Hi RobbieZ

Very nice build....I love the way you did the joints on the amp enclosure. Very simplistic, yet effective. I have built an amp before which only requires the enclosure build. I have seen some really complicated and difficult jointing systems used in other builds which put me off from building a wooden enclosure in the past, such as dovetail joints etc. Now I feel really motivated by your project into finishing mine......

Cheers...

Lee

To be absolutely honest building a valve amp to save money is not the way to go if you are a beginner. I have built a 100 watt Marshall style amp and the total cost including importing costs are in excess of R7500 not including the immense amount of time it takes to learn all the fundamentals of amp building and the trade secrets of good tone! /gain /stability etc etc + the time to actually build and wire everything together. All this might sound quite negative but
if you are out to experiment, learn, have fun and just looking to create a unique sounding amp then go ahead and build one! The feeling of building an amp from scratch and playing through it with your guitar is an amazing feeling - - - - - > you feel like Frankenstein! ? 8)

O and be sure to take all the necessary precautions when working with valve amps due to the high voltages inside!

If you need to be pointed in the right direction of building then send me a PM......

ez wrote: Yeah, Makepeace is right. You should be fine. Building an amplifier without knowing EXACTLY what everything does (like me) is easy enough as long as you work methodically and triple triple check everything you do as you go. Grounding design is something you should be intimately familiar with, with your background, but reading some stuff on the application in audio amps prob won't hurt (you'll likely be bored by it in 10 minutes though).

Playing your own amp is the best feeling, MUCH more rewarding than playing a shop-bought amp.

I agree there is nothing like playing an amp built by yourself the feeling is addictive. you feel like Frankenstein

I just finished my first amp recently actually the electronics side at least, still have to do the enclosure for the chassis and mount all the trannies etc . The best thing to do Is do a lot of research looking at Valve amp schematics first, this will
allow you to learn the common building blocks that make up a typical valve amp like: the high voltage DC power supply, phase splitter/phase inverter, pre-amp section, tone stack, power output stage, matching your output trannie to your
valves, biasing output tubes, types of biasing ie fixed or cathode biased, grounding etc etc.

one thing I found that worked for me is that I built each major amp section eg. power supply(DC), bias supply, pre- amp section as an independent modules. Tested Each module separately for expected outcome, then joined modules
together and tested again to check for correct operation.

Note: voltages/current in a valve amp can kill you or someone else please do homework on safety first

If you do decide to build one remember baby steps, and kiss all your spare time good buy!

ezietsman wrote:

Thank you very much.


Usually the preamp tubes are cathode biased. If the idle current is too low I would guess you need to check the cathode resistors to make sure they're the correct value. A 100 watt amp like that should shake the house if you turn it up.

What kind of amp is it?

There's some good forums you can ask, I'm not an expert in these things, maybe ask at ampgarage?

My amp is 100w push-pull type amp which should sound like a hot rodded marshall in general. The preamp design is from
Ax84.com I chose the Single ended lead preamp and hooked it up to 100watt output stage that I put together by modifiing the 50W push - pull
stage design which can be found at Ax84.com as well...

ezietsman wrote: I got my hands on a Shure SM57 and a Presonus Inspire firewire interface. I made it all work in Ubuntu (yay!) and recorded some of my noodling.

The amp was on the Lite IIB channel in the parallel triode input (Read, fatter than the other one), Volume on 7, Tone on 9, VVR on about 3/10. I used my Tokai. All variations is due to me fiddling with the guitar controls as well as due to my sh1tty playing. No postprocessing on the audio except to convert it to mp3.

I'm not knowledgeable about placing the mic, it was somewhere near die edge of one of the speakers for this recording but the recording sounds darker than the live amp. Should prob put the mic a bit closer to the centre of the speaker.

http://www.box.net/shared/4vtj96h5yjbdp64pflp6


Tell me what you fink!

> I am very jealous, and damn that amp is screaming with tone... very good job indeed!

By the way I am buisy with a 100 watt build but am having some problems. I finally biased the output tubes and preamp tubes yesterday, but my
pre-amp tubes won't bias more than 1.5mA I need them to be biased around 4mA, secondly I'm not getting enough power or should I say
volume out. The power tubes are electro harmonix EL34's biased around 30mA(for now) at a plate voltate of 450VDC.

