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In Reply to: RE: Black Gate N caps for tuner posted by sherod on June 18, 2016 at 12:20:16
You didn't say what size they were and how many you have, 10µf hopefully, the final sig path coupling caps are C10 & C20 on the audio board. Post back if that's not what you have.
Here's a picture.
Did H/K use carbon film resistors throughout? I see you replaced four(two blue,unknown brand, and two Vishay/Dale) on the audio board. Was this done to improve sound or to replace OOS ones?
As far as I know, yes all are carbon films. The replacements in there are both metal films. I like the Dales but am not married to them , I think the others are Yageo.
I've been revisiting the audio buffer board for the last couple of weeks and have made a few changes that I'm still getting a feel for, sonically. That board is/are true dual mono, discretely formed, differential amps. You literally can cut the board in half, plug in both halves and everything would be fine. What it doesn't have is a balance circuit, if my rudimentary understanding is correct. To that end, I'm trying to understand how unbalanced components in each amp affect the audio and if matched halves can be of benefit.
Here's a question for you. On the MPX board have you replaced C3 with a film cap?? Its a ceramic now and its directly in the signal path. If you haven't, you should.
...with the results. With a polypropylene cap the sound is so much cleaner and more focused. Thanks for the recommendation, John.
...with balancing the circuit, please let me know. Anywhere I can improve the sound of the Citation 18 tuner is great for me. It is one of my primary listening sources, at least until I can get my Sansui TU-9900 back up and running.
...that C3 still had a ceramic cap in it. I wonder why H/K put a ceramic in that location? I'll put a good polyprop there. Thanks for the suggestion. I just ordered an adder board with the 3 GAXX filters from Bill Ammons.
Yea, old picture. There's a polystyrene in there now.
If I read the schematic correctly, C3 is 4700uf, 500v. Did you hear an improvement with the styrene cap? By the way, where did you find a good polystyrene with this large of value?
A polypro will be fine, since you've had an alignment, pull and measure the ceramic. Try to match the size of the ceramic with a film. That way you won't alter the separation adjustment. And yes the poly sounds better.
Is the voltage critical? I can't seem to find a decent polyprop that has 500v capacity.
Anything over 25V is fine. Should not be a problem finding a low voltage poly.
I haven't tested the capacitance of C3 cap yet but assuming it's + or - 20%, the only cap I can find with that high of capacitance value from the main distributors, Mouser, Digikey, Newark is a polyester. Do you have a source where you got your poly replacement? Thanks.
Since your's has already been aligned, I would pull and measure what the cap is now since the cap is in the adjustment circuit. Then match that value with the replacement cap or caps. Just get as close as you can to the current value. I looked at my notes when I did mine and that 4700pf ceramic actually measured 3960 and that's what I put in. If you're going to have it aligned in the future, put in the 4700 before its sent out to get back to the OEM nominal.
You may want to look here:
Thanks for the info. I have been confused. The schemo says that all capacitors are listed in uf, but you say this ceramic cap is 4700pf, not uf, correct? I plan on measuring it this weekend, but just wanted to make sure.
OK, in the metric system going from micro to pico means you move the decimal point 6 places to the right filling in the missing places with 0s.
The ceramic is clearly marked .0047, moving the decimal point yields 4700, which is indicated on the schematic.
I read on one of the threads that a ceramic capacitor can maintain its capacitance better at RF frequencies. Could this be why H/K put it at C3 on the MPX board? Just wondering...
Yes that's absolutely true, that's why you typically don't muck with the cap type in the front end, the key being RF frequencies, figure 100MHz for FM. Now once you hit the IF stage the frequency drops to 10.7MHz and then into the composite stage at about 55KHz which is where C3 lives, so no there's no good reason to use a ceramic there. More a cost and availability reason than a technical reason. IMHO
I see you put a poly cap at C15 on the MPX board. Besides that location and C3 are those the only locations you feel benefit from a film cap upgrade? I was curious where C15 was in the signal path?
C15 is part of the stereo switch filter, and on mine it was already a film cap. I did check for value, should be the same on yours.
...just as what is in the deemphasis. I haven't checked for value but was wondering if that location was critical for the sound.
No, not at all.
I have some polystyrene caps on order to put in that location.
I understand now and will measure and order accordingly. Sorry for bugging you so much. Even though this thread seems to be a private conversation between you and me, maybe someone else will see it and the info can help them out.
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.
I currently have in the BG N series values: 1uf,50v, 10uf,50v and 4.7uf,50v. I see in your picture that you put a 10uf "N" in C10 and C20. Any other locations where the "N" would be beneficial? I probably have a 1/2 doz. of the above values in N-series. Thanks.
OK, but just a work of caution, while the boards are decent the circuit traces are really, really delicate. Watch the iron temp and get in and out fast.
Starting at the IF board and strictly looking at the signal path,
C15 add a 0.047 polyprolylene bypass cap WIMA MKP2 is nice.
C4 add a 0.047 polyprolylene bypass cap WIMA MKP2
C17 & 19 The 10 would work there but I would go 22
C18 & 20 The 10s will be fine there
C5 & 15 The schemo says 1, the factory installed 4.7, on at least the 2 I worked on
C10 & 20 10s are fine there.
That's everything in the signal path.
I know you recommend increasing value from 10uf to 22uf at C17/19 on MPX board. Would 33uf be excessive in those locations as decoupling?
Yes a 33 will work, shouldn't be an issue at all. That's signal path not decoupling.
My schemo says there is also a 1uf at C22( I don't know if this location warrants a N cap. Also, there are 4.7uf at C21 and C24.
That's the signal feed to the headphone amps, so if you use cans
C21 & 24 10
C22 & 25 4.7
I'm going to do some experimenting.
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