Fender Princeton Reverb II
The Footswitch p/n 017007
possible solution to the clean sound tone loss problem
photo from 1983 Fender amp catalogue
See the photo below - that's all it is folks; 2 buttons, ('lead' and 'reverb'), 2 LEDs and a couple of resistors.... What's all the fuss? You read a lot of stuff about the Rivera-era Fender footswitch, some of it contradictory. Despite the complexities inside the amps and the confusing side-effects of using one, it is not a complicated device and the mythology is nonsense. Honest.
photo courtesy Harry Brill of Tiger Audio, Inc
the 2 LEDs (one red and white wire each) are just under the cable-entry at the top.
Does it change the amp's sound?
Do I Really Need One?
How to use it
I'm grateful to several other folks, especially contributors to the Fender Discussion Page, for much of what I've learned so far.
If you've already got a footswitch and you find it helps in practice, be happy. The 1983 catalogue lists it as 'optional', which means not all the original owners bothered to buy one. Nearly All the Rivera-era Fender amps, including the Princeton Reverb II (Princeton Reverb 2), used the same footswitch. It's a simple design but very unusual - no other series of amps has used it. If you've found a 2-button footswitch and you're wondering if it will work with your PRII, have a look at the other end of the cable. If it breaks out into two stereo 1/4" jack plugs, one of them marked as 'red' in some way, you may have the right one. If not, don't even try it; though it might work with a bit of re-wiring - if it has 2 switches and 2 LEDs, 75% of the work has been done for you.
The Fender part no. was 017007. No other numbers, and sometimes not even this one, appear on the Fender original (thanks for this info, CJ and Donk).
* single-channel amp; 'red' button
selects lead (overdrive) effect
** 2 - channel amp; 'red' button switches channels
requirements for front panel settings or pull-switches vary from one model to another - check your amp's manual
thanks to PartsSmart, Dale Beachwood, Unquiet and others for confirming these compatibilities
schematics for these amps (not the footswitch) including Fender 75 and 140
Do I Really Need One?
This applies to PRII only; other amps, compatible with this switch, may operate differently
...an open question! I've got to say, once I'd built one, I only used it for a couple of numbers in my soul covers band, where I want to turn reverb on and off at either end of a solo. The 'lead' sound isn't that great and I never touch the other button. (The 'lead' sound is preamp distortion. I love the sound of this amp where 'lead' is NOT selected but the power stage starts to overdrive.) In addition the amp doesn't offer independent control of the tones for clean and lead sounds, and the amount of distortion isn't independently adjustable. I use a separate distortion effect box, a Marshall Guv'nor, but everyone's got their favourite. This is all subjective. My point is, you might want to think twice before going to any trouble to get a PRII footswitch. See also Does it change the amp's sound? below.
May 08; I now use my idea - the single-button reverb-only footswitch
My son Sam, who played in a
punk/thrash band, pointed out another option worth considering; the
Human Footswitch. They once played at a festival where
the promised backline (shared with other bands) wasn't very good
and featured an amp with the wrong footswitch. Channel switching
was needed by the guitarist, so they got a friend to stand by the
amp and operate the front panel "channel" switch when the
guitarist nodded at him. It's cheap, it's organic, it promotes
friendship, it makes someone else feel involved, no special parts
or soldering required.... everyone's a winner. In fact, the young
man involved even found "I'm with the band; I'm the Human
Footswitch" to be a successful chat-up line. Young people
How To Use the Original Design, 2-button Footswitch
This applies to PRII and Super Champ for sure; other amps, compatible with this switch, may operate differently
Plug it into the rear of the amp - there are 2 jack sockets labelled 'red' and 'plain' and your footswitch jack plugs should be similarly identified. Pull out the volume knob (as in "pull for lead".) When you turn on the amp, one or both of the footswitch LEDs may or may not come on initially but will alternate between on and off as you work the switches. One switch will turn lead sound on and off; the other will turn reverb on and off. The depth of these effects still depends on knob settings.
(download size about 2MB) advises us to fit some cable
clamps to the inside of the cabinet to act as extra
strain-relief on the jack plugs. It makes the advice sound as
though the footswitch was intended to be permanently connected and
be stored inside the cabinet. I guess some kind of clip to stop it
rattling around would be in order....
Where to buy a Footswitch ready-made
... if you're sure you really want one...
