Modding a non-HRM 124 to HRM... any info appreciated

[Joost]

I have been reading posts for a few hours, but it seems it's really a mixed bag as far as opinions go.

Also, I found the bluesmaster layout, but I was wondering if anyone ever did a schematic for modding a low-plate ODS with skyliner update to HRM.

I am really in love with my clean sound on my Too Rock with dumbleator. The power amp works great as well (when I use it from the return of the internal dumbleator as a separate second power amp for stereo playing.)

It's just the OD that just plain sucks. I've tried some simple mods as well as different tubes of course, but can't get the basic sound right. It's like a fuzz pedal or something. I want some basic blues/rock overdrive. Maybe the tweak-ability of the HRM OD section will get me there.

However, I do not want it to mess with anything else on the amp as that is just great!!

[boldaslove6789]

If your OD doesn't sound great try changing the lead dress to match HAD's wiring. Follow the wiring as closely as you can as it will make a huge difference.

All the 124 pics are here (go to 124):

http://www.roblivesey.com/dumble/

[Structo]

Joost,
Due to your amp having the Dumbleator built in, it is very crowded in there.

Not sure where you would squeeze in the HRM board.

If you have the money, you should probably build another amp, this time HRM.
You can also play with Bluesmaster values as well on that amp.

I think it's possible to dial in your OD channel.

But remember, your amp is brand new!

Let things settle down for a while before changing things.
It may just mellow out and sound great after 40 hours or so of operation.

[jborders5]

I'd mod it to a high plate using the #102 & #183 layouts before trying the HRM route.

[trane34]

Not sure if this would apply to your rig but I noticed on my 124 low plate skyliner that the OD smoothed out if I kept the volume on my guitar down (about half way with hums and 3/4 with sc) and let the amp do the work. Also the masters both had to be opened up. It took me awhile to figure this out as I'm used to playing with the volume of the guitar turned all the way up especially with single coils.

[Structo]

This is where the Dumbleator comes into play.

You have both the pre-Gain and Master up between 12:00-2:00 where the tone resides and then control the "Loudness" with the Dumbleator Output pot.

Using it as a Master volume.

After building my D'lator I understood what everybody was talking about.

[Joost]

Thanks for all the replies so far. I have tried matching the lead dress as closely as possible. As for playing time, I do have quite a few hours on it since I finished the basic amp back in May.

It's just that I don't like the basic character of the amp's overdrive so it seems. I have tried smoothing out the high-end with a few caps, but that didn't fix the basic problem. There's just too much gain too soon and I can't get a crunchy blues/rock OD sound on any setting. I even lowered the value of the gain trimmer to exactly 361k like the original 124.

I feel like it's clipping too soon, like I need more headroom or something.

I'm going to try jborders5 suggestion first to change the OD to 102/183 specs.

I'll stick with modding the non-HRM overdrive first.

[Luthierwnc]

In order I'd try:

a) heisthl's not-the-ayan mod,

https://tubeamparchive.com/viewtopic.ph ... +mod#56875

b) 220k/150k plates on the OD,

c) 220k/150k on V1

sh

PS what's resistance to ground on the OD trimmer?

[hans-jörg]

Hi,
I made the same out of the same reasons (OD to fuzzy).
I changed the OD (V2) to 183/102 Specs plus the Ayan mode (cap/R in front of OD entrance). What I didnt till jet (because I done it in the morning) is to change the cap values at V2 Anode/Cathode from aprox. 300p to 25p. First check with guitar sounds way better. I also lowered the voltage at V1/V2 because allways over 200VDC. Now its fine from around 189V to 195V both. But as I wrot there was no time to find out how well the change was. I also lowered the coupling cap value of V2b (OD in) from 0.01µF to 3n3µF but I´m not shure if I´ll change it back. First I have to play a while.
Best
Hans-Jörg

[Structo]

If you are using the higher plates now, I would re-adjust the OD trimmer.

I seem to remember you used the #124 value trimmer?
You should install a 100K trimmer.
The 220K feeds that.

Measure this with the amp fully powered up, off standby and with the OD on.
Be CAREFUL.

But before you turn the amp on, clip your meter probes to measure resistance with one probe on the trimmer wiper (Middle lug) and the other probe to chassis ground.

Make sure the speaker is plugged in.

Gain and master pots at zero.
OD on.

Set it to between 20K and 25K or so.

I find the higher that is set, the fuzzier the tone gets.

To me, fuzzy means the low fuzz tone type tone and the word fizzy, means the top end buzzy/ fizzy tone.

[hans-jörg]

Hi Tom,
yes I meaned FIZZY.
And yes, I changed the trimmer too (to 100k). For 1st power up I installed it by ear but I`ll measuer the value (to see if I have the right taste).
But for any case: I learned that this amp is greate with at least half power (volumes) open. If you want a nice bedroom or livingroom level you need the recovery of the D´letor (wich I have !!)
I was very happy in the rehearsal room but for lower volumes I want to shape it.
At least I dont have a propper speaker at home. Now I mounted a Celestion G12T75 - to dark for low volume. The other is a Eminence Guitar Legend 12". Way better but no balls, becomes soon wammy or so.
AND both are 16 Ohm.
I have to try my 2x10" bass box with Neodyms - maybe...?
So all this together makes me unsatifyed for playing at home ... not rearly - there is still the cellar

But lets get back: do you agree that I have to change the snubber too?

Best

Hans-Jörg

[Joost]

What is the consensus on trimmer and pot values? The 124 has a 360k trimmer whereas 102 and 183 have 100k trimmers. Then there are 100k drive pots as well as 250k drive pots and the same goes for ratio/volume pots, either 100k or 250k.
The trimmer should be 100k but what kind of drive and ratio values do you suggest?

[Structo]

Scott (Dogears) has stated that the 220K into the 100K trimmer is the grail tone on OD.
But it is subjective.

Marcos who owns a 2nd Generations ODS (I think) says on the notes on the #40 layout where he talks about dialing in the OD tone.
Below is the #40 with the notes on the side bar.
The notes on various layouts can be very revealing.

I can't remember what I have for OD pots at this time in my amp.
I believe I have a 250K on the Drive pot but I can't remember if I also put a 250K on the Ratio or Volume.

I do know that using the 250K on the Drive pot thickens the tone.
To some that may sound mushy or muddy.

So you just have to try it to see.

[Joost]

I'm going to go high-plate on the OD and change the OD trimmer to 100k, see how that sounds and then slowly updating the specs to 183 OD, listening to all the changes.

Thanks so much!!

Scott (Dogears) has stated that the 220K into the 100K trimmer is the grail tone on OD.
But it is subjective.

Mario who owns a 2nd Generations ODS (I think) says on the notes on the #40 layout where he talks about dialing in the OD tone.
Below is the #40 with the notes on the side bar.
The notes on various layouts can be very revealing.

I can't remember what I have for OD pots at this time in my amp.
I believe I have a 250K on the Drive pot but I can't remember if I also put a 250K on the Ratio or Volume.

I do know that using the 250K on the Drive pot thickens the tone.
To some that may sound mushy or muddy.

So you just have to try it to see.

[Joost]

I'd mod it to a high plate using the #102 & #183 layouts before trying the HRM route.

So I've been reading a lot today and found a thread that said HAD liked symmetry in the valves, which was why his plate resistors were generally the same over V1 and V2. Now, as you know I do not want to mess with v1 but would that mean I can't change the plate resistors (and cathode resistor/cap according to rule of 66) on v2?