#124 Build Questions

[martin manning]

Much better. Do all the controls work as expected?

[lgehrig4]

Much better. Do all the controls work as expected?

I had a little time to give it a test and here are my initial observations.

- The volumes and master work as they should.
- TMB controls have no effect unless the Mid switch is down (I think in the middle position too). Even then they are fairly subtle compared to other amps.
- Mid switch provides boost in up position, but nothing in the other two. Though it would so since its a 3-way. (ie. mid boost - flat - mid scoop)
- Rock swich up is just bassier. Middle position sounds more "rock" like. Is that the intention?
- Sounds like PAB switch in the back adds to the mid boost when set to manual.
- Presence is subtle as well. Something changes from 0 to 10, but it doesn't sound like you are adding or removing presence. More like the presence is there the whole time but the character of the high frequencies are changing a little.

The "A Collection of #124 Information (Schematics, Layout, etc.)" thread mentions Effects 'Send' and 'Return', but I have 'Power Amp' and 'Preamp'. Is this the same or did I build a different version of #124?

[67plexi]

From what I can see from your photo your relay is wired wrong whats up with the yellow jumper ??

[lgehrig4]

From what I can see from your photo your relay is wired wrong whats up with the yellow jumper ??

Thats the way its wired in Martin's layout and eyelet board document, except in the layout NC1/NO2 are jumped via the trace.

Screenshot 2025-04-09 at 10.26.30 PM.png

Screenshot 2025-04-09 at 10.29.16 PM.png

[martin manning]

- The volumes and master work as they should.
- TMB controls have no effect unless the Mid switch is down (I think in the middle position too). Even then they are fairly subtle compared to other amps.
- Mid switch provides boost in up position, but nothing in the other two. Though it would so since its a 3-way. (ie. mid boost - flat - mid scoop)

The mid boost switch is supposed to be an on-on type, no middle position. With an on-off-on the middle position will be the same as mid boost off. When Mid Boost is engaged, you have a larger treble cap passing more mid frequencies.

- Rock swich up is just bassier. Middle position sounds more "rock" like. Is that the intention?
- Sounds like PAB switch in the back adds to the mid boost when set to manual.

The middle position of R/J is the same as PAB, and the Jazz setting should have less bass than Rock.

- Presence is subtle as well. Something changes from 0 to 10, but it doesn't sound like you are adding or removing presence. More like the presence is there the whole time but the character of the high frequencies are changing a little.

Most of the effect will be in the last 20% of rotation.

The "A Collection of #124 Information (Schematics, Layout, etc.)" thread mentions Effects 'Send' and 'Return', but I have 'Power Amp' and 'Preamp'. Is this the same or did I build a different version of #124?

Same thing.

[lgehrig4]

Thank you!

The mid boost switch is supposed to be an on-on type, no middle position. With an on-on-on the middle position will be the same as mid boost off. When Mid Boost is engaged, you have a larger treble cap passing more mid frequencies.

So annoying. I ordered the switch based on the "124 BOM Joost 1.2 AMPGARAGE" doc I found here

Most of the effect will be in the last 20% of rotation.

This sounds about right. So the only issue I have is the extra position with the mid switch. I can live with that.

I'll test the effects loop and work on FET bias.

Thanks again!

[martin manning]

So annoying. I ordered the switch based on the "124 BOM Joost 1.2 AMPGARAGE" doc I found here :(

It's kind of an unwritten rule that everyone is responsible for checking all information found here. No guarantees on anything. That said, ordering small toggle switches can be annoying. I have a whole collection of wrong types. Maybe you can add a post to the thread with the BOM noting that error so the next guy doesn't get the wrong switch.

So the only issue I have is the extra position with the mid switch. I can live with that.

I'd change it.

I'll test the effects loop and work on FET bias.

Your FET bias is actually pretty good right now since you are dropping close to half of the supply voltage across the drain resistor. If you want to, you could replace the 2k source resistor with a 1k8 and see if you like that any better.

[lgehrig4]

It's kind of an unwritten rule that everyone is responsible for checking all information found here. No guarantees on anything. That said, ordering small toggle switches can be annoying. I have a whole collection of wrong types. Maybe you can add a post to the thread with the BOM noting that error so the next guy doesn't get the wrong switch.

Will do! I want to thank you for all the time you spend assisting me during this process! Same for anyone else who jumped in.

It sounds real good. Not as intuitive to dial is as I expected but I found two really good overdriven tones already. This is with crap tubes, V30's and an amp that isn't burned in yet so I'm looking forward to dialing this in

[martin manning]

No problem, I get a charge out of watching a new amp come to life. The ODS is capable of a very wide range of sounds, more than is generally understood from the players who are known for using them.

