Hello Everyone,
This a review and detailed measurements of the Rotel RC-03 Preamplifier.
After the reviews of the staggering Accuphase C-280 and the high-end Denon PRA-S10, I was interested to review a much lower end similar device, and here we go.
Rotel RC-03 - Presentation
This preamplifier was available from 2002 to 2005, and it was the entry line of Rotel, as a pure preamplifier, at around 500€. As you can see, the design is simple and the functionalities are limited. Yet, we get a phones and out and phono stage (MM only) but no subsonic filter, tsk tsk tsk.
The back is equally simple:
And again we get more than the essential with two outputs and couple of triggers, for two stereo amplifiers?
The specs provided by Rotel were the below:
Of course I'll check if there are met.
Let's have a quick look at the inside:
The phono card:
Phones out:
User experience
Not much to say, really. There can hardly be a more simple / easy to use HiFi device. The volume knob is precise and silent per my experience and measurements. Touch and feel are higher end than the price, so that's good.
If I enjoyed the presence of the phones out, I'm always unhappy with phono stages without a subsonic filter. So you have to hope that the power amplifier has one...
Rotel RC-03 - Measurements (Line)
All measurements were performed with an E1DA Cosmos ADCiso (grade 0), and the Cosmos Scaler (100kohms from unbalanced input), for capturing analog outputs of the preamp. I used a high performance DAC, the Topping D50III, as the generator with REW Software from a laptop. All these devices run on batteries, and the D50III was behind a USB isolator, to prevent as much as possible any ground loops.
I won't be necessarily following Amir's way of measuring such an item because I don't use an AP, and my main goal is to check and compare the claims of the vendor. So you can't directly compare to Amir's measurements, although it's not completely deviating. All that said, you'll be able to compare the below measurements with those I performed with the Accuphase and the Denon.
All measurements are from RCA outputs, of coures. The two channels match a 0.1dB in the worst case scenario, which is good. Phase is flat.
Since the Rotel is rated for 150mV input and 1V output, let's see if we get more or less than the claimed 0.004% of THD+N:
Yes, that's better, although we don't reach the 16bits of resolution, due to noise. And this very close to the much bigger, way more expensive Denon PRA-S10. You can see that the distortion is very low with that 16dB gain applied. And again 0.004% as per specs, and 0.0014% measured after 20 years of service (the previous owner used it every day).
Now like I did with the two others, this is with 500mVrms input:
That is the confort zone of this Rotel and the max resolution we can get of it. The Denon was doing almost 1bit better in this test. That said, a SINAD of 105dB is more than decent.
For compatibility with Amir's review, this is the same same test with 2Vrms input and same at the output, meaning unity gain:
Ah, here the Rotel takes the lead over the Denon, by half a bit. The reason is that the Rotel has a better management of the noise floor at unity gain.
Like I did with the Denon, this is again 2Vrms in/out (unity gain) but with the noise included up to 90kHz:
The Rotel does not suffer the issue I spotted with ultrasonic noise, as I saw it with the Denon. You can go check, and so this time the Rotel wins again by 1.6bits!
All of what you saw above and what I measured is above the specs of Rotel, good news, right?
----
I guess you saw some power supply related leakage from mains (50Hz in Europe), and I like to show it "à la" Stereophile:
The two channels are shown, right one have a little more leakage, but at below -120dBr, no way you can hear that.
----
Let's continue with the famous Multitone that a lot of you, including me, like so much, here at unity gain:
And the below is the same test, but using the AudioPrecision's test file instead of REW's generator (one more tone at low frequency):
In both cases, we get more than 19bits distortion free range, very good.
And since I showed that Multitone a max gain with the Denon let me overlay unity gain and max gain:
At max gain, we are very close to 20bits distortion free range, excellent!
----
Let's move on to bandwidth:
That is what I call flat! And despite the zooming! Nice, and it helps not having tones control...
----
Oh, yes, another measurement that you can use to compare with other devices. It is the THD+N ratio vs frequency, with an extended bandwidth to capture all distortion and noise components up to 90kHz:
Left and right channels have nearly the same performances, all limited by noise. No rise of distortion at high frequencies, that is a well behaved little preamp.
