Running Benchmark AHB2 in bridged mode and 4 Ohm Speaker

@kijanki  I agree, but amp that doubles power exactly has to have adequate power supply AND deep negative feedback. Exact doubling implies perfect regulation (ideal voltage source), that is not possible without deep feedback.

What part do you agree with? If you do agree that feedback does not make up for these losses why do you keep bringing up deep feedback. (also a term I have never heard)

1. What about the emitter resistors? You cannot ignore them. 

2. How good is the supply regulation? 1% ?

3. What does the deep feedback have to do with it? If the damping is even 10 thats enough. Its only going to affect the shape of the clipping and make it worse not better.

If for some silly reason you want the power to exactly double then you make a power supply that puts out more voltage as more current is drawn. Kinda upside down idea. 

If you can site an amplifier that exactly doubles bring it on. Show me.

Ramtubes, I explained exactly what I agreed with by quoting your statement - read again.

Why are you bringing emitter resistors again, yes we know that they exist. 

I'm not sure why you're asking me what Benchmark voltage regulation is.   Perhaps you should direct this question to John Siau.

What does the deep feedback have to do with it?

Feedback lowers output impedance.  You cannot make exact doubling of the power if DF=10.

If you can site an amplifier that exactly doubles bring it on. Show me.

There are many of them (I'm surprised you don't know that).  For instance Rowland model 535 is specified for 250W@8ohm and 500W@4ohm.  Krell Evolution 302e specifies 300W@8ohm 600W@4ohm and 1200W@2ohm (both channels driven).  Pass Labs XS150 states 150W@8ohm 300W@4ohm  etc.

You keep asking "what feedback has to do with it" while I'm trying to show you, that exact doubling of power cannot be achieved without deep feedback.  Exact doubling of the power is treated on this forum as a virtue, while I don't think it is necessary a good thing and might be even harmful when deep feedback is used to spike-up amplifier's  specifications while creating TIM distortions at the same time.

@kijanki  Ramtubes, I explained exactly what I agreed with by quoting your statement - read again.

Why are you bringing emitter resistors again, yes we know that they exist.  

I'm not sure why you're asking me what Benchmark voltage regulation is.  Perhaps you should direct this question to John Siau.

What does the deep feedback have to do with it?

Feedback lowers output impedance. You cannot make exact doubling of the power if DF=10.

If you can site an amplifier that exactly doubles bring it on. Show me.

There are many of them (I'm surprised you don't know that). For instance Rowland model 535 is specified for 250W@8ohm and 500W@4ohm.  Krell Evolution 302e specifies 300W@8ohm 600W@4ohm and 1200W@2ohm (both channels driven). Pass Labs XS150 states 150W@8ohm 300W@4ohm  etc.

You keep asking "what feedback has to do with it" while I'm trying to show you, that exact doubling of power cannot be achieved without deep feedback. Exact doubling of the power is treated on this forum as a virtue, while I don't think it is necessary a good thing and might be even harmful when deep feedback is used to spike-up amplifier's specifications while creating TIM distortions at the same time.

I know of all those amps and those specs. But those are marketing numbers. Can you tell me the actual measured clipping power at those various loads. 

I keep asking about the emitter resistors because when you drop the load impedance and more current is drawn the drop across those resistors (and any other resistances) doubles and it appears you dont want to take that into account. 

I have not been asking or referring to the Benchmark in this discussion. 

Exact doubling of the power is treated on this forum as a virtue

,

I dont see why it is a virtue especially if it is just a spec and not what is really going on. Has Stereophile tested any of these amps. Please provide a link. 

Yes, drop across resistance will double, but reserves in power supply combined with the feedback will make up for that.

I dont see why it is a virtue especially if it is just a spec and not what is really going on. Has Stereophile tested any of these amps. Please provide a link.

I never said it is a virtue - just the opposite.

@kijanki 

Heres a Rowland that specs 60 into 8ohms,  120 into 4 ohms just the way you like it. The actual measured powers are "  Fig.7 indicates the THD vs power for 8, 4, and 2 ohms at 1kHz, one channel driven (bottom, middle, and top curves respectively; line voltage of 113V). The maximum output power at 1% THD was 84W (19.2dBW) into 8 ohms, 140W (18.5dBW) into 4 ohms"
Read more at https://www.stereophile.com/content/jeff-rowland-design-group-model-1-power-amplifier-measurements#D...

The spec is twice the power into 4/8 ohms is just as you like 120/60 watts. The measured is 140/84 watts, not double. Note as I predicted the 8 ohm power is understated as it must be. But 120/60 watts are just minimum specs, not what the amp CAN do. Good manufacturers always underspec to make sure they make spec. 

Here is a Krell speced very close to 2/1 power into 4/8.  However the actual ratio is 910/625 watts. hardly 2/1. 


 Although the Krell's specified maximum power into these loads is very high, at a respective 575W (27.6dBW) and 900W (26.5dBW), the amplifier exceeded those powers, clipping at 625W into 8 ohms (28dBW) and 910W into 4 ohms
Read more at https://www.stereophile.com/content/krell-solo-575-monoblock-power-amplifier-measurements#17OE2KQdwm...

Cant you see that the doubling down is just a spec and to make that spec they have to go way over on the 8 ohm to get the 4 ohm to work out. The Krell barely makes spec with only 10 watts to spare on 4 ohms but exceeds 8 ohm power by 50 watts. 

I have a friend that loves to see amps double down but none actually do. Its nice when they get close but its just impossible to be exact or just close. 

Where does this religion of doubling down get its followers?