Yaqin CD3 / Darkvoice 336SE Mods (Coupling Caps)

[blairfrischx]

I've been debating swapping the capacitors in the Yaqin SD-CD3 I have to something more reputable. I was wondering if anyone could recommend a capacitor to try that would actually fit in the limited space.

For reference, here (link) is the insides. The blue blocks are what I'm talking about. There are 2x0.22uF and 4x0.47uFcapacitors corresponding to the input and output, respectively.

I was leaning towards either Mundorf Zn or Clarity Cap SA, if they fit. I was also considering testing the Dayton Audio caps since they are cheap and might be worth playing with.

I'd also like to extend this thread to mods on a Darkvoice 336SE to avoid making two separate threads. For reference, here (link) are the insides of that.

Attachment is the closest thing I have to a representative schematic of the signal path based on Google and visual inspection of pictures.

Some things I'd like to do to that include:

• Swapping signal path resistors with precision resistors
• Swapping 20W chassis-mount resistors to higher quality resistors
• Adding cathode bypass cap
• Swapping output coupling caps (3x10uF film per channel) with a larger nonpolar electrolytic (possibly bypassed with a film)
• Swapping headphone jack and potentiometer
• Swapping preamp output coupling caps (1x0.47uF film per channel, similar to the CD3) with a different film
• Possibly redoing wiring with something more substantial, if I feel adventurous.

Anyway, I just wanted to know if people had any suggestions for coupling capacitors to use in either application, specifically. Any input is appreciated.

[zingo]

Clarity Caps are hard to beat, and with those values, they should fit in the stock location fine.

[blairfrischx]

The two electrolytics that don't have their values filled in in the schematic above are 220uF/250V.

I am leaning heavily towards the Clarity Caps. They are about $5 per cap for those sizes. Also leaning towards 100uF Mundorf Bipolar caps to replace the output caps on the Darkvoice.

Here (link) is a picture of the inside of the Darkvoice 336SE I actually have. The picture I linked above is from Google. The one I have is from what seems to be an earlier production run where they still had a PCB for the big filter caps, and they still seemed to love hot glue. That'll be a bit of a pain to work around.

[blairfrischx]

Parts list so far is looking like:
For the Yaqin CD3:
4x Clarity Cap SA 0.47uF
2x Clarity Cap SA 0.22uF

For the Darkvoice 336SE:
2x Clarity Cap SA 0.47uF
2x Mundorf E-Cap100 100uF
2x (Each) PRP 1% 1W Resistors (1K, 2K, 10K, 1M)
2x (Each) Kiwame 1% 2W Resistor (200R, 30K)
2x Vishay/Dale 1% 25W Resistor (1K)
Alps 100K Blue Velvet Potentiometer

Some things I haven't quite decided on yet:
Maybe new RCA jacks.
Maybe replacing the 220uF/250V caps with nicer Nichicon ones.
Power supply capacitors/resistors

Does anyone have any comments on implementing a cathode bypass capacitor? I would probably use a Elna Silmic II, but I don't know what value or voltage.

Also, does anyone have any comments on using a film to bypass the Mundorf E-Cap? The only other person I've seen using the E-Cap in a Darkvoice amp had it bypassed with an Obligatto film; not sure if it's something I should be looking to do.

Attached shows planned circuit specs (really just has different coupling cap values and a cathode bypass cap), though some values are missing at the moment.

[blairfrischx]

Orders are placed.

I'm using Sonicap Gen I caps in the Yaqin CD3.

