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bhjazz

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bhjazz last won the day on February 5 2012

bhjazz had the most liked content!

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About bhjazz

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    High Roller
  • Birthday December 31

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Converted

  • Interests
    DIY audio, Java, photography
  • Headphones
    HD-600, PS500e, ATH-ESW9, SE-310, E4S
  • Headphone Amps
    CKKIII, Headamp Pico Dac/amp, Twisted Pear Ventus, MHSS | Prev->Dynahi, Pimeta | Next -> Bijou
  • Sources
    DVP-S9000ES, Audio Alchemy DDS III, Dual CS-431 TT, Jolida FM tuner, Laptop+HiFace
  • Other Audio Gear
    Theta, Classe, Cardas, Bottlehead, ASC Tube Traps, Shunyata Hydra 8 & Hydra 2

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  1. Looks great! I recently added a K&K Step Up trafo to my own Delos. I liked this cart before, but now it's even closer to that spooky realism you hear about. Dee-lish.
  2. It's around here somewhere, I believe. The dent in the lower portion of the face plate was kindof getting to me... Probably happened during shipping here back in the day. So I ended up doing just a few things and it all locked in. I connected input grounds on the boards together, as well as the output grounds. This was weird to do since the left and right grounds were already connected at the Alps. Finally, I connected the ground from the output jack to the ground plane screw on the closest amp board. DEAD QUIET. Finally! Hey, many thanks to you Nate, Doug, Craig, and Pars for all the ideas. I'm glad to have this one back in the arsenal! Will post some pics now that it's done. Still looking for a 3mm green LED for the new front panel, though. (I think it was a 3mm) I have no idea why that item is so hard to find these days.
  3. I had tried some of these connections before, but adding them together was the key. The amp has been dead quiet for an evening or two. More soon.
  4. You're definitely on to a piece of the puzzle, Craig. I actually can't get a connection to check resistance on the front/rear panel unless I have the probe inside a screw terminal. Yesterday I tried the trafo twist and was able to knock the noise down just a tick. Cool. I also found that the weird volume pot noise (noise at about 50% volume) was more due to unshielded headphone cable location (the ESW9 that I had on) than anything else. So now I'm just hearing it at 0 - 25% on the volume pot. This is pretty close to what I hear with a pair of Grados. I started measuring everything to give myself a better picture. Here are some values. BTW, my Fluke 112 shows 0.2 ohm even with the leads shorted together. First, these are taken with the amp OFF. across caps inline from earth to rca grounds: 10.2 earth to rca gnd 10.2 rear panel chassis to rca terminal ground: 10.2 rear panel chassis to output ground (on amp board) 10.2 earth to ps board screws (I'm guessing this is the ground plane?): 0.2 earth to amp board screws: 0.2 earth to bolt holding down trafo: 0.2 power switch case to power supply screw term: 0.2 Channel A (top board, left channel) Channel B (bottom board, right channel) input gnd to output gnd (channel A) 0.2 input gnd to output gnd (channel A) 0.2 earth to chassis (front faceplate) 0.2 alps pot chassis to output gnd 10.2 front panel to rear panel 0.2 earth to output ground 0.2 earth to input ground 0.2 But here is something I found really odd: with the amp ON: Alps chassis to output ground on the board that *does not* have an output ground connection - 10.2 and immediate silence through headphones Alps chassis to output ground, on the board that *does* have an output ground connection - 10.2 and huge buzz through headphones This is heard most clearly with a pair of ESW9a 'phones. I'm going to start by bypassing the pair of caps that connect earth to the input RCA jack ground. That would eliminate most of the 10.2 ohm readings above. Next, I'll connect the ground screw from the pot to the current star ground, and connect input grounds together and output grounds together. We'll see where it stands at that point, but the tests with the amp on make me wonder what else is going on. Thanks!
  5. Wow, you guys are great. I'm so glad I could come back here and get such straight answers. Many, many thanks. Nate: you did not have the boards there. You simply had the caps hanging off of the amp boards. I wanted to keep the output caps from being so fragile, so added the boards (from Jameco) and the bypass caps since they were staring at me. I have wired the two boards together underneath. I'll try the "transformer twist" first. Thanks! Ah, I did not check the offset. Will search for the pots as well, just in case. Thanks! The ground scheme is what was in the original build: one input ground, one output ground. Connecting these two to the corresponding spots on the other channel did not work for me. Very interesting. I see two different schemes here: Connect (ground) everything or if everything is isolated then use some type of ground loop break. I think mine is a case of the ground noise volume being constant with volume, for the most part. Not sure why it comes and goes with volume change... I do feel like this chassis has totally different metal conductivity, so that may have turned into a problem when I tried to duplicate the original wiring. How would I connect the PCBs and the PS to this new ground? Using the ground off of the board itself, or the ground it is "processing"? That is, with the power supply for instance, if I check continuity between the screw that holds the board down and the chassis I get nothing. (My wording may be convoluted here. Blame the Syrah.) I do find it odd that if I connect my DMM to the incoming ground connection (at the IEC) and any random point on the chassis bottom that I get no continuity. However, if I do the same test and use the rear panel there is clearly some connection. I'll post what I find with some better testing. Thanks for leading me in that direction. No, VT4C is long gone. I think they closed in 2010, so now you know how long ago I started buying parts! Now that I have tested a little bit today, the pot is grounded to the front panel, but that may not be at equal ground potential to the rest of the build. (?) Again, many thanks to all of you. I'll try these, test a bit more, and report back.
  6. Pandemic Project #54: re-case the Ventus. So, some quick history: I won the raffle Nate had back in the day for the TwistedPear Ventus. It has worked fine and I have enjoyed it for years but I wanted it in a different chassis. Over the years I bought parts here and there. The case came from VT4C. I had top and bottom panels made with venting and finally got it all reinstalled recently, only to set up a vicious game of chase the ground loop noise for myself. The setup is, otherwise, the same as the original setup with all the same parts, just transplanted into a different case. The only difference in parts was changing the power button setup (which had a nice relay) to a bog standard clicky switch. The boards next to the amp boards just have a cap (with a bypass cap). Nate added these to tame some of the output voltage drift, if I remember correctly. So the noise through the headphones sounds like 120Hz ground noise, but more like a sawtooth wave than a sine wave. The amount of noise varies as the volume is turned up - it starts off loud at 0%, then goes away until about 25% volume, where it gets loud again, then fades until you hit full volume, where it is again loud. Touching the chassis changes the noise slightly, and touching the output ground also changes the noise. If I turn the volume up to the "silent mode" at about 50-60% I can touch the ground and bring the noise right back. I posted a similar question on the TwistedPear forums, but received pretty much nothing but questions. When I answered those, the discussion went dark. Thanks, TP audio. I have attempted various fixes that did not work: Disconnect the signal ground connection from the chassis ground (see pics below) Disconnect the ground bridge between the L and R channels on the Alps volume pot Change the ground connection from the left channel board to the right channel board Connect the grounds together on the amp boards Connect the ground from the Alps volume pot to the chassis Remove the Alps from the chassis Cursing and shouting at the noise I don't have a 'scope to check the incoming voltage from the power supply, but do wonder if something is amiss there. Any guesses for chasing the ground loop dragon? I really hate to see this amp gathering dust. Damn. Thanks for any suggestions. BH
  7. bhjazz

