Thanks Mark, that was also on the agenda. I pulled a pair matched to .00697 and dropped in a pair at .00159. IT's to early to tell, but the initial power up, now at 5 mins has it holding to within about 5mV. 
My plan is to build both extra boards and have a look to see which of the 2 of 3 matches up best and go from there.
I can tell you this much so far, both the IPS6 and IPS7 are in my top 4, and the 6 is probably going to land in the top 2. This is on the lab speakers though too. The testing pair I use to make sure I don't take out any good speakers. My opinions could change when I get them on better speakers.
As I type and multitask, I'm in the 10min range now and this thing is solid like the other. Down to about 2mV movement.
My plan is to build both extra boards and have a look to see which of the 2 of 3 matches up best and go from there. I can tell you this much so far, both the IPS6 and IPS7 are in my top 4, and the 6 is probably going to land in the top 2. This is on the lab speakers though too. The testing pair I use to make sure I don't take out any good speakers. My opinions could change when I get them on better speakers.
As I type and multitask, I'm in the 10min range now and this thing is solid like the other. Down to about 2mV movement.
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I liked the IPS7 so much I've been op-amp and pre-amp rolling since I installed it. The issue with matching and stability on IPS6 prompted me to switch. I have a pair matched right about 2mV on the boards. I installed them and after about 5 min drift is too high to reach any conclusions. I can say this, the boards sound very good at first listen. More in an hour.
I wouldn't worry too much about a few dozen millivolts of offset voltage, meandering around on IPS6. Since the output of IPS6 is AC coupled to the M2x amplifier, the amp will never see it and you will never hear it.
Have some fun and reassure yourself: do a little bit of chalkboard engineering. Calculate the imbalance of drain currents (in percent) between the two JFETs, when testpoint TP1 and testpoint TP2 are a whopping 44 millivolts apart.
The facts which you need to complete this homework are:
1. the collector current of Q3 is six milliamps
2. the drain resistors R3 and R4 are each 1.33 Kohms
3. 44 millivolts is easily divisible by 2 ... intentionally, to make the arithmetic simpler
Have some fun and reassure yourself: do a little bit of chalkboard engineering. Calculate the imbalance of drain currents (in percent) between the two JFETs, when testpoint TP1 and testpoint TP2 are a whopping 44 millivolts apart.
The facts which you need to complete this homework are:
1. the collector current of Q3 is six milliamps
2. the drain resistors R3 and R4 are each 1.33 Kohms
3. 44 millivolts is easily divisible by 2 ... intentionally, to make the arithmetic simpler
I don't know where my last post went, but I said to AB, that even when it was wondering to 60mV I couldn't hear it, but also the test speakers aren't hyper detailed in case something goes bang. Going on memory, I don't hear anything diff after the replacement of the J113s and with a drift of about 2mV. Both pairs are matched at less than 2mV.
AB, my gut feeling here is there are other values not tested in matching which play a part in the drift. I would suggest you build the 3rd board try that and/or replace the pairs in the drifting board. I'm not sure that having them in the 2-3mV range is required, or that that will prevent the driift we are seeing. I think it quit possible to have a pair at 5mV and see less drift because of how other specs align. Remember, this one test we are running doesn't cover other variables.
We should swap some opamps AB.. you game?
Also, I need a favor from the community if possible, I need a good to very good I2S cable to check and see if mine has an issue. I really don't want to buy a $100 plus cable if it's not the issue. I would of course pay shipping both ways and just need it for a day or so. If someone has a good one and is willing please let me know.
JT
AB, my gut feeling here is there are other values not tested in matching which play a part in the drift. I would suggest you build the 3rd board try that and/or replace the pairs in the drifting board. I'm not sure that having them in the 2-3mV range is required, or that that will prevent the driift we are seeing. I think it quit possible to have a pair at 5mV and see less drift because of how other specs align. Remember, this one test we are running doesn't cover other variables.
