why the higher plate loads on Dumbles?

[martin manning]

The larger plate resistors (which sets the rails) generating a greater voltage drop across the resistor giving you a wider voltage swing in effect offering greater headroom...

A larger plate load will increase the plate voltage swing for a given grid voltage swing, and so produce more gain. I would argue that headroom, which is defined as the maximum grid voltage swing at the onset of clipping, is unaffected as long as the center bias is maintained. Along the load line, clipping occurs at Vg-k=0 and the Vg-k where the load line crosses Ip=0, which is fixed by B+. So, it's really B+ that determines headroom.

[thyx]

The larger plate resistors (which sets the rails) generating a greater voltage drop across the resistor giving you a wider voltage swing in effect offering greater headroom...

A larger plate load will increase the plate voltage swing for a given grid voltage swing, and so produce more gain. I would argue that headroom, which is defined as the maximum grid voltage swing at the onset of clipping, is unaffected as long as the center bias is maintained. Along the load line, clipping occurs at Vg-k=0 and the Vg-k where the load line crosses Ip=0, which is fixed by B+. So, it's really B+ that determines headroom.

This.

[talbany]

Martin
Thanks for the clarification..Senior moment



Tony

[martin manning]

It's all good... I was thinking that this had been discussed before: https://tubeamparchive.com/viewtopic.ph ... 7&start=30 It wasn't easy to find, and I knew what I was looking for!

[Max]

Hi,

This is what I remember and think:

Concerning "history":

ODS amps with "pre-classic" specs (#001 > around #70):

I don’t know of a single ODS, that seemed to have been originally built with "pre-classic" specs, with plate resistor values higher than 100K.

ODS amps with "classic" specs (around #70 > around #140/150):

AFAIR you’ll find "classic" amps with 100K plate resistors and "classic" amps with higher plate resistor values in the same series number range. #124 as an example has 100K and #123 has higher plate resistor values. AFAIR both have been built around 1984.

AFAIR you’ll find even "classic" amps with some "high plate" variant for V1 but a "low plate" configuration for V2.

ODS amps with skyline, bluesmaster etc. "post-classic" specs (starting around #140/150):

AFAIR these all have plate resistor values higher than 100K and often with "individual" plate resistor values different from amp to amp.

Late eighties and later updates of "classic" and "pre-classic" amps:

In updated amps AFAIR you'll find all kind of configuartions. Some with "low-plate" specs for V1 and V2, some with "high-plate" specs for V1 and V2, some with "high-plate" specs for V1 and "low-plate" specs for V2.

Did DA use a Dumble amp?:

Up to know I didn't find some IMO trustworthy source for a confirmation of this rumour. If someone here knows of such a source this would be interesting of course.

Concerning tone:

As you know, there is this "reference thread": https://tubeamparchive.com/viewtopic.ph ... 483#136483.
So IMO it would perhaps make some sense to explain the differences in tone you talk about (more or less "violin-like" as an example) by referring to examples from this thread.

Why?

IMO "violin-like" as an example could perhaps be used in a rather different sense by different people. So perhaps you could use some of the Charly Bonat or Karl Ratzer "non-slide" tracks recorded with "pre-classic" ODS amps to compare these with the tone of some "skyline" or "bluesmaster" non-slide tracks?

Relation between a certain kind of tone and a certain kind of technical spec:

I personally have a lot of difficulties to understand why people who obviously have a lot of knowledge concerning the general physics of a tube amp don’t simply bring some amps with some of these different technical specs to some sound research laboratory and simply measure the differences present - as an example in the timbre structure of these different amps - instead of only discussing in a more speculative manner what perhaps could be the more important differences in the sound emission of a "low-plate" and a "high-plate" amp?

IMO it would perhaps be rather interesting to find out in an experimental methodical and scientific way what differences in measurable sound emission can be found to be in a significant relationship to certain technical specs, and after this is done, if there are similar significant relationships between the meaurable sound emission parameters and the perception of musicians and/or audiences when playing and/or listening.

In this thread https://tubeamparchive.com/viewtopic.ph ... 133#150133 some members like Luddy and Cliff Schecht have gratefully offered their help if you shouldn’t know such a kind of sound research laboratory and how to use it to find out meaningful relations between the technical specs and the sound emission of amps with different technical specs in a scientific way.

