ODS Filtering Question

[cdemike]

I'm glad I re-searched this because I was about to ask how to scale filtering from 50w to 100w or vice-versa in the tech section. Really helpful mathematical analysis -- thanks!

I did want to get clarification on something, though: it's not really clear to me why filtering would scale as a square-root basis rather than linearly. Maybe it'd be helpful if I laid out how I was thinking about it. The formula I'm familiar with and use for power calculations is P=IV (and variations thereof mostly using substitutions derived from Ohm's law), and the formula I dug out of the old physics textbook for energy stored in a capacitor is E=0.5C(V^2). Assuming no differences in ESR or the B+ dropping string and taking into account that power is energy over time, I can't see a reason why energy stored in a capacitor wouldn't be a reasonable stand-in to determine a filter capacitor's role in a circuit since the time involved should be the same. Since someone trying to scale 50w to 100w or vice-versa would likely keep B+ the same or reasonably similar, it could be considered constant. So with the assumption of equal B+, the power function could be reduced to P=I, where the only difference would be the current requirements of the output section (should scale linearly as multiples of push-pull pairs in this case). Turning to the energy stored in a capacitor, voltage is again constant, as is the coefficient 0.5, so we'd get E=C, which again should scale linearly.

Where am I going wrong?

[martin manning]

I don't have a complete theory, but I don't think it's just steady-state power. At this point it's a correlation, where the square root relationship seems to fit quite well with observations.

[Blues Hound]

I wanted to see if there is a preference to use Audio grade caps vs General purpose caps for the filtering.

I watched a video on YouTube where the tech was replacing caps in an audio amplifier, he was looking at Nichicon caps, Audio grade.

https://www.youtube.com/watch?v=37JCDYgzZdU

For the voltages that are used in ODS amps, over 300V, around 8:30, the General use caps seemed to be of better quality at a lower cost, LKX (Audio grade) vs LLS (Gerneral purpose)

I recently changed out the F&T 220uf caps in my 102 to Nichicon 220uf 400V and there was a noticeable difference in the OD tone being smother, the Nichicon are a general purpose cap.

Thanks,
Steve

[WhopperPlate]

I recently changed out the F&T 220uf caps in my 102 to Nichicon 220uf 400V and there was a noticeable difference in the OD tone being smother, the Nichicon are a general purpose cap.

Yes

[Roe]

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

+ 1, but it varies since not all of these caps are the same. some are designed specifically for tube amps while others are more generic caps for any kind of power supply. Typically, the problem with graininess concerns the latter type of cap (whereas the former tend to sound just fine in my experience). For some of these caps and datasheets, see https://www.die-wuestens.de/eindex.htm

[award70]

What does "grainy" sound like and what might cause this?

Alan

I’m not trying to be a smartass or start anything….I would like to know.

[martin manning]

I recently changed out the F&T 220uf caps in my 102 to Nichicon 220uf 400V and there was a noticeable difference in the OD tone being smother, the Nichicon are a general purpose cap.

I'm wondering what the condition of the F&T's was. Were they old?

[pullshocks]

Side question--I had not heard of SC capacitors before. Who sells them?

[WhopperPlate]

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

+ 1, but it varies since not all of these caps are the same. some are designed specifically for tube amps while others are more generic caps for any kind of power supply. Typically, the problem with graininess concerns the latter type of cap (whereas the former tend to sound just fine in my experience). For some of these caps and datasheets, see https://www.die-wuestens.de/eindex.htm

Yes, I admit I have only tried the generic variety, which also seems to be what most people use and have access to from typical vendors. I have wanted to try the variety made for tube amplifiers, as there are aspects of the generic’s character that I do like, so I am hopeful from your testimony . As long as they punch in a mix that’s half the battle

[Blues Hound]

I recently changed out the F&T 220uf caps in my 102 to Nichicon 220uf 400V and there was a noticeable difference in the OD tone being smother, the Nichicon are a general purpose cap.

I'm wondering what the condition of the F&T's was. Were they old?

Martin,

They were new when installed less than two years ago.

After reading a thread on filter caps I swapped out the F&Ts to Nichicon and there was a noticeable difference in the OD being smoother, much smoother.

I was asking if anyone has tried Audio Caps vs General purpose caps, I used GP caps and they sounded great, I have just put together a PPS with Audio caps and have yet to A/B it against the current PPS.

Steve

[ijedouglas]

I was asking if anyone has tried Audio Caps vs General purpose caps, I used GP caps and they sounded great, I have just put together a PPS with Audio caps and have yet to A/B it against the current PPS.

Steve

I wish I knew the formula I have tried "good"/"quality" caps and they have sounded shitty and then crappy caps that everyone scoffs at and they sounded great. The trick is to listen with your ears and not your eyes.

I have yet to see a real ODS with F&T caps in it, yet we keep seeing folks put them in their amps and expect them to sound like the real thing....

[WhopperPlate]

One of the biggest changes for the better I ever achieved fine tuning amplifiers was removing those generic F&T caps. I have swapped more than a few sets out of clients amplifiers, and its always night and day better compared with anything else, and they are much happier afterward. single notes , especially on the high strings and above the 12th fret, have more clarity and punch with other brands. I struggled for years as a kid trying to be heard in that range within a dense loud band mix on stage, playing my main home built amplifier ( using F&T because they are the "best"), before I thought to myself, "I wonder if changing the filter caps will help...".

[WhopperPlate]

What does "grainy" sound like and what might cause this?

Alan

I’m not trying to be a smartass or start anything….I would like to know.

Harsh, irritating especially in the high end, definition and clarity lacks up top and doesn't sing , high end harmonic feedback also subsequently sounds terrible and screechy, causes ear fatigue, makes you want to turn down or turn off your amplifier, and anticipate the end of the gig or rehearsal.

[martin manning]

...They were new when installed less than two years ago.
After reading a thread on filter caps I swapped out the F&Ts to Nichicon and there was a noticeable difference in the OD being smoother, much smoother.

Well there's a data point anyway. My ODS has a mix, F&T for the reservoir and the rest are Nichicon in a precision type PS.

[WhopperPlate]

...They were new when installed less than two years ago.
After reading a thread on filter caps I swapped out the F&Ts to Nichicon and there was a noticeable difference in the OD being smoother, much smoother.

Well there's a data point anyway. My ODS has a mix, F&T for the reservoir and the rest are Nichicon in a precision type PS.

I have found the negative attributes are tempered when used intermixed with other capacitors