ODS-HRM (how shall I choose?)

[romberg]

I've decided to try my hand at building an ODS. My preference is not to build anything like an exact copy of any particular amp. But I would like to get a circuit somewhere in the ballpark.

I'm going to base my build on a Weber Halle kit as it has roughly the same topology and will keep the price near my budget. I like the idea of the HRM tone stack on the front panel. So, I'm keeping that and the transformers. But I'm gonna build my own boards and get other components to match an ODS schematic.

The question is which one? I've searched around this site and found schematics for ods-hrms and found ones for 101 (rev 1.4) and 102-v2 (rev 1.. I understand that neither of these are for any specific amp. Which is ok by me. I've also found schematics for 124 and 183.

At the moment I'm planning on using 102. Does this seem reasonable? I've also found a layout for it. I'm gonna be sorting out my own layout. But it would be helpful to study something that has already been done.

Anyway any tips or pointers would be appreciated.

Thanks,

Mike

[dreric]

My suggestion is that you are more likely to build a good amp by copying an established design. #124, 183 are good starters.

A lot of the Dumble mojo is the layout and component selections, the Halle does not share these and transformers are garbage.

Good Luck!

Eric

[Teleguy61]

The Halle is based on an SLO, not a D-type.
Ceriatones are much closer to D-style. 50 watt HRM kit Pack 1 is $495.
Source your own transformers and cab.

[M Fowler]

Java is based on TW Express.

[romberg]

If you look at the schematic it is similar. If one were to change about a dozen values or so it would be an exact match for the 101-hrm I found here. That is what I am going to do.

I was simply wondering if the 101-hrm or 102-hrm schematics found here are good (have been built etc). I'd like to find a schematic (and matching layout if possible) of something more correct is all. I know even then my amp is not gonna be a "real" ODS. There is only one fellow on this planet that can make those. I'm not him .

But I'd like to make my own that is somewhat similar. I've only been able to locate schematics for 101 and 102 which are hrms. I don't think 124 and 183 are. I just wanna know if I've missed something? That's all .

Mike

[Smokebreak]

Hey Mike , here's how I look at it, in it's most basic form :

The HRM amps can be viewed as hot-rodded-marshalls. The non-HRM amps(124,183,102,etc) can be viewed as hot-rodded-fenders. HRMs have 2 tone stacks, and the non-HRMs have 1.

Now some folks, or most folks will say that for an HRM to do it's thing in OD mode, the first tone stack, after the 1st stage(which is the stack for clean mode, and the same location that the non-HRM amps have), must be lifted using the PAB function(a tone stack lift). If you look at the HRMs like this, you'll see that these amps resemble a 4 gain stage, plate driven Marshall type, as they posses a stack after the 4th gain stage.

The non-HRM amps can be looked at as a non-reverb Fender(stage,stack,stage) in clean mode, then 2 added gain stages after that, and of course without the HRM stack at the end.

So yes, 124 and 183 are non-HRM.

If you're looking for an HRM that's straight OD, there is a "minimalist" schematic, which has the 1st tonestack removed. I built one recently and tweaked it to my own tastes : https://tubeamparchive.com/viewtopic.php?t=27241

There is also a Bluesmaster HRM : https://tubeamparchive.com/viewtopic.php?t=12875

I think the Weber "Heather" is their SLO, and their "Halley" is indeed their HRM. So if you used the Halley platform, you could do HRM or non-HRM. Of course the usual pitfalls of layout and component selection may apply.

Check out the "2nd gen" and "3rd gen" threads in the Files section, too, for more non-HRMs. There are more schematics and layouts there.

But you'll just have to build them all and see what you like best

Good luck!!

[romberg]

Thanks! I am gonna add a PAB relay and the three tone shaping circuits. The OD trimmer is getting moved inside and the pot on the first stage is getting removed (although it does look interesting). I intend to match a schematic from here (more or less). I just like the idea of the HRM tone controls not being buried inside the amp.

Thanks for the pointers to the 2nd and 3rd gen threads. I'll look into those. I'm just not 100% sure if the only difference between an HRM and a non-HRM is the tone stack at the end? Good working layouts will help me come up with my own.

Mike

[Smokebreak]

I'm just not 100% sure if the only difference between an HRM and a non-HRM is the tone stack at the end?
Mike

Well no, that is by far not the only difference, but the tip of the iceberg, I guess. You'll find pretty substantial differences within each realm, as well.

You can surely put all 6 tone stack knobs on the face, but that's a hell of a lot of knobs

[Luthierwnc]

You have already gotten some good advice. I would second the opinion that if you want a D, you have to make a D -- at least, the first time. Layout, parts, circuit, speakers, all of it. It is the only way to know if you are close.

The 102 is a good choice -- nice, middle-era amp that is very well documented with a lot of clips on the net to reference the tone. Modding it to an HRM isn't difficult if you think you need more grind in the OD.

Keep in mind these are not Strat-happy rigs. Buckers and Tele's work well but they aren't for channeling your inner Stevie.

Good luck, sh

[M Fowler]

You need to pick your D amp build based on what is it you want to hear in the end?

Read Max's posts and the video's he reference's various D generations tones or styles.

The RF 102 is very bright.

[romberg]

Thanks for all the advise everyone! Especially the "go back and look some more" kind .

I have done so. And I've decided I do want to try building a HRM variant. I have found two.

The first is the bluesmaster variant (I'd overlooked the bluesmater before) documented here:

https://tubeamparchive.com/viewtopic.php?t=12875

And the second is this "102" build that is itself a variant of the 101 schematic. I understand the 101 schematic is 101 as in "Introductory Quantum Mechanics 101" and not serial number 101. The 102 variant uses a skyliner tone stack and is this schematic:

https://tubeamparchive.com/files/ods_102_hrm_158.pdf

Have I missed any other HRM schematics? I'm gonna compare these two and pick one. Unless anyone jumps in and says "no don't build that one!".

Thanks again,

Mike

[ToneMerc]

The 102 variant uses a skyliner tone stack and is this schematic:

https://tubeamparchive.com/files/ods_102_hrm_158.pdf


Mike

I built a quad 6V6 HRM thats kind of similar with the standard PI.

TM

[Smokebreak]

That's a great looking amp. I like how you arranged the trimmers. What are your thoughts on the 4 x 6V6 vs 2 bigger bottles for the HRM?

[ToneMerc]

That's a great looking amp. I like how you arranged the trimmers. What are your thoughts on the 4 x 6V6 vs 2 bigger bottles for the HRM?

TY, Never tried this amp with only two big bottles; would be easy enough though, pull the quad of 6V6's and install a pair of big bottles and bias accordingly.

TM

[Max]

4 x 6V6 vs 2 bigger bottles for the HRM?

IMO it's a matter of personal taste and musical context. So you might even consider 2 x EL34 for a 50 Watt HRM. I've attached two pictures of an original 5th generation (so probably non-HRM - but who knows) ODS 50W with 2 x EL34. Picture source: http://www.gbase.com/gear/dumble-over-d ... 1990-black

Cheers,

Max