ODS Filtering Question

[Raoul Duke]

Hi all,
Been checking out as many build threads and actual documented Dumbles as I can here on TAG in an effort to learn more and I’ve noticed that many of HAD’s 50w builds typically have lower filtering on the power section (usually 100uf in parallel) but many who build the 100w models as “two holers” usually retain the 100w power section filtering (myself included).

I understand how filtering affects the feel and sound of an amp in a general sense (for instance-my ‘66 AC30 is night and day from dual 16 to dual 32 cans) - but I’m curious about actual experience and theory/opinion from those with more knowledge and experience with Dumble circuits.

My question is:
“Is there an advantage/disadvantage to using 100w filtering values in a 50w amp?”

Thinking about dropping down the 220s in my 102 to try and get it to feel just a little less “hard” and a little more like my 2nd gen. Waste of time?

[martin manning]

Give it a try. As I recall others have not seen a significant difference, but ymmv.

[Raoul Duke]

Martin,
I’m leaning toward experimenting with this. Just read a couple of threads where Charlie Wilson was writing about filter values and brands and had some really interesting insights regarding how they affect tone and feel. Given the vast breadth and depth of both his knowledge and experience; and the really unique things that end up on his bench - I’m intrigued by his notes on the subject (Thanks Charlie!).

This might be my next rabbit hole, lol. I’ll report any findings.

I could spend all day reading here…

[ijedouglas]

Martin,
I’m leaning toward experimenting with this. Just read a couple of threads where Charlie Wilson was writing about filter values and brands and had some really interesting insights regarding how they affect tone and feel. Given the vast breadth and depth of both his knowledge and experience; and the really unique things that end up on his bench - I’m intrigued by his notes on the subject (Thanks Charlie!).

This might be my next rabbit hole, lol. I’ll report any findings.

I could spend all day reading here…

I would definitely play around with this. I have seen a 50W Dumble with 2 x 200uf reservoirs so clearly even HAD experimented with it

[Raoul Duke]

What really prompted me to dig into this is the BM Ripper thread where HAD had the parallel 100uf in a 6th gen 50w amp.
Got me thinking…

[Raoul Duke]

Here’s my impressions from the filter cap experiment I’ve conducted over the past couple of days. They are of course just opinion and this was by no means scientific - but certainly a great learning experience for someone new to amp building.

First went from dual 220s to dual 100s (both sets F&T). Definitely a looser feel with a bit of ghosting at extreme highs and lows. Didn’t really sound or feel like my 102 anymore.

Then went up to dual 180s (SC brand). Pretty much sounded like the 220s again with a very slight increase in bass response that I’d probably attribute to brand difference.

Next installed dual 150s (SC) and they seemed to have a little of the looseness of the 100s with a more balanced tonal response. Ok, they seem pretty good - so I’ll leave them in and come back tomorrow (this morning) with fresh ears.

This morning, they still sounded good with none of the tight “buzz”-like feel of the 220s which got me thinking about all this in the first place. Guess I’ll leave them in for awhile and see.

I know there’s a lot more variables (brands, values etc) that I haven’t tried and the incremental differences are pretty small; but it was an interesting experiment nonetheless. Also may have convinced me that the full precision PS might be part of my next build just because of the variety of brands and values available (at lower cost).

More to ponder…

[bepone]

more filtering, tighter the bass.. lower the fitering as low as 33uF for first cap - looser bass and ghost notes are increasing.. i like lower filtering and vintage bass warmth in the sound, it is good for slower blues sound.. for metal opposite, high filtering is necessary

[Raoul Duke]

Makes sense from what I’ve read and now experienced.

Been researching snap-in caps to replace the large axials in whatever I build next and have a few general questions regarding implementation:

1. Should the leads be bent once through the board for more mechanical support? Any need for RTV to hold them?

2. What’s the preferred method for (mechanically) attaching wires to the leads? I.e: Loop the wire around exposed lead and solder?, crimp lead around wire etc?

3. I see in Martin’s excellent drawings that eyelets are not required under the caps and I understand that they would prevent the base of the cap from sitting squarely on the board; but might smaller, flatter eyelets work while providing a common solder point ?

4. For the smaller value axial caps: when running the leads under the board to the eyelets where they come back up/through - is it better to carefully flatten the leads to the bottom of the board or use small arcing bends?

5. Am I way overthinking this and is it a “just figure out what works for you” kind of thing?

Love to get some opinions from the more experienced folks on this.

Thanks all!

[martin manning]

First went from dual 220s to dual 100s (both sets F&T). Definitely a looser feel with a bit of ghosting at extreme highs and lows. Didn’t really sound or feel like my 102 anymore.

Then went up to dual 180s (SC brand). Pretty much sounded like the 220s again with a very slight increase in bass response that I’d probably attribute to brand difference.

