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Old 4th August 2014, 06:30 PM   #11
sbelyo is offline sbelyo  United States
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Originally Posted by sbelyo View Post
Would a pair of opa627au on a browndog adapter work in place of IC5 (LM4562) ?
This is pin compatible on a brown dog adapter. Has anyone tried this?

Also it looks like I would have to parallel two caps for C1 - C4 to get 0.015 uf

Is there any drwaback to doing this other than having to make it fit?
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Old 4th August 2014, 06:58 PM   #12
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I have done some experiments with ivy
For me the sound was to sterille ,cold.
Some resistor changes that you suggest are good. I think i used Wishay.
Panasonic FM or FR are to cold-sounded for audio filtering. I use Nichicon KZ because midrange is more powerfull and energic.
I reduced filtercaps on 4,7n Styroflex capacitors
Lm4562 changed first for lme49720 metallcan... better but still some coldness in music to hear.
Best option was lme49990 with more than 100pf (100-200pf styroflex or silvermica) on feedback ( without cap lme49990 oscilated but lme49720 metalcan didn*t) and about 5-10mA AClass biasing ( think i used BF245Bor C selected for right biassing) . That is up to you what bias you will choose.
Thin was silver-gold Mundorf.
http://www.audio-kontakt.com/forum/v...391bd2d38e5e4a

This was middle version.
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Old 4th August 2014, 07:27 PM   #13
sbelyo is offline sbelyo  United States
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Thanks... someone suggested the LME49860 as well
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Old 4th August 2014, 07:44 PM   #14
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Lme49860 is +-22V lm4562 for me similar sound.
Lme49720 is better... 2X49990 on adapter is even better , low noise, more organic, highs are brillant, fine ...bas has more weight than lm4562 and lme49720.
opa627 is to soft for my taste in this configuration. Mycrodinamic and details are not so good as lme49720 or lme49990. Opa627 and lme49720 both need no compesation cap, but lme49990 does. Maybe all others have tried it without cap... then the IC oscilate and sound is wooly, shy, like a curtain over the speakers.
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Old 5th August 2014, 01:05 AM   #15
sbelyo is offline sbelyo  United States
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The compensation cap is C1 - C4 or am I wrong?
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Old 6th August 2014, 06:50 PM   #16
sbelyo is offline sbelyo  United States
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If I change the value of C1 - C4 to 8.2 nf what will the effect be?
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Old 6th August 2014, 07:28 PM   #17
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Changing C1-C4 lowers/highes high cutoff frecuency 8n2 from 55khz to 100khz. So the phase margin is not so deep in 20khz range
(Sample)RC Low-pass Filter Design Tool - Result -
Feedback cap i meant across resistor R22 and R24 (2,2kohm...) you add 100-220pf styroflex or silver mica cap when you use lme49990.
If you don*t have scope you better use lme49720 metallcan !!! not plastic case. Nichicon KZ or Silmic 2 -100uf capacitors plus 1uf mkp and 100nf mkp or pps on power supply decoupling.
I also changed opamp in AVCC regulator do some more filtering and give better decoupling on both other regulators..... clock regulator had huuge oscilations...measure and you willl see it...that oscillation even goes in both other regulators. By me supply for +5V was Salas shunt.
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Old 7th August 2014, 02:03 AM   #18
sbelyo is offline sbelyo  United States
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Originally Posted by androa76 View Post
Changing C1-C4 lowers/highes high cutoff frecuency 8n2 from 55khz to 100khz. So the phase margin is not so deep in 20khz range
(Sample)RC Low-pass Filter Design Tool - Result -
I see what you're talking about. Someone went down to 8.2nf and you went down to 4.7nf I'm just not sure if I should keep the stock value or lower it. I really want it to sound not as cold or forward on the high end. So I think I would want to lower the value of C1 - C4 correct?
Quote:
Originally Posted by androa76 View Post
Feedback cap i meant across resistor R22 and R24 (2,2kohm...) you add 100-220pf styroflex or silver mica cap when you use lme49990.
I should switch to a pair of LME49990 so I will add the feedback cap across R22 and R24
Quote:
Originally Posted by androa76 View Post
If you don*t have scope you better use lme49720 metallcan !!! not plastic case. Nichicon KZ or Silmic 2 -100uf capacitors plus 1uf mkp and 100nf mkp or pps on power supply decoupling.
I don't have a scope so I'll go with LME49990 and Silmic II caps
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Originally Posted by androa76 View Post
I also changed opamp in AVCC regulator do some more filtering and give better decoupling on both other regulators..... clock regulator had huuge oscilations...measure and you willl see it...that oscillation even goes in both other regulators. By me supply for +5V was Salas shunt.
I'll revisit this a little later on
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Old 8th August 2014, 04:04 AM   #19
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If you have current versions of Trident they are absolutely stable. Older versions can benefit from a comp cap on the error amplifier. AVCC is very stable - newer versions have improved error amplifiers.

As for "Warmer" sound, you could experiment with raising the output impedance. And possibly increasing the filter capacitors - this will shift the high end phase a bit and tend to accentuate the mid band.

The latest iteration of the Placid BP is a must have for either the IVY or the Legato. This last iteration has the benefit of exceptional user feedback which has influenced its final form. It has taken the supply to a new level in terms of low noise and low output impedance. The difference it makes in an output stage can be stunning.
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Old 8th August 2014, 08:50 AM   #20
bk856er is offline bk856er  United States
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Does your strong Placid BP recommendation also apply to Buff II with current gen Tridents + Legato v2? I'm currently using the LCBPS and I've been thinking about a PS change.

Also, is the original 30VA 15+15V trafo adequate for the above setup if I change to the Placid BP? I notice your current offering is 50VA.

BK
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