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Yamaha Pb-1 Preamp foot switch question/problem

J

Juan M

Aug 8, 2025
20
47
Albuquerque, NM
#1
Hello everyone,

My name is Juan and I am a new member here posting for the first time. I have been a user of both the yamaha b100iii series amplifiers as well as their rack preamp (the PB-1) and love them both to pieces. Of all the amplifier gear I have used for bass they stand as my favorites - for many reasons - above other gear which I also love by the likes of swr, trace elliot, peavey etc..

My question and problem I have is that i acquired an ART L-switch (ts latching type) thinking that it would function to open/close the parametric eq of my pb-1 pre, but unfortunately I get no function from it - the para eq and led the a 1/4" cable and L-Switch, but does not switch between on and off when the footswitch is depressed. Conversely, when i plug this switch into my yamaha b100iii amplifier foot-switch input jack, it turns off both the parametric eq stages, and allows one of the two to toggle between on/off. From what I have unearthed in deep dives into the switching in all the yamaha iii series amps and pres (both bass and guitar) is that they maintain their functions utilizing a 1/4" ts cable. Logically, I reached for the aforementioned ART switch and had no luck. I have the service manual and schems for the b100iii series amps (which shows an exploded diagram and parts list for the dual foot switch), as well as the original manual and service manual for the pb-1, but nowhere in either of the original pb-1 manuals does it show any mention of the foot switch. It does appear (based on the pcb schematic of the amp itself) that it should utilize a ts cable for latching, but I am curious if I am somehow something..

I attached the foot switch and para eq section of the pb-1 schematic (not b100iii - although i have that too) below.

para.jpg
yamaha pb-1 foot switch.jpg


Thanks for any input and help yall! Also.. if its supportive i would be happy to upload my scanned pdf of the service manuals for the pb-1 as they were very hard to acquire in physical form and just as hard to find online.
 
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#2
When an open cable is plugged into the jack, the PEQ should switch.

IF there is a front panel switch, it may need to be in a specific position (I don't remember)
 
#3
agedhorse said:
When an open cable is plugged into the jack, the PEQ should switch.

IF there is a front panel switch, it may need to be in a specific position (I don't remember)
Click to expand...
thanks for the reply. Neither the b100iii nor the pb-1 pre utilize an external, amp-mounted on/off switch. They turn "off" by centering the detents at zero. So in that sense they turn "off", but there is no button to turn them off.

Neither the b100iii nor the pb-1 led switch off when I plug in a ts cable only. When i plug in the cable AND the l-switch, the b100iii shuts off BOTH para eq's (that model has two as you may know) and can turn ONE channel on/off successfully, but when i do the same with the pb-1 the led stays on and the para functions wherever the knobs are set per usual regardless of hitting the foot switch while plugged in.

Also, i think i was editing the post as you replied, and I added and corrected a bit of what i hope is some more contextualizing information. Also, there is a really strange typo/fragement that (I can no longer edit it due to some sort of time limit) at the begining of that 2nd paragraph. I was basically just trying to describe what I stated above in this post.
 
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#4
Ok, I looked at the docs for the PB-1 and there is no front panel PEQ bypass switch so ignore than comment since I misremembered.

The footswitch is wired so that with nothing plugged into the jack the PEQ functions normally. When the connection is opened (by using an unterminated plug or cable), the PEQ relay opens and the PEQ mode is bypassed. I believe the LED goes out when bypassed and is on when active, but not 100% guaranteed since it's been a long time since I worked on one. IF plugging an unterminated plug into the footswitch jack doesn't bypass the PEQ, there's definitely something wrong. I am assuming the PEQ works normally without the footswitch.

The 100-III is an entirely different circuit and I'm almost positive that the footswitch is proprietary to this model. It's still a TS cable but there is level/threshold information that is carried on the switched line, it's not a simple contact closure. It's a very tricky circuit that uses analog switching IC's (if I'm recalling correctly). The switch drive unit is the threshold detector and analog switch circuitry that converts the two footswitches to a single TS cable and then back to switching two separate PEQ bypasses.

1756088047952.png



If you aren't using a factory footswitch, there may be nothing wrong with the amp.
1756088147040.png
 
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#5
thank you for your input and feedback here. i am begining to wonder if there is an issue with the inputjack for the foot switch on the pre, or perhaps something else going on in that part of the circuit. i am going to test another foot switch from a friend and see if that somehow does it. if not, i will have to dive in. its time for me to learn how to service my yamahas anyway, so perhaps this will be a good place to start despite other know issues. I will let you know what i come to find in the next day or two! i hope its simply a foot switch remedy!
 
