Andrew Heck

Active Member
In my present system I’m driving 150w speakers with a 100wpc power amp. I run my power amp wide open and control volume with my preamp. When I am really pushing the volume, the preamp potentiometer sits at 1 or 2 o’clock and I’m worried about inaudible clipping damaging my speakers. What I want to do is get two Parasound HCA-750s in bridged mode and run each channel in mono. The first advantage would be using an amp with better specs (especially the damping factor) and the second would be more headroom power to assure no clipping. Are there any factors I should take into account that I’m not thinking of? I’m not looking for louder,necessarily, just better power to really grab those drivers. Thanks for any advice you might have for me.
 
I had two Parasounds many years ago. I think the HCA-800, probably closely related. They had the handy bridging-switch on the back, which made it easy. I was disappointed — run as normal stereo amps, I thought they were average-sounding, maybe even mediocre — and bridging them only produced more of the same mediocre sound.

Just one man's opinion. I sold them to a friend for what they cost me, and he liked them. Could've been a bad match to my speakers (I tried both Quad Electrostatics and big studio JBLs), to my system in general, or just my personal taste. And your HCA-750s might be better.
 
I had two Parasounds many years ago. I think the HCA-800, probably closely related. They had the handy bridging-switch on the back, which made it easy. I was disappointed — run as normal stereo amps, I thought they were average-sounding, maybe even mediocre — and bridging them only produced more of the same mediocre sound.

Just one man's opinion. I sold them to a friend for what they cost me, and he liked them. Could've been a bad match to my speakers (I tried both Quad Electrostatics and big studio JBLs), to my system in general, or just my personal taste. And your HCA-750s might be better.
Hey, thanks for the feedback. I had an HCA-600 hooked up before the 800 and it was a superior amp. I agree with the 800 being lackluster. The 750 has much better specs and more in common with the 600 than the 800. In bridging, did you experience any obvious loss of sonic benefits? I have read that the damping factor is especially effected by bridging, but I cannot think why.
 
did you experience any obvious loss of sonic benefits? I have read that the damping factor is especially effected by bridging, but I cannot think why.
Bridgeable amps always have the warning: "8ohm and above speakers only." Theoretically they can't handle impedance dips into the lower realms. That may be what you were thinking about damping factor.
I'm glad you agree the 800's were not good amps, we're speaking the same language. I only used them briefly because I just didn't like them, and don't recall any details.

But that "8ohm and above" rule did not apply to my Audionics amps...

Run as normal 70W stereo amps, I found them average. But magic happens when you bridge them. It's not just the boost to 225 Watts — there's more vitality, more radiance. Sheer joy. They run really hot, biased high into Class A, and that Class A warmth and liquid flow is very evident in the midrange and crystalline highs.

Bridged, they were the best amps I ever found to drive my Quad 63 'statics. Quads dip way down to 2ohms, and these little bridged amps handled it without a hiccup, despite what the 'rules' say — and I was comparing them to bigger and far more costly Krell, Audio Research, VAC, and others.

So I guess that 8ohm-only rule about bridging doesn't apply to all amps. I'm told the Hafler 220 is another amp that elevates SQ when bridged, beyond mere higher watts, but I've never heard them myself. The only way to know about the Parasound is to try them — and if you have to buy them, you might consider others, such as the Hafler, which are plentiful and cheap. My love for the Audionics aside, they'll need new caps, I have four and they all do, so that's an extra cost.

Hope this helps, and please update us on your progress.
 
Bridgeable amps always have the warning: "8ohm and above speakers only." Theoretically they can't handle impedance dips into the lower realms. That may be what you were thinking about damping factor.
I'm glad you agree the 800's were not good amps, we're speaking the same language. I only used them briefly because I just didn't like them, and don't recall any details.

But that "8ohm and above" rule did not apply to my Audionics amps...

Run as normal 70W stereo amps, I found them average. But magic happens when you bridge them. It's not just the boost to 225 Watts — there's more vitality, more radiance. Sheer joy. They run really hot, biased high into Class A, and that Class A warmth and liquid flow is very evident in the midrange and crystalline highs.

Bridged, they were the best amps I ever found to drive my Quad 63 'statics. Quads dip way down to 2ohms, and these little bridged amps handled it without a hiccup, despite what the 'rules' say — and I was comparing them to bigger and far more costly Krell, Audio Research, VAC, and others.

So I guess that 8ohm-only rule about bridging doesn't apply to all amps. I'm told the Hafler 220 is another amp that elevates SQ when bridged, beyond mere higher watts, but I've never heard them myself. The only way to know about the Parasound is to try them — and if you have to buy them, you might consider others, such as the Hafler, which are plentiful and cheap. My love for the Audionics aside, they'll need new caps, I have four and they all do, so that's an extra cost.

Hope this helps, and please update us on your progress.
Wow, thanks for the in depth response and useful information. I’ll look into Hafler, I can snag 750s all day for $150ish, so I’ll compare critically. I’d rather find another HCA-600 but those are like the Ark of the Covenant. I guess they’re all under lock. They handle bass so much better than the 800s with a damping factor of >800, same for the 750s, but a bridged power rating of 150w which is exactly where I need to be at less than $100. So, I either wait to find a 600 (I already have one) or get two 750s and try to dump the 800.
 
