My Dad owns the 770 80 Ohms too and the Darkvoice seems to run them just fine. Also I wonder how much power and Trans conductance you’d need to OTL a Planar? The La Figaro + 5998 seems to work well with Planars, but could that be taken further with 6528s? The La Figaro Can’t Handle 6528s by the way in case you ask, the transformers funny enough are actually SMALLER and for a lower VA rating at just 80, I guess when they made the La Figaro they made it very particular in it’s design. Makes Sense since Pentodes are MUCH more efficient that Triodes.
6528 tubes are very unique for many reasons…I find it very interesting that they work decently with planars. Most planars Ive seen work well on a tube amp is a hybrid tube of sorts or an otl hybrid with rectifier tubes.
Reason be the Trans-conductance reducing Output Impedance, especially on amps running two of these with Both Triodes per channel. 5998 tubes seem to be about double the Transconductance of a 6080, and a 6528 is much more than a 5998. Drawback is finding a Transformer that can handle 5 Amps at 6.3 V, and that’d only power the 6528, let alone the Driver tube. I think the Zana Deux does one better and uses 6C33Cs which uses a whooping 6.67 Amps of Current at 6.3 Volts and that’s just a single triode tube!
O Forgot to mention but I’m in the middle of building an OTL with this concept in mind uses 2 Transformers capable of Outputting 7 Amps @ 6.3V which is well more than enough for a Driver and 6528.
1 Like
I have heard many positive things about the Zana Deux and if I remember correctly, Tyll was big fan and owned one as well.
Clean power is very important to Tube Amps as well. But one doesn’t need to spend an arm and a leg. I have a simple Furman M-8x2 power conditioner surge protector and that did make a difference with my DarkVoice…but mostly because my power lines in my hourse are old from the 1950’s, so it isn’t the cleanest. Power conditioners aren’t unicorn dust and don’t fix most problems, but my use case this time around it made a difference eliminating some buzz and hum.
Interesting. I have very rudimentary knowledge of circuitry as I am an accountant by trade, but learned mostly through the audio hobby as well as my hobby as a Bassist/Drummer/Saxophonist…so very rudimentary. It is a subject I wish I had more interest in when I was younger so I could have gotten into the field…accounting is boring (but pays to well to consider a career change at 39 years old, lol).
I got a Furman PST-8 and it seems to help a bit but not much, got it at a discount though on Amazon so not bad. Also I’m no expert either, I’m building it based on alot of amps that I’ve found Build Guides for and schematics and stuff, Not so much of a science more of a “Ok, so if it didn’t blow up in this amp it won’t blow up with these parameters”. I mean I’m Majoring in Psych atm but a friend gave me an old Aviation Repair Book and simply taught myself how not to die a horrible, shocking death due to electronic malpractice. I mean I manged to make my Darkvoice work (after many, many, many burns and shocks) really well, I mean, “How Much harder is it to build one myself”. If I die make sure to quote that as my Epitaph or something. I’ll probably post pics once it’s done and not on fire.
Oh also forgot to mention, the Prototype worked fine, but now I’m stepping it up by using Shunt Regulators (Like the Crackatwoa/Mainline) and increasing the power by going from a 6J5 to 6SN7, also increasing the Voltage output from the power supply by reducing R 1 on the Secondary Amp a bit which will help since I’ve heard the Regulators lower voltage. I mean the Prototype was capable of running 600 ohms at about a third of it’s Max Volume (may add some Grid resistors though).
1 Like
That is super interesting. Keep me posted once you started building. Would make an interesting VLOG in my opinion.
I’m sure once I get the funds to acquire my bottlehead crack and build it, I will become much more confident in my skills on the matter. But I will say, the DarkVoice is a really good choice as a starter tube amp. I learned a hell of a lot from just doing the Fitz mod and tube rolling.
1 Like
Definitely keep at it and I wholeheartedly agree to getting a Crack Starting off. The Darkvoice was my first tube amp, loved it, modded it, and loving it more, but it’s a pain in the ass to mod and Rebuild due to how the case makes it hard to fit your hand in. Besides the Crack has more depth in it’s case allowing for a variety of things like Chokes and High Capacitance Film Caps in the PSU.
Oh you can also paint the wood and stuff. If you buy the Crack, build it first with no Speedball and Later with Speedball. I put Speedball in my Darkvoice but didn’t like the outcome and switched back. Give the Crack a Listen First without the Speedball, then add the C4S and see how that sounds, then add the Speedball Board and listen to it again, see how you like the different components and their effects.
Also while the Speedball didn’t give me the sound I wanted with the DV, the DV also has a different Power Supply with a lower resistance but a lower Secondary Voltage as well as different current and other stuff, so don’t get disheartened because it I didn’t like it in the DV cuz while similar, both have different concepts on how to power their tubes.
