Rotel RB-1070 Amplifier Review

[restorer-john]

- gain appears awfully low - (1 k + 560) / 560 so about 3x.

Feedback resistor is 18k, not 1k. So about 30dB.

 

[pma]

Yes. Gain is 1 + 18k/560.
Capacitor VAS loading is not optimal.
The circuit is only visually symmetrical, there are many ways to get even order distortion - like supply rail induced distortion.

https://www.eetimes.com/distortion-in-power-amplifiers-part-vi-the-remaining-distortions/

Look at Fig.7

 

[Tangband]

Most high end amps back then performed similarly or even worse than this one, but look at the distortion pattern - audibly harmless second harmonic with odd orders above that well down and subsequent harmonics declining in a straight line to 20k and no doubt beyond! I bet it's a heck of a lot 'cleaner' at supersonic frequencies too than the new wave of wonder-whizz-boxes this site wets itself over? Got to say I like the seemingly simple and symmetrical circuits used there which should be easy to maintain I suspect.

Rotel amps always 'sounded' just fine in a domestic system but kind of got themselves a 'mid price' reputation over here, so would be largely ignored by the 'high end badge collectors' of which there are still a goodly few I think.

Thanks for reviewing this - should help for people after a good used solid buy. That Audiophonics amp with graphs shown above is many multiples of the expected price of this Rotel currently and let's be absolutely honest, that Topping dinky-box is hardly in the same *usage* ballpark now, is it as I'd suggest it's more for basic small desktop systems really?

Yes, the reputation of Rotel was a mid price reputation. Not only that - cheaper Rotels were considered better sounding than the more expensive ones in the Linn stores.

Subjective statements :
Their more expensive models were outperformed by a naim nait 1 ( 15 Watts ) or even their own cheaper amplifier like the Rotel 810 for 100 dollars. Even with big speakers like Linn Isobarik the difference were obvious, if playing music at sensible levels .

Nowadays, the same is happening with a tpa 3251 based amplifier if compared to yesterdays dinosaurs. Three years ago, I bought a Aiyima a04 with a meanwell 32V 8A psu, and after extensive listening sessions a couple of days together with other people on average listening levels, I sold my three class A/B amplifiers and bought two more Aiyima .

My most powerful amp , rated at 500 Watts ( Crown xli1500 ) sounded worse of them all- the music didnt come to life, and the perceived pitch of each note the musicians were playing wasnt as clear as with the tpa 3251 based Aiyima . The bass was clearly better defined with a more exact perceived pitch of each note the bass player played when listening to the Aiyima a04. That made the music more fun to listen to.

So there is no real news even at 2023 - amplifiers sounds slightly different and there are some differences in the articulation when playing real music , especially in the bass . With normal volume levels using two loudspeakers in a smaller room, there are also other qualities than raw power specs that matters.

 

[Deleted member 48726]

Yes, the reputation of Rotel was a mid price reputation.

Subjective statements :
Their more expensive models were outperformed by a naim nait 1 ( 15 Watts ) or even their own cheaper amplifier like the Rotel 810 for 100 dollars. Even with big speakers like Linn Isobarik the difference were obvious, if playing music at sensible levels .

Nowadays, the same is happening with a tpa 3251 based amplifier if compared to yesterdays dinosaurs. Three years ago, I bought a Aiyima a04 with a meanwell 32V 8A psu, and after extensive listening sessions a couple of days together with other people on average listening levels, I sold my three class A/B amplifiers and bought two more Aiyima .

My most powerful amp , rated at 500 Watts ( Crown xli1500 ) sounded worse of them all- the music didnt come to life, and the perceived pitch of each note the musicians were playing wasnt as clear as with the tpa 3251 based Aiyima . The bass was clearly better delfined with more exact perceived pitch of each note the bass player played when listening to the Aiyima a04.

So there is no real news even at 2023 - amplifiers sounds slightly different and there are some differences in the articulation when playing real music , especially in the bass . With normal volume levels using two loudspeakers in a smaller room, there are also other qualities than raw power specs that matters.

Which speakers are / were you using with these mentioned amplifiers?

 

[Tangband]

Which speakers are / were you using with these mentioned amplifiers?

