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TOPIC: Preamp trim/volume for correct DDRC88 input gain?

Preamp trim/volume for correct DDRC88 input gain? 3 months 4 weeks ago #26983

  • ahuesjp
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Hello everyone,

This is my first post in this forum, and I am fairly new to the subject of matching gain. I have tried to learn as much as I could over the last week before asking this question, but I apologize if I am just confused as a newbie.

I recently got a DDRC88A unit, and I am trying to do my homework before I install it into my sound system this weekend. I am trying to determine the correct gain, pre-amp trim, and volume settings to use with between my pre-amp, amplifiers, and the DDRC-88A unit.

On the DDR88A output side to the amplifiers, the gain procedure and adjustments are fairly clear, and documented in the DDRC88A manual and the Gain Application Note in the minidsp website.

However, I am unclear on the DDRC88A input side. The only guidance given is to ensure the output from the source (preamp) doesn't go over the max DDRC88A input setting, but there is no guidance on how to measure if you are going over the limit.

My pre-amplifier is the Emotiva UMC-200, and it only has unbalanced line out outputs. While the manual doesn't list the line-out voltage specs, the Audioholics review measured that it can output 4V RMS (at 0.1% THD). Please see: www.audioholics.com/av-preamp-processor-...ocessor-measurements.

If I understand things correctly, my pre-amp has more than enough output to drive DDRC88A inputs into clipping. Therefore, the correct DDRC88A input sensitivity setting is 2V RMS unbalanced line-in (the max). But I should also limit (via trim & volume) the pre-amp output to ensure it doesn't go over 2V RMS when outputing the maximum possible signal (full scale?).

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Question #1:
How do I calculate the correct pre-amp trim and maximum volume to use with the DDRC-88A?

Prior to the DDRC-88A, I had a MiniDSP 2x4, and I used the community tutorial for connecting multiple subs using it: www.minidsp.com/support/community-powere...e-subs-with-audyssey. It outlines the procedure for setting the pre-amp trim using REW tone generator, and a voltmeter to prevent input clipping on the minidsp 2x4. I "guess" that the procedure uses a 60Hz tone at -3 dBFS because the tutorial is for the sub-channel. Can I follow the same procedure to set the trim for the speaker channels? Can I use the same tone generator settings for the speaker channels. Otherwise, what tone generator settings should I use?

I also wrote my pre-amp vendor (Emotiva), and they send me the volume setting for 0 dB unity gain (input->output) through the pre-amp, which is about 75% of the volume range. As the pre-amp doesn't have a "reference" setting (as that depends on the Amp & Speakers), this is the volume that I used in the procedure above. Is that correct?

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Question #2:
Which equipment do you recommend I use to control/adjust the system volume, the DDRC-88A or my pre-amp?

My pre-amp has an analog volume control, which should have no lost of resolution. But the DDRC-88A will digitize the signal anyway, and that might negate the benefit to using the analog volume control.

If the volume should be controlled by the DDRC-88A, what volume setting should I use in the pre-amp? I assume this should be the volume used in question #1, to ensure the maximum possible signal doesn't produce a DDRC-88A input above 2V RMS. Is this correct?

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Again, I apologize if I am confused as a newbie. But I would appreciate your review of my logic, and any detailed answers/feedback/guidance that you guys could give me.

Thank you,

Juan Pablo Ahues-Vasquez
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Preamp trim/volume for correct DDRC88 input gain? 3 months 3 weeks ago #27173

  • devteam
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Hello

On the current DDRC-88A software, there isn't a way to do monitoring of that input signal. It will change soon with an upcoming release in few weeks. For the time being:
Question 1: Do 6dB less and you'll be 1/2 of that 4Vrms. Also note that max output are 100% level. very very rarely would a device run at max output. By default, on 2vrms, on a normal listening level, you'll be fine.

Question 2: The master volume control is setup when you do the Dirac measurement (i.e. master level to achieve correct reading). Check the user manual for more details.

These are minor details I think.. Don't worry too much as most people don't need to worry about it. Launch your Dirac Live software, start learning and let us know if any issues. :-)

DevTeam
MiniDSP, building a DIY DSP community one board at a time.
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Preamp trim/volume for correct DDRC88 input gain? 2 months 2 weeks ago #27842

Hello,
I am very interested in this FW!
Is there any release date? Will it a feature only for the BM version?

Kind regards from a happy customer :-)
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Preamp trim/volume for correct DDRC88 input gain? 2 months 1 week ago #28013

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@ Michael

If the "Gods of firmware" are nice to us, we're hoping to release it in 1week from now. :-)
Thanks for your patience.

Devteam
MiniDSP, building a DIY DSP community one board at a time.
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