I've added a 1.5uF ero mkt cap to each chipamp revision 3 board, from V+ to V-.
PSU is basic 220VA tranny, single MUR860 rectifier bridge, 1000uF pan FC per side per amp.
The sound seems to have lost a slight edginess but seems more focused and smoother.
Any once got any experience with a similar cap in this position? I seem to remember Carlos had a 3.3uF in his snubberized PSU setup?
PSU is basic 220VA tranny, single MUR860 rectifier bridge, 1000uF pan FC per side per amp.
The sound seems to have lost a slight edginess but seems more focused and smoother.
Any once got any experience with a similar cap in this position? I seem to remember Carlos had a 3.3uF in his snubberized PSU setup?
You are getting two 'hits' for the price of one.
You are coupling the + and - rails at HF effectively without involving the ground circuit.
If you place capacitors from + to ground and - to ground, then rail to rail you will have 1/2 the capacitance (two capacitors in series), running them from one rail to the other will give you the *full* capacitance between rails
Caps from the + to the - rail is an old Nelson Pass trick (yes, that Nelson Pass), its a PITA to calculate using PSU designer, but it works soooo well.
Owen
You are coupling the + and - rails at HF effectively without involving the ground circuit.
If you place capacitors from + to ground and - to ground, then rail to rail you will have 1/2 the capacitance (two capacitors in series), running them from one rail to the other will give you the *full* capacitance between rails
Caps from the + to the - rail is an old Nelson Pass trick (yes, that Nelson Pass), its a PITA to calculate using PSU designer, but it works soooo well.
Owen
I guess this explanation would be consistant with the improved smoothness without loss of transparency.
Thanks for the help Owen.
Should I be using small caps like the 1.5uF I have, or look at a bigger electrolytic? I'd try a big FM but all mine are 50V, so not up to the 54V from V+ to v-.
Is there a pass labs thread that explains more?
Thanks for the help Owen.
Should I be using small caps like the 1.5uF I have, or look at a bigger electrolytic? I'd try a big FM but all mine are 50V, so not up to the 54V from V+ to v-.
Is there a pass labs thread that explains more?
I'm being a bit spontaneous with my current amp as I have been buying bits for the next one and nd am keen to try out as many things as I can.
Anyway, I just added 4uf russian PIO caps in parallel with the 1.5uF eros. Seems like more of the same improvements! I'm loving this - I've been playing with these amps for months and it's cool to try something new that seems to work.....
I'd love to hear of other's experiences :-D
Must be one of the easist mods to try temporarily.... go on!
Anyway, I just added 4uf russian PIO caps in parallel with the 1.5uF eros. Seems like more of the same improvements! I'm loving this - I've been playing with these amps for months and it's cool to try something new that seems to work.....
I'd love to hear of other's experiences :-D
Must be one of the easist mods to try temporarily.... go on!
Hi,
I think part of the success you have found is down to using a plastic film cap across the supply.
Compare what you have done to the recommended scheme for bypassing an opamp. Many go +pin to -pin. Although a few recommend asymetric bypassing and some +pin to ground and -pin to ground. It seems to depend on how the internals of the amp are designed.
Your gainclone may well suit rail to rail decoupling.
Have you tried pin to pin bypassing by moving the film cap from PSU to gainclone pins?
I think part of the success you have found is down to using a plastic film cap across the supply.
Compare what you have done to the recommended scheme for bypassing an opamp. Many go +pin to -pin. Although a few recommend asymetric bypassing and some +pin to ground and -pin to ground. It seems to depend on how the internals of the amp are designed.
Your gainclone may well suit rail to rail decoupling.
Have you tried pin to pin bypassing by moving the film cap from PSU to gainclone pins?
That makes complete sense to me - best place for the cap (whatever size is optimal).
Unfortunately the base of the pcb is inaccesible - next time I build I'll do the work before final assembly.
Any suggestion for cap value? 5.5uF combo sounds better than 1.5uF, but since I don't know the maths It'll be trial and error for me...
Unfortunately the base of the pcb is inaccesible - next time I build I'll do the work before final assembly.
Any suggestion for cap value? 5.5uF combo sounds better than 1.5uF, but since I don't know the maths It'll be trial and error for me...
Hi,
I cannot advise on cap values nor on the ideal location of the bypassing and/or decoupling.
This is down to my biassed attitude towards chip power amps.
I am a discrete man to the grave.
I have heard how bad car radios/CD players, separate amps, cassette players etc sound when compared to in house stereo systems.
It is almost certainly down to using chipamps to save space, cost and development time (=cost).
I cannot advise on cap values nor on the ideal location of the bypassing and/or decoupling.
This is down to my biassed attitude towards chip power amps.
I am a discrete man to the grave.
I have heard how bad car radios/CD players, separate amps, cassette players etc sound when compared to in house stereo systems.
It is almost certainly down to using chipamps to save space, cost and development time (=cost).
Chipamps (like everything) aren't perfect. I like them a lot though.
We all have our own experience to lean on. For my part, I used to sell high end hifi etc. and believe that the gainlone is the best accessible high-end amp I've ever heard.
