Poor sound after recap SAE 2300 power amp

elara

elara

Classic Rock and HI-FI
Hello friends,

please help me with your usefull opinions.

lately I replaced the cans capacitors in power supply with two new Epcos caps and every electrolytic on pre-drivers channels boards with new Nichicon Muse KZ caps. Besides, I replaced the rectifier bridge and almost every element (except one cap) on the relay Board of my SAE 2300 power amp.

Power amp recovered its bass punch but it now sounds pretty bad, every thing sounds undefined, mid and high frequencies sound muffled and muddy, without life at all.. Amp lost all its brightness.

What can be happening?, Any idea..?

Could be possible that Nichicon Muse KZ caps need some days for break in??

Could be possible that my power amp didn´t like the Nichicon Muse KZ caps??


Thanks in advanced and excuse my english.... :)
 
If it don't sound good now ,it won't sound any better in 100 hours.
 
Signal Trace

I would try signal tracing if you have the equipment listen to the various stages to find the loss in quality. Your description sounds like a major loss.
 
Are you sure you did not buy some fake cap?
If you are sure I believe it would be nice to do some measure comparison between old and new capacitors.
 
I bought a sansui ca-3000 which was recapped with Panasonic fc capacitors. Although the music was clear and transparent, something was missing and it sounded boring. I recapped it with Elna Silmics ii and a few Cerfaines. Without a doubt instantly turning the pre-amp on, the smooth silky sound I was hoping for was there. There was more bass as well. I've never dealt with nichicon muse before so can't comment. I would try some silmics ii in your sae 2300.
 
Either you are imagining it (most likely cause) or there might be a defective component or bad solder joint somewhere.

Calm down. Don't listen to music with unrealistic expectations or stress. That is what causes bad sound, not capacitors.
 
Check your input and output wiring, and wiring to the speakers. I think you have one of them wired out of phase. Usually the bass will go too, but the diffuse, undefined midrange is usually a dead giveaway that signal is out of phase or reverse polarity.
 
Hello again Friends,

Thanks a lot for yours comments. Here are some more...

Every cap and part I installed comes from Mouser so I believe they are not fake.

(Using a Fluke digital tester)
I measured capacitance for all new components before installing and they were ok., besides I measured every old capacitor and only one was out of tolerance.

I tested the power amp before and after repair using two different pre amps, two different speakers, different input and output cables, besides also I asked for a second opinion from listening to my quality control boss (my daughter) and I can ensure that this power amp today is sounding horrible. :-(

I have reviewed every thing I touched and I can see anything wrong.. It is hard to belive to me that Nichicon KZ may be a bad product.

Could be some "electronic incompatibility"?, in this case, why it happens?

I guess someone have installed Nichicon KZ in a SAE power before, but I could not find any reference. Any suggestions on how to search for that experience?

Thanks.
 
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Bad luck with your recap project, Elara. There are numerous possibilities: improper soldering, defective original capacitors, ESD damage to one or more capacitors during/after installation, improper selection of capacitors, polarity of capacitors is reversed, etc.

Please note the important comments by OPs regarding only buying from reputable retailers like DigiKey or Mouser, and "If it don't sound good now,it won't sound any better in 100 hours."

Despite all the hype, I don't rate Nichicon KZs. I used them once, didn't like the sound and replaced them with Elna Silmic IIs.

I don't know your skill level but here are a few basic suggestions. (OPs please correct me if I am wrong.)

- Good soldering skills are critical. There are good guides on the Net. Make sure you have the appropriate soldering iron (30 W + ), a good solder sucker and solder wick, 100% isopropyl alcohol for cleaning joints, good quality 60/40 rosin core solder (Ersin Multicore, Radio Shack, Hakko or Goot SE-56008). Avoid lead-free solder and exotic solder (98% silver, etc.). Practice a few joints on a blank PCB board until you are confident of your skills, because especially desoldering can lift PC board solder tabs and then – OMG!.

- Confirm the capacitors you are using comply with the SAE 2300 service manual parts list regarding capacitance, voltage, polarity and rated temperature. Note that many amplifiers, including one I recapped, use polarized caps on the power and preamp circuits and BP (bi-polar) caps on the driver circuit. (I used Nichicon ES BPs for my driver circuit and Nichicon PWs for everything else.)

- Use the capacitance recommended by SAE and same or next value higher voltage. Be aware that many Japanese capacitors are rated at 85 deg C (to suit Japanese appliances) whereas a 105 deg C rating seems more common for European and US amps.

- Be careful about ESD damaging your circuit boards, especially if they use IC chips. When working on the board with the large power condensers, first discharge the condensers for a few seconds with a 5 W / 10 W resistor across the terminals. Do the same for each new capacitor before soldering it to the PC board.

- Start by replacing the capacitors on the power supply board with Nichicon PWs. Power up the amp to confirm it's basically functioning OK. Then proceed with replacing the capacitors on the driver board with Nichicon ES BPs or Elna Silmic II polarized caps - depending on what the SAE service manual specifies.

- Here are some some URLs I found useful:

http://www.condoraudio.com/wp-conte...oose-Replacement-Capacitors-and-Resistors.pdf
http://www.head-fi.org/t/528380/electrolytic-capacitors-used-in-audio-dc-blocking-comparison-tread
http://gigapod.free.fr/re-cap.html


Best of luck!
 
