Amp internals

[ESBlonde]

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 ?

1/4" jacks were telephone technology. Back in the early days of electric guitars and combination amplifiers the 1/4" jack seemed suitable for guitar signal compared to the other common alternatives at the time. Pushing speaker level signal through the microscopic contact area is a big no no and that's why people started to use XLR instead of 1/4" jack on speakers in the late 70s. The Speakon connector is a dramatic improvement although given the massive power capabilities of some modern PA Power amps there will soon need to be another common solution. Still it's not as if we guitarists aren't able to embrace new things rather than play 50+ year old designs of... oh hang on.

[jpfamps]

Wienbrock?

[jpfamps]

I don't have any real issues with 1/4" jacks for guitar leads; this is a good job as I expect you would have trouble getting the market to change this now.

I actually think it's a good idea to use a connector that isn't locking as a guitar lead, especially if you play in a band with clumsy horn players................

The same goes for IEC leads. I like the fact they will detach if tripped over.

Speakon connectors are definitely a step in the right direction for loudspeakers, however at the moment they are very much confined to high power amps.

For guitar and bass amp to speaker, I think a locking connector is fine, as the wires should be short and not running across the floor.

[ecc83]

I think a little sense and reason is needed re speaker jacks on guitar amps (I would not suggest them for hi fi!)

Ok, they might be the "best" but Neutrik rate their 1/4 jacks at 3A and yes that is but 36W for a 4 Ohm load (135W for 15R) but as I said before, guitar signals are not continuous. In any event Ns quote contact resistance as 10milliOhms, allow a cheaper product to be 10x worse, a 4R speaker has a DC resistance of about 2.6R and and no valve guitar amp will be close to an Ohm. So what is going to get hottest here?

FCS the tiny, puny contact in an RJ45 jack is rated at 1.5amps!

Then, no matter how big the contact (unless they are precision lapped) area only a microscopic "peak" will actually be carrying the current. It seem to me that it is the mass of copper sinking the heat away from the contact point that is important. Look at the contact area of a 13A socket, yes there are two per pin but no bigger than a jack contact and rated at 5times the current. Much heavier gauge metal however.

Cheap jacks? Twas ever thus, don't go cheap! Most of you I guess do not remember the cheap 13A PTs that caught fire! Or the ones that de-natured and left the live pin in place!

Dave.

[ManWithoutSkin]

Sorry if this is a stupid question, but could someone with knowledge of circuits like ecc83 or IBCM just take the chassis off an amp or look at a picture in detail, look at the circuit and then copy it and make they're own amp thats exactly the same?

[monquixote]

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 : )

You can buy locking IEC cables: http://www.misco.co.uk/productinfo/p...uctCode=158484

You can also get locking IEC sockets with little metal cages that drop over the plug.

I've used them in the past, but I prefer non locking for amps as it's better to pull the power out of your head than drop it on the floor.

[Sir Axeman]

My amp...you'll never guess what it is!


pretty tidy eh? Some of those in that link were a real hotch potch!

[ecc83]

Sorry if this is a stupid question, but could someone with knowledge of circuits like ecc83 or IBCM just take the chassis off an amp or look at a picture in detail, look at the circuit and then copy it and make they're own amp thats exactly the same?

Not a stupid question at all and the answer is yes, it is not only possible it is/has been done since time immoral! Called "reverse engineering" if you want the polite phrase but unless you intend to rip off and market the "Blenkisop metal ballcrusher mkll" there is little point. In fact the broadbrush circuitry of valve guitar amps is so well known and similar* that there really is nothing much new under the sun.
Well, not at first glance perhaps but the devil, as they say, is in the detail. Within the handful of triodes (and A pentode!) that you find in gitamps there is a vast range of voicings and choices as to how you arrange gain blocks. Getting these details how the designer wants them (I won't say "right" because the definitive guitar amplifier does not exist) is the result of many hours toil and cut/play/solder/curse/tea/fag/cut/solder.....

*There is probably more variation in the circuitry of valved hi fi amps. But then the aims are different. A much wider power bandwidth is required especially below 100Hz, need big, expensive traffs for that. Low distortion demands a lot of feed back and so stabiltiy becomes an issue and noise should be inaudible in normal operation, can't say that about many guitar amps!

Dave.

[chillidoggy]

I'm voting for keeping kettle leads and any other amp lead that comes out reasonably easily when I forget to unplug them as I'm lifting the amp off the cab. Which happens with alarming regularity due to being a bloke, and therefore totally unable to multitask.

[ICBM]

Sorry if this is a stupid question, but could someone with knowledge of circuits like ecc83 or IBCM just take the chassis off an amp or look at a picture in detail, look at the circuit and then copy it and make they're own amp thats exactly the same?

Pretty much, if you have both a layout picture and a circuit diagram. There are a few components that are hard to reverse-engineer from that unless the specs are written on the schematic (eg output transformers), but as Dave said it's not rocket science, and most of the building blocks are well-enough known that you could make at the very least a well-educated guess and be in the same ballpark.

Obviously the more complicated an amp the harder it is - eg trying to reverse-engineer something like a Mesa from photos and even the schematic would be quite hard, since the PCB layout is not all that obvious in many places without stripping all the components off. Traditional designs are quite easy.

There are a *lot* of small-builder amps which are either exact of very near copies of classic simple circuits like the Fender 5E3 Deluxe or the Fender 5F6-A Bassman/Marshall JTM45 - which are the same thing, in an early example of reverse-engineering! Although Marshall used a very different output transformer, resulting in quite a different-sounding amp.