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DQ828  
#61 Posted : Monday, April 22, 2013 11:11:47 AM(UTC)
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Originally Posted by: luisbock Go to Quoted Post
Hi
I dont have a scope. Can the ripple problem be present with Placid HD, stock trannies and Buffalo 3 Standard build? Are there any diferent issues in avr300 setup to the present Buffalo 3 (non SE) build advice?
Regards


Yes, see post 46,47 & 48.

I don't have a scope either, I'm just modding on trust :)

Edited by user Monday, April 22, 2013 11:13:52 AM(UTC)  | Reason: Not specified

avr300  
#62 Posted : Monday, April 22, 2013 5:03:22 PM(UTC)
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Originally Posted by: fred_com Go to Quoted Post
Hi guys,

one note about this mod - when modding negative side of Placid HD BP polarities of electrolytic caps should be reversed (C2, C3 and the new one).
If polarity is not reversed - the negative side voltage will sag.

I don't know how this works, but I'm sure Russ will clarify this :)

Thanks,
Fedor


Always pay attention to polarity by using your DMM. But you're 100% right.
gbato  
#63 Posted : Wednesday, April 24, 2013 6:39:37 AM(UTC)
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Thanks to avr300, Russ and all you other guys for posting and making the mod possible. Here's my "anti-ripple-mod" of the Placid HD 1.0, using slightly different pads on the PCB to get room for it all (TP_GND2 is handy) - in case someone might find it useful.

Placid HD 1.0 "anti-ripple-mod"

Caps are 1xNichicon FG 1000uF/35V and 2xElna Silmic 100uF/35V.

Next up is Placid HD BP 1.0.

Edited by user Wednesday, April 24, 2013 6:43:59 AM(UTC)  | Reason: Not specified

luisbock  
#64 Posted : Sunday, April 28, 2013 3:52:56 PM(UTC)
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Originally Posted by: DQ828 Go to Quoted Post
Originally Posted by: luisbock Go to Quoted Post
Hi
I dont have a scope. Can the ripple problem be present with Placid HD, stock trannies and Buffalo 3 Standard build? Are there any diferent issues in avr300 setup to the present Buffalo 3 (non SE) build advice?
Regards


Yes, see post 46,47 & 48.

I don't have a scope either, I'm just modding on trust :)


Thanks DQ828
Does it mean we all have to do this mod for a clean PS?
Regards
Russ White  
#65 Posted : Sunday, April 28, 2013 5:29:56 PM(UTC)
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I have already stated - no you do not. It is completely optional, and in fact there are cases where it may not be desirable.

All this mod does is give better PSRR at the expense of a slower start up time because of the large time constant.

If you size the transformer and the reservoir caps appropriately for your load, the ripple will not be large enough to bother with.

The mod is completely optional - that said I think its a good one for many cases (and that's why I showed how to do it).

As with anything there is a trade off, that is the slow ramp up time, which in some applications will not be desirable.

As with anything DIY - it just depends on what is important in your particular case. :)

Also it just shows there is almost always more than one solution to any given challenge.

Cheers!
Russ
avr300  
#66 Posted : Sunday, April 28, 2013 5:33:48 PM(UTC)
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Who's all ? ;-)

It's completely optional, although I recommend it.

Regarding the placement of the C2-C3 your can just swap the onboard 220nF for the upgraded once, no need to place them under the board.

Oh yes, I upgraded the main caps as well.

Remember, it's DIY. ;-)
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musicman  
#67 Posted : Monday, April 29, 2013 7:15:18 PM(UTC)
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Are you willing to share the specs on your upgraded caps avr300 ?
musicman  
#68 Posted : Monday, April 29, 2013 7:16:33 PM(UTC)
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The four small ones in front of the 33000uf.
avr300  
#69 Posted : Monday, April 29, 2013 7:37:15 PM(UTC)
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Yes certainly, my pleasure.

Panasonic FM 470u, 16v.

You know, what ever comes handy (at the end of your fingertips) one uses.
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Corpius  
#70 Posted : Monday, April 29, 2013 7:54:43 PM(UTC)
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How much longer does it take before the desired voltage is reached? Is there a way of calculating it. Maybe the same way as when calutaling the RC time constant of a resistor–capacitor circuit?,

I'm asking this, because I'm worried when I do the mod the time it takes to start the DAC becomes a bit too long for my I2C controller. My controller starts first and swithes a relay to power the DAC. It waits for 50 ms after the relay is switched, than it starts programming the DAC. I'm not sure what will happen if the start time is longer as 50ms . I can always increase the delay of course, but I still need to now by how much. I don't want full volume blasting through my speakers when the delay is too long Eh?