Parts list for the Darkvoice is:
2x Clarity Cap SA 0.47uF -- preamp output coupling
2x Mundorf E-Cap100 100uF -- headphone output coupling
2x Clarity Cap SA 1.0uF -- headphone output coupling bypass
2x Sonicap Gen I 4.0uF -- to test against the Clarity Cap
2x Nichicon Fine Gold 100uF/25V -- to test as cathode bypass
2x Elna Silmic II 100uF/25V -- to test against Nichicon FG

2x (Each) PRP 1% 1W Resistors (1K, 2K, 10K, 1M)
2x (Each) Kiwame 1% 2W Resistor (200R, 30K)
2x Mills MRC50 50W Wirewound (1K)
2x Mills MRA12 12W Wirewound (200R)

[blairfrischx]

I started taking the innards of the Darkvoice apart tonight.
Some things that were accomplished:

• Removed PCB on filter capacitors. 200R/10W resistors removed (slated to be replaced with Mills 12W)
• Removed gobs of hot glue on input/output wiring and between coupling capacitors
• Desoldered input/output wiring from RCA jack PCB. Removed jacks and PCB (slated to be replaced with nicer jacks and nicer wire)
• Removed big ugly red coupling capacitors (slated to be replaced with Mundorf 100uF bipolar + Clarity Cap SA 1uF)

I haven't yet done any significant work on the bunch of wiring surrounding the tube sockets. That will all be replaced with high-quality solid-core wire down the road. I also need to figure out how to remove the faceplate so that I can replace the headphone jack and potentiometer. I'll probably go with a nicer Neutrik jack and an Alps Blue Velvet pot (debating using 100k instead of 250k). Once I figure out how to systematically disassemble the amp, things will go much faster (not necessarily more smoothly )

It's a work in progress. I'll probably swap the capacitors in the Yaqin this weekend to some Sonicaps. That should be significantly easier than working inside the Darkvoice.

Regardless, I'm having fun.

[heiney9]

Pics...........we need pics

H9

[blairfrischx]

Here (link) is a collection of pictures I took of the insides before I started taking it apart. I will have to take more photos of what it currently looks like inside later.

[blairfrischx]

Alright, here (link) is another gallery of photos. I got the largest PCB out of the chassis (with the coupling caps, etc.) so I could work on it separately (since just about everything on it is being replaced). The smaller Clarity Caps aren't actually going to be used right now, since they are too big. I will be using some 0.47uF/200VDC Sonicap Gen II's instead.

Darkvoice apparently trimmed the leads on the transformer really short. That's gonna be a bit of a pain to work around - about on par with the hot glue all over that PCB. What a mess.

I'm at a stopping point for now because the tip of my finger caught the side of my desoldering iron.

[blairfrischx]

Made a bit of progress tonight, packing that PCB with new components. The through-holes where the old resistors were were a little small, so I had to get somewhat creative with how to pack them in. I'll end up having the same problem with the Clarity Caps (their leads are at least 16AWG, and those holes look like they won't fit under 20)

Picture of the PCB

Once this is done, I'll have to start taking apart and replacing the wiring and resistors that are point-to-point inside the amp. That should actually be somewhat easier, not having to work around the limitation of desoldering/resoldering a PCB.

Honestly, the most difficult things forthcoming will be replacing the headphone jack and potentiometer. I have yet to figure out how to get access to them.

[DefQon]

Nice mods going on there mate. With regards to accessing the pot and headphone jack. You'll need the appropriate sized tip hex (allen) key to remove all 8 hex screws on the faceplate. Once removed you have full access to the bolted on volume pot and hp jack by removing the washers.

With replacing the pot, make sure you don't end up ordering some custom stepped or ALPs pot as it could end up being too long to fit, especially since the P2P wiring to the front 6SN7 tube cramps things up a bit.

Just another question, what will you be replacing the 6 x 10uf filter caps with?

[blairfrischx]

Nice mods going on there mate. With regards to accessing the pot and headphone jack. You'll need the appropriate sized tip hex (allen) key to remove all 8 hex screws on the faceplate. Once removed you have full access to the bolted on volume pot and hp jack by removing the washers.

With replacing the pot, make sure you don't end up ordering some custom stepped or ALPs pot as it could end up being too long to fit, especially since the P2P wiring to the front 6SN7 tube cramps things up a bit.