In the US, Voodooman made one
for a time, but there were, lets say, issues.... Google it....
But you're good-to-go with the
Chuck at Superior Music in Mt Juliet, TN, USA....
sells new reproduction Fender footswitches, used original, & New old stock Rivera Fender footswitches. This outfit also devote a lot of webspace to one of the best list of musician jokes I've ever seen.
In Europe, the ever-helpful Tube Amp Doctor sell a reproduction of the original - see here
Rivera also used to sell a footswitch for these amps. Makes sense, as Paul Rivera spearheaded the design of this amp range for Fender. If you find a Rivera-branded f/s with 2 stereo jacks and the 017007 part number (which was the Fender number too) then it's probably fine for this range of amps.Other outlets are (apparently - I haven't checked) Antique Electronics Supply, Mojo Tone, New Sensor, Magic Parts, and Hoffman. Let me know if you've tried any of these.
If you know another source,
please let me know.
Original Design Schematic/Wiring Diagram
The Fenderholic link doesn't seem to work any more so I drew my own... the small numbers (1-6) on the switch tags coincide with the instructions on "how to build one" below.
Does it Change the Sound of the Amp?
This applies to PRII only; other amps, compatible with this switch, may operate differently.
Aug 08; I am told the Concert clean channel sounds weaker when the footswitch is used. However, the following paragraphs refer only to the PRII.
Because the footswitch is
rare, and thought by some to be complicated inside (it isn't, see
the photo at the top of this page), a minor mythology has
developed about it. Let me try to set the record straight.
(1) Some believe there is a magical overdrive circuit or tonal circuit which is only accessible via the footswitch. This is not so. However...
(2) With the footswitch connected, both the lead sound and the clean sound will change. Some say they like the change, some say they don't.
This is because, with the footswitch connected, the 'lead' effect is switched in and out by an optocoupler wired from signal path to ground. This contrasts with footswitchless operation, in which the volume-knob-pull switch opens or closes the 'lead' signal path (no grounding action). Plugging in the footswitch introduces a resistance from the signal path down to ground, which is switched from high to low by the footswitch; so the sound has to be a little different. For a much more detailed explanation see Here comes The Science; how the effect switching works
On the Super Champ page you can see an official Fender drawing for this footswitch. My drawing above is based on a hand-drawn sketch, faxed to my amp's original owner by a Fender engineer. The two drawings are basically the same. One Super Champ user built a f/s to my drawing, got the 'loss in clean volume' problem described below, spent another 100USD on an original Fender f/s and still got the same problem. My page has been on the web since 2002 and I'm still open to corrections. But if you build a f/s according to these instructions and get the side-effects described on this page, that's normal; it's not a fault with the f/s.
I've had some helpful email
traffic from three PRII owners (using footswitches from various
sources, not this page), all of whom say the clean sound is
significantly quieter with the footswitch connected. This
may not be desirable, but strictly speaking it's not a fault and
is explained 2 paragraphs up from here. You can hear this
effect without getting a footswitch - it might help you
decide whether you want a footswitch or not. You need two stereo
1/4" (6.35mm) jack plugs. Get right-angled ones if you think you
might end up using these plugs to build a footswitch.
The amp now thinks it has a footswitch connected with 'clean' sound selected. You may find it's quieter or has a thinner tone than "clean, no footswitch". Switch off again before removing the jack plugs. The highest voltage on any of the tags is 6V DC so this shouldn't be a risky operation, but if your amp or the building wiring has a fault, there may be some unspecified danger, so don't touch those naked jack plug terminals while the amp is switched on.
The "loss of clean volume with footswitch" problem may have a solution here at post #5... plus, can be partially overcome by following the example of Andrew W in Canada, who says he gets his favourite sound like so; footswitch connected, volume knob pushed in, lead LED on. On his PRII , with this setting, (quote) "the gain of the clean channel increases significantly like a kind of boost. It definitely creates a kind of output overdrive effect, not to mention the lower mid range spikes significantly making the tone very full and 'chubby' sounding." I think this is something to do with the 0.003 uF capacitor wired across the lead level pot acting as an alternative signal path with a bit of frequency-dependent phase-shift . Andrew W is using the amp in a manner not intended by the designer, but it's not harmful, and hey.... most advances are made by misusing equipment, aren't they?. The down side of working this way is, you can't get the amp's lead sound with your foot. This doesn't matter to me, because (as I said above) I don't like the amps' own lead sound, and I use a separate stomp box for an overdrive sound.