Yeah, with a damping factor of >800, I’ve got some to give away.
I actually misinterpreted your original post, because you never said anyhting about improving the damping factor of an amp. You said using an amp with better specs. My aplogies.
 
Andrew - I believe if you do a bit of research on damping factor, you’ll discover that it’s more of a marketing spec than a meaningful one.

When driving an amplifier into clipping, it can make as much as two times the clean power it can make. Speakers manage power thermally and they really aren’t particular about how clean it is. Exceeding the speaker’s power handling capability is the cause for failure. Power vs time is really the key
consderation.

Bridging amplifiers can affect specificarions, true. However, there are no hard and fast rules that apply to all bridgeable amplifiers. Therefore, it’s always best to refer to the manufacturer’s published specifications in regards to stereo and bridged operation and compare for yourself.

Finally, a pair of bridged amplifiers offer all of the well documented benefits of mono blocks - increased separation, better soundstage and imaging, etc.

Good luck in your quest to find another 600 - patience is a virtue.
 
In my present system I’m driving 150w speakers with a 100wpc power amp. I run my power amp wide open and control volume with my preamp. When I am really pushing the volume, the preamp potentiometer sits at 1 or 2 o’clock and I’m worried about inaudible clipping damaging my speakers. What I want to do is get two Parasound HCA-750s in bridged mode and run each channel in mono. The first advantage would be using an amp with better specs (especially the damping factor) and the second would be more headroom power to assure no clipping. Are there any factors I should take into account that I’m not thinking of? I’m not looking for louder,necessarily, just better power to really grab those drivers. Thanks for any advice you might have for me.
I wouldn't worry that your pushing the amp too hard and into clipping just because the potentiometer is at the 1:00-2:00 position, this really isn't an indicator of how much headroom is left. I have speakers rated to 120 watts being driven with 325 watt amps, I also have speakers rated to 400 watts being driven with 35 watt amps, these numbers really aren't any kind of requirement.

Question, when cranking to this level what is your source?
 
I wouldn't worry that your pushing the amp too hard and into clipping just because the potentiometer is at the 1:00-2:00 position, this really isn't an indicator of how much headroom is left. I have speakers rated to 120 watts being driven with 325 watt amps, I also have speakers rated to 400 watts being driven with 35 watt amps, these numbers really aren't any kind of requirement.

Question, when cranking to this level what is your source?
The Sansui has to be cranked quite a bit more than the digital sources.
 
I wouldn't worry that your pushing the amp too hard and into clipping just because the potentiometer is at the 1:00-2:00 position, this really isn't an indicator of how much headroom is left. I have speakers rated to 120 watts being driven with 325 watt amps, I also have speakers rated to 400 watts being driven with 35 watt amps, these numbers really aren't any kind of requirement.

Question, when cranking to this level what is your source?
I've got a really good friend who has all kinds of electronic test equipment, and I plan to take all my amplification components to him, hook it up, set the main power to 100%, plug in 3.5mV to the 42-2109 and turn the preamp up until we observe square waves at the speaker outs. Then I'll know where she clips and I won't go past that point. It should be accurate and informative.
 
The Sansui has to be cranked quite a bit more than the digital sources.
Are you saying it needs to be cranked more with your source being a turntable than with digital IE a CD player? If so that's quite normal, CD players, tuners, tape decks usually have much higher output than most cartridge/phono interfaces.
 
Are you saying it needs to be cranked more with your source being a turntable than with digital IE a CD player? If so that's quite normal, CD players, tuners, tape decks usually have much higher output than most cartridge/phono interfaces.
Yes. And my real concern is that I’m pushing my amp too hard and it’s clipping the sine waves.
 
Yes. And my real concern is that I’m pushing my amp too hard and it’s clipping the sine waves.
Nope, the amp is receiving the same input to achieve the same output, just the maximum output will be lower. Less likely to drive the amp into clipping with the lower input than the higher, I wouldn't sweat it. If you still feel you need more volume maybe a higher output cartridge could be in your future.
 
I've owned several Parasound amps (current models). I used their 275 v.2 bridge for a center channel. That speaker was 4 ohm, so bridged that amp was seeing a 2 ohm load. I was always really impressed with that amp and the 2 ohm stable rating - which it was able to back up. It never had an issue and only got lightly warm.
 
Nope, the amp is receiving the same input to achieve the same output, just the maximum output will be lower. Less likely to drive the amp into clipping with the lower input than the higher, I wouldn't sweat it. If you still feel you need more volume maybe a higher output cartridge could be in your future.
I'm sorry, but I don't understand how the input is staying the same on my power amp. As I increase the output from my preamp by turning it's volume knob, am I not in danger of overdriving my power amp? Isn't that what clips an amp? And if that power amp is wide open, would I not be sending clipped power to my speakers?
 
I'm sorry, but I don't understand how the input is staying the same on my power amp. As I increase the output from my preamp by turning it's volume knob, am I not in danger of overdriving my power amp? Isn't that what clips an amp? And if that power amp is wide open, would I not be sending clipped power to my speakers?

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.
 
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