New 183 build

[Stephen1966]

Many thanks J and Charlie... I found an interesting article by Mr R.G.Keen, 'The Secret Life of Pots' which goes into detail about the procedure you recommend.

http://www.geofex.com/article_folders/p ... tscret.htm

I'm tempted to try shaving the pots first with a blade to see if I can achieve the consistency required. And the BASS pot is the challenge. Otherwise the technique of paralleling resistors seems like a more reliable way to achieve the target resistances. If the latter proves more successful, I might go with CC resistors - an instinctive choice - but Allen Bradleys sound like a good choice to me.

I have to read and inwardly digest that article again, and also think about the taper I want to utilise. For the moment linear or audio taper are the principle types I think I need to consider.

Thanks for doing the maths on this - it's a good start.

[Stephen1966]

i have i have!

+1

[WhopperPlate]

I think your instincts stand to reason . Most potentiometers are CC.

[Stephen1966]

With caps it’s fun to try a sozo mustard with a orange drop for starts

The transformers arrived today but they sent the wrong chassis

Putting the schematic and orders together now and was wondering if you are talking about a complete replacement of all the 6PSs or if there are certain positions that respond more effectively in the circuit. What did you try?

[Edit: a +1 for Tube Town - they informed me today that they are sending out the correct replacement, free of charge, and I can keep the wrongly delivered chassis. Damn! It means I have to build another amp now ]

[WhopperPlate]

With caps it’s fun to try a sozo mustard with a orange drop for starts

The transformers arrived today but they sent the wrong chassis

Putting the schematic and orders together now and was wondering if you are talking about a complete replacement of all the 6PSs or if there are certain positions that respond more effectively in the circuit. What did you try?

Most of my experience with that experimentation comes from working on other circuits , but some places I have tried generally are the PI input coupling cap and off v1b.

You can try this with anything , ceramic + mica , MF + CF, polyester + polypropylene, imagination is the limit

Fwiw dumble isn’t particularly known for this behavior

Not something I ever thought of executing throughout an entire amplifier , more like just something to try when you are looking for ideas for fine tuning .

This is somewhat like combining different composition caps in the tone stack (which dumble did do often enough) . For instance, It’s popular to utilize a 715p or similar as the mid cap , or bass , keeping the others 6ps

[bepone]

I have started to use 715 and 716 in more positions, middle cap, after V1b, before PI, after PI to the output tubes.. Then in V2a also! So, mostly
Then if the amp is too present, i'm starting to return 6Ps here and there.. always is good to have all colections of 6P2, 715s, 716s, and Sozo for tweaking..

[Stephen1966]

I'm planning a 715 for the PI entrance. The photo of 183 seems to show a 715 here, along with the 715s after the PI. The NTEs are a problem in that they aren't in production anymore and the idea is to use only in production parts and that might be a deciding factor in the use of Allen Bradleys as well, though there still seems to be quite a few of them around. For the NTEs I am going to use instead, the DME. I recently used these entirely in the Dumbleator circuit and it is very transparent with the 250k send pot, and quiet as well. So it's mostly in the latter stages of the preamp where the consensus is that there are areas for tweaking - I'll start with the 6PSs and see how they sound.

I will have the schematic ready soon so you will be able to see what I am planning... Another aim I have is to put this amp together quickly. My previous build, the Skyliner, took almost two years of thinking and research through all the testing and tweaking as well. But it only takes about six weeks to assemble the amp altogether. I think I would go crazy if I had to spend another two years on a project. Thankfully, many of the lessons learned in that project don't need to be repeated and I got to test the ideas in a way that I now know, what works and what doesn't. The 183, is very similar to the 124 in the topology but there are some key differences and I expect this to be a different animal altogether. To get it fired up and working is the first objective then, the tweaking could be quick or it could take longer. I don't mind.

The biggest differences are the power scheme, the OT and the power tubes. High plates and all the other little adjustments of values still follow the Skyline and 124 topology so it's not entirely an unknown entity.

The one (and only) thing I came to regret with the Skyliner, was that I didn't fully test the transformers before they were installed. I am wondering, how you would test the transformers and measure them before installation? Do you have any procedures you think are worth sharing?

[jazzbass]

Hi everyone,

building various versions of the amplifiers designed by H. Dumble I used the Lay out of Ceriatone as a guide and the diagrams of TAlbany, which he kindly inserted on the discussions of TAG, as a reference for the actual values ​​of the components as detected by the observations of real Dumble amplifiers but I wonder if this approach is correct.

The components that are found on the market today have different characteristics from those that Dumble had chosen and even if passive components of the same type as those used by him are found on the market, a part of the project, also for a matter of costs, will obviously consist of components built in the last two / three years.

Maybe you could search and find all the amp components in the vintage market but the end result will cost a fool. Without thinking about speakers and capacitors.

What is your opinion about it, it is really worth trying to reconstruct the "sound" of the amplifiers as H. Dumble built them, assuming you can really establish which one it was since many clips are affected by used effects, ambience, other instruments that play together, type of box and speaker, microphone used for recording and its position, etc.

I had been thinking about these aspects for some time but the construction of a # 183 and its subsequent transformation into Bluesmaster and its subsequent manipulation to obtain a "believable" sound especially the OD convinced me that the study of the original is necessary. but then the result must be obtained by trial and error.

a hug, Franco

[talbany]

So we know we have several different types of cap compositions like Charlie mentions that yield different sonic results ie, Polyester Polyprop, Mica etc. Then there are the voltage ratings which can also influence the sound as well. If your looking to tweak both sides of the amp then the PI entrance is a good way to do it. 715/16. If you are looking for a overall brighter tighter sound. If you want to take it the opposite direction then a paper/Mylar 220P is a good choice and middle of the road stock being the 6PS's
As far as the tone stack goes? If you are looking to brighten the treble frequency's use a mica cap, if your looking to brighten the mid frequency's then use a 715/716 mid cap, (also don't forget cap orientation matters in both mid and PI entrance.) A 200P in the OD couplers is a great way to help smooth out the OD side, I generally throw one in feeding the 100k resistor (level pot), whatever floats your boat.



