Discussion in 'Modifications and Tweaks' started by Marvey, Jul 22, 2021.
Well then of course I am wrong. Who pissed in your cereal?
I think U20 is on the DS Modi.
Let it run for an hour, leave it on all the time, send on loaner tour (no longer need warms up).
Correct. The TL082 is probably the servo.
This may be useful (from link):
From: johnc124 (General Manager - TI Linear Amplifiers Business Unit)
OPA1656 has about 6 dB more open loop gain at audio frequencies, so distortion is potentially lower. Some work was also done to reduce common-mode distortion in the OPA1656 when the impedances at the inputs are mismatched. And of course, the price on the OPA1656 is lower
When I use my Modi 2U with the Jot 2 there is quite an edginess with some headphones (HD540, HD250), but if I use my Chord Mojo it really smoothes out. Haven't tried my Modi Multibit with the Jot yet.
Don’t take me wrong, not everyone has the same experience with a piece of gear. I’m possibly part of the ‘sensitive flower’ clan in the sense that I experience a slight harshness to its sound signature with my usual repertoire.
@Hands, this is for you. Use Magni 3+ as an IV/output stage. This topology same as the Theta Gen V - except it doesn't run at 100C and warp the PCB after five years.
YEL (left of R120 / R220) = signal from IV out DAC
GRN (top of R201/R101) = ground
Usual disclaimers: explosions are your fault, I could have gotten something wrong, better than any opamp, etc.
Does this bypass an amplification stage?
Yes. To the output stage. Can get the idea from the board layout.
Yup, essentially what I've been doing for a few months now with my AD1862 DAC.
For GND, I wasn't 100% sure which side of the resistor to put it on, what to do with the pot, etc. That and figure out if I needed to connect the PCB GND to the DAC's chassis.
I can't say I tried every permutation, but I think I settled on connecting the GND wire to the other side of resistor, where the output of the pot leads. I removed the pot and connected the output through hole to GND. And the PCB standoff near the power supply I have connected to the ground point on my chassis.
This seemed to offer the lowest amount of noise in measurements after fiddling around both with the Magni 3 and 3+ as the IV/output stage. Unfortunately, while I've learned a lot, I still am not totally well-versed in this field. And, so, I end up doing a lot of trial and error testing to see what works, and then what works best of the lot. (Don't do this if you can't handle breaking a lot of shit. I don't really learn otherwise.)
Feedback resistor also swapped out for one at 3K for 2V RMS out with the 3+ on low gain. This is still a sizable jump in gain over stock despite the 3+ being set to low gain. Not sure if I need to swap out other resistors in a relative fashion to account for this. Again, a bit over my head.
Instead of using the pre-outs, I removed the headphone jack and wired up some 100 ohm resistors on its outputs. More or less how the pre-outs are setup, but with a shorter path.
While this is fun to play around with, and it sounds damn good, number chasers are probably better off sticking to opamps. When you deal with boards like the 3+, you're looking at separate power requirements, separate wires to connect boards, and so on. You're more likely to run into noise, hum, and ground loop problems. And an opamp is probably going to have better paper specs anyway, even if you got the noise floor perfect.
I would agree with you on that. The opamp swap does more to change the character of the DAC, arguably for the better if using the 1656/2156. @jexby and @zerodeefex can attest that I got unreasonably excited about it in a group text when I tried it. The amount of change really caught me off guard.
It seems to address what I'd consider the core weaknesses of both the Modi and Bifrost 1 MB: mild-to-moderate grain, mild haze, bass mushiness, and kind of a grey, reserved sound. These seem to change for the better. Other changes and are more different rather than better.
The Bifrost 1 MB w/ opamp swap gets it closer to Bifrost 2 territory in terms of subjective performance. Not as expansive, not as dynamic, not as clear, but also has this sort of bloom and warmth to it in the lower-mids I find appealing. BF2 still gets the nod for performance, but it was closer than I expected when compared.
Let me see if I have any measurements backed up somewhere that compare before/after the opamp swap...
Side note, I'm still super impressed how much Schiit squeezed into the Modi MB.
I feel stupid for having to ask, but this requires two opamps and not 1? The OPA1656 is a 2 channel IC. Is this summing a differential output from the DAC chip? I apologize for my ignorance.
