ODS 124 - revisited for the 21C

[pompeiisneaks]

Glad I'm not the only one confused. Here it's defined as Bus Bar:


https://en.wikipedia.org/wiki/Busbar

~Phil

[Charlie Wilson]

One reason why they don't might be because there seems something frivolous or petty about hiding the circuits from techs who come after or about trying to hide something. There may be some truth to that with regard to Alexander. I know lots of human beings and artists who are, sad to say, quite flawed individuals but they still do brilliant things. But I don't buy it. D is too deliberate, too conscious of every small detail it seems, and I just don't buy it was the only reason he gooped his circuits. I have a theory, only a theory mind you, that the silicon is there, epecially in the more sensitive early stages of the amp as a means of thermal control. Silicon is a very poor conductor of heat. Those silicon hand mitts we use are no more than 1/16" thick but allow us to handle objects of hundreds of degrees coming from the oven. The inside of a chassis, with it's host of valves is a very hot environment and subject to extreme temperatures from a cold start up to fully opened up and operating.

I would like to comment on this. Not that Dumble needs me to defend him but you may think differently when I tell you when and possibly why he started gooping his amps. Dumble had worked out a deal with a European distributor. I think the chassis were sent over and installed in cabinets once they got there. At this time the amps were not gooped and I believe they were 70s type circuits. Well someone got the idea to simply take Dumble's circuit and make their own amps called Kitty Hawk. So yeah, I'd be a bit pissed off if someone I trusted to do business with stole my design. After that came the 4th gen. amps and I believe to try and keep it from happening again, he gooped them. Obviously Dumble knows that someone can simply remove the goop, but he was also making a statement, Stay out of my amps. Dumble is an artist as well as technician and artists don't like being literally copied so others can profit.
CW

[talbany]

Kitty Hawk

Kitty Hawk Clone.jpg

Original Dumble 2nd generation import #40..No goop

12 (1).jpg

BTW..Here is another #38 https://www.youtube.com/watch?v=b3CjSEq-Y1A&t=1066s

Dumble-#40-(1).jpg

Roy brothers´shop in Bochum, Germany,where Applied Acoustics built the 1X12 combos in the wood cabinets.

https://ampgarage.com/forum/viewtopic.php?f=4&t=34312

Tony

[marcos]

Between 1978 and 1981 I had several long phonecalls with Wolfram Roy of Applied Acoustics/Kitty Hawk, and also visited their shop a number of times. He basically said that he thought he could make something like the ODS a lot of cheaper, hence the Kitty Hawk "Standard", which must have been the first Dumble clone ever. Decent amp, darker sounding than the Dumbles of the time.
They were also making a copy of the Mesa/Boogie Mk II at the time, before moving on to other models. BTW, the price for the ODS was 2500 DM at the time, around 1500 USD, iirc. Glad I kept mine. Not that I´d ever sell it. My .02 cents Marcos

[martin manning]

I would like to comment on this. Not that Dumble needs me to defend him but you may think differently when I tell you when and possibly why he started gooping his amps...

Add to that the "Security Agreement" which customers were required to sign, stating that no one except HAD would service or inspect the internals of the product for the purpose of analyzing the circuit, or even to leave it vulnerable to such inspection.

[Stephen1966]

One reason why they don't might be because there seems something frivolous or petty about hiding the circuits from techs who come after or about trying to hide something. There may be some truth to that with regard to Alexander. I know lots of human beings and artists who are, sad to say, quite flawed individuals but they still do brilliant things. But I don't buy it. D is too deliberate, too conscious of every small detail it seems, and I just don't buy it was the only reason he gooped his circuits. I have a theory, only a theory mind you, that the silicon is there, epecially in the more sensitive early stages of the amp as a means of thermal control. Silicon is a very poor conductor of heat. Those silicon hand mitts we use are no more than 1/16" thick but allow us to handle objects of hundreds of degrees coming from the oven. The inside of a chassis, with it's host of valves is a very hot environment and subject to extreme temperatures from a cold start up to fully opened up and operating.

