RME for reference)
That's -0.8dB at 20kHz (ref = 1kHz)

EDIT:
An updated version of the Frequency Response, for different SAT-2 Levels

Blue is now the RME loopback at 192kHz (SD Sharp filter)
Red is with SAT-2 at Max level. (It's also very similar at 9 o'clock)
Black is with SAT-2 at 12 o'clock level (worst case scenario)

Warning: Scale is +/- 1 dB
That's quite zoomed in !

(Test signal is REW Perodic Noise 192kHz, 128k FFT size)

l

 

[Rja4000]

Effectively no.

Shouldn't be any saturation, indeed.

I can push 19V in the SAT-2 without any hint of added distortion...

 

[anphex]

Out of curiosity, I've done some measurements with my Radial Engineering SAT-2
RME ADI-2 Pro fs R Mono is used for measurement

Here is the SINAD at -10dB "Gain"

View attachment 210522

Here is the bandwidth at 768kHz sampling rate, still at -10dB"gain"
(Grey is the RME for reference)
That's -0.8dB at 20kHz (ref = 1kHz)

View attachment 210524

I was shoked for a second, then I saw the dB scale on the left
So basically, this thing is about high end worthy when your amp has too much sensivity/gain - as a last resort for attenuation.

Oh, and wanna have a laugh? I wanted to see a measurement of this thing because I thought of getting one for "throttling" the input to my Hypex amps to match the Topping PA5 with about 10dB less gain, but now I see this thing isn't really available in Germany.