First D Style Build Advice Needed

[thesmokingwings]

Good Morning Group,

This is my first post in the Dumble discussion section after many, many hours of reading. My main observation so far is a Dumble build is very hard to compare to an original unless you have the availability to play the original, due to the feel as much as the sound, that can't be properly transferred through sound clips and videos. While you can study the circuit and come as close as possible to a clone of it, you can't really know how close it is unless you can play or hear in person what you are cloning. Therefore, since I don't have or may never have access to an original, I need to BUILD something in order to get a base from which to have a starting point. I have many guitars that I can play, so the need to build an amp to a guitar specifically isn't important at this point, and I also play multiple genres, so building for a particular style isn't necessary either. I'd much prefer to build a standard circuit and tweak as/if needed. There are a few particular things I think I would prefer in the build that a certain circuit might be more proper, and that is probably the direction I'd like to take the build, however...

The most important part of this first build is to learn the style of build and to secondly use what I have on hand. I have a few dozen builds under my belt so far, mostly 18 watt and under, as that was the iron I had available in the most quantity and with the least amount of necessity to buy more parts (mostly organ chassis/iron as I got into building amps by repairing Hammond organs, and through that I also fell in love with tubes, of which I now have a few thousand that are usable). I've gone through most of that iron now, and am at the point where I have larger iron that needs to be used. Also, as you can see in the attachments, I have purchased 18 chassis that were closeouts from Carol Ann OD2 stock at Mojotone. At the price I paid, I couldn't worry about whether it would fit a build I had in mind or if the iron would be perfect for the spacing, as I can't build a chassis for what I paid, plus theyre powder coated! So I bought them with the intent of building D style amps with tweaks dependent on what I have in stock. These chassis are large and will handle plenty of weight and parts, so theyre perfect as the building block of my intentions. Also, as far as parts go, I have oodles of NOS parts, from Bradley CC resistor (which honestly I'm not a fan of but will use if specified) to vintage sockets, pots, mil spec resistors and capacitors, etc etc. Therefore the quality of the build will be high, even if I don't use EXACTLY what HAD did.

Where I need the advice of the sages here, is what direction to take with the iron I have. While I do have some iron that was intended for 4x6l6 plus 5x12ax7 family tubes SS rectified, I'd really prefer to use that iron after I've had a few D style amps under my belt as the iron is NOS and more suited to amps I'd like to make multiples of. Mostly what I have are sets of 2x6l6, 3x6l6 (yes three, from a few Hilton Voycall amps that ran 2 6l6 in PP and one in SE with a separate OT), 2xEl34, and one 2x6550. As per my goals, the 2x6550 is what I'd prefer to use first for a few reasons. 1st, the iron has the exact spacing as the holes drilled in the Carol Ann chassis and has a choke that fits as well, so less things to drill and purchase. 2nd, the 2x6550 will get me what I believe to be a closer sound overall to a 100 watt amp than the other options, due to ceiling potential of the 6550's ( I understand the 6550 will not sound like a 6L6, but in terms of headroom the 2x6550 will get me closer to the original potential of 4x6l6 than my other options). The main issue I have is I can't find a D style amp that was ever a 2x6550. I could work around the 150 watt SSS, but I really don't want an SSS if possible first, I'd prefer an ODS. Im assuming there may be some sort of SSS marriage with a ODS somewhere that I could adapt, but that takes away from my idea of wanting a base amp to tweak after, not before. Also I'm guessing I could just adapt a 50 watt circuit to take 6550's, and if there aren't any 2x6550 or 4x6550 ODS circuits, then I guess that's what I have to do. If I go that route, should I then copy the power section from the 150 SSS and adjust to use 2x6550 and pair it with a pre section from say a #102? Are there any other caveats in using 2x6550 or KT88 from 6l6 or El84 aside from adjusting the necessary component values that I need to be aware of? Also lastly, I do want to incorporate a tube FX loop in this build, as I will have the space on and in the chassis for it.

I have included a schematic (hopefully it comes out legibly) of the AIMS VTG-120 that I'm hoping to use the iron from. If you could look over the power section of that amp and see if there is anything I will need to adjust to besides any difference in values of components, as I will follow the Dumble power section of whichever amp I decide to build. Thank you for any advice in advance and I apologize for the long winded post.

