Arcam tell me that the PA720 cannot be used to bi-amp ATC speakers.

[oliver_reid]

The Arcam AVR30 has 7 seperately amplified channels. I used 4 of them to bi-amp my ATC-19s (which for this specific purpose provide 4 binding posts ) No issues.

I now have a PA720 (also has 7 seperately amplified channel) and have hooked up these speakers the same way. I noticed a quiet “chk-chk-chk…” sound coming from the speakers - with no input signal present

I actually purchased this amp after Arcam support originally told me this would work fine

Now they are saying:

“Generally a ticking noise would point to a DC offset meaning the PA720 is not agreeing with the bi-wire set up causing the offset.”

They suggest that I do NOT bi-amp.

Could someone translate this for me..? The ATC’s are power hungry, and do sound better bi-amped

 

[oliver_reid]

FYI Arcam say "bi-wire" but I made it clear to them that I am bi-amping

 

[NiagaraPete]

FYI Arcam say "bi-wire" but I made it clear to them that I am bi-amping

Do you have a digital or electronic crossover of some sort?

 

[levimax]

FYI Arcam say "bi-wire" but I made it clear to them that I am bi-amping

Are you sure you are really biamping? This would require the speaker crossovers being bypassed and the use of an active crossover network between the source and the amp inputs. If the amp outputs are tied together the issue they mention may make sense. I would try hooking up one channel from the amp to the speaker normally and see if there is any noise .. the noise you describe could be caused by something else.

 

[NiagaraPete]

According the manual on page 17 is says "
ENEN-17 "Dual Mono / Bi Amp Mode - PA240 only

 

[DVDdoug]

The amplifier doesn't care if the signal is bandwidth-limited (fed from an active crossover). ...The amplifier doesn't know if you are bi-amping,

I can imagine a DC offset on the input causing a problem but most amps have a capacitor in the input to block DC. If you disconnect the input to the amp, that would go-away.

Another (unlikely) possibility... Is the clicking coming from the tweeter? The amplifier may "want" a DC current path.

Since you are not completely bypassing the speaker's internal passive crossover, the crossover will block DC to the tweeter (DC is zero Hz). In that case a resistor across the high-frequency output (or the speaker's tweeter input) might help. The resistor should be relatively-high (maybe 100 Ohms) to limit the current/power wasted by the resistor.

 

[oliver_reid]

Are you sure you are really biamping? This would require the speaker crossovers being bypassed and the use of an active crossover network between the source and the amp inputs. If the amp outputs are tied together the issue they mention may make sense. I would try hooking up one channel from the amp to the speaker normally and see if there is any noise .. the noise you describe could be caused by something else.

ATC set this up with 4 binding posts each pair connoted with metal player connectors . Normally you connect to one pair and the signal is fed to both pairs. If you remove the plate-connector the 2 drive units are independent and you can bi- amp - each driver has its own band pass filter. The is the way ATC designed it to work.

 

[DSJR]

ATC's always sound better fully active, but that's not what you want to hear...

Back before the SL driver update, the 20 passive ancestor of your 19's was single wired, although the bass and tweeter crossover circuits were on either side of the board and only coming together at the terminals which were sat in the middle and between the two networks (loads of images of these on the net). The 20SL put the second set of terminals on for fashion only I was told, at least at the time.

Since to the best of my knowledge, the tweeter and bass-mid 'circuits' are completely isolated if the links are removed from the speaker terminals, it really shouldn't affect the driving amp at all... I can't find an image of the 19v2 crossover and the 19 crossover image (that linked to the review here of the long discontinued previous model) showed a squashed up board layout compared to the 20's I had. The GR 'review' of the 19v2 has the crossover hidden from view apart from the edge of a coil just behind one of them (I wonder why?), probably because there's no update kit to sell!!! I didn't listen to his spiel, but I think there were some tube connecters waved about....

Sorry I can't help further. Granny sucking eggs - you did remove the terminal links, didn't you?

 

[oliver_reid]

According the manual on page 17 is says "
ENEN-17 "Dual Mono / Bi Amp Mode - PA240 only

I am not Bridging. That is what P 17 means. The AVR 30 - which has the same amp section (except for a smaller transformer) explicitly allows bi-amping

 

[oliver_reid]

ATC's always sound better fully active, but that's not what you want to hear...

Back before the SL driver update, the 20 passive ancestor of your 19's was single wired, although the bass and tweeter crossover circuits were on either side of the board and only coming together at the terminals which were sat in the middle and between the two networks (loads of images of these on the net). The 20SL put the second set of terminals on for fashion only I was told, at least at the time.

