Mark Levinson Replica Amp

[Krunok]

The problem with doubling comes at the limits of the device.

Random example:

https://www.stereophile.com/content/luxman-l-509x-integrated-amplifier-measurements

"With clipping defined as when the THD+noise in the output reaches 1%, I measured clipping powers of 154Wpc into 8 ohms (21.9dBW, fig.5) and 250Wpc into 4 ohms (21dBW, fig.6)."

That's true. But let me show you a Rotel amp which has slightly stronger output stage than mine also measured by Stereophile guys:

"Using the conventional 1% THD definition of clipping, the Rotel puts out 291W into 8 ohms with one channel driven (24.6dBW), 558W into 4 ohms (24dBW), and even 800W into 2 ohms (23dBW)!"

I hope we'll agree that 558W is not really far from 291 being doubled.

https://www.stereophile.com/content/rotel-rb-1080-power-amplifier-measurements

That amp has been rated as 200W by Rotel. Mine is rated at 140W and it really doesn't make any sense to push it to the max as speakers will not sound very well there and my neighbours will not talk to me for a while.

 

[Ellisr63]

Well I couldn't resist getting a clone amp case for my B&O 3 channel biamped setup. I just ordered a clone KSA 50S amp case on eBay. I did not care if it said Krell or not (30 years ago I could have bought a Krell, but I chose going with Classe DR10 amps bridged instead...long since gone now). I just have always liked the look of the Krell amps with their massive handles and heatsinks. I looked at other options, but the plain Jane amp cases that were big enough just were blah looking. If I like this one I will see if I can find a smaller one for my biamped rear channels when I get that far on our Home Theater.

 

[watchnerd]

Well I couldn't resist getting a clone amp case for my B&O 3 channel biamped setup. I just ordered a clone KSA 50S amp case on eBay. I did not care if it said Krell or not (30 years ago I could have bought a Krell, but I chose going with Classe DR10 amps bridged instead...long since gone now). I just have always liked the look of the Krell amps with their massive handles and heatsinks. I looked at other options, but the plain Jane amp cases that were big enough just were blah looking. If I like this one I will see if I can find a smaller one for my biamped rear channels when I get that far on our Home Theater.

Am I reading correctly that you put a whole amp inside the case?

Or just boards, power supply, etc?

 

[Ellisr63]

I only purchased a clone case. I will be making it into a 3 channel amp (biamped). I will be installing 3 B&O 50asx amp modules, and 3 125asx amp modules (balanced/bridged). I will be punching or drilling the extra inputs, and outputs needed to complete the amp.
A couple of years ago a friend of mine assembled my B&O amp modules into a 14 channel amp, and when we moved to our current location I decided i wanted my new setup to be a balanced one (we were going to have the front speakers 75` from our preamp, so I started buying the balanced version of the 50 watt B&O modules... the 125w modules you can change to bridged/balanced). So a few months ago I started to disassemble the 14 channel amp, and also started to look for a better amp case since we had originally gutted a defective amp.

 

[DKT88]

That low end roll-off is obscene.

What coupling are you using and what capture device/software? Is it a soundcard front end? Mic input/Line?

What about this front panel markings- they cannot be serious!

View attachment 12511

Left Eye, Right eye and Power Nose!

and what body part euphemism do they use for the output? I won't venture a guess in this public forum.

 

[Ellisr63]

and what body part euphemism do they use for the output? I won't venture a guess in this public forum.

Speaker jacks must be an orifice. ROFL

 

[restorer-john]

I agree. They should all "double down" within some range of operation. Feedback compares the output voltage to the input, and maintains the gain, so double the current flows into the reduced impedance of the load.

Doubling the current is one thing, but the voltage swing cannot be maintained due to the increased voltage drops across the emitter resistors and Tr junctions. As power is a function of voltage and current, 'doubling down' never can truly happen.

The usual trick is to derate the high impedance specification to give the illusion to audiophiles who buy on numbers. When the amplifier gets reviewed, they think they are getting an even better deal because it tests way above spec or 'punches above its weight' etc.

 

[restorer-john]

"Using the conventional 1% THD definition of clipping, the Rotel puts out 291W into 8 ohms with one channel driven (24.6dBW), 558W into 4 ohms (24dBW), and even 800W into 2 ohms (23dBW)!"

I hope we'll agree that 558W is not really far from 291 being doubled.

That Rotel also blew up when being tested into low impedances. Clearly took out a channel and they only had a single channel left to run tests on. An amplifier that almost doubles down, blows its fuses and then ceases to function is a fail as far as I am concerned.

That said, I love Rotel gear. Generally, it is built beautifully and pretty much always performs better than spec.

I ran some tests only yesterday on a little vintage integrated Rotel (RA-930AX) I'll post in the reactive load thread today if you're interested.

 

[Jim777]

I ran some tests only yesterday on a little vintage integrated Rotel (RA-930AX) I'll post in the reactive load thread today if you're interested.

I am, I think they sound pretty good so curious to know.

 

[Krunok]

That Rotel also blew up when being tested into low impedances. Clearly took out a channel and they only had a single channel left to run tests on. An amplifier that almost doubles down, blows its fuses and then ceases to function is a fail as far as I am concerned.

That said, I love Rotel gear. Generally, it is built beautifully and pretty much always performs better than spec.

I ran some tests only yesterday on a little vintage integrated Rotel (RA-930AX) I'll post in the reactive load thread today if you're interested.

There was obviously something wrong with that unit, it had significant difference in output impedance from the start.

Btw, my RMB-1075 (5*120W, 160W in stereo) is THX certified, have much larger heatsinks and is running for more than 15 years without any problem.