My first Dumble finally started

[Tdale]

This if my first time using a board, so it's pretty exciting. I'm attaching a photo of the board, with a few parts in place. Looks pretty ok I think..let's hope it'll sound even better

By the way. I read some place that big cathode caps give a bassy sound, while small give a more mid rangy sound, while in between, say around 4-8 uF, gives a more "fusion" sound... Does this make sense?

Tommy

[dogears]

Looks good Tommy.....


Trust me on this.... Try and find milspec metal films for the plates. It does matter and is noticeable..... As far as I know, Dumble never ever used carbon on the plates.

Do it right as you will be investing a lot of time in the project.

It is easy to change bypass caps or add a switch to toggle CL2 between 1, 5, and 10uf. I find this very useful and the difference between 5 and 10 is much more noticeable than you would think!!

[Tdale]

Ok.. high watt too, or just normal wattage metal film mil spec?

Any recommendations?

Tommy

[dogears]

Vishay Dale RN65

Mouser has them. 1/2 watt rated but probably more like 1 watt.

Funkalicious Groove, Normster, Bob I, Pedro, etc... have all tried them and agree!!!

Ok.. high watt too, or just normal wattage metal film mil spec?

Any recommendations?

Tommy

[Tdale]

Thanks! This forum is GOLD!!!

I made a Matchless DC30 clone, using only Riken ohm carbon film resistors all through, except in the power supply. I wonder what would happen if I got some metal films for the plates.

How exactely does the metal films affect the sound?

Tommy

[dogears]

I used Riken Ohm in my clone but swapped to the RN65 and prefer the metal films..... They have a certain "ting" on top. Not sure they would work well in other amps. Something about the topography of the Dumble seems to make them a great match!

Plus they are cheap

Btw, try using 160k-180k to feed the 100k pre-OD trimmer. I like the dynamic sound more than a 220k.

Also, I like the Skyliner stack. .01 midcap, 250ka mid pot, .001uf across a 500ka bass pot. Here is another tip if you are using midboost. Dumble used a .002 PS Orange drop and a 390pf in series. Not a .0022uf I know it is a minor point, but I like the sound of the net treble cap around 315pf to 320pf. WIth a .0022uf you are over 330pf. Every little bit of blueprinting and love counts IMO.

[Tdale]

I was planning to use the other od entrance... with a bridge resistor, and two resistors from each end, through a trim pot and then to ground..

But I hear lots of good things about the 220K into a 100K trim... or as you say, 160-180 into the trim..

The good thing with using a board in stead of point to point, is that it's pretty easy to make changes...

Tommy

[dogears]

I can't stress enough to NOT use that wierd network. It is not in any "grail" era amp I ever heard of. The only reason people even try it is because a couple of early ungooped Dumbles had it. He moved on.... Don't waste your time.

I was planning to use the other od entrance... with a bridge resistor, and two resistors from each end, through a trim pot and then to ground..

But I hear lots of good things about the 220K into a 100K trim... or as you say, 160-180 into the trim..

The good thing with using a board in stead of point to point, is that it's pretty easy to make changes...

Tommy

[Tdale]

That's noted

Tommy

[jazzyjoepass]

Dogears is right.

Metal films do good to lower the noise floor and there's a sparkle when u use them. The higher the wattage rating the better. If you have a choice between 1 watt and 0.5 watt, take the 1 watt - lesser noise.

Regarding the network to the OD, 220k works (or 150k) into 68K is much simpler to wire and u get good immediate results ....


Cheers.

Happy cloning ...

[Tdale]

And not use the trim you mean? Is there any resistor to ground in the way you explained?

[jazzyjoepass]

Oops, I meant with the trimmer ...

[hipbluescat]

If the metal resistors are the one to use then what about capacitors.

Would you only use Sprages 716 series ?

Ans for electrolytic capacitor use the blue Sprages also ?

[Ellicaster]

How's the Dumble amp coming along? Do you have a good schematic available and a parts list?

Many thanks.

Ellis

[Tdale]

http://www.youtube.com/watch?v=8lMCS3raYN8

Working on the cab..and tweaking the sound

Tommy