A Google search like "sound research laboratory" etc. would of course be another obvious way to make a first step into this direction.

A nice weekend to all here!

Max

[Structo]

I wonder how disjointed the serial numbers and how far out of sequence they are?

For example, somebody orders an amp, say it's going to be #157.

Something happens and for some reason #157 get's put on the shelf for a year or more.

Now a year or more later he comes back to that amp and incorporates all the updates up to that point in time into that amp. (Skyline, Mid Boost, Precision Power Supply, etc.)

So is it still feasible to say that such and such amplifier is 3d or 4th generation because of it's serial number?
Especially if we are not allowed to look inside?

[Max]

I wonder how disjointed the serial numbers and how far out of sequence they are?

Hi Tom,

IMO based on what I know this is very similar with Dumble amps as with vintage guitars. A large percentage (75%?) of those vintage guitars that are still "all original" is "as in the books", some (15%?) will be different in certain specs, few (8%?) will be different in more specs, very few (2%?) will be even rather "strange".

So is it still feasible to say that such and such amplifier is 3d or 4th generation because of it's serial number?
Especially if we are not allowed to look inside?

"Generation" as I use this term first of all refers to a common look that is the same for a certain generation.

But indeed: Many or even most of the amps from the same "generation" (= "look") I know have some similar technical specs, like the "pre-classic" OD entrance structure as an example or the "classic" tone stack values as an other example etc.

But of course you'll find differences in the details of a general structure as with all general structures. Again: very similar as with vintage guitars (just ask the Gibson Custom Shop concerning the "correct" neck angle of a vintage '59 Burst). The more this will IMO be the case with custom made amps.

SO IMO you should look upon this "generation" term as referring to amps with the same look and a Gaussian distribution of specs around those values that are the most common ones for a certain generation. Do you understand what I'm talking about?

All the best

Max

[Structo]

Yeah, Gaussian.

[greiswig]

So...aside from me, how many people here have and use a low-plate amp? How many have even tried one? IIRC, Gil had and liked one...but I don't know as I've heard anybody else saying they used one.

[David Root]

I built two, a #124 100W and a #13/#40 '70s 50W. I like the 124 in OD with both PAB and MB, awesome, once I got rid of a nasty parasitic, which took quite a while. The '70s is just so nice in OD , has neither PAB nor MB, old school aggressive tone that takes me all the way back!

I also built a high plates Bluesmaster 4x6L6GA w/HRM and PAB, also a super rockmeister! Good with 5881s too.

All sound great clean as well.

Low plates, high plates, HRM, non-HRM, standard PI, Bluesmaster PI, 6L6, EL34, Music Man 700V plates, they all have their place I think. But not every permutation sounds great apparently, I guess I have just been lucky so far.

[Max]

So...aside from me, how many people here have and use a low-plate amp? How many have even tried one? IIRC, Gil had and liked one...but I don't know as I've heard anybody else saying they used one.

Hi greiswig,

The Dumble ODS 100W amp I liked best up to now is a 100W "classic" ODS with 100K for V1 and V2. This is what I liked:

- OD sound is sparkly and shining but full and fat, too, with single coils and buckers, but still very "clean" and "polished". The OD hamonics are not audiable as some "fuzz" or "fizz" that seems to be a bit seperated from the non-generated harmonics. In perception the OD generated harmonics start without a gap where the non-generated "end", no break between these two. So the generated harmonics don't sound generated for my ears.

- Overall OD sound is already a bit more "stylish" and "designed" than the sound of a "pre-classic" ODS, but in a (for my ears) still very "natural" sounding way that I personally like a bit better than the sound of at least some of the later skyline etc. amps that are too much "Dumble sound synthezised" for my personal taste.

- I don't look for a "Dumble tone" in a Dumble amp but I use a Dumble amp just because these are well made musical instruments and able to deliver the tones I hear in my head. And I want that my guitar still sounds like an electric guitar and not too much like a horn or a violin or a keyboard etc.. The more SSS-DNA I can perceive in an ODS the better I usually like it. The sustain I am looking for in OD mode with a strat as an example shall be more of the kind of a great fat sustainy slide tone without playing slide than emulating a sax etc. This "low plate classic" amp in my perception does all this in perfection.

