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Would you happen to have a pic of the power supply and MPX boards(901 and 502)?
Here you go.
In the power supply, at location C12, the schemo has 1000uf, 50v. I currently have a Nichicon HE 2700uf,50v there and it sounds great. I was wondering...I have two Black Gate 1000uf,50v caps. Would paralleling them at C12 work? There is enough trace to drill two holes to fit the 2nd cap and enough room on the board to shoehorn it in. What do you think? I can get a Black Gate FK 2200uf, 63V but the seller is asking an exorbitant price for it. Black Gates are becoming very rare and more expensive. Supposedly the Audio Note owner in England is working with Rubycon to make him a Black Gate equivalent.
The Nichi HE is a very good, low ESR cap and just about perfect for that location, if it were me I'd leave it where it is. Paralleling two smaller caps does have some theoretical advantages, even lower ESR, but in this application, I've not "heard" any improvements when tried on other tuners.
If you want to experiment try a couple of Panasonic FR or FM caps and connect the leads above the board using the existing through holes. That way you don't have to drill the board and you can see, hear, any differences before you start drilling holes .
Just my $.02, oh and I've never heard or experiences any issues in using a BG "N" in a feedback loop.
The Nichicon does sound excellent in that location so I will leave it there for now, especially since you feel that paralleling wouldn't make a difference. I did replace R3 resistor with the Dale wirewound you recommended. The original resistor was still spot on at 91 ohm, but I went ahead and replaced it anyway.
Thanks for all your informative and helpful information.
Hoosier, I noticed that on the de-emphasis caps C9-14 you replaced only two of them with polystyrene. Any reason you did this?
I was just correcting the total capacitance for a 75µs time constant. I wasn't concerned with the 50µs setting and made the correction at one location for each channel.
I was wondering which caps and resistor are for the 75us? Also, did you hear an improvement with the Ammons adder board and filters? Bill emailed me with a quote and said there are two filters, the GAXX being the low one with least distortion.
75µs uses all the caps:
The Left Channel is R4 & C9/10/11
The Right Channel is R5 & C12/13/14
Remember that there are consequences in changing out the filters. It will pretty much require an alignment after the change-out. There is one 3 pin and 1 4 pin filter in there. The 4 pin is equivalent to 2 3 pins. What Bill typically does is give you a matched set of 3 GDT filters, and with his adder board which has enough gain to compensate for the insertion loss of the GDTs. If I remember correctly the GAXX filters are GDT types.
I hope that makes sense.
The resistors were way off, reading 5.5K. I put in two KOA Speer 1W, 6.2K that read 6.12K. The improvement was huge. I then found I needed to add 330pf to get a final reading of 74.3 us. The highs are now greatly extended; bells, cymbals,etc. sound much more extended and dynamic. Thank you for this recommendation.
...I would have to ship the tuner somewhere to have someone professionally do this. I had it aligned a few years ago.
Since I don't have the equipment to test for that, I suppose I'll leave well enough alone for now.
If you have a decent multimeter you can get close enough. pull the caps and measure their capacitance. It wouldn't surprise me that one or two will be off spec. Do the same for the resistor. the calculation is pretty straight forward.
To calculate the time constant for each channel you need to know the R in Ohms and the C in µf. Using the schematic values. 3 X .0039 = .0117, then .0117 X 6200 = 72.54µs. You're just trying to get close to 75µs.
Once you know the actual values you can calculate and correct as required.
Use poly styrene or propylene for replacement caps and a metal film for the resistor.
Hope that makes sense.
If you can't get it exactly at 75us with the calculations, is it better to be slightly under or over the 75us?
I don't believe anyone can hear the difference between 73 or 76. Consider that the OEM theoretical came in at 72.5 and no one seems to notice. Throw in 5% parts at the receiving end and who know what at the transmitting end and you begin to appreciate how subtle these deviations are..
It's not unusual to see mid 70s tuners go with a 65µs de-emph, halth way between 50 & 75 and it not that apparent.
Get it close and you'll be fine.
Yes, I was curious why H/K had their schemo specs on the deemphasis set at 72.5 us( and that's assuming perfect tolerance) but I would imagine it was because of the parts cost and tolerances available at the time. I am going to take out the caps and resistors soon and do some measuring to see where it currently stands. I'm sure that between the old parts and new 1% parts I'll be able to get tighter tolerance readings. Thanks for your input.
Thank you, sir. I have a good multimeter and can do this. So exactly which three cap locations are we talking about? I see that C10 and C11 are two of them and resistors are R4 and R5, which are 6.2K. I have two 1/2W Speer KOA reserved for there.
The Left Channel is R4 & C9/10/11
The Right Channel is R5 & C12/13/14
In the de-emphasis circuit is it important that the .0039uf polystyrene caps are of audio quality or is the main importance the precise value in order to get as close to 75us? Thanks.
Not to start a was here but in "general", please note the qualifier, any film & foil cap like the poly styrene, or polypropylene, even mylar are better than a lytic. The ones in there now are 5% mylars. IMHO any film cap that gets you to the total capacitance required, for the size of the resistor, so you end up with 75µs will be fine.
Let the flames begin.
Everyone has their favorite caps when it comes to sound. I'm aware that the factory caps are mylar, but I was only questioning if the cap was more crucial to audio vs. just a decent cap that had the required capacitance to combine with the resistor value to come as close to 75us as possible. I have ordered some polystyrene film and foil as that is what I saw you used. If the stock caps are on spec then I might just leave them in as the tuner sounds really good right now. I have read that mylar does have a tendency to go out of spec with age. That's my next project. Thanks!
No worries, rest assured that the flame quip was not directed at you, and to answer you question directly, which I failed to do , yes any polystyrene will do, the concern here is the total capacitance vs. resistance.
Since I had the 18 out on the bench and I'm an incurable tweak I had the audio board out and was just looking at the condition of the solder joints in general. To my surprise I found a bunch of cracked joints at the blue board connector at the bottom of the board. Had to re-solder about a third of them. Which put me on a witch hunt on the rest of the boards.
You should check yours also and see if its just mine or a generic issue. Don't forget the power supply.
Thanks for the heads-up. I will definitely check the older solder joints. I have done everything except to check out the de-emphasis setting on the caps and resistors. It sounds so good now that I'm hesitant about changing anything. I'm an incurable tweak as well and I can't tell you how many times I've had things sounding great but made some changes for the worse and sometimes too many changes can make it very difficult in finding the change that made the sound worse. I have learned the hard way to make small changes, listen for a while and if the change is better, move onto the next change.
Hoosier, I see that you replaced the resistor R3 on the power supply board. The schemo shows 91R, 1W. Can you tell me what brand and value you used(black resistor) and your reason for replacing this resistor? Mine is still original. I was thinking a KOA Speer carbon film would work well there, but I can't find a 91R in 1 or 2W.
I used a Vishay/Dale wirewound 3W from Mouser PN 71-RS2B-91
Replaced it because it was slightly out of spec and, got hot and just because I was in there already.
I really appreciate you taking the time to post these. By the way, you helped walk me through modding a Sansui Tu-9900 a few years ago. I got it to sounding really good, even better than my Citation 18 tuner, but I couldn't leave well enough alone and ended up further tinkering with it and did something where it won't power up now. I don't have the electrical knowledge or equipment to trouble-shoot the problem. If you ever have some free time on your hands and feel like fixing it for me, I would gladly pay you for your services and time.
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