So just started thinking about my current phono setup. I believe I'm already using my denon in balanced mode after reading your article. I'm using cinemag input xfmrs which are not tied to ground in any way. This is a recent addition to my system in the last 4 months and I noticed how quiet the phono stage is now compared to direct connection. Am i thinking correctly?
Owen, SY,
Very interesting discussion on the interaction between MM cartridge Z and the noise generated by a phono stage. Doug Self discusses this in his "Small Signal" book, which I'm sure you're familiar with, but many readers many not be.
Given that the noise depends on the cartridge R and L, I wonder if there is a "standard cartridge" that all manufacturers use to spec their equipment? There are lots of models for cartridges of course (Self gives one in his book), but it seems to me that manufacturers just measure in whatever way makes their equipment look best. So there is no reliable way to compare.
Do I have this right?
Scott
Very interesting discussion on the interaction between MM cartridge Z and the noise generated by a phono stage. Doug Self discusses this in his "Small Signal" book, which I'm sure you're familiar with, but many readers many not be.
Given that the noise depends on the cartridge R and L, I wonder if there is a "standard cartridge" that all manufacturers use to spec their equipment? There are lots of models for cartridges of course (Self gives one in his book), but it seems to me that manufacturers just measure in whatever way makes their equipment look best. So there is no reliable way to compare.
Do I have this right?
Scott
Unfortunately no - there is no standard. John Atkinson of Stereophile was on this forum a few years ago. He shorts the input to phono SMPS to get an idea of the input noise voltage. This of course does not take into account the current noise that arises from the cart L and R.
I suggested that he use a standard source that would factor this in but the idea did not progress with him.
500 ohms and 600 mH would be a reasonable source. Alternatively, the industry should just settle on using a specific cart as a reference - how about a Shure V15?
I suggested that he use a standard source that would factor this in but the idea did not progress with him.
500 ohms and 600 mH would be a reasonable source. Alternatively, the industry should just settle on using a specific cart as a reference - how about a Shure V15?
Fancinating - but what does it sound like. Which is the crusp of why we build
Since it it designed specifically to just amplify and equalize, rather than be an effects box, I'm going to guess that it doesn't have any "sound," just that of the phono cartridge.
Fancinating - but what does it sound like. Which is the crusp of why we build
SY is pretty much spot-on in his reply. It doesn't really sound like anything, and that's the point of most of the things I build.
If coloration is your thing (and that's fine if it is) then I feel it's better added somewhere other than the phono stage. I'd suggest the preamp or the power amp as good candidates.
The main reason I built this was to use it for archival purposes along with my newly developed ES9102 ADC. In this application, you don't really want a particular sound so much as you want absolute accuracy.
I suppose the closest superlative I could give is "transparent".
Regards,
Owen
Endorsing a particular cartridge as being the "standard" would be problematic. What we really need is a generally accepted average. This could easily be approximated by averaging the impedance of the top 10 best selling carts (10 MM and 10 MC) from DC to 40kHz and defining an equivalent circuit (R+L) that comes closest.
I can definitely see how the practice of shorting the inputs could lead to confusing results, or results that are much better than they would be if an appropriate load we inserted, especially with MM carts and pre amps when it comes to input current noise.
Regards,
Owen
Interesting!
I ordered a few this evening to test. They are enormously expensive for an op-amp, but still worth a shot, at least for the first stage.
It would be a very compelling solution for someone wanting to use both MM and MC carts without needing two preamps.
Regards,
Owen
Hi Owen,
frequent swapping of cartridges is one important feature to me, searching a phono amp.
Actually for measuring purposes of different cartridges, record players.
That is why I am looking for an op amp based design. (low noise and dist.)
Also, the availabilty of a PCB for ease of build, is important.
Guess, I found s.th.
The frequent swapping would require a passive switch of input R and C. Well, I can imagine that. Soldering in new parts is too time consuming when the task is to compare two cartridges.
And the possiblitiy of adjusting gain, to cope with different output voltages.
Say there is a loud MM and a low output MC with a difference of, say, easily 20dB, how could they be adjusted to have the same level at line output? If possible at all with that design.
Might be esier, better to do that in the line level domain anyway? (not the volume pot though...)
Thinking loud and asking questions at the same time.
Thank You.
I do like the balanced, symetrical, differential design.
Looks beautiful, too.
Best
Thomas
that was easy
What I had in mind was a concept similar to the EMT Preamp JPA 66.
It has 4 phono input all of which have indiviual level control and load capability for each input. Convinient.
If you just switch cables load and gain have to be adjusted all over again.
As I said for a measurement setup that is not practical enough.
For this build I want a 'feature rich' pre amp. I do have minimalist (and) tube phonos. None ot them has switchable or selectable input loads. Not to speak of 4 inputs etc.
Best
Thomas
As I said, I want to be able to switch between cartridge inputs with the correct load and gain for each input already set.
That might be two MM, or two MC or one MC one MM. Some will be used more often, others only once. One input might be connected permanently.
To suit these demands, I do not want to plug cables to one single input and then dial in the correct load and match gain. That will take at least 6 or 7 seconds...
Again, for a reference of the 'surrounding' features I want to build around this PCB, check the EMT JPA 66 features.
Not only as listening system, but as a part of a measurement system.
Anyaway, back to actual question:
is it possible or does it make sense to adjust gain in one of the stages of 'The Wire' balanced phono stage?
Thank You
Best
Thomas
Got my board today.
Interesting question. From the above discussion about noise (thanks for the spreadsheet!) I'd assume the second stage (R43) would be a good candidate, alternatively the third stage (R44).
I'm also interested in a more in depth look at this.
I found the above in the BOM. Is there an ongoing discussion about a group buy on the forums?
Cheers,
Sebastian.
audiothomas said:
Interesting question. From the above discussion about noise (thanks for the spreadsheet!) I'd assume the second stage (R43) would be a good candidate, alternatively the third stage (R44).
I'm also interested in a more in depth look at this.
opc said:
I found the above in the BOM. Is there an ongoing discussion about a group buy on the forums?
Cheers,
Sebastian.
hello fellow wires!
i also ordered this board and will soon begin the build. however i would like to ask your opinions on using a single ended power amp (lm3886 based).
i have researched some strategies:
strategy 1
INA137. is the INA137 up for the task? what are your opinions on this one?
strategy 2
modifying the power amp for receiving bal input.
strategy 3
something like a transformer (have not looked deeply into this)
i am aware that i could be nullifying the advantages of a bal preamp, but this is all i have for the moment...
br
tituman
i also ordered this board and will soon begin the build. however i would like to ask your opinions on using a single ended power amp (lm3886 based).
i have researched some strategies:
strategy 1
INA137. is the INA137 up for the task? what are your opinions on this one?
strategy 2
modifying the power amp for receiving bal input.
strategy 3
something like a transformer (have not looked deeply into this)
i am aware that i could be nullifying the advantages of a bal preamp, but this is all i have for the moment...
br
tituman
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