Hi Hans,
The boards are still waiting test. Captive breeding experiment #6 is still not sleeping through the night and I am resisting mission creep on the phono functionality. I realised that, thanks to a few additional purchases the 3L-R setup is preferable so I need to change a few parts (which are on order). I may risk wrath of wife and lash up temporarily. I also need to get the second set to LD ASAP.
The 6i6 was partially bought to back off some of the mission creep as I can implement functions digitally instead of having to build more stuff up. At least that is the theory!
The boards are still waiting test. Captive breeding experiment #6 is still not sleeping through the night and I am resisting mission creep on the phono functionality. I realised that, thanks to a few additional purchases the 3L-R setup is preferable so I need to change a few parts (which are on order). I may risk wrath of wife and lash up temporarily. I also need to get the second set to LD ASAP.
The 6i6 was partially bought to back off some of the mission creep as I can implement functions digitally instead of having to build more stuff up. At least that is the theory!
I have a question. As I get around to experimenting with different ways of hooking cartridges to the 6i6 (and by inference other homestudio type equipment) I want to keep all the info together. Does it make more sense to put it here where the circuits are or start a new thread and cross-link?
OK, Thanks. Just to recap, the average bit of gear we are looking at has 3 types of input
1. Mic, balanced usually with Phantom power
2. Instrument (unbal)
3. line in (balanced)
Idea is to gather together various ideas of how to hook cartridges up to these. I was initially going to write off the instrument input as it's noisier than the mic one, but as it's a high-Z input there are a couple of simple things that might work so worth a check (i.e. 47k resistor in parallel).
1. Mic, balanced usually with Phantom power
2. Instrument (unbal)
3. line in (balanced)
Idea is to gather together various ideas of how to hook cartridges up to these. I was initially going to write off the instrument input as it's noisier than the mic one, but as it's a high-Z input there are a couple of simple things that might work so worth a check (i.e. 47k resistor in parallel).
And just when I thought I would start with the easy one (mic input) first step is the manual. The spec for mic input impedance in the manual is 2kOhms. I'm not sure I want to blindly accept that but trying to think of an easy way that someone with minimal test tools could do.
I guess you could just sweep and see with a test record but that's slightly clumsy as you have several unknowns?
I guess you could just sweep and see with a test record but that's slightly clumsy as you have several unknowns?
Bill,
Here you can see what happens with Rin=2K. I suppose you will be using a DAC and a digital correction.
The image top right shows a FR when Rin=47K in Green, when Rin=2K in Blue and when you discard the 75usec Riaa time contstanr with Rin=2K in Red.
Left image above shows the FR for an adjusted Riaa correction with Rin=2k, the circuit diagram is shown below.
Hans
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Hi Hans,
I was going to experiment with (as discussed earlier in this thread) loading to get the 75uS pole, but musing over how one could easily check if the spec input impedance is correct. What I haven't yet done is look at the sensitivity to this, so if spec is 2k and its 2k5 does that make big odds. I'll go off and do that as it might not be an issue.
I was going to experiment with (as discussed earlier in this thread) loading to get the 75uS pole, but musing over how one could easily check if the spec input impedance is correct. What I haven't yet done is look at the sensitivity to this, so if spec is 2k and its 2k5 does that make big odds. I'll go off and do that as it might not be an issue.
To get the 75usec pole, depending on your Cart you should aim for a load around 6K or L/R=75usec.
I used two JFET followers on a floating 9V battery (split by two big R's to make a false ground) drove the 2K mic inputs fine, there is DC at the source but they are always AC coupled. You can then use any cart termination you want.
Scott,
With the in between buffer your solution can use the full set of Riaa time constants in the digital filter and it is still possible to experiment with a lower Cart termination giving a pole at 75usec and leaving this time contant in the digital filter.
It would be nice to know if this results a an improvement in sound reproduction.
I suppose you used something like this for the buffer: Designing a universal diff-in/diff-out Head Amp
But why then are you using a battery instead of the phantom power ?
Hans
For 1 meter connections the pseudo-balanced/single ended connection worked fine. Of course this is also the simplest way one FET and three resistors per channel and some bypass caps.
Had to go off and bang my head on a wall for a bit as was being stupid as usual. I think that both a buffer and straight in should be tried. I might even for a giggle try my microtrackII if I can get it working mainly as this has no published specs* for the mic input and also has the least compliant phantom power known (about 30v apparently).