Passive jbl 530.
( nowadays I use Genelec 8340 with class D ).

 

[Deleted member 48726]

Passive jbl 530.
( nowadays I use Genelec 8340 with class D ).

Looks like it could be a challenge for some amplifiers IR to the tested phase, impedance and sensitivity. Could be why you heard a difference.

JBL Studio 530 Speaker Review

This is a review and detailed measurements of the JBL Studio 530 bookshelf speaker. They normally cost US $600 but routinely go on sale. That is how I purchased mine for US $280 direct from JBL. The 530 has a very unique style of its own: I normally take speaker grills off for...

www.audiosciencereview.com

 

[restorer-john]

Passive jbl 530.
( nowadays I use Genelec 8340 with class D ).

Let's start a separate thread to discuss this? The review thread of the Rotel RB-1070 will get dragged off track otherwise.

 

[Tangband]

Let's start a separate thread to discuss this? The review thread of the Rotel RB-1070 will get dragged off track otherwise.

Sorry for the story off topic - now back to discuss Rotel.

 

[ranrt]

Hi Amir, I wish if you could , maybe some day do the same test on ADCOM GFA 555ll or see comparison against the Rotel. Thanks

 

[capslock]

Yes. Gain is 1 + 18k/560.
Capacitor VAS loading is not optimal.
The circuit is only visually symmetrical, there are many ways to get even order distortion - like supply rail induced distortion.

https://www.eetimes.com/distortion-in-power-amplifiers-part-vi-the-remaining-distortions/

Look at Fig.7

You are right, I misread the value due to the typeface used.

I still don't see how supply reil induced distortion would be independent of drive level.

 

[My adventures in stereo]

Good to see Rotel reviewed here, looks like good value for money
Would love to see some similar Parasound amps reviewed here

 

[pma]

I still don't see how supply reil induced distortion would be independent of drive level.

I agree that it is a bit like guessing from a crystal bowl. However, I do understand that THD+N vs. frequency may be power and frequency independent and I have such example in one of my amplifier designs (below). Measuring BW is 45kHz. Here the key is the frequency compensation (of FB loop) used.

 

[Brambo67]

This is a review and detailed measurements of the Rotel RB-1070 stereo power amplifier. It was released in early 2000. Can't find the cost then but I see it used for around $400 to $500.
View attachment 258672
I have always found Rotels to be most attractively designed power amplifiers. One look at that front panel and you immediately think of muscle and beauty in design. Alas, the extruded aluminum in front which gives it that look, is cosmetic. There are two others internally which do the job of cooling this classic AB design. In use the heastsinks got pretty warm to touch to give it some air to breath.

Not much news in the back other than nice inclusion of trigger input/output:
View attachment 258673

Rotel RB-1070 Measurements
The unit warmed up nicely without its performance changing much:
View attachment 258674

So let's see what our dashboard of 1 kHz tone does into 4 ohm load:

View attachment 258675
The amp is about 2 dB more sensitive than usual which likely accentuates the power supply noise a bit. I was able to reduce 60 Hz hum in one channel but not simultaneously in the other. That is exceeded however by the power supply noise at 120 Hz and multiples. SINAD is likely dominated by distortion to the tune of -80 dB. This lands the RB-1070 slightly above average of all amplifiers tested:
View attachment 258676

Despite the power supply noise, dynamic range is very good:
View attachment 258677

Frequency response is excellent and spec compliant:
View attachment 258678

Crosstalk is good:
View attachment 258679

Multitone shows no frequency dependence which is nice:
View attachment 258680

There is ample power available into 4 ohm:
View attachment 258681

The response is quite odd in that it doesn't slope down. Don't know if that is intentional, accidental or due to power supply caps aging, letting in more ripple as power goes up.

Regardless, lots of power is available:
View attachment 258683

Company only specs the power into 8 ohm at 130 watts. It certainly delivers that:
View attachment 258684
Putting aside noise floor which is rather high, the units transfer function is one of the best I have ever seen:
View attachment 258685

Sadly there is a significant power on pop:
View attachment 258686

Conclusions
As one of my favorite (looking) brands, I was very anxious to measure a Rotel amp, hoping it would not let me down. Fortunately it did not. No, the SINAD doesn't break new ground but the rest of the measurements are very good with plenty of power available. It is a great choice for people wanting good amount of power in an attractive package with competent performance.

