[L0rdGwyn]

Speaking of future designs...

@L0rdGwyn great work, looks fantastic. Pretty much the mods i did years, but yours looks the part... mine only sounded it.

Crazy idea... there is enough room on those PCBs to fit the edcor 10k tx..... maybe....

Cool idea! But are those Edcors gapped to take 80-100mA on the primary? Otherwise, would have to cap couple to them anyway, so not sure that would be an improvement, unless you had something else in mind?

This got the gears turning though, could be interesting to load the cathode follower with a low turns ratio output transformer, maybe 2:1 or 4:1 to lower the output impedance further, although they would be large to handle 100mA without saturating, also wouldn't be an OTL anymore I might explore this idea.

 

[DeweyCH]

BTW, what the EFF is with all of the freaking heat shrink in the DarkVoice?!! Every tube pin? Every soldered connection? REALLY? My god, absolute insanity.

Just had to get that off my chest. All of the glue and heatshrink in this amplifier is maddening.

A-freaking-men. Total novice here and even I think that's absurd.

 

[bcowen]

Nope, it is a completely different tube, higher transconductance than even the 5998.

https://frank.pocnet.net/sheets/077/7/7802.pdf

>>>>>>>as everyone rushes to Ebay looking for 7802WA's <<<<<<<

 

[bcowen]

BTW, what the EFF is with all of the freaking heat shrink in the DarkVoice?!! Every tube pin? Every soldered connection? REALLY? My god, absolute insanity.

Just had to get that off my chest. All of the glue and heatshrink in this amplifier is maddening.

Yeah, supreme overkill without any doubt.

I will say, however, that the soldering work (at least in my amp) was done quite nicely, and far better than most other things I've seen coming out of China.

 

[L0rdGwyn]

>>>>>>>as everyone rushes to Ebay looking for 7802WA's <<<<<<<

Unfortunately, these are truly unobtainium

 

[bcowen]

Very doable. Reach out to Bill. He should be able to provide assistance with tubes fulfilling your emotional and physical needs.

Yes, but I have a different situation here. Whenever tubes are mentioned in some derogatory or rolled-eyed tone, all I have to say is "shoes." The conversation is immediately directed to something other whine-able topic.

 

[bcowen]

Unfortunately, these are truly unobtainium

Well thanks for teasing us then. I'm not buying any more tubes so just speaking for the other guys, of course.

 

[DeweyCH]

Oh finally I got the front panel off (haven't had much time to play with this lately) and replaced the power switch. I'm just gonna let those eight hex screws hold the front panel in place from now on. I ended up having to drill out that last screw.

Physical connections (IE non-soldering stuff) are back in place. Tonight I shall solder. Really, this time.

Edit to add: I did decide not to pull the output cap PCB and replace those. Just... too much.

 

[SHIMACM]

I've really enjoyed the pairings of HD6XX (sold), Beyer T1.2 (sold) and now ZMF Auteurs with the DV. Also some old-school AKGs - mid- and late-production Sextetts.

Really nice pairings all.

I have T1 (1st Generation) and I was always in doubt if Darkvoice was capable of amplifying it to its maximum potential.

I've always been curious to listen to hd6xx on Darkvoice, but I haven't had the opportunity yet.

You had the two headphones, how do they compare on Darkvoice?

 

[DeweyCH]

I have T1 (1st Generation) and I was always in doubt if Darkvoice was capable of amplifying it to its maximum potential.

I've always been curious to listen to hd6xx on Darkvoice, but I haven't had the opportunity yet.

You had the two headphones, how do they compare on Darkvoice?

It's hard to make a comparison, I sold the Senns long before I bought the Beyers. I also got the Beyers at a point where my DV had been modded a bit and had better tubes. Both sang like birds when fed by it.

 

[DeweyCH]

BTW, what gauge wires do y'all use when replacing the internal wiring? I kind of specifically wonder about @L0rdGwyn 's green twisted wire from this post. Or does it even particularly matter?

Could I actually use speaker wire?

EDIT: Never mind, I figured that bit out. 14 gauge solid-core grounding wire. Got it.

 

[bcowen]

BTW, what gauge wires do y'all use when replacing the internal wiring? I kind of specifically wonder about @L0rdGwyn 's green twisted wire from this post. Or does it even particularly matter?

Could I actually use speaker wire?

Depends on which wiring you're referring to. Different gauges needed at different points. For the heater wiring, 20 gauge is probably sufficient (although @L0rdGwyn should feel free to correct me if not), but you would NOT want to use traditional "speaker wire" there unless you can twist the two strands together. The twisting is needed to cancel noise as the heater wiring is carrying AC current.

 

[L0rdGwyn]

Okay, going to try to explain how you go about center-tapping and elevating the heaters of the stock DarkVoice.

Please read in full before making any changes, be sure to understand what you are doing before you do it. If you are unsure if what you have done is correct, take a photo and PM me or post in the thread and tag me. Carry out these modifications at your own risk, there is ~200VDC inside the amplifier, working with high voltages carries a shock and safety hazard.

Heater Center Tap

What you will need:

• 2x 100ohm 1/2 resistors (type does not matter, metal film would be fine).
• 1x 2K 1/4W resistor
• 1x length of 20AWG wire (solid or stranded does not matter)

1) Find the two points on the main PCB where the heater wiring is soldered, here.