I ordered a spare so I have two coming, but my margin for error just went away…
Correct, you'll need two opamps, one to replace each of the AD8512.
These DAC ICs have one current output per channel, so should be natively single-ended without summing. Only one half, or one amplifier, within the opamp is used for IV duties.
I believe page 16 in this datasheet shows a visual diagram of how the second amplifier in the opamp is utilized (i.e. for Rcom and Vref on each channel):
You'll see two 8512 opamps in the diagram, which should represent how both amps in the opamp are used with the DAC IC.
As for another general comment, one could also replace the servo opamp. It's not going to make as much of a difference as the IV opamps. I don't think there's much agreement in the hobby if servo opamp choice is particularly important, so long as it meets some basic spec requirements for the use case.
The Bifrost 1 MB, later revision, used the OPA1678, I think? I think Magni 3+ also uses that compared to the older part as seen in the Modi MB and Magni 3 for the servo.
Don't buy additional opamps just for the servo though, please. Diminishing returns. Maybe worth a consideration for kicks if you already have spare parts, know they're appropriate, aren't a first timer with SMD opamp soldering, and have nothing better to do.
I also had some spare voltage regulators from Sparkos that I stuck in the Modi MB for shits and giggles. Can't say they made much of a difference (so don't do it, not worth the $$$), but it was more of a "why the hell not" sort of deal.
Also accidentally got some nice sparks flying when one of the larger Sparkos regulators touched the chassis. I hadn't noticed it the first power on, but did notice my measurements had a lot of nasty mains noise. Took me a moment to figure that one out, or, rather, a second power on where I paid closer attention to the device. Didn't seat/bend the regulator properly for clearance. Thankfully, DAC survived.
I should be very clear, my Modi MB became a sort of dumping box for stupid experiments (and learning!) once I got a newer revision, Bifrost 1 MB. Think of it as a lab box to test things for QA and Production. If you're not willing to treat it as such because you can afford it, I don't recommend anything more than the two IV opamp swaps.
Mod-i MB OPA-1656 transplant was successful. I now hav one stock unit and one turbo one. I’ll put together some comparisons ASAP.
So given how folks are bitching about Lokius not being true balanced - I thought up of a solution during lunch today. There is a way that we can get a true balanced solution (balanced all the way through without phase splitter or sumers). Note that this works for Loki, Lokius, etc.
It's even dual mono! (Note: x2 Loki will be needed). The usual disclaimers apply: if something explodes, it's your fault.
Is this like a smaller scale version of Gungnir/Freya hack several members did a few years back?
I finally got time to build my A-B box. I decided to order decent neutrik RCA jacks and a good switch from Mouser.
I have been listening around an hour, and I feel like the Dacs and the ZDT Jr are really just now getting warmed up.
Right now, I would say that the difference between stock opamps and OPA1656 is subtle. I’m surprised that there is almost no volume difference.
I plan to edit this post as the night goes on.
96khz/32 bit Lateralus - Lateralus - OPA1656 sounds a bit less congested. Notes sound just a tad more real. Bass quality is a small step up. It’s still not a very large difference. Overall, stock sounds more flat, but again, only slightly.
I need to verify that my Modi MB DACS are running the same firmware. Regardless, both sound great. Schiit really did a fantastic job on this DAC, not even considering the price. It’s an iconic item in the hobby.
Switched headphones from Grado PS500 to Senn HD58x. Grado was in low impedance jack, the 58x in high. Now the difference is apparent. The OPA1656 unit is clearer and cleaner sounding. Still not huge, but easily audible. The Grados sound better across the board, but with them, the difference is less pronounced.
Back to Grado, but in high impedance jack. Tool - Aenima - Eulogy (96/32) - more airy on OPA1656 unit. Headstage is better. Better instrument separation and clarity.
Wetleg - Chaise Longue - prefer OPA1656 unit.
The Hives - Two Timing Touch and Broken Bones - no preference.
Kyuss - Phototropic - Prefer OPA1656 unit.
In conclusion (for tonight) I will mod the stock unit with OPA2156 chips soon. I don’t expect to be able to differentiate that from the OPA1656 unit.
So, you remove the output
would you need to remove the opamps from the modi mb to wire the output to the Magni 3+, or can you just connect the Magni 3+ to the input pins of the opamps and leave them in place?