Despite I am going to propose you something similar to snake oil ... triyng with by-pass capacitors can be easier than replacing big capacitors again.
Just a trial without a solid scientific base, but someone says that it works :D

Otherwise, if every channel has its own smoothing capacitors, you can try one channel with original capacitors and the other with the new ones, just to have a real comparison.
 
Last edited:
The first thing I'd want to do is check the amp with a sig gen and scope, just to be absolutely sure there isn't some error or performance problem that needs to be fixed. Since you did the whole thing it's even possible that the same error exists in both channels. If that test proves OK, then you have to start looking at the parts you changed in detail. Did you change values or voltage ratings from the originals? Did you re-bias the amp? It's unlikely, but possible, that different cap leakages moved the bias point of the amp. New caps will generally have higher leakage until they've been under voltage for some hours. It usually doesn't matter, but obviously something is amiss. How's the DC offset?
 
Did you change the caps with the same value as the originals. Going up or down in uF value can alter the sound.
Is this a DC amp? If yes, the caps shouldn't have an effect.
Conrad is correct. You need to 'scope' out the amp to find the 'problem.'
 
ftpols said:
Bad luck with your recap project, Elara. There are numerous possibilities: improper soldering, defective original capacitors, ESD damage to one or more capacitors during/after installation, improper selection of capacitors, polarity of capacitors is reversed, etc.

Please note the important comments by OPs regarding only buying from reputable retailers like DigiKey or Mouser, and "If it don't sound good now,it won't sound any better in 100 hours."

Despite all the hype, I don't rate Nichicon KZs. I used them once, didn't like the sound and replaced them with Elna Silmic IIs.

I don't know your skill level but here are a few basic suggestions. (OPs please correct me if I am wrong.)

- Good soldering skills are critical. There are good guides on the Net. Make sure you have the appropriate soldering iron (30 W + ), a good solder sucker and solder wick, 100% isopropyl alcohol for cleaning joints, good quality 60/40 rosin core solder (Ersin Multicore, Radio Shack, Hakko or Goot SE-56008). Avoid lead-free solder and exotic solder (98% silver, etc.). Practice a few joints on a blank PCB board until you are confident of your skills, because especially desoldering can lift PC board solder tabs and then – OMG!.

- Confirm the capacitors you are using comply with the SAE 2300 service manual parts list regarding capacitance, voltage, polarity and rated temperature. Note that many amplifiers, including one I recapped, use polarized caps on the power and preamp circuits and BP (bi-polar) caps on the driver circuit. (I used Nichicon ES BPs for my driver circuit and Nichicon PWs for everything else.)

- Use the capacitance recommended by SAE and same or next value higher voltage. Be aware that many Japanese capacitors are rated at 85 deg C (to suit Japanese appliances) whereas a 105 deg C rating seems more common for European and US amps.

- Be careful about ESD damaging your circuit boards, especially if they use IC chips. When working on the board with the large power condensers, first discharge the condensers for a few seconds with a 5 W / 10 W resistor across the terminals. Do the same for each new capacitor before soldering it to the PC board.

- Start by replacing the capacitors on the power supply board with Nichicon PWs. Power up the amp to confirm it's basically functioning OK. Then proceed with replacing the capacitors on the driver board with Nichicon ES BPs or Elna Silmic II polarized caps - depending on what the SAE service manual specifies.

- Here are some some URLs I found useful:

http://www.condoraudio.com/wp-conte...oose-Replacement-Capacitors-and-Resistors.pdf
http://www.head-fi.org/t/528380/electrolytic-capacitors-used-in-audio-dc-blocking-comparison-tread
http://gigapod.free.fr/re-cap.html


Best of luck!
Click to expand...
Agree with ftpols
Power Board: Nichicon PW or Panasonic FR(Lower ESR)
Driver Board: Nichicon ES(BiPolar) or Elna Silmic II(Polarized)

When I recapped my Sony STR-GX10 I had used for the Audio Path for Output Nichicon KZ...:no: After 100hrs the Sound was still Muddy. Switched then out with Elna Silmic II and :thmbsp:
 
If you don't have a scope, I agree with restoring one channel with original caps, check, and put new caps again one by one, listening after each replacement. I think the power supply should be fine. I'dpoint to the amp section first.
 
one more vote for "clearly something is wrong," as opposed to you just needing to try a different brand of caps or something like that.

this is pretty much a brief summary of the other responses, with my own experience thrown in:

if you have any caps inserted backwards, they'd likely blow within a few minutes. if that doesn't send the amp into protection, then you could have muddy sound like this, although you'd probably have heard the cap blow if you were around the amp or the music was playing. still, look for caps with the top seal shredded. if that's not it, a bad solder joint, an overheated part, or an ESD-damaged part are the likely culprits. the bad part could be tricky to find, but it's possible if you're patient! good luck...

EDIT: the other question i don't think you answered was whether you fully discharged the filter caps before working on the amp. some filter caps discharge slowly on their own, others don't, and in that case they can cause problems to transistors (especially FETs) if you're not careful.
 
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Did you make sure that you provided a ground for the new caps when you replaced the can cap, which used the can itself for ground?
 
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