Hi guys
I am looking at the feasibility of cloneing the gain channel of the Randall RG 80 Or RG 100 series amps (to plug into a simple chipamp, <20W, maybe a TDA2003 for a practaise amp), however i find the way the schematic i found was drawn very confusing. I was hoping someone could help me interpret the circuit diagram. I am not a 'noob' and have built several electronic circuits before, so i dont need electronics 101. In case attatchments don't work, here is a link: http://www.schematicheaven.com/newamps/randall_rg100es-rg80es.pdf (http://www.schematicheaven.com/newamps/randall_rg100es-rg80es.pdf)
I have a few questions:
1)Am I correct in thinking that the 'RED CHANNEL' is the distortion channel.
2)the circuit diagram says as a note 'All capacitors are rated in MFD at 100 volts'. I assume that means all values are in millifarads (as in 1000 uF?), but it seems strange to have a 10 mF (10,000uf) capacitor on the cathode of Q6?
3)D3 and D4 are captioned '4VZ'. Does this mean they are actually 4 volt zener diodes, even though they have the symbol of a normal Diode? A zener in the PSU is marked '12VZ'.
Thanks in advance!
I made that amp a few years ago and it's awesome.
Here are my samples:
http://www.esnips.com/doc/d6a08723-1fef-4ab9-afd4-f8520f273388/Randall-RG100ES-Boost-1
http://www.esnips.com/doc/489be47f-e102-49d0-aac5-b09ee8a4870b/Randall-RG100ES-Boost-2---Scooped-Mids
http://www.esnips.com/doc/619f7c75-6446-4b4c-85d6-6bd8258b2137/Randall-RG100ES-Boost-1(Solo)
1.Yes the red channel is the distortion channel
2.Caps are in micro farads (10uF on the source of Q6)
3.Yes they are 4V Zener diodes,(1N914 are clipping diodes,or boost in that amp, but they attenuate the signal a lot).
Thanks a lot for your help, Mensur.
May I ask how you constructed the amp - It would be great if you could post your layout for PCB/veroboard ?
Also, do you have a 'better' schematic (less confusing)?
Im starting a stripboard layout, but I will have to do a farnell order for an enclosure, the speaker and maybe parts for the power amp, if i dont use one of the TDA2003s i sampled a while back. This gives me an oppertunity to get a few PCB materials
Hi Nickbob.
Yes, the schematic *is* complex, but you should split it into its "building blocks"
Re-draw only the Red channel , the tone control and the preamp output transistor.
No Reverb, Green channel , switching or power amplifier (loop is optional and can be added later) and work from that.
You'll have your layout work reduced to what's around Q5/6/7/4 .
That's what Mensur (and anybody) usually does.
You can provide your own chipamp and +24V.
Good luck.
Juan Manuel Fahey
Quote from: mensur on October 09, 2009, 06:59:04 PM
I made that amp a few years ago and it's awesome.
Here are my samples:
http://www.esnips.com/doc/d6a08723-1fef-4ab9-afd4-f8520f273388/Randall-RG100ES-Boost-1
http://www.esnips.com/doc/489be47f-e102-49d0-aac5-b09ee8a4870b/Randall-RG100ES-Boost-2---Scooped-Mids
http://www.esnips.com/doc/619f7c75-6446-4b4c-85d6-6bd8258b2137/Randall-RG100ES-Boost-1(Solo)
1.Yes the red channel is the distortion channel
2.Caps are in micro farads (10uF on the source of Q6)
3.Yes they are 4V Zener diodes,(1N914 are clipping diodes,or boost in that amp, but they attenuate the signal a lot).
The first and last clips sound amazing. What were you using for power in that amp? Any schematics or layout? Very nice work. Thanks for sharing it with us.
Thanks,
The poweramp is my design with TDA7294(minor difference with datasheet's schem).Again the head has "LARGE" volume drop with diode clipping engaged(limit's the signal 0.7VAC p-p).
Here's new version of the preamp, with some new mods , MC34063 DC converter, to get 24V from 9V battery, plus it has voicing control, exact the same as Century C170II/2000,plus it has added gain stage to compensate volume drop caused by diode clippers.
(http://a.imageshack.us/img843/7452/ultimaterandall.th.png) (http://img843.imageshack.us/i/ultimaterandall.png/)
Quote from: mensur on August 18, 2010, 01:05:50 PM
Here's new version of the preamp, with some new mods , MC34063 DC converter, to get 24V from 9V battery, plus it has voicing control, exact the same as Century C170II/2000,plus it has added gain stage to compensate volume drop caused by diode clippers.
(http://a.imageshack.us/img843/7452/ultimaterandall.th.png) (http://img843.imageshack.us/i/ultimaterandall.png/)
Do you have a PCB layout or Eagle files for this?
HEy Mensur, nice job,
but I have 2 questions:
1 the original have 2 zeners where they go? Why u choose take off those diodes?
2 Can i put the tonestack of the Randall X2 in it?
Thanks,
The clipping diodes are in the circuit, before master contol.
It has +1 gain stage to acomodate signal loss after clipping diodes.
All Randall's have the same tonestack, Warhead has parametric mid control, which uses OpAmps, and I dont like opamps, so I did it like this.
Mensur, i would like to ask you again about the capacitors c5, c8 & c14. Are they normal (film, poly etc ) or eletrolitical (polarized) ? Cuz their values are 1uF...
tankx for the previous answers.
Quote from: LOBO on November 09, 2010, 02:21:31 PM
Mensur, i would like to ask you again about the capacitors c5, c8 & c14. Are they normal (film, poly etc ) or eletrolitical (polarized) ? Cuz their values are 1uF...
tankx for the previous answers.