----
The below IMD SMPTE sweep vs input level is not comparable to the same test from Amir, because it is excluding noise:
Comfort zone is from 500mV to 1Vrms input at unity or max gain. The plot show the total distortion at 1V, and being at -100dBr, that will remain easily hidden to your ears. These results are better than those of the Denon PRA-S10 which suffered from higher distortion at unity gain.
----
Other measurements (not shown):
The above are a very good set of measurements for an entry level preamplifier.
Rotel RC-03 - Measurements (Phono MM)
If I bought that little preamp at the time, it's because it has a phono input and I was curious to test what this one could deliver, especially when compared to vintage master class preamplifiers who were the king of that exercise, once upon a time. See the Accuphase C-280 review to understand what I mean.
Ok, let's start with the 1kHz test tone @40mVrms with 40dB gain:
Oh, wait a minute, this is so close to Sir Accuphase! Nearly 15bits of resolution for the black polyvinyl chloride disc? Oh well, nothing will come in the way of the best master, in that case... This is very nice.
And if I perform the same measurement but compensate for the RIAA curv(s)e, like I did for the Accuphase review, then...
Come on, this is 1bit more resolution than what the Accuphase had to offer. Little insolent thing.
Note: Why 40mVrms input when Amir uses 5Vrms for this test? For two reasons:
----
Next important set of measurements for a phono preamp is related to knowing at what point it will clip, depending on the frequency and voltage input. We need a good headroom, and all ancient phono preamps were known to perform well on that perspective. Let's see what the much younger one can deliver.
This is measured with a sweep of THD vs input level, at different frequencies:
Ah, I can finally say poor little thing. We don't have much headroom here. At 1kHz, it will clip beyond 60mVrms. So that means, as per my note above (and that's also the reason why I put it before), that we don't have any headroom here, while the old blokes mastered this exercise.
I am also surprised because Rotel specs say 160mV is the overload point and that should be at 1kHz (although not specified). So I wonder... a bit tired?
Since the above measurements were at 40dB gain, I tried the same at a lower 20dB gain (at 1kHz) and got the same results:
All that said, it should be enough. But I'm afraid that, and because there's no subsonic filter, we could get clipping at very low frequencies.
----
Ok, bandwidth, as we need to check the respect of RIAA curve:
Right and Left channels are shown with their 0.1dB difference. Other than that, the RIAA curve is within 0.1dB, this is very good.
----
Oh, yes, for the fun, as @amirm likes the below measurement. It is a sweep of THD only (no noise) with an extended bandwidth up to 90kHz to capture distortion at high frequencies too. I overlaid three sweeps, with 5mVrsm input (40dB gain and 52dB gain) and 10mVrms (40dB gain):
I could not test at low frequencies in two cases, because of the clipping. Other than that this is very good distortion performances.
----
Besides the input voltage limitation, this is a very good phono preamplifier missing a subsonic filter.
Conclusion
This little preamp can be found for a very low price, and it delivers.
Overall, the distortion is very low, and only a little low level random noise, below the one of the CD Audio, can be seen and limits the performances.
I have some concerns about the too rapid clipping of the phono preamp section, especially without subsonic filter in the lowest frequencies, but maybe I'm over cautious? Or maybe Rotel was smart enough to leave that to the bigger brothers? I might be interested to know...
Anyways, I've been writing this review with the Rotel driving my too big Accuphase amplifier, feeding two very hungry B&W speakers.
Supertramp - Crime of the century was the album of choice to accompany this write up, a portal to a distant time. I’m back in that smoke-filled living room, my parents laughing with friends as a grey haze of cigarette smoke lazily drifts mid-air. I’m a child again, hidden under the dining table, lost in a world of toys, while that masterpiece spins its magic...
What does that mean? Straight wire with gain, transparency, and time travel
This is what music is about, and that preamp knows how to sing.
I hope your enjoyed this review and I wish you a happy weekend!
Flo
This a review and detailed measurements of the Rotel RC-03 Preamplifier.
After the reviews of the staggering Accuphase C-280 and the high-end Denon PRA-S10, I was interested to review a much lower end similar device, and here we go.
