Hi Mike,
People are getting confused about the job these caps perform. These are not passing audio, and the voltage across these is essentially constant. Ceramic caps are the best component for the job. The Wima caps won't explode or cause horrible sounds, they just won't work as well. This probably will not make as big a difference as to agonize over. So, whatever ....
This project keeps getting pushed to a no holds barred experience, rather than a nice tune up with some lessons learned. The super amp would then follow with improvements that can be retrofitted to this one if desired. In any case, this would have given you a working amp at all times to listen to as you play with the other. Oh well.
-Chris
People are getting confused about the job these caps perform. These are not passing audio, and the voltage across these is essentially constant. Ceramic caps are the best component for the job. The Wima caps won't explode or cause horrible sounds, they just won't work as well. This probably will not make as big a difference as to agonize over. So, whatever ....
This project keeps getting pushed to a no holds barred experience, rather than a nice tune up with some lessons learned. The super amp would then follow with improvements that can be retrofitted to this one if desired. In any case, this would have given you a working amp at all times to listen to as you play with the other. Oh well.
-Chris
Mike,
Not everyone bypasses their op-amps with film caps. I used electrolytics on my LM3886 and wouldn't do it differently next time. All I would change is to use Rubycon ZA instead of the inferior ZL range.... right on the pins.
Simon
Not everyone bypasses their op-amps with film caps. I used electrolytics on my LM3886 and wouldn't do it differently next time. All I would change is to use Rubycon ZA instead of the inferior ZL range.... right on the pins.
Simon
Yes Chris but I never do anything light hartedly, you know me by now.
I wanted to know if soldering caps direct to the chips pins was viable and if so which cap to use. It turns out that yes its woth it and its do-able but with a link wire to the supply ground rather than direct to the chips ground. Im settled on this now.
There always a contientious 'fight' between the audiophile and the audioengineer. Both have different viewpoints. I believe this is why I have seen the wimmas used for bypass rather than the apparently more suitable Ceramics on DIY amps using the LM3886. I havent seen any with ceramics. Likewise I have noticed alot of PSU caps bypassed with a small value poly rather than a ceramic.
Lets areee to disagree. I'll experiment with both to see for myself which is best if any.
As usual I really appreciate your input. Its great for me - from a novice point of view - to have someone as knowledgeable as yourself contributing to my project. And yes, this is nice tune up with some lessons learned project. Im not planning anything too extreme but I want to ensure I maximise the benefeits of any mods I carry out.
As it stands I plan to definately do the following:
(Power amp)
- Change Diodes to MUR080's (forgot the exact part no)
- Change main PSU caps to Mundorf M-lytic 10'000uF 50v.
- Change local decoupling on power chip to BG STD 100uF 50v.
(the above are definates and I allready have the components)
- Bypass output traces, switch and realy with good OFC wire. (shorter signal path and less joints contacts)
- Link out DC blocking cap on input
(Preamp)
- 1000uF Pana FC on reg input
- RC filter network before +5v reg (processor supply)
- Tone circuit bypass and trace shortening.
- Removal of signal path DC blocking caps, I'll remove 1 at a time checking DC offset at the output. Hoping I can get it down to just 1 per channel.
And considering:
(Poweramp)
- Add 0.01uF bypass direct on chips pins. Ceramics or wimma polyprops.
- Change FB resistor to 12k (less gain). Possibly a nice Caddock of Vishay. (need to look into this more).
- Change feedback cap. So far in my research I have chosen 100uF Elna Silmic or 47uf wimma polypropylene. Also have 100uF Tants and Ruby ZLH to play with.
- Possibly use better resistors in the rest of the circuit.
(Preamp)
- Change feedback caps on opamp to Silver Mica or Polystyrene.
- Upgrade to better esistors around opamp.
- Possibly RC filter network before +/- regs. I will try this and decide accordingly after I have listened to results.
- Diconnet unwanted areas of the circuit (tone circuit, phonostage) from supply.
If the above makes a considerable difference positively I will change the volume pot to an Alps blue and bypass the tone pot.
Mike.
I wanted to know if soldering caps direct to the chips pins was viable and if so which cap to use. It turns out that yes its woth it and its do-able but with a link wire to the supply ground rather than direct to the chips ground. Im settled on this now.
There always a contientious 'fight' between the audiophile and the audioengineer. Both have different viewpoints. I believe this is why I have seen the wimmas used for bypass rather than the apparently more suitable Ceramics on DIY amps using the LM3886. I havent seen any with ceramics. Likewise I have noticed alot of PSU caps bypassed with a small value poly rather than a ceramic.
