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Everything posted by Laowei
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Thanks Kevin. Your generosity in taking the time to dissect and explain this is greatly appreciated.
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Not sure if that's true in a differential circuit. In other amps, I have increased the resistor and made the amp sound worse. Same current thru higher resistance equals larger voltage drop. Add AC and it would make things dynamically worse; higher voltage modulation on the screen.
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I see the effective AC loop in the GG as this: ( Carbon shown) In a pentode, the screen grid electrostatic potential effects the electron flow to the plate. One can even use the screen to drive the plate if so inclined. Connecting G2 directly to the plate to simulate a triode, they would share the same potential, but G2 would fail due to excessive current draw. So to limit current, a resistor is usually added, which separates the screen from the plate potential depending on current across it. The higher the resistor value, the more difference. At DC, things look stable. Add in hundred of volts AC swing and the voltage across the resistor will modulate the screen potential. Adding the diode stops AC thru the screens (stabilizing the potential) and leaves it to pass only through the plates. I've found my GG to be able to play both a little louder and a little cleaner into my SR-009 after doing this addition.
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With G2 connected to the plate with a resistor, as the screen passes current across the resistor, the screen will have a (slightly) different potential than the plate. With a CCS and DC, this relationship will be stable/constant. Varying AC load will vary the current across the resistor, and vary the screen potential relative to the plate..The varying potential on the screen can to an extent control current collection of the plate. Adding the diode, AC load is blocked from modulating the potential of the screen. The voltage drop across the diode is constant so should not be of consequence. Follow the AC loop in the differential circuit. 200Vrms (300Vpeak) voltage limit on TX2575. Two 100K wired in series in the GG.
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A couple little things for now. Replaced the originally built Dale RN60 resistors in the global NFB circuit with ultra low noise and TCR TX2575 naked Z foil Vishay resistors (400VDC PS only). Also added a 1N4007 diode in series to the screen current limiting resistors that wire the pentode into triode operation. Similar as have done to my amps in the past. Will replace with Schottkys soon.
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Just plugged in 2 matched pairs of used/tested above new, Valvo labeled Mullard xf3 tubes in my slightly modified GG. Now we're talking. That's how I remember real tube magic.... The only other tubes tried in this amp: 2000 vintage Svetlana Winged C EL34, NP JJ 6CA7, NP Gold Lion KT77. Not a drastic SQ difference with the OS Mullards, but the music simply flows with the xf3s, reproduced with a calm ease, clarity, presence and majesty absent in those other tubes. Everything sounds so balanced and right with these old guys.
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RIP Cassini. Job well done.
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Just trying swapping anything to chase down the annoying courseness.
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Yes, the output is direct coupled, but is filtered. The filter effects the output signal.
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Yeah, I think so after a first night of listening. Will need more run in time to hear how they finally settle in. Months ago I replaced the 220pf and 330pf WIMA FPK and 0.1uf WIMA MPK caps in the anti-imaging filter of each channel. I have a general bias against any WIMA caps in the signal path. So I purchased some AMTRANS polypropylene film and copper foil caps from Parts Connexion for the first 2 values , and new manufacture black case Vishay MKP 1837 from Mouser for the later. I had read many good things on websites about those ERO/ Vishay caps. Replacing the stock WIMAs mostly opened up the low level upper harmonics and gave a clearer picture on the music. The stock Yggy is a bit veiled in that regard IMO. But there remained a slight coarseness in the HF, that became noticed as a signature as time went on. It made extened listening sessions fatiguing after several hours. I swapped out copper for silver/gold wiring, other makes/brands of tubes, even replaced the NFB resistors in my GG with naked foil TX 2575 Vishay resistors. More resolution, but still that nagging coarseness. Was it my SR-009??? Found an eBay site and that listed NOS ERO KP1837 blue case caps. Seems that when Vishay bought ERO/Rhoderstein they moved production and changed the dielectric from the earlier well reviewed capacitors. So I bought these NOS caps, and just put them in last night. On first listen coursness is gone, there is more low level info naturally portrayed, slightly more color and tone in the body of instruments, and seemingly better dynamics. To me it is always interesting how getting the upper HF sorted out can focus the imaging and also give better dynamics and definition to the bass. I have a limited number of those NOS blue case ERO 0.1uf caps left over. PM me and I could send you a quad if you would like to mod your Yggy.. Also have some 220pf and 330pf NOS blue case ERO KP1830 polypropylene film and tin foil I could include. Those are reputed to be more neutral and less warm than the AMTRANS.
