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#1
Building a 100W Dumble clone over my month long break. Another Overdrive Special (ODS) but this time 100W and the Hot Rubber Monkey (HRM) version.

HRM has a different overdrive section and a few minor changes to the clean channel. The entrance to the OD is quite different from non HRM ODS'. The biggest difference though is the post OD tonestack. The controls are adjustable via trimmers in the chassis. That way you can match your overdrive sound to your clean sound, super smooth and silky. I got a really neat mod for the tonestack, more when I get there.

Another big difference is the plate load resistors and cathode resistors are quite different values than my previous #124. Should be a totally different beast.

100W will offer more bandwidth and girth than a 50W and just feel more full. 100W is only a mere 3dB louder than 50W so it's not a "volume thing".

Got in on a group buy of chassis happening at another forum. The two guys who put the group buy together live fairly close to me. Local metal shop and silk screening places made up the chassis. The chassis is incredible rugged and well built.

The iron I got at a local hi-fi place I have dealt with before. Had a 20% off sale so I got a solid deal on Hammond PT and OT. The iron is beastly, PT, OT and choke weigh over 20 pounds. Shipping all that iron would have been $$$.

Got orders coming in from Mouser and Antique Electronic Supply. Still need to make the eyelet board and etch four more PCBs.






Last edited by kurtlives91 at Dec 15, 2009,
#2
im excited to see another amp build. i love your work chris

edit: quick question about the 100w to 50w comparison, how does it handle the bandwidth better and have more girth? wouldn't a higher wattage have a more sterile sound at comparable volumes?
Last edited by blandguitar at Dec 15, 2009,
#3
How would the sound be sterile comparing a 50W and 100W at the same vol?


100 watt amps will seem louder due to the increased bandwidth propagated by the extra output tubes, this decreases the load on the tubes themselves so you don’t get the anomalies associated with a tube about to clip. This gives the amp more headroom, increased low end, better touch sensitivity, and a clearer cleaner top end, in effect making the amp seem louder since you are hearing a clearer richer sound produced.

The difference in volume between a 50w and 100 is about 3db (barely distinguishable). I think playing through those early 100w Twins, Plexis, Hiwatts has fooled some into thinking a 100w guitar amp is overkill. IMO this rule doesn't apply to these amps since most of the breakup character is produced by a gradual increase in gain and a tight powerful output section
#4
Man, this is gonna be cool


I think he's talking about how lower wattage amps can be made to break up at lower volumes. The higher wattage, having more headroom, would be cleaner at the same volume.

This is what I've always heard, I don't know if that applies in this situation though.
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Quote by handbanana
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#5
That looks really nice. Any chance you could PM a link to the schematic?

Is it going to be a head or do you have a cab for a combo?

Are you going modify the circuit any? Either way it is going to be an awesome amp.
#6
http://ampgarage.com/forum/files/ods_102_hrm_158.pdf No secrets

Its going to be a head. Most Dumble's were heads, I don't like the look of the combo versions. Only a select few speakers "work" with these amps so best to have a cab with them imo.

One mod I did on my 50W non-HRM ODS was switchable mid cap which I really like, probably do that again after I'm done. Got a neat idea for the overdrive channel. Going to be adding another relay and having a three button foot switch instead of stock two. More on that when I get there though...
#7
Bandwidth and power output are not at all related in the simple manner you imply.
You can have low power amps with broader bandwidths than higher power ones.
Many (frequency dependent) factors determine an amplifiers bandwith.
In the case of a output section substitution such as this, it is probably the choice of output transformer quality and feedback ratios that will have greatest effect on any difference in the bandwiths of the two amplifiers
#8
^the people I have talked to compared 50W amps to 100W amps with the same components and specs. Ya their are tolerances but ya the output section also makes a difference.

Why don't you tell us all the relationship between bandwidth and power output? Seems like you got a few things to say.


This amp is usiong a quad of EL34s btw. Forgot to mention that.
#9
Didn't know you finished your other Dumble build, do you have any sound clips?
Quote by envoykrawkwar7


edge11
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best thing ive read all day

[feel free to sig this statement]

Gear:
Esp Ltd Ninja 600
Esp Ltd F-50
les paul elite
5watt jcm800 clone
Roland jc-55
Crate V33
Jca20H
Ibanez tubescreamer ts9
Keeley ds-1
#10
Looking forward to this build, as usual.