Based on what we have found from test records +/-1dB is as good as it gets and so worrying about the exact input impedance is a waste. OTOH phantom powered buffers will offend so many delicate souls it's worth doing just for the fun value
*The user manual has no figure, but on the web have found a couple of references to the mic input being '>5.3k'. That's sooo helpful.
Based on what we have found from test records +/-1dB is as good as it gets and so worrying about the exact input impedance is a waste. OTOH phantom powered buffers will offend so many delicate souls it's worth doing just for the fun value
*The user manual has no figure, but on the web have found a couple of references to the mic input being '>5.3k'. That's sooo helpful.
I am watching this thread with much interest as I just took delivery of a Behringer UMC202HD. Promptly realized I have no 1/4" adapters and the local pro shop wants $15 per. I can wait a few more days to hook it to while some online-bought adapters make their way to me. I would rather buy local but not when they are ripping me off for cables and adapters.
I bit the bullet ten years ago and bought 4 of every adapter I could think of, even BNC to RCA in both flavors. Sometimes I need to series them like differential BNC to XLR.
Trying to pull some info back onto here that appeared on another thread.
PHLUX-II active phono cartridge is what appears to be a rebodied AT95 with a single ended amplifier board soldered onto the cartridge pins. This has encouraged me to think about Scott's balanced phantom powered concepts and if we could make a board small enough to go at the headshell. (Whether we should bother is a secondary question compared to the fun of trying). I rapidly realised that, for the balanced case this will be beyond the average DIYer in the first instance (inc me) but a board that goes inside the TT or just outside could be of interest.
To which point the first challenge is picking the FETs as many of us just don't have the sort of junk box Scott has and . LSK389/489 I just cannot find in small qty outside ebay in europe. So leaves it really to the onsemi products particularly the 2SK3557. Any reason not to baseline that for MM duties? Tad pricey at 23p each in 10 off but cheap enough so as not to worry hunting for anything else?
PHLUX-II active phono cartridge is what appears to be a rebodied AT95 with a single ended amplifier board soldered onto the cartridge pins. This has encouraged me to think about Scott's balanced phantom powered concepts and if we could make a board small enough to go at the headshell. (Whether we should bother is a secondary question compared to the fun of trying). I rapidly realised that, for the balanced case this will be beyond the average DIYer in the first instance (inc me) but a board that goes inside the TT or just outside could be of interest.
To which point the first challenge is picking the FETs as many of us just don't have the sort of junk box Scott has and . LSK389/489 I just cannot find in small qty outside ebay in europe. So leaves it really to the onsemi products particularly the 2SK3557. Any reason not to baseline that for MM duties? Tad pricey at 23p each in 10 off but cheap enough so as not to worry hunting for anything else?
Looks like a BF862 substitute so it should be good here. I'll see what might work all SMT and tiny. I don't see the need to make it flea power as they seem to have.
EDIT - ~$16/100 at Mouser >6000 in stock.
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Hi Bill,
Farnell has a huge assortment of NFets, through hole and SMD.
https://nl.farnell.com/webapp/wcs/s...5001&langId=31&categoryId=700000004636&sf=721
However, when using the 47K termination, you really have to add a capacitance. This will be a bit more difficult when mounting a buffer on the Cart.
The other thing to realise is that the unit needs power. Depending on SE or Diff, 2 or 3 extra wires will have to go through your Arm to the Cart !!
You could use phantom power either from your 6i6 unit or from a 9 Volt battery, but in both cases you will need relatively bulky Electrolytic 47uF caps that could make your PCB quite heavy.
In that case you would need a second PCB to take care of the supply side and to connect to the cables from the 6i6.
All in all, a PCB in the TT Cabinet directly after the Arm seems to me quite a bit more attractive to realise.
Hans
Farnell ran out of stock and report that they are no longer in production.
A shame for this fantastic low noise NFet.
Hans
Hi Hans,
Yes it was the big caps that made me realise that phantom powered mini boards were, whilst possible NOT DIY. I do want to try your phantom MC headamp sometime as well.
On the 2SK3557 Digikey have 10k and farnell claim more stock in april so hopefully will remain supported for a while!
Yes it was the big caps that made me realise that phantom powered mini boards were, whilst possible NOT DIY. I do want to try your phantom MC headamp sometime as well.
On the 2SK3557 Digikey have 10k and farnell claim more stock in april so hopefully will remain supported for a while!
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