That was the plan, no speedball first. Being able to paint the case is very interesting as I am a big fan of woods and different types of stains, so that gives me some ideas.
Still deciding if I want to go Wood or Aluminium on my amp. Kinda leaning towards wood since the damn thing will be so massive heat might not be an issue. Anyways I’ll leave that for another time I guess, got homework and stuff and wanna get some sleep early. I’ll post some pics of the internals and other stuff when the rest of the stuff comes in. Thing’s gonna weigh more than 25 pounds though (The Late Section Power Supply Transformers weigh 12 pounds alone, let alone the Chokes at about 8 pounds and the “Warm Section” Early Power Section which alone weighs another 5 pounds), but the power output and sound, as well as it’s volume adjustment range and other small tidbits will more than make up for it.
At that point might put wheels on it, tie a rope to it and call it a portable tube amp . . . I might need a generator too. Oh well all in the name of Audiophilia.
2 Likes
Been loving my new 7193 tubes. Got the Ken-Rads and National Union. Probably gonna try to find the mullard mitchum cv6 or hytron e1148 next. Lemme know if you have them and wanna get rid of em.
5 Likes
Dope Tubes, I have GEC 7193s but they’re SUPER microphonic, shame though because they do sound great.
I made my La-Figaro a 6J5 re-socket (instead of using 6SJ7 pentodes), even have the singular adapters for 7193s, but they’re SO Microphonic, even my Darkvoice with the Dual Adapter has issues (albeit much less).
I just stick to the RCA 5692 and Bendix 6080 Combo for my Darkvoice and all is well.
1 Like
@Schizoid I spent a lot of time looking for tubes I liked and I’m finally satisfied with these but now I’m wondering what I can do to improve sound. I was looking at the mods and it seems like the line out one would substantially improve the sound quality, would you say it’s something easy to do without prior soldering experience?
Line Out one? Are you talking about the one on SBAF where they disconnect the Preamp Output? Sorry, never heard of a line out mod. If you can tell me abit more of what the line out mod is.
Honestly if you want to improve the sound best bet would be to put in better Capacitors on the output (replacing the red ones on the board). That mod is a bit of a doozy though when I did it, since the board on mine was pretty weird to unscrew and then put back into place. Also the capacitor size matters so make sure to take that into consideration. Since those caps are at the output they make quite a bit of difference. Changed mine with Mundorf caps and the amp sounds more refined honestly.
Hum Fitz is also a good beginners mod that makes the Darkvoice more quiet, but may make it louder depending on the capacitance of the caps used with higher capacitance introducing more gain (may be good or bad depending on what you want). Make sure to get good Capacitors for this mod. 25V 220uf ELNA caps we’re good, until I changed the transformer out for a better, In spec for 120V Mains one, it made the Hum-Fitz mod a bit redundant afterwards.
Another mod would be to replace the diode at the middle of the amp (Bridge Rectifier) with Cree diodes kinda like they do in Bottlehead Crack Mods. Essentially it’s removing the diode and replacing it with a board and somehow fitting it somewhere in the amp, but the upside is better bass response (from what I could tell) since those diodes are a faster at switching. This mod though is not for someone new to soldering since getting the diode out is a bit hard if you don’t want to damage it. If that doesn’t matter though you could always get closer in but maybe melt it a bit accidentally, making it easier to remove without that consideration.
You can also replace the last capacitor of the power supply (the 820/1000uf one) as well as the last cap of the Driver tube plate power supply (the two 220uf ones on either side) with equivalent film/ higher quality electrolyticcaps for overall better sound as well.
Also removing the Preamp section helps as well, and also replacing the cathode biasing resistors of the Driver tube with LEDs, and maybe buying Vishay resistors for the Cathode of the power tube too (replacing the big gold ones with better big gold ones).
Easiest mods though are the Cathode LED replacing the resistor in the small tube, the Hum-Fitz mod, and disconnecting the Preamp Output by cutting it out. There is a SBAF article about Darkvoice/Cracks mods that also recommend other things like better grid stoppers and stuff: (https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.superbestaudiofriends.org/index.php%3Fthreads/darkvoice-and-crack-mods.5621/&ved=2ahUKEwi-2Y2qyonnAhXpxlkKHQavAKwQFjAAegQIAxAB&usg=AOvVaw3tyRAFM_-beZ5J62jSlFzO)
Idk hopefully some of this helps out, although I recommend that even with the easiest mod requiring soldering being the Hum-Fitz mod that you practice a bit beforehand, maybe by soldering wires together to get a feel for how soldering actually works.
