Dumble Serial number 006X OD50WX

[Charlie Wilson]

I'm with you Phil but here is were I'm coming from. I would ask anyone to put a Koa Speer 1/2w carbon film, Xicon carbon 1/2w carbon film, or a Piher 1/2W carbon film of the same (measured) value on say the input grid of the first tube and tell me that you can't hear a difference. We have at least five senses but the engineer science crowd wants to always differ to the visual one. Show me a graph or a audio spectrum read out. We have a very sensitive measuring device on both sides of our head and to me is the most important when we are talking about reproducing sound. Then if you can hear the difference, you are told by the so called educated elite that you are delusional because the fancy school that they paid tons of money to go to says that all components of the same value sound the same. It's absolutely insane. There is a saying in a certain crowd that I hang out with; contempt prior to investigation. You want your amp to sound good, then listen to what it actually sounds like. As far as goop, I think it serves multiple purposes but really I think Dumble was making a statement, "Stay out of my amp!". He started doing it right after his amp was copied and became Kittyhawk amps and frankly I don't blame him. He trusted those guys to sell his amps and they stole his design.
CW

[martin manning]

I would ask anyone to put a Koa Speer 1/2w carbon film, Xicon carbon 1/2w carbon film, or a Piher 1/2W carbon film of the same (measured) value on say the input grid of the first tube and tell me that you can't hear a difference.

Ok, a specific example! V1 input grid is a sensitive spot for sure. What kind of difference do you hear? I would guess it’s in the noise level?

[pompeiisneaks]

I'm with you Phil but here is were I'm coming from. I would ask anyone to put a Koa Speer 1/2w carbon film, Xicon carbon 1/2w carbon film, or a Piher 1/2W carbon film of the same (measured) value on say the input grid of the first tube and tell me that you can't hear a difference. We have at least five senses but the engineer science crowd wants to always differ to the visual one. Show me a graph or a audio spectrum read out. We have a very sensitive measuring device on both sides of our head and to me is the most important when we are talking about reproducing sound. Then if you can hear the difference, you are told by the so called educated elite that you are delusional because the fancy school that they paid tons of money to go to says that all components of the same value sound the same. It's absolutely insane. There is a saying in a certain crowd that I hang out with; contempt prior to investigation. You want your amp to sound good, then listen to what it actually sounds like. As far as goop, I think it serves multiple purposes but really I think Dumble was making a statement, "Stay out of my amp!". He started doing it right after his amp was copied and became Kittyhawk amps and frankly I don't blame him. He trusted those guys to sell his amps and they stole his design.
CW

The problem, though is that you could have someone else sitting with you that would clearly disagree and say they are 100% sure they hear no difference. They may have worse hearing, but since it's a human organ that is fallible, and a human brain behind it that also is prone to cognitive bias, you have infinite variability on that 'measurement' device.

that's not to say that you're not right, just that your right may not be for someone else

Also, testing something like that becomes pretty difficult, because you have to setup a test rig/jig that removes all other variables. I.e. the exact same tube, tube socket, wires, wire lead lengths etc. and doesn't impart 'flavor' from those sources also changing. This becomes pretty tricky. Not impossible, but tricky. Just the fact of desoldering one component, and soldering in another with differing solder amounts, heat applied, etc impacts how the component may have been impacted in installation.

see millions of variables.

I firmly think that the debate can't be solved, but you should just listen for what makes you happy and don't worry about what anyone else thinks

~Phil

[donvan]

Also, testing something like that becomes pretty difficult, because you have to setup a test rig/jig that removes all other variables. I.e. the exact same tube, tube socket, wires, wire lead lengths etc. and doesn't impart 'flavor' from those sources also changing. This becomes pretty tricky. Not impossible, but tricky. Just the fact of desoldering one component, and soldering in another with differing solder amounts, heat applied, etc impacts how the component may have been impacted in installation.