Tony

[jazzbass]

Hi Tony,

thanks for your precious synthesis, it is a great help for me to understand in which direction to go to "Tuning" an amp or to predict from the beginning how I want it to sound.
My question remains: how did the Dumble originals sound or really sound, without the tricks of recording studios or concerts, and if it is worth trying to reproduce that sound or just take a cue from them and then reinterpret the project as they did TwoRock, Bludotone, Fucks and other excellent builders.

A hug
Franco

[Stephen1966]

building various versions of the amplifiers designed by H. Dumble I used the Lay out of Ceriatone as a guide and the diagrams of TAlbany, which he kindly inserted on the discussions of TAG, as a reference for the actual values ​​of the components as detected by the observations of real Dumble amplifiers but I wonder if this approach is correct.
...
What is your opinion about it, it is really worth trying to reconstruct the "sound" of the amplifiers as H. Dumble built them, assuming you can really establish which one it was since many clips are affected by used effects, ambience, other instruments that play together, type of box and speaker, microphone used for recording and its position, etc.

Ah! It's the old Ship of Theseus problem. Can a reproduction actually be the thing it reproduces?

I've spent enough years of my life trying to get to the bottom of that one and the short answer is 'no,' but...

I don't believe it's a matter of being "correct" or "incorrect" - sourcing period correct parts is just another way to address the problem of fidelity to the original.

I find it easier to understand these amps holistically, as both objects and ideas. To attempt a faithful reinterpretation materially, but also (importantly) to reproduce the sound I imagine, know and love. With this project, I want to be able to show that we can have both and we don't need to break the internet, the bank or our minds to do it.

To paraphrase the great philosopher Tony: after all said and done, it all comes down to whether it floats your boat or not. You know it.

By the way... you might want to revise how you address Mr Andrew Fuchs. He is from New Jersey, you know

[Stephen1966]

Returning briefly to the subject of pots, I was halfway through building an Excel formula when I came across this post:

https://el34world.com/Forum/index.php?t ... #msg236653

The excel spreadsheet there is quick for calculating the parallel resistance required to achieve a target pot resistance. It also has a graph which shows the effect of the parallel resistance on the taper of the pot. Using a a parallel resistor on the CCW side of the pot with the wiper provides a log taper, using a parallel resistor on the CW side gives an anti-log taper. Using two parallel resistors on either side of the wiper allows for some interesting unconventional tapers to be developed. You have to enter values for two parallel resistors for this spreadsheet to work but you can get around it by making one of them, near infinite resistance.

[WhopperPlate]

Hi Tony,

thanks for your precious synthesis, it is a great help for me to understand in which direction to go to "Tuning" an amp or to predict from the beginning how I want it to sound.
My question remains: how did the Dumble originals sound or really sound, without the tricks of recording studios or concerts, and if it is worth trying to reproduce that sound or just take a cue from them and then reinterpret the project as they did TwoRock, Bludotone, Fucks and other excellent builders.

A hug
Franco

Franco

Like you have said , without breaking the bank and chasing unobtanium , essentially what’s available is reinterpretation.

It’s tantamount to violin builders looking for the wood Stradivarius used to reproduce the sound . Old growth Italian spruce isn’t an abundant resource to say the least.

What you do have though is a wealth of knowledge and verifiable techniques used by the masters , and a vast selection of modern parts, to creatively interpret Dumbles designs and develop one’s own unique voice …basically what Dumble did himself . Who was using all those “rare as hens teeth “ parts before him ? And as those parts became less available he didn’t stop building them , he changed sources for parts .

As other very knowledgeable members have already stated consistently , layout and lead dress are imperative to the search . Arguably most important. You can use the most common brand parts and make something spectacular with adherence to these principles alone . Brushing this aside is not advised .

It would be one thing if every dumble was a carbon copy of each other . Fortunately for the sake of my argument and the hopes of all aspiring amp builders , they weren’t . Dumble creatively assembled available parts to produce amplifiers that ideally would have accomplished his and the artist’s objectives.

This core philosophy of dumbles approach to amplifier building is more or less self evident in the historical documentation of his evolving work.

All of this note for note cover band juke box mentality is well and good for whoever’s boat that floats , but for those simply interested in developing their own sound
, and or helping others achieve theirs , then the obsession with mimicry becomes counter productive . That being said , if you want to mimic bust out another thousand

[Stephen1966]

So we know we have several different types of cap compositions like Charlie mentions that yield different sonic results ie, Polyester Polyprop, Mica etc. Then there are the voltage ratings which can also influence the sound as well. If your looking to tweak both sides of the amp then the PI entrance is a good way to do it. 715/16. If you are looking for a overall brighter tighter sound. If you want to take it the opposite direction then a paper/Mylar 220P is a good choice and middle of the road stock being the 6PS's
As far as the tone stack goes? If you are looking to brighten the treble frequency's use a mica cap, if your looking to brighten the mid frequency's then use a 715/716 mid cap, (also don't forget cap orientation matters in both mid and PI entrance.) A 200P in the OD couplers is a great way to help smooth out the OD side, I generally throw one in feeding the 100k resistor (level pot), whatever floats your boat.



Tony

Hi Tony, I would be keen to hear your ideas about cap orientation.

[WhopperPlate]

Safe to say almost everything being said here has already been said somewhere else in the forum already