Why does my amp sound worse than an AC30CC?!

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XgamerGt03
Posts: 112
Joined: Fri Feb 13, 2009 6:03 pm

Re: Why does my amp sound worse than an AC30CC?!

Post by XgamerGt03 »

If I'm not mistaken the Cathode follower in the Vox Top Boost Circuit can draw quite a bit of grid current during operation.

This can cause a more compressed and punchy sound from what people say. I personally like the sound of a cathode follower driven tone stack with a low value cathode resistor.
tubeswell
Posts: 2337
Joined: Thu Mar 27, 2008 6:42 am
Location: Wellington. NZ

Re: Why does my amp sound worse than an AC30CC?!

Post by tubeswell »

XgamerGt03 wrote:If I'm not mistaken the Cathode follower in the Vox Top Boost Circuit can draw quite a bit of grid current during operation.

This can cause a more compressed and punchy sound from what people say. I personally like the sound of a cathode follower driven tone stack with a low value cathode resistor.
Yes various AC30 over the years with the DC-coupled pair driving the tonestack have ~56k-68k cathode resistor on the CF stage, which causes more current to be 'stolen' from the inverting stage's plate resistor (than in your typical 5F6A DC-coupled pair). This results in more non-linear amplification at the inverting stage's plate, which equals more 'compression' in the sound.
He who dies with the most tubes... wins
Gaz
Posts: 1146
Joined: Tue Aug 25, 2009 6:27 am

Re: Why does my amp sound worse than an AC30CC?!

Post by Gaz »

I don't know if the compression effect is really happening with so little preamp gain, and I think it's been exaggerated since Merlin's book came out. I've also never thought of compression equaling 'punch', which is rather a dynamic sound and clear sound.

After much more A/Bing, I decided to go with Vox stack, but with the 10k resistor grounded, rather than across the bass pot. This get rid of the weird mid scoop at the top of the bass control's rotation.
tubeswell
Posts: 2337
Joined: Thu Mar 27, 2008 6:42 am
Location: Wellington. NZ

Re: Why does my amp sound worse than an AC30CC?!

Post by tubeswell »

You don't notice the compression effect until you start to really crank it
He who dies with the most tubes... wins
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