Circuit designers - cathode follower, or plate fed tone stack?

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cstenger5
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Re: Circuit designers - cathode follower, or plate fed tone stack?

Post by cstenger5 »

Bieworm wrote:
Thu 12/02/21 11:02 am
I disagree. Tweed bassmen, plexis, 2204... all great sounding amps with very good and responsive tone controls IMHO
All have a CF
No argument there whatsoever. I just feel a bit less like I'm missing out, considering my current build is plate driven.
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ewizard
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Re: Circuit designers - cathode follower, or plate fed tone stack?

Post by ewizard »

Keep in mind I did not say unresponsive, just less responsive as compared to anode driven tone stacks. The cathode follower is good at reducing insert loss from tone stacks, which do suck a lot of volume and load down the previous stage a bit. Because they can reduce insertion loss so well, it changes how the tone stack interacts with the rest of the circuit. In my experience, it is less responsive. The bass control has a wide sweep for little change, the mid pot doesn’t suck the mids out quite as much, and the highs stand strong even with generous amounts of cut. This is of course relative to an anode driven tone stack of pretty much identical topology.
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Bieworm
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Re: Circuit designers - cathode follower, or plate fed tone stack?

Post by Bieworm »

ewizard wrote:
Sun 12/05/21 11:49 pm
Keep in mind I did not say unresponsive, just less responsive as compared to anode driven tone stacks. The cathode follower is good at reducing insert loss from tone stacks, which do suck a lot of volume and load down the previous stage a bit. Because they can reduce insertion loss so well, it changes how the tone stack interacts with the rest of the circuit. In my experience, it is less responsive. The bass control has a wide sweep for little change, the mid pot doesn’t suck the mids out quite as much, and the highs stand strong even with generous amounts of cut. This is of course relative to an anode driven tone stack of pretty much identical topology.
Agreed on the brightness that's pretty present, even on low treble settings.. but some like that in an amp (like me)
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Re: Circuit designers - cathode follower, or plate fed tone stack?

Post by ewizard »

I thought I would circle back around this topic, it has been quite some time now, and while the topic went dead, I thought I would take another stab at it.

Having designed a few more amp circuits since my last post, one thing still stands for me, I am not a fan of CF's. I have also learned I like having my mids too, so I don't use conventional tone stacks. But contrary to all that, my newest build has guess what? A cathode follower...

Now, let me clear some things up. No " tone stack " after it, only a Hi-cut filter ( adjustable treble bleed to ground ). My bass controls are pre CF. And I am using a local negative feedback loop around the CF into its driver stage. Similar to a Fender Tweed Super-Amp. I like my mids, so no mid-control is in the works as of yet. So why a CF, and what does this amp do? Well, it sort of does the Dumble thing, but without having 4 gain stages. It is creamy, rich, and it does the clean to breakup thing that is spongy, mid-forward, and smooth. I am on the fence about going with cathode biased, or staying with fixed bias for this amp, I may just do both? I feel that cathode biased would give it some more harmonic character, but may be too raunchy when pushed. I have not tested it yet, but in fixed bias mode, it brings the spank.

What I am getting at is that you just never know where you will get to unless you keep an open mind. While I don't like CF's, there are ways to make them not do the things you don't like, and get a different flavor. In this case, for me, it was a necessary evil and there is a chance this design will be my flagship design ( there is only one at the moment )? I had a client tonight who is a 50-year veteran guitar player, and using my 18-watt design, he said he has never had a better sound!! I find that shocking and flattering, considering my 18-watt design is about as simplified as you can get an 18-watt to be. It is similar in some ways to the Lite iib, except I have a bass control, a cut control and a post phase MV. Ok, so not as simple, but all the major tone controls are not sucking out gain at least. I have seen his amp collection, and he has Marshall Plexis, JCM-2000's and 800's as well as A Diezel Lil Fokker and some other vintage amps. For him to be as stoked about an 18-watt derived design of mine as he is, shocks me. So again, you just never know what will bring the win, if it sounds good it is good. So try it, even if you don't like it normally, you may just find it does what you need...
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