Fender Super Twin.

[dave.king1]

Thanks for the pic Doc, the wiring looks to be of an "interesting" standard.

From pics on the net I Don't Think Fender Done It This Way ( apologies to Waylon )

[DrNomis_44]

Thanks for the pic Doc, the wiring looks to be of an "interesting" standard.

From pics on the net I Don't Think Fender Done It This Way ( apologies to Waylon )

Granted it does look a bit like a "rat's nest", I might see if I can tidy things up when I get round to doing the restoration work on it, the chassis definitely could do with a bit of a clean-out and service, I did spot one electrolytic cap that looked like it was on the way out.

[DrNomis_44]

Update:

Did some googling for schematics for the Fender Super Twin and found that what I actually have is the non-reverb version, apparently there are two Super Twins that Fender used to manufacture, there's the Super Twin Reverb which uses a couple of unusual valves in the preamp, and then there's the Super Twin non-reverb which uses the same preamp circuit minus the reverb circuit, but is basically the same as the Super Twin Reverb, so, going by that, it's most likely that my Super Twin amp hasn't been modded but has had some electrolytic caps replaced, I haven't had a look inside the metal cover that's covering up all the main supply filter caps yet, this cover is sometimes referred to as a "Doghouse" by amp techs, this coming fortnight, I'll see if I can order a replacement Fender style knob for it and some new valves for my Legacy amp from Evatco.

[Marcel]

Update:


I thought that I would do something cool and post a pic of the insides of the chassis of my Super Twin amp for you to check out, so here you go, this is what it looks like inside the chassis of one of these things, this is "Old School" Electronics where a good proportion of the components are mounted on Eyelet Boards, not Printed Circuit Boards, this is how Fender used to build their amps back in the day:

Attachment 19955

OMG !!!.... Been a way long time since I've had to work on gear that looks that untidy, along with much fear that anything you touch might disintegrate...lol

... Probably doesn't look as bad in the flesh, but the photo sure brings out the worst of the cosmetic aspects of it...

[DrNomis_44]

OMG !!!.... Been a way long time since I've had to work on gear that looks that untidy, along with much fear that anything you touch might disintegrate...lol

... Probably doesn't look as bad in the flesh, but the photo sure brings out the worst of the cosmetic aspects of it...

But in a funny and perverse kind of way, the insides of the chassis seems to be what really gets me excited, I guess old school electronics fascinates me for some reason that I don't quite understand.....lol.

[Marcel]

I know where you are coming from on that...

There is a simplicity and a danger in tube gear that solid state just doesn't have. When you think of it nearly all tube gear gets their results with typically less than 10 active elements. Some how I think, and regardless of how it may sound or cost, we will never see the day where a solid state 50W 2204 style amp will ever be released boasting only 8 transistors.

Yeah, the danger is all pretty much the high voltages at potentially lethal currents. 500VDC @ 300mA in a guitar amp is more than enough to switch off a human life... and if working on that gives you a 'buzz' then maybe old school AM radio broadcasting repair might be worth a try where 6kVDC @ 700mA is quite common and 25kVDC @ 1.5A over two serious power tubes in series is often encountered, The thoughts of working anywhere near those voltages make some break into a severe nervous sweat, whereas others like myself it is our day-to-day job ... go figure...

Regardless of all that my heart just loves hearing a good tube guitar amp. 2nd harmonic and even overtones sound so much better when produced by real tubes than the filtered third and odd harmonic overtones that are the more natural condition of solid state. I suppose it is all a question of balance really....

[DrNomis_44]

I know where you are coming from on that...

There is a simplicity and a danger in tube gear that solid state just doesn't have. When you think of it nearly all tube gear gets their results with typically less than 10 active elements. Some how I think, and regardless of how it may sound or cost, we will never see the day where a solid state 50W 2204 style amp will ever be released boasting only 8 transistors.

Yeah, the danger is all pretty much the high voltages at potentially lethal currents. 500VDC @ 300mA in a guitar amp is more than enough to switch off a human life... and if working on that gives you a 'buzz' then maybe old school AM radio broadcasting repair might be worth a try where 6kVDC @ 700mA is quite common and 25kVDC @ 1.5A over two serious power tubes in series is often encountered, The thoughts of working anywhere near those voltages make some break into a severe nervous sweat, whereas others like myself it is our day-to-day job ... go figure...

Regardless of all that my heart just loves hearing a good tube guitar amp. 2nd harmonic and even overtones sound so much better when produced by real tubes than the filtered third and odd harmonic overtones that are the more natural condition of solid state. I suppose it is all a question of balance really....

I think part of my fascination with Tube/Valve technology is that I'm tired of trying to work with components that require a magnifying glass and a pair of tweezers just to read the component values and solder them onto circuit boards, I prefer working with components that I can easily hold in my hands and read without squinting my eyes, I've found that in reality, surface-mount devices are not more reliable than conventional components, but if other people like SMD technology well then each to their own.

When a Valve amplifier distorts, or is overdriven, as you have said, they do generate even order harmonics, and they definitely do sound more musical, to my ears the difference between an overdriven Valve amp and an overdriven Solid-State amp shows up as a high-frequency crackling when a Solid-State amp is overdriven, a Valve amp sounds a lot smoother to my ears, it has a fuzziness in the high-frequencies, plus the distortion harmonics tend to be mostly in midrange and upper midrange frequencies, but the overall tone is more determined by the circuit-topology of the amplifier, my Marshall MA100C is an all Valve 100 Watt amplifier and the signal-path is all through Valves from the input through to the output, there is some solid-state circuitry but that's mainly for channel-switching, reverb, and the resonance control which affects the low end in the amps power-amp section.

