Nomenclature

[Luddy]

I'm still new to the forum and am pretty limited in my electronic expertise. I see a few terms used a lot:

#183
HRM (Hot Rubber Monkey, I now know)
Skyliner

It seems like #183 is a very special amp. What makes it that way?

It looks like HRM is a mod involving the tone stack. Does HAD have anything to do with this, or is this a mod that others have done?

I can't tell from reading here what exactly a Skyliner is. Is it from a particular era." But it is not an official model name like OTS and Steel Stringer. If I'm right, what is the parent name, if there is one?

[David Root]

Search #183, there are two quite long threads on it. In a nutshell, it apparently captures the best of later Dumble tone, and it used EL34s not 6L6GCs.

I say apparently because I haven't heard it, except MP3s which did sound good. Some MP3s are OK, some not.

Skyline is a late '80s Dumble tonestack, so called because if you look at it on a spectrum analyzer it the frequency plot looks like a skyscraper skyline.

[boldaslove6789]

HRM is Treble,Middle, and Bass controls for the Overdrive that are inside the amp on trim pots. Non Hrm is when the values are fixed and the Overdrive voice cannot be changed. These features were all in original Dumble amps.

The earlier Dumble Overdrive Specials had no HRM (Or Overdrive controls). Later HAD (Howard Alexander Dumble) added these HRM controls to further control and customize the sound of the overdrive for each individual player.

Skyliner refers to the clean tonestack but can also be a word to describe a certain era of ODS's. Certain amps that contain the Skyliner tonestack may have other things in common (like the values of the Phase inverter etc.)

Like David said #183 is an amp that was covered in detail here including a layout and a ton of other details etc.

[Structo]

I believe the Skyline tone stack appeared around 1988, give or take.

It involved changing the mid cap from .05uF to a .01uF and also changing the mid pot from 100K to 250K.

It mainly affects the mid range of course.

The reason for the HRM (Hot Rubber Monkey) was probably a result of complaints by guitarists that the OD tone was not quite what they wanted so they had to compromise the clean tone stack settings to achieve a better OD.

So what HAD did was make a daughter board with three trimmer pots, three caps and a resistor.

This freed up the clean stack on the front panel to control only the clean tone and the OD had it's own stack now but it had to be adjusted when the chassis is out of the cab.

Some enterprising souls have put a hatch cover on top of the cab that can be opened so you can adjust the HRM stack externally.

Also, the the Master Volume becomes the clean only master and the OD also has a master volume for the OD.

Ideally when playing in OD, the PAB (Pre Amp Boost) should be switched on so only the HRM stack is in effect.
Or you can leave it off and create some interesting tones with both tone stacks in circuit.

[butwhatif]

the biggest feature of the skyline eq is that the mid control does not cut as much bass, because it doesn't overlap the bass, and adjusts a higher freq midrange than the classic eq. it also cuts some of the low mid that the classic tends to have.