Hi again Ed,
NO, as said this cap mod isn't 1 to 1 and reuires fiddling / adaptating
If I follow your pm your are likely to go for the CD 940. If so, here is my experience again, but that is just me and won't apply to other caps. Each time 1 cap per channel of course... and for all these caps you will need to make one leg longer and bend the legs / fiddle to get them on the board as they aren't intended to be mounted verticaly, but I guess you understood all that already. Hot glue or blu tack is your friend in case of...
The first cap, 0.22uF cap, fits in terms of size, diameter and wires, is slightly elevated due to the bent legs.
The second cap, 1uF, needs to be somewhat elevated and then can fit verticaly on top of the trim pot while releasing a gap 'as the first cap) for resistors etc. I found that using the right hole (out of a choice of two) allowed to center these caps a bit more against each other so that all fitted (access to trim pot, stability, Korg visible)... see my pix. The legs of that second cap needs to be ground off with sand paper or similar to get 0.5mm ish smaller so they can fit into the mounting holes!
The 3rd cap, 3.3uF doesn't fit in a satisafctory manner on the board (I am building an extension board) and its legs are way too big. More per PM: first determine IF you really need a 3.3uF cap there as that depends mainly on the input impedance of your power amp, so no general value here (1st and 2nd caps are different on that as purely Korg related) and you could get away with smaller ones, perhaps...
Hope this helps
Claude
NO, as said this cap mod isn't 1 to 1 and reuires fiddling / adaptating
If I follow your pm your are likely to go for the CD 940. If so, here is my experience again, but that is just me and won't apply to other caps. Each time 1 cap per channel of course... and for all these caps you will need to make one leg longer and bend the legs / fiddle to get them on the board as they aren't intended to be mounted verticaly, but I guess you understood all that already. Hot glue or blu tack is your friend in case of...
The first cap, 0.22uF cap, fits in terms of size, diameter and wires, is slightly elevated due to the bent legs.
The second cap, 1uF, needs to be somewhat elevated and then can fit verticaly on top of the trim pot while releasing a gap 'as the first cap) for resistors etc. I found that using the right hole (out of a choice of two) allowed to center these caps a bit more against each other so that all fitted (access to trim pot, stability, Korg visible)... see my pix. The legs of that second cap needs to be ground off with sand paper or similar to get 0.5mm ish smaller so they can fit into the mounting holes!
The 3rd cap, 3.3uF doesn't fit in a satisafctory manner on the board (I am building an extension board) and its legs are way too big. More per PM: first determine IF you really need a 3.3uF cap there as that depends mainly on the input impedance of your power amp, so no general value here (1st and 2nd caps are different on that as purely Korg related) and you could get away with smaller ones, perhaps...
Hope this helps
Claude
dunno for your side of pond
I didn't look , but there must be some other manufacturer and there must be tons of caps , even if polycarbonat caps never were in majority.....
last time I bought 1K pieces locally ........ learning from Papa - always buy plenty, then you're getting good price , think later how you're going to use them
I didn't look , but there must be some other manufacturer and there must be tons of caps , even if polycarbonat caps never were in majority.....
last time I bought 1K pieces locally ........ learning from Papa - always buy plenty, then you're getting good price , think later how you're going to use them
Assuming the energy storage inside the 75-24V Meanwell LRS power supply is equivalent to a 17,000 microfarad capacitor charged to 24V (others can offer different opinions about this),
then a 2.0K ohm resistor, connected from +24V to ground, will dissipate 95% of the stored energy in 100 seconds. Use a resistor rated for 1 watt or more.
Where did I get that energy storage figure? By torturing the numbers found in Mean Well's datasheet, attached.
_
then a 2.0K ohm resistor, connected from +24V to ground, will dissipate 95% of the stored energy in 100 seconds. Use a resistor rated for 1 watt or more.
Where did I get that energy storage figure? By torturing the numbers found in Mean Well's datasheet, attached.
_
Receiving some PM on that PPP topic, so just for info...
The 2 PPP caps I mentioned here in my test cost a total of 10E (or $) at Mouser. That's per channel of course.
