Split Cathode vs Shared with same values

[lgehrig4]

I have a JTM 50 clone that I want to hot rod and the first thing I'm planning on is to bring it closer to JMP 50 spec, starting with the shared cathode on V1. I'd rather not split due to lack of room on the board and was wondering if the lead channel would sound the same if I just changed the values on the shared cathode vs the same values on both sides of the split cathode?

In other words..

shared (0.68uf/820) vs split (0.68uf/820, 0.68uf/820)

I'm assuming it's the same result but I don't know for sure.

p.s. Anyone aware of a layout, preferably Marshall that labels the board components by name? This would be a great reference for researching what the individual components do in the circuit. (ie, cathode follower, bias resistor, etc)

[martin manning]

Starting from shared 820Ω//680n, equivalent separated values would be 1640Ω//340n. If you use 680n on both you will get a mid boost, relatively speaking. Nearest standard values would be 1620Ω and 330n.

[lgehrig4]

Thank you! Do you happen to know if that mid boost you speak of sounds good?

[ChopSauce]

What sounds good to him might not sound good to you, & vice-versa...

You know how cathode bypass caps work? Well that's it!
(U may want to Google that otherwise)

[danman]

This may help you.

http://forum.metropoulos.net/viewtopic.php?f=26&t=15719

The boards changed slightly over the years but this should have the info you need.

[lgehrig4]

What sounds good to him might not sound good to you, & vice-versa...

You know how cathode bypass caps work? Well that's it!
(U may want to Google that otherwise)

I understand what you are saying, but there is no harm in asking for an opinion. Not everything someone says has to be scientifically proven or measurable.

I have an idea how they work but just knowing how that something cuts highs, adds low, boosts mids, etc doesn't alway tell the entire story. Sometimes only the ear can tell and thats why I was asking for his opinion.

[lgehrig4]

This may help you.

http://forum.metropoulos.net/viewtopic.php?f=26&t=15719

The boards changed slightly over the years but this should have the info you need.

Thanks for this! I actually stumbled upon it after posting the question. This is perfect. Exactly what I was looking for.

[lgehrig4]

Found a great video on this

https://www.youtube.com/watch?v=HrkYUPmEUhk

[Roe]

with shared cathode the different triodes affect each other reciprocially. An unmatched tube will give a different result than a matched tube. And signal or noise on one triode affects the other. In my fender ab763 amps I've removed all shared cathodes, reducing noise and bleeding significantly.

[ChopSauce]

Interesting! I even could read about people splitting the cathodes of a push-pull to use mismatched tubes, possibly not of the same type.

What sounds good to him might not sound good to you, & vice-versa...

You know how cathode bypass caps work? Well that's it!
(U may want to Google that otherwise)

I understand what you are saying, but there is no harm in asking for an opinion. Not everything someone says has to be scientifically proven or measurable.

I have an idea how they work but just knowing how that something cuts highs, adds low, boosts mids, etc doesn't alway tell the entire story. Sometimes only the ear can tell and thats why I was asking for his opinion.

Certainly (!) but this first remark was very general and not intended to suggest you shouldn't ask at all! Now I understand that you know much more on the subject that I first thought. I guess nothing beats experiment, though.

[lgehrig4]

Interesting! I even could read about people splitting the cathodes of a push-pull to use mismatched tubes, possibly not of the same type.

What sounds good to him might not sound good to you, & vice-versa...

You know how cathode bypass caps work? Well that's it!
(U may want to Google that otherwise)

I understand what you are saying, but there is no harm in asking for an opinion. Not everything someone says has to be scientifically proven or measurable.

I have an idea how they work but just knowing how that something cuts highs, adds low, boosts mids, etc doesn't alway tell the entire story. Sometimes only the ear can tell and thats why I was asking for his opinion.

Certainly (!) but this first remark was very general and not intended to suggest you shouldn't ask at all! Now I understand that you know much more on the subject that I first thought. I guess nothing beats experiment, though.

I guess I know more than I lead on but I'm still a little nervous to try stuff without asking first. I don't quite trust my judgement yet. For example, today I received some parts to add a Jose Master. I'm using a push/pull pot so I can switch it out and I've never wired one of these before. I'll use my meter to check the resistances but I still won't feel comfortable moving forward until someone tells exactly how to wire it.

Look out for that thread...