I would like to upgrade the power supply by-pass capacitors in my tube amp and have a question that maybe someone here can help me with. I am not an expert at this but I can solder and have changed out the caps on my DAC with great results so I would like to do the same with my amp. My question is this, the caps that are in the amp are 450v 470uf, I can not find capacitors from the major manufacturers at the 450v spec. I can find 400v and 600v, so would either of these work in my amp and if so what general differences can I expect going either a little higher or lower on the voltage of the cap. Thanks in advance guys.
Capacitor question
- Thread starter DWR
- Start date
Farnell UK has lots of caps with your exact values DWR from the likes of ELNA, Panasonic, Cornell, etc. Have you tried looking there? Most audio centered cap makers concentrate on coupling cap or XO cap values.
Those are probably power supply storage capacitors. Never go lower; you can go higher, so use the 600 V capacitors if that is your choice.
Lower voltage rating increases the risk of the capacitors shorting (destroying themselves and potentially other parts in the compenent) and will decrease their lifetime (and lower their performance over their lifetime).
Going higher often requires more space (volume) for equivalent capacitance, and they are often a little "slower" though I seriously doubt you would notice in an audio power supply application.
HTH - Don
Lower voltage rating increases the risk of the capacitors shorting (destroying themselves and potentially other parts in the compenent) and will decrease their lifetime (and lower their performance over their lifetime).
Going higher often requires more space (volume) for equivalent capacitance, and they are often a little "slower" though I seriously doubt you would notice in an audio power supply application.
HTH - Don
Thanks guys, that is pretty much what I thought, the 400v is just going to be too low for safety sake. I really wanted to try some of Modwrights new caps but they only make 400v. I will go with some 600v Auri Caps. Yes Jack I have been looking on the Farnell UK site as well. Again thank you guys.
If you are choosing film capacitors for bypass you should take care that some manufactures specify max DC operating conditions and others specify AC. Since you refer the voltage of the electrolytics the 450V is a DC rating.
Yes that is correct and some have tolerances up to 10% +/-, but even at that it would be pushing the limits too close for my comfort. So I f I end up going this route I will use the 600v capacitor and be safe.
I apologize if this is known 
. But please, please be safe in making such mods. Even if your system is off, caps inside may hold full charge and at 400 volts and 470uf, touching that cap may have dire consequences. All the caps inside the box need to be bled to zero before touching anything. No jewelry worn (watches, rings, necklace, etc). Wear shoes. Turn the box on and then unplug it (don't use the on/off switch -- this will bleed more of the energy from the caps). And above all, make sure at all times the power cable is in your sight, with it not plugged into anything! Hang the end of it on top corner of the box while you are working it and if you ever notice it is not there, stop working.
Electricity is a simple thing to do safely but if you make one mistake, you may not be around to make the second one! Despite years of experience, I have gotten shocked a number of times from sloppy procedure. I have lived through it but you may not.
Again, I am sorry if you know all of this and this is old news.
. But please, please be safe in making such mods. Even if your system is off, caps inside may hold full charge and at 400 volts and 470uf, touching that cap may have dire consequences. All the caps inside the box need to be bled to zero before touching anything. No jewelry worn (watches, rings, necklace, etc). Wear shoes. Turn the box on and then unplug it (don't use the on/off switch -- this will bleed more of the energy from the caps). And above all, make sure at all times the power cable is in your sight, with it not plugged into anything! Hang the end of it on top corner of the box while you are working it and if you ever notice it is not there, stop working.Electricity is a simple thing to do safely but if you make one mistake, you may not be around to make the second one! Despite years of experience, I have gotten shocked a number of times from sloppy procedure. I have lived through it but you may not.
Again, I am sorry if you know all of this and this is old news
.
garylkoh
WBF Technical Expert (Speakers & Audio Equipment)
Power supply storage caps and crossover caps are designed for very different purposes. Just because you get the correct rating (470uF 400V) does not mean the correct type of caps. Microstrip mentioned film caps - those are good for bypass, for crossovers, and not as good for coupling, I've never encountered these as storage caps (they would be huge!). You mentioned that you want to change out the power supply by-pass caps.
The purpose of these is ripple smoothing. So, you want a polar electrolytic cap that has at least 470uF to get the same amount of smoothing as the originals. Do not go below 400V. However, going from 470uF to 560uF will be far more advantageous than going from 400V to 600V. You get more energy storage - resulting in a tighter, more defined bass. Going too far in this direction might get you bloated bass. For this purpose, I like the Panasonic TS-HA series. They have the lowest ESR and ESL (fastest).
Try bypassing the cap (another cap in parallel) with a good quality low capacity, but high-voltage part. I like the Wima polyester film caps in this instance. You will get more clarity and definition in the high frequencies.
Both of the above can be gotten from Digikey.