I copied Canadian Andrew W for the first six years I had a PRII; the footswitch is connected, the volume knob is left pushed in, the lead LED is always on, and the footswitch is only used for turning reverb on and off. I didn't get his 'clean sound boosted'' phenomenon but the clean sound was acceptable. Now (May 08) I use the reverb-only footswitch.
There is another effect, which I think is psychological. Assuming you're using the footswitch as per the manual; if you have reverb on, and then also turn lead on, the reverb almost vanishes. This is equally true without a footswitch, but the footswitch allows you to compare the sounds instantly, and so the death of the reverb seems more marked. The reason why the reverb falls away like that is explained on my page about what the valves (tubes) do.
I'm always interested to hear
how yours behaves, especially if you've found a way to overcome
the 'drop in clean volume' problem.
This applies to PRII only; other amps, compatible with this switch, may operate differently
See here for another way; a one-button footswitch for reverb only; avoids the tone-sucking problem and could be best for you if you know you're never going to need the 'lead' sound to be footswitchable.
How Do I Build the Original Design Footswitch?
Photos of this project
Not difficult (the photos are intended to show it's pretty uncomplicated in there). It took longer to do this write-up than to build the footswitch. And the mechanical side of things (ie building something which will survive gigs, cables jerking and flexing etc) is more difficult than the actual electronics. Dec 2011 - on eBay in the US, you occasionally see a firm selling new clones of the original Fender chrome-dome type footswitch for this range of amps. I imagine they're well-made and properly specified, and the price looks reasonable. My only quibble is that they claim the footswitch contains parts which are "not inexpensive" which I take to mean "expensive"... if you've read that, don't let it put you off. It isn't true. See the photo at the top of this page - 2 switches, 2 resistors, 2 LEDs. Voila.
I hope techs and experienced hobbyists will forgive me for spelling things out at a simple level. When I start waffling about something which is blindingly obvious to you, please jump to the next paragraph.....
You will need some very basic soldering and metalworking skills, and...
- a suitable metal box; metal for strength and the necessary electrical shielding.
- cable, 4-core plus screen (shield), you choose the length: Fender's was 12 ft (3.6m). My cable is actually 2 screened twisted pairs, which has no advantage electrically but makes wiring up 2 jack plugs much easier. 5-core without shield is no good; the reverb signal actually travels up this cable and back down again, and without the shield it will pick up noise.
- cable gland with strain relief
- 1 red LED
- 1 green LED
- 2 resistors, 390 ohm, 1/4 watt or 1/2 watt
- 2 switches, robust for stomping on, Double Pole Double Throw (means there are 6 solder tags), latching action (= push on, push off)
- 2 stereo jack plugs, with one marked red in some way. If you're going to leave the footswitch plugged in all the time (ie even when transporting the amp), you might want to use right-angled plugs to stop them sticking out beyond the rear of the cabinet. I wish I'd done that now.
- rubber feet for box
- solder, glue, paint(?)
The above bits cost me about £11 (15 $US) in Oct 02, not counting the cable, which I had lying around in the shed and knew would come in handy one day. I love it when that happens.
Notes on the bits
LEDs have a long lead and a short lead. Don't cut them without some way of keeping track of which is which. On the schematic above, the short leads are the ones nearest the bottom of the page.
The 2 resistors are identical and it doesn't matter which way around you solder them into place. For connection clarity, I'm calling one (i) and the other (ii).
Check your switches with a continuity tester - you need to know which are the 2 'common' tags on each switch, and which are the tags sometimes connected to 'common' and sometimes not. Almost certainly the 'commons' will be in the middle of the switch. I'm calling the common tags 2 and 5. 2 alternately connects with 1 and 3 as you repeatedly push the switch. Same for 4, 5 and 6....
Stereo jack plugs have three separate conductors - the tip, the body (goes to the screen/shield/braid) and the one in between, called the ring. The back of the amp has 2 jack sockets for the footswitch - one labelled 'red' and the other 'plain', so we need to label the jack plugs accordingly...
I don't know what colours are the cores in your cable. At the other end, they're going to the stereo jack plugs. The screen goes to both jack plug bodies. The four internal cores are going to 'plain' plug ring, 'plain' plug tip, 'red' plug ring, and 'red' plug tip. So I'm labelling the four cores as below. I suggest you print this out and write your cable colours against my labels.
cable plain ring .......................
cable plain tip ........................
cable red ring ........................
cable red tip. .........................