The third one cost that alone but you may not need the same high value as me, or just leave that one and replace just 2 caps per channel.
So to get all the 4 CD 940 PPP caps you can see in the picture I attached with my post it will cost you roughly 20$. Average cost is 5$ per cap.
As said, quite a lot of money for "caps" and much more expensive than the initial proposal. On the other hand, I felt this is money well spent, still a reasonable amount in absolute terms and to get that Special Edition extra sound I am sure manufacturers would easily charge a few hundred $ extra.
There are of course other options, other makes etc., plus bypassing caps also etc.
I went for CD 940s because I wanted to try them personaly, because I felt they were likely to be close to the "reasonable ultimate" (no real compromise soundwise, so say a reference) and I wanted that last one for me (best sound garantee without trying too many different options) but also because I wanted here to report on sonic differences between caps options in form of recommended standard vs say a PPP reference.
From a financial POV it didn't make any sense in my case as I needed the 2 options to do the comparison and knew that one, the less good sounding to my ears (there is no bad sounding here!), would be for nit anyway - but then others can benefit from that experience and decide where to draw a line.
And again there are many options, for all kind of tastes, beliefs and budget, that's DIY
Have fun experimenting
Claude
The 2 PPP caps I mentioned here in my test cost a total of 10E (or $) at Mouser. That's per channel of course.
The third one cost that alone but you may not need the same high value as me, or just leave that one and replace just 2 caps per channel.
So to get all the 4 CD 940 PPP caps you can see in the picture I attached with my post it will cost you roughly 20$. Average cost is 5$ per cap.
As said, quite a lot of money for "caps" and much more expensive than the initial proposal. On the other hand, I felt this is money well spent, still a reasonable amount in absolute terms and to get that Special Edition extra sound I am sure manufacturers would easily charge a few hundred $ extra.
There are of course other options, other makes etc., plus bypassing caps also etc.
I went for CD 940s because I wanted to try them personaly, because I felt they were likely to be close to the "reasonable ultimate" (no real compromise soundwise, so say a reference) and I wanted that last one for me (best sound garantee without trying too many different options) but also because I wanted here to report on sonic differences between caps options in form of recommended standard vs say a PPP reference.
From a financial POV it didn't make any sense in my case as I needed the 2 options to do the comparison and knew that one, the less good sounding to my ears (there is no bad sounding here!), would be for nit anyway - but then others can benefit from that experience and decide where to draw a line.
And again there are many options, for all kind of tastes, beliefs and budget, that's DIY
Have fun experimenting
Claude
And again there are many options, for all kind of tastes, beliefs and budget, that's DIY
Have fun experimenting
Beautifully said!
Hello,
The multipair cables are twisted to limit their sensitivity to interference and crosstalk.
In the case of RCA base, I ask myself some questions in order to choose the most efficient:
1 / Should I twist the cable of the left channel RCA with the one on the right and make a common mass?
2 / Do I have to twist together the common ground cable with the right / left cables already twisted?
3 / Do I have to twist the ground cable of the RCA with the input cable of the same RCA then do the same for the left one?
Thank you for your answers,
Christophe
The multipair cables are twisted to limit their sensitivity to interference and crosstalk.
In the case of RCA base, I ask myself some questions in order to choose the most efficient:
1 / Should I twist the cable of the left channel RCA with the one on the right and make a common mass?
2 / Do I have to twist together the common ground cable with the right / left cables already twisted?
3 / Do I have to twist the ground cable of the RCA with the input cable of the same RCA then do the same for the left one?
Thank you for your answers,
Christophe
Not sure it is the best way, but that's what I did and despite no casing it works now very well on these hot summer days...
- RCA: I connected all grounds together, signal only goes to source switch, so no twist there and single / exposed... well short anyway and enough hassle
Indeed on that particular case left and right are "quite twisted", but well
- from switch I run signal only output to volume pot but that is indeed with each channel twisted with 'its' ground (note all cable grounds run to one star point)
- pot to board traditional twisted cables signal+ground
- same for output, so the output RCA are connected by the board and don't have connected grounds like the others... but I haven't properly investigate that RCA output on my reference system
The twisted pairs came handy already twisted, courtoisie of the Cat 6 cable...
