Donald North Audio — Owners Thread

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by Huxleigh, Aug 12, 2016.

  1. m17xr2b

    m17xr2b Friend

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    Tube rolling falls in two camps broadly:

    1. The belief the operating point is critical for operation, 5% deviation is too much and all tubes sound the same when ran exactly the same in the same circuit as long as the specifications are respected.
    This is what the RT tube is, a basic 6N1P that in the Stratus circuit has the gain and current it should have. RT doesn't test the tubes exactly to the Stratus circuit but it's close enough.

    It's hard for me to believe they make such a difference, I've ran single plate output tubes, one pair testing over nos and another near emission failure. Couldn't hear a difference between them for casual listening. Still I have an open mind, maybe they do sound better, revelation it's not.

    2. The tube roller, trying everything under the sun to add flavour/coloration. I'm very guilty of this.
    Trying the ECC40 in the Stratus won't hurt but the circuit is not designed with it in mind. Ideally you want 3 to 5 times plate loading resistance. With 6N1P the Stratus has 5 times, the ideal value. With ECC40 it's only twice, not enough by anyone's standard. In theory you should hear more distortion but in practice I prefer some of the earlier ECC40 to the 6N1P or 1539.

    Let's put it this way, the 6N1P family will sound to their full potential while the ECC40 will not.

    Be careful with ECC40 adaptors. I've had three tubes die on me because of them. The tubes are quite fragile and some NOS bases need a bit of force to get them in. In my case the glass would fissure but not break immediately. One tube lasted tree days in the adaptor before vacuum was lost while running it(not in the Stellaris thankfully). If you have to push it in you'll break it. Tungsram seem more tough than the Holland made ones.
     
    Last edited: Sep 14, 2019
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  2. Claud

    Claud Friend

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    I bought one Tungsram and one Siemens and an adaptor on Ebay. So, m17xr2b, you sound like you have tried a ECC40. How did it sound? What are you using for a driver tube in your Super Stellaris?
     
  3. m17xr2b

    m17xr2b Friend

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    I've fixed my AVVT hum. Finally I can enjoy them without being reminded my amp hums.
    The heater wires are long and go under the rectifier board, I'm not sure why this is import with AVVT but spreading the positive and negative far apart and away from the heater board significantly reduces to 10% of what it was and makes it a non issue.
     
  4. m17xr2b

    m17xr2b Friend

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    I'm currently playing with C3G tubes and running a pair of C3GS(the selected higher transconductance ones). I had to make a small mod where I can't use 6BQ7A anymore but I didn't care for them anyway. The operating point is not quite ideal and is something I'm working on but the sound is very much up there.
    The 6N1P and ECC40 I found veiled in a way. Might be my hearing but I was yearning for more...extension, sparkle, air up top.
    [​IMG]
    Jac from Jacmusic hails it as the best input tube, I don't agree but it's up there. Soundstage is increased, detail takes a bump and I got the extension I was looking for. At this point I don't think the Stellaris is warm, it's the 2A3 and 6N1P that gives that impression. With PX4/AD1 and C3G it lacks any kind of warmth. It's super punchy, neutral, extremely fast, detailed and still muscial. Decay is still natural. I was expecting sterile, cold and detail freak but this wasn't the case.
    My adaptor arrived broken(I f* hate adaptors) but I managed to make it work only if temporary.

    For the ECC40 you have to be specific. There are 9 variants I know of, here are just a few. Even Tungram has 2 or 3 constructions. Without being specific it's hard to take impressions to heart.
    The outer right one is tungsram. A very safe choice, smooth, a bit boring somehow, nothing wrong with it but lacks dynamics.
    The next grey plate multiple holes is philips made in holland, a later version. Fantastic dynamics and rhythm but a bit coarse.
    The middle short grey plate may be made in france, very detailed tube, similar to the Sylvania 6SN7W short bottle but not quite as SSish. Good to brighten up a darker output tube or headphone.
    Then you have the early metal base, short and long bottle,can be grey or black plate, very natural sounding with dynamics coming close to the later grey plate but without any harshness. Very smooth but I have a feeling they're being held back by the Stellaris circuit.
    ECC40 by Phillips was made with different plate construction in Holland, France, two factories in Germany and maybe more. I've seen them branded Philips, Mullard, Amperex, Valvo, Telefunken, Pinnacle, Mazda etc.
    [​IMG]
    Taking the best out of 6N1P, that is 6N1P-E, the two variants and 1539, the mig fighter tube, they have a dense, lush, detailed midrange but on the dark side and loose ish low end.
    The ECC40 is not as dense in the mids while preserving and enhancing detail and smoothness, a bit airier treble and better low end extension and control but not by much.

    It's also down to synergy, after countless hours I'm still using 422A grey plate and 6N1P-E with AVVT. The 422A is mid focused as well and makes for some incredible sessions once the amp is warmed up.
    The AD1 really wakes up with C3G where neither 6N1P or ECC40 cuts it.

    In the long run I'd like to try these babies. Mazda AC/HL shortpath, what I think is one of the holy grail of input tubes if the Mazda PP3/250 is any indication. It can be done but I'll take it slow. Supposedly they last for 250,000h.
    [​IMG]
     
    Last edited: Sep 16, 2019
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  5. m17xr2b

    m17xr2b Friend

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    I also changed the UX sockets. AVVT gets its own pins as the socket will be stretched anyway and my other tubes will use the secondary pins. Plus I was always a fan of mounting from below if you know what I mean.