We should swap some opamps AB.. you game?
Also, I need a favor from the community if possible, I need a good to very good I2S cable to check and see if mine has an issue. I really don't want to buy a $100 plus cable if it's not the issue. I would of course pay shipping both ways and just need it for a day or so. If someone has a good one and is willing please let me know.
JT
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The homework may be above my pay grade but I'll hit the books and give it a try after I finish this post.
In the meanwhile, after a little over an hour my left channel is ±1.5 mV/min and is not drifting appreciably. The right is stable as well but averages ±2.5mV/min. Even if I can't do the homework I would have concluded there is nothing to worry about. I'll give it a few more hours and see if there is any long-term drift.
I'm hard-pressed after an hour of listening to decide between IPS6 and IPS7. My subjective impression is that depending on the op-amp/pre-amp combination the IPS7 can sound ok to great. Usually crisp, tight control, impactful and musical. I was surprised that I prefer it's sound with Starving Student II as the pre-amp with the LM4562NA in place. I guess specs don't tell the whole story. I have not tried different pre-amps with the IPS6 yet since I just installed it but I really like what I am hearing out of the box. These are both great cards. Thanks Mark!
In the meanwhile, after a little over an hour my left channel is ±1.5 mV/min and is not drifting appreciably. The right is stable as well but averages ±2.5mV/min. Even if I can't do the homework I would have concluded there is nothing to worry about. I'll give it a few more hours and see if there is any long-term drift.
I'm hard-pressed after an hour of listening to decide between IPS6 and IPS7. My subjective impression is that depending on the op-amp/pre-amp combination the IPS7 can sound ok to great. Usually crisp, tight control, impactful and musical. I was surprised that I prefer it's sound with Starving Student II as the pre-amp with the LM4562NA in place. I guess specs don't tell the whole story. I have not tried different pre-amps with the IPS6 yet since I just installed it but I really like what I am hearing out of the box. These are both great cards. Thanks Mark!
Builders and reviewers who've listened to both IPS6 and IPS7, tend to have a strong preference between the two. Some adore 6 and others adore 7. Quite a few of them have said: OK done! This is BY FAR the best of all daughter cards, I'm never swapping them out ever again, it would be lunacy to change anything. Some say that about IPS6 (mister f p) and others say that about IPS7 (mister t j). But which of them is correct? They both are!
We all have personal preferences. These cards, and the M2X for that matter, are all so good the time of day, how much sleep you got the night before, and factors like that may have more influence than which op-amp we're using. Not to mention the rest of the system. I've been playing my own 24/96 FLACs, and Tidal Hi-Res through Roon to a HiFiBerry Digi + pro on an RP4. DAC is a Schiit Bifrost II MB, today feeding the aforementioned SSII. The M2X feeds a pair of Zu Omens. If your system is different your results may vary.
That long pre-amble was all leading up to saying that Mark nailed it above. I fell in love with the IPS7 2 days ago. Thought it was the best card yet. I was ready to stop right there. Then today's posts from @thompsontechs prompted me to try the IPS6. Whoa! I am in love again. The IPS6 may be my keeper card. Crystal clear, detailed, fast accurate impactful tight bass. Voices sound like they are right in front of you and guitars sound like someone is plucking the strings in the room with you. I'm listening to a trumpet solo right now that is incredibly realistic. Ok, I have been reading too many audiophile reviews but you get the idea. I like what I'm hearing. Amazing that one small card in such a complex chain can make such a difference.
Now I have a problem. I have all the boards stuffed for a second M2X. I want to finish it ASAP so I can do side-by-side comparisons between amps with different daughter cards. I looks like I have to use the Mark's Gerbers and buy some boards unless someone wants to give or sell me 2 IPS6 and 2 IPS7 boards.
Is it love or just infatuation? Time will tell.
