Welcome, Guest
Username: Password: Remember me
NOTE: This is a "Community" forum. Please be mindful that community members are here to help as part of a community effort. We therefore appreciate your effort in keeping this forum a happy place!

If you have a specific issue (e.g. hardware, failure) and want help from our support team, please use our tech support portal (Support menu - > Contact Us).
Thanks a lot of your help in making a better community.

TOPIC: Input level RCA for Minidsp SHD

Input level RCA for Minidsp SHD 3 weeks 6 days ago #55098

  • robertofabbri
  • robertofabbri's Avatar
  • Offline
  • Junior Boarder
  • Posts: 21
  • Thank you received: 5
  • Karma: 0
Hello,

I'm trying to figure out what the proper gain level should be on my phono setup, before the signal enters in the RCA input of my Minidsp SHD for the A/D conversion.

Actually, my current setup has a 0,3 mV cartridge, paired with a +66 dB gain phono.
These two figures should produce a nominal output of almost 600 mV.

Anyway with music signal, is not infrequent to deal with recorded music showing a +XX dB output. Think about (for example) at the tracking test of HiFi News Test Record, they start from +12dB until +18dB. A +12dB added would increase the phono output until almost 2,5V.

Now, I see from the datasheet that the RCA analog inputs of the SHD have a 2V sensitivity. Should I assume that any signal above that level would produce clipping? I am asking this because here and there I'm hearing what I think is a tad of distortion, but after a lot of efforts, still I cannot address the cause (my rig is alright).
The administrator has disabled public write access.

Input level RCA for Minidsp SHD 3 weeks 6 days ago #55099

  • entripy
  • entripy's Avatar
  • Online
  • Gold Boarder
  • Posts: 313
  • Thank you received: 88
  • Karma: 6
It is actually 2V RMS, which should cope with peaks up to 2.8V.

It will clip above that level. The good news is that you can purchase inline RCA attenuators to attentuate hot signals.

In most signal chains there are usually so many imprecise specifications you can often get far more or far less out than the numbers suggest. Is that 0.3mV cartridge sensitivity the maximum output? the guaranteed mininum that could be higher? RMS or peak?
What are the error margins on the specifications? Is that 66dB +/-1dB or +/-3dB?

The specification numbers may give you a clue that you could be close to clipping but they just aren't useful enough to rely on for any actual calculations.

I think you probably either need to just fit inline attenuators or measure actual peak voltages.
Last Edit: 3 weeks 6 days ago by entripy. Reason: fix typo
The administrator has disabled public write access.

Input level RCA for Minidsp SHD 3 weeks 6 days ago #55100

  • rodrigaj
  • rodrigaj's Avatar
  • Offline
  • Senior Boarder
  • Posts: 78
  • Thank you received: 21
  • Karma: 0
I have a Benz L2 which is similarly spec'd at 0.3mV. I have a Lundahl SUT with a 20dB gain (1:10 SUT ratio) and an Avid Pulsus set at 48dB for a total gain of 68dB. This connects directly to my SHD RCA inputs.

I only listen to classical music exclusively and never get any clipping distortion.

If you are certain that your LP's are not the problem, that your cartridge and tone arm are not the problem, compliance, ...etc., then as @entripy suggest, RCA inline attenuators would be a good solution. Or, if the clipping is infrequent, live with it and accept the limitations of the LP medium. Many recordings from the late 50's - early 60's, have some distortion from one groove to another, as you approach the inner grooves toward the label, incompatible RIAA curves, etc...

Personally, the whole vinyl rebirth is a mystery to me. I still try to listen to at least one LP per listening session but it is mostly for nostalgia.
The administrator has disabled public write access.

Input level RCA for Minidsp SHD 3 weeks 6 days ago #55101

  • rodrigaj
  • rodrigaj's Avatar
  • Offline
  • Senior Boarder
  • Posts: 78
  • Thank you received: 21
  • Karma: 0
I forgot to mention that the 0.3v spec, as entripy suggest is a nominal value, that is usually spec'd at some velocity. For example, my Benz L2 is spec'd at 0.3v at 3.54cm/s. What its output is at different velocities is unknown.
The administrator has disabled public write access.
Moderators: devteam