Just another question, what will you be replacing the 6 x 10uf filter caps with?

I figured those 8 hex screws on the faceplate were the key to it, but just by inspection I couldn't tell how to take it apart. I also didn't have the correct size allen key on hand. Thanks for confirming my suspicions, though! And welcome to Club Polk.

I will be replacing the 3x10uF caps per channel with a 100uF Mundorf bipolar electrolytic cap, bypassed with a Sonicap Gen I 8.9uF film cap. I've heard of one other person using the Mundorf bipolar caps (though they used an Obbligato film as a bypass) to good effect.

[DefQon]

I figured those 8 hex screws on the faceplate were the key to it, but just by inspection I couldn't tell how to take it apart. I also didn't have the correct size allen key on hand. Thanks for confirming my suspicions, though! And welcome to Club Polk.

I will be replacing the 3x10uF caps per channel with a 100uF Mundorf bipolar electrolytic cap, bypassed with a Sonicap Gen I 8.9uF film cap. I've heard of one other person using the Mundorf bipolar caps (though they used an Obbligato film as a bypass) to good effect.

Thanks...

Some pictures would be great. I already have mine fairly modded but the filter caps is something I have not replaced yet as I only use the amp to drive my high impedence HD600's and few other can's.

[blairfrischx]

Thanks...

Some pictures would be great. I already have mine fairly modded but the filter caps is something I have not replaced yet as I only use the amp to drive my high impedence HD600's and few other can's.

I've been updating as I've worked my way through the process, including some pics. Above your first post is a picture of the filter cap PCB that I took. It doesn't have the larger Sonicaps in place yet. I'll probably be updating on Friday or Saturday with that board being completely done.

Because the transformer leads were cut so short, soldering them back on to the PCB might prove to be a huge pain. I've been playing with the idea of adding some extension wires onto them to make it easier.

At the end of my mods, I think the only stock things inside will be the tube sockets (though I've honestly debated buying new Belton sockets to drop in) and the electrolytic filter caps along the V+ line.

[zingo]

Enjoy the process! As a guy who's modded many piece of equipment, you don't gain much in resale value, but it's good experience and usually some nice gains in sound quality.

[blairfrischx]

Enjoy the process! As a guy who's modded many piece of equipment, you don't gain much in resale value, but it's good experience and usually some nice gains in sound quality.

I'm certainly enjoying the process! I've done cable mods before and built the main amps I use in my stereo system (actually I cheated a bit, because those amp boards were pre-built; I just swapped some resistors), but this is the first time I've gone in and done a comprehensive set of mods on an already-assembled piece of equipment.

The people over at Darkvoice didn't make it very easy with their early production runs; they used PCBs in places where it didn't make a whole lot of sense (e.g. on the RCA jacks and on the filter capacitors) and hot glued a lot of things in place. It's a while away, but I'm excited to get it back it reassembled and back in commission.

[blairfrischx]

Pretty cool update: I stripped everything out of the inside except for the tube sockets, headphone jack, potentiometer, LED PCB, and electrolytics.

Some pictures

Now I start the slow process of filling it back up with stuff. That requires some parts that haven't shown up yet, but the general process should be pretty straightforward working from front to back in the amp. Uninsulated wire and associated resistors first, then insulated wire, etc. I'll have pictures as I work through the process.

[blairfrischx]

I still can't for the life of me figure out how to get the face plate off. It seems like there are four screws from the inside of the amp holding it on, not the eight hex key screws surrounding the volume knob. Only three of the hex key screws had nuts on them, and none of them seem to just come out with counterclockwise rotation, as if they aren't actually in a threaded hole. I'm trying to push them from the other side while unscrewing, but it's a bit difficult. Just FYI, they fit 2mm and 5/64" allen wrenches.

I attempted to remove the chassis that carries most of the components of the amp (what the tube sockets are attached to), since it is also held on by four screws, but they are rather soft and tightly fastened, and one of them is now stripped. That tray is actually in the way of accessing three of the hex-key screws from the faceplate.

