IVY III tweaking for warmer sound

[ijscobar]

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.

The magic words... I ordered both Placids to replace the old ones of my BIIISE.

 

[sbelyo]

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.

I have those so I should be good

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.

To raise the output impedance I increase the output resistors correct?

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.

I have the latest Placid HD BP. But, I have the older 30 VA transformer. Should I up it to the 50 VA?

 

[sbelyo]

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 think R24 is wrong. The feedback cap should be placed across R22 Left and R23 Right Am I correct?

 

[Russ White]

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

Absolutely. The Placid HD (and HD-BP) will be a significant upgrade.

 

[Russ White]

To raise the output impedance I increase the output resistors correct?

Yes - 100-221R can make a subtle difference. Some will prefer to use 0R. The effect will depend largely on the load (cables and amp etc).

I have the latest Placid HD BP. But, I have the older 30 VA transformer. Should I up it to the 50 VA?

30VA is certainly sufficient, but 50VA will give very slightly less ripple at the reservoir caps.

 

[ijscobar]

30VA is certainly sufficient, but 50VA will give very slightly less ripple at the reservoir caps.

Can one hear the difference?

 

[Russ White]

I would say less so with the new Placids, and they have significantly improved PSRR over the previous version - still it is difficult to say what people will find audible.

 

[sbelyo]

Another user here posted that when using a pair of LME49990 in the BAL/SE stage that they will oscillate. He says to use 100-220pf styroflex or silver mica cap for feedback compensation when you use lme49990. When looking at the schematic I should place them across R22 Left 2.2K ohms and R23 Right 2.2K Ohms am I correct?

He states a different number for the right side so I just want to be sure that was an error. Can someone confirm?

 

[androa76]

Correct. MKP ( roe...ero1830 Blue color) can be used if finding styroflex or mica is difficult
And R25 and R26 was 50ohm because i used only se output.

 

[sbelyo]

Correct. MKP ( roe...ero1830 Blue color) can be used if finding styroflex or mica is difficult
And R25 and R26 was 50ohm because i used only se output.

Thanks... I got most of the parts yesterday. I just have to place a digikey order

 

[sbelyo]

Just to update this thread

I used PRP resistors throughout
I used Vishay Roderstein .1uF film caps for the supply decoupling
I paralleled two Amtrans 8.2 nF film/foil polypro caps for the analog filters
Used two LME49990 op amps on a brown dog adapter and added a feedback compensation cap for each channel (value and type mentioned earlier) in place of IC5 (LM4562)
I used Nichicon Muse caps for the electrolytics

You'll need longer pin headers (Digikey SAM1061-06-ND) and standoffs (Digikey 36-8404-ND) to clear the brown dog adapter and electrolytics.

My first impression once installed was not the best. The highs were great and very detailed but there was almost no bottom end. After a few hours the highs started to become shrill. I suspect it is the BAL/SE opamp and feedback cap. My plan is to remove those items an re install a LM4562 and then listen again

In the mean time I re installed a stock IVY III, then installed a 50 VA transformer for it, then swapped out the PSU for the new Placid HD BP 2.1 along with a 30 VA transformer for the BIII VD supply

Those three steps were a significant improvement in sound. The bottom end appeared while the highs stayed detailed and there was more separation between instruments. My next step is to upgrade the BIII VD supply and then listen again for a while. Once completed I'll make the changes to the IVY III again and see what happens

 

[BrianDonegan]

The J-FET-input OPA1642 actually does a nice job in place of the LM4562/LME49720.

Be careful of added inductance with longer leads and added effective trace lengths when modding.

 

[sbelyo]

I will check that op amp out. I suspect using that adapter had a negative effect because of the trace lengths. I'm pretty sure it was oscillating but I have no way to measure

 

[sbelyo]

The J-FET-input OPA1642 is excellent. I'm pleased with the sound. I removed the compensation caps and the other opamps on the adapter. Then, I installed the OPA1642. The sound compared to an unmodified IVY III goes from a tad bright to a neutral sound. It was a step in the right direction. I feel the amtrans caps took about 24 hours to burn in so if you build an IVY like this make sure you let it settle in before you judge it.

 

[sbelyo]

I'm planning on ordering 0.1% 1/4 watt 50 PPM PRP 9372 resistors for the TPA Ivy III. Normally this tolerance is not stocked by anyone and the price prohibits ordering one or two sets. I started a group buy thread for it here on diyaudio. I just need 5 people to get them for a decent price. The details are in the GB thread. Is anyone interested?