That long pre-amble was all leading up to saying that Mark nailed it above. I fell in love with the IPS7 2 days ago. Thought it was the best card yet. I was ready to stop right there. Then today's posts from @thompsontechs prompted me to try the IPS6. Whoa! I am in love again. The IPS6 may be my keeper card. Crystal clear, detailed, fast accurate impactful tight bass. Voices sound like they are right in front of you and guitars sound like someone is plucking the strings in the room with you. I'm listening to a trumpet solo right now that is incredibly realistic. Ok, I have been reading too many audiophile reviews but you get the idea. I like what I'm hearing. Amazing that one small card in such a complex chain can make such a difference.
Now I have a problem. I have all the boards stuffed for a second M2X. I want to finish it ASAP so I can do side-by-side comparisons between amps with different daughter cards. I looks like I have to use the Mark's Gerbers and buy some boards unless someone wants to give or sell me 2 IPS6 and 2 IPS7 boards.
Is it love or just infatuation? Time will tell.
I've got all 7. I've heard them all. I like them all. They all sound great, seriously.
I think my personal preference favorite has more to do with the design esthetic I think is neat-o, groovy and cool more than actual sonics.
And let's face it, they are all buffers, the 600lb gorilla sonically (as intended) is the autoformer.
I think my personal preference favorite has more to do with the design esthetic I think is neat-o, groovy and cool more than actual sonics.
And let's face it, they are all buffers, the 600lb gorilla sonically (as intended) is the autoformer.
I should have mentioned that I lucked out when I was matching J113s. The two pairs I used were closely matched. In fact they were matched to within the reproducibility of my Extech 330 meter. 0.4mV and 1.3mV were the averages of 3 independent readings on each. Does it make a difference? The homework problem suggests not. That's another thing I can test with 2 systems set-up.
Agreed. I was surprised that daughter boards would make so much of a difference. I stayed with the Ishikawa for several months because I liked the M2X as it was originally designed. I think I had no expectation bias, but what I hear is what I hear. If the music isn't as good as I think it is, don't break my bubble.
I should add some additional information that may or may not be relevant to why my system sounds so good to me. I wrapped the autoformer windings in copper tape and placed a Mu-metal box over the unit. I also used an AnTek steel can over my AnTek AS-3218. I did an horrendously sloppy job on the internal wiring, in part because I didn't have enough wire to do it right and in part because I was in a hurry to hear the M2X. The amp is silent in the absence of an input signal. There is no hum or any other detectable noise at full gain with an ear to the speaker. I am not equipped to do measurements yet. I am not convinced they will reveal anything special, but I will get around to it. For now I am enjoying the Lake Poets at the moment...
Okay, so I woke, pretty much, in the middle of the night, and had a thought to break out the grinder butcher my way into the Burson V6 Vivid opamp. That is not an easy task as they have them wrapped up pretty tight.
Anyway, after carefully cutting away enough plastic and missing all the critical bits, I had the boards free of their plastic cages. I pulled out the 134 out and gently inserted the V6 and put the IPS7 back into the MX.
I didn't think I hurt anything getting it out of the plastic, but held my breath as I punched the power up and waited... no smoke, no sound. Wait, in my hast I forgot the stream had been muted. OKay volume down and un-mute. Creep up on the volume and......... Yes, there be sound. Okay is it good sound? Yes, but I need to let it run for a time. Opamp has zero hours on it. My gut feeling is it will be something special.
Anyway, after carefully cutting away enough plastic and missing all the critical bits, I had the boards free of their plastic cages. I pulled out the 134 out and gently inserted the V6 and put the IPS7 back into the MX.
I didn't think I hurt anything getting it out of the plastic, but held my breath as I punched the power up and waited... no smoke, no sound.
Wait, in my hast I forgot the stream had been muted. OKay volume down and un-mute. Creep up on the volume and......... Yes, there be sound. Okay is it good sound? Yes, but I need to let it run for a time. Opamp has zero hours on it. My gut feeling is it will be something special.Attachments
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