Here (link) are some pictures illustrating what I'm talking about. If anybody has any suggestions (looking at you DefQon - might have to message you on Head-Fi), they'd be much appreciated.

Still having fun, though. It's gonna be pretty quick once I actually figure out how to replace the potentiometer and headphone jack... Who would've thought the wiring would be the easy part compared to actually disassembling a chassis?

[blairfrischx]

Still wrestling with the front plate. I would have loved it if it had been attached by four hex key screws, just like the back plate. That would have been beautiful.

I finished putting components on the filter cap board and finally got new RCA jacks. Turns out that they fit perfectly, so now they just kinda get to hang out on the back panel with the IEC inlet until I get to them near the very last steps of the process. Either way, they're pretty.

Pictures (link)

[blairfrischx]

I decided to take a break from the Darkvoice for a bit, thinking that focusing on the Yaqin CD3 might give me something to do for a few days. As it turns out, swapping the coupling caps in the CD3 ended up just about the easiest thing I've ever had to do with a soldering iron. It took all of half an hour to heat up, replace six caps, and cool down.

Picture of final product

[blairfrischx]

Got all of those stupid hex key screws out of the face plate, finally. It is still attached by something (maybe just adhesive, maybe those screws I mentioned several posts up).

I ended up actually going with a Noble 100k potentiometer instead of one from Alps or a Chinese-made stepped attenuator. It should be here Friday, by which point I should be able to start wiring again.

I actually stumbled upon what appears to be the stock pot when I was browsing PartsConnexion for a new one; it looks to be made by Connex (link).

Faceplate without volume knob or screws

[blairfrischx]

Turns out the pot I bought (Noble 249Y) is too deep by about 1.5mm and runs into the front tube socket.

While this would typically be cause for cursing and generally angry behavior, I've found a workaround! Namely, swapping the positions of the headphone jack and potentiometer on the front of the amp.

The potentiometer (provided I drill a hole for the little nub thing they always have) would fit where the headphone jack originally was with 1-2 mm of clearance between it and the bracket for the 220uF electrolytics; likewise, the Neutrik headphone jack I've bought has tons of free space in the center of the chassis without interfering with the tube socket, provided I make the hole in the front of the chassis slightly larger to accommodate the screw that the headphone jack uses.

I think it may just work out in the end. This is nothing compared to the other problems I've had. It just requires a little bit of mechanical work. I have some time to consider my options. This doesn't require any sort of reworking of the aluminum faceplate, in theory. In practice, these things could work out entirely differently.

And this is why I like DIY projects.

Here (link) is what it would look like from the front. No knob, as they are still on their way to me. It looks a bit more assymetric than the "stock" look, but it is technically superior in terms of components.

Bonus pic: Comparison of potentiometer sizes

[trav0810]

I have a CD-3 myself, so I am really interested to hear how that turns out.

[blairfrischx]

I have a CD-3 myself, so I am really interested to hear how that turns out.

I've already finished the mods on the CD3 up here. I have to say, the upgrade was worth it to me. It was painless, and it had what I would describe as a tangible effect on the sound - benefits of a quick turnaround time on modding and getting it back in place.

Really, the biggest effect I've noticed would be in vocals. The Sonicaps are generally described as having a tangible "midrange bloom", and I have to say I agree in this case. It was a very good upgrade over the stock film caps in terms of vocals.

[blairfrischx]

I haven't been able to make any progress on this lately, since I've been waiting on a shipment from Parts Connexion.

In the meantime, I discovered I had an ALPS 100k sitting around in an old amp I built, so I have options now: use the ALPS pot and stock headphone jack in stock locations, or use the Noble pot and Neutrik jack in non-stock locations.

To keep myself entertained, I did resistance readings for all 22 detents of the Noble pot and a similar number of positions on the Alps pot in order to check which tracked better.

