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The DIY'rs Cookbook

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  1. johnjen
    So I did swap out the 'factory tweako'' caps for a set of Hovland SuperCaps.
    It took a day of running the dac before it 'settled in' and started to close the gap to match the SQ of my reference tweako Jggy dac.
    Both dacs were being fed from my AOIP stack with SPDIF feeding the Jolida dac and AES feeding my Jggy, which in turn then fed the Purp-Amp…
    And then…

    The Purp-Amp took a mother may I step up, which in turn opened up that gap even more than it was even before the factory caps got dialed in.

    That DHT gudness kicked in and even at this early stage, well, lets just say the Jolida needs more, MUCH moar tweaking.
    Those Miflex caps I installed in the Purp-Amp have started to fully settle in and that MitM (Magic in the Mids) is back and is still changing, albeit slowly.

    I figure it's been ≈ 50-100hrs of run time since they were installed and since then there have been other tweaks added (grounding, grid stoppers etc).
    It's to the point where I'm listening to Led Zepplin and I can actually hear all the words and understand them, and this applies to every 'voice' regardless of what it is, as they are all clearly immediately identifiable.
    This is the 1st (well a repeat of the first) time that this degree of Transparency, Articulation, and Instant Recognition has presented itself.
    And I've been listening to Led Zep since the 70's on vinyl.

    This MitM and especially the DHT (directly heated triode) variety, when used in very simple SET circuits, has an added degree of gudness that is just simply stunning.
    SDSG (SuperDuperSuperGlue) is in full force and this degree of tweak checks off on all of the rest of those attributes I deem that constitute what is 'Better'.

    And I'm getting ready, once again, to tear it apart for yet more tweaks…
    Will I ever learn to leave well enough alone? hahahahahahahahahaha…

    But I do really need to change the input xfmrs and re-locate them and track down some circuit hiccups, that while they have been reduced in amplitude, really shouldn't be there at all, even if they are at ≈ 0.4mvac (≈ -60dB)

    And so it goes.
    JJ
     
    Last edited: Sep 23, 2019
  2. johnjen
    Since I've yet to discuss this particular topic I doubt ANYONE here will be able to guess what this 'device' I made is.

    But that won't stop me from entertaining guesses.
    At least for a day or so…
    hahahahahahahahaha

    weather wire.jpg

    JJ
     
  3. gefski
    Looks like a waterproof fuse holder for my Jet Ski. :swimmer:
     
  4. johnjen
    Well, you got 2 out of 3, it is water proof (with LOTS of that marine grade heat shrink with the self-glueing action) and inside the bulbous center is an accessory automotive fuse holder.
    But there is a 1Ω resistor inside, all carefully installed and protected.

    It's a ground isolator/noise absorber for the comcast cable internet feed into my house.
    It will lower it's dirty noise from getting into the ground connection for the rest of electrical service for my house.

    This is part of my research into grounding and what can be done to improve it.

    JJ
     
  5. gefski
    Love that you're digging into that! Many of us have $$$$$ in our systems, then for streaming have crappy feed into cheesy Comcast or (in my case) Frontier devices. Keep us posted!
     
  6. johnjen
    What tipped us off was when we were developing the 45 amp, under some conditions I would start hearing a local talk radio station in the 500KHz frequency band.
    We found it on the ground plane, which means it was getting into every piece of gear that was grounded.

    This 1Ω trick will hopefully reduce this, and/or alter this 'detector' circuit function enough to limit this anomalous behavior.

    For a while there, we were blaming those dastardly alien signals that were beaming in from space, contaminating my audio system…
    hahahahahahahahahahaha…

    I might also install a separate ground rod for the comcast feed, or perhaps use a separate ground for the entire audio system depending upon what is most effective.

    This rabbit hole has LOTS of side paths to explore.

    JJ
     
    Last edited: Sep 29, 2019
  7. johnjen
    To date I have just under 150hrs on the Purp-Amp and it's still settling in just a bit.
    The SQ is marvelous especially on poorly recorded music, which is a bit of a surprise actually.
    All the spatial cues (the acoustic 'space', depth, side to side and in the vertical planes) are surprisingly stable and 'transparent' in that its easy to hear the contributions that the 'space' makes to the performance, no matter if it's a studio or live based recording.