Rotel RC-03 - Presentation
This preamplifier was available from 2002 to 2005, and it was the entry line of Rotel, as a pure preamplifier, at around 500€. As you can see, the design is simple and the functionalities are limited. Yet, we get a phones and out and phono stage (MM only) but no subsonic filter, tsk tsk tsk.
The back is equally simple:
And again we get more than the essential with two outputs and couple of triggers, for two stereo amplifiers?
The specs provided by Rotel were the below:
Of course I'll check if there are met.
Let's have a quick look at the inside:
The phono card:
Phones out:
User experience
Not much to say, really. There can hardly be a more simple / easy to use HiFi device. The volume knob is precise and silent per my experience and measurements. Touch and feel are higher end than the price, so that's good.
If I enjoyed the presence of the phones out, I'm always unhappy with phono stages without a subsonic filter. So you have to hope that the power amplifier has one...
Rotel RC-03 - Measurements (Line)
All measurements were performed with an E1DA Cosmos ADCiso (grade 0), and the Cosmos Scaler (100kohms from unbalanced input), for capturing analog outputs of the preamp. I used a high performance DAC, the Topping D50III, as the generator with REW Software from a laptop. All these devices run on batteries, and the D50III was behind a USB isolator, to prevent as much as possible any ground loops.
I won't be necessarily following Amir's way of measuring such an item because I don't use an AP, and my main goal is to check and compare the claims of the vendor. So you can't directly compare to Amir's measurements, although it's not completely deviating. All that said, you'll be able to compare the below measurements with those I performed with the Accuphase and the Denon.
All measurements are from RCA outputs, of coures. The two channels match a 0.1dB in the worst case scenario, which is good. Phase is flat.
Since the Rotel is rated for 150mV input and 1V output, let's see if we get more or less than the claimed 0.004% of THD+N:
Yes, that's better, although we don't reach the 16bits of resolution, due to noise. And this very close to the much bigger, way more expensive Denon PRA-S10. You can see that the distortion is very low with that 16dB gain applied. And again 0.004% as per specs, and 0.0014% measured after 20 years of service (the previous owner used it every day).
Now like I did with the two others, this is with 500mVrms input:
That is the confort zone of this Rotel and the max resolution we can get of it. The Denon was doing almost 1bit better in this test. That said, a SINAD of 105dB is more than decent.
For compatibility with Amir's review, this is the same same test with 2Vrms input and same at the output, meaning unity gain:
Ah, here the Rotel takes the lead over the Denon, by half a bit. The reason is that the Rotel has a better management of the noise floor at unity gain.
Like I did with the Denon, this is again 2Vrms in/out (unity gain) but with the noise included up to 90kHz:
The Rotel does not suffer the issue I spotted with ultrasonic noise, as I saw it with the Denon. You can go check, and so this time the Rotel wins again by 1.6bits!
All of what you saw above and what I measured is above the specs of Rotel, good news, right?
----
I guess you saw some power supply related leakage from mains (50Hz in Europe), and I like to show it "à la" Stereophile:
The two channels are shown, right one have a little more leakage, but at below -120dBr, no way you can hear that.
----
Let's continue with the famous Multitone that a lot of you, including me, like so much, here at unity gain:
And the below is the same test, but using the AudioPrecision's test file instead of REW's generator (one more tone at low frequency):
In both cases, we get more than 19bits distortion free range, very good.
And since I showed that Multitone a max gain with the Denon let me overlay unity gain and max gain:
At max gain, we are very close to 20bits distortion free range, excellent!
----
Let's move on to bandwidth:
That is what I call flat! And despite the zooming! Nice, and it helps not having tones control...
----
Oh, yes, another measurement that you can use to compare with other devices. It is the THD+N ratio vs frequency, with an extended bandwidth to capture all distortion and noise components up to 90kHz:
Left and right channels have nearly the same performances, all limited by noise. No rise of distortion at high frequencies, that is a well behaved little preamp.
----
The below IMD SMPTE sweep vs input level is not comparable to the same test from Amir, because it is excluding noise:
Comfort zone is from 500mV to 1Vrms input at unity or max gain. The plot show the total distortion at 1V, and being at -100dBr, that will remain easily hidden to your ears. These results are better than those of the Denon PRA-S10 which suffered from higher distortion at unity gain.
