1959 cascade mod (Randy Rhodes head) HOW TO

Info for maintaining and tweaking your amp to perfection.

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Postby Kapo_Polenton » Thu Jun 12, 2008 3:59 pm

Not only that, but how well does it scale back to a plexi AC DC crunch if you want to go that route.
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Postby eddie123mi » Tue Jun 17, 2008 9:14 pm

Why do you NEED a MV?
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Postby gluke » Fri Jun 27, 2008 7:41 am


Here it is:

Input II
Both 68K on the jack to V1A
820 + 330 cathode
.22 -> 1M pot -> 470K -> V1B

Input I
Both 68K on the jack to V1B
2K7 + .68 cathode
.22 -> 1M pot -> 470K+470pF -> V2A

They have shielded cable on both inputs and both pots. No caps on either pot. They have two 100ohm and a potmeter between the heaters to ground to tune out hum I guess.

So no switching on the jacks. It's a cascaded layout with the Input I connected straight to V1B.
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Postby rgalpin » Mon Jun 30, 2008 10:48 am

do you mean .022?
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Postby gluke » Thu Jul 24, 2008 4:39 am

Sorry, yes all caps .022
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Postby rgalpin » Thu Jul 24, 2008 10:24 am

why do folks here on the board say that the two 68k input resistors actually puts 34k resistance to the pin? i'm having a hard time getting my head around that.

the signal goes from the jack to a 68k. after the 68k the circuit branches in 2 directions, as follows:

1. the signal sees 68k resistance back to the low input jack. i assume that jack is grounded out when there is nothing plugged into it. so that is 68k resistance to ground.

2. the signal also goes to the pin on the tube.


| ----> 68k ground


does that equal 34k to the pin?
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Postby gluke » Fri Jul 25, 2008 2:53 am

You have to look at the curcuit and how the switching function in the two jacks works. When you plug into the high input the "tip" of both jacks are connected together so both 68Ks are in parallel with a 1M to ground. hence 34K.
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Postby hotguit » Sat Jul 26, 2008 6:58 am

I said a MV is needed because Vol 1 acts as gain for V1B, Vol 2 acts as Volume/gain for V2.
You can adjust gain tone with these two pots too.
So i think that having a Post P.I. MV would be better; but it's an opinion of mine. more control on the overall volume.
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Postby 908ssp » Sat Jul 26, 2008 10:18 am

hotguit wrote:Hi
I said a MV is needed because Vol 1 acts as gain for V1B, Vol 2 acts as Volume/gain for V2.
You can adjust gain tone with these two pots too.
So i think that having a Post P.I. MV would be better; but it's an opinion of mine. more control on the overall volume.

That is the way SDM Steve set up my 2204. The V2 volume really changes the tone drastically cutting the distortion from the phase inverter. Great for changing the tone lousy as a volume control. The PPIMV works well but I prefer an attenuator and run the PPIMV all the way up.
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Postby gluke » Fri Aug 01, 2008 5:42 am

ok I'm trying my hardest to figure this one out, but I'm not quite getting it. The bright channel is hooked up like any other 1959 but with a .022 instead of .0022. There is a bright cap as well but it threw me off 'cause it's mounted on the curcuit board. It doesn't have a value written on it. It just says J on top. The other channel also is hooked up as any other 1959.

The only "mod" is a brown cable that is hooked up to the grid in V1 where input I is connected. It goes up to the curcuit board next to the green cable (that goes to V2) and connected right next to the two mixer resistors. I assume this new cable does the cascading, but I can't figure out where it is going on the curcuit board. The only thing that would make sense is if they cut the trace between the two mixer resistors and went straight form channel II volume pot through the 470 and into channel I through the brown cable.

I don't know. I have to try it out in one of my ampes and see how it sounds.
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Postby D-Max » Sat Aug 02, 2008 4:09 am

I think Gluke is right about the the brown wire and the way it is cascaded.