OK one thing that I would do is to use a stepdown transformer of similar size to the amp power transformer, ie if the amp power transformer is 100w 110Vac I would get a 120w 230Vac to 110Vac step down transformer and connect
the secondary winding of my stepdown transformer to my amps power transformer primary winding. Then connect the stepdown transformer primary winding the a 230Vac mains(SA) and the amp will then be running on 110Vac which is actually stepped down from 230Vac.

This would work at the cost of buying an additional stepdown power transformer, which is about R400 depending where you buy...

Hi All, due to tests and exams my guitar amp project will be on hold for a month from today..... sorry about this.....

I am currently doing my B - Tech degree in electrical power engineering (DUT) as well as trying to keep up
with my schedule at work.

Thanks...

Lee

Progress Report 01/01/2009

--> wiring of power supply, bias supply, preamp, tone stack, valve heaters, power valves , preamp valves,
rectifier, transformer/chokes & protection relays 80% complete...

--> Testing phase: pending...

--> Biasing of valves pending...

--> enclosure build : pending...

It depends. If the Hughes has solid state transistors(F.E.T'S) for the output power stage then that's not good for me...but if it has solid state rectifier and the rest all valve then that's ok with me. Solid state rect. will produce
a more harsh/hard type of tone with some raw crunch....

you need to do some research on the circuit design.

.....between a hybrid and a pure valve amp, I would choose the mesa any day.....

Karel Mars wrote: Thanks for the lovely photos. I think your project is very inspiring. A few questions comes up for me:

Why did you choose to put the EL34's closest to the controls (vol/t/m/b)? You might have to consider putting a shield plate between the controls and the output tubes to eliminate hi frequency oscillation. Those pots are like radio antennae.

6 pre-amp tubes! Are you doing a channel switching amplifier?

Thanks for the reply.....

I did not perceive that happening but I am certainly going to consider your info.... I guess that the El34's are less sensitive than the pre - amp tubes which are extremely sensitive to ac noise.....

I think some aluminium foil (covered in plastic)over the controls will do the trick to isolate any high frequency.

There are only 3 gain stages with a toggle switch to eliminate one gain stage before the cathode follower
stage...

The last two 12AX7 tubes are for the driver/phase inverter stage.

Rudolf wrote:
The technological fast paced world as much as media would like to convince us otherwise has done nothing but drive society apart and grow an every man for himself mentality the world over.

I agree, As we increase our level of technology year after year it seems that the "world" gets more and more
stressful, polluted and unappreciative of natural things....

Nephilyn lee
Electrical Technologist

.

Gearhead wrote: Seeing as you build the power caps on Vero board.. are you not worried that the track width will be too small for the high voltage and that it will 'spark through'?

you are 100% correct, I only used the board for placement and use wire to join the components underneath , I must admit that vero board is the worst stuff you can use with high voltage....
but I took care in separating the +HT voltage rail from the ground rail by gently cutting large spaces between them. Turret board is the way to go....

Graeme Parfett wrote: @Neph: So you also build MCCs ?
Which panelbuilder are you with?

yup....

Sorry cannot say.....

I agree...

Hi all, watershed is going to be live in concert at the Barnyard theater, Gateway, Durban on the 17th, 18th
of Jan 09...

C U there....

Progress reports suspended till January 2009 due to holidays..... sorry...

I know don't count your chickens before they hatch, but these chickens have flown their coop...

Here are some preliminary photo's on the stuff that's built and working...... upload test --->

above 2000A /400VAC chiller pannel

The actual photo's.....















end.

wow..............

Gearhead wrote: Here's a some unsollicited advice: get the metal part(s) powdercoated instead of spraying it. That stuff is thicker, more scratch resistant, shinier and in the long run even cheaper than spray paint.

Thanx for the advice GH, but it(metal base part) arrived from the manufactures powder coated black.
I am going to re spray the entire thing which is going to look much better than powder coating.
Powder coating is thick, but not really shiny (depending on what clear overcoat is used) or scratch resistant.
I have many scratches on it already from drilling and filing out of the holes......

I would use powder coating if I plan on manufacturing large scale though...

Alan Ratcliffe wrote: Are you building the enclosure yourself, or having one built? If the latter, who is doing the building?

Howzit Alan, yes and no, I am building the wooden enclosure for the metal base part which houses all the tranies and electronic stuff. The metal
enclosure I got from a company called Quaterdeck (Panel manufacturers) which sponsored it to me for free because we(The company I work for)
do buissness with them. As for the paint job, my cuz is really good spray painting so he's gonna do the paint work this weekend. He's using
left over VW Black magic paint.

The wooden box is going to be covered in vynal by a guy that lives near my place.....