I'm also wondering how useful this mod is for the Buffalo, because it already has low noise regs for all important parts of the chip. I my opinion the mod has more influence on the analoge parts, such as the IV stage. Not trying to say here that the mod is not useful for the Bufallo, but just sharing my thoughts :)
avr300  
#71 Posted : Monday, April 29, 2013 8:03:14 PM(UTC)
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I'll fancy - "the less noise you put in the less noise you'll get out"

But it up to you.

Yes, you could calculate the start up time, or you can measure it. Perhaps using 470u instead of 220n is "going over the top" - but that was what I had at time of presence.

With the components I use it's roughly 2 sec.
Corpius  
#72 Posted : Monday, April 29, 2013 8:58:54 PM(UTC)
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Originally Posted by: avr300 Go to Quoted Post
But it up to you.
I'm very tempted. I think that I will give it a try soon, but I will use some smaller values instead to keep the delay as short as possible. :)

Edited by user Monday, April 29, 2013 9:00:15 PM(UTC)  | Reason: Not specified

musicman  
#73 Posted : Tuesday, April 30, 2013 8:24:44 AM(UTC)
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avr300 ; is it just to go for Phanasonic 470u without change anything else ? Something I will need to adjust?
luisbock  
#74 Posted : Tuesday, April 30, 2013 10:40:18 AM(UTC)
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Originally Posted by: Russ White Go to Quoted Post
I have already stated - no you do not. It is completely optional, and in fact there are cases where it may not be desirable.

All this mod does is give better PSRR at the expense of a slower start up time because of the large time constant.

If you size the transformer and the reservoir caps appropriately for your load, the ripple will not be large enough to bother with.

The mod is completely optional - that said I think its a good one for many cases (and that's why I showed how to do it).

As with anything there is a trade off, that is the slow ramp up time, which in some applications will not be desirable.

As with anything DIY - it just depends on what is important in your particular case. :)

Also it just shows there is almost always more than one solution to any given challenge.

Cheers!
Russ


Thank you Russ, you made the issue cristal clear. I am just looking for wise solutions, just got a little confused with the thread direction.
Best regards
avr300  
#75 Posted : Tuesday, April 30, 2013 4:43:39 PM(UTC)
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Originally Posted by: musicman Go to Quoted Post
avr300 ; is it just to go for Phanasonic 470u without change anything else ? Something I will need to adjust?


Don't forget the decoupling of the error amplifier, the resistor / cap mod mentioned earlier in this threat. It's at least important as the C2/C3 upgrade.

Always check the output voltage and shunt current after a mod.
musicman  
#76 Posted : Tuesday, April 30, 2013 9:38:22 PM(UTC)
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Thx
fred_com  
#77 Posted : Wednesday, July 31, 2013 10:29:58 AM(UTC)
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Hi guys,

After applying this mod everything was fine, but then I've decided to upgrade filter caps as well - to 22000uF, and now I have a problem with Placid HD BP which is powering a Legato 3 with buffers - sometimes on turn on the output voltage is 1.62v instead of 15v and QN1 gets really hot. After several power cycles it starts normally.

Mod config - C2, C3 - 47uF, additional cap is 220uF, resistor is 220 Ohm.

Could it be because C2 and C3 capacitance is too high? Or is it strictly because of beefier filter caps? But others seem to use even more capacitance with no ill effects.

P.S. Large capacitance on C2, C3 is actually not desired (as Russ already said) for some controllers, and I've learned it myself, when powering certain USB-I2S controller based on XMOS chip.

P.P.S. Btw, I've measured output with oscilloscope with just larger filter caps, but without this mod - ripple was still there.

Thanks,
Fedor
avr300  
#78 Posted : Wednesday, July 31, 2013 10:42:14 AM(UTC)
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Here I have seen the same. Not only after upgrading the main caps from 10kuf to 33kuf but also before with the stock caps.

Try beefing up the tranny. With the 30VA stock the the powerup procedure was wobbly. Now, with a 120VA tranny, the _CLICK_ from the Legato mute relay is really authoritive, starts up 10 of 10 times. And the sound is much more present.

No matter what others think - the 30VA tranny seems to be a bottleneck.

Good luck.
fred_com  
#79 Posted : Wednesday, July 31, 2013 11:17:43 AM(UTC)
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Hi avr,

thanks for your quick reply.

Looks like new trafo is the way to go :)
Russ White  
#80 Posted : Wednesday, July 31, 2013 11:19:19 PM(UTC)
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Or just use two, one for each rail (with it's secondaries in parallel) :)
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