I would like to comment on this. Not that Dumble needs me to defend him but you may think differently when I tell you when and possibly why he started gooping his amps. Dumble had worked out a deal with a European distributor. I think the chassis were sent over and installed in cabinets once they got there. At this time the amps were not gooped and I believe they were 70s type circuits. Well someone got the idea to simply take Dumble's circuit and make their own amps called Kitty Hawk. So yeah, I'd be a bit pissed off if someone I trusted to do business with stole my design. After that came the 4th gen. amps and I believe to try and keep it from happening again, he gooped them. Obviously Dumble knows that someone can simply remove the goop, but he was also making a statement, Stay out of my amps. Dumble is an artist as well as technician and artists don't like being literally copied so others can profit.
CW

I have datasheets, photographic evidence and a bunch of theories which unfortunately, I have neither the experience or the knowledge to interpret on my own, to the extent I would want to. Is he an artist? No doubt. Would he be pissed? Deservedly so. [Edit: "Deservedly" is a poor choice of adverb. I have no axe to grind with Mr D. For anyone who cares, I meant to say: "Rightfully".] But beyond that, I'm not going to speculate any further about the character of the man. Do the historical events which led to this practice deserve further scrutiny? Yes. Nothing happens outside of some context. And so, in this present context, if encasing the first stages of the amp had such clear thermo-electromechanical advantages, why doesn't everyone do it? But then, can we really say, with absolute certainty, it has no effect. Passive heatsinks and thermal insulators are a thing. The effect might be negligible but what if, this very small thing contributes in some distinct way to the dynamic behavior of the amp across a range of operating and environmental conditions?

[Stephen1966]

I would like to comment on this. Not that Dumble needs me to defend him but you may think differently when I tell you when and possibly why he started gooping his amps...

Add to that the "Security Agreement" which customers were required to sign, stating that no one except HAD would service or inspect the internals of the product for the purpose of analyzing the circuit, or even to leave it vulnerable to such inspection.

Yes, it's clear he was concerned about his intellectual property. I stand by my theory that there are possibly more pragmatic reasons for why he did this. So far, nobody is actually standing up and saying it has nothing to do with the thermal signature of the amp.

[martin manning]

Relatively massive components standing on wire leads (Orange Drop caps, say) are subject to resonant vibration and fatigue failure of the leads. There could also be some audible effect when vibrating components are spaced closely enough for some coupling to occur. Applying a bit of silicone can prevent this movement, and you can see that HAD has done that in some instances. You don't see any silicone on the PI caps, though, so he wasn't concerned about mechanical failure there. Covering the preamp with it is unnecessary, and makes servicing the amp more difficult. I'm standing up and saying I believe it's for IP protection.

[Stephen1966]

Relatively massive components standing on wire leads (Orange Drop caps, say) are subject to resonant vibration and fatigue failure of the leads. There could also be some audible effect when vibrating components are spaced closely enough for some coupling to occur. Applying a bit of silicone can prevent this movement, and you can see that HAD has done that in some instances. Covering the whole preamp with it is unnecessary, though, and makes servicing the amp more difficult. I'm standing up and saying I believe it's for IP protection.

Thank you, I see your point... try as I might, I can't find a datasheet for the LCA 0411 Sprague Q-Line resistors so I can only guess what the temperature coefficient of these could have been. My guess, is that it was probably quite poor by today's standards. Perhaps there is a relationship between the PPM the W and the physical mass of the component. In my very limited experience, the greater the rating in W, the greater the physical size and so in my mind at least, the greater the thermal stability of the component. Smaller components, thinner leads and so on, suggest a smaller impedance and hence a higher susceptibility to ripple currents. A silicon encasement could therefore, take the small physical size out of the equation and provide a blanket of thermal protection from the other heat sources, thus improving the performance of the component. Maybe, I'm overthinking it, or just plain wrong. I would welcome being corrected on this. Likewise, there are quite a few caps in that area of the board, and for an airtight seal around the leads if nothing else, it possibly extends the life of the amplifier. Reliability was one of his stated goals I recall. Having seen the photos for myself though, there is no argument, he really did go to town with the silicon gun.

[talbany]

Relatively massive components standing on wire leads (Orange Drop caps, say) are subject to resonant vibration and fatigue failure of the leads. There could also be some audible effect when vibrating components are spaced closely enough for some coupling to occur. Applying a bit of silicone can prevent this movement, and you can see that HAD has done that in some instances. Covering the whole preamp with it is unnecessary, though, and makes servicing the amp more difficult. I'm standing up and saying I believe it's for IP protection.

I completely agree!
As an amp manufacturer I would want to be able to have access to most of my preamp without having to spend several hours scraping goop from the thing.Especially in Dumbles case, being a custom amp designer to be able to go in and quickly modify or repair something or in the case of 124 upgraded from a Low plate classic to a Skyliner you would want that flexibility and there would be a good reason for gooping the entire thing..A dab of silicone can always be applied to the board to secure leads secure caps and prevent vibration, moisture from entering the cap through the lead extensions is recommended but not the whole thing.. Given the Precision resistors Dumble used in key spots and Flameproof Q-lines I would think under normal operating conditions heat would not be a big factor.

