Hi everybody,
I have to choose four big power supply capacitors for my amplifier restoration project.
The amp in question is KA-907, Kenwood's TOTL model from 1979.
On this photo you can see the original capacitors:
.
Only capacitors that are of the right size (that can be physically fitted inside the amp) and that are available to me (I live in Europe), are these Panasonics:
.
Are they OK for this kind of use?
I hope so, since I couldn't find any others that are small enough to be fitted inside the amp.
I'm not sure which ones should I get.
Some people advised me to go for the capacitors with the largest capacitance that can be physically fitted inside the amp (in this case - 33.000 uF, part no. ECEP1KP333HA).
Others told me that I should stick with the original capacitance.
Some told me that I should go for the 80 degree C, others said go for the 100 degree C ... 80V or 100V?
Who should I listen to and why?
I'm kind of a newbie, so little theory wouldn't hurt.
Please tell me what capacitors would you choose from those lists above.
You can use part numbers.
Thanks in advance,
Aleksandar
I'm so sorry for waisting bandwidth, but I also posted the same question in other section of this site, in hope that more people will see it.
I really need to make this decision as soon as possible (while those capacitors are still in stock).
PS
In case this is important, here is also a scan from the service manual, showing the power supply and power amp sections:
http://www.kujucev.com/kx/_amp_web.jpg
I have to choose four big power supply capacitors for my amplifier restoration project.
The amp in question is KA-907, Kenwood's TOTL model from 1979.
On this photo you can see the original capacitors:
An externally hosted image should be here but it was not working when we last tested it.
.
Only capacitors that are of the right size (that can be physically fitted inside the amp) and that are available to me (I live in Europe), are these Panasonics:
.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Are they OK for this kind of use?
I hope so, since I couldn't find any others that are small enough to be fitted inside the amp.
I'm not sure which ones should I get.
Some people advised me to go for the capacitors with the largest capacitance that can be physically fitted inside the amp (in this case - 33.000 uF, part no. ECEP1KP333HA).
Others told me that I should stick with the original capacitance.
Some told me that I should go for the 80 degree C, others said go for the 100 degree C ... 80V or 100V?
Who should I listen to and why?
I'm kind of a newbie, so little theory wouldn't hurt.
Please tell me what capacitors would you choose from those lists above.
You can use part numbers.
Thanks in advance,
Aleksandar
I'm so sorry for waisting bandwidth, but I also posted the same question in other section of this site, in hope that more people will see it.
I really need to make this decision as soon as possible (while those capacitors are still in stock).
PS
In case this is important, here is also a scan from the service manual, showing the power supply and power amp sections:
http://www.kujucev.com/kx/_amp_web.jpg
The 18000uf@80vdc should work just fine.If you have enough clearance the 22,000uf @ 80vdc would work as well.Those particular caps have 5-mounting pins you will probably have to snip off 3 of them to mount on your PC board.Pay close attention to the polarity. You may or may not notice any audio difference going from 18000 to 33000 with exception to low frequencys which I would think would benefit the additional power reserve.
105 degree would be better than 85
100 vdc would give you additional safety margin.
Obviously the the originals worked just fine probably for quite a while.The choice is up to you to spend a little extra for piece of mind.
Dave
After looking at schematic 80 vdc is plenty.
105 degree would be better than 85
100 vdc would give you additional safety margin.
Obviously the the originals worked just fine probably for quite a while.The choice is up to you to spend a little extra for piece of mind.
Dave
After looking at schematic 80 vdc is plenty.
1979 was a good year...
Xeaglekeeper sounds good to me! I'd place the largest caps I could inside the location you have and try hard to maintain or exceed the temperature rating and voltage rating to acheive long happy life.
While you are at it, you could shop around and pluck out a few more old electrolytics as well. I think I would like a look-see at the schematic first, then I would choose my battles. I'd look for a couple other opportunities while there, like ceramics and such.
Jah to the restoration!
Shawn.
Xeaglekeeper sounds good to me!
I'd place the largest caps I could inside the location you have and try hard to maintain or exceed the temperature rating and voltage rating to acheive long happy life.While you are at it, you could shop around and pluck out a few more old electrolytics as well. I think I would like a look-see at the schematic first, then I would choose my battles. I'd look for a couple other opportunities while there, like ceramics and such.
Jah to the restoration!
Shawn.
22kuF is just fine, any more then u need to worry about the Bridges and AC fuse...
The KA-907 is a great amp. I still have a KA-1100 and a KA-3300 both flagships after the 907.
Ofcourse upping the caps with lower ESR units like the Panasonics and you are making the rails much tighter than spec... one drawback is the SOAR of the current OP stage may factor the droop and hence be ok but now with lessor droop, you may be getting closer to the OP device limits than intended by the designer. I say this because Kenwood usually had low current hi volt supplies in their integrated's and made the OP stage perform accordingly. The simple solution is to use better OP devices to compensate.
I have had excellent results with replacing the OP devices with 2sd424 and 2sb554. Smoother sound, greater SOAR and reliability.
Availability is another issue.
Go one step ahead and use the MJ21195/96's and you have a bullet proof OP stage. These will be drop in subs, no tweaks needed. the originals are 120w devices and the MJ's are 250w with better gain.
The KA-907 is a great amp. I still have a KA-1100 and a KA-3300 both flagships after the 907.
