Is BC550C acceptable for v3.1 build in instead of BC550B or what are possible alternatives? 'B' gain version appears to be discontinued.
Is the transistors in need of matching? (hFE maybe?)
Also, if using only balanced output - is it even needed to power the center part of the board?
Also, if using only balanced output - is it even needed to power the center part of the board?
No - they really don't *need* to be - but it does not hurt to match them either. You may eke out slightly better THD. 🙂
No - no need to power the BAL/SE section at all - you could just leave all those parts unpopulated.
No - no need to power the BAL/SE section at all - you could just leave all those parts unpopulated.
Hi Russ:
I there any harm running the Legato on 16V rails? Any adjustments I need to make?
Thanks!
I would not suggest it. Still it may be possible if you choose an op-amp for BAL/SE stage that can handle those rails.
I wouldn't do it.
If not needing BAL->SE converter, one can just skip powering the "center" part of the board - isn't it so?
Thanks Russ.
Looking up the LM4562 datasheet, it looks like it can take up to 17V rail supply voltage and the LME49600 can take up to 18V. Seems like I should be OK with 16V rails. Are you concerned with power-on surge?
My delima is trying to use the same Placid BP that powers the Legato to also power a Dynalo headphone amp which I hope to run on 16V rails. Maybe I should consider tuning the Dynalo for 15V rails. After all the headphones that are intended to be used with the Dynalo are both low-impedance headphones.
The biggest concern is really heat - but you could slightly increase the CCS resistors to compensate.
Is it ok to use 4.7K instead of 4.99K for R17-R24, R33-R36 on v3.1?
If I understand the schematic correctly, the buffer IC2 is in the feedback of IC1.2 opamp used as the differential amplifier at unity gain.
If I understand the schematic correctly, the buffer IC2 is in the feedback of IC1.2 opamp used as the differential amplifier at unity gain.
Hi there,
Not long ago i had one of Panasonic FM caps damaged by accident, so i replaced it temporarily with what i had at hand - Panasonic FR 330/25V as they are almost the same size. This could be burn-in related or something, but i noticed the difference and replaced the rest of electrolytes on one channel to 330/25 just to compare left/right out of curiosity and i "think" the side with 330 could be sounding better...
Is it ok to use larger values in these positions (C9,10,13,14,15,16)? Because i have a lot of these 330/25 and none of 100/25. They also have half the impedance of 100/25 so should be a good thing?
Not long ago i had one of Panasonic FM caps damaged by accident, so i replaced it temporarily with what i had at hand - Panasonic FR 330/25V as they are almost the same size. This could be burn-in related or something, but i noticed the difference and replaced the rest of electrolytes on one channel to 330/25 just to compare left/right out of curiosity and i "think" the side with 330 could be sounding better...
Is it ok to use larger values in these positions (C9,10,13,14,15,16)? Because i have a lot of these 330/25 and none of 100/25. They also have half the impedance of 100/25 so should be a good thing?
In power related positions? I tried Nichicon KZ and Elna Silmic II in these positions in just when i first assembled Legato and even after weeks of burn-in i found them performing worse.
They are great for audio path, but not power related\filtering it seems.
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I think Silmic II is the best of all caps. Maybe not for digital circuits. I never tried them for this.
Brian, Russ or anyone....
Originally Posted by Erlend Sæterdal
Is it possible to use other resistors around the opamp to get some gain there ? Change the resistors 21-24 to 10 kohm ?
Is it possible to get 7 to 10 volts of output from the opamp output stage, without sonic damage? I'd like to use the Legato to go direct in to the PASS F4 which has no voltage gain.
Originally Posted by Erlend Sæterdal
Is it possible to use other resistors around the opamp to get some gain there ? Change the resistors 21-24 to 10 kohm ?
Is it possible to get 7 to 10 volts of output from the opamp output stage, without sonic damage? I'd like to use the Legato to go direct in to the PASS F4 which has no voltage gain.
It should definitely be doable. 🙂 Any time you increase gain you will also increase the noise floor - but it should still be very good.
I don't post stuff very often but wanted to share something. My Legato 3 is sounding REALLY nice with some changes I've made recently. Maybe I'm blinded by the new "sheen" and the excitement will wear off but anyhow.. I used the Legato 3 completely stock for a couple of weeks before mods (replaced a tweaked Legato 2) to get a feel for it. My dac is powered by Salas shunt supplies which I don't believe perform the best with a lot of capacitance at the load. Here's what I've got: I removed all of the stock capacitors (with proper rework equipment) and replaced the 2n2 Wima's with polystyrenes (LCR Components, 2200pf, EXFS/HR series, $2 ea. at Newark). Swapped the electrolytics with Vishay MKP1837 .1uF caps. I use the SE output so I pulled the stock LM4562 and socket and replaced with a J-FET-input OPA1642 on a SOIC8 to DIP8 adapter. Concerned about decoupling I carefully soldered SMD Panasonic ECPU .1uF caps right at the supply pins. Also used Panasonic ECHU 100pF caps in place of the stock ones (directly across adapter pins on the bottom of the board). None of this stuff fits the board and I had to get creative. I would not recommend doing all of this without lots of experience, a good magnifier and solder/desolder rework station, a steady hand and patience. My usual demo music that's been played a million times is alive now in a way I've not experienced before. Big improvement top to bottom but particularly the upper range.