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Amp channels running in parallel?

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Running your amp channels in series (bridged basically) is cool and all, but does anyone have experience with running them in parallel?

From a technical point of view, the amp with the higher output voltage will try to drive the amp with the lower voltage, so they should be matched as closely as possible when operating in parallel mode. To my understanding, having dissimilar voltages on a BTL setup only reduces the overall voltage swing, so we're not going at full power.
In bridged mode operation, the two amps will both see half of the impedance, as voltage is doubled. In parallel mode, the amps will see double the impedance, as current is doubled, which would, for example, make driving the 1 Ohm IPAL a lot easier. Also, you could couple 4 amps like this, which would provide double voltage and double current to the loudspeaker while keeping impedance (and damping factor) the same.
To go even deeper, to my knowledge the output transistors on an amplifier operate in parallel(?), so adding a second output stage might be similar to adding more transitors. Would it be possible to build an infinitely powerful amp with just adding more paralleled transitors?

Crown's old Macrotech amps have a parallel feature, which expects you to run a jumper wire from 1+ to 2+ on the output side.
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Do you have a MA5002VZ? I have a couple in very bad shape that I'm trying to fix and as they have previously been fiddled with and there are discrepancies between the service manual wiring diagram and the silk screen I'm unsure if the cables P500 and P501are in the correct positions (there are another set of cables underneath them) (this is how it came to me).  I did some basic checks against the MA5000VZ schematic on the pin outs and I think this is correct...

As for parallel mode like lots of the design of this amp it doesn't make sense to me as at least at the time it was launched the available drivers had 8 ohm voice coils so for it to be useful the amp would have to be loaded with a ludicrous number of drivers.  The very large number of parallel transistors approach was used with amps like the Void Infinite 8: https://www.abeltronics.co.uk/amptesting.php?z=Void_Infinite_8_mk2

*on a side note the forum upload limit seems to have been reduced to 0.08MB!?!?  (my picture didn't seem to work as well  - try https://drive.google.com/file/d/1iQ59CYpxIum91ivtv0ULTfLJV3aFF2jt/view?usp=sharing )

 

Edited by kipman725
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Kipman I'll try to look into the user data limits with Kyle. It may be that you've maxed yours out rather than a hard limit on the size of the pics.

The car audio guys have been strapping multiple amps together to drive a single load for years. It's rare in pro audio anymore. Seems to be mostly back in the 80's and 90's. I've always heard that it can get messy if the amps gains aren't matched correctly. No hands on experience with this though.

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11 hours ago, kipman725 said:

Do you have a MA5002VZ? I have a couple in very bad shape that I'm trying to fix and as they have previously been fiddled with and there are discrepancies between the service manual wiring diagram and the silk screen I'm unsure if the cables P500 and P501are in the correct positions (there are another set of cables underneath them) (this is how it came to me).  I did some basic checks against the MA5000VZ schematic on the pin outs and I think this is correct...

As for parallel mode like lots of the design of this amp it doesn't make sense to me as at least at the time it was launched the available drivers had 8 ohm voice coils so for it to be useful the amp would have to be loaded with a ludicrous number of drivers.  The very large number of parallel transistors approach was used with amps like the Void Infinite 8: https://www.abeltronics.co.uk/amptesting.php?z=Void_Infinite_8_mk2

*on a side note the forum upload limit seems to have been reduced to 0.08MB!?!?  (my picture didn't seem to work as well  - try https://drive.google.com/file/d/1iQ59CYpxIum91ivtv0ULTfLJV3aFF2jt/view?usp=sharing )

 

I don't personally own a Macrotech, no. I just stumbled across this amp when researching this topic.
The Void amp is interesting, was that their own design? To my knowledge they are just rebranding Powersoft amps.

Parallel mode use could find some use in special cases. Ricci's testing here would probably benefit having two bridged K20s in parallel, as that would make compression sweeps more accurate and would handle something like the 2Ohm IPAL SKHorn well. And he'd burn through even more voice coils.

It's hardly useful, but still interesting. Like 30" drivers 🙃

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Void used to have their own amp designs up to and including the X series (X6/X8) but now rebrand Powersoft.  QSC amps have the capability of combining amp channels in parallel:, series and series parallel:

https://www.qsc.com/systems/products/q-sys-ecosystem/products-peripherals-accessories/network-amplifiers/cx-q-series/cx-q-8k4/?L= 

The MA5002VZ is kind of the ultimate class AB (ish) amplifier  (just check its specs, very Hi-Fi).  It has a circuit topology called grounded bridge which doubles the effective voltage swing of the power stage and also a circuit that series stacks the power rails.  The end result is efficiency like a class-G amp (switched rail) but with the performance of a lower voltage class AB amplifier (no rail switching events, lower voltage faster output transistors).  It also includes extensive monitoring that  models the thermal reserve of the output transistors and keeps the amp in safe operating area.  That means if its working right you can just load it up with parallel sub drivers until the Ilimit lights start to flicker or the amp starts to thermal limit.  However to do this lots of the circuits are floating and there is a lot of complexity (no microcontroller) so when the amplifier goes wrong its hard to fix at a component level.  Fixing the amp at the module level is very easy though due to extensive diagnostic indicators and easy disassembly.  It would have been very interesting is Crown had made a SMPS version of the MA5002VZ as almost all the weight and bulk is due to the transformers, it would have been very competitive with class-D amps (although perhaps not in cost due to the large number of transistors required).

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A modern implementation of combining any amount of channels within an amplifier should be fairly simple. Just deploy a feedback loop system which sets gains of slave channels for their output voltage to match the master channel.

I don't know much about amplifier classes, except that class H is heavy af and class D is the new super efficient stuff which makes for lightweight amps which are so efficient that they don't need big heatsinks anymore.

Do you happen to know at which voltage the PS of the MA is operating at? It's probably possible to do such a retrofit yourself.

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