Lets areee to disagree. I'll experiment with both to see for myself which is best if any.
As usual I really appreciate your input. Its great for me - from a novice point of view - to have someone as knowledgeable as yourself contributing to my project. And yes, this is nice tune up with some lessons learned project. Im not planning anything too extreme but I want to ensure I maximise the benefeits of any mods I carry out.
As it stands I plan to definately do the following:
(Power amp)
- Change Diodes to MUR080's (forgot the exact part no)
- Change main PSU caps to Mundorf M-lytic 10'000uF 50v.
- Change local decoupling on power chip to BG STD 100uF 50v.
(the above are definates and I allready have the components)
- Bypass output traces, switch and realy with good OFC wire. (shorter signal path and less joints contacts)
- Link out DC blocking cap on input
(Preamp)
- 1000uF Pana FC on reg input
- RC filter network before +5v reg (processor supply)
- Tone circuit bypass and trace shortening.
- Removal of signal path DC blocking caps, I'll remove 1 at a time checking DC offset at the output. Hoping I can get it down to just 1 per channel.
And considering:
(Poweramp)
- Add 0.01uF bypass direct on chips pins. Ceramics or wimma polyprops.
- Change FB resistor to 12k (less gain). Possibly a nice Caddock of Vishay. (need to look into this more).
- Change feedback cap. So far in my research I have chosen 100uF Elna Silmic or 47uf wimma polypropylene. Also have 100uF Tants and Ruby ZLH to play with.
- Possibly use better resistors in the rest of the circuit.
(Preamp)
- Change feedback caps on opamp to Silver Mica or Polystyrene.
- Upgrade to better esistors around opamp.
- Possibly RC filter network before +/- regs. I will try this and decide accordingly after I have listened to results.
- Diconnet unwanted areas of the circuit (tone circuit, phonostage) from supply.
If the above makes a considerable difference positively I will change the volume pot to an Alps blue and bypass the tone pot.
Mike.
SimontY said:
True, I was referring to unmodded commercial hi-fi. And it was a generalized statement, sorry. I use 10uF BG STD on the LM4562 in my CDP. Initally I wanted to use a small value BG N 50v for the power chip bypass. No-one said it was good or bad so I decided against it, though I still fancy the idea.
Mike.
It's still likely to sound best (small BG). I didn't want to say because I don't feel like arguing with people who know better.
Hehe, I've never changed diodes and heard a massive improvement personally 😉
But I did change all the rectifier diodes in a Roksan Caspian amp once and it made the sound very clean and bright and snappy!! It wasn't quite what I was hoping for but it was interesting at least.
Simon
But I did change all the rectifier diodes in a Roksan Caspian amp once and it made the sound very clean and bright and snappy!! It wasn't quite what I was hoping for but it was interesting at least.
Simon
Ted205 said:
The Diodes I got are MUR860. I chose them because they seem the most common for chipamps using LM3886. Initially I was going for Hexfreds but apparently theyre no good for audio? 😉
I still fancy the BG n's despite all the above posts.
Hi Mike,
Any engineer who designs something without listening to it, is not an engineer. I have not met a single audio engineer that designs with instruments only. There are a few people who think that they are engineers who might do this, but I can't think of any off hand. Every single company I know of uses a listening room as part of the design process.
The problem begins where you have people who consider themselves designers and engineers who can not afford the equipment, or are too cheap to invest in equipment in order to test what they are working on. This is very much like attempting to drive with a covered windshield. Anyway, the popular excuse is one of the following:
1. I can hear the difference, and that is all that matters.
2. Things that test well, sound bad.
3. The problem with engineers is that they never listen to their designs.
.... and lastly, my absolute favorite ...
4. When I did "whatever", it sounded like a veil was lifted from the music.
The reality is that humans are often wrong when it comes to identifying distortion. If you become accustomed to the way something sounds, you will prefer that sound. It becomes real to you. Most testing is carried out in a manner that is not reproducible either. For instance, a dummy load does not represent a realistic speaker load. Well, sure. It doesn't and we all know it doesn't. But it is a reproducible standard that others can recreate. You can even add inductance or capacitance to get closer to real behavior, but there is no current standard for this that I know of right now. What this does do is provide a method where you can measure whether your design changes are getting better, or worse.
Some things that test well may sound bad - true. However, if something tests "bad", it will probably sound bad. The problem with testing "bad" is that it isn't well defined and certain factors need to be nailed down in addition to a THD number only. So, not enough information possibly.