2) Solder one end of a 100ohm 1/2W resistor to each heater winding pad. Twist together the opposite ends and solder them together, like the illustration below. This is the center tap point!



3) Break the ground connection between the 6SN7 heater and the ground bus below. This wire can simply be cut or desoldered and discarded.



If you are elevating the heaters, skip to step 6. If you are not, go to step 4.

4) Now connect a piece of wire from the new center tap point to the ground bus. This is the long, thin length of bare wire that runs throughout the chassis.



5) Because the power LED is run from the heater supply and we have just halved the voltage it sees, we must adjust the series resistance before the power LED. On the power LED PCB, there are two 2K resistors, one on top and one on the bottom. Add the additional 2K resistor in parallel with the top 2K resistor. This means the leads of the new resistor will be soldered to the same pads as the existing 2K resistor.

If you are not elevating the heaters, you are done, the hum should be improved but might not be completely eradicated.

Elevated Heater Supply

You should have just finished step 3 and created the virtual center tap and broken the heater ground connection at the 6SN7 socket. To elevate the heater supply, we must make a voltage divider from the B+ supply to reduce its voltage to our desired elevation voltage. Anything from 30V-60V will work fine. This elevated voltage will be applied to the center tap point.

Additional items you will need:

• 1x 220K 1/2W resistor (type does not matter)
• 1x 100K 1/2W resistor (type does not matter)
• 1x 10uF 250VDC electrolytic capacitor (these Vishay / Sprague axial caps will work fine: https://www.mouser.com/ProductDetail/Vishay-Sprague/TVA1504/?qs=sGAEpiMZZMvwFf0viD3Y3aqMjiJTbj4RWQfU45X0ilM=)
• 2x additional length of 20AWG wire (solid or stranded does not matter)

6) Find the below power supply capacitor, the second to last in the supply (note this can be done with either capacitor in this position, they are all in parallel). This is the point at which you will connect the voltage divider. The B+ at this point should be roughly 150V, although I would not be surprised if it varied between amplifiers given the quality of the transformer, the end result will be the same.



7) To the newly created center tap point (the junction of the two 100ohm resistors), solder one end of the 220K resistor, one end of the 100K resistor, the positive end of the 10uF electrolytic capacitor, and one end of a 20AWG length of wire.

8) Solder the other end of the 100K resistor and the negative end of the electrolytic capacitor to the ground bus, shown in step 4.

9) The other end of the 220K resistor must be connected to the positive end of the power supply capacitor shown in step 6. If the leads are long enough to reach from the center tap point to the positive terminal, it can be done this way. Otherwise, connect the other end using an additional length of 20 AWG wire.

10) Disconnect the power LED PCB from the ground bus, shown below. The wire can simply be removed from the PCB and the excess clipped.



11) The power LED PCB ground must now be brought to the center tap point so the power LED does not see the elevated supply DC offset. Connect the length of wire connected to the heater center tap to the power LED ground PCB pad.

The wiring should look like below, another crude illustration.



12) Lastly, as in step 5, the series resistance before the power LED must be reduced so the LED will light up. On the power LED PCB, there are two 2K resistors, one on top and one on the bottom. Add the additional 2K resistor in parallel with the top 2K resistor. This means the leads of the new resistor will be soldered to the same pads as the existing 2K resistor.

That's it, you should now have ~45VDC heater elevation, the hum present on any noisy tubes should now be gone.

 

[L0rdGwyn]

BTW, what gauge wires do y'all use when replacing the internal wiring? I kind of specifically wonder about @L0rdGwyn 's green twisted wire from this post. Or does it even particularly matter?

Could I actually use speaker wire?

EDIT: Never mind, I figured that bit out. 14 gauge solid-core grounding wire. Got it.

Depends on which wiring you're referring to. Different gauges needed at different points. For the heater wiring, 20 gauge is probably sufficient (although @L0rdGwyn should feel free to correct me if not), but you would NOT want to use traditional "speaker wire" there unless you can twist the two strands together. The twisting is needed to cancel noise as the heater wiring is carrying AC current.

14AWG is way overkill, 20AWG for heaters will work just fine, should be a nice tight twist. Solid is better for this as it keeps its shape better than stranded. Take two equal lengths of wire, attach one end of them to a vice, attach the other end to a power drill and twist slowly while gently pulling taught with the drill.

 

[Damok]

I have never been so disappointed in a product before but there is something wrong with my Darkvoice. It arrived a few days ago and the first day was just amazing on the stock tubes, I had a great time just listening to music and relaxing. I swapped the tubes after a few hours and went back to listening and everything was amazing. I turned it off and went to bed for the night, I woke up and turned it back on and started letting it arm up while I read my morning emails. I plugged in my headphones and started listening, I heard a weird loud popping noise out of the left ear and then the nothing out of the left channel. The right channel was still going and as I went over to turn it off it popped again and turned back on, I thought it was a weird glitch but it just kept happening every 1-2 mins. I swapped back to the Stock tubes as maybe that was the issue but no, I still get this horrible pop in the left channel and it goes silent for a bit then randomly pops and comes back on.

Has anyone experienced this and is the whole thing just f'ed or is there something I can do to fix it?