Assembly; (a) in the box
Lay out the switches and LEDs in a way that makes sense to you. Decide where the cable entry should go. Drill out the box (5 or 6 holes = 2 switches plus 2 LEDs plus one cable entry, plus another hole if needed to screw the braid/shield/screen to the box). File the hole edges free of fine debris and don't leave any in the box.
My switches came with a couple
of metal washers. I soldered a short piece of wire to one of the
washers and used that as my box (shielding) connection.
Photos of this project
Fit switches and LEDs. The Fender original, right way up, in use, with the cable-entry away from you, has lead switch (and red LED) on the right. I use red-for-lead, but I put that on the LEFT in order to match what I'm used to from a previous amp. You choose your own layout and make your own adjustments if it's different to mine.
I drill holes for the LEDs which are a snug push-fit, push the LED through from inside to outside, and blob some epoxy glue (Araldite) on the inside to hold it in place. It's worth roughing up the metal area where the glue touches, to give it more 'key'. Separate the cable cores, turn the braid into a 'tail' which can be attached to the box, and push it all through the gland and into the box. Make sure the cable is held firmly by the gland (it's not the job of the solder connections to take the strain when someone trips over your footswitch cable).
Solder the connections as shown in the schematic above, or as detailed below as fifteen connections.
LEDs don't like being heated up, so don't solder too close to the LED body or for too long. Length of all connections is a trade-off between too short (connections under strain) and too long (flapping around and working loose).
Reverb switch; (on
right when my box is in use, so on left while working inside the
1 tag 1 to resistor (i)
2 resistor (i) other end to green LED long lead
3 green LED short lead to tag 6
4 tag 6 to red LED short lead
5 tag 2 to box
6 tag 3 to cable Plain Ring
7 tag 6 to cable Red Tip
(note, tags 4 and 5 on reverb switch are unused)
8 tag 1 to resistor (ii)
9 resistor (ii) other end to red LED long lead
10 tag 2 to tag 5
11 tag 5 to box
12 tag 3 to tag 6
13 tag 3 to cable Plain Tip
14 tag 4 to cable Red Ring
15 Shield/braid/screen of outgoing cable to box.
Assembly; (b) other end of
Now you need to solder the stereo jacks. They both should end up with the cable shield soldered to the 'body' tags, and the other 4 cores soldered to rings and tips as per your colour code chosen above. How you break out one cable to two jacks is up to you, but you need to make them robust and jerk-proof. Both kinds of jerk, in fact.
As I said earlier, my cable was easy to break out to 2 jacks because it's 2 screened twisted pairs. Both screens are attached to the box. The 'y' junction at the jacks end is reinforced with gaffer tape (duct tape). Not pretty but it works.
Another option is;
- cut the outer insulation back by about 200 mm (8 inches)
- push one jack plug body onto the cable (I forget this at least once in any project involving connectors)
- clamp the whole cable in the strain-relief of one jack plug
- wire up that plug normally (ie cut the 2 cores, intended for that plug, to a sensible length and solder into place) BUT leave the other 2 cores long and don't cut the 200 mm braid; solder it in place leaving most of it free
- push the 200mm of the 2 remaining cores plus screen back out of the jack plug (this may necessitate widening the hole on the jack plug body with a drill)
- push the other jack plug body onto these long cores and screen
- wire up the second jack plug
Another option might be to use heatshrink sleeving to protect a 'Y' junction of cable, where it splits off to go to 2 jack plugs. I think some places sell specially-shaped bits of sleeving for this purpose.
Just to make sure, I checked the following continuities at the jack plugs before using the footswitch...
body - box; connected permanently
tip - body; connects and disconnects as you work the lead switch
ring-body; connects and disconnects as you work the reverb switch
body - box; connected permanently
tip - body; no connection
ring-body; connects and disconnects as you work the lead switch
The moment of truth awaits..... see How to use it
The above advice is offered in good faith but I accept no responsibility for loss, damage, injury, death, destruction, pestilence, chaos etc etc. All the construction info above is in the public domain, but it's based on designs owned by Fender, and I'd appreciate it if you'd treat my write-up and photos as copyright 2002 Andrew Waugh. Thanks.
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