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Thoughts on DSP multiamp/attenuator setup?
Thoughts on DSP multiamp/attenuator setup?
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Old 16th May 2019, 01:13 PM   #51
badman is offline badman  United States
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The reason for the standalone unit was to simplify the gear configuration- trying to avoid adding devices!

I do need to figure out some post-DSP attenuation for gain staging- as it stands, I typically need a net voltage gain of 0dB or less throughout the system (high power amps and sensitive speakers in a home setting). The best pre-built options I've seen come from Naiant, properly designed, and with variants for line level, mic level, etc. The 8 position balanced attenuators are one heck of a nice way to add input trimming to an amp, but there are adaptor and cable built-in attenuation options available too.

https://naiant.com/custom_audio_repr...nline-devices/

I'll probably just build my own as it's just 3 resistors per cable and I have the parts for the most part, but the naiant stuff seems well made and is very reasonable.
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Old 20th May 2019, 08:30 AM   #52
KaffiMann is offline KaffiMann  Norway
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Thoughts on DSP multiamp/attenuator setup?
Quote:
Originally Posted by badman View Post
trying to avoid adding devices!
Good luck with that!
Seems you are trying to find some equipment to avoid adding some.... other equipment.

We've all been there.
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Old 21st May 2019, 11:40 AM   #53
mortron is offline mortron  Canada
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I recently came across a cheap used Driverack 260, and am going to use it to figure some stuff out and see where it takes me. I am coming from an Ashly XR2000 analog crossover.

My biggest hang up, which may be similar to something OP is dealing with, is that my power amps do not all have the same gain, and therefore when set up at one volume, once I turn it up, the balance is affected, no?

Is attenuating the input levels on the power amps going to allow gain matching between the amps? My impression was Gain was a bigger concern than wattage. Ya?

Apologies if I'm hijacking or distracting. If so, let me know and I'll start a different thread.
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Old 21st May 2019, 11:48 AM   #54
kipman725 is online now kipman725  United Kingdom
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The DSP I am using (symetrix symnet 8x8) has software controlled gain/attenuators on the input and outputs. With 100dB/1W speakers I don't notice any hum.
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Old 21st May 2019, 01:23 PM   #55
badman is offline badman  United States
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Quote:
Originally Posted by mortron View Post

My biggest hang up, which may be similar to something OP is dealing with, is that my power amps do not all have the same gain, and therefore when set up at one volume, once I turn it up, the balance is affected, no?
Unless they have nonlinear gain (IOW, high distortion), once you balance the input levels and gain for parity, you'll be in good shape. This is absolutely a good place for this conversation!

Quote:
Originally Posted by kipman725 View Post
The DSP I am using (symetrix symnet 8x8) has software controlled gain/attenuators on the input and outputs. With 100dB/1W speakers I don't notice any hum.
The 360 has clipping range controls on input and output, as well as individual output channel balancing levels and a master control in software.

The issue for my application is not expected to be with noise, though naturally that's to be avoided, but I want to be able to ensure that I can use a pre-DSP volume control without causing the A/D converters to have insufficient dynamic range available (Or use a digital volume control pre-digital input). The software attenuation has a decent range to it because of the wordlength headroom in the processing chain, but I tend to listen at a wide range of volume levels. Rarely super high but often super low.

It's really about keeping the preferred, simple UI from the processor or digital source as my volume control interface, and the system flexibility that goes along with that. If I can have that flexibility without performance costs by throwing some resistors on the amp inputs (I could modify them for unity gain but that's a pain if I want to use them in other setups), then that makes good sense to me.

If it matters, I ordered several of the naiant products. Too affordable a quality solution to pass up. I picked up a quad of the 24dB attenuator cables, and a pair of their SPD variable attenuators (it's a small switched resitor network built into a little adaptor, very convenient way to add variable input attenuation). Between those, I should be able to keep my ducks in order, even when working with a variety of amplifier/speaker efficiency combinations. I won't use any output attenuation on the subwoofers, for example, but might need more on the tweeter than the 24dB that the midranges need. The goal is to have as little gain balancing needed within the DSP as possible, as that's digital headroom that's better allocated to input sampling.