2 quick questions:
  • Are all these amp and pedal builds because you're still hunting that tone for the Moircaster?
  • What is a simple fix to tame the almost shrill highs, build a more authoritative mid, and get a tighter low?


BTW, you need to assemble/build a Strat, after assembling/building a Mahogany/Maple LP or Super Strat with 2 Humbuckers. This will ensure a new/different amp building frenzy. I guarantee it.

#12
Quote by kurtlives91

<snip>
Why don't you tell us all the relationship between bandwidth and power output? Seems like you got a few things to say.

<snip>
.


Bandwidth is defined by where the half-power points of an amplifier fall on a power output vs frequency plot.
These points are determined by how the frequency dependent devices (such as capacitors and inductors) within the particular circuit are configured and interact, not upon the mere magnitude of the gain of the pass band or upon the nominal gain of an active device used.
I encourage you to read elementary Elec Engineering or electronic texts on this subject rather than expect me to provide my woefully inadequade sumaries in here by way of my own one-finger typing skills.
#14
Intro to electrical engineering books are very interesting and useful when looking at and trying to understand amps and pedals. I'd for sure get one if you can, used on eBay should yield a good deal. Also, if you look around I'm pretty sure there are books actually on tube amp design, might be worth looking into.
Chain:
Fingers -> Schecter Damien FR -> Fulltone OCD -> ABY Box -> Bugera V22 / Peavey 6505+
#15
Got in a Antique Electronic Supply and Mouser order last week and early this week. So I did a bit of machine work on the chassis getting everything to fit just right. Installed the hardware and everything is looking good so far.

Still need to etch the PCBs and make the main eyelet board. That will have to wait till next week.










Happy holidays!
#19
Quote by blandguitar
the transformers are under the way the head where the boards and internal wires go. judging by the way the letters read. is it apart of a larger enclosure?

Meadows
Quote by Jackal58
I release my inner liberal every morning when I take a shit.
Quote by SK8RDUDE411
I wont be like those jerks who dedicate their beliefs to logic and reaosn.
#20
Hmm well it's just one chassis, not sure what you mean.

I still need to add the two relay PCBs, FET PCB, PSU PCB and the eyelat board. It all fits in there, will be tight. Need to drill the mounting holes for all those boards once there done.

Some mounting holes will be under the OT so those bolts will need to be counter sunk.
#24
This is looking pretty good. I've looked at these amps, and played on one (not this one, the 50W). Can't wait to see how this turns out. Maybe try it myself after my fender amplifiers are done.
#25
Made the PCBs and got the eyelet board over the past week or so. Took a bit of work to machine the chassis so everything fit just right. Everything fits as it should now.


Useful new tool, chassis cradle



Here you can see the main eyelet board, two relay switching boards and the FET board.


The power supply (PSU) board





Here are what the traces look like. They are supposed to somewhat mimic the hand drawn artwork that real Dumble's have.



Hoping to complete the amp by the end of next weekend. Got two other amps to build (not for me) and a 212 cab to finish off (for my Dumble's). Going to start populating the eyelet and do some wiring tomorrow, hopefully.
Last edited by kurtlives91 at Jan 2, 2010,
#26
We still interested?


Anyways here is a pic of the Dumble 212 cab I have been working on. I found plans for a true Dumble 212 back in early September. My dad and I worked on the cab off and on when I was home on the weekends. It took a lot of time, trial and error to learn how to make good solid, precise finger joints. With the finger joints, glue and cleats the cab is rock solid. The cab is also perfectly square, makes fitting baffles and back panels easier. Today I took a round over router bit to the edges. A light sand with the rotary sander and here it is now.

Going to cut the back panel this week. Then comes tolexing on the weekend. It's either black tolex with white pipping or tan/blond tolex with white pipping.



