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CAT SL-1 clone DIY project

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avelasco

Member
Joined 2020
#1
Hi, I recently bought a clone of the CAT SL-1 and this weekend I plan to start the assembly, since I did not find the schematics I decided to make it.
I would like to ask for your advice on two issues
1.- Is the diagram correct? Does it have serious bugs?
2. Is there any advice you could give me to improve it


Diagrama.jpg - Google Drive
 
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#9
A good case can be made for keeping the cathode stop resistor in circuit. Cathode followers have a lot of feedback, and a pole at fairly high frequency. This is equivalent to an inductive output impedance, which will try to resonate with capacitive loads. Too many cathode followers are marginally stable, and parasitics aren't unknown. The cathode stop should be mounted right at the socket pin, like a grid stop.


All good fortune,
Chris
 
#12
CAT SL-1 clone from web. I have never built it so I don't know much.
 

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#19
A 47R resistor in the second stage is so small as to be unimportant. It could be removed (along with the coupling cap and 1M grid resistor) with no effect, or it could be increased to take some advantage of it.


I'd be tempted to re-arrange the B+ supply so that the cathode follower was fed from the same decoupling spot as the second stage, to minimize supply interactions. (Second stage output signal is developed across the upper ECC83 half. Cathode follower input is between grid and anode. These should be connected together as well as possible.)


As rayma has pointed out, output stage cathode stop gives some loss, so could be minimized. A single resistor, mounted physically close to the socket, should do. Could be smaller value, maybe half?


This circuit has a lot of gain. 26dB at least. Do you really want this much?


All good fortune,
Chris


Edit: I see the 47R is a typo. So ignore.
 
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#20
Chris Hornbeck said:
This circuit has a lot of gain. 26dB at least. Do you really want this much?
Edit: I see the 47R is a typo. So ignore.
Click to expand...

As I can see from the simulations you are right, it has a lot of gain

This weekend I will build the preamp and I can report my findings

I chose this board because it will be my first tube DIY project and learn some thing new.


Chris Hornbeck said:
I'd be tempted to re-arrange the B+ supply so that the cathode follower was fed from the same decoupling spot as the second stage, to minimize supply interactions. (Second stage output signal is developed across the upper ECC83 half. Cathode follower input is between grid and anode. These should be connected together as well as possible.)


As rayma has pointed out, output stage cathode stop gives some loss, so could be minimized. A single resistor, mounted physically close to the socket, should do. Could be smaller value, maybe half?
.
Click to expand...

It would be a lot of annoyance if you could explain these points to me in more detail?
I am definitely willing to make modifications to improve the design, but I am not an expert, if you have patience I can implement them in the diagram

Thanks
 
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