[pottedplant]

I've been following this thread as I am also building a 124 and it has been invaluable to me, watching you all hash out the issues methodically is quite helpful in avoiding any issues on my own build and this site is such a gem for that. Martin you have the patience of a saint haha

One thing this thread taught me was to check my resistors before installing them and I'm sure it will help me when I assemble my boards, you guys are awesome

[lgehrig4]

I've been following this thread as I am also building a 124 and it has been invaluable to me, watching you all hash out the issues methodically is quite helpful in avoiding any issues on my own build and this site is such a gem for that. Martin you have the patience of a saint haha

One thing this thread taught me was to check my resistors before installing them and I'm sure it will help me when I assemble my boards, you guys are awesome

Definitely a good idea. Next time I would even go one step further and test each with the DMM to use the ones closest to their marked values.

I am generally impatient but I took my sweet time with this one. Build the boards over a month ago and checked them over multiple times, and still missed that resistor. This one was definitely a learning experience. It was my 5th build (JMP50, 5F6A, 5E3, and TW Express) but up until now I've been just following layouts for the most part.

[pottedplant]

I've been following this thread as I am also building a 124 and it has been invaluable to me, watching you all hash out the issues methodically is quite helpful in avoiding any issues on my own build and this site is such a gem for that. Martin you have the patience of a saint haha

One thing this thread taught me was to check my resistors before installing them and I'm sure it will help me when I assemble my boards, you guys are awesome

Definitely a good idea. Next time I would even go one step further and test each with the DMM to use the ones closest to their marked values.

I am generally impatient but I took my sweet time with this one. Build the boards over a month ago and checked them over multiple times, and still missed that resistor. This one was definitely a learning experience. It was my 5th build (JMP50, 5F6A, 5E3, and TW Express) but up until now I've been just following layouts for the most part.

I totally feel you on this and I will take your advice using the DMM to confirm. I had a few wrong ones in a pretty complex phaser/panner pedal build I did years ago by kit, that one took months to figure out because the bands were impossible to see even back then when I had the eyesight of someone in their twenties lol Now it's impossible to read even the diode type without getting my phone out and zooming in lol

I am loving this build! I hope you post some clips!

[lgehrig4]

After spending more time playing and testing the amp, I have a couple of questions.

First, the TMB controls. They only seem to be active in the Rock or Jazz settings when no mid-boost is applied. One there is a boost from either the mid switch or PAB switch these knobs do nothing.

Second, the overdrive is active when the switch is in the pedal position (as opposed to manual) I went over the wiring multiple times and it is exactly as in the layout. The PAB switch works in the correct manner. It still works as uit should but I cannot figure out why its reversed.

Brown wire from the PAB switch, runs to the diode of the relay with the 22M resistor
Blue wire, form the Overdrive switch, runs to the diode of the relay closer to the preamp board

rear-switches.jpg

rear-switches-2.jpg

[martin manning]

First, the TMB controls. They only seem to be active in the Rock or Jazz settings when no mid-boost is applied. One there is a boost from either the mid switch or PAB switch these knobs do nothing.

Mid boost does nothing but increase the treble cap by shorting the smaller of the two in series, which could be what you are hearing. You could do some multimeter checks to confirm. PAB lifts the tone stack, so the TMB controls should be inactive when it is engaged.

Second, the overdrive is active when the switch is in the pedal position (as opposed to manual) I went over the wiring multiple times and it is exactly as in the layout. The PAB switch works in the correct manner. It still works as uit should but I cannot figure out why it's reversed.

Toggle switches have the contacts opposite to the slide switches shown in the layout wrt the "up" vs. "down" position. I'm not sure why one of them seems to work as intended and the other one doesn't. Might have something to do with the PAB being connected differently. In the HAD 124 manual PAB is accessed via the center position on the R/J switch. I have both pedal-manual switches wired the same in mine, giving me two ways to manually select PAB.

[GAStan]

Second, the overdrive is active when the switch is in the pedal position (as opposed to manual) I went over the wiring multiple times and it is exactly as in the layout. The PAB switch works in the correct manner. It still works as uit should but I cannot figure out why it's reversed.

Toggle switches have the contacts opposite to the slide switches shown in the layout wrt the "up" vs. "down" position. I'm not sure why one of them seems to work as intended and the other one doesn't. Might have something to do with the PAB being connected differently. In the HAD 124 manual PAB is accessed via the center position on the R/J switch. I have both pedal-manual switches wired the same in mine, giving me two ways to manually select PAB.

This got me too. If you look at the #124 pics it had slide switches on the rear panel and toggle on the front. The layout accurately reflects this. When I built my #124 the chassis I got had holes for toggle switches both front and rear but like you, I wired exactly as the layout shows so the front panel switches worked but the rear were reversed.
I felt silly when I realized what had happened