Ofcourse upping the caps with lower ESR units like the Panasonics and you are making the rails much tighter than spec... one drawback is the SOAR of the current OP stage may factor the droop and hence be ok but now with lessor droop, you may be getting closer to the OP device limits than intended by the designer. I say this because Kenwood usually had low current hi volt supplies in their integrated's and made the OP stage perform accordingly. The simple solution is to use better OP devices to compensate.
I have had excellent results with replacing the OP devices with 2sd424 and 2sb554. Smoother sound, greater SOAR and reliability.
Availability is another issue.
Go one step ahead and use the MJ21195/96's and you have a bullet proof OP stage. These will be drop in subs, no tweaks needed. the originals are 120w devices and the MJ's are 250w with better gain.
I recently recapped my Pioneer SX-1250 with some Nichicon KG Super series capacitors. You can also look into the Nichicon KG Gold series (these will probably fit into the amp). Very nice capacitors and of the utmost quality.
I would stick with the original cap values because that is what the engineers at Kenwood designed the amp for.
I would stick with the original cap values because that is what the engineers at Kenwood designed the amp for.
First of all are the power supply capacitors bad? If they aren't bad why replace them? I have some old equipment that has the original power supply caps and still works flawlessly.
Secondly I do NOT agree with gross oversizing the power supply caps because this causes undo stress on the rectifiers and usually means you will need to design a soft start circuit in order to have your diodes survive the turn on cycle. Adding larger sized caps makes the bass response sound very muddy unless you add bypass caps of the correct size.
If your bent on replacing the power supply caps I would suggest caps of roughly the same size and naturally caps that will work within the pyhsical limitations of the chassis. There are tweeks that will make ANY amplifier sound better. An example of one would be to bypass any electrolytics in the signal path with a small mica or mylar cap. Another tweek would be to add bypass caps to the power supply caps. These two tweeks will add far more to the sonic clarity and overall sound than you will ever get from putting huge power supply caps in.
Shawn,
The bypassing of the caps in the signal path and in the power supply works on Crown amps also. I can remember doing this on an Ampzilla that I owned. I did the bypasses on one channel and left the other channel bone stock and then had some people listen to it and watch their faces drop in amazement. I asked which channel sounded clearer and cleaner and it was a no brainer.
Secondly I do NOT agree with gross oversizing the power supply caps because this causes undo stress on the rectifiers and usually means you will need to design a soft start circuit in order to have your diodes survive the turn on cycle. Adding larger sized caps makes the bass response sound very muddy unless you add bypass caps of the correct size.
If your bent on replacing the power supply caps I would suggest caps of roughly the same size and naturally caps that will work within the pyhsical limitations of the chassis. There are tweeks that will make ANY amplifier sound better. An example of one would be to bypass any electrolytics in the signal path with a small mica or mylar cap. Another tweek would be to add bypass caps to the power supply caps. These two tweeks will add far more to the sonic clarity and overall sound than you will ever get from putting huge power supply caps in.
Shawn,
The bypassing of the caps in the signal path and in the power supply works on Crown amps also. I can remember doing this on an Ampzilla that I owned. I did the bypasses on one channel and left the other channel bone stock and then had some people listen to it and watch their faces drop in amazement. I asked which channel sounded clearer and cleaner and it was a no brainer.
burnedfingers said:
The guy is asking the question on diyaudio.com not mycapsareflawless.com
He wants to tinker... Let him do so within reason... Caps do age... right? The amp's close to 30 yrs old... !! Is there a chance that the caps are not steller? It's an easy upgrade... within reason not an issue yes? Thats why he is asking the collective wisdom.
burnedfingers said:
Amen to this... try different caps to see what suits you. Avoid tantalums...
K-amps is right,after 30 years these caps should have been replaced atleast twice.But burnedfingers is also right,use caps as much close to the originals as possible.Changing caps only with larger values,will surely make the bass muddy,thick,and slow.Also,because of this bass problem your mids and highs will suffer too.Caps only do not make a good power supply.Try also to replace all electrolytics if possible,and by all means,do bypass psu electrolytics with good polypropylene ones.
burnedfingers said:
Stating a large "generalization" for me: I have added massive amounts of farads to shrimpy old power supplies to wonderful results and never have I tasked a rectifier beyond any of its capability.
In the past year or so I have studied many schematics and builders methods. I am a firm believer that capacitance should be distributed more than just from the main power supply bank and that local "farads" are beneficial when they are brought close to the output devices that tax them so much. I.e. placing an additional ~1,000uF, bypassed near or next to the output devices. In some amplifier builds the power supply caps can make a distance 10~15cm of wire length by the time DC reaches the output transistors! This is a reality and I believe it requires compensation for best results.
I will also go out on a limb by asking readers to review
THIS thread. I believe the topic is covered well here.
These are my assumptions and I hope some day to have data to further support my current belief.
Subjective listening, to me comes second to the oscilloscope. I hate to say never but I would bet this view of mine will never change. Bigger power supply caps have bigger storage capacity and if this capacity is properly delivered to the demand then the results should be wonderful for all ears.
Furthermore, over sizing transformers will allow a specific design to draw more power with less sag in +/_ rails.
Power supply caps are there to filter and support current demand. Go big or go home! Cheers,
Shawn.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.