I personaly like film caps(Wima MKS4) overthere, but you can try with elcos, and see what best suites you.
mensur can you tell how to use your schematic with the regular 24V? (What to erase and what to add?)
Here's what's new:
http://img826.imageshack.us/img826/4341/randallultimate.png
We have standard Randall RG100ES with contour control(which is from Century 200), which can be bypassed, plus it has additional gain stage for accommodating volume drop due to diode clipping.
Congratulations, Mensur.
Excellent design. :tu:
Mensur.
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.
What's the problem with PSU?
hope mensur has pcb on this one :D
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:http://www.4shared.com/document/sLu8FxGW/x2pre_split.html
(http://www.4shared.com/document/sLu8FxGW/x2pre_split.html)
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!
Hi,
could someone post the pic randallultimate.png again? Imageshack killed it...
I hope Mensur don't mind: http://www.megaupload.com/?d=VFD4E6KP (http://www.megaupload.com/?d=VFD4E6KP)
Quote from: LOBO on April 14, 2011, 11:45:25 AM
I hope Mensur don't mind: http://www.megaupload.com/?d=VFD4E6KP (http://www.megaupload.com/?d=VFD4E6KP)
I don't mind:
http://img641.imageshack.us/img641/4237/ultimaterandall.jpg (http://img641.imageshack.us/img641/4237/ultimaterandall.jpg)
Could you post the one without the 9v adaptor?
What charge pump was used to get 24v from 9v?
Quote from: tra on May 20, 2011, 05:00:10 PM
What charge pump was used to get 24v from 9v?
MC34063
Mensur, thanks for the updated schematic! Coupla questions:
- What's the 150uH 'L1' component in the voltage adapter?
- If I don't want the extra gain stage and contour circuit, what can I leave out of the schem?
- Is there any way to add a Resonance/Depth control next to the Presence one? It would be handy.
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?
Hey~
I've been reading all of your posts on the SSamp forum. I have 3 RG100HT .
All of them have really crappy volume drop when the treble is pulled (gain
boost). I looked at your 3 page schematic but can't for the life of me figure
out what part specifically I can use to get the volume back up when the
treble knob is pulled.
Can you point me in the right direction?
Thanks!
jason
Quote from: mensur on October 09, 2009, 06:59:04 PM
I made that amp a few years ago and it's awesome.
Here are my samples:
http://www.esnips.com/doc/d6a08723-1fef-4ab9-afd4-f8520f273388/Randall-RG100ES-Boost-1
http://www.esnips.com/doc/489be47f-e102-49d0-aac5-b09ee8a4870b/Randall-RG100ES-Boost-2---Scooped-Mids
http://www.esnips.com/doc/619f7c75-6446-4b4c-85d6-6bd8258b2137/Randall-RG100ES-Boost-1(Solo)
1.Yes the red channel is the distortion channel
2.Caps are in micro farads (10uF on the source of Q6)
3.Yes they are 4V Zener diodes,(1N914 are clipping diodes,or boost in that amp, but they attenuate the signal a lot).
Isn't the gain boost function just toggling the silicon diode clippers, of which's forward voltage is much below the forward voltage of the other clipping devices (which, if I remember right, were few back-to-back zeners). Hence the drop in loudness.
To even out the volumes you need to install an additional circuit that either
- Switches on when gain boost is not toggled and attenuates the signal by proper ratio.
- Switches on when gain boost is toggled and amplifies the signal by proper ratio.
Here is a semi-verified PCB layout using Mensur's schematic. Passes signal, but the tone stack doesn't seem right. Could be a fault in the layout or my build.
Link removed due to complaint.
"Based"????
It seems like a copy without credits.
Quote from: LOBO on October 05, 2011, 03:26:53 PM
"Based"????
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 Randall...am I in the wrong here?!?
I removed the link.
Quote from: tra on October 06, 2011, 10:08:07 AM
Quote from: LOBO on October 05, 2011, 03:26:53 PM
"Based"????
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 Randall...am I in the wrong here?!?
I removed the link.
There is no problem with making a PCB from someone's schematic and posting it here, it just needs to be noted that it was their circuit. No big deal.
Quote from: tra on October 06, 2011, 10:08:07 AM
Quote from: LOBO on October 05, 2011, 03:26:53 PM
"Based"????
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 Randall...am 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.
No problem. We'll let Mensur decide if the layout should be made available here. Until then, I'll keep the link off of SSGuitar. It's available on other DIY forums if anyone is interested.
Quote from: tra on October 06, 2011, 02:33:11 PM
No problem. We'll let Mensur decide if the layout should be made available here. Until then, I'll keep the link off of SSGuitar. It's available on other DIY forums if anyone is interested.
You might want to send him a PM, I'm not sure he gets on here often and he might not notice this thread.
I'll post maybe tomorrow my recently finished layout of this RG-100ES amp project files. Actually, a mix of RG-100ES preamp(green and red channels), Belton BTDR reverb, TDA7293 power amp, and power supply.
Quote from: ENGR BUGO on October 11, 2011, 04:15:48 PM
I'll post maybe tomorrow my recently finished layout of this RG-100ES amp project files. Actually, a mix of RG-100ES preamp(green and red channels), Belton BTDR reverb, TDA7293 power amp, and power supply.
I await this anxiously!
Quote from: tra on October 11, 2011, 04:16:32 PM
I await this anxiously!
here: http://www.ssguitar.com/index.php?topic=2324.0