madbeanpedals::forum

General => Open Discussion => Topic started by: lrgaraujo on February 06, 2021, 04:40:42 PM

Title: Impedance matching on SS power amp
Post by: lrgaraujo on February 06, 2021, 04:40:42 PM
Hello, everybody!
Hope everyone is doing well!

I messed up the jack in the preamp of my SS combo and I've been using the aux input until I can have it fixed. However, there is an impedance mismatch (aux input impedance is 100k and preamp input impedance is 1M) that I believe is making it sound dull (even if I use a separate preamp).

Will a DI box make it better (I have all the necessary components at home, already)?
Title: Re: Impedance matching on SS power amp
Post by: thomasha on February 06, 2021, 10:52:56 PM
Hi, that seems a huge change for being just an impedance mismatch. A preamp should be enough to drive the power amp.
Which amp is it? Maybe there is something online that we can check to verify what's going on. I would guess the aux input is somewhere still in the preamp, so that if the preamp is bad, aux is partially affected.

Other possibility would be something like in a wah pedal without true bypass, where the circuit sucks part of the signal even when disengaged, and it sounds dull. If the preamp is not working it may be affecting the aux too.
Title: Re: Impedance matching on SS power amp
Post by: jimilee on February 06, 2021, 10:59:40 PM
Quote from: lrgaraujo on February 06, 2021, 04:40:42 PM
Hello, everybody!
Hope everyone is doing well!

I messed up the jack in the preamp of my SS combo and I've been using the aux input until I can have it fixed. However, there is an impedance mismatch (aux input impedance is 100k and preamp input impedance is 1M) that I believe is making it sound dull (even if I use a separate preamp).

Will a DI box make it better (I have all the necessary components at home, already)?

Use those DIY skills to have a look at the jack.
Title: Re: Impedance matching on SS power amp
Post by: lrgaraujo on February 07, 2021, 02:41:00 PM
Quote from: thomasha on February 06, 2021, 10:52:56 PM

Which amp is it? Maybe there is something online that we can check to verify what's going on. I would guess the aux input is somewhere still in the preamp, so that if the preamp is bad, aux is partially affected.

Thanks for the answer, thomasha

I found the schematic and the block diagram. The aux input is right after the tone control, so I'm guessing it shouldn't be affected by the preamp (and the preamp works fine, problem is with the jack).

Quote from: jimilee on February 06, 2021, 10:59:40 PM
Use those DIY skills to have a look at the jack.

It's probably my best guess, but I'm too lazy to open the amp  ;D