If I'm not mistaken, the OPA4627 is intended to be the nearest alternative to an OPA627.
Yes, I am mistaken. I was going from recollection, but see that it was the ADA4627/ADA4637 pair from Analog Devices I was thinking of.
https://www.analog.com/media/en/technical-documentation/data-sheets/ADA4627-1_4637-1.pdf
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I used that DAC to drive the sources of some 2sK170 and J74 into OP275 for final I to V and filtering. I don't have a copy of the circuit anymore but I used metal film resistors and garden variety NPO/COG caps and it sounded impressive even on the breadboard.
instead of simply swapping pin-compatible ICs it could be a better solution for replace the esemble AD844/2xBUF604 like realized in the Horch DAC model "STEPS" - go to post #25/26 under
One of German's most ultimate DAC: Horch "STEPS 1" - Schematic wanted
Also the unbalanced I/U section of Pass' D1 could be of interest (definitely better than OPA2604 as I note by a listening test on a DAC with PCM1702).
https://www.diyaudio.com/forums/pass-labs/30208-d1-stage-finished.html#post616248
https://archiwum.allegro.pl/oferta/i-u-convert-by-pass-d1-salas-i6621041940.html
Pass D1 I/U - DIY - Audiostereo.pl
DAC – Garbz Electronics
Whether there are now integrated OP amps like the OPA1656 or that one under
https://www.ti.com/lit/ds/symlink/o...472166&ref_url=https%3A%2F%2Fwww.google.de%2F
that clearly blown away the old-fashioned approaches just mentioned in terms of sonic character in a listening test ?
That would be really interesting to know.
One of German's most ultimate DAC: Horch "STEPS 1" - Schematic wanted
Also the unbalanced I/U section of Pass' D1 could be of interest (definitely better than OPA2604 as I note by a listening test on a DAC with PCM1702).
https://www.diyaudio.com/forums/pass-labs/30208-d1-stage-finished.html#post616248
https://archiwum.allegro.pl/oferta/i-u-convert-by-pass-d1-salas-i6621041940.html
Pass D1 I/U - DIY - Audiostereo.pl
DAC – Garbz Electronics
Whether there are now integrated OP amps like the OPA1656 or that one under
https://www.ti.com/lit/ds/symlink/o...472166&ref_url=https%3A%2F%2Fwww.google.de%2F
that clearly blown away the old-fashioned approaches just mentioned in terms of sonic character in a listening test ?
That would be really interesting to know.
Attachments
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this approach looks interesting, too
https://www.diyaudio.com/community/...urrent-mirror-iv-converter-a-la-ad844.360162/
https://www.diyaudio.com/community/...urrent-mirror-iv-converter-a-la-ad844.360162/
I tried OPA861 (not the same as PR, i dont want to copy, but it not much different because of the only concept) with TDA1540 jfet current inj. 2mA.
And I can say that it was big disappointment about the sound outcome
although measurements was good.Immediately after that I tried AD811 - the sound was significantly better.
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I remember once long time ago I tried PR diamond pair transistor IV with TDA1541A - that was very very good sounding IV even with unmatched/worst case sc. transistors and CD power supply used. Based on that good experience I decided to try OPA861 but that was disaster...
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I tried OPA828ID with a SOIC-to-DIP adapter, it sounds quite good.
https://www.ti.com/product/OPA828/part-details/OPA828ID
https://www.ti.com/product/OPA828/part-details/OPA828ID
@Zoran, mine sounds very good but neutral with deep tigth bass that are unusual with the tda1541A and clear highs w/o the usual romantic mid than the tda1541A can sometimes exhibit if on the early non asian plants.
Although needed a clever passive parts tunning imho few push at the stupid level I tweak (near the autistic behavior, lol) and a c-core power transformer.
But that's a whole at home : my pre is a Yamaha CX2, so a lot of old Elna and Nichicon Caps inside and discrete scheme being on the warm side. Amp being very neutral while mosfet output with smps as power source.
Maybe thenon matched discrete diamond added some H2 in your tests ?
I still have have to test the 1656 on the tda1541A that worked fine with the ad1862 for my ears ! Some are using current opa with tda1541A they seem to appreciate. All of that is on hiatus because not much time for hifi and DIY these days.
About Rogic, I know he is not using opa861 on his on shelves DAC. His last diy Aya5 was a discrete diamonds with brandnew japonese discretes. I haven't picked one by lack of time and also because the electronic parts sourcing problems, although I am the one asked him to go discrete if possible on the Aya5 to bring some change after the good sucess of the Aya2 2014 some members resurected by asking him to continue DIY pcbs (and it was with opa861) after the disaster of a brainstorming tda1541A pcb thread !