    And this purp-amp design wasn't as tightly focused on reaching down to the very bottom end like the 45 amp, but it continues to surprise me with impact and power all the way down.

    And where tubes excel in the mids this amp is subtle and nuanced and as usual for a god tube amp, it LIKES to be cranked up.
    This is where the MitM (Magic in the Mids) can really stand out.

    As the MOAR knobs get cranked up, the acoustic presentation tends to be MOAR REAL, MOAR U-R-There-ish.
    This trait is common to tube amps that are well heeled that can handle getting cranked on without any facial wincing.
    And at 'elevated' volume levels when the music pushes on the edges of the performance envelope, it can become 'painfully' obvious things are running out of steam.
    This amp has more there, there, than I will ever need.

    But wait!!!
    There's more refinement to come as the new input xfmrs and grid leak resistors get dialed in, as they should make significant improvements as well.

    JJ
     
    Last edited: Sep 30, 2019
  8. johnjen
    To date I have just under 150hrs on the Purp-Amp and it's still settling in just a bit.
    The SQ is marvelous especially on poorly recorded music, which is a bit of a surprise actually.
    All the spatial cues in the acoustic 'space', depth, side to side and in the vertical planes are surprisingly stable and 'transparent' in that it's easy to hear the contributions that the 'space' makes to the performance, no matter if it's a studio or live based recording.

    And this purp-amp design wasn't as tightly focused on reaching the bottom end like the 45 amp, but it continues to surprise me with impact and power of the very bottom end.

    And where tubes excel in the mids, this amp is subtle and nuanced and as usual for a good tube amp, it LIKES to be cranked up.
    This is where the MitM (Magic in the Mids) can really stand out.

    As the MOAR knobs get cranked up, the acoustic presentation tends to be MOAR REAL, MOAR U-R-There.

    This trait is common to tube amps that are well heeled and that can handle getting cranked on, without any facial wincing.
    And at 'elevated' volume levels when the music pushes on the edges of the performance envelope, some amps can become 'painfully' obvious, when things are running out of steam.
    This amp has more there, there, than I will ever need.

    But wait!!!
    There's more refinement to come, as the upgraded input xfmrs and grid stoppers get dialed in.

    JJ
     
    Last edited: Sep 30, 2019
  9. johnjen
    So today I added a 100KΩ stereo volume control to the 6L6 amp.
    It needed it.
    I also swapped the input xfmrs for another set and use the originals in the Purp-Amp.
    I'll fire it up tomorrow and fuss with a few other details.

    And the Purp-Amp is blossoming and I think I can begin to describe, at least initially, the difference between these Miflex caps and the Hovland supercaps I started with.
    The Miflex's are a bit less fluidic, a bit more 'reserved', less attention getting/spectacular.

    And they may still need more time to fully blossom as they only have ≈ 170hrs on them.
    Still that holographic aspect is only hinted at, at least at this point.

    Here is the new volume control.
    6L6 w:pot.jpg

    I'll take a few pics with it all lit up and running and post them later.

    JJ
     
  10. johnjen
    An Update…

    I have been running the 6L6 amp after I added the volume control and it has helped, partially because I no longer need to use the digital volume control in the Media Center player.
    This would seem to support the notion that analog volume controls work better than using a DSP volume control in these tube amps.

    And I have tested the 2 sets of matched 6L6 tubes I recently acquired.
    The 1st is a set of Triad made in Japan tubes, which while nice, don't quite equal the McIntosh (made by GE) set I was running.

    But the 2nd set is set of Westinghouse tubes made in Germany, are simply outstanding.
    We suspect they were made by Telefunken and physically they are quite different than any of the 6L6 I have ever seen.
    And it became immediately apparent that they delivered added clarity everywhere, with impact of all leading edge sound sources, with power and a sense of immediacy that is simply wonderful.
    And in some ways they deliver SQ which is the equal or better of the Purp-Amp, but with a different emphasis and a slightly reduced bandwidth.
    This was an unexpected outcome based upon the fact that was meant to be primarily a speaker amp, and as such we didn't expect this degree of delicacy and finesse to be heard on headphones.

    And I have installed the 'new' input xfmrs in the Purp-Amp and it needs a bit more time to settle in, but is already delivering an added sense of delicacy to inner details and the soundstage.

