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Author Topic: Randall Warhead  (Read 8369 times)

Gabriel

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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?
« Last Edit: June 24, 2011, 11:22:39 AM by LOBO »

J M Fahey

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Re: Randall Warhead
« Reply #1 on: June 21, 2011, 08:26:52 PM »
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.

Gabriel

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Re: Randall Warhead
« Reply #2 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: http://www.ssguitar.com/index.php?topic=1307.0

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.
« Last Edit: June 22, 2011, 11:02:22 AM by LOBO »

J M Fahey

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Re: Randall Warhead
« Reply #3 on: June 22, 2011, 11:20:29 AM »
Well, +24V is fine for the Fets. I referred to 18V because that's what you wrote on the schematic.
Op Amps *can* work with +/-7V, but that's not usual, most everybody uses +/-15V unless having a very good reason not to do so.
Yet old Kustom amps used +/-8V ... and they were clean !!

Gabriel

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Re: Randall Warhead
« Reply #4 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.

Gabriel

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Re: Randall Warhead
« Reply #5 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
                                                        V

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?

Cheers!!!!

dhkv69

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Re: Randall Warhead
« Reply #6 on: December 14, 2011, 01:12:40 AM »
Today I traded in my peavey Rock Master preamp and avatar contemporary cab for this, and I am very happy. The cab is in pretty good condition, except for some tears in the tolex. When I heard it in the store, it sounded great. I havent played it yet becaude my amp is under repair, but I can't wait to play it.