Rotel RB-1070 Amplifier Review

[H-713]

Probably the design with lower loopgain (lower feedback factor). Maybe intentionally resistor loaded VAS. Separate THD (not THD+N) measurement would reveal more, or spectrum measurements at various power. But, the 5W distortion is too high, I would expect lower distortion from this Rotel amplifier.

Nice to see 3 pairs of power transistors per channel, the SOA will be better than with similarly power rated commercial audio amplifiers, good for reliability.

I can't help but wonder if the distortion is dominated by a grounding issue. The distortion mechanism that I struggled with for a while was figuring out how to handle the ground for the output stage decoupling caps. I've seen quite a few amplifiers that exhibit this behavior, so I suspect I'm not the only one who's made that mistake a few times.

This amp is at an immediate disadvantage from a PCB layout perspective in that it's a single-sided board. I'm not saying that you can't get good performance out of a single-sided board (It's been done many times), but it does take a lot more skill.

 

[pma]

And single board for 2 channels, probably common supply and common gnd for both channels. I agree, difficult to fix then.

 

[manisandher]

Ah, Rotel at last . Thanks Amir.

I've been a long-time Rotel fan. Started with an RCD-855 at uni. Workted my way up to this full Michi stack by the early '00s:



Sounded as good as it looked.

Currently using a couple of monster RB-1590 amps to drive my subs.

Mani.

 

[fredoamigo]

Bridge mode is unusual as you need to remove the cover and configure three jumpers.

Yes it is, but even for a person with two left hands like me it's easy to do, you... you could do it blindfolded

 

[Bleib]

Wow. Many years ago Rotel 1080 and 1090 used to be the end game poweramps to have.

 

[Eleo]

Interesting to note that Thd - albeit rather high - is dominated by even order harmonics - third harmonic is -105db or so. Therefore, I guess, it is not a concern. Likely, newer models, being completely dual mono, are even better

 

[Tangband]

Hmm not very impressed. Compared with the topping pa5 with tpa 3251 chip inside ( same chip as my Aiyima a04 ) , the Topping pa5 outperform* the Rotel below clipping point. Lots of power with the Rotel though.

*In my experience, such differences is something that you can hear, to. The tpa3251 based amplifier will sound clearer.

 

[Sokel]

Something meeting it's specs after 20 years....well,that's what I call good engineering and respect to user.
And will probably work many more with some care.

Thanks Amir!

 

[manisandher]

Hmm not very impressed.

Perhaps you missed this?

It was released in early 2000.

Mani.

 

[Tangband]

Perhaps you missed this?



Mani.

Yes , its technology from the 2000, and it was rather good then. Not now.

 

[Sokel]

Yes , its technology from the 2000, and it was rather good then. Not now.

View attachment 258709View attachment 258710

Rotel still works thought
(you should have choose some other today's amp )

 

[pma]

This is the schematics. @syn08 would not like it .

As expected, VAS is resistor loaded. The sound will be “full”, owners would like it.

 

[restorer-john]

I've happily run a pair of RMB-100 MOSFET monoblocks for years

I've always considered that mechanical construction design of the RMB-100 amps as ideal, inexpensive and easy to replicate. I often wonder why DIYers don't replicate that style.

 

[restorer-john]

This is the schematics.

The unit reviewed is a version 2 or 3. Note the auxilliary transformer and optocoupler trigger. The rest of the schematic seems identical.

 

[Eleo]

Yes , its technology from the 2000, and it was rather good then. Not now.

View attachment 258709View attachment 258710

Again, I highlight the difference for what concernes third harmonic: -105 db Rotel, -120db Topping. I assume that difference is utterly inaudible. Differences in power are not. Maybe noise can be a problem with sensitive speakers

 

[pma]

Sanken’s used, that’s fine.

 

[restorer-john]

Again, I highlight the difference for what concernes third harmonic: -105 db Rotel, -120db Topping. I assume that difference is utterly inaudible. Differences in power are not. Maybe noise can be a problem with sensitive speakers

Rotel amplifiers are incredibly reliable, conservatively rated, well made, well priced and a joy to use and own. I have many Rotel pieces from the same era and before as this amplifier. Noise (residual) is not their strongest attribute, but in practice, is not noticed.

You can't put Topping and Rotel in the same sentence on my opinion. One brand is legendary for all the above attributes, the other has a long way to go....

 

[Eleo]

Rotel amplifiers are incredibly reliable, conservatively rated, well made, well priced and a joy to use and own. I have many Rotel pieces from the same era and before as this amplifier. Noise (residual) is not their strongest attribute, but in practice, is not noticed.

You can't put Topping and Rotel in the same sentence on my opinion. One brand is legendary for all the above attributes, the other has a long way to go....

I’m not comparing Topping to Rotel I was replying to a previous post. Btw I always liked Rotel gear and had, among others, the Rb 1552, which is basically the same as th Rb 1070

 

[pma]

Rotel amplifiers are incredibly reliable, conservatively rated, well made, well priced and a joy to use and own. I have many Rotel pieces from the same era and before as this amplifier. Noise (residual) is not their strongest attribute, but in practice, is not noticed.

You can't put Topping and Rotel in the same sentence on my opinion. One brand is legendary for all the above attributes, the other has a long way to go....

I remember testing this amp against Classé CA-200, with Wilson Audio Maxx speakers.

Classé CA-200 stereo power amplifier Measurements

Sidebar 3: MEASUREMENTS My 240V–rated example of the CA-200 happily delivered a neat 270Wpc into 8 ohms (24.3dBW) for program-related duty cycles driven by the UK's nominal 240V power (the actual voltage was 242V). Singly driven flat-out into 8 ohms continuous, the just-clip level was 250W...

www.stereophile.com

 

[restorer-john]

I’m not comparing Topping to Rotel I was replying to a previous post.

I know. I was talking about Rotel in general and agreeing with/adding to, your noise comment.