One small step at a time OR my 18 watt Marshall build

ezietsman · 2011-04-06T21:41:41+00:00

So I've decided to build an amp. A twin channel 18 watt amp based loosely on the 1974x Marshall from the 60s. The first channel will be more or less the same as the original 18 watt's, just a volume and tone knob and very little gain from the preamp, all the drive will come from the two EL84s in the power section. The second channel will have Gain, Treble, Mid, Bass and Master Volume. This will be a higher gain channel with more preamp drive than the normal channel. Befiore you ask, the gain knob and pot will go into the lo input on the second channel, as I won't be needing that input ? Instead of having a power switch like all other amps (design flaw), mine will have a switched pot that switches it on and off (duh!) as well as control the loudness of the amp by varying voltages to the power amp and phase inverter. So I'll be able to get proper power section drive at any volume. To get things rolling, I present the first component of my amp, its also the only one I have at the moment. THE PLEXIGLASS FACEPLATE! more to follow...

singemonkey

It's the best blues guitar tone I've ever heard. Best of all, I get to play it sometimes ? I will have one. Oh yes.

It sounds to me very close to the tone Clapton got with the 45watt 2x12 combo in '65. Better still, you don't have to blast yourself stone deaf to get it.

If I get one, I'll simply get the single channel with standby switch, click on/off power scaling knob, volume and tone. There's really no need for anything else. With that amp I really don't need the tubescreamer. Or pretty much anything else for playing blues frankly.

Reinhard

Now you just need to sell me the SG and you can buy one ?

singemonkey

Reinhard wrote Now you just need to sell me the SG and you can buy one ?

He. Nice try mate ? But yeah. I definitely intend to use some of the proceeds from that rather sweet guitar to buy a rather sweet amp.

ezietsman

So Sunday my amp started acting up. Volume dropped and the VVR control made a very perturbing (and loud!) crackling sound. I thought the VVR pot had gone dirty.

Lots of fiddling later, I realised the VVR pot is fine. So I had to bug fix this. I measured all the voltages, they seemed fine. (@Gearhead, the EL84s are getting 325 V, you'd be happy to know.). It meant all the valves are doing OK, and there must be a dodgy connection somewhere. Out came the wooden chopstick. Poking the two coupling caps going to the phase inverter produced noise/hum and weird oscillations. Re-soldered those and the mighty roar is back!

My friend from JHB says mine blows his 18 watt completely out of the water (he played mine on Saturday) and he is in fact going to rebuild his to one exactly like mine. Coming from a successful pro guitarist this makes me feel rather good about my attempt.

So remember, if you built an amp and something is wrong, sometimes (literally) poking inside may help you discover the problem. Do not use a conductive poking device!!

Jack-Flash-Jr

ezietsman wrote
So remember, if you built an amp and something is wrong, sometimes (literally) poking inside may help you discover the problem. Do not use a conductive poking device!!

Or at least cover your poking device with a condom.

Glad to hear the beast is well again...

ezietsman

Jack Flash Jr wrote
ezietsman wrote
So remember, if you built an amp and something is wrong, sometimes (literally) poking inside may help you discover the problem. Do not use a conductive poking device!!

Or at least cover your poking device with a condom.

Glad to hear the beast is well again...

I'm not lending my amp to you again...

Jack-Flash-Jr

ezietsman wrote
Jack Flash Jr wrote
ezietsman wrote
So remember, if you built an amp and something is wrong, sometimes (literally) poking inside may help you discover the problem. Do not use a conductive poking device!!

Or at least cover your poking device with a condom.

Glad to hear the beast is well again...

I'm not lending my amp to you again...

? if I put 41.204 Hz into your amp it's going to need a condom from pure joy...

ezietsman

Jack Flash Jr wrote
ezietsman wrote
Jack Flash Jr wrote
ezietsman wrote
So remember, if you built an amp and something is wrong, sometimes (literally) poking inside may help you discover the problem. Do not use a conductive poking device!!

Or at least cover your poking device with a condom.

Glad to hear the beast is well again...

I'm not lending my amp to you again...
? if I put 41.204 Hz into your amp it's going to need a condom from pure joy...

You will too when you realise it doesn't cut off the bass frequencies like the other sucky amps...

ezietsman

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!

Nephilyn-Lee

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.

ezietsman

Nephilyn Lee wrote
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.

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?

Nephilyn-Lee

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...

billionairebum

Sweet sweet sweet dude....

ezietsman

Ah thanks. Here's another one, this one was for the July Comp on this 'ere forum.

https://www.box.com/s/de6d9d3ce10425a8435c

Sean

ez wrote Ah thanks. Here's another one, this one was for the July Comp on this 'ere forum.

https://www.box.com/s/de6d9d3ce10425a8435c

Yowzir! Now I get what all the fuss over this amp is about. Very nice ?

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