Looking for a class D amp that goes down to DC or thereabouts....

[Doodski]

3hz are thereabouts,aren't they?

That's a nightmare!

 

[sarumbear]

DC or thereabouts as the title of the thread says.
It's not my language but 3hz are thereabouts,aren't they?

It’s not the language but prior art:

FREQUENCY RESPONSE​

• Better than 0.1 Hz to 200 kHz, +0/-3 dB

Benchmark AHB2 Power Amplifier

Benchmark's new AHB2 Power Amplifier - "The Quietest, Cleanest Audio Amplifier on the Planet"

benchmarkmedia.com

 

[Oristo]

DC coupling means DC in, DC out.

Hafler power amplifiers are DC coupled in the forward direction;
DC negative feedback correction was stronger than for audible frequencies,
to prevent sending DC to speakers. In other words, lowpass-filtered negative feedback.
I suppose that similar tricks are employed in other nominal DC-coupled amplifiers.

 

[Doodski]

Hafler power amplifiers are DC coupled in the forward direction;
DC negative feedback correction was stronger than for audible frequencies,
to prevent sending DC to speakers. In other words, lowpass-filtered negative feedback.
I suppose that similar tricks are employed in other nominal DC-coupled amplifiers.

I must ask. Things like this can eat me up with curiosity in a very good way. Coming from the north I see and have read about many sorts of peeps that come here for stuff and even for first line defense. What does, "Signal processing R&D." mean. What did you do or do?

 

[CINERAMAX]

Hehe, Oh boy I opened Pandora's here, thank you all. A Double Bass Array where I am hoping to reach into the single digits (7-8?), it is based on these modules. In my past experience with ELF/ULF the rotary subwoofer the amp went down to DC as part of the requirement but the operating range of the TRW-17 rotary woofer is 1-20. Here we are trying to lower the floor of these arrays ( from the regular 12hz when running throughout its whole band) through filtering at the highest frequency the planar wavefront can be created, this is a function of how close the subwoofers are to each other. Im keeping them in the 1/4 to 1/3 of the wall dimension range zones.

The client wants to replace the individual 350wpc@4 class a/b with a multichannel class D, but there is little bandwidth Data available on the typical CI multichannel class D amps from Trinnov and Ati. With the new Trinnov MSMC steered planar wavefront based software, these towers lend themselves for single row media room apps. It is a lot easier to do these DBA's in projection cinemas than they are with videowalls. This is what I've come up with: Our 4 10 towers are 14"w x12"d x46"tall. Im hiding the woofers behind an isolated wood lattice cover.

According to Jon Herron in this video the closer you can get those woofers together the higher up in the range the MSMC will operate to somewhere around 100hz ( I think 125hz is the best case scenario with projection), by purposely limiting the woofers to no more than whatever that maximum operable range limit for the planar wave will be, we give it downward headroom to reach below the teens. Thus I am looking for a multichannel rackmount amp with decent power that goes at least down to 8Hz in bandwidth ideally excelling in all low frequencies criteria. Thanks again!

 

[boXem]

I understand but you have not answered my question: what does that DC response offer if it can’t be utilised fully to the amp’s spec?

Nothing. This is why we added a high pass in our more recent offering. These are audio amplifiers, not soldering stations.

 

[chris256]

This is why we added a high pass in our more recent offering.

The worst thinkable "solution". It's easy / primitive nowadays and cheap. It harms frequency response and adds distortion (each filter adds distortion). That's completely unnecessary if you would add a monitor instead which jumps in, if DC is detected and switches off power or reduces power - accompanied by a warn LED. Other manufacturers (like RME or T+A e.g.) are able to provide those correct solutions.

 

[boXem]

The worst thinkable "solution". It's easy / primitive nowadays and cheap. It harms frequency response and adds distortion (each filter adds distortion). That's completely unnecessary if you would add a monitor instead which jumps in, if DC is detected and switches off power or reduces power - accompanied by a warn LED. Other manufacturers (like RME or T+A e.g.) are able to provide those correct solutions.

I guess that because something is easy and cheap, it's not good, right?

- frequency response:

- Distortion:

- shutting down the amp as soon as there is a tiny DC in the source sounds like a great plan... As far as I know RME doesn't make power amps and T+A uses the mechanism used in the Purifi modules, like we do.

Any other comment?

 

[chris256]

shutting down the amp as soon as there is a tiny DC in the source sounds like a great plan

You have to shut down if it's harmful. Not if it's tiny. Please no black and white painting.

RME doesn't build power amps - but pre amps. Same point here: you don't want DC at the output. RME provides two solutions (at least for the ADI 2 DAC FS which are switchable by the user): filter or hardware monitor. They subsequently added a filter because there are a few broken sources around, which wouldn't be played by the monitor.
Another point: if the source is broken, you have to fix the source (the culprit) and not the sufferer. For digital sources it's pretty easy to remove DC offset.

Your attached measured values don't say anything about distortions around 20 Hz. Each filter has distortions / phase errors. There is no filter without distortion or errors in general. That's why you don't want any filters in the signal path at all. Goal is a straight wire!

I have a T+A A200. The monitor drives a LED, which warns before the shutdown would be kicked in (if tiny DC is detected). If harmful DC is detected it's shut down - exactly what is expected. But DC (if it's already part of the source) is not the fault of the poweramp - therefore it's ok if it shuts down. You have to fix the source - that's the way to go!

