Welcome, Guest. Please login or register.

September 30, 2020, 03:09:22 PM

Login with username, password and session length

Recent Posts

 

Author Topic: Trying to build a bass preamp for a class D module.  (Read 3862 times)

Superfuzz

  • Regular
  • **
  • Posts: 21
  • Chip Points: 0
    • View Profile
Trying to build a bass preamp for a class D module.
« on: October 14, 2016, 05:34:41 AM »
Hi there, I'm basically an FX pedal builder but lately I developed a lot of preamps ideas so I moved on amps. (well I'm trying to)

So now, I'm kinda stuck in this situation:

I designed a bass preamp, it's an idea of mine from start to finish and I'm very very happy on how it sounds when I try it on the PA of my 400w Ashdown. The whole thing was meant to be placed in a box with a connex Class D module wich doubles also as regulated power supply but, as I play it (even at very low master levels) the board goes into protection and I must restart it.

I contacted Connex and they told me that it goes into protection with every signal bigger than 1.5V RMS and it supports 4V p-p maximum. I know those are the standard values for line-in signal. Bass/guitars preamps anyway are always stronger than this and that's how I minded mine. I've tried to clip my signal with everythin, even with German diodes, but it still seems to much for the Connex.

Is there some kind of rule I'm missing? Or I should buy/build a whole different kind of power amp?


Thank you for any kind of help,

Ciao!
« Last Edit: October 14, 2016, 05:36:25 AM by Superfuzz »

tonyharker

  • Elite
  • ****
  • Posts: 149
  • Chip Points: 19
    • View Profile
Re: Trying to build a bass preamp for a class D module.
« Reply #1 on: October 14, 2016, 06:16:23 AM »
Just turn the volume down.

phatt

  • Legendary
  • ******
  • Posts: 2137
  • Chip Points: 261
    • View Profile
Re: Trying to build a bass preamp for a class D module.
« Reply #2 on: October 14, 2016, 07:57:47 AM »
Maybe a compressor improve the outcome?
Phil.

Superfuzz

  • Regular
  • **
  • Posts: 21
  • Chip Points: 0
    • View Profile
Re: Trying to build a bass preamp for a class D module.
« Reply #3 on: October 14, 2016, 08:50:20 AM »
The problem is that  it stops  even at 1/4 of the  volume..The preamp is really "old school" ,  something beetween an old peavey and a sunn..It even has a sort of distortion inside.. 8) for sure is bit brutal..
« Last Edit: October 14, 2016, 04:56:13 PM by Superfuzz »

phatt

  • Legendary
  • ******
  • Posts: 2137
  • Chip Points: 261
    • View Profile
Re: Trying to build a bass preamp for a class D module.
« Reply #4 on: October 14, 2016, 11:12:45 PM »
You could try a simple voltage divider at the output of your preamp.
If the volume control is at the end of your preamp and it's say 100k pot then change it to a 10k pot, that will limit the maximum swing. or just bridge a 10~20k resistor across the existing volume pot.
Phil.

Superfuzz

  • Regular
  • **
  • Posts: 21
  • Chip Points: 0
    • View Profile
Re: Trying to build a bass preamp for a class D module.
« Reply #5 on: October 16, 2016, 04:33:21 PM »
You could try a simple voltage divider at the output of your preamp.
If the volume control is at the end of your preamp and it's say 100k pot then change it to a 10k pot, that will limit the maximum swing. or just bridge a 10~20k resistor across the existing volume pot.
Phil.
This partially answers why it was completely unusable when I initially put a buffer after the master pot (wich actually is 100k indeed).
After I removed the buffer I went where I'm now, 1/4 of the travel of the pot. Now I got to check it with a 10k pot ;).

There's a reason of why shunting the signal down with diodes didn't worked in my case?

Thanks!

Superfuzz

  • Regular
  • **
  • Posts: 21
  • Chip Points: 0
    • View Profile
Re: Trying to build a bass preamp for a class D module.
« Reply #6 on: October 19, 2016, 05:09:02 AM »
Ok it worked a bit better, but it still cuts out..I think I'm goin to throw away that power amp..it's not enough for real bass.

J M Fahey

  • SSGuitar Global Mod
  • Legendary
  • ****
  • Posts: 4142
  • Chip Points: 429
    • View Profile
Re: Trying to build a bass preamp for a class D module.
« Reply #7 on: October 21, 2016, 08:28:51 PM »
*Which*  Connex module is it?
How is it fed?
Please detail power amp model, power supply, if possible a link to that data, it canĀ“t get into protect just because signal overdrives it, any usabe amp module must keep working even with +20dB overdrive, just clip horribly but instantly recovering when signal level is back to normal, you must have ome other problem.

I suspect your power supply can not feed that amp at full power  and *the supply*  shuts off.