And it's true, for a basic Triode gain-stage you need less passive components to get it working correctly than you need for an equivalent Bipolar Transistor gain-stage, you only need three fixed resistors to get a Triode gain-staged biased correctly, whereas a single Bipolar-Transistor needs four, yes there is the Fet (Field Effect Transistor) which is like a Solid-State equivalent of a Triode, but in actual fact, the Fet behaves more like a Pentode.


If you do know what you are doing and follow the correct electrical safety procedures then Valve amps can be safe to work on, provided that you keep your head screwed-on.

[Marcel]

Amen to everything you wrote Doc...you are preaching to the converted...lol

All my tube knowledge basics (and a lot of what I know about electronics) I learnt back in the early '70's. To get out of the Melbourne winter cold I joined the schools ham radio club. It is amazing what sinks in to a young teenage mind when you overhear doctorate professionals giving an in depth Amateur radio training course on the subject at a time when tube technology was still regarded as 'current' and the 2N3055 and the NE741 were the new kids on the block...

As for SMD.... try playing with that stuff on 10GHz or 15GHz where true 'White man magic' starts to happen and everything below 1GHz seems to behave like DC by comparison ...

I have similar to you with my JVM210c. 100W 2x12 combo with bucket loads of gain on an all tube signal path and solid state switching and digital reverb. It is certainly more amp than my meagre guitar playing deserves...

[DrNomis_44]

Amen to everything you wrote Doc...you are preaching to the converted...lol

All my tube knowledge basics (and a lot of what I know about electronics) I learnt back in the early '70's. To get out of the Melbourne winter cold I joined the schools ham radio club. It is amazing what sinks in to a young teenage mind when you overhear doctorate professionals giving an in depth Amateur radio training course on the subject at a time when tube technology was still regarded as 'current' and the 2N3055 and the NE741 were the new kids on the block...

As for SMD.... try playing with that stuff on 10GHz or 15GHz where true 'White man magic' starts to happen and everything below 1GHz seems to behave like DC by comparison ...

I have similar to you with my JVM210c. 100W 2x12 combo with bucket loads of gain on an all tube signal path and solid state switching and digital reverb. It is certainly more amp than my meagre guitar playing deserves...

I've been into Electronics as a hobby since I first started when I was 13 years old, I'm 47 years old now, turning 48 in August this year, I'm mostly self taught in Electronics but I did do some formal studies in the mid 90's at my local University, I've got lots of build projects in my head that I would love to do, you may have seen my DIY Valve Amp Head thread in the Pitbull Guitar Amps section, haven't been able to order the bits I need to do some more work on it this year so far, had other things I needed to put my money into, but hopefully later on this year I'll be able to do more work on it, I do happen to have some test equipment like a Signal Generator, a good 20Mhz Dual-Trace Oscilloscope, some good Multimeters, a couple of good temperature controlled Soldering Stations, but I'll need to design at least one good Dummy Load for testing/biasing guitar amps, this whole Electronics hobby thing is a fun learning experience, and so far I've enjoyed it a lot.


One thing I would love to learn is how to design a good sounding speaker cab for musical instrument amplifiers, I've got a great book lying around somewhere that's got all the theory and stuff in it about designing speaker cabs, it's mostly geared towards Hi Fi speakers but the underlying principles are the same, the book is written by a guy called Vance Dickason, and you can buy it from your local Jaycar Electronics shop, I've got another book called Build Your Own Audio Valve Amplifiers, which is written by another guy called Rainer Zur Linde, Jaycar Electronics also sell this book, it's mostly geared towards Hi Fi Audio Valve Amplifiers but there is a section on Guitar Amplifiers in it too, there's also a great project for a Stereo Hi Fi Valve Preamp and there's also PCB artwork included too if you want to etch your own PCBs, pretty cool, I'm seriously thinking of building one one day once I can get all the parts I need, other pieces of Valve equipment I'm seriously interested in building are a set of four Gyraf Audio Valve Preamps for my little bedroom studio, but I need to source some Lundahl input and output transformers for them first though, and they are not cheap.

Here's a link to the Gyraf Audio website, some really cool stuff on it:

http://gyraf.dk/


The Gyraf Audio Valve Preamp I'm interested in building can be found amongst the DIY projects, it's called the G9 Mic Preamp.

[Marcel]

Wow... lots of good stuff on the Gyraf site... And that G9 preamp would be quite fun and challenging to build...

Much the same here... Got into radio in year 7 by joining the school radio club in '73. Radio tech in the RAAF until '86, Roadie work for a while and played Audio tech at Brisbane Expo 88, Wanted a real job so worked as a tech for radio and TV stations then moving on into aviation electronics for a few years, now after collecting all the tickets and licences I need to hold I'm back as private contractor tech for commercial radio... I'm 55 now and collected heaps of junk and test gear over the years that all sits gathering various amounts of (wood) dust in my 9mx12m shed that also doubles as my luthery workshop that was setup mostly to help recover from a heart condition...lol

It's all good.... Like everybody, I know a bit about some things and not much about others...