HRM, Skyline, bluesmaster for dummies

[PaisleyTube]

Hi all

Can anyone explain in a few words (or with some schematics) what the HRM, Skyline and BluesMaster mods are and in which models (70s/80s/90s?) they're used?

Many tia!

[Darkbluemurder]

Hi and welcome!

These are questions that are raised all the time. This is why there is the SEARCH function.

But it makes clear that we now have so much information on the forums that it becomes increasingly difficult to manage the information. As a question to Omar and the group: would it make sense to create subcategories in this section like "Buzzwords/glossary", "Preamp related" (including discussions on switches, tone stacks, snubber values etc.), "Power amp related" (phase inverters, OTs, negative feedback), "speakers", "Effects" (covering reverbs and D-lators)?

To your questions:

1. Skyline: refers to specific values in the tone stack after V1a (150k slope resistor, 390pf treble cap with 2200pf cap in series with 250kA treble pot, treble boost shorts 390pf cap, 0.01uF midcap with 250kA mid pot, 0.1uF bass cap with 500kA bass pot, 10k to ground from bass pot CCW and 0.001uF cap from CW to CCW lugs on the bass pot. Mostly used in the 90s HRM models which brings us to

2. HRM: Hot Rubber Monkey or Hot Rod Marshall: refers to a 2nd tone stack after V2b.

3. Bluesmaster: a variation of the HRM amp.

All schems are in the Dumble files section.

[dogears]

Actually, a few corrections.

The treble pot is 250Kb.

The midboost cap is a .002uf on every amp I have seen. When combined with the 390pf treb cap, the net is 326pf. If you use the .0022, you get 331pf and the midboost is more extreme. You can hear the difference. Maybe a little subtle, but there.

Lastly, there as many as dozens of non HRM Dumbles with the Skyline stack. Even the infamous Ultrasound tan one. It was his standard in the 80s....

To your questions:

1. Skyline: refers to specific values in the tone stack after V1a (150k slope resistor, 390pf treble cap with 2200pf cap in series with 250kA treble pot, treble boost shorts 390pf cap, 0.01uF midcap with 250kA mid pot, 0.1uF bass cap with 500kA bass pot, 10k to ground from bass pot CCW and 0.001uF cap from CW to CCW lugs on the bass pot. Mostly used in the 90s HRM models which brings us to

2. HRM: Hot Rubber Monkey or Hot Rod Marshall: refers to a 2nd tone stack after V2b.

3. Bluesmaster: a variation of the HRM amp.

All schems are in the Dumble files section.

[ayan]

Actually, a few corrections.

{snip}

Lastly, there as many as dozens of non HRM Dumbles with the Skyline stack. Even the infamous Ultrasound tan one. It was his standard in the 80s....

Perhaps we should consider making that late 80s. The early 80s all had the classic EQ with the Deep switch, etc. The earliest Skyliner conversion I have heard of dates from 1986; the earliest chassis reflecting the MID switch that I know of dates from 1987.

Cheers,

Gil

[chris_sanford]

Actually, a few corrections.

{snip}

Lastly, there as many as dozens of non HRM Dumbles with the Skyline stack. Even the infamous Ultrasound tan one. It was his standard in the 80s....

Perhaps we should consider making that late 80s. The early 80s all had the classic EQ with the Deep switch, etc. The earliest Skyliner conversion I have heard of dates from 1986; the earliest chassis reflecting the MID switch that I know of dates from 1987.

Cheers,

Gil

A question for the historians: what is the earliest HRM example you are aware of? #182 is the earliest one I personally know about. Anyone seen an older one?

chris

[dogears]

Yep... But, he did convert a lot of amps, including many of those early classic stack ones!! My buddies late 70s one for instance....

Perhaps we should consider making that late 80s. The early 80s all had the classic EQ with the Deep switch, etc. The earliest Skyliner conversion I have heard of dates from 1986; the earliest chassis reflecting the MID switch that I know of dates from 1987.

Cheers,

Gil

[Fischerman]

But it makes clear that we now have so much information on the forums that it becomes increasingly difficult to manage the information. As a question to Omar and the group: would it make sense to create subcategories in this section like "Buzzwords/glossary", "Preamp related" (including discussions on switches, tone stacks, snubber values etc.), "Power amp related" (phase inverters, OTs, negative feedback), "speakers", "Effects" (covering reverbs and D-lators)?

At least one other forum I frequent (totally different topic) has a sticky called 'The Anthology of wisdom..." and it contains some posts/threads that were considered so good that they had to be preserved. Plus it prevents people from asking the 'basics of the basics' over and over.

Just a post (i.e. a stickied post or in placed the Files section) stating what all these 'Dumble specific' terms mean would be great. I know that more than once I've done a search and been so frustrated by the time I was done I felt like I had dealt with some government agency. Like a while back I was looking for Bluesmaster info and then after all my searching was like; "You gotta be kidding me...it's just a Marshall PI...that's IT!" All that searching just for 'Bluesmaster = Marshall PI'.

[ayan]

Yep... But, he did convert a lot of amps, including many of those early classic stack ones!! My buddies late 70s one for instance....

Perhaps we should consider making that late 80s. The early 80s all had the classic EQ with the Deep switch, etc. The earliest Skyliner conversion I have heard of dates from 1986; the earliest chassis reflecting the MID switch that I know of dates from 1987.

Cheers,

Gil

I suspect he probably converted all of the old amps he could get his hands on. There is one 1982 (6 months older than RF's first "owned" one) specimen here in L.A. that was not converted, and the reason is that other people went "under the hood" to add an active loop to the amp. The owner suspected Dumble would be upset and refuse to work on the amp, so he never bothered trying to get any of the upgrades.

I still stand by my statement, however; while HAD may have converted all minus one amp, the earliest date I know of for conversions is 1986. For what its worth, according to RF, most of TTYD had been recorded by 1984 or so; he (joined and) quit Miles' band in 1986 to wrap that project up and start toruing as a solo act. It may well be that TTYD has pre and post conversion tones in it, assuming RF got his Skyliner conversion early on. More room for speculation. TTYD (the whole recording), as well as live RF footage from the early and mid 80s, definitely sounds brighter and : smaller" than his later tones.

Gil

[Funkalicousgroove]

I heard from a pretty reliable source he actually used EV's and a Dumble 4x12 (I got to play through that very 4x12 during my shootout) for alot of that recording.

I had never seen a Dumble 4x12 before that, it was kind of neat in that it was basically a TV sized cab that had a center baffle making it 2 2x12's stacked.

I think it matched the Tan head that sometimes resides in a green combo cab.

[PaisleyTube]

Thanks for all your replies!

I guess (ha ha) these questions are asked over and over but maybe it's (indeed) a good idea to make a sticky or document about this in the files section.

Seems to be a great forum, again thanks!

[johan]

Actually that's a very good idea. Do a FAQ for all us "dummies".
Just to copy and paste what's already written here.

[Ed Bonatto]

Well, since we are discussing everything you ever wanted to know about dumble but was too shy to ask, I allways wanted to know (and I hope it is no taboo or anything like that): what ever happened to Dumble? Are any amps being produced, or/and when did it stop, and if not asking too much... why???

I've searched quite a lot without finding much about this theme.

Thanks

[novosibir]

... what ever happened to Dumble?

Interesting quest! I'm also curious, what he's doing at the moment! Counting his money every day, or what?

He himself should register to this forum and directly reply to some quests

Larry

['67_Plexi]

I know for a fact he will still make amps. It costs $$$$$$$$$$$$$$ though.

['67_Plexi]

and you have to be REALLY famous !!!!