[norburybrook]

If you're going to build then you should build EXACTLY as possible one of the golden builds when you start otherwise you have no reference point.

#40 , #102, #124 , Bluesmaster or #183.

If you can find NOS parts so much the better but if not use new parts that are available.


Make it as close as possible to the original and see how you like it. They're not for everyone.

If it's your thing then you can start experimenting, but I equate it to cooking: do it it like the traditional recipe first , then make a few more to taste before you start doing your own thing.


Just my view....... YMMV



M

[thesmokingwings]

If you're going to build then you should build EXACTLY as possible one of the golden builds when you start otherwise you have no reference point.

#40 , #102, #124 , Bluesmaster or #183.

If you can find NOS parts so much the better but if not use new parts that are available.


Make it as close as possible to the original and see how you like it. They're not for everyone.

If it's your thing then you can start experimenting, but I equate it to cooking: do it it like the traditional recipe first , then make a few more to taste before you start doing your own thing.


Just my view....... YMMV



M

Thank you for your input, as read many of your comments and it's nice to have a reference point now. I will try to source some iron that isn't new production (my entire reason for building in the first place was to use what is already here instead of creating a need for more consumption) for the first build and just go ahead and make it a 100 watt 4x6l6. Then I can deviate from that into the iron I have on hand and see where the similarities and differences lie and whether I can get a sound I prefer to the 4x6l6 route. Thank you again.

[norburybrook]

no worries, That's just one view though so you might get a different opinion from someone else soon


I'm no expert but I've been down this path over the last few years and I think you need to have some sort of reference point otherwise you're always chasing your tail.


You may find your NOS non standard Iron makes a nicer sounding amp but IMHO you need a bench mark in which to gauge that against.




M

[Lothy]

If you're going to build then you should build EXACTLY as possible one of the golden builds when you start otherwise you have no reference point.

In general you are right, but I think a little more critical look to those topic is needed.
I think you can burn a lot of money, if you do so. E. g. the exact values and brand of the filter caps.

Cheers
Gerhard

[norburybrook]

If you're going to build then you should build EXACTLY as possible one of the golden builds when you start otherwise you have no reference point.

In general you are right, but I think a little more critical look to those topic is needed.
I think you can burn a lot of money, if you do so. E. g. the exact values and brand of the filter caps.

Cheers
Gerhard

yes, that's true Gerhard. If you're in the EU, Sprague caps are really expensive and I don't think swapping them out for a different make will change much. I've always used F&T personally. Same with resistors just use the correct value and type 1.e carbon comp/film/ metal film etc in the correct places . Use orange drop 6ps caps when specified etc or the 715's in some builds in places and you'll be good to go.

M

[thesmokingwings]

If you're going to build then you should build EXACTLY as possible one of the golden builds when you start otherwise you have no reference point.

In general you are right, but I think a little more critical look to those topic is needed.
I think you can burn a lot of money, if you do so. E. g. the exact values and brand of the filter caps.

Cheers
Gerhard

yes, that's true Gerhard. If you're in the EU, Sprague caps are really expensive and I don't think swapping them out for a different make will change much. I've always used F&T personally. Same with resistors just use the correct value and type 1.e carbon comp/film/ metal film etc in the correct places . Use orange drop 6ps caps when specified etc or the 715's in some builds in places and you'll be good to go.

M

I have never been influenced by the snake oil of some component proponents, but I will try to emulate within reason. I have a pile of NOS 6PS caps, probably enough for all the Dumble clones I could ever want to build, and a pile of Dale mil spec resistors as well, but aside from those, I will use as high a quality part as possible. I prefer PRP resistors, but will use the Dale's and I prefer Mallory 150's but will use the 6PS also. As far as caps go, more than likely I will use Nichicon radials in the PS filtering and maybe some F&T axials if needed, but more than likely in the PS it will be Nichicon radials. I have strong feelings on transitioning into board design with radials in modern builds, as they are available at a better spec for a cheaper price, which allows for less time on the bench and an overall lower cost of ownership without sacrificing anything empirical. I'm hoping to simultaneously build a prototyping setup while I'm building this amp, as I really need on and have all of the parts available to do so. Also I have settled on a sister build for the #102 in a two tube power section that I originally wanted to do, but as advised I need a true close as possible Dumble to have a proper basis. So it will be a #102 and a D'Mars OD running 2x6L6s for power, that way I should have a good understanding of a "golden build" as it was called and an offshoot with many differences but still some of the genealogy present. I find I can typically build two amps in close to the same amount of time as one, so that's the plan. I will be starting a new thread for those builds, but would like to continue to hear advice on this thread if it's okay for now.