Round 2 of the Modi Multibit dac-off jack-off starts tonight.
RCA Cables - self-made using Rean RCA jacks and Mogami 2552 cable.
SPDIF - I have Belden cable, not not a SPDIF splitter made with Belden 75ohm. I'm using a Monster Cable splitter into 75Ohm RCA cables. That's all kind of wrong, but it's the best I can do right now.
Source: Raspberry Pi 3b or something like that. Hi-Fi berry i2s to SPDIF. Volumio => Apple Music => Airplay from MacBook Air => Volumio, so limited to 16bit, 44100KHz. 2 Modi MultiBit Dacs, one stock, one with OPA1656 Opamps replacing the Analog Device stock op amps.
Amp: ZDT Jr. with GE 5654 matched tubes from Riverstone audio.
Headphones: Grado PH500 OG, Sennheiser HD58x, Creative Aurvanna Live (biodyna lovin').
Warmup period begins now: 20:07:00 CDT. What better music to warm up to than the Hives?
Shall we begin? No, we shall warm up. I'll begin for real around 21:00 CDT.
Edit a). I forgot. The lubrication is Coca Cola Zero (approx 40%), Bacardi (60%). And I'm warming up with Cake because I like Cake, but it's not comparison worthy. Sorry.
Edit b). It's on now. Mick Gordon - Rip and Rear - Switch position Right. I don't know right now which way is the stock position and which is the new OpAmps. We'll find out together at the the end.
Edit c). Ministry - Psalm 69 - Just One Fix - Switch position Right. Seems more clear.
Edit d). NIN - Broken DE - Happiness in Slavery - No preference. Both sound equally angry and full of hate.
Edit e). Switching from Aurvanna live to Grado PS500 - James Brown - Live at Budakon - Sex Machine - Switch Position - Right - More real sounding, more what I'd expect if I was there in the audience. Right on right on. Get on up!
Edit f). Desert Sessions - If you Run - Switch position - right. Only when the the song get's more active and guitar heavy though.
Edit G) Bob Schneider - King Kong (Title Track) = Switch position left is left glarey. Otherwise, hard to say.
Edit H). Beastie Boys - Paul's Boutique - Johnny Ryall - Switch Position right no doubt.
Edit I). Wild - Adam Jones & K.S. Rhoads - Right is clearer. More immediate, as if there is less between the musicians and me somehow.
Edit J). Adam Jones - The Witness - The most beautiful song I've ever heard is more beautiful at switch position Right.
Edit K) A great recording. AC/DC Back In Black - You Shook Me All Night Long - no pref
Edit L) Audioslave - Show Me How to Live - Bass is livelier on position RIGHT.
Edit M). break time - time for Grey Goose and lime soda water.
Edit N). Foo Fighters - In Your Honor - Still - Position Right.
Edit O) Nirvanna - Nevermind Super Deluxe - Lounge Act - No preference.
Edit P) Paul Gilbert - Fuzz Universe - Fuzz Universe - Bass is just better at position Right.
Edit Q) A Perfect Circle - Mer De Noms - Judith - no pref. Double edit - prefer right.
Edit R) The Police - Synchronicity - Syncronicity II - Ever so slightly more full sounding on Right.
Edit S) The Power Station - The Power Station - Bang a Gong (a personal favorite song since I was a child) - slightly more clear on right.
Edit T) QOTSA - Era Vulgaris - Make It Wit Chu - Right right right. Sometimes the same is different, but mostly, it's the same. LOL.
Final edit). I've found myself debating whether I can actually hear any difference or if I just want to. I'm not sure my opinion means anything anymore. I haven't heard a Bifrost, I haven't heard a Ginguir or a Yggdrasil. My opinion doesn't really mean shit. I can't be certain I can hear a difference in these Modi MB. I'm questioning everything right now. I feel like I've wasted a lot of time on this. The difference in the opamps is so small as to not really matter if I'm being honest, at least with my gear. I'm feeling let down and depressed and very frustrated if I'm being honest. I need to re-evaluate my position. I need to hear some better gear. An op-amp swap isn't the answer. It's just not.
Right: stock. Long live Modi MB!
Yes, remove anything that could be a load. Note that I haven't tried this - only @Hands has.
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