I agree that it is difficult testing some of these things but I don't think it would be that difficult testing a V1 input grid resister. Just wire the two different type resisters (of the same value) to a switch and do a blind A/B test.

[Charlie Wilson]

I guess what is uncomfortable about this for some people is that some of it does become subjective. However, take a couple people that are really into tasting coffee or wine, they seem to come up with similar descriptions when describing the taste. To me Koa Speer 1/2w carbon film resistors sound dull and boxy, Xicon 1/2w carbon film have more top end but are grity sounding wih tight mids(or scooped), and Piher resistors are bright(articulate) on the top end not as scooped in the mids and bit more bassy than the previous two. These are subjective descriptions but I know however you describe them they sound different and as timbre is determined by the harmonics, a complex signal and frequency analyzer would show a difference. I just don't have one of those. Look I find the tech stuff interesting and useful and should learn more but I also trust what I hear and ultimately when I strap on a guitar that is the most important thing. As far as noise level with a grid resistor, as there is no constant current going across it I don't know how different resistors of the same value would change the noise level.
CW

[martin manning]

To me Koa Speer 1/2w carbon film resistors sound dull and boxy, Xicon 1/2w carbon film have more top end but are grity sounding wih tight mids(or scooped), and Piher resistors are bright(articulate) on the top end not as scooped in the mids and bit more bassy than the previous two. These are subjective descriptions but I know however you describe them they sound different and as timbre is determined by the harmonics, a complex signal and frequency analyzer would show a difference.

Yes, but resistors are non-reactive (except for negligible-at-audio-frequencies lead inductance and capacitance) I don't know how they could . I've measured various types of same-value resistors with an LCR meter and they do not differ in any significant way.

As far as noise level with a grid resistor, as there is no constant current going across it I don't know how different resistors of the same value would change the noise level.

I was thinking thermal noise, which does not depend upon current, but in reviwing that I see it does not depend upon the resistor type either. There is grid current, but of course that is very small.

[talbany]

Charlie
I don't think anyone here (Including me) is telling you your imagining thing's( way to take this personally)


Like I said in my post "Some" people refuse or simply cannot? For whatever reason. How do I know this?.Years of working with the public.
So with that said How many here taking the position that it makes no difference in sound have actually done any extensive testing on the different types of parts to see if they hear anything or are you just looking at the spec sheets. Be honest!.
Btw. Yes there is no shot noise in grid resistors
Tony

[martin manning]

Still looking to get some of these special parts to do some A-B testing ;^)

[talbany]

Still looking to get some of these special parts to do some A-B testing ;^)

Check your mailbox they may be there. They went out tues "Special"

[Charlie Wilson]

Charlie
I don't think anyone here (Including me) is telling you your imagining thing's( way to take this personally)


Like I said in my post "Some" people refuse or simply cannot? For whatever reason. How do I know this?.Years of working with the public.
So with that said How many here taking the position that it makes no difference in sound have actually done any extensive testing on the different types of parts to see if they hear anything or are you just looking at the spec sheets. Be honest!.
Btw. Yes there is no shot noise in grid resistors
Tony

Tony, your are right I get a little worked up sometimes. I supposed everyone has different aspects of this amp building that they enjoy and I am envious of the guys that know all the formulas and technical stuff. However, the thing I find the most fun is strapping on a guitar at my bench with a bunch of different components and seeing what I can get an amp to sound like. I truly believe that some of the overly bright or harsh or not lively enough amp issues could be solved or at least made better through component choices. I believe that Dumble was very deliberate about what he used and where from a sonic standpoint. I can accept that if someone has tried some different components and does not hear a difference way better than if someone refuses to try because in theory they should all sound the same. In the immortal words of Lord Valve; "This ain't f...ing rocket science they'e audio circuits!".

[martin manning]

Still looking to get some of these special parts to do some A-B testing ;^)

Check your mailbox they may be there. They went out tues "Special"

Nothing yet, but I'll keep looking.

