Mid Plate iterations and asymmetrical Rp/Rk ratios

[FuzzFaceBuilder]

I've been working up a first-generation build for a while now, And in research I've found interesting Rp/Rk iterations. Some HAD built, some by others.

So, two questions:

For all the guys that have been in actual ODS have you come across any mid-plate iterations (i.e. 150k/180k or 135k/135k etc.) that sound good/work well when implemented in an early generation ODS? Are there personal preferences, non HAD implemented, that work well?

Secondly, asymmetrical Rp/Rk ratios(!) I've been reading that changing the ratio changes the bottom half of a scoped wave form. HAD implemented non-1/66 ratios on purpose in ODSR #60 and ODS #20.

The asymmetrical plate/cathode resistors (180K/1K and 130K/1.8K) make a big difference in the sound. Ask Dogears about ODS #20...

And 67plexi's asymmetrical mid-plate iteration

...The next one is a 50 Watt started out as a #183 but it distorted to much so I went with the 135k,2k2/135k,2k2 on V-1... I may have stumbled on Angles breath with this build...when I switched to the 1950 Broadcaster The people just swarmed the stage...It's not 3D it's 4D...

Are there other "golden" ratios (i.e. 1/61.3, 1/72.2, 1/Rp) that work well in Rp/Rk situations?

Here's to hoping!

[talbany]

Personally I don't think the focus here should be placed on clipping patterns alone (symmetrical vs asymmetrical):shock:
I think the emphasis should be more on frequency response (tone) and feel (although how do you quantify feel )
We know we hear the difference in high plate vs low plates
IMO..It's a 2 part question?
How the clipping symmetry effects quality of breakup (in OD)
How it effects tone?
Then ask are all 4 stages set up symmetrically?

Something to think about..
I think he was more concerned with frequency responce and feel than clipping patterns..But that's a guess!!

There are no golden ratios..Well maybe for you!!

Happy Thanksgiving!

Tony

[dave g]

There is only one stage in the dumble that clips significantly during normal operation, and that is the 4th (aka OD2 or V2b)

The symmetry of that stage's clipping is probably the single biggest determiner of the sound of the overdrive, and you can control it to a huge extent with the cathode resistance.

You should try wiring up a 10k linear trim pot as a variable resistor and using it as the cathode resistor for that stage. Put an extra 500 ohm resistor in series just to establish a lower limit. Try the trimmer at a bunch of different settings and let your ears be the judge.

Read this:
http://www.valvewizard.co.uk/Common_Gain_Stage.pdf

[Structo]

I remember Dogears (Scott Lerner) saying that the ratio of around 1/66 was one of the crucial things for the Dumble tone.

[FuzzFaceBuilder]

Tony Dave and Tom,

Thanks for sharing and informing my perspective.

I agree that symmetrical/asymmetrical clipping isn't the goal. I'm curious about implementation of non-1/66 Rp/Rk networks in the whole of the circuit as frequency response, tone, etc. go.

Happy Thanksgiving and thanks so much.

Hale

[talbany]

Tony,

Thanks for sharing and informing my perspective.

I agree that symmetrical/asymmetrical clipping isn't the goal. I'm curious about implementation of non-1/66 Rp/Rk networks in the whole of the circuit as frequency response, tone, etc. go.

Happy Thanksgiving and thanks so much.

Hale

Cool!!..Not sure if it helped but your welcome..
FWIW..I have a theory that relates to this..

Most of our most popular/longer lasting amp designs (amps we grew up with and are used too) Most use 100k plates (but with slight variations on cathode's).
I believe these stages have basically gone unchanged and have stood the test of time for 2 reasons ..They sound good and they work with many different types of instrument/Guitars..Both Buckers and singles sound good in a 2/3 gain stage amp w/100k plates
When you start to deviate from this type of gain stage your narrowing that field and heading in a more specific direction in sound or feel so you might end up with a design that might sound great with certain instruments and not so good with others.. Something to keep in mind when going down this road..
BTW This is not just related to Dumbles topology but other designs as well..
Have a goal in mind or chase your tail!!

DO a search as I remember years ago some great posts discussing how RP/RK values effect tone..If I get time I'll look!!

Tony

[marcos]

I have seen at least one ODS similar to #60,
AFAIR 180k/1k and 130k/2,2k on V1a and V1b.
From what I have heard this was arrived at by experimentation,
in order to satisfy the owners tastes. To me, this underlines what Tony has said in his statement, i.e. straying from the 66:1 ratio
may work for a certain player/ guitar/ musical style, but your on the safe side with the traditional values. This what my experiments have
taught me, as well.Just my 2 Euro cents (.027 USD)

Marcos

[67plexi]

Marcos, So true I look at #60 ODSR as a test amp V-1 100k/130k white Mepco/Electra
When I built a copy of #60 it had a dual sound for slide guitar it was great. A slight delay V-1a/V-1b.
As far as I know I am the first to use 135k 2k2 / 135k 2k2 on V-1 to each his own.
I want to sound like me not them. I'm a Drummer what do I know ???
I get stuck playing guitar in bands.

Steve.