#6
Juan M said:
thank you for your input and feedback here. i am begining to wonder if there is an issue with the inputjack for the foot switch on the pre, or perhaps something else going on in that part of the circuit. i am going to test another foot switch from a friend and see if that somehow does it. if not, i will have to dive in. its time for me to learn how to service my yamahas anyway, so perhaps this will be a good place to start despite other know issues. I will let you know what i come to find in the next day or two! i hope its simply a foot switch remedy!
Click to expand...
The 2 button footswitch is specific to the V3 amp, a regular footswitch won't work correctly.

On the preamp, the switching circuit is normally closed, it's a hard contact close/open without any additional circuitry such as LEDs involved.
 
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#7
Do this test. plug an instrument cable into the PB-1's foot switch jack. Short the tip and sleeve. if the PEQ works, then a only simple on_off foot pedal is required. A latching foot switch will not work. The schematic shows no support for a latching foot switch.

If the PEQ does not work without the foot switch, there is a circuit issue. Maybe as simple as cleaning the foot switch jack contacts with deoxit.
 
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#8
beans-on-toast said:
Do this test. plug an instrument cable into the PB-1's foot switch jack. Short the tip and sleeve. if the PEQ works, then a only simple on_off foot pedal is required. A latching foot switch will not work. The schematic shows no support for a latching foot switch.

If the PEQ does not work without the foot switch, there is a circuit issue. Maybe as simple as cleaning the foot switch jack contacts with deoxit.
Click to expand...
Being that a latching foot switch is an on/off switch, I'm not sure that I follow. But I appreciate your support. The para DOES function without any foot switch present. I will test a different foot switch asap and circle back!!
 
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#10
Sorry for the brain fart. Yes, the PB1 requires a simple on-off foot switch. I see from the schematic that the PEQ is relay controlled. The foot switch jack is normally closed. Inserting a plug opens the jack and inserts a loop with a latching switch to activate or defeat the PEQ.

I see that the ART LSwitch has an LED. That's why I suggested inserting an instrument cable in the foot switch jack and manually short tip to sleeve. Then just the switch would be in the circuit.


IMG_7323.jpeg
 
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#11
No problem at all, and thank you tons for the suggestion. I will give this a try!

After all my sleuthing, I have still found absolutely zero sign of any sort of foot-switch mention or inclusion in any of the pb-1 literature. I have found NO photos anywhere online with a switch (not even the owners manual or service manual, both of which i have a physical copy of) but i did manage to find this. I believe this may have been a pairing option for the pb-1. I actually got very lucky and just found one for sale for $20 and jumped on it. This one also happens to have NO led (per your mention of the led possibly being a component). I hope this does the trick!

zzrwtsym4jpalsbvpfk0.jpg
 
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#14
I will start with this s
6thplanet said:
You seem to be hung up on the switch thing. Did just plugging in an instrument cable into the foot switch jack shut the EQ function off?
Click to expand...

I think I mentioned trying just a cable above, and it does not turn off the para. Para works otherwise in a normal-on status. The reason the switch is coming into question is due to the fact that yamaha have a history of making unique configurations of switching - specifically for this itteration of the b series (the iii), and that I am at a loss about why a latching switch utilizing a tc cable and a simple on/off configuration wouldnt do the trick (or at least didnt when using the brand new ART l-switch that otherwise worked on other gear). I hope that makes sense. I am open to there being other problems - per my asking if it could be something else above, just to be super clear.
 
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#16
Very happy to report that this single switch, non-led, TS latching footswitch from Yamaha that I got is indeed doing the trick (Fs-1 model). Toggling between the single para eq on my pb-1 works successfully! As an aside, this FS-1 switch worked to actuate both of the para eqs on the the b100iii (not one OR the other, but both either on or off). I would still love to get the dedicated, dual switch made for yamaha b100iii or other iii series amps..

Now to figure out what is going on inside both of these switching that is causing them both to produce differing results.
I apprecaite everyones ideas and support and insight with trying various aproaches.
 

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#18
#19
beans-on-toast said:
Looking at this, the foot switch circuit is more complex than on many amps. Click on download at the bottom left. You need to find the proper foot switch for your amp.



www.audioservicemanuals.com

Yamaha b100 115iii 112iii bass amp service manual — Free Service Manual PDF | Audio Service Manuals

Read or download the yamaha b100 115iii 112iii bass amp service manual service manual free — 14 pages, PDF format. No login or registration required.
www.audioservicemanuals.com
Click to expand...
Which is exactly what I posted earlier, including the basics of how it works.
 
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#20
agedhorse said:
Which is exactly what I posted earlier, including the basics of how it works.
Click to expand...

Yes. The one that I posted in #18 (B100III V3) is far different from the one that was posted in Post #1. The schematic indicates that foot switch jack is TRS in this one. The PB-1 amp head circuit shows a TS jack. Two different approaches.
 
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