Next installed dual 150s (SC) and they seemed to have a little of the looseness of the 100s with a more balanced tonal response. Ok, they seem pretty good - so I’ll leave them in and come back tomorrow (this morning) with fresh ears.

This morning, they still sounded good with none of the tight “buzz”-like feel of the 220s which got me thinking about all this in the first place. Guess I’ll leave them in for awhile and see.

100W ODS use 2x 220uF (110uF net), and in at least one case 2x 300uF (#124, 150uF net). The 50W are shown with 2x 100u, but I would argue for 2x 150u to be consistent with the 100W amps. I believe there is a square root factor involved due to the relationship between current and power, and with that assumption a 50W would want (50/100)^0.5 times the reservoir capacitance of a 100W, 0.707 x 220u = 156. Anchoring on the 2x220u being "normal" for 100W ODS, and Raoul's 50W experiments that showed 2x 150u to be about right, and 2x100u to be quite loose, the relationship below is produced. If #124's 2x 300u is taken as a good reference for "tight," a 50W with 2x 220u would be the same, which also seems to line up quite well with Raoul's observations.

[WhopperPlate]

A) series caps in power supply , not parallel

B) f&t caps in most circuits are grainy and annoying on the ears .

C) as evidenced by your experience , the differences between 220 and 100 uf caps is quite significant . Congratulations, you aren’t numb to the changes

[martin manning]

Updated the plot above to show 2x 6V6GT 22W. The theory suggests 50u for the reservoir, which compares nicely against AB763 Deluxe Reverb's 32u, or the often used 2x 22u for 44u reservoir capacity.

[Raoul Duke]

This is all very interesting for sure and I appreciate the feedback Martin and Charlie (even though I got the terminology wrong, lol)! Martin - your ability to assimilate raw data and map out the trends in such a logical, mathematical way is really impressive and shows how much you truly enjoy this. Very inspiring.

My experience with the reliable amp techs in my geographic area is that F&T are the best - which makes sense from a repairman’s perspective because they seem to be super reliable and high quality; which from a billable hours standpoint I would think is more important than tone (just trying to be pragmatic from a business perspective). Maybe something like:

“Tone isn’t really a primary concern because if you didn’t like your amp’s tone - you’d be selling it and not bringing it to me for re-capping. I’ll use the components that I know will be reliable regardless of how they affect the tone and let you figure out the rest.”

Makes sense - I’d probably look at it the same way if in the typical tech’s business situation.

Charlie - regarding the F&Ts - “grainy” is the right word I was searching for but couldn’t find. It’s subtle, but noticeable if you’re inclined to really listen IMO.

Currently planning my next build and thinking Bluesmaster HRM. Trying to choose between Roderstein and Sprague for the big filter caps. Any suggestions from those who’ve heard both? Definitely going with the Precision PS with snap-in caps.

Thanks again guys!

[bepone]

with the radial snap ins there is a lot of choice..im using mostly Nichicon or UCC.. with axials not so much...

[martin manning]

Been researching snap-in caps to replace the large axials in whatever I build next and have a few general questions regarding implementation:
1. Should the leads be bent once through the board for more mechanical support? Any need for RTV to hold them?
2. What’s the preferred method for (mechanically) attaching wires to the leads? I.e: Loop the wire around exposed lead and solder?, crimp lead around wire etc?
3. I see in Martin’s excellent drawings that eyelets are not required under the caps and I understand that they would prevent the base of the cap from sitting squarely on the board; but might smaller, flatter eyelets work while providing a common solder point ?

Just snap the caps into the 2mm holes, wrap the under-board lead wires around the terminals close to the board on the back side, and solder. That should lock them in place.

4. For the smaller value axial [radial] caps: when running the leads under the board to the eyelets where they come back up/through - is it better to carefully flatten the leads to the bottom of the board or use small arcing bends?

Insert the caps and bend the leads flat, 90 degrees. That should hold them tightly against the board. You may have to bend say 70 degrees, cut to length, put the 90 degree bend in for the bit that goes up through the eyelet, bend the lead flat against the board, and finally bend the clipped end over on the top side.

In both cases a very small amount of the right kind of silicone under the caps wouldn't hurt, but it probably isn't necessary.

[Raoul Duke]

Thanks guys!

Tremendously helpful Martin! I know it’s small stuff but I like to do things right the first time. Understanding the details is important to me because…

I also like to do a number of visualization “reps” for delicate or unfamiliar processes before I actually attempt them. Probably sounds a bit goofy, but I find that it increases my chances of doing it right the first time because it forces me to think through each step and usually reveals bits I hadn’t previously considered; thereby decreasing my need to improvise “on the spot” which may lead to having to re-do something later.

Gerry Brown would approve, lol…

Thanks again!