----
Other measurements (not shown):
- Input voltage clipping: xxVrms (I forgot to measure, but certainly much higher than 2.5Vrms!)
- Output voltage clipping: 7.8Vrms
- Dynamic Range: 103.1dB (CCIR 2k weighted) or 107dB(A) at unity gain
- IMD AES (18kHz + 20kHz 1:1) : -98dB
The above are a very good set of measurements for an entry level preamplifier.
Rotel RC-03 - Measurements (Phono MM)
If I bought that little preamp at the time, it's because it has a phono input and I was curious to test what this one could deliver, especially when compared to vintage master class preamplifiers who were the king of that exercise, once upon a time. See the Accuphase C-280 review to understand what I mean.
Ok, let's start with the 1kHz test tone @40mVrms with 40dB gain:
Oh, wait a minute, this is so close to Sir Accuphase! Nearly 15bits of resolution for the black polyvinyl chloride disc? Oh well, nothing will come in the way of the best master, in that case... This is very nice.
And if I perform the same measurement but compensate for the RIAA curv(s)e, like I did for the Accuphase review, then...
Come on, this is 1bit more resolution than what the Accuphase had to offer. Little insolent thing.
Note: Why 40mVrms input when Amir uses 5Vrms for this test? For two reasons:
- The Topping does not provide a good enough signal at 5mVrms, simple.
- Because some dynamic cartridges (eg: Shure M44-7 - 9mVrms for 5cm/sec), together with over-cut records, would be reaching a speed velocity of 30cm/sec, meaning they'd be at or beyond 60mVrms.
----
Next important set of measurements for a phono preamp is related to knowing at what point it will clip, depending on the frequency and voltage input. We need a good headroom, and all ancient phono preamps were known to perform well on that perspective. Let's see what the much younger one can deliver.
This is measured with a sweep of THD vs input level, at different frequencies:
Ah, I can finally say poor little thing. We don't have much headroom here. At 1kHz, it will clip beyond 60mVrms. So that means, as per my note above (and that's also the reason why I put it before), that we don't have any headroom here, while the old blokes mastered this exercise.
I am also surprised because Rotel specs say 160mV is the overload point and that should be at 1kHz (although not specified). So I wonder... a bit tired?
Since the above measurements were at 40dB gain, I tried the same at a lower 20dB gain (at 1kHz) and got the same results:
All that said, it should be enough. But I'm afraid that, and because there's no subsonic filter, we could get clipping at very low frequencies.
----
Ok, bandwidth, as we need to check the respect of RIAA curve:
Right and Left channels are shown with their 0.1dB difference. Other than that, the RIAA curve is within 0.1dB, this is very good.
----
Oh, yes, for the fun, as @amirm likes the below measurement. It is a sweep of THD only (no noise) with an extended bandwidth up to 90kHz to capture distortion at high frequencies too. I overlaid three sweeps, with 5mVrsm input (40dB gain and 52dB gain) and 10mVrms (40dB gain):
I could not test at low frequencies in two cases, because of the clipping. Other than that this is very good distortion performances.
----
Besides the input voltage limitation, this is a very good phono preamplifier missing a subsonic filter.
Conclusion
This little preamp can be found for a very low price, and it delivers.
Overall, the distortion is very low, and only a little low level random noise, below the one of the CD Audio, can be seen and limits the performances.
I have some concerns about the too rapid clipping of the phono preamp section, especially without subsonic filter in the lowest frequencies, but maybe I'm over cautious? Or maybe Rotel was smart enough to leave that to the bigger brothers? I might be interested to know...
Anyways, I've been writing this review with the Rotel driving my too big Accuphase amplifier, feeding two very hungry B&W speakers.
Supertramp - Crime of the century was the album of choice to accompany this write up, a portal to a distant time. I’m back in that smoke-filled living room, my parents laughing with friends as a grey haze of cigarette smoke lazily drifts mid-air. I’m a child again, hidden under the dining table, lost in a world of toys, while that masterpiece spins its magic...
What does that mean? Straight wire with gain, transparency, and time travel
This is what music is about, and that preamp knows how to sing.I hope your enjoyed this review and I wish you a happy weekend!
Flo
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