    [​IMG]

    The additional switches on the left are for PX4/AD1 operation. The one next to the rectifier is for the 422A.
     
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  6. Claud

    Claud Friend

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    Those Mazdas look like my Acme Supremes. How big are they compared to a 6N1P? Speaking of 6N1Ps, have you ever tried one of Ruby Tiger's Selects? Thanks for the pics. I have always wanted to see your switches since you told me about the one for the 422a. In my Stratus, it is a great sounding rectifier with the KR 2A3s. With your switch circuit, It must be so much better. When I can find another reason to send my Stratus back to Donald, I will have to get me one of those circuits.
     
  7. m17xr2b

    m17xr2b Friend

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    Google is your friend for datasheets.
    Don't kid yourself thinking adding the 422A switch will make a world of difference. This one is very subtle and impossible to A/B unless you have a very good audio memory. I wanted it for technical reasons and because I'm the one who explores the whole dungeon in games. I don't recommend sending it back for this switch as you might be underwhelmed with the result.

    For a more than subtle upgrade the stepped volume control as found in Stellaris Special and Silver is just the ticket. While the stock TKD pot is top notch conductive plastic is still plastic and I couldn't get hold of the upgraded TKD stepped one. The Khozmo pot seem to fit nicely in the Stellaris with a couple of mods.
    Out with the old, in with the new.
    [​IMG]

    The shaft is 4-5mm longer than needed and had to trim it. Added a few spacers between the pot and the chassis plate to make it even otherwise the volume knob isn't flush.

    Ordered the basic 50K shunt type and replaced input resistors with Charcroft Z-Foil, same as the vishay naked foils and saved 35$.
    Now it's two resistors in the input signal path, the Z-Foil and a Vishay SMD(a lot of debate online for which resistor has the bigger SQ impact).
    [​IMG]

    The steps are really nice and smooth, 48 is just the right number for fine adjustments so I don't miss the old pot.
    Even better, with C3g tubes on the old one I was at 1 to 1.5 volume because of the extra gain. Now I'm at around 4 with HD650s and 7.5 with K1000. Between 0 and 7 the impedance is between 47K to 55K. Over 8 it starts to shoot up, not an issue for my SS dac but has to be considered.

    Without A-Bing it's hard to tell exactly what it does, but I do hear it as an upgrade. It's silly to say a veil is lifted, clearer, better focus, increased definition come to mind. As upgrades go, it's just above a good cable cable upgrade performance wise and worth it for such a fine amp.

    I've read some bad posts on Khozmo reliability even if the build quality feels sturdy, we'll see how it holds up. In Europe it's the cheapest 40+ stepped 50K pot I could find.
     
    Last edited: Sep 21, 2019
  8. Claud

    Claud Friend

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    Thank you m17xr2b. I was just hoping that the WE422a switch might be more effective. I have two WE422as and think they are a great rectifier . It really makes those KRs sing in my Stratus. You are a fine person to share your experience with me and others here.
    By the way, If you have not tried a Ruby Tiger Select 6N1P, I would be willing to help you out since this is not the first time you did so for me.
     
  9. bazelio

    bazelio Friend

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    Note to self: Never purchase anything that has previously been in m17xr2b's possession.

    PS nice shaft.
     
  10. Donald North

    Donald North Friend

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    17280883-48F3-42DA-99A8-B3D89F6E68BB.jpeg
    Starlett #1

    Tube complement:
    6CG7 input tube
    6DG6 output tubes
    5AR4 rectifier

    16dB gain
    9 ohm output impedance via XLR
    Selectable 9 and 120 ohm output impedance via 1/4” TRS
    360mWrms into 100 ohm; 440mWrms in 50 ohm
     
    Last edited: Sep 23, 2019
  11. Luckbad

    Luckbad Traded in a unicorn for a Corolla

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    How many dollars?
     
  12. Donald North

    Donald North Friend

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  13. Luckbad

    Luckbad Traded in a unicorn for a Corolla

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    Well, my SPL Phonitor XE has lasted for a long time, but umm...
     
  14. m17xr2b

    m17xr2b Friend

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    That 6CG7 will be the bane of me if I get the amp. 6SN7 in a different shape, endless rolling, could be fun.
     
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  15. Donald North

    Donald North Friend

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    I tried many input tubes so hopefully users will be less inclined so: 12AU7/ECC82, 6N6P, 6N30P, 5687, 5963, 6350, 6463. The 6CG7 provided the best sonic synergy, together with low in-circuit noise, microphonics, and availability.
     
    Last edited: Sep 23, 2019
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  16. ColtMrFire

    ColtMrFire Writes better fan fics than you

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    Very tempted. If I sell my T3 I can probably get it. Dammmmnnnn.

    @Donald North
    What's the wait time? Deposit?
     
  17. Donald North

    Donald North Friend

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    PM or email me to discuss
     
  18. famish99

    famish99 Friend

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    Are these run triode strapped or run ultralinear?
     
  19. Donald North

    Donald North Friend

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    Triode strapped. Interestingly, it has similar plate impedance and output transformer requirements as a 2A3.
     
    Last edited: Sep 24, 2019
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  20. k4rstar

    k4rstar On a journey... somewhere

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    are the OPTs for the Starlett still sourced from Edcor? great name for an amp btw
     
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