The tests you are doing now with the op amps and PCM1702 I did more than 15 years ago. Together with friends, we tested over 20 op amps for IV stage and then we concluded that a tube is always better than an average op amp. I'm sorry that I don't have any more pictures from that era.
Along with AD811 and ADA4625, I forgot to add AD797.
And let me not forget, along with the op amp, the regulators, power supply ,decoupling.... also play and for each op amp they give a different sound impression.
Along with AD811 and ADA4625, I forgot to add AD797.
And let me not forget, along with the op amp, the regulators, power supply ,decoupling.... also play and for each op amp they give a different sound impression.
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15 years is a long time. Many opamps have seen the light of day in the meantime. And it boils down to personal preference in the end 🙂 To me, opa1656 beats them all in most devices. Been saying that to nixie and mikorist for a while now, they are just now experiencing what i was saying. And all three have different tastes (and mikorist still have other preference as in muses02). Price wise unbeatable, performanse wise, very close to burson v6c which to me is best opamp on the market atm. And i simply can't justify the price difference as it's so close. Note that i clearly say to me. Saying something in absolute, especially in this sport of ours is something to frown upon. As said, it's simply personal preference as tastes are different.
That being said, proper discrete solution should beat opamps any time of the day. But, more money, more complex, larger footprint. There is no free lunch, everything is about compromise, you get to choose which one 🙂
That being said, proper discrete solution should beat opamps any time of the day. But, more money, more complex, larger footprint. There is no free lunch, everything is about compromise, you get to choose which one 🙂
I personally don't like op amps at all, nor do I have them in my system except the AD811, which is a different beast. I don't even have a place to test the OPA1656 even if I wanted to. About 15 years ago, I had a different opinion. Then I thought like you. In my opinion, there's no need to load the hi-fi with op amps if they don't need them, a phono stage or preamp can be done much better with discrete technology( or tube) , while success is not always guaranteed for IV due to the complexity of the IV conversion itself.
The classic op amp or VFA has a flaw in IV, which is unequal input impedance, while unlike them the CFA op amp is much better as is the discrete current conveyor which if performed superbly can have the same input impedance up to 1MHz. A discrete current conveyor, if it is good is not very easy for DIY and even commercial manufacturers do not really pursue this solution.
But as you say, everyone has their own wishes and thoughts about good sound.
The classic op amp or VFA has a flaw in IV, which is unequal input impedance, while unlike them the CFA op amp is much better as is the discrete current conveyor which if performed superbly can have the same input impedance up to 1MHz. A discrete current conveyor, if it is good is not very easy for DIY and even commercial manufacturers do not really pursue this solution.
But as you say, everyone has their own wishes and thoughts about good sound.
I am currently trying the AD811 with a PCM56P in a Sony player for the heck of it. What do you think?
I have already cut out the traces using the internal operational amplifier that was being used. Do you use cog (npo) for feedback caps? What frequency response do you normally use? I am currently targeting about 60KHz low pass (two pole).
Can I buy an AD811 and plug it into a Miro DAC? It won't oscillate or cause any other problems?
No
First check the power supply values - AD811 is going to significant overheat. It should be less than 14V in Jung application. +-12V is good maybe even +-10V...
Do not put ad811 without bigger heatsink - much bigger than in Jung example.
Not to avoid that serial "R" in the input line of OP. I think that the value of 1K
Measure the "C" values in parallel with feedback R. Maybe to add RC net also.
What about the supplies to the PCM56? Have you done anything about them? Super-regs perhaps?
I going to try soon opa1633 for diff i/v , have better BW than opa1637 which I have used previously with good result.
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I had to move to the Head/Fi forum to get the right information. No one listens to headphones seriously here.🤣
There they claim that the OPA2107 is the best on headphones.
I have never heard of OPA2107.
OPA1656 or Muses02 or Sparkos is my recommendation. Then Burson. But I don't listen to speakers. Everything sounds different to me on headphones.
I have a couple of PCM56s somewhere in the drawers but I've never done anything with them. Certainly Super-regs will help, but I would still recommend a shunt regulator, for example a Salas shunt and if you are skilled with a soldering iron then this.
I haven’t heard the AD815 come up in quite some time. Carlosfm, and the other guys at the defunct HIFIDIY site used to rave about it for use in a line stage. I’ve never auditioned a circuit featuring it, but have always been curious about the sound. Would you share your subjective experience? Thanks.
So far I haven't tried it either, my intention is to make an amplifier in the style of Jan Didden.
I also have information that it is excellent as a line stage, I am even thinking of making an IV stage with it (although it is the smaller brother of the AD811).
I also have information that it is excellent as a line stage, I am even thinking of making an IV stage with it (although it is the smaller brother of the AD811).
Way back I worked on a project of stereo to 5.1 around QSound 5.1 and 7785 chips,
that time I came across AD815 and BUF634 built a lot of circuits around both of them, used them as buffers and later as Headphone amps, BUF634 circuits are still lying around, AD815 in my subjective opinion was too soft, missed out on lows that is why all the little circuits built around AD815 cant be seen in my lab anymore.
If anyone here is interested I have four PCM1702-K for sale along with Miro's PCBs. Chips are absolutely genuine and in perfect condition.
Was hoping for £60 a pair with PCB.
Also spare PCBs for AD1862 (no onboard I/V), AD1865, PCM63 and PCM1702
I already have AD1862N-J and PCM63P-J to try so don't need them all, will hopefully be able to do comparisons with Abraxalito's Abbado II NOS DAC.
Was hoping for £60 a pair with PCB.
Also spare PCBs for AD1862 (no onboard I/V), AD1865, PCM63 and PCM1702
I already have AD1862N-J and PCM63P-J to try so don't need them all, will hopefully be able to do comparisons with Abraxalito's Abbado II NOS DAC.