circuit board layout from a schematic

[Terry]

That schematic is weird, do the lines that cross over join together?

That had me going for a while too Mike, until I realised that the few lines which don't connect have a small break in one of them.

Even knowing that makes it difficult to follow, though, as the brain keeps telling you that the other points are not joined!

At least the second schematic has conventional dots on the junctions which makes a great improvement in clarity.

[Bushbaby]

This will be a very novice question here - can I swap out the ECC82 for an ECC83? The latter is higher gain and draws less current so I am led to believe.

Best Regards

[ppppenguin]

I was confused by the schematic at first. Then I remembered that there was an old and now neglected convention. Shown as 3 in my sketch. Your schematic uses crossing wires as joining, something that looks ambiguous.

Modern practice is to use 1. in my sketch. A lot of older diagrams use 2. The 3rd version is rare.

ECC82 and ECC83 (and ECC81) are not interchangeable. They have very different characteristics. It might be possible to change a few resistor values to make a circuit designed for one work with the other, but not always very well.

ECC81: Mainly for RF/IF
ECC82: Mainly for pulses and switching
ECC83: Mainly for low noise audio

[Crackle]

I have experimented with swapping various ECC8x valves in guitar amp circuits. They will work to an extent. The ECC81 was sometimes used in the phase splitter position, an ECC83 worked just as well.
So long as they have a centre tap and are pin compatible, which the 81, 82 & 83 are, they should work.
You have to remember this is a guitar amp so its not science but art, you need to experiment and make your own unique sounding distortion, in order to get a guitar to really sing. (I dont play an instrument but I like experimenting)
Mike

[Bushbaby]

Mike
Would these just be a straight swap from 81 to 82 to 83? Im concerned that I dont want to overpower any of the components. I really dont recall, apart from the modern very low output Marshall amps (1 watt amps that use ECC82's) anything other than ECC83s.

Thanks

[Crackle]

I didnt change any components we just swapped the valves to see what effect it had. I cant say what sort of long term effect it would have on the valve, but they are only working at low power anyway. At audio frequencies the ECC83 would give more gain in the preamp stages, but I seemed to think it had only a minor boost in gain in the phase splitter stage, I think, it is quite a while ago now when we were experimenting with Sams JCM800 Marshall head.
But I seem to remember the best improvement in sound (for home use according to Sam) was when the amp was being driven hard at over 70 watts, into an 8 ohm power resistor on a massive heat sink, and with a 68 ohm and 6.8 ohm voltage divider driving the speaker.
Mike

[pwdrive]

Using the values in the schematic do a load line for the ECC82 and then one for an ECC83, should be able to get an idea of what's what from that.

Lawrence.

[Bushbaby]

Lawrence
I feel terrible about this - I haven't a clue how to go about doing this- my degree in Chemistry and Masters in Environmental management for business isn't helping me in the slightest here! As I am rapidly closing toward full retirement and I am going to ensure to take some electronic classes to bring myself up to speed!!

Thanks

Rob

[pwdrive]

Here you go:

http://www.valvewizard.co.uk/Common_Gain_Stage.pdf

Lawrence.

[Bushbaby]

Thanks Lawrence

Regards