    I also changed the grid stopper resistors and went from 330Ω to 520Ω just to find out what impact that would make.
    And I have since returned to the 330Ω value on the driver tube (6CG7) as the SQ lost a bit of directness and finesse.

    I'll take some pics of the 6L6 amp once the finish on the box is ready.

    JJ
     
    Last edited: Oct 6, 2019
  11. johnjen
    Here are a couple of pics of the 6L6 amp with the new volume control pot installed mounted in the cedar base.

    6L6 vol control front.jpg

    6L6 with vol control side.jpg

    The 'cable' attached to the speaker outputs is a impedance matching 'circuit' so that when I use my 800-Jmods, the load that is reflected back thru the output xfmr to the output tubes is 'idealized'.
    This is yields a significant improvement in SQ as it considerably narrows the spread of the 800's change of impedance over the audio bandwidth that the amp 'sees'.
    I have also added this 'trick' to the Purp-Amp's output xfmr which yields similar SQ improvements.

    And if you are running a tube amp with 4-8-16Ω taps on high impedance HP's, I highly recommend adding this 'circuit', which is nothing more than 2 fixed value resistors (one for each channel) in parallel with your HP's.
    The value needed is based upon the Ω of the taps you use, and the impedance of your HP's.
    I have a pair of 8.2Ω resistors (as marked) on the 8Ω taps when using my 800-Jmods.

    The Purp-Amp uses a different set of resistors to match it's 32Ω output impedance.

    JJ
     
  12. johnjen
    Uh, er, um, it's uh, like this…

    The Purp-Amp, it's establishing new levels of SQ and hasn't stopped morphing since I 'fixed' it.

    I hit a lick tonight and it's still morphing and settling in, but already whole new layers and levels to the soundstage are emerging.
    Each 'voice', their acoustic space, and their dimensionality within that space have taken steps up with additional nuances which continue to become apparent the more I listen as the hrs accumulate.

    When I installed the new input xfmrs I forgot that they needed to be 'properly' grounded, because I mounted them to the side walls of the wood box and not to the top plate like I had originally planned,
    and now they are wired in properly…

    The s/n has improved to -68dB / -120dB (R / L) 0.38mvac / 0.000mvac,
    which means there is till a gremlin in the right channel that once it's dealt with should improve things even further.
    So now to find the source of 0.38mvac noise in the right channel.

    Some might say 'inaudible is inaudible' but I have this nagging hunch that when both channels are equally quiet at say -120dB (0.000mvac) the SQ will again belly up to the bar and push it higher still.

    JJ
     
    Last edited: Oct 10, 2019
  13. johnjen
    Right now I'm testing a new regulator tube in the 6L6 amp and thus far it seems like a winner.

    So I tool a couple of pics of the amp running in the dark and semi dark.
    So glamor shots in the dark, a new wrinkle…

    6L6 dark shot #1.jpg

    and a little more light
    6L6 dark w:light-2.jpg

    This amp is sounding more and more like the Purp-Amp in terms of nuance and inner details but with much more power behind it.

    JJ
     
  14. johnjen
    So this 6L6 amp slowly continues to become more focused and delicate in it's inner details as the hrs pile on.
    And this TAD 5AR4 rectifier tube has also stepped up the amps 'game' as well.

    And having this MOAR knob on the front end of this amp is a big help in being able to control it's output, which is considerable when pushed.

    I never even approach 12oclock, it's from 9 to 11:30 and that's including using 2 different sources as both SE and bal are being used (No, not at the same time… hahahahaha), so I'm switching between a 2v or 4v signal strength inputs as well.

    And it's all to easy to 'crank on it' and let'r rip. which can be mighty impressive, as all that seems to happen is MOAR, but not louder.

    But with MOAR comes REAL as well.
    Yeah it's an affect but it can be quite entertaining regardless.

    Drums and other percussion has a degree of punch/impact from the Leading Edge Dynamic Impact, (LEDI), which comes from moving air rather than just modulating it, (think trouser flapping, only with HP's).

    JJ
     
  15. Tjj226 Angel
    I have never seen 6l6GCs look like that. They look more like a 6l6G or even a KT66
     
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