Voltage reading question

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mlundy57

Voltage reading question
« on: 9 Dec 2018, 08:48 pm »
Is there a safe way to measure the voltage on different channels of a preamp to see if the voltage output is the same?

The situation is this: Using the front channels and surround back channels of an AVR to bi-amp Wedgies and servo subs. The front channel preamp outputs are going to a power amp that is feeding the Wedgies. The Surround Back channel preamp outputs are going to the A370 amps.

The issue: there is a 23dB difference between the Wedgie and the sub, with the sub lower, (volume control on sub is maxed out) when each are checked close to the drivers and about 20dB difference at the listening position.

I'm wondering if there is a voltage difference between the front and surround back channels in the AVR that might account for SPL differences.

Thanks,

Mike


HAL

  • Industry Contributor
  • Posts: 4350
Re: Voltage reading question
« Reply #1 on: 10 Dec 2018, 12:54 am »
Mike,
If you have a test CD with test tones on it and a AC volt meter you can get an idea of the level offsets.

Disconnect all the preamp outputs and test each one with the same test tone. 

From what I remember of surround processors, the main front and rear surround channels do not have the same levels, as it depends on the decoded content from multichannel source material. 

You might be better off with a Y connection splitting the main L-R outputs to both amps for the Wedgies and A370's.

mlundy57

Re: Voltage reading question
« Reply #2 on: 10 Dec 2018, 01:03 am »
Rich,

I have both so I can do the check.

The AVR has the ability to assign the surround back channels to the front main channels for bi-amping. When in this configuration, the surround back channels get the same signal as the front channels and are supposed to be at the same level. If the levels are the same, the AVR isn’t the problem. If different then it’s at least part of the problem.

Thanks,

Mike

MarvinTheMartian

  • Jr. Member
  • Posts: 92
Re: Voltage reading question
« Reply #3 on: 11 Dec 2018, 01:00 am »
Mike: Swap the RCA cables to the bass servo amp and the wedge amps, if the level mismatch follows, the issue is somewhere in your AVR.
Check the internal channel levels in your AVR, surround level settings may still apply even in front channel bi-amp mode.

Which AVR are you using?
Shawn

mlundy57

Re: Voltage reading question
« Reply #4 on: 11 Dec 2018, 01:17 am »
Mike: Swap the RCA cables to the bass servo amp and the wedge amps, if the level mismatch follows, the issue is somewhere in your AVR.
Check the internal channel levels in your AVR, surround level settings may still apply even in front channel bi-amp mode.

Which AVR are you using?
Shawn

Shawn,

That would be a simplier first step. Unfortunately, when in bi-amp mode (both main and surround back channels assigned to front main) the surround back channel level adjustment is notavailable.

This is an older Onkyo AVR. The ability to adjust surround back channels separately from front main when in bi-amp mode also is not available on my much newer Marantz SR-7009 AVR.

That would make it too easy

Mike

Captainhemo

Re: Voltage reading question
« Reply #5 on: 11 Dec 2018, 05:44 pm »
Maybe I'm missing something  but can't you  just  swap the  Wedgies  amp to linked  surround preouts and  run the subs off the main /front pre outs... , adjust the  volume down slightly on the  A370's  to match up  withthe  wedgies  ?

jay