    Dead JFETs?

    Craig, thanks for the confirmation. I appreciate it. They are currently in-circuit, so that could mean they are storing a charge somewhere and staying open. I had suspected the diode-like properties had gone away, which prompted my post. I'll remove them from the circuit for testing and if they are, indeed, burned out, I would have to replace them anyway. Thanks again.
  8. I have a pair of 2n5457/5458 JFETs on a small board as part of a bias scheme for a 12AX7. The circuit also has a 9v battery. I cannot get the voltage dialed down, so I checked the JFETs. The resistance from gate to source (and gate to drain) read the same in both directions: roughly 1k ohm. These are dead, aren't they?
  9. I'm working on a Larocco prototype right now. I'm getting down to final assembly and realized that the Alps pot has a 20mm shaft, but it's going through a 10mm front panel. Most knobs have the set screw at 10mm so I think i'm guaranteed it will fall off at first use. Q1: Does anyone know of knobs (EDIT: that aren't fugly) which have the set screw at less than 10mm? Q2: This sounds hokey, but is anyone aware of a way to extend the shaft 5mm? If not, I suppose I'll have to drill out the inside of the panel to regain a few mm. Thanks.
  10. By the time 4 years rolls around digital formats will change, so...at that point the C1 will probably cost 60k.
  11. Cable done tonight and working great with the Onkyo Android player. Thanks again, Justin!
  12. Tuned in as well. This is working nicely with the Cabernet Franc.
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