- The OD tone of this amp is SRV realm with ease, if you dial it in to do a SRV kind of sound. And I like the SRV kind of tone a lot because it is that "electric". And I like it if an electric guitar sounds "electric" and not too much like a woodwind.

- Clean sound is very versatile for chords and single notes in very different timbres and from cristal clear to sustainy blues single note playing.

- OD timbre is just an extension of the clean timbre, what I like.

What I like best about this amp is its versatility. I can do all musical styles I like from clean and warm Chet Atkins stuff or sparkling Andy Summers chords up to Peter Green, SRV, Albert King, Dickey Betts, Billy Gibbons and high gain shredding (FET!) stuff - all with one amp.

Yes, this "low plate classic" I like a lot. AFAIR its technical specs are more or less similar to this one: https://tubeamparchive.com/viewtopic.ph ... 262#140262

@ David Root:

Low plates, high plates, HRM, non-HRM, standard PI, Bluesmaster PI, 6L6, EL34, Music Man 700V plates, they all have their place I think. But not every permutation sounds great apparently.

Hi David,

My impression in regard to all the original amps I played is exactly the same: All have their place and all are great musical instruments built in order to be the perfect tool for some individual guitar player and his personal musical interests and playing style etc..

Have a great weekend and lots of fun!

Max

[bcook]

Bang on Max. I've tried many iterations and I always come back to the low plate classic. It's just a fun amp for me to play.

[exocet]

Out of interest, does the 100K Classic ODS spec that Max is inferring take Strat type guitars well?

I know that many say that the skyliner stack needs a 0.047 mid cap for Strats but even with the Mid boost engaged on my "high plate skyliner" the OD with my strat (Fralin Blues Specials) is not very good, very mushy and indistinct - no guts to it at all. My telecaster however sounds very good indeed. I'm considering making changes, initially just to tone stack but now I'm wondering whether to go the whole hog and change plates as well?

[ayan]

Out of interest, does the 100K Classic ODS spec that Max is inferring take Strat type guitars well?

I know that many say that the skyliner stack needs a 0.047 mid cap for Strats but even with the Mid boost engaged on my "high plate skyliner" the OD with my strat (Fralin Blues Specials) is not very good, very mushy and indistinct - no guts to it at all. My telecaster however sounds very good indeed. I'm considering making changes, initially just to tone stack but now I'm wondering whether to go the whole hog and change plates as well?

I think that the 100K plate amps are more Strat-friendly, regardless of tone stack. The tone seems to be a bit more pronounced in the higher mids, as opposed to perhaps lower mids with the high plate values. The overdrive seems smoother, and the sound is chimier with low plates.

As far as a Strat goess, generally speaking, if you want the quack positions (2 and 4) the Classic tone stack will work better than the Skyliner. If you use the Skyliner, turn the mids up and the bass down and you will be close. Positions 2 and 4 like the PAB quite a bit, IMHO. If you like a fat bridge pickup sound, a la Eric Johnson, the Skyliner EQ will work better. Try Robber Ford settings, with the bass and midrange turned up, and you can get a pretty fat sound that way. PAB will thin things out, as discussed at length here.

HOWEVER, Strat pickupus all sound different. Until I got a HR 62 Reissue STrat a year ago, I didn't know that the pickups on that guitar could sound so good. They are low output, RPRW for the middle pickup, and they sound great through my amps. They are not capable of getting a harsh sound, and are much more pleasant to the ears than some Kinmans that I had in another Strart. At present, I ditched the Kinmans and have the other guitar (an EC Strat) back to its stock configuration with the Vintage Noiseless set and the mid boost. It doesn't sound much like a Strat, but then again, neither did the Kinmans when compared to actual single coils.

Gil

[stelligan]

I absolutely don't know the technical science of it all, but must agree that to my ears lower plate amps and Stratocasters(with vintage pickups) are a better pairing. I love those newer generation Dumble amp types. My Stratocasters do not. I am not really sure why I have kept building them(I guess for fun and for friends). These amps can be very unforgiving with some guitars and playing styles. I have purchased 5 humbucker equipped guitars and 2 Telecasters since I started building the darn things.

Henry's Redplate amps have been a revelation for my Strats. Different mid cap voicing permutations and built in tube loops seem to be a recipe to make a Strat happy. I guess I should leave the building to you professionals and have a guitar sell off.......... I should really be back down to one guitar, one amp, and one woodshed.