[talbany]

Still looking to get some of these special parts to do some A-B testing ;^)

Check your mailbox they may be there. They went out tues "Special"

Nothing yet, but I'll keep looking.

keep me posted

[talbany]

Charlie
I don't think anyone here (Including me) is telling you your imagining thing's( way to take this personally)


Like I said in my post "Some" people refuse or simply cannot? For whatever reason. How do I know this?.Years of working with the public.
So with that said How many here taking the position that it makes no difference in sound have actually done any extensive testing on the different types of parts to see if they hear anything or are you just looking at the spec sheets. Be honest!.
Btw. Yes there is no shot noise in grid resistors
Tony

Tony, your are right I get a little worked up sometimes. I supposed everyone has different aspects of this amp building that they enjoy and I am envious of the guys that know all the formulas and technical stuff. However, the thing I find the most fun is strapping on a guitar at my bench with a bunch of different components and seeing what I can get an amp to sound like. I truly believe that some of the overly bright or harsh or not lively enough amp issues could be solved or at least made better through component choices. I believe that Dumble was very deliberate about what he used and where from a sonic standpoint. I can accept that if someone has tried some different components and does not hear a difference way better than if someone refuses to try because in theory they should all sound the same. In the immortal words of Lord Valve; "This ain't f...ing rocket science they'e audio circuits!".

Charlie
Were cool!. I am more in your lane as well. Never that great at the math either. My partner at VVT Amps designs underwater weapons systems for submarines (Yes a Rocket scientist ) so he kind of used me for my ears and I could play guitar. He was my mentor and learned plenty from him. He was also a TV repairman in the 60's and 70's and worked on High powered radio transmitters that were tube driven. How cool is that want to talk about High Voltage and high heat! . Back when we started the company I too would sit in the shop for hours after everyone was gone and try all kinds of different parts searching for that perfect sound. Now I don't know that I found it (maybe for me) but all those hours of trying different parts definitely helped me to better design custom amps for certain players (which I did for many great players) I've found certain players just prefer the sound of a ceramic cap over a mica or the Great Tom Principato who DID NOT like the sound of MF's on his plates . Some players prefer the sound of Mallory 150s or NTE's over the PS's'. So this is just another example of yes! the "Players can tell" the difference but it was my job to figure out which parts better suited what it was they were hearing. So all those hours tweaking finally paid off. Sort of. This was kind of the point I was making in my other post but probably did a bad job of explaining it
BTW. I personally like that certain parts carry with them a certain sound. It makes building that much more interesting and personal to the player and am constantly discovering the sounds of new parts from guy's like you!

I am Done! talking about this.
Tony

[FUCHSAUDIO]

if it's covered with silicone then there'l be no vibration of components ....subtle tone choices......

how do you fix stuff if it's gooped?
M

Well, it's funny you ask. My friend Paul in LA, a good friend of mine owned a Dumble. One of the early "bought it for a grand, flipped it for 3 grand and today it's at Carter's for 100-K" guys..lol. He owns 4 or 5 of my amps and honestly felt the Dumble was a good amp but feels mine are great/better/whatever. Whatever...

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...

I don't disagree that he used parts that (at the time) were unheard of in guitar amps. Randy Smith at Mesa actually used some RN resistors in the early Boogie MK-1's. I don't know if he got them because they were quieter, tighter tolerance, sounded better, or he saw what Dumble did. As mentioned earlier, some of the early amps I made with audiophile caps and Holco resistors and RN series resistors were pretty tits...sadly, those parts not being RoHs or available kinda sucks...The PRC resistors (made in the states these days) are very good, although costly..

Thanks for the kind words. I'm not here often, I'm pretty involved with the business and whatever spare time I do have is spent with the family or playing gigs while I still can.

[martin manning]

...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..

Thanks Andy. Just to be clear, he removed the silicone, and left the parts and board intact? I'd guess to avoid damaging what's underneath a burr cutter would be best, as opposed to a cut-off saw.