[fred.violleau]

Seems like you are going for a marathon on those builds! Excited to see and hear the results! I have put a d-lator inside these amps twice now, and came up with a board that respect the original design while embedding the d-lator. If you need one, I'll be glad to share.

Side note: I have also added the FX return on the front of the amp as advised by other builders. It is a great addition as it allows to open the master volume and hit the PI so you get more overtones. Then the return FX Knob becomes your new Master Volume. Added also a dry/wet knob that allows to blend the original signal with the Second stage of the FX Loop when the wet signal comes back. Love this feature with a good reverb pedal (like a TC electronic that can handle a strong signal). Only downside to it, is you can't add a delay in that FX loop chain since it will be buried far away. Your FX is a 100% wet and the blend pot only allows a fraction of the wet signal..

So I would recommend this feature if you are using reverb only, or an old rack unit like a Rocktron intelliflex or something like that. It should allow you to blend the FX the way you want, before it comes back into the FX loop.

My 2 cents here,

Good luck with your builds!

Fred.

[jcsifu]

I have put a d-lator inside these amps twice now, and came up with a board that respect the original design while embedding the d-lator. If you need one, I'll be glad to share.

Hi Fred,
Quick question. I am looking to build a Dlator into one of my clone/inspired amps, how did you tap in for plate voltage?

[norburybrook]

I have put a d-lator inside these amps twice now, and came up with a board that respect the original design while embedding the d-lator. If you need one, I'll be glad to share.

Hi Fred,
Quick question. I am looking to build a Dlator into one of my clone/inspired amps, how did you tap in for plate voltage?

I used this as a template for mine.

dumble ODS with on board loop (1).jpg

M

[fred.violleau]

I did the same as Marcus did: tap a separate node from the B+ before the preamp nodes, but with its dedicated ground point (this is where I differ from M.'s layout), 100k resistor to lower the B+ around 380v (probably need to adjust, depending on your PT).

The trick is really around the ground points to get it right. Look for Marcus's low plate build with a d-lator, Tony Albany and Erwin provide great insights as to where you should locate those ground points in order to minimize hum here:

https://ampgarage.com/forum/viewtopic.p ... 6&start=60

Cheers and happy holiday!

Fred

[jcsifu]

I used this as a template for mine.

dumble ODS with on board loop (1).jpg


M

Hey Marcus, Happy Holidays! Hope you had a fun time. Thanks for the reference layout. I'll study up while I'm waiting on parts that seem to be getting delayed forever due to bad weather.

JC

[jcsifu]

I did the same as Marcus did: tap a separate node from the B+ before the preamp nodes, but with its dedicated ground point (this is where I differ from M.'s layout), 100k resistor to lower the B+ around 380v (probably need to adjust, depending on your PT).

The trick is really around the ground points to get it right. Look for Marcus's low plate build with a d-lator, Tony Albany and Erwin provide great insights as to where you should locate those ground points in order to minimize hum here:

https://ampgarage.com/forum/viewtopic.p ... 6&start=60

Cheers and happy holiday!

Fred

Happy Holidays Fred!
Thanks for the link for the thread addressing grounding issues, I wasn't thinking of that so I'm glad you guys already discovered and solved that issue for reference. I'll read it a few times before I start to build. I'm not going to be playing for a few days as I was at a party and was handed a cheap acoustic with very high action and heavy dead strings to play songs on all night for us to sing to around a fire pit and my fingers are now misshapen and have dents and hurt really bad. I wonder if anyone else suffered similar HFS...("holiday finger syndrome").

JC

[fred.violleau]

Hahahahahaha @jcsifu, happens to me in the Summer when visiting friends and drinking wine around the fire pit with an old acoustic guitar! We can't do that outside at Christmas here in Quebec, it usually is too cold

Fred.