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FYI, just got thru opening up my Yggy to pull two analog PCBs and swap out 4 filter caps. Took me 25 minutes. Upgrading to the Gen 5 USB PCB earlier took me maybe 15 minutes. First time taking it slow and careful, it may take you a half hour. It's really easy, and the SBAF instructions are very straightforward. No need to over think it.
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RIP Walter Becker, the guitar half of Steely Dan.
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Good night Jerry Lewis.
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My amp is dead quiet. In my 2 case GG, I tie PS and Amp grounds to a single star ground on the Amp chassis. IEC ground is connected at the PS chassis and then carried separately to another point on the Amp chassis. My input is the same as yours, with XLR pin 1 grounded to the chassis, but I leave the pot's ground left floating (with each L and R +/- signal ground connected for the attenuator to work). Being balanced, they will null. With your pot ground connected to the amp boards and then daisy chained to the PS board, possible ground loop there. Try disconnecting and see if the hum is still there. https://www.tortugaaudio.com/articles/humming-along-to-the-pin-1-problem/
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Happy Birthday Sorenb!
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Never a fan of iTunes.I bought Pure Music early on. Tried the Amarra (meh) and Audirvana early demos. Was questionable if I heard a real improvement between them, but was not using STAX with Gilmore amps at that time. I ended up buying Audirvana and kept it. It's been massively updated with options over the last several years, and the SQ has improved too. Just now comparing to Pure Music, the latest Audirvana is quite a bit more transparent, resolving and clear. It shines with the Yggdrasil Gen 5 upgrade, IMO. You might consider trying the free Audirvana demo: https://audirvana.com/?page_id=3397 Later if you like Audirvana, there is really slick iPhone app for remote control: https://audirvana.com/?page_id=3620 I use it to run my Mac mini headless. Its really nice to use.
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John, are you using any playback software like Audirvana, Amarra, HQPlayer, ....etc? Those work a lot better than iTunes.
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So sorry to hear this. Condolences to you and your family.
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Recieved and installed the Gen 5 USB upgrade yesterday. On first listen, it sounds more refined than the Eitr. A high value upgrade to the Yggdrasil. End of story for me (unless it breaks).
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The older Gen 3 USB input originally shipped with the Yggy is not the best sounding unit out there. The Gen 5 upgrade is supposed to bring the USB input up to the AES/EBU input quality, which most who write on the internet seem to prefer. I don't have a lot of experience with AES/EBU input to the Yggy. Except with using a Mutec to convert from USB, which I really did not like at all. As with Theta Digital products, there is no Gen 4. I had a Schiit Eitr, the stand alone unit that inputs USB to a similar circuit to the Gen 5, and outputs SPDIF coax. In my brief audition, the Eitr sounded really good. Switching USB cables made no difference that I could hear. Switching coax cable still made a difference, so there was that variable. Unfortunately after a week, it quit holding lock and was dropping out about every 20 seconds. Tech help could not help, so back it went. Hoping the Gen 5 delivers this time on the Schiit marketing promises.
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Sent back the non-locking Eitr to Schiit a week and a half ago. Received a full refund including shipping both ways, with no restocking charge. The Gen 5 self installed USB PCB upgrade became available today on the Schiit site. So I ordered up one for my Yggy. For a not outrageous price of $100 plus shipping. Hope it works better long term that the Eitr.
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Plus the tightly twisted output wires to the STAX jack. What's the Schiit with that?
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Bought mine for next to nothing at the end of a Ham swap meet. The original owner did not want to lug it back home. Use it for first slow start up of tube amps.