#27
Definitely still interested! I've been following your progress, I just don't know enough about amp building to have significant comments.
#28
Quote by kurtlives91
We still interested?
Not so much. Christmas came and went and you hadn't finished this and put it under my Christmas tree, so fuck off, you selfish bastard.

srsly, though, the traces on the PSU board look scary close. I can almost smell the ozone from here. I really hope they don't arc or smth.
Meadows
Quote by Jackal58
I release my inner liberal every morning when I take a shit.
Quote by SK8RDUDE411
I wont be like those jerks who dedicate their beliefs to logic and reaosn.
#29
That makes one of us worried about the traces!

If you wanted an amp you should have asked. I built four Matchless/Voxy amps since then, I could have slipped you one.
#30
Yesterday and today I populated the eyelet board. Later today I installed it in the amp and started wiring it up. So far I only wired the tube side.

Followed the wiring color as per the #2xx amp I am cloning. Same old style Dumble lead dress. Note the lengthened cathode wires and how the cathode and plate often run parallel.

Eyelet board is pretty standard stuff. Carbon film 1W resistors, military spec RN65's metal films for the plate's, Orange Drop 6PS for caps. Had to add one eyelet for the HRM OD entrance (props if you can spot it). One 4K7 resistor under the board for "padding" the OD trim pot. Still need to clean the board off a bit, damn 63/37 solder.





#31
looks awesome. why use an eyelet board instead of a copper clad pcb though? one last question, what ampere rating do you use for the toggles and such? like 6A @ 250v or more? maybe less? just curious as to which is a safe move with HV equipment
#32
Quote by kurtlives91
Had to add one eyelet for the HRM OD entrance (props if you can spot it).
This one?



Quote by blandguitar
why use an eyelet board instead of a copper clad pcb though?
Eyelets (or turrets) are fast, clean, and easy. Drill holes where needed, press eyelets in. Done. No patterning. No etching.
Meadows
Quote by Jackal58
I release my inner liberal every morning when I take a shit.
Quote by SK8RDUDE411
I wont be like those jerks who dedicate their beliefs to logic and reaosn.
#33
Quote by blandguitar
looks awesome. why use an eyelet board instead of a copper clad pcb though? one last question, what ampere rating do you use for the toggles and such? like 6A @ 250v or more? maybe less? just curious as to which is a safe move with HV equipment

As SYK mentioned the eyelet board is used cause it's cheap and easy to make. It is also way easier to remove and install components on an eyelet board than a PCB. Since all the signal path components are on the eyelet you want to be able to access them easily and efficiently.

The mini toggle switches are you see in the last set of pics are 125V at 5A. These switches are for signal use and switching applications. The most these switches see are 12V DC. I use Mountain switches for miniature toggle's as I think they are the best (a bit pricey though).

Power and Standby switches need to be more up to the task of high voltages and currents. I use Carling short bat switches in my builds. 6A switches. The take the switching voltage transients well.


Well spotted SYK! *e-props*
#34
I wish I had something more relevant to say other than 'looks cool,' but hey, it looks cool.
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Quote by handbanana
wiliscool is just plain dumb
#35
^Thanks!

Here are a few more progress picks. Wired up the relay boards (for the most part), wired in the mini toggle switches (almost), drilled and worked on voltage doubler and rectifier/bias PCBs, did a bit of wiring to the output tubes.












Cut the back panel and oval for the 212 cab as well.
#36
Looks great man.
Just call me Bobby
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#39
Thanks


200mF too much for the filtering for the bias supply? The original amp had two 47mF caps in parallel for 100mF of filtering. Today I went out and couldn't find 47mF 100V axials, so I got two 100mF 100V axials. Would two 100mF in parallel be ok to have in the bias supply, I would think it would be ok.
#40
Quote by kurtlives91
200mF too much for the filtering for the bias supply?
I don't see a downside here, Chris. You have a fairly large resistor in series, so there won't be a problem with surge during start up or anything like that.

Larger caps tend to have internal inductance, so I'd probably parallel a 0.1 with this.
But I'd do that with a pair of 47uFs anyway.
Meadows
Quote by Jackal58
I release my inner liberal every morning when I take a shit.
Quote by SK8RDUDE411
I wont be like those jerks who dedicate their beliefs to logic and reaosn.
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