I am going to recommend (used) Rotel RB-1070.

----------
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/

So, the reviewer decides that 80 dB SINAD justifies a recommendation. I can’t see the justification. Of course a fifty year old guy running the 100 meters in 15 seconds does great. Would you consider lining him up in your relay team for the Olympics? I don’t think so… I don’t understand why everyone is hammering on SINAD score being the value most important to base judgement on and still saying; wow, nice score… I can’t help from seeing some biased recommending here. Please explain how this amp will help getting a great listening experience. Or is there some magic I’m not aware of? Imagine going through lengths to finally find that refurbished Denon AVC x3700h with AKM DAC’s, investing in proper cables and the best speakers, subscribing to TIDAL and deciding to get this amp to get your so desired 7.1.4 Atmos setup with driving your front left and right for the perfect stereo setup…. Only to find out through this review that, yes it is recommended, but also yes, it took your SINAD score down to making it useless for your lossless hires files to play.

Anyway, I still belief these measurements are great and wouldn’t hesitate one second to buy this 2nd hand myself as well, as these are widely available where I live and am more relaxed about SINAD. But I will not understand why it is recommended if it fails to run the 100 meters in, let’s say, about 10 seconds… And of course so many people cheering and not wondering what that fifty year guy was doing in the relay team even if he looked great and admired by the guy holding stopwatch….

 

[amirm]

So, the reviewer decides that 80 dB SINAD justifies a recommendation

The recommendation is due to 300 watts per channel for $350 from name brand company. I couldn't sell you its empty box for that much money!

 

[capslock]

I agree that it is a bit like guessing from a crystal bowl. However, I do understand that THD+N vs. frequency may be power and frequency independent and I have such example in one of my amplifier designs (below). Measuring BW is 45kHz. Here the key is the frequency compensation (of FB loop) used.

View attachment 259027

Very interesting indeed! Do you have any idea what drives THD+N in your case? Could it be very low THD and high N? It it was THD, one would expect a nonlinearity in the transfer function to be the root cause, and that is by defintion going to be level dependent.

 

[DSJR]

It is possible that some of you specialists will determine that an Audio Alchemy DAC-in-the-box can be bested by a current generation device costing almost nothing. What the hell does 'bested' mean?

From a review of the Audio Alchemy DAC-in-a-box from Gramophone way back in the old days of 2012: "Despite the increasing climate of opinion which denigrates audio measurements and points to their inability to predict or even correlate reliably with the sound quality as heard, I never regard technical testing as a waste of time. At some stage, therefore, before or after the admittedly more meaningful listening sessions, I like to check the makers' specification point by point. Without 'testing to destruction' I can often get a better feel for the unit's ability to stand up to rough handling and the quality of construction and electrical alignment than is possible from mere music listening. There is the added benefit that objective tests can be carried out to international standards on an individual unit in isolation, whereas 'listening' to an amplifier, for example, is only possible when a CD deck or other source and chosen loudspeakers are hooked up, with their own idiosyncrasies. Then there is the effect of the listening room..."

The review, Rachel Cramond is concerned about rough handling.

I believe it was tested in 'Gramophone' magazine some time back in the 90's? and the reviewer, also a recording engineer, found that the dac-in-a-box had an audible 'effect' on all recordings played through it compared to what I remember as his Sony PCM-F1 reference which made his masters and which I gather is still pretty good if outclassed technically now. My dealer pal sold dozens of these Audio Alchemy boxes though and back then, £200 was peanuts for a digital source.

 

[DSJR]

Yes, the reputation of Rotel was a mid price reputation. Not only that - cheaper Rotels were considered better sounding than the more expensive ones in the Linn stores.

Subjective statements :
Their more expensive models were outperformed by a naim nait 1 ( 15 Watts ) or even their own cheaper amplifier like the Rotel 810 for 100 dollars. Even with big speakers like Linn Isobarik the difference were obvious, if playing music at sensible levels .

Nowadays, the same is happening with a tpa 3251 based amplifier if compared to yesterdays dinosaurs. Three years ago, I bought a Aiyima a04 with a meanwell 32V 8A psu, and after extensive listening sessions a couple of days together with other people on average listening levels, I sold my three class A/B amplifiers and bought two more Aiyima .

