Running Benchmark AHB2 in bridged mode and 4 Ohm Speaker

@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?

I will clarify; the bridged AHB2 drives the Kingsound King III ESL much better than a stereo unit alone, or two stereo units in passive biamp mode. 

As the discussion of the thread centers around bridged operation, I don't believe I have stated the capacity of a stereo unit on this forum to drive the Kingsound King III.

When I refer to "level unlimited" I mean that the amp is at maximum output of the preamplifier turned full on and the speakers not hitting past perhaps 87-88 dB. I would call an amp "level unlimited" where in my use I would not turn the level up more, but the amp could certainly provide a higher listening level. It may not be a technically correct description, but it serves to indicate the situation. I do not attempt to listen to systems at "live", i.e. above 90 dB levels, and I do not recommend others to do so. 

I have said several times previously that there is NO sonic degradation in bridged mode, nor distortion associated with running the amp full out. The amp is FAR superior sounding in bridged mode regardless of the speakers used, efficient or less efficient. 

 The AHB2 was never even close to clipping. Relevant to that, summarizing the discussion from the Owner's Manual, "... the AHB2 has an Over-Temperature Fault circuit that monitors the heat sinks constantly. If either one reaches the max allowable temperature the channels are muted to protect the amp and speakers. All high-power systems are shut down to facilitate cooling... One or both heat sinks will be very hot.. power reset after cooling." (Again, summary) 

The amps were actually running cool with the Kingsound King ESL, I could keep my hand on them. The amp also has a "Clip" light indicator, which never, ever came on. The King III is nominal 6 Ohm and 83 dB sensitivity. 




 

@kijanki  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.

I, prehaps misinterpreted this statement as something you agreed with.. 

 

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

 Under RMS testing (which I have responded to in your other thread) there is no power suppy reserve, its flat out. 

Please tell me how feedback is going to find power where there is no more. Feedback does not create power. Rather than keep telling me it does tell me HOW it does.