Amp internals

[ICBM]

I know people like to see tidy wiring but in fact having every single wire cable tied every inch can make an amp a pain in the arse to work on, especially if you need to work on it while it's running.

+1

One of the nice things about many PCB amps is that if you're careful, it's possible to run the amp with the PCB out so you can troubleshoot both sides of it - although getting there can take a bit of time!

As Misty pointed out worse things are PCB mounted valve bases, PCB mounted pots, valves hanging upside down with no restraints, 1\4 sockets used for speakers, crap impendence selectors which are so bad they have an impedence of their own.

Actually inadequately-rated/supported PCB-mounted power resistors cause more problems than all those put together in my experience - with the exception of old impedance selectors which can be a blown transformer waiting to happen...

PCB-mounted preamp valve sockets are never an issue unless they're the junk white plastic ones used by Marshall, Trace Elliot and a few others in the 90s, which actually melted and shrank! The modern brown ones you find in anything from an Epiphone to a Mesa are fine. With PCB-mounted power valve sockets the usual cause of problems is arcing around the PCB traces, rather than a fault in the socket itself. Even this could be due to the board getting cooked by the heat and becoming conductive, so it's more an issue of board quality than the socket.

I know we use things like 1\4 jacks and kettle leads on amps for legacy reasons but any new decent design wouldn't.

What's wrong with kettle leads? Apart from the fact that there is no physical retention so they can get tugged out.

I agree 1/4" sockets shouldn't really be used for speakers, mainly because musicians will mix them up with guitar cables, but at up to 20W or so it barely matters, and as long as you use proper speaker cables, not at up to 100W (at least into 8 or 16 ohms). Beyond that the connector rating does come into it, which is why Speakons should be the standard for bass amps of greater power and often 4-ohm loads.

[cacofonix]

Ribbon cables. Stick to PC's with them, IMHO, and even then...


I had to replace one in my little big muff Pi. Every time I moved the PCB, which I had to because one of the ribbon connectors had snapped, another snapped.

I eventually replaced the lot with decent linking wire. Probably more than the pedal was worth, but I now know it will outlast the zombie apocalypse.

[Danny1969]

+1


What's wrong with kettle leads? Apart from the fact that there is no physical retention so they can get tugged out.

I agree 1/4" sockets shouldn't really be used for speakers, mainly because musicians will mix them up with guitar cables, but at up to 20W or so it barely matters, and as long as you use proper speaker cables, not at up to 100W (at least into 8 or 16 ohms). Beyond that the connector rating does come into it, which is why Speakons should be the standard for bass amps of greater power and often 4-ohm loads.

I don't like kettle leads for gigging equipment because there's nothing to lock it in ... which means it might not be pushed all the way home which can cause arch'ing, or it might fall out. The Neutrik Powercon locking mains connector is much better and fits a standard 30mm cutout.

My ideal amp would have XLR connectors for all signal, Speakon for speakers, Powercon for mains and no connectors on rear at all .... as we almost always gig with the amp close to a wall so you can't see behind the amp let alone get to anything : )

[cacofonix]

Cornfords and matamps also look well made. There's one of the hurricane somewhere, and that looks nice too.

Trouble with matamps is lack of consistency in sound, so I'm told, because the maker is a tinkerer, so every one is different.

Still, get a good one and they absolutely rock. I posted a link in Casper's 1224 sale thread, with one really singing.

[ICBM]

I don't like kettle leads for gigging equipment because there's nothing to lock it in ... which means it might not be pushed all the way home which can cause arch'ing, or it might fall out. The Neutrik Powercon locking mains connector is much better and fits a standard 30mm cutout.

A good tight-fitting IEC is actually quite hard to pull out. I'm not keen on non-standard connectors (no matter how good) because you have to carry spares of everything. At least with a "kettle" lead you can pretty much always find one, even if it means borrowing the one from a kettle . Same with 1/4" speaker cables - at a push, you can get away with a guitar cable if you have to.

Does the Powercon fit in the old Bulgin cut-out? If so that might be another option for upgrading old amps.

My ideal amp would have XLR connectors for all signal, Speakon for speakers, Powercon for mains and no connectors on rear at all .... as we almost always gig with the amp close to a wall so you can't see behind the amp let alone get to anything : )

I like signal inputs on the front, but not much else. I certainly wouldn't want power and speaker sockets there, when the other ends of the cables always go to things round the back! I always connect those first when setting up (as you should), so if you then want to move the amp back to against the wall, you're just protecting them from getting tugged.

[DannyP]

Here's one I made:

[ecc83]

Whilst it would seem ideal to have such solid "pro" mains and speaker connectors, in practice average Joe gitist is not going to thank you for them and NOT buy the product!

I agree with ICBM . IEC plugs are usually firm enough and if you have a 100watter atop a stack, surely better the lead comes out than the amp brains someone!

Speaker jacks in my experience up to 200watts are well able to handle what is afterall a very intermittant signal (I do agree tho that huge, 2R bass rigs need better). If there were significant losses in jack I would see evidence of overheating? I do not.

And yeah! Tangling up unbalanced input and output leads sounds like a sure fire route to instability to me!

Dave.

[jpfamps]

And here's inside one of ours.

[Danny1969]

Whilst it would seem ideal to have such solid "pro" mains and speaker connectors, in practice average Joe gitist is not going to thank you for them and NOT buy the product!

I agree with ICBM . IEC plugs are usually firm enough and if you have a 100watter atop a stack, surely better the lead comes out than the amp brains someone!

Speaker jacks in my experience up to 200watts are well able to handle what is afterall a very intermittant signal (I do agree tho that huge, 2R bass rigs need better). If there were significant losses in jack I would see evidence of overheating? I do not.

And yeah! Tangling up unbalanced input and output leads sounds like a sure fire route to instability to me!

Dave.

A locking Speakon mains connector is just a more professional way of ensuring it won't work loose due to heavy vibration. Very common on profession PA kit so just another common lead to me

A 1\4 jack and socket is a terrible design for speaker and amp coupling because just the weight of the cable can cause problems if the socket is cheaply made. Also because both ends are male it's very easy to short out. And you can accidently plug the output of an amp into something expecting signal level ... like an effects unit! All in all it's the worse possible type of moden connector to use to connect amps to speakers

Never seen any balanced in's or outs on any guitar amp so not sure what you mean there ?

[Dadave]