(For those that are interested? he uses what's called Permatex high dielectric RTV. For grins I gooped one similar to how Dumble does his.There was a slight shift in tone I would say would be similar to going from a maple neck guitar to a Rosewood was kind of what it reminded me of.This was back when I was really into Dumble amps )


BTW.My theory is that he was not only protecting the design but also what type of parts he used like Precision metal films on plates,cathodes..imo is a rather large part of the Dumble sound..Because anyone with a meter and cap tester and a little knowledge of guitar amp design can determine RP/RK values along with a few cap values where it's gooped.Again it's just my theory
Tony

[ChopSauce]

Yes.

I don't understand how the goop would be of any help with regard to thermal considerations. Convection (that is goop-free) is way more efficient at transporting heat away from components, even though metal do a great job at conducting heat. So once gooped, components have almost no efficient way of dissipating their heat. The goop being seemlingly a thermal insulator, the situation seems even worse.

If that were to protect from vibrations, no need to goop above components, either.

Maybe HAD considered it was better replacing the whole board. His customers where worth it ...

[didit]

Relatively massive components standing on wire leads (Orange Drop caps, say) are subject to resonant vibration and fatigue failure of the leads. There could also be some audible effect when vibrating components are spaced closely enough for some coupling to occur. Applying a bit of silicone can prevent this movement, and you can see that HAD has done that in some instances. Covering the whole preamp with it is unnecessary, though, and makes servicing the amp more difficult. I'm standing up and saying I believe it's for IP protection.

I completely agree!
As an amp manufacturer I would want to be able to have access to most of my preamp without having to spend several hours scraping goop from the thing.Especially in Dumbles case, being a custom amp designer to be able to go in and quickly modify or repair something or in the case of 124 upgraded from a Low plate classic to a Skyliner you would want that flexibility and there would be a good reason for gooping the entire thing..A dab of silicone can always be applied to the board to secure leads secure caps and prevent vibration, moisture from entering the cap through the lead extensions is recommended but not the whole thing.. Given the Precision resistors Dumble used in key spots and Flameproof Q-lines I would think under normal operating conditions heat would not be a big factor.

(For those that are interested? he uses what's called Permatex high dielectric RTV. For grins I gooped one similar to how Dumble does his.There was a slight shift in tone I would say would be similar to going from a maple neck guitar to a Rosewood was kind of what it reminded me of.This was back when I was really into Dumble amps )


BTW.My theory is that he was not only protecting the design but also what type of parts he used like Precision metal films on plates,cathodes..imo is a rather large part of the Dumble sound..Because anyone with a meter and cap tester and a little knowledge of guitar amp design can determine RP/RK values along with a few cap values where it's gooped.Again it's just my theory
Tony

Full agreement and standing beside you both.

Best .. Ian

[Charlie Wilson]

Someone once said that Dumble would just cut off the goop components and all, and reinstall, if he had to fix something. I was incorrect about the wattage rating of the LCA0411, they are .55w.http://pdf.datasheetcatalog.com/datashe ... 8260_1.pdf. The other thing about the goop, I'm pretty sure that if he saw signs of the goop being removed you would not get your amp serviced ever again by him.
CW

[talbany]

Someone once said that Dumble would just cut off the goop components and all, and reinstall, if he had to fix something. I was incorrect about the wattage rating of the LCA0411, they are .55w.http://pdf.datasheetcatalog.com/datashe ... 8260_1.pdf. The other thing about the goop, I'm pretty sure that if he saw signs of the goop being removed you would not get your amp serviced ever again by him.
CW

It was Andy Fuchs

So, he had his Dumble develop a noise issue. He's a handy guy and opened it up but when he saw the goop, he decided to just take it to the man. He described the abode (I believe that weird church-like building on Jackson Brown's property). He said he walked down a hall to his shop room, both sides of which were filled with stacks and stacks of old Fender amp chassis. Some missing power transformers, some missing output transformers, some missing parts here or there...from which Dumble selected "exceptional examples of the parts he required for his designs". My friend hands him the amp and he proceeds to take a Dremel with a cutter wheel on it, and basically chop the goop right off on the preamp end of the board !! Tossed it in the garbage, rewired the preamp, tested and regooped it...

https://ampgarage.com/forum/viewtopic.p ... op#p398287

Tony

[Charlie Wilson]

Tony, in a totally unrelated, derail, I think that amp the Russian guy in the video is playing through sounds great! Check out the two added resistors in the OD section that are in the gut shot in the video. Any ideas what those do? They go from the OD out to the two leads of the bypass caps or maybe parallel the cathode resistors to make the OD a bit gainier?
CW