You get BIG advantages if you buy a bunch of each cap, and then measuring each one to find matched pairs. Use a meter like this one:
http://www.bkprecision.com/products...-handheld-lcr-meter-with-esr-measurement.html
Reason being that you have one cap on the "push" side, and one cap on the "pull" side of the typical amp. You buy matched-pairs of tubes....
Disclaimer: I don't know what amplifiers you are modifying..... and the experience I have stems from designing one single tube amp.
The purpose of these is ripple smoothing. So, you want a polar electrolytic cap that has at least 470uF to get the same amount of smoothing as the originals. Do not go below 400V. However, going from 470uF to 560uF will be far more advantageous than going from 400V to 600V. You get more energy storage - resulting in a tighter, more defined bass. Going too far in this direction might get you bloated bass. For this purpose, I like the Panasonic TS-HA series. They have the lowest ESR and ESL (fastest).
Try bypassing the cap (another cap in parallel) with a good quality low capacity, but high-voltage part. I like the Wima polyester film caps in this instance. You will get more clarity and definition in the high frequencies.
Both of the above can be gotten from Digikey.
You get BIG advantages if you buy a bunch of each cap, and then measuring each one to find matched pairs. Use a meter like this one:
http://www.bkprecision.com/products...-handheld-lcr-meter-with-esr-measurement.html
Reason being that you have one cap on the "push" side, and one cap on the "pull" side of the typical amp. You buy matched-pairs of tubes....
Disclaimer: I don't know what amplifiers you are modifying..... and the experience I have stems from designing one single tube amp.
garylkoh
WBF Technical Expert (Speakers & Audio Equipment)
I apologize if this is known
Electricity is a simple thing to do safely but if you make one mistake, you may not be around to make the second one! Despite years of experience, I have gotten shocked a number of times from sloppy procedure. I have lived through it but you may not.
Again, I am sorry if you know all of this and this is old news
And I'll second this...... from bad experience.
An old tube-hand told me that the trick they use to live that long is to always make sure that they have one hand behind their back..... so that there is no path for the electricity to flow through the heart.
Be sure that you are not grounded anywhere on your body, and you'll get a nasty shock. Grounded anywhere - feet, hand and it may stop your heart.
Excellent advise on the safety points, I follow each and every one of them, electricity is nothing to play around with (I was a fireman for 23 years, water and electricity really don't mix, and in 23 years I only goy one good shock, being complacent). Also, thanks for the technical advice Gary, I am not even sure if I am going to go this route or not. The amp in question is a Jolida JD-1000P. 100wpc push/pull EL-34. I know what caps some of the people offering modification service use, so I just have to decide if it is worth it for the money involved to change the caps or move to another amp. I went thru this same thought process with my CJ preamp and decided to have it modified and I am totally satisfied with the money spent on that piece, that one I couldn't do the mods myself so I had it done.
True, but I would like to add a note - do not use an insulated screwdriver or similar to bleed the capacitors - if they are still charged the power of the fast discharge can be very high, damage the screwdriver and yourself. I have a very high quality needle nose pliers that got damaged this way.
Check the capacitors with a voltmeter and discharge them using a power 10 kohm resistor if needed.
I owned a tube power amplifier that was fused between the capacitors and the transformer leading to the anode tubes. If the fuse broke, the power capacitors would retain almost full power for hours, as the bank wast formed with low leakage film type and there was no bleeding resistor.
A proper high voltage power supply should have bleeder resistors installed across the filter caps, to bleed off the voltage after the device has been switched off. If yours does not have these I would suggest installing some when you make the cap change. Shoot for about 1 or 2 mA of current ( in other words, a 270K to 470K ohm resistor will work well for a 450V power supply) and be careful use a resistor of adequate power dissipation and voltage rating. There are several 2W to 3W resistors out there with an appropriate voltage rating of around 750VDC. Carbon film is fine to use in this application. It will still take some time for the residual charge to drain with these installed, so continue to use caution around the filter caps.
In '73 I worked on 20,000 watt transmitters that had capacitors the size of a large car battery. Those bad boys would suck the electrons out of the air, if you didn't hang a grounding rod on a terminal.
another idea for no bleeder resistors used, separate high voltage supply and low voltage supply for filament into two switches connect as picture show, turn one on first( no matter which one) wait for a while and turn the other on later.use same way to turn it off too,in this way will drain off the power from all caps
tony ma
Attachments
Purity Audio Design 1
Well-Known Member
If you are only installing/replacing caps to bypass (in addition to) the power supply filter caps already inside the Jolida, a decent film cap will do just fine. The 470uF caps are the main filter caps in the power supply. Your thought of using AuriCaps is a good one. I have modified hundreds of Jolida amps from the little 102 to the 1000A. As other have mentioned, replacing these caps with a better quality, lower ESR version would bring excellent results. The Panasonics are my favorite and you can bypass these with your AuriCaps. Going to 560uF will also not cause any problems and will in fact bring you better control.
Another inexpensive tweak to the power supply would be removing those cheap silicon diodes and replacing them with a good quality "Ultra Fast - Soft Recovery" diode. This will also provide a quieter presentation as those cheap silicon pieces can be noisy.
