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About JimL

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  1. KGSSHV Carbon Build Thread

    I have both the 009 and the 007 Mk 2.9 with port mod. At the last Albuquerque meet, out of 6 listeners, 3 preferred one and 3 preferred the other, driven by a BHSE - I told them the 007 is less efficient so they needed to turn up the volume a bit to compensate. I slightly prefer the 007, as to my ears the 009 is a bit on the bright side, and the 007 Mk I is a bit on the soft/dull side. FWIW, recording engineer Bob Katz also prefers the 007 Mk 2.9 with port mod as being more tonally accurate, and Tyll at InnerFidelity seems to like Bob's modded 007 more than either the 007 Mk I or 009 based on his comments from Big Sound 2015.
  2. The Headcase Stax thread

    What goes in may be sinusoidal, what comes out may be sine wave plus harmonics, i.e. distortion. For example, I have driven a woofer with progressively lower frequency sine waves, and at some point the pitch suddenly seemed to double because it was producing enough 2nd harmonic distortion that I heard the distortion as much as the fundamental, and the pitch sounded an octave higher. In fact, the term "doubling" refers to this phenomenon. So, yes, flapping can occur, or doubling (or tripling, or higher harmonics).
  3. The Headcase Stax thread

    Below 20 Hz what you may be hearing is the harmonics of the tone rather than the fundamental - i.e. what you may be hearing is distortion, especially if you cranked it up.
  4. KGSSHV Carbon Build Thread

    If you're concerned about harshness, the 007 may work better for you than the 009. Not that the 009 is harsh, but it's a bit bright to my ears, and that can sometimes be confused with harshness.
  5. SRX-Plus Build Thread

    Glad your wife likes the SRX Plus.
  6. SRX-Plus Build Thread

    It's a totally differential circuit, so a single ended input automatically gets converted to a balance output - you are using both sides of the output regardless, so that wouldn't work.
  7. KGSSHV Carbon Build Thread

    How fickle audiophiles are! Just a week ago the SRX Plus was the greatest thing since sliced bread, and now...a new girl and the old one forgotten.
  8. unbalanced/balanced to balanced tube input

    Looks a lot like the front end of an electrostatic headphone amp (T8000-ish), but with relatively low voltage transistors (except for the KSA1156). You could always substitute a MOSFET current source for the input tube tail CCS.
  9. Technical Assistance/Advice Thread

    So, it was shown decades ago that 5-10% high filament voltages will decrease tube life. On the other hand, running your filaments 5=10% low will not affect cathode emissions much. 6SN7 tubes draw 0.6 amps each, or 1.2 amps for a pair, so an 0.5 ohm resistor will drop your filament voltage to about 6.2 volts, while a 1 ohm resistor will drop it to 5.6 volts. Somewhere around 0.7-0.8 ohms should do it - a wire wound resistor of those values is pretty inexpensive.
  10. Trilogy H1 electrostatic amp

    So the major issue I have with the Trilogy is this: given the tube complement, the only possible circuit is the Egmont topology shown in spritzer's post of August 27, above. This is the simplest, cheapest electrostatic amp circuit around, similar to a circuit that Schiit considered building as a CHEAP electrostatic amp at one point. As best I can tell from internal pics that have teen posted, the Trilogy doesn't even have output constant current source loads, which make a big difference in drive capability. congo5 has built two Egmonts, and modified one by substituting constant current source loads for the plate resistors. He reported that: "Having two Egmont's I can A/B them to compare. It is a huge improvement, more volume and much less distortion. Much more of a usable amp now. Noticeably cleaner bass. Like Night and Day." So, an Egmont type circuit would be reasonable for an amp selling for, say, $1000, or 800GBP. No way is this worth what Trilogy are asking for it. And as far as sound quality, here is a show report from Head-Fi by someone who owns a KGSS Carbon and SR009: "Stax 009 + Trilogy Audio Amplifier This was introduced as a ground up new design with all tube line stage. It sounded better than the T8000 but not by much. Nice enough but not excited yet. I get a wow moment at home on my Carbon. Not hearing that here. The soundstage is nothing special. Looking in the top grill out has 6 tubes set horizontally. It was not as warm as my Carbon on the case / top. Think it costs 5K. Nice to see a UK produce, and I wanted to be wowed but not happening. No USB port so listened to Diana Krall and some Jazz." If you like the sound quality, fine. But honestly, for the price I think it's a rip-off. Sorry.
  11. Hmm... Let's see. Topology described as: BJT Folded Cascode+Tube with CCS, 6SN7GTB outputs. Max output 325 VRMS which calculates to 920 volts peak-to-peak - this suggests PS supply of around +/-300 volts give or take. So I Google searched folded cascode and came up with this image from a patent application - looks similar to the input and mid-stages of a Stax amp, but maybe with BJT input instead of FETs, and the CCS looks cascoded, so probably the output stage is similar to the SRX Plus, but without a tail current source. So, yeah, overall similar to a SRM-T1 with CCS in place of the output resistors, or a KGDT/KGS Most likely passive PS, though.
  12. Technical Assistance/Advice Thread

    So, the problem is, even if the DN2540 sits at +300 volts, with signal, it can swing anywhere between ground and +600 volts with a big enough input signal. But the DN2540 is only rated at 400 volts. You should be able to see where I am going with this. Furthermore, as Kevin Gilmore points out, there is nothing in the circuit that sets the drain voltage of the DN2540 at +300 volts. The 10M90S current source is pretty much indifferent as to what the drain-source voltage of the DN2540 is so there is really nothing to control the quiescent voltage of the DN2540 drain. The feedback resistor really won't control it. I saw this in the SRX Plus, which uses 250k feedback resistors - there were times during de-bugging and adjustment when one output was nearly at B+ whereas the other was close to B- until I got things tuned up. That is tolerable with tubes because the maximum tolerated voltage is higher than the maximum rated plate voltage. Not so with MOSFETs or transistors - exceed the maximum for even an instant and you have a fried device. If that happens to your circuit on turn-on, it'll blow so fast you won't even know what happened. Take a closer look at the HEV70 schematic, it looks like there is a resistor network to set the quiescent output voltage.
  13. Technical Assistance/Advice Thread

    What I'm confused about is, why would you want to build a so-so amp just to try things out? It seems to me that a better solution is to get an old Stax SRD-6 or 7 adapter box, modify it to pro bias and drive it with a standard speaker amp. That is a known quantity, will be easier, have at least decent quality sound, and probably less expensive.
  14. The ultimate DIY? A Stax SRM-T2!

    Never going to happen. As Dirty Harry said, "A man's got to know his limitations."
  15. The ultimate DIY? A Stax SRM-T2!

    As I recall, that's the circuit that you tried to build, but found the OA2 tubes lost most of the signal?