Soldering is essentially heating up what you want combined until the actual solder metal (usually a tin/lead mix) can fuse with whatever you’re combining. The solder has to be melted obviously, but the wires ALSO have to be hot as well in order for them to fuse with the solder better and ergo to each other. Also take into account what is being soldered, since resistors for example can expell heat quickly, it may take a while to solder a resistor to a wire if the soldering iron isn’t heating it up as quickly as the resistor is dissipating heat. Especially the big aluminum ones since those can probably expell lots of heat before the leads of the resistors can fuse with the solder correctly.
Idk take your time with this so you don’t mess anything up, do some soldering exercises first before doing Hum-Fitz, then maybe think about tackling the Red Output Capacitors on the PCB since those have the most noticeable effect on sound besides tube rolling, but only after you’re sure you can solder correctly, rather not damage expensive capacitors especially those dead center on output of the signal.
2 Likes
Thank you so much for the detailed reply, I will thoroughly read everything to make an informed decision. The line out mod I was referring to is explained in this link: https://www.superbestaudiofriends.org/index.php?threads/darkvoice-and-crack-mods.5621/
He said that “it lifted the veil”, so I figured it would be a substantial difference. That being said I have no idea how he did it so I figured I’d ask lol
Thanks again for all the info!
1 Like
Yeah that’s the mod I was referring to when I said about cutting the Preamp out, just cut the wires to the Preamp and everything sounds a bit better, since the Darkvoice has no dedicated switch for HP output or PA output, they’re both essentially working at the same time, as well as some other issues in that section. Also it’s a bit more effective to also remove the Capacitors and the resistors from that section too, but just cutting the wires is fine as well.
Oh also building my own amp too, and just to get the idea of how much is being put into this thing, here’s the output capacitor of one of the power supplies to rest of the circuit, hopefully it doesn’t go boom after I power it on.
1 Like
Oh god, did I just link you the same thing 
Maybe I’ll try my luck with the pre amp mod!
Really curious to see how your project turns out. Did you already make a thread for it? Either way I would love to see pictures of the process!
Yeah the Preamp mod is as simple as opening the amp and cutting the wires. Just make sure that the wires aren’t touching the chasis after you cut them, maybe make them a super short cut. You WILL lose the preamp output of the Darkvoice however, so take that into consideration. Oh also make sure the Capacitors are drained. Cutting the wires isn’t an issue, but accidentally touching a charged power supply and you’re in for quite a shock.
Also haven’t started yet since I’m waiting in the enclosures for the Power supply and amp sections. I’ve made sure to calculate everything as best as I can so it should function without issues.
Oh also the amp will have switches for the Heaters and for the B+ supply, essentially a super simple soft start, where the tubes heat first, then the high voltage is applied with a secondary switch (the switch is after the transformer but before the diodes since AC is easy to have a switch for, while a DC switch at similar voltages will start a fire/go boom. The tubes aren’t super high voltage though most is maybe ~170-180V, so a more complicated circuit like something on a relay isn’t that important for this thing.
Oh also it’s fully OTL and will be taking advantage of a transformer capable of heating the 6528 tube for low OTL output impedance, although my headphones are T1s and HD600s and other High Impedance stuff, so it really doesn’t matter too much (Argons though and I want a super OTL baby to push them without getting into 6C33C tube territory, they can melt solder from how hot they can get, so oof).
You’re really going off there, I respect the dedication. Unfortunately, I’m just starting getting into this so most of this goes over my head. But thanks to your help I’ll be doing my first mod on monday by (hopefully successfully) cutting off the preamp. I’ll make sure to google how to drain the capacitors beforehand!
I mean when I started, I drained the Capacitors using a light bulb, as long as the terminals are making a good connection with the bulb you should see it light up then dim as the Capacitors drain, then check with a multimeter. 12V or less is safe but check all of the Capacitors since I’ve gotten shocked a few times since one of the Capacitors in the stock Darkvoice wouldn’t drain unless you drain it directly. A 150-200 DC (AC is more lethal) shock from a capacitor with low capacitance isn’t lethal in most cases but it is painful. Oh also never put your left hand in an amp since a right side shock isn’t as likely to be lethal as a left side shock if you do get a shock since that can hit your heart and it can stop it.
Seriously the mod may seem simple but ALWAYS take precautions, like isolating yourself from ground with rubber soles (Crocs are almost always rubber so that helps) and checking all Capacitors with a multimeter. If you want to be proactive, adding a high resistance bleed resistor of about 200kohm ~1 or 2 Watts across the last terminal of the power supply capacitor will almost assure a full drian after shutting the amp off. I’m quite a bit paranoid so if something is up to spec, I like to overspec it a bit when possible, such as resistor wattage and other stuff.
Stay safe and I hope your Darkvoice provides some good training for soldering and into Amp circuitry. Srsly though, hope it turn out well but work safe.
1 Like