Bridging Parasounds

[Andrew Heck]

I

The preamp if fed no signal would have no effect on the power amp even if turned up to the max correct? So no worries of clipping correct?

So it stands to reason if the input signal to the preamp is less then the signal sent to the amp will also be less correct? This is the reason you're needing to turn the volume pot further to achieve the same output level, less in equals less out.

With this in mind you can see where the higher output sources like CD, tuner, etc would be more capable of pushing the preamp to overdrive the power amp into clipping.

Hope this helps.

I was somehow under the impression that gain was not linear. I thought it was on a curve so the actual voltage needed to reach an increased decibel level from a lower input was exponentially more than it took to reach the same decible level for a higher voltage input.

 

[Grenadeslio]

I

I was somehow under the impression that gain was not linear. I thought it was on a curve so the actual voltage needed to reach an increased decibel level from a lower input was exponentially more than it took to reach the same decible level for a higher voltage input.

Watts are watts, it's the reason your higher input sources are louder. Try connecting your turntable through the aux input, or a MC cartridge through a MM phono stage, crank the volume pot all you want you won't get enough output to clip the amp.

It's the reason amps are rated for X wattage output at Y input voltage. A change in the input voltage either way will see a corresponding change in output wattage, to a point. To high a voltage input will stress the components not rated for such.

The problem with too low of an input voltage is increased noise to signal ratio from cranking the amp in an attempt to increase output.

 

[Grenadeslio]

The sensitivity of a power amplifier is that specified voltage at the input (with the level control wide open) that will cause the amplifier to reach full rated power. An amplifier that has a rated sensitivity of 1 Volt at 4 Ohms and has a voltage gain of 40X's will then deliver 40 Volts into the 4 Ohm load.

One customer's faulty linear logic, (which many innocently share) was that he was okay, because he turned down the level control on the front of the amplifier to limit his output power. This makes me want to say a few cuss words. Turning down the level control does NOT limit the amplifiers full output capability (in Watts). It only changes the SENSITIVITY as to what amount of voltage at the input causes the amplifier to reach it full rated output power in Watts. The amplifier now has a voltage gain of times 20 to reach 40 Volts. So if, you have a 400 Watt amplifier that is sensitive to 1 Volt into 4 Ohms, that would be 400 Watts (40 x 40 / 4 = 400). Now, if you turn the input level down to -6 dB, you changed the sensitivity and the voltage gain by -6 dB, you did NOT reduce the maximum power output to ¼ (-6 dB), as it can still reach full rated power, but it would take twice the voltage at the input to reach the rated maximum power. As it would then be sensitive to 2 Volts at the input to reach 40 Volts at the output, which would now be a times 20 voltage gain.

 

[BigElCat]

I purchased two HCA-750A amps (and a matching PL/D 1100 pre-amp) with the intent to bi-amp my ADS L-1290 speakers.

The bi-amping didn't work out, so I ran them in bridged mono mode for a couple of months.

I rotated my Sansui AU-X701 integrated back into the system, and was amazed at how the Sansui out performed the HCA-750 amps. The Sansui is rated at something like 120 watts rms, and the HCAs were supposed to deliver 250 watts in bridged mode. The Sansui has equal volume (at any given gain setting), and better bass .

 

[Grenadeslio]

Could always go this route.

Just saw these on eBay.

 

[Andrew Heck]

I purchased two HCA-750A amps (and a matching PL/D 1100 pre-amp) with the intent to bi-amp my ADS L-1290 speakers.

The bi-amping didn't work out, so I ran them in bridged mono mode for a couple of months.

I rotated my Sansui AU-X701 integrated back into the system, and was amazed at how the Sansui out performed the HCA-750 amps. The Sansui is rated at something like 120 watts rms, and the HCAs were supposed to deliver 250 watts in bridged mode. The Sansui has equal volume (at any given gain setting), and better bass .

Thanks for the heads up. I'm surprised, honestly. I loved my 600, it just didn't push what I needed. I thought they'd be beasts bridged.

 

[Andrew Heck]

Could always go this route.

Just saw these on eBay.

View attachment 1217162

those look nice, but i want more...
and to that end!
i have decided to go with......
a wild card.
I placed an order for a Hafler. Sounds pretty good right? well, hopefully, but wait, there's more.
It's actually a modded Hafler. It was used in movie theaters, so it's THX certified, Rated at 270 wpc, with a stupid huge transformer and more capacitance than you can shake a stick at. A company called Smart (very original) bought up a bunch of old Haflers and tricked them out for movie theater use and now I'm getting one. I read a post on a theater forum by Oscar Nuendorfer (who is now the chief electrical engineer at Panasonic) explaining how powerful and clear these amps are. He played a role in designing them and they're supposed to be very low distortion, too. Hell, I may have made a big mistake but the price was vvvvveeeeery low and there was so little information on them, just like my Legend Audio speakers which are crazy great, that I thought I might repeat the sonic magic I scored with them. If I'm wrong I'll start over and look for an Adcom 5500 or something.
Yes there is a fan because they're pro gear, but it's purported to be "whisper quite" when it ever comes on. Yes I had to order RCA to XLR cables, but the amp was dirt cheap. Ditto for the argument that the capacitors will cost a fortune to replace if they're tired or go bad.
I'll laugh at myself with all of y'all if it sucks.

 

[Andrew Heck]

http://www.film-tech.com/warehouse/manuals/ta250-450.pdf