Once the 1959RR was released, I tried to find the owner's manual on the internet but no luck.
I couldn't find the English version of the 1959RR handbook, but at some point (don't know when) I did find a Japanase version.
It's on the Japanese Marshall website:
I copied the Japanese text from the PDF into Google Translate to translate the Japanese text into English, with quite a cryptic text as result:
[color=darkred]1959 RR rear panel front panel 1959RR

Front panel

1. Power switch
Amplifier and power on / off switch. Power amplifier with the appropriate power supply That when the switch is illuminated. Amplifier is turned off when the power is supplied by When he is not illuminated.
NOTE: When you move amplifier, power amplifier to cut the power cord pulled out state ARUKO And please be sure to check.

2. Standby switch
Switch to standby power switch (1) in conjunction with the amplifier to warm up before use Can be life-power tube can be extended. When you use amplifiers, Make sure you switch the power at the standby switch to "standby" remains the . The vacuum tube to warm the supply voltage is needed. Approximately two minutes later, the vacuum tube
Temperatures reached the correct behavior, you can switch on standby. Playing??
Amplifiers expected to be on / off when the vacuum tube to extend the life of the standby switching Ji use only, please. Also, completely off the power when the power switch off before the News
By Tan please switch it off.
NOTE: The following Presence (4), bass (5), middle (6), Treble (7) after completing four Troll, Channel 1 and Channel 2 all common to both. Treble, middle, nyah Su is very interactive, one to control and manipulate the other two control Le action may change. Try out a variety of settings, it is recommended. Randy's favorite setting is on the panel as well.

3. Control Presence
1959 RR is the power of the control section of the action, power amplifier NEGATI By changing the feedback in a high-frequency sound to increase. Clockwise And sound and turn a piece of "Art" is increasing, from Sharp and Crisp.

4. Based Control
Adjust the bass sound. Clockwise turn will increase the range and bass.

5. Middleware Control
The most important mid-range sound regulation. Clockwise around mid tones and increasing the thickness Oh Have heard the sound of the punch. And anti-clockwise turn, thus reducing the mid tones.

6. Treble Control
Adjust treble sound. And clockwise around high-frequency sound (Treble) will increase, Brighter tone guitar.
The 1959 Marshall Super Lead standard amplifier, unlike Randy Rose
L mode, the gain to increase, thus making the circuit to increase the distortion The changes have been made. This modification of the music that you had Randy distortion Amplifier to boost the level it is easy to use.
This change is very simple, but two separate valves to a "cascade"
(In the first stage output to send to enter the second stage) and the technique has been used Masu. Traditionally, each part is divided into two channels 1 and Channel 2 input buffer / GEINSUTEJI role of the first flag. Then take the next stage to supply the individual The signals are mixed in, and amplified by the tone stack supply.
Cascaded valves 1, the guitar signal is about 36 dB, or 60 times the normal circuit At this point, much larger than levels seen in amplification. This is the big signal After further amplified by the stage and soon became head room can be eliminated, resulting in the wave
Is a major form of distortion. The reshuffle also added another two-channel volume Does work, but the impact of change in tone, gain and increase the volume controls Roll. Channel 2, using the guitar signal cascade through the entire circuit Characteristic. Channel 1, using the cascade to bypass the standard amplifier Format. In this case, "Volume 1" is functioning normally. This Modification of the standard two-channel format is no longer available.

7. Volume 1
Channel 1's overall output level of regulation. Clockwise around the size and volume Com. This channel is a high sensitivity of the Treble.
Full cascade mode, the valve is Volume 1 of 1 amplified by the second half of the amount of signal Control the master volume as a whole cascade circuit. The PURIAN The next group stage to boost the signal sent to gain control and think about this And. Channel 1 is connected to the standard guitar mode, the normal cycle DIFAI 1959 Super Lead is not the same as the volume control Functional.

8. Volume 2
Adjust the full cascade mode. 1 valve amplified by the first half, supplied by the late The amount of signal control, by itself gain control circuit as a cascade.

9. Channels for a high-sensitivity input
Channel 1 from the bright sound of the "sensitive" guitar input, modified by TEI standard mode l does not generally the most commonly used input. Always high Quality shielded cables to be used for guitar please. NOTE: This input to connect the KASUKE DE bypass circuit in the amplifier is a standard format.

