Rumski Forum - HITNO! BIG KNOB ili SPL 2381

evo nekih kritika

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The machine isn't flat/neutral. I'm running exactly the same sources and cables into it as I used before, and the sound is now less bright. But it sounds OK.

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I guess another possible reason for the changed sound is that the SPL is loading the impedence differently on the inputs and/or outputs. But I don't know about such things, so I'm guessing.

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I just got my SPL monitor controller today! Yes, the volume is stepped, but the markings are in %, and the manual doesn't say what the db diffference is from step to step.

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I wanted to follow up on this, now that I've had a little more time with this box. The attenuated frequencies appear to be around 2k-5k (judging by my ears, which are NOT calibrated to SI). The specs in the manual say frequency response is 10hz-100khz, +/- 3db.
3db!!!!

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chose this unit over the Big Knob because I expected better sound. I chose it over the Coleman because it has a more complete feature set. But sound quality must come first.

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all switches (source and speaker selection, talkback) produce little clicks and pops when operated. The source selector on my Digi Command 8, which this unit was meant to improve on, doesn't even do that. I also had to turn the input sensitivity on my Adam S3A's way down to get an acceptable travel on the volume pot, otherwise my max listening volume would be around less then an inch of the pots travel. I find this odd: this is supposed to be a fully passive unit, yet it's output is considerably higher compared to my D/A interface hooked up straight to my speakers

Ovo su bile kritike korisnika ....... aonda se javio covek iz SPL a i rekao

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Hi all,
we think we can clear up the discussion a bit. I?ll try to collect answers to all the questions that came up here, please get back if there are more questions or if I overlooked something ?
In general: the MTC is not an entirely passive unit, and we never said so.
A passive volume control would affect impedances. Changing the volume would mean you change the frequency response. Passive balancing I/O stages would require transformers. You probably can imagine what a price the MTC would have and what a huge box it would be ... Or, for example, the +10dB boost of the RCA inputs would be impossible and A/B comparisons i. e. of CD and DAW signals would not be that easy ?
Passive concepts are hyped due to their theoretical advantages, but: every box with a power supply is not entirely passive. When it comes to functionality, you rarely have the chance to exclude active circuits.
1) Frequency Response (Dip/Attenuation)
Buzz is right: +/- 3dB of course is nonsense. The correct spec would be 10Hz-100kHz (-3dB), representing at which corner frequencies the measurement detects a fall-off of -3dB. This means the curve is flat way up (we are just preparing precise measurements of a serial unit). It?s been a typing error from the editor, not a confused engineer. We?ll change the manual immediately.
We?ll put a fresh MTC2381 from the production on the bench and will publish our measurements here so that you can see that the MTC does not attenuate high frequencies.
A frequency dip (at around 2-5kHz) would require a sort of band-pass or EQ filtering, but this is not likely to happen in the MTC. Impedance problems would cut high frequencies like a low-pass filter, thus show another effect than described here.
We think you surely hear the sound of the MTC, the cables used for connections etc., just like with any unit compared to flat wiring ? as soon as you put some electronics in between, you will notice a change. So any controller, any other cable will have its effect.
We had some good quotes on the MTC from other users who compared it to the (comparable) competition, and our own impression also is that the MTC has its strengths in sound quality and functionality. We certainly did not observe sound deviations that could be compared to a 3dB high frequency attenuation, from there, Onan, we will be glad to help you analyze your specific situation. Just give us a call or send us an e-mail.
2) Audible clicks when switching
This is a good example of what we did to keep a high signal quality level:
We use hard-switching here instead of soft-switching CMOS components (CMOS tend to produce more distortions). With DC potential coming from external units or internal op-amps, you inevitably hear clicks with hard-switching or one alternatively has to put in trimming circuits that again add side-effects. We could reduce it to an acceptable level using shorting switches and selected op-amps, but a little click remains. We only noticed this with the Speaker On and the Headphone On switches. Since sound quality was our priority, we decided to use hard-switching ? and fight these battles with customers :) to explain it was the best compromise between signal quality and functionality.
TIP: The faster you move the switches, the less is audible.
3) Monitor Volume
Input levels of monitors and power amps vary in wide ranges, so it is difficult to find an ideal compromise. We decided to give the Monitor Volume control a +10dB boost (unity gain is around 2 o?clock), as it is better to reduce the input sensitivity of ?loud? monitors than hearing quiet signals not loud enough on ?quiet? speakers. Because there is no problem to reduce the input level on monitors or power amps as that is what input level controls are made for while on the other hand there would be no way to touch up in the opposite direction.
4) Monitor Volume Control Scale
A dB scale of a Volume Control should ideally represent the sound pressure level in the control room. How should we know?
The scale on the MTC allows to put your own marks for your preferred listening levels ? you should use an sound pressure level meter at your listening postion and move the Volume Control until the desired level is reached. Mark the position and the SPL value on the scale and you?re done.
Other dB scales (e. g. +10 to ?80dB) represent line levels and not the SPL dB values in the control room. We opted for the percentage scale to avoid confusion with line level and SPL dB scales.
I hope to have clarified this case a bit and will be posting the measurements asap.
Everyone and especially owners of the MTC in case of further questions are invited to contact us directly for support and answers to their possible questions.