After I finish the next 'statement' gainclone, I want to try something like a first watt..... Already played with lots of low power class-d which is excellent for the portable kit I've built (sound quality:efficiency ratio is brilliant). A Nelson amp seems like the next project...
This mod works wonders for me though - my gainclone already bettered than the naim, classe, burmester, mf, myryad, linn, chord etc. I've used at home in the past.
Anyway, grander plans aside, TRY THIS IF YOU HAVE A GAINCLONE!!!
We all have our own experience to lean on. For my part, I used to sell high end hifi etc. and believe that the gainlone is the best accessible high-end amp I've ever heard.
After I finish the next 'statement' gainclone, I want to try something like a first watt..... Already played with lots of low power class-d which is excellent for the portable kit I've built (sound quality:efficiency ratio is brilliant). A Nelson amp seems like the next project...
This mod works wonders for me though - my gainclone already bettered than the naim, classe, burmester, mf, myryad, linn, chord etc. I've used at home in the past.
Anyway, grander plans aside, TRY THIS IF YOU HAVE A GAINCLONE!!!
Hi,
I would guess that the improvement could be down to attenuating very short duration spikes and/or glitches that get from the power end of the device through the supply to the input end of the device. (with a chipamp much of this route is buried inside the chip).
If the supply is contaminated then the output will be contaminated.
Improve the first and the second cannot get worse.
I cannot confirm this hypothesis since my test equipment and technique cannot approach the levels that need measuring.
I would guess that the improvement could be down to attenuating very short duration spikes and/or glitches that get from the power end of the device through the supply to the input end of the device. (with a chipamp much of this route is buried inside the chip).
If the supply is contaminated then the output will be contaminated.
Improve the first and the second cannot get worse.
I cannot confirm this hypothesis since my test equipment and technique cannot approach the levels that need measuring.
Pure speculation (please correct me if wrong):
There should be a constant voltage between V+ and V- that is equal to twice the voltage between either leg and ground. Under the dynamic load of an amp, this will drop at 'busy' times that test the psu.
Only one rail is used at any time to supply current, as the amp is either puting out positive or negative current relative to ground (as the signal fluctuates above and below zero). Never are both rails drained at the same time. In fact, whenever one rail is being drained, the other is recovering.
Could this additional cap help maintain the voltage accross V+ and V- by responding very quickly to drops in one side or the other? I guess the issue is whether the higher voltage between V+ and V- allows this cap to step in quicker than those between a voltage rail and ground.
Equally, I could see the cap helping with noise that was equal and opposite on the two voltage rails.
These are complete guesses so someone step up and educate me!
I'm still hearing improvements with a 1.5uF ero mkt in this position. The additional 4uF pio improved smoothness but killed dynamics - initially it sounded better but after a day I prefer the single ero.
There should be a constant voltage between V+ and V- that is equal to twice the voltage between either leg and ground. Under the dynamic load of an amp, this will drop at 'busy' times that test the psu.
Only one rail is used at any time to supply current, as the amp is either puting out positive or negative current relative to ground (as the signal fluctuates above and below zero). Never are both rails drained at the same time. In fact, whenever one rail is being drained, the other is recovering.
Could this additional cap help maintain the voltage accross V+ and V- by responding very quickly to drops in one side or the other? I guess the issue is whether the higher voltage between V+ and V- allows this cap to step in quicker than those between a voltage rail and ground.
Equally, I could see the cap helping with noise that was equal and opposite on the two voltage rails.
These are complete guesses so someone step up and educate me!
I'm still hearing improvements with a 1.5uF ero mkt in this position. The additional 4uF pio improved smoothness but killed dynamics - initially it sounded better but after a day I prefer the single ero.
Thanks for posting your experiments with a cap from V- to V+. I just had to try it with what i had on hand(a couple 4.7uf electrolytics in series) and I too am pleased with the result. The only way I can explain the sound is that it seems to have more space to it and snare drums really seem to sound good. Looking forward to trying some nicer film caps for fun when I place my next digikey order.
You can shoot me if I can find anything at this time of morning, but I'm pretty sure it was an article by the esteemed Mr Pass in which he claimed that due to the asymetrical nature of air... i.e. the driver has to do all the intintial pushing against the air on its own steam, and then gets some assitance on the way back due to the compression and viscosity of air, (Mr Nelson, if I got this wrong I do appologise)... anyhow, this is how the article explained that a PSU with a slightly stronger positive rail would in fact be benificial... I'm not sure if this is limited to discrete circuits, but I'm guess this would only apply only to non-inverted topologies...
Nelson did it to prove single ended nature of air pressure and therefore prove single ended amplifiers morally supreme.
1Pa of AC pressure is quite loud, while 'DC bias' of air pressure is around 100kPa.
Aside from philosophical issues, even Nelson's amps don't come close to such a high DC bias to AC signal ratio
1Pa of AC pressure is quite loud, while 'DC bias' of air pressure is around 100kPa.
Aside from philosophical issues, even Nelson's amps don't come close to such a high DC bias to AC signal ratio
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