The Jolida amp can be tweaked to no end but also as others have mentioned, if you are uncomfortable with doing this work on your own, be sure to have someone with experience perform the work for you. Doing things wrong could not only damage your amp but also cause some serious injury.
Another inexpensive tweak to the power supply would be removing those cheap silicon diodes and replacing them with a good quality "Ultra Fast - Soft Recovery" diode. This will also provide a quieter presentation as those cheap silicon pieces can be noisy.
The Jolida amp can be tweaked to no end but also as others have mentioned, if you are uncomfortable with doing this work on your own, be sure to have someone with experience perform the work for you. Doing things wrong could not only damage your amp but also cause some serious injury.
Thank you very much Bill and welcome to the forum. I know you have modded a lot of Jolida amps, but I see on your website you are not doing any mods presently.
Purity Audio Design 1
Well-Known Member
Hi DWR. Thanks for the welcome to WBF.
No, at this moment we are not taking in any modification work since the development of Purity Audio Design. If/when we get back into it will be determined at a later date but as I mentioned, the Jolida pieces are a good value and take well to upgrades. They do have their limitations but at their price points..........
No, at this moment we are not taking in any modification work since the development of Purity Audio Design. If/when we get back into it will be determined at a later date but as I mentioned, the Jolida pieces are a good value and take well to upgrades. They do have their limitations but at their price points..........
I suppose that you are changing the PS BYPASS caps to get better rippling suppression.
As a rule of thump i bypass with 1/100 value but use the higher standard caps that i can find.
It's a safe bet to use higher voltage caps - so for a main PS cap of 400V i wouldn't use as a bypass cap
anything lower than 600V.
If you're after a double bypass(!), again use 1/100 value of previous bypass cap with even higher voltage,say 800V or 1000V.
An example :main cap 470uf/400V - first bypass 4,7uf/600V-second bypass 0,047uf/800V.
Mixing capacitor types usually gives better results.I have used to good effect polypropylene as first bypass and PIO as second bypass.
Always use the lowest ESR caps that you can find, plan carefully before buying as usually space is limited and always buy a couple more than needed "just in case".
The effect will be noticable in a revealing system as a smoothing out of things,quietness,better harmonics and microdetail.
If you are after bigger impact (especially in the bass-low mid) you could increase your "battery" power by changing the main PS caps to the next level:from 450uf/400V to 560uf/400V.
In such a case, i consider the double bypass 1/100 route as a nececity!
Be forwarned that caps usually get taller and wider when you up the power reserve (ufs) or the operation voltage (Volts).
Bleed the power out of the caps with a big resistor (i use a 50 Watt 25Kohm type).
After doing this to all capacitors of the PS bank,REPEAT the procedure once more!
Your life is worth the extra care!
Also be carefull when taking out old caps:it's easier than you think to strip a trace on the board!
Have fun!
As a rule of thump i bypass with 1/100 value but use the higher standard caps that i can find.
It's a safe bet to use higher voltage caps - so for a main PS cap of 400V i wouldn't use as a bypass cap
anything lower than 600V.
If you're after a double bypass(!), again use 1/100 value of previous bypass cap with even higher voltage,say 800V or 1000V.
An example :main cap 470uf/400V - first bypass 4,7uf/600V-second bypass 0,047uf/800V.
Mixing capacitor types usually gives better results.I have used to good effect polypropylene as first bypass and PIO as second bypass.
Always use the lowest ESR caps that you can find, plan carefully before buying as usually space is limited and always buy a couple more than needed "just in case".
The effect will be noticable in a revealing system as a smoothing out of things,quietness,better harmonics and microdetail.
If you are after bigger impact (especially in the bass-low mid) you could increase your "battery" power by changing the main PS caps to the next level:from 450uf/400V to 560uf/400V.
In such a case, i consider the double bypass 1/100 route as a nececity!
Be forwarned that caps usually get taller and wider when you up the power reserve (ufs) or the operation voltage (Volts).
Bleed the power out of the caps with a big resistor (i use a 50 Watt 25Kohm type).
After doing this to all capacitors of the PS bank,REPEAT the procedure once more!
Your life is worth the extra care!
Also be carefull when taking out old caps:it's easier than you think to strip a trace on the board!
Have fun!
While there is no danger in the range we are talking about, increasing cap size too much might damage things upstream. Reason is that a cap resists changes in its output. This is good from the point of view of it powering what is downstream from it: the amp. It is not so good from the device feeding the cap which now on power up, sees more resistance from the cap as it attempts to ramp up its voltage from zero to operating voltage. I have indeed damaged parts leading to the cap on start-up.
Again, adding 10 to 20% is likely to be OK but don't go overboard without understanding the full circuit and its power limitations.
Again, adding 10 to 20% is likely to be OK but don't go overboard without understanding the full circuit and its power limitations.
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