10. Channels for a low-input
Channel 1 for "low sensitivity" guitar input. "Sensitive" input from low-volume is 6 dB And (half) level, and the result, the ability to gain a small state. This is a non - Sensitivity is always active and high output pickup equipped guitar circuit is necessary to field May result. NOTE: This input to connect the cascade circuits are bypassed by the amplifier is based
TANDADO format.

11.'s Channel 2 input for high sensitivity
This guitar is connected to the input of a full cascade mode.

12. Channels for low-input 2
This guitar is connected to the input of a full cascade mode. "Sensitive" input.
Resona 6 dB volume is low (half) level, and the result is less ability to gain state. This is a very sensitive and high output active pickups are equipped with circuit The guitar may be necessary.

Rear Panel

1. Loudspeaker output
Warning! The amplifier, speakers, please do not use any connection.
Speaker extension to connect to the cabinet two parallel Roud
Jack speaker output. Always a positive amplifier output impedance selector Please set properly (2). Also, make sure that high-quality speakers for the (Shield) Cave Please use the LE. Guitar (shielded) cable, please never put on the shelf.
When using extension cabinet, make sure to seal high-quality speakers
- No, please use the cable.

2. Output impedance selector
Speaker amplifier output impedance match.
Output impedance selector is set to change when, at 1959 RR always turn the computer A trim, please.
Marshall's all-valve amplifiers when using the following in mind, please. a)
During the operation amplifier must be connected to the speaker. b) amplifier selected INPIDAN News of the extension speaker cabinet and out of the total impedance Them.
1x16 O cabinet: 16 O selectors to set one of the output to use
RR guts
RR_gut_rotated.jpg (172.11 KiB) Viewed 2154 times
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Postby D-Max » Sat Aug 02, 2008 4:13 am

So.....my preliminary conclusion is that in the 1959RR a one-wire mod is applied as was mentioned on forums already months ago. But it is an one-wire mod the otherway around and leaving the bright channel stock. I am right?

I made a schematic of the preamp (until V2a), see attachment.

So, what are your thoughts about this?

If anyone has the PDF of the English version of the handbook and some better pics, I am quite happy to receive it for further analysis :wink:
preamp only.gif
RR - draft - preamp
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Postby MassTone » Sat Aug 02, 2008 8:57 am

Just adding the mod description from Musician's Friend for reference...

Cascade mod in depth Unlike a standard Marshall 1959 Super Lead amplifier the Randy Rhoads model contains a modification that increases gain and therefore extra distortion within the circuit. This modification 'hot rods' the amplifier making it easier to push it into the saturation levels necessary for the sound that Randy needed. The change involves 'cascading' (feeding the output of the first stage into the input of the second stage) the two halves of tube 1. Traditionally each half would serve as input buffer/first gain stage for the two channels i.e. one half for channel 1 and the other for channel 2 from there they would separately feed the respective signals to the next stage which would mix them further amplify them and feed them to the tone stack. Cascading tube 1 results in the guitar signal being increased by around 36dB or 60 times much larger than it would normally be at this point in the circuit. Subsequent stages then try to amplify this larger signal by similar amounts and quickly run out of headroom causing the waveform to distort severely. The two channel volumes still remain functional after the modification but adopt different roles for their affect on the tone allowing control of the extra gain and volume. Plugging into channel 2 routes the guitar signal through the whole cascade circuit while plugging into channel 1 allows you to bypass the cascade and use the amp in its standard format where 'Volume 1' will function as it normally would. Standard Channel 2 format is sacrificed due to the modification.
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Postby beaulieu » Sun Aug 03, 2008 9:15 am

Ok so Its a one wire mod?? How can one do this mod but still save the normal ch?? I noticed on the 1 wire mod the normal ch no longer works!! Anybody?? Steve (SDM)??
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marshall RR

Postby lifer » Sun Aug 03, 2008 10:15 am

man, whatever the "mod" is, I'm sure it's easy to do...

Marshall can't afford to slow down the production line w/ anything

too involved!!

Only Marshall can add a couple lousy wires and ask another $600

on top of their already overpriced, shi**y amps.
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