I've had the opportunity (?) to work on several things that where "designed by ear" and "voiced". These designs almost always turn out to be unreliable and the "voicing" simply means they change the character of the distortion. In every case, the perceived sound quality and reliability was improved by redesigning the unit to increase circuit stability and follow good engineering guidelines. Listening to the item is part of the design process.
There really is not design vs listen camp. There is more a design correctly vs mess around type thing, and it's the mess around crowd that is constantly arguing. The design correctly people just do their thing quietly.
Would anyone attempt to design a car or airplane without an understanding of the parts? Even nuts and bolts come in different materials, coatings and designs. What normally happens is that people use parts recommended with zero clue as to their actual properties. It's a good thing that most parts will not fail and will sound okay when used for an application they are not well suited for. That is what keeps most tweakers going.
I'm not upset here, I am disappointed that with all the information here, these myths prevail. I was hoping to show you the opportunities to learn for real here Mike. Learning is easy if you only put out a little effort and do some objective thinking. Learn about what you are doing and why things work the way they do.
-Chris
Actually, that is not true at all. It's so far from the truth that it scares me how entrenched these myths have become.
Any engineer who designs something without listening to it, is not an engineer. I have not met a single audio engineer that designs with instruments only. There are a few people who think that they are engineers who might do this, but I can't think of any off hand. Every single company I know of uses a listening room as part of the design process.
The problem begins where you have people who consider themselves designers and engineers who can not afford the equipment, or are too cheap to invest in equipment in order to test what they are working on. This is very much like attempting to drive with a covered windshield. Anyway, the popular excuse is one of the following:
1. I can hear the difference, and that is all that matters.
2. Things that test well, sound bad.
3. The problem with engineers is that they never listen to their designs.
.... and lastly, my absolute favorite ...
4. When I did "whatever", it sounded like a veil was lifted from the music.
The reality is that humans are often wrong when it comes to identifying distortion. If you become accustomed to the way something sounds, you will prefer that sound. It becomes real to you. Most testing is carried out in a manner that is not reproducible either. For instance, a dummy load does not represent a realistic speaker load. Well, sure. It doesn't and we all know it doesn't. But it is a reproducible standard that others can recreate. You can even add inductance or capacitance to get closer to real behavior, but there is no current standard for this that I know of right now. What this does do is provide a method where you can measure whether your design changes are getting better, or worse.
Some things that test well may sound bad - true. However, if something tests "bad", it will probably sound bad. The problem with testing "bad" is that it isn't well defined and certain factors need to be nailed down in addition to a THD number only. So, not enough information possibly.
I've had the opportunity (?) to work on several things that where "designed by ear" and "voiced". These designs almost always turn out to be unreliable and the "voicing" simply means they change the character of the distortion. In every case, the perceived sound quality and reliability was improved by redesigning the unit to increase circuit stability and follow good engineering guidelines. Listening to the item is part of the design process.
There really is not design vs listen camp. There is more a design correctly vs mess around type thing, and it's the mess around crowd that is constantly arguing. The design correctly people just do their thing quietly.
Would anyone attempt to design a car or airplane without an understanding of the parts? Even nuts and bolts come in different materials, coatings and designs. What normally happens is that people use parts recommended with zero clue as to their actual properties. It's a good thing that most parts will not fail and will sound okay when used for an application they are not well suited for. That is what keeps most tweakers going.
I'm not upset here, I am disappointed that with all the information here, these myths prevail. I was hoping to show you the opportunities to learn for real here Mike. Learning is easy if you only put out a little effort and do some objective thinking. Learn about what you are doing and why things work the way they do.
-Chris
mikesnowdon said:
Hi,
No.
It's pretty much the optimum value. It's part of the Zobel and it stops the amp from oscillating with an inductive load. I has no effect on SQ.
Thanks.
Ive been looking at the earlier photo Stream posted (post:100). It shows 2 additional Ceramic caps near the FB resistors, C72,73. It was suggested earlier that they could be decoupling bypass caps. To me they dont look like theyre in the right place for that unless the PCB traces are drastically different from the service manual. They seem to paralel the FB resistors and the resistor to ground off the FB loop.
I'll try and take a look this weekend to see whats going on down under. I'll post some pics.
Any ideas what they could be for?
Mike.
Ive been looking at the earlier photo Stream posted (post:100). It shows 2 additional Ceramic caps near the FB resistors, C72,73. It was suggested earlier that they could be decoupling bypass caps. To me they dont look like theyre in the right place for that unless the PCB traces are drastically different from the service manual. They seem to paralel the FB resistors and the resistor to ground off the FB loop.
