Jump to content
Sign in to follow this  
pfsmith0

HD500 Input Z

Recommended Posts

I took my HD500 into the lab to measure it's input impedance to see if it was "real" or just an simulated/emulated effect. Summary: it is a real resistor.

 

Details: I used an Audio Precision APx525 to generate a 100mV RMS signal at 100 Hz (because 1kHz caused too much cross-coupling at the higher impedance settings of 1M and 3.5M) with a 20 ohm output impedance (which is negligible). I switch in various series resistors until the signal out of the HD500 into the APx525 (either XLR out, 1/4" out, or SPDIF, it made no difference) dropped 6dB. Only the first FX block was installed in the HD500- the Studio EQ set to its default settings. The results are below:

 

HD500 Input Z selected / Input Z measured

22k / 22.21k

32k / 32.03k

70k / 69.8k

90k / 90.1k

136k / 136.5k

230k / 232k

1M / 999k

3.5M / 4.57M (noisier measurement than the others)

 

So what?

 

Well, the HD500 input Z interacts with humbucker and single-coil pickups in an identical way that amps and FX boxes do. Humbuckers generally like (or require, depending on your point of view) higher impedances than single-coil pickups. Also, if you're driving the HD500 from a source w/o pickups, such as another FX box or a wireless receiver, then input Z selection should have no impact on your tone (as long as the box can drive the selected input Z). Generally, lower input Z offers lower noise but is harder to drive (prone to amplitude loss or more distortion).

  • Upvote 4

Share this post


Link to post
Share on other sites

Really nice to know these things, thanks for doing all that testing. You're the man!! You Rock!!

Share this post


Link to post
Share on other sites

Would be interesting to see if front-ending the input with a solid pre-amp would generally improve the tone dynamics

achieved at the output. Unfortunately, amongst the gear that I have, a dedicated pre-amp isn't one of them.

Could be possible tapping into the pre-amp of any guitar amplifier tho, if it has an FX Loop, that is.

 

Good post. ;)

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

×
×
  • Create New...