Here (link) is album of the results. I might do the same readings for the stock pot eventually, but it didn't seem like a good investment of time since I'm replacing it regardless.

Just based on that, it would seem that the Noble performs better throughout much of the spectrum, especially the upper end. But regardless, both perform well (no more than 4% deviation between channels). Oh well, it was something to do. Now, if only the Canadians and USPS would hurry up.

[zingo]

I hate to be a bit of a bummer, but the Sonicaps are rated at 200V, and the board states those caps should be at least 275V. I'd hate for you to have any problems with that high voltage path.

Thanks for posting all the updates and pictures as I recently picked up the Grant Fidelity B283 MKII which is a very similar design to your CD-3. I'm going to be upgrading the caps as will, and just ordered a set of ANSAR Supersound PPA caps to swap in. I already installed a matched pair of 1952 Raytheon 6SN7 to replace the stock Chinese tubes, and am very pleased with the sound quality compared to my B1 buffer.

As it turns out, swapping the coupling caps in the CD3 ended up just about the easiest thing I've ever had to do with a soldering iron. It took all of half an hour to heat up, replace six caps, and cool down.

Picture of final product

[blairfrischx]

I hate to be a bit of a bummer, but the Sonicaps are rated at 200V, and the board states those caps should be at least 275V. I'd hate for you to have any problems with that high voltage path.

Thanks for posting all the updates and pictures as I recently picked up the Grant Fidelity B283 MKII which is a very similar design to your CD-3. I'm going to be upgrading the caps as will, and just ordered a set of ANSAR Supersound PPA caps to swap in. I already installed a matched pair of 1952 Raytheon 6SN7 to replace the stock Chinese tubes, and am very pleased with the sound quality compared to my B1 buffer.

I had that same concern with voltage before I swapped them. I took a multimeter and poked around inside before I went through with it. The highest voltage I could find was ~175V at the first filter electrolytic. Voltage at the coupling caps during operation wasn't even 100V.

I've had it running for probably 20 hours since I swapped caps, and I haven't run into any problems yet. I'm tempted to think they used 275V based on availability, not necessity. Feel free to correct me if I interpreted measurements incorrectly and should swap capacitors again to something with a higher voltage rating.

I'm currently running a matched pair of brown-base Sylvania 6SN7WGTs. I have to say I enjoy the tube buffer in my system.

[zingo]

If that was the measured voltage than I wouldn't be to worried about it. Is there a difference of voltage at different operating points and loads? Obviously overshooting on the component voltage rating will never hurt, but as long as you are exceeding the voltage of the circuit, no problems!

[blairfrischx]

I was testing with it on my desk between my DAC and headphone amp, just so I could be sure it didn't see significantly higher voltages during normal operation. I couldn't find anything that would indicate that 275V was necessary.

Speaking of voltage measurements, I did similar ones for the Darkvoice to see exactly what the high voltage supply is and what voltage the coupling caps see. It runs at a slightly higher voltage (~200V) compared to the CD3, but the voltage at the coupling caps was still only 70-75V. Other people who've modded it verified that 100V caps work just fine here. What's more worrisome there is that the main supply filter caps are 820uF/200V, meaning that one is constantly running essentially right at its operating point. Why they would design the amp like that instead of opting for 250V caps, I have no idea. I've been shopping around for caps to replace them.

On a completely unrelated note, Parts Connexion apparently missed that I sent payment for my order 10 days ago, so they only got around to shipping today. Maybe all of last week was a Canadian national holiday.

[zingo]

What's more worrisome there is that the main supply filter caps are 820uF/200V, meaning that one is constantly running essentially right at its operating point. Why they would design the amp like that instead of opting for 250V caps, I have no idea.

This is one reason I prefer to buy Chinese equipment with the Grant Fidelity name on it, even used like this buffer. Ian and Rachel ensure not only that the product does what is advertised and that the circuit is accurate, but also that it is not dangerous or troublesome.