Coax cables might be better (are for sure for shielding per se), but I always had a problem with symmetry as ground is in fact part of the signal so like same wires...
Bonne chance
Claude
- RCA: I connected all grounds together, signal only goes to source switch, so no twist there and single / exposed... well short anyway and enough hassle
Indeed on that particular case left and right are "quite twisted", but well
- from switch I run signal only output to volume pot but that is indeed with each channel twisted with 'its' ground (note all cable grounds run to one star point)
- pot to board traditional twisted cables signal+ground
- same for output, so the output RCA are connected by the board and don't have connected grounds like the others... but I haven't properly investigate that RCA output on my reference system
The twisted pairs came handy already twisted, courtoisie of the Cat 6 cable...
Coax cables might be better (are for sure for shielding per se), but I always had a problem with symmetry as ground is in fact part of the signal so like same wires...
Bonne chance
Claude
From a financial POV it didn't make any sense in my case as I needed the 2 options to do the comparison and knew that one, the less good sounding to my ears (there is no bad sounding here!), would be for nit anyway - but then others can benefit from that experience and decide where to draw a line.
And again there are many options, for all kind of tastes, beliefs and budget, that's DIY
Even when you decide to shoot the moon on your budget, you will still
spend only a small fraction of what commercial product costs.
Indeed Papa!
That little preamp is a fabulous gift and excellent value for money!
I felt a trully small fraction of the "big money not spent elsewhere if going commercial" could at least be spent as extras on the B1 KORG... it deserves it.
Having said that, you deserve even more another fraction, be it wine or food - please shout if around Paris one day...
Claude
That little preamp is a fabulous gift and excellent value for money!
I felt a trully small fraction of the "big money not spent elsewhere if going commercial" could at least be spent as extras on the B1 KORG... it deserves it.
Having said that, you deserve even more another fraction, be it wine or food - please shout if around Paris one day...
Claude
The ACA kit arrived Friday. Just finished it, plugged it in, and to my surprise... it actually worked! Beginners luck. Sounds great powering my office B&W bookshelf speakers. Plenty of power for them. Time to put some hours on the amp.
But now I need the Korg Preamp kit to become available for the front end!! I'm using an iFI Nano IDSD black for the Pre currently and they seem to get along pretty well.
But now I need the Korg Preamp kit to become available for the front end!! I'm using an iFI Nano IDSD black for the Pre currently and they seem to get along pretty well.
Hmm, will let the experienced boys reply but reading Papa my understanding is he went for the 24V and the indeed highish 16dB gain for sonic reasons. It seems to be pretty key, not saying it wouldn't work of course, just it might diverge quite a bit from the initial mean.
Of course I could be wrong and the usual suspects will answer for sure better than I did
Claude
PS: note a very small regulated offboard wall wart PS as the one I use is around 25$ and in your case easy to implement as you just have to drill for a small PS plug... job done.
Of course I could be wrong and the usual suspects will answer for sure better than I did
Claude
PS: note a very small regulated offboard wall wart PS as the one I use is around 25$ and in your case easy to implement as you just have to drill for a small PS plug... job done.
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I have used two of these "passive preamps" so far. Into one I built my Aikido line stage, into the other Wayne's BA2018 linestage. In both cases, I have used an external PSU, which is what I would recommend to do. The control logic needs at least 12V AC or DC, a bit more is better. 15V DC for the control no problem, because it has its own regulators. I use separate rails / regulated voltage lines for audio and for control.
The preamp module works flawlessly, albeit with some low-level noise spikes, that can be seen on a spectrum analysis, stemming from the control logic circuits, presumably. Most pronounced at volume level 65 and somewhat higher, not recognizable below, inconsequential at volume levels higher than 90 or so.
I suppose this gets translated through the relays into the audio signal.
Nothing audible through 100 dB/w speakers at volume levels that will actually be used. No signal and volume control fully open, a very faint electronic whine could be heard with my ear at the driver. But at these levels, I probably would blow out the drivers instantly with a signal.
Soundwise and functionality-wise I'm still very happy with them.
Best regards, Claas
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