My most powerful amp , rated at 500 Watts ( Crown xli1500 ) sounded worse of them all- the music didnt come to life, and the perceived pitch of each note the musicians were playing wasnt as clear as with the tpa 3251 based Aiyima . The bass was clearly better defined with a more exact perceived pitch of each note the bass player played when listening to the Aiyima a04. That made the music more fun to listen to.

So there is no real news even at 2023 - amplifiers sounds slightly different and there are some differences in the articulation when playing real music , especially in the bass . With normal volume levels using two loudspeakers in a smaller room, there are also other qualities than raw power specs that matters.

The trouble with dealers (myself for thirty plus years pretty much) is that most of 'us' have no tech background and 'only' our ears to judge. back in the 70's where measurements were still important, the better UK dealers sharing various top agencies, tended to share similar outlooks and opinions, but once subjectivism took over, every dealer 'audio consultant' had an independent view depending on the dem room acoustics and how an often sub-standard amp equalised the often cruel speaker loads. I say this appreciating that the US and other larger markets may have a different take on all of this as we UK audio lot were insular and totally dismissive of what the far east (Japan mainly then) and the US was doing. This 70's to 80's era is jurassic times for many posters here, when twenty years ago for oldies like me is but 'yesterday' in our terms and ancient history for many of you here

 

[Palladium]

The recommendation is due to 300 watts per channel for $350 from name brand company. I couldn't sell you its empty box for that much money!

That's used price though.

 

[Ageve]

So, the reviewer decides that 80 dB SINAD justifies a recommendation. I can’t see the justification.

1. The second harmonic is -80dB. The rest of the distortion is at, or below -94dB.

2. The dynamic range is very good.

3. The bandwidth is very good.

4. You get a lot of power for the money.

5. It's 20 years old, and not only does it still work. It still measures ok.

 

[DSJR]

Hmm .. would you kindly be specific? How about this, for example

SoundStage! Measurements - Bryston 4B SST Stereo Amplifier (10/2004)

SoundStageNetwork.com | SoundStage.com - BHK Labs Measurements: Bryston 4B3 Stereo/Mono Amplifier

www.soundstagenetwork.com

Bryston 7B SST2 monoblock power amplifier Measurements

Sidebar 3: Measurements I examined the Bryston 7B SST2's measured behavior using mainly Stereophile's loaner sample of the top-of-the-line Audio Precision SYS2722 system (see the January 2008 "As We See It" and www.ap.com); for some tests, I also used my vintage Audio Precision System One Dual...

www.stereophile.com

As I said in my post above, my HiFi Choice book review sensibilities pre-date these Brystons* you quote, which back then in the 80's weren't really on the domestic scene in the UK (they disappeared for a while until the tie up with PMC here). The amps Martin Colloms raved over were by ARC (SP8 and 10 I think, which were revised to make them 'even better'), the D-70 power amp (which I gather hated our UK mains voltage and blew up expensively as a result) and to be honest, the early Krell 50's and 100's which weren't judged as 'quite' at the top of Colloms' hierarchy, also measured no better and maybe worse than this Rotel apart from 2 ohm drive ability. Mr Colloms then expended his numerical subjective score to keep himself relevant and of course his wonderful references of the mid 1980's would numerically be judged poorly now compared to the latest ARC Reference preamp (how many expensive revisions does it take to make a transparent line buffer stage??? - another marketing can-o-worms not for this thread though)

I apologise for treating twenty years ago as 'last week' and fifty years ago when I started as 'just a few years ago.' Perspectives of time do change as we get older (and I know there are many here in their 70's and maybe 80's who can look back to the 50's and 60's audio products experienced 'first time round' with varying degrees of fondness I'm sure)

* The last twenty years have seen Bryston amps shoot up in price over here and maybe also in their home market too. I'd regard them as high end pro versions of amps like this Rotel, with solid and utterly dependable performance year in year out, but prices started to rise alarmingly in the noughties and few dealers got to know how basically good all rounders the brand could be apart from the more domesticated source/preamps they offered at more than double the price my previous BP25P cost..