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Messages - Gabriel

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Schematics and Layouts / Randall X2 preamp.
« on: November 23, 2011, 10:31:12 AM »
This is my interpretation of the Randall X2 schematic.
It's not tested yet, but i hope get start my prototypes in a couple of months.

I choose to make modular sections because it was more easy to me and if you wish you could make just one of the preamps or just the tonestack. Channel selection was sugested in another post.

I also hope you enjoy. :cheesy:

Any doubts, critics, impruvements, sugestions etc are very welcome.

Preamps and Effects / Re: Randall Warhead
« on: November 18, 2011, 06:26:22 AM »
Hello SSFelows! (sorry for the doubled post)

I'm almost finishing the layout of this preamp. In fact, as Mr. JM Fahey, have already said, the IC is fed + /-15V, and the FETs (overdrive & boost gain with +24 v. supply with + /-7V (or + / - 5v) for the  switching channels system.
I got the rest of the schemes of the amplifier (power & poweramp section) and I could finally verify this fact. Sorry for that.

Soon I'll post the layouts section of my results. :cheesy:

But while I was working on it, a doubt arose regarding the channel switching.
I can not simply copy a selection or design the channel switch with relays, my skills are not sufficient for this task.
So I was looking Runoffgroove and came across the system of selection of channels doubled at Rick Don Vance.
It was great for my project, because i'm doing modular sections of the preamp, so i did a version of the system, attached below.

My project look like this:

                                              Channel Switch

Imput stage >>                                      Ch1 Clean           >> tonestack >>> etc.
                        "Ch3" Fry (gain boost) >> Ch2 OD

What do you think? Will I have problems like "pops" or other things?


Preamps and Effects / Re: Randall RG80/RG100 Preamp DIY
« on: October 06, 2011, 11:47:42 AM »
It seems like a copy without credits.

I fixed the word "based" to "using." There was no PCB layout for this anywhere so I paid someone to create one. I'm not making any money on this. What's the problem? The overall design(s) was taken directly from I in the wrong here?!?

I removed the link.

Man, I apologize. I had no intention to offend you or anything like that.
I thought you had found the layout on the net, from a guy who was taking the opportunity to make money and stuff ... (there are many bad people out there ...)
I did not know you had spent money on it.
Perhaps for this to be a written communication, I could not fail to be misunderstood, just like you.
I sincerely ask apologize again.

Preamps and Effects / Re: Randall RG80/RG100 Preamp DIY
« on: October 05, 2011, 03:26:53 PM »
It seems like a copy without credits.

Preamps and Effects / Re: Randall RG80/RG100 Preamp DIY
« on: July 22, 2011, 07:38:30 PM »
I'm not mensur but i can answer a couple of your questions:

1 - Its a inductor (veri similar in apearence with a resistor) it's basic eletronics you know...
2 - he has already answer that: "which can be bypassed [the contour], plus it has additional gain stage for accommodating volume drop due to diode clipping."
3 - i guess it could, but resonace isn't a fancy name for low pass?

Preamps and Effects / Re: Randall Warhead
« on: June 24, 2011, 11:33:10 AM »
Greetings master,

So, i repost the schem, with the missing values.
And i also put a pot in the passive mid section of the tonestack (that was neutralized due to the active mid section) just for fun, but i guess it will be completely pointess.

When i get time, i'll make this thing and do some experiences aroud the voltage suply.

many thanks, gracias, obrigado.

Preamps and Effects / Re: Randall Warhead
« on: June 22, 2011, 11:00:37 AM »
You are not supplying the tone control parts values !! :(
Anyway, those Fets run on +18V; the IC are not specified but can use bipolar +&-18V.
This thing can't be fed from a 9V battery, unless, of course, you use a couple voltage pumps to make +/-18V.

Sorry master, my mistake, i'll fix it and repost
But i've post the original one (just to compare) in the mensur's Rg809/rg100 topic:

I gess it shows that they fed the fets with 24v+ and the ics with +/-7v !! o.O(very strange..., unless i'm wrong in my reading )

Thanks for the reply, i'll try your sugestion.

Preamps and Effects / Randall Warhead
« on: June 21, 2011, 01:57:51 PM »
Based on the official schematcs that we can find on the web a friend of mine did a new schem, simplifing the Warhead.

Idid not like the french version of the X2 head just with fets. It sounds allright, to me, but not quite good as the real one.

There are, now, only the input stage, a switch channel stage, OD stage (With the "FRY" stuff - a boost using FEt)/Clean stage and a fine tonestack (half active - half passive).

I'm not sure if he finished the project, because we lost contact with each other.

But, doing a comparison between the two schemes, i can see diferences with the supply power. I'm not sure, either, if it must run with 18v bipolar or the regular 9 v.

Can anyone help me check  this schem?

Preamps and Effects / Re: Hello! And I've got a pedal question
« on: June 15, 2011, 11:40:29 AM »
Your amp have a send/return?

You could plug the DD in there and see if the problem is solved. Maybe the AD/DA converter of the DD boost its noise to the amp.

Preamps and Effects / Re: Randall RG80/RG100 Preamp DIY
« on: April 14, 2011, 11:45:25 AM »
I hope Mensur don't mind:

Preamps and Effects / Re: Randall RG80/RG100 Preamp DIY
« on: February 05, 2011, 07:38:18 AM »
Sorry for the late reply!

I almost lost my own schematics for good due to a bad computer thats going to tilt. For that I'm not able to put my own schematis :( . I'll take it to a tec to solve the problem and then i'll put my drawings here to you see what i was doing.

1 - here is the original one:

2 - In the big picture i was cutting off all the stuff (specially the relys ) that run with 7v in the 1st page leaving only 5 parts that i presume that run with 24v:
(a) A main input(buffer?) that goes to 2 preamps - (b)the clean and the (b1)overdrive (this last one with the option of the (c)Fry boost stuff) - and for the last part the (d)EQ. I also cut of the 3rd page (the loop etc).

I cannot specify more my doubt cuz i'm not able for now to post my drawing as i've said before. But, in main lines, i was wonder if the 7v wires are really needed to make this thing work.

Thanks fot the attention!

Preamps and Effects / Re: Randall RG80/RG100 Preamp DIY
« on: January 26, 2011, 02:04:04 PM »

I got the Randall WarheadX2 preamp original schematic  and a couple of redraws of it, from a friend, in Eagle docs. I know you dont like opamps  but you could help me with the simplification of this one? Most of the work is done but i need some tips. I got some troubles with the power supply.
If you cannot help ( you probably are a busy person) i tanks anyway.

Amplifier Discussion / Re: Fet version of Marshall Superlead Plexi
« on: January 26, 2011, 01:51:50 PM »
Indeed , you really are a "Fet man". Fantastic amp! I whish i could do something like this one day...

Preamps and Effects / Re: 5150 fet french stuff
« on: January 14, 2011, 09:55:13 AM »
Yeah, I'm seriously considering build this one in 18v (i've heard some saying that higher the voltage, better the sound) just to see what this thing can do (or cannot do...)

I heard some mesa boogie dual rectifier 3channel fet version,it seems work somewhat fine...

Anyway,  I think it will be a challenge get it right and fine :trouble.

Preamps and Effects / 5150 fet french stuff
« on: January 14, 2011, 06:59:02 AM »
Hey people,

I find some 5150 peavey clone with fets, by a french dude:

Is it any good? What are your opinion about this stuff?

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