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My new amp (solid state "mesa recto")

Started by Alexius II, July 29, 2011, 03:41:07 PM

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Alexius II

Will do!

I just noticed that tomorrow is sunday :duh so aluminium obviously comes the day after tomorrow ;D

jcgss77

Very nice work on your amp, and very nice playing.  Congratulations!   :tu:

Puguglybonehead

Wow! Very nice job on this amp. Your sample sounded great! Love the look you did for the cabinet. Very inspirational.  :tu: Did you use the Dr. Boogey circuit for your preamp?

I have a chip-amp kit (from Ebay) based around the same chip. I was thinking of building it into a chassis with 2 "bays" in which to plug in different preamps. (thinking the ROG circuits, ie: Professor Tweed in Ch 1, Matchbox in Ch 2, etc...) Was thinking of being able to plug in preamps sort of PC sound card style. Kind of a modular analog "modeling" amp.

Did you solve your problem with the drift in the trimpots? That worries me a bit. Has anyone had problems like this with the other ROG circuits? I guess it's worth measuring voltages and going to fixed resistors.

J M Fahey

Yes, I suggested that.
I don't like a trimpot (or any potentiometer) carrying DC in my signal path, much more so if it's a high gain circuit, because a mechanical contact on a carbon track is a bad contact, by definition.
Conductive plastic pots are better in that aspect .... but best connection is a soldered one  ;).
As of your plug-in preamps, I suggest you do not rely on edge connectors (as in PC boards) but normalize on a certain regular connector  with an "universal" pin assignment.
PC board makers can get away with edge connectorsw because they can gold plate them, which is beyond what we can do within our means.
As an example, *all* of my instrument amps which I build commercially have the same connector:
+15/-15/signal out/ground/+B (usually +40V) for the LED or anything else which does not run on +/-15V
That way, I have already built cabinets+60/100W power amps+PSU, and by plugging the approppriate preamp the customer can carry any amp he chooses in a jiffy.
I usually have a Bass preamp, a simple 3 channel Mic/Keyboard one, a regular (clean/distortion) Guitar preamp and a Jazz sound one.
That covers most bases with a minimum effort... and minimum inventory.
The power amp+PSU is also plug-in so somebody with a burnt one can trade it for a new one in about 5 minutes for a fixed price.
Modular is a very practical concept.
All of my 60/100W power modules have had the same connectors and are mounted with the same 2" separation 1/8"bolts (and have about the same footprint) for the last 30 years, so somebody with an old workhorse can have it running like new with no problems at all.
That has given them some legendary reliability status, not bad as a selling point.
It also means that somebody in a far away Province or neighbouring Country can order a new module and revive his burnt amp without moving its bulk back and forth.

joecool85

Quote from: J M Fahey on October 06, 2011, 06:38:52 AM
All of my 60/100W power modules have had the same connectors and are mounted with the same 2" separation 1/8"bolts ...That has given them some legendary reliability status, not bad as a selling point.

Ok, that's not fair.  Stop telling us how awesome your amps are when we can't get them here in the US!   :trouble
Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com

J M Fahey

Hi joecool, I didn't use the word "awesome"  :lmao:
It's just that I have the funny idea that things should last , providing good service to their owner along the way.
And just between you and me, it also had a lot to do with not wasting perfectly good stuff I had already built, at a high cost to boot, not in $$$$ but in man-hours (mine) which is an even scarcer stuff.
So when I design, say, a new power amp, for example going from TO3 devices to plastic transistors, or from bipolars to MosFets or from discrete to chipamps (I'm road testing TDA7294), if I make them mountable to the aluminum back panel (my heatsink) with the same two screws, same holes, it means that if I still have 60 backpanels left from the last 100 unit run, I can keep using them, and viceversa.
And if an old client shows up with a PCB "repaired" by somebody who lifted half the pads and traces, ruining it beyond repair, I just slap a new one , even a different technology one.
In fact, anybody who shows up with a pre-2006 board with TO3 2N3055 gets the TIP141/142 one, even if only one output transistor is dead and nothing else, because counterfeiting has made them unusable.
Now I'm in Brazil setting up shop here, going tghrough all the paperwork, red tape, etc. , and one homework I'm having to complete is designing a "packaged"power amp (yes, you guessed right, still mountable with those old screws), similar to those ILP modules used by many British SS amp makers, so if a guy has a problem 3000 miles away I just mail him a new one, together with a little silicon grease, so he drops the old one in the junk, wipes old grease, applies a little new one, bolts the new power pack, plugs 3 connectors and is home and running again, no soldering.
All he needs is a screwdriver and a little tissue paper.
Shipping costs here are *outrageous* and the Country is huge, not to mention that Mail service is poor, to say it politely.
PS: if things go well here, maybe I get in the mood and setup something on the US side, as we already talked.
Just give me some time.
:tu: :tu: :tu:

Alexius II

#36
Hello after quite a long time!

I now finally have some free time to finish my "almost finished" projects, and this is one of them. Some time ago I replaced those trimpots with fixed resistors and all the strange "noise artifacts" (scratching) are gone. I also replaced two bad pots and that ugly power switch (green led light instead of red/orange ac light). While doing that, I temporarely removed the buffer - and while testing the amp - found out it doesn't need one (for now). I might add a switched buffer at some point, as the line-out after tone stack without an buffer is not very nice.

I also have all the materials for the labels, which should be finished until the end of the week.
Will post photos and samples when it's done  :tu:

EDIT:
Quote from: Puguglybonehead on October 06, 2011, 02:38:10 AMDid you use the Dr. Boogey circuit for your preamp?
Yes, the preamp is a Dr.Boogey. I made the PCB from gaussmarkov blog :tu:

Alexius II

Today I tried to do a few different label designs and came up with something like this:



Each sign represents a letter: I for input, G for gain, B for bass, M for mids, T for treble and P for presence, while maintaining the original sharp/linear theme from the logo. I am just now drawing theese in autocad, so that I can take them to a nearby workshop tomorrow (abrasive waterjet cutting). I have some 1mm and 2mm aluminum plates, so two different label types will be made: labels cut from 1mm aluminium plate, painted in black - and labels from 2mm aluminium plate with just the sides painted in black, like in the sketch above. If it turns out not to be what I immagined, the design will be changed. If all is ok, final pics should come soon  ;)

Alexius II

#38
No comments.. I guess no one likes my design :tu:

Anyway, today I got the aluminium plate back:


And here is a quick ugly photo with raw unfiled labels placed on the amp:


It does look kind of strange to some people, but it turned exactly as I hoped.
I will continue on monday (filing, sanding, painting...) :)

EDIT: Also, all the visible screws have been changed to black hex type, as I like the look of them more.

joecool85

I think it's great.  Though it's not quite my style, I love the machined aluminum.  Was it expensive to get done?
Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com

el nino

congratulations man...
Its looks very professional finish, maybe it should called "tiny recto" ?
kerraankkk...
my guitar want's to kill your father

Alexius II

Thanks  :tu:

The cost for the waterjet cutting was 8€ (around $10). Not a lot, considering one unique amp, but not really cheap if I would want to do similar things often ;)

The main problem was, this being a huge machine, the little letters would easily get flushed away as "debris" so we had to modify my drawing a little. Solution was to add a tiny line, few mm long and around half mm thick, that would not get cut - connecting the symbol to the rest of the plate. Worked like a charm, but some filing and sanding will be required. (just like some small model airplanes that have all the plastic pieces attached from the molding process)

el nino: since the "Mini Rectifier" already exists :-X I choose another name: Black Mesa.
This name tells us, that the amp was inspired by M/B - and that I am a serious computer geek (Half-Life anyone?)   :lmao:

Etching the name on a small plate (that was also cut from the same aluminium as other labels) will hopefully be the final task, thus concluding my work on this amp  ;)

Puguglybonehead

Nice stuff! That is a very unique and original look you've got going on there. Not an easy thing to achieve, nowadays. I like how it looks almost Cold War Industrial. Your labeling technique is clever. Very cool!

joecool85

So, those labels are attached to the front somehow...superglue?  I thought at first they were all one piece, etched into the front, then I noticed the two separate pictures and figured out why you were referring to them as "labels".
Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com