T+A uses the mechanism used in the Purifi modules, like we do.

The 1ET400A-modules implement a protection circuit according specs which monitors some critical parameters / stages - including DC offset. So no reason for a filter at all.

 

[boXem]

You have to shut down if it's harmful. Not if it's tiny. Please no black and white painting.

RME doesn't build power amps - but pre amps. Same point here: you don't want DC at the output. RME provides two solutions (at least for the ADI 2 DAC FS which are switchable by the user): filter or hardware monitor. They subsequently added a filter because there are a few broken sources around, which wouldn't be played by the monitor.
Another point: if the source is broken, you have to fix the source (the culprit) and not the sufferer. For digital sources it's pretty easy to remove DC offset.

Your attached measured values don't say anything about distortions around 20 Hz. Each filter has distortions / phase errors. There is no filter without distortion or errors in general. That's why you don't want any filters in the signal path at all. Goal is a straight wire!

I have a T+A A200. The monitor drives a LED, which warns before the shutdown would be kicked in (if tiny DC is detected). If harmful DC is detected it's shut down - exactly what is expected. But DC (if it's already part of the source) is not the fault of the poweramp - therefore it's ok if it shuts down. You have to fix the source - that's the way to go!


The 1ET400A-modules implement a protection circuit according specs which monitors some critical parameters / stages - including DC offset. So no reason for a filter at all.

So if I read you well, if RME adds a filter because broken sources exist (sometimes there is even DC in the recording), it's OK, if we do the same, we are wrong... Makes sense...
Multitone says everything about distortion around 20 Hz.
Maybe you should consider the enventuality that I know more about about aftersales, electronic systems, amplifiers, sources and the Purifi modules than you. Enjoy your (nice) electronics, have a nice day, and sorry for not owning a German company.

 

[sarumbear]

Nothing. This is why we added a high pass in our more recent offering. These are audio amplifiers, not soldering stations.

Thank you for correcting your initial error of judgement

 

[chris256]

if RME adds a filter because broken sources exist (sometimes there is even DC in the recording), it's OK

No - it isn't ok - but it's switchable (please read all and not just the things you want to read)! That makes the great difference. And yes, those filters are harmful depending on the individual use case. It took me hours to find the solution after I did the firmware update of the (new) DAC this year, because I faced the same problem as described by the OP of the linked thread above.

Multitone says everything about distortion around 20 Hz.

It starts @20 Hz @5 W.
15 Hz or lower e.g. are AC, too. I have organ music << 20 Hz. I expect those signals to be amplified without any damping and distortion. Just a quick example screen shot of Boellmanns Suite Gothique - Tocata:

Maybe you should consider the enventuality that I know more about about aftersales, electronic systems, amplifiers, sources and the Purifi modules than you.

IOW: your arguments ended. Do you really need that?

 

[boXem]

...
IOW: your arguments ended. Do you really need that?

I need you to understand that my time for arguments with harmchair engineers ended. Again, goodbye.

 

[fpitas]

Hehe, Oh boy I opened Pandora's here, thank you all. A Double Bass Array where I am hoping to reach into the single digits (7-8?), it is based on these modules. In my past experience with ELF/ULF the rotary subwoofer the amp went down to DC as part of the requirement but the operating range of the TRW-17 rotary woofer is 1-20. Here we are trying to lower the floor of these arrays ( from the regular 12hz when running throughout its whole band) through filtering at the highest frequency the planar wavefront can be created, this is a function of how close the subwoofers are to each other. Im keeping them in the 1/4 to 1/3 of the wall dimension range zones.

The client wants to replace the individual 350wpc@4 class a/b with a multichannel class D, but there is little bandwidth Data available on the typical CI multichannel class D amps from Trinnov and Ati. With the new Trinnov MSMC steered planar wavefront based software, these towers lend themselves for single row media room apps. It is a lot easier to do these DBA's in projection cinemas than they are with videowalls. This is what I've come up with: Our 4 10 towers are 14"w x12"d x46"tall. Im hiding the woofers behind an isolated wood lattice cover.

According to Jon Herron in this video the closer you can get those woofers together the higher up in the range the MSMC will operate to somewhere around 100hz ( I think 125hz is the best case scenario with projection), by purposely limiting the woofers to no more than whatever that maximum operable range limit for the planar wave will be, we give it downward headroom to reach below the teens. Thus I am looking for a multichannel rackmount amp with decent power that goes at least down to 8Hz in bandwidth ideally excelling in all low frequencies criteria. Thanks again!

Thanks for the explanation. Looks like boXem can help you out.

 

[Hayabusa]

I'm of the mind I think 2 Ohm or near is the limit and that's why Purifi is rated 2 Ohm and no more. Zero is just crazy anyway.

what has 2 ohm to do with DC?

 

[chris256]

what has 2 ohm to do with DC?

Good question ...

 

[Andysu]

Looking for a class D amp that goes down to DC or thereabouts....​

I don't think you are going to find one. The protection circuitry is so good they protect at that from what I am aware of.

i think i read about another amplifier went down to 0Hz a crown model maybe 1980 or early 1990

i still prefer behringer class d

 

[CINERAMAX]

I settled for this:https://en.elipson.com/product-page/a2700