I haven't gotten them yet, but expect them sometime in the next week or so, at which point I'll start integrating the Venu and see where it gets me.
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Old 21st May 2019, 03:18 PM   #56
mark100 is offline mark100  United States
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You know, I keep a pair of these around for whenever i have too much speaker sensitivity and amp gain. The switchable attenuation has always let me find a range of digital/analog level control that maintains good gain staging.
Amazon.com: Hosa ATT-448 Input Attenuator, XLR3F to XLR3M: Gateway

I think mine are -10, -20, -30dB....which i like...
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Old 21st May 2019, 08:14 PM   #57
badman is offline badman  United States
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Quote:
Originally Posted by mark100 View Post
You know, I keep a pair of these around for whenever i have too much speaker sensitivity and amp gain. The switchable attenuation has always let me find a range of digital/analog level control that maintains good gain staging.
Amazon.com: Hosa ATT-448 Input Attenuator, XLR3F to XLR3M: Gateway

I think mine are -10, -20, -30dB....which i like...
Those are a great solution! However, for my use, my concern with those is that they're very low impedance, which isn't ideal for the amp input attenuation. The other issue with some attenuators (not necessarily these) is that the attenuators aren't symmetrical- they use an L-pad on just one leg, unbalancing the system and potentially bringing common mode noise along for the ride.

I'm going to use these for cases where 24dB isn't a good match:

https://naiant.com/studio-electronic...ne-attenuator/

The steps offer quite a bit of range, at a more appropriate impedance, and are known to be properly balanced.
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Last edited by badman; 21st May 2019 at 08:18 PM.
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Old 21st May 2019, 08:45 PM   #58
mark100 is offline mark100  United States
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Quote:
Originally Posted by badman View Post

I'm going to use these for cases where 24dB isn't a good match:

VPD variable inline attenuator

The steps offer quite a bit of range, at a more appropriate impedance, and are known to be properly balanced.
Those look really cool...bound to work.

fwiw, and not to be challenging at all ........I think too much attention is given to gain staging / impedance matching / etc ...these days.....those things strike me as finishing details with very little significance ....compared to even basic simple tuning ...
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Old 21st May 2019, 09:15 PM   #59
bentoronto is offline bentoronto  Canada
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Thoughts on DSP multiamp/attenuator setup?
IDIOT'S GUIDE TO MOVING TO DSP ALMOST PAINLESSLY

There are many Behringer DCX2496 on eBay cheap. A million in use. All-singing, all-dancing, does everything. Stand-alone with its own display panel.

Cheap too is a USB to AES box, maybe $35, thereby by-passing the analog DCX input stage that some people think is faulty (without any evidence I've ever seen). But not applicable to the new more modest DCX variant.

If you are a purist, you might want to run you digital section all-bits-on-deck. In that case, you need a cheap ganged volume control at the far-side of the DCX. Cheap.

Works great. You can do all kinds REW tests and fine-tune your EQ in minutes. You'll wonder why you didn't do it a decade earlier.

Passive crossovers make no sense in theory or in practice, unless you are crossing over pure resistances and have no sympathy for amp loads.

B.
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Last edited by bentoronto; 21st May 2019 at 09:20 PM.
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Old 22nd May 2019, 12:36 AM   #60
badman is offline badman  United States
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Quote:
Originally Posted by mark100 View Post
Those look really cool...bound to work.

fwiw, and not to be challenging at all ........I think too much attention is given to gain staging / impedance matching / etc ...these days.....those things strike me as finishing details with very little significance ....compared to even basic simple tuning ...
That's perfectly fair. As a counterpoint, however- I care about the details, and the little stuff does matter, but perhaps also important is that it's additive. Better amps of similar power don't matter as much as a better crossover, but their improvements stack on top of the better crossover improvements. I have invested enough in the small stuff to put the effort into the OTHER small stuff. Low diffraction cabinets, tweaked drivers, etc. I don't want to make overstated golden ear claims like a schmuck but the little stuff matters to me.
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