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Old 24th March 2010, 07:01 AM   #1
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Default First tube amp project: GO!

So I bought a huge 100 Watt tube amp a month ago, complete with 4x12 cab (diamond nitrox head and cab) and am super happy with it. The only problem is that it is not portable for jamming or practicing at a friends place.

I decided that since I have a good understanding of circuits (BSEE, and MSEE degree 99% done, along with common sense and electricians in the family) I will start a tube amp project that is NOT a kit. Not to knock kits, in fact they are great, but I wanted something more challenging and a better learning experience.

This thread will be the journal, complete with pictures and updates, in case anyone wants to follow along and make sure I don't get zapped to death and/or offer insight.

The schematic is this one:
http://www.schematicheaven.com/newam...at_minicat.pdf

I heard it in a shop once and loved it, and all I need to travel with is a simple 5Watt.

So far: I've ordered every single part, including the Celestion V30 speaker and the Mercury Magnetics transformers. I just need to hit up Home Depot and get the MDF to build the combo cab from scratch!

Keep in mind that I consider the cost of this amp to be my "tuition" for the course of amp building 101... if that makes sense. I also hope to learn to diagnose issues, but who knows, when I built circuits in the past I have had the uncanny lucky streak of never really making a mistake hooking things up (bad and good, because mistakes teach).

I'll take pictures as things arrive...

-Dave
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Old 24th March 2010, 10:29 AM   #2
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Looks cool, I was planning on doing an AX84 or AC4TV.

Hope it goes well for you!
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Old 24th March 2010, 11:47 AM   #3
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Wt..? Besides being drawn kinda weird,the circuitry around the EL84 doesn't look quite right,the grid is floating (no DC/ground reference) and the master pot can't be right?

Am I missing something?
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Old 24th March 2010, 12:00 PM   #4
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I also see some capacitors in unusual places
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Old 24th March 2010, 01:32 PM   #5
OneyedK is offline OneyedK  Belgium
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The schematic is correct (take a closer look), but it's drawn in an unconventional way.
Nothing to worry about.

It's basically a champ clone, converted to EL84, no feedback loop, added master and tone controls.
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Old 24th March 2010, 02:53 PM   #6
TheGimp is online now TheGimp  United States
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I agree that the ground connection is missing from the right side of the master control.

Otherwise there is no dc path from the grid to ground.
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Old 24th March 2010, 04:06 PM   #7
speleo is offline speleo  Iceland
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Dave,

Regarding cab material, have a look at the Celestion website. Look for Guitar Cab Design under Dr. Decibel secrets.

Use plywood for the cab and (maybe) MDF for the baffle and it will sound more lively. MDF is stronger but heavy and dead.

Cheers.
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Old 24th March 2010, 06:25 PM   #8
OneyedK is offline OneyedK  Belgium
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Quote:
Originally Posted by TheGimp View Post
I agree that the ground connection is missing from the right side of the master control.
Whoops, overlooked that one. Might be easier to modify that master control to a more "normal" circuit.
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