Thanks so much for the information!!
One of my little amplifiers was running on a 36vct, 1 amp transformer, I tried snubbing the rectifier to cool it off (less heat at heatsink), which it did, but it didn't sound right.
I had mistakenly tried using the same 10nF that I had seen in my big amplifier's service manual.
Now I find out that the needed value for the little amplifier was 820pF. OMG!! That's a huge difference.
Well, no wonder.
EDIT: Yes, the right size works nicely.
Thanks again!!!
EDIT: As promised, a photo, because not everyone has Excel software.
One of my little amplifiers was running on a 36vct, 1 amp transformer, I tried snubbing the rectifier to cool it off (less heat at heatsink), which it did, but it didn't sound right.
I had mistakenly tried using the same 10nF that I had seen in my big amplifier's service manual.
Now I find out that the needed value for the little amplifier was 820pF. OMG!! That's a huge difference.
Well, no wonder.
EDIT: Yes, the right size works nicely.
Thanks again!!!
EDIT: As promised, a photo, because not everyone has Excel software.
Attachments
danielwritesbac said:Thanks so much for the information!!
One of my little amplifiers was running on a 36vct, 1 amp transformer, I tried snubbing the rectifier to cool it off (less heat at heatsink), which it did, but it didn't sound right.
I had mistakenly tried using the same 10nF that I had seen in my big amplifier's service manual.
Now I find out that the needed value for the little amplifier was 820pF. OMG!! That's a huge difference.
Well, no wonder.
EDIT: Yes, the right size works nicely.
Thanks again!!!
EDIT: As promised, a photo, because not everyone has Excel software.
Any first impressions on the tweak?
Regards
konstantin said:
My little LM1875 project didn't improve nor degrade the sound, but did run cooler.
I don't have any that are technically gainclone style, so I couldn't comment on what the tweak does with a gainclone.
Hey, thanks for the lower temps!!
I think that this will be mighty helpful on getting my new parallel+bridge amplifier more compact and affordable.
AndrewT said:
Hi Andrew,
Would you share your experience in that respect.
What is the capacitance you use before the transformer?
Do you use only X rated caps and do you use them between hot and neutral?
Do you use Y rated caps - between phase or neutral and earth?
Most often heard critics are that the use of these affects the dynamics. What is your impression?
Thanks, Baki
Hi konstantin
Thanks for the fast reply. i start to get and absorb all the information on this threat.
actually i have 2 more transformers i want to try .
my guess on the caps:
EI transformer 2x15v 30VA needs ard 450pF
and toroid transformer 33v 0v 33v 300va needs ard 15nF
which is just need to find out the actually commercial values
pls correct me if im wrong
whats the relationship between Ampere and VA?
thanks alot, Erwin
Thanks for the fast reply. i start to get and absorb all the information on this threat.
actually i have 2 more transformers i want to try .
my guess on the caps:
EI transformer 2x15v 30VA needs ard 450pF
and toroid transformer 33v 0v 33v 300va needs ard 15nF
which is just need to find out the actually commercial values
pls correct me if im wrong
whats the relationship between Ampere and VA?
thanks alot, Erwin
milen007 said:
A center tap transformer advertised 1 amper and 36vct (2x18) is 36VA. A 2 amper transformer of 36vct (2x18) is 72VA.
To do the other calculations, scroll up and spot either the photograph or one of the spreadsheets and click on one of them. You can then see the relationship between different sizes.
Many sizes of EI core are listed.
To get a "single" transformer size, like 12v (1x12) use the "dual secondaries" section of the chart, look up the 12+12, and use only one cap.
Hi danielwritesbac
thanks for the clarification, i am starting to get it. my guesses are below :
EI transformer 2x15v 30VA needs ard 560pF or 680pF
and toroid transformer 33v 0v 33v 300va needs ard 12nF or 15nF
which is just need to find out the actually commercial values
pls correct me if im wrong
thanks for the clarification, i am starting to get it. my guesses are below :
EI transformer 2x15v 30VA needs ard 560pF or 680pF
and toroid transformer 33v 0v 33v 300va needs ard 12nF or 15nF
which is just need to find out the actually commercial values
pls correct me if im wrong
Very nice clarification here, I was already planning on introducing this capacitor, but all references I saw to it simply said 100nf, without explanation about the value.
From the chart given here, I'm assuming that for 2x24V 120VA toroid transformers. I'll need 3300 pF caps, considering the closest ready-made value, is that correct? I've easy access to both polyprop and ceramic caps, polyprop rated at 250V, ceramic rated at 500V. Both choices should be fine, right?
From the chart given here, I'm assuming that for 2x24V 120VA toroid transformers. I'll need 3300 pF caps, considering the closest ready-made value, is that correct? I've easy access to both polyprop and ceramic caps, polyprop rated at 250V, ceramic rated at 500V. Both choices should be fine, right?
Atilla said:
Edit: Here's my opinion on the topic. Its opinion because I believe that the eventual outcome of the audio amplifier's signal has no other purpose than to please an ear. Of course, that would be mine, and thus this particular post is all opinion/observation.
The difference in audio should come from the slight voltage drop; however, if your audio comes across like soda pop with the fizz gone out (poor dynamics), then the caps that you have chosen are too large for your application.
Accidentally too large: A capacitor with a higher ESR (internal resistance) is R-C-R in nature, albeit the "R" varies considerably by bandwidth. Higher ESR caps, although potentially less effective, will "do" a different bandwidth than expected, and thus may need a different size than listed. This is especially true of, (but not exclusive to) small dip/bubble, caps.
So if I'm asked to choose between "mystery poly" or the certain results of ceramic, then I'll answer Ceramic because it has been used for this application since the early years of diodes.
The OP (original poster) suggested Wima FKP-2, and I do not have the knowlege to suggest any alternative model of plastic capacitor. In my opinion, other models of poly would be a random experiment.
It appears that we have two different purposes in this application. As for me, I already liked the sound of my amplifiers. As I didn't want to alter the audio, I chose smaller cap values than indicated by the chart. I received the benefit of much less heat at the heatsink. This benefit was far more than the expected proportion of the 1.2v voltage drop.
First production run from Technics came with 10nF ceramic for a 300VA, 52vct (2x26), transformer. Without the caps, it would get very hot at the heatsink--like a space heater. With the caps in place, it runs at sane temps.
EDIT2: Whether its handmade or production, I believe that the cooler temps, without introducing audio abberation, is a "step in the right direction" because it is an increase of efficiency.
Unexplored:
One would assume that a 100v rated diode will make different results than an 800v rated diode--as to the application of snubbing the rectifier. I believe that the results would vary, especially as to the outcome of affecting the dynamics of the audio signal. My apologies, because I don't know which direction is "better." I'd guess that the higher capacity diode is less likely for voltage drop under load, but I just don't know. Can someone please clear that one up? Thanks!
Actually, I was more reffering to the actual capacitance values and that both voltage ratings are high enough for this application.
I certainly don't want to engage in a "which type of cap sounds better" discussion, while I'm sure that if there's anything wrong with a specific cap type, it'll be brought up very quickly
Slight voltage drop can't do me too bad with 2x24V secondaries for a LM3886 I believe.
I certainly don't want to engage in a "which type of cap sounds better" discussion, while I'm sure that if there's anything wrong with a specific cap type, it'll be brought up very quickly
Slight voltage drop can't do me too bad with 2x24V secondaries for a LM3886 I believe.
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