I'll try and take a look this weekend to see whats going on down under. I'll post some pics.
Any ideas what they could be for?
Mike.
Hi Jaycee.
How do you know that and what is its purpose? Im thinking its to filter out HF maybe?
Cheers!
Mike.
How do you know that and what is its purpose? Im thinking its to filter out HF maybe?
Cheers!
Mike.
Hi Mike,
Jaycee is very experienced with amplifier designs.
I can't tell for sure what these capacitors are connected to, but their value and proximity to the feedback resistors does suggest high frequency compensation. Could be the layout required them, could be the choice of output transistors.
Notice that they are NP0 / C0G types from the black strip on top. That means that the capacitance is pretty stable under temperature changes. I guess they don't want the value shifting.
Consider the value - 10 pF (or pico-farad). These capacitors will appear as an open circuit to audio unless you are dealing with very high impedances. That means that they are only there to affect high frequencies. RF pickup -yes, but more so internally generated noise which may have regenerative gain, or oscillation.
When you see things like this, don't mess with them. Notice that they are ceramic capacitors.
-Chris
Jaycee is very experienced with amplifier designs.
I can't tell for sure what these capacitors are connected to, but their value and proximity to the feedback resistors does suggest high frequency compensation. Could be the layout required them, could be the choice of output transistors.
Notice that they are NP0 / C0G types from the black strip on top. That means that the capacitance is pretty stable under temperature changes. I guess they don't want the value shifting.
Consider the value - 10 pF (or pico-farad). These capacitors will appear as an open circuit to audio unless you are dealing with very high impedances. That means that they are only there to affect high frequencies. RF pickup -yes, but more so internally generated noise which may have regenerative gain, or oscillation.
When you see things like this, don't mess with them. Notice that they are ceramic capacitors.
-Chris
Hi Chris.
I dont doubt Jaycee's expertise, I just wanted more info. My message probably reads wrongly. Sorry Jaycee. 🙂
Thanks for the explanation on those caps, I was curious on their purpose more than anything. So they are for HF filtering, I'll leave them alone.
I've asked CA for a '340A-SE' service manual as I want to study the areas of the circuit not shown in my 'non-se' manual. The thing Im most interested in is the i-pod connection. There is a front panel jack input which activates a relay when you insert a plug. When doing so the input switches to 'AUX'. I assume it also swithces in the second buffer opamp (below the top one) but Im not sure why? (I thought this was a phono stage!🙁 ) Now - for example - I was using the rear panel 'AUX' phonos for a DVD player, when I plug in an i-pod I'd assume the rear phono is switched 'out'. Otherwise there would be 2 inputs running simultaniously. Im thinking about re-jigging this for the CDP input so while using the CDP the signal isnt passing the selector ic. The realy would be activated by the 'direct' switch. Do you get the idea? It seems easily do-able and the relay is close to the rear panel so the signal path wont be extended considerably. I need that manual though so I can see whats going on.
Mike.🙂
I dont doubt Jaycee's expertise, I just wanted more info. My message probably reads wrongly. Sorry Jaycee. 🙂
Thanks for the explanation on those caps, I was curious on their purpose more than anything. So they are for HF filtering, I'll leave them alone.
I've asked CA for a '340A-SE' service manual as I want to study the areas of the circuit not shown in my 'non-se' manual. The thing Im most interested in is the i-pod connection. There is a front panel jack input which activates a relay when you insert a plug. When doing so the input switches to 'AUX'. I assume it also swithces in the second buffer opamp (below the top one) but Im not sure why? (I thought this was a phono stage!🙁 ) Now - for example - I was using the rear panel 'AUX' phonos for a DVD player, when I plug in an i-pod I'd assume the rear phono is switched 'out'. Otherwise there would be 2 inputs running simultaniously. Im thinking about re-jigging this for the CDP input so while using the CDP the signal isnt passing the selector ic. The realy would be activated by the 'direct' switch. Do you get the idea? It seems easily do-able and the relay is close to the rear panel so the signal path wont be extended considerably. I need that manual though so I can see whats going on.
Mike.🙂
I now have a 340A 'SE' service manual. 🙂
Those 2 ceramic caps are shown. One is across the feedback resistors, the other links the +/- supply inputs.
Mike.
Those 2 ceramic caps are shown. One is across the feedback resistors, the other links the +/- supply inputs.
Mike.
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