Since to the best of my knowledge, the tweeter and bass-mid 'circuits' are completely isolated if the links are removed from the speaker terminals, it really shouldn't affect the driving amp at all... I can't find an image of the 19v2 crossover and the 19 crossover image (that linked to the review here of the long discontinued previous model) showed a squashed up board layout compared to the 20's I had. The GR 'review' of the 19v2 has the crossover hidden from view apart from the edge of a coil just behind one of them (I wonder why?), probably because there's no update kit to sell!!! I didn't listen to his spiel, but I think there were some tube connecters waved about....

Sorry I can't help further. Granny sucking eggs - you did remove the terminal links, didn't you?

That is helpful. Thanks. I agree. The two drive units are driven in isolation when the plates are removed.

 

[NiagaraPete]

I am not Bridging. That is what P 17 means. The AVR 30 - which has the same amp section (except for a smaller transformer) explicitly allows bi-amping

Okay.

 

[DVDdoug]

The ATC’s are power hungry, and do sound better bi-amped

In theory you could double the power (+3dB louder) with 100W into the woofer plus 100W into the tweeter. But real-world audio contains much less energy in the high frequencies and 100W of high-frequency energy into the tweeter would fry it! Typically in bi-amped & tri-amped speakers the low frequency drivers use larger amplifiers, especially subwoofers.

Bi-amplifying does allow you to easily adjust the woofer & tweeter levels separately,

Also, it's tricky to match the active crossover with the passive crossover built-into the speaker. A properly bi-amplified speaker doesn't have passive crossover (except maybe some low frequency protection for the tweeter in case something goes wrong). The passive crossover also introduces some slight signal loss so it helps if you don't have one.

 

[Everett T]

The Arcam AVR30 has 7 seperately amplified channels. I used 4 of them to bi-amp my ATC-19s (which for this specific purpose provide 4 binding posts ) No issues.

I now have a PA720 (also has 7 seperately amplified channel) and have hooked up these speakers the same way. I noticed a quiet “chk-chk-chk…” sound coming from the speakers - with no input signal present

I actually purchased this amp after Arcam support originally told me this would work fine

Now they are saying:

“Generally a ticking noise would point to a DC offset meaning the PA720 is not agreeing with the bi-wire set up causing the offset.”

They suggest that I do NOT bi-amp.

Could someone translate this for me..? The ATC’s are power hungry, and do sound better bi-amped

They maybe be power hungry, but biamping isn't gonna be the best solution to satisfy them. With a sensitivity of 85db, just pick a good power amp to reach your desired spl levels. Biamping isn't going to benefit you one bit with that speaker (passive) same as with most all speakers. There are some exceptions, just few and far between.

 

[Soniclife]

now have a PA720 (also has 7 seperately amplified channel) and have hooked up these speakers the same way. I noticed a quiet “chk-chk-chk…” sound coming from the speakers - with no input signal present

Which drive unit is making the noise? What happens if you disconnect the other drive unit?

 

[sys4096]

Is the 12V trigger cable connected between your preamp and the PA720 ? Try again without the trigger cable. This resolved the issue I had with my setup.

 

[amirm]

What they are telling you makes no sense.

 

[wwenze]

If you have a multimeter, I would:

1) Resistance measurement mode, measure the resistance across the tweeter terminals, and then measure the resistance across the woofer terminals. Tweeter terminal should show open or some high value (like >8ohms), woofer should show <4ohm usually. If both speakers measure the same, then all good. Heck, might as well measure between tweeter and woofer terminal because why not, if Arcam is complaining about a path between tweeter and woofer terminals. Switch to diode mode for this job; while resistance mode will push just a small voltage, diode mode will push at least 0.7V and as high as VCC depending on your meter.

2) DC voltage mode, with speakers disconnected, measure the amp for any DC offset. Repeat with speakers connected.



Would be funny if the amp design has a high unloaded bias offset which requires a low DC load resistance to suck it up. This seems to make what Arcam is saying make sense tho.

 

[jhaider]

“Generally a ticking noise would point to a DC offset meaning the PA720 is not agreeing with the bi-wire set up causing the offset.”

They suggest that I do NOT bi-amp.

Could someone translate this for me..?

They think you connected two channels to a speaker with the straps connecting the terminals, they think ATC miswired the crossover, or they’re lost at sea.

 

[Daka]

Any luck getting to the bottom of this?

 

[Triggerhappy]

In theory you could double the power (+3dB louder) with 100W into the woofer plus 100W into the tweeter.

Not really, as no speaker input (HF/LF) see any more (or less power) from the amp then the 100W in to the speaker terminals.