As far I am concerned, the opa861 works fine in the AYA2 2014 and AYA DS and AYA4 with some tweaks. I can not come back with DAC with serie caps outputs since, whatever what is before : tubes or oap or discrete. I surmise a bipolar as I/V then a 1656 like after as a buffer should work easily without hard tweaking with the TDA1541A or TDA1540 !
Although I dunno about what oaps flavors these days !
Although needed a clever passive parts tunning imho few push at the stupid level I tweak (near the autistic behavior, lol) and a c-core power transformer.
But that's a whole at home : my pre is a Yamaha CX2, so a lot of old Elna and Nichicon Caps inside and discrete scheme being on the warm side. Amp being very neutral while mosfet output with smps as power source.
Maybe thenon matched discrete diamond added some H2 in your tests ?
I still have have to test the 1656 on the tda1541A that worked fine with the ad1862 for my ears ! Some are using current opa with tda1541A they seem to appreciate. All of that is on hiatus because not much time for hifi and DIY these days.
About Rogic, I know he is not using opa861 on his on shelves DAC. His last diy Aya5 was a discrete diamonds with brandnew japonese discretes. I haven't picked one by lack of time and also because the electronic parts sourcing problems, although I am the one asked him to go discrete if possible on the Aya5 to bring some change after the good sucess of the Aya2 2014 some members resurected by asking him to continue DIY pcbs (and it was with opa861) after the disaster of a brainstorming tda1541A pcb thread !
As far I am concerned, the opa861 works fine in the AYA2 2014 and AYA DS and AYA4 with some tweaks. I can not come back with DAC with serie caps outputs since, whatever what is before : tubes or oap or discrete. I surmise a bipolar as I/V then a 1656 like after as a buffer should work easily without hard tweaking with the TDA1541A or TDA1540 !
Although I dunno about what oaps flavors these days !
I agree, opamps just not sound good in i/v, I am looking too for an good diff opamp for i/v, I will try opa1633 and if sound is not a well I will look for something discrete for i/v or at least maybe an transformer for them. I am used opa1637 for previous project as an i/v and sound is thin in comparation to the transformer i/v, simply lacks dinamics, dac is an discrete DSD dac and I'm believing I need something with higher slew rate, opa1637 is too slow for that.
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DAC output stage charakteristics are main factor for any consideration about IV.
Output resistance of DAC, if there is any DC off-set, amount of p-p current, current injection option, etc ets.
specific dac needs a also specific transformer. not just an "transformer"...
That is for OP too...
Output resistance of DAC, if there is any DC off-set, amount of p-p current, current injection option, etc ets.
specific dac needs a also specific transformer. not just an "transformer"...
That is for OP too...
Thanks Zoran, we have used ina849 for diff to se for tone control and etc, opa1637 was used for i/v, I was happy with result but sound is definitelly better with transformer i/v, transformer was https://it.aliexpress.com/item/32810421236.html , sound very good with that transformer, sound is good too with opa1637 but i hear diference in instruments separation, I'm believing opa1637 simply not have enought BW for i/v and thinking to try new opa1633 which have much higher BW, what you think about opa1633 as an diff i/v ?
What should be done with this transformer is first to measure some basic things
1. Lp inductance of the primary
2. Inductance of the primary with secondary closed. That will be for calculating aprox Mutual indictance and coupling factor.
3. DC resistance of the windings. but with the caution because higher Vdc can saturate laminatons... Better to put some known resistor K range and use 10x K range in the meter, Then substract values... Or use some pro old school LRC meter...
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4. Measure transfer with known generator resitance but with secondary left open (somehow) sound cards can have 10K input
Probably best way is to prepare very simple JFET buffer with high input impedance like 1meg or 2,2meg, To find te true resonant F.
5. Then with the same setup reduce JFET buffer R input, to try to round the resosnant peak.
6. same time measure db loss with lower R load should be max -0.25db. If it is still resonant peak occurring, it is a must to aply RC sircuit in the secondary to avoud overdamping the total BW sygnal beyound -0.25db
7. Repeat transfer with some other value of signal generator. you can also use simple 2 JFET buffer for input with R serial at the out of the buffer and in to the primary. Real value will be RdsON+Rserial. For the 2SK170 RdsON is about 40ohms I think?
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If You will going to make these vey simple measurements You will see that the datas given in the store could not be posibile...
And bare in mind that transformers adding just 3rd harmonics. And with signal increase the distortion is increasing too. So keep the signal low. Amplify the sigmnal after the transformer...