jcx

well some part of this sale must be "fully valued" http://www.head-fi.org/t/604826/fs-bhse-stax-o2-mark-i-combo

I like knowing more about the part - the later IXTP01N100 datasheet has capacitance curves - while the CCS datasheets are missing these specs so I would definitely roll my own CCS with the IXTP01N100 just tried hacking the IXYS 10m90 SPICE model into LTspice - I get 100 pF Cds @ 200 Vds in sim - an order of magnitude worse than the IXTP01N100D mosfet datasheet have any of you measured these parts dynamically? - I doubt they're really that bad but I believe the mosfet datasheet a lot more

dual mono isn't "overkill" with Class A balanced output - it is closer to "not even wrong" Class A balanced output draws constant current from the PS - there isn't any interaction between channels via the PS if they are both ~ ccs loads irrespective of audio signal in either channel even in clipping the most common situation will be Voltage clipping - low frequency audio signals don't draw any appreciable current drivng ES, are the most common large amplitude signals

odd subject for the KGSSHV thread is there really any issue with power sequence in the BH - the ss ccs loads always limit the output tube current

I'm aways curious about how solid teflon machined parts, especially any press fits, are expected to work for decades - has teflon creep, stress relaxation been taken into account? machining vs application temp can be a mechanical dimension tolerance issue too with a (crystal transition?) thermal expansion coefficient peak occurring around room temp - close to 1% volume change in range from 60 - 90 F http://www.rjchase.c...fe_handbook.pdf I would expect chassis mounting pretty much requires spring washers with flat washer - since I certainly have >60-90 F range in my apt over the course of a year solid polystyrene stock is also available - different problems, still great electrical properties

http://www.cdc.gov/norovirus/index.html ??

I think the SRPP should be viewed as a modulated CCS like Pass Aleph http://www.passdiy.c...df/zen-ver2.pdf - the 50% split of AC current seems likely to optimize efficiency of bias current/power dissapation with little danger of destabilizing gain swings that the higher modulation levels of the mu follower extreme Pass shows enhancment mode power fet with bjt regulator and AC coupled modulation - with depeltion mode power fet and tapped resistor string the circuit is a lot simpler I tried talking about these ideas in the T2 thread when the good Doctor asked/speculated about alternatives

the gate drive opto isolators provide floating V ~8V from a string of photodiodes that you can series with the enhancement fet gate to get "depletion mode" equivalent - but the floating V source can provide very little current, < 10 uA - quite enough for mosfet gate drive though some C in parallel with the photodiodes assures enough charge capacity to soak up Crss slewing current - possibly a "gate stopper" R would assure RF stability http://www.irf.com/product-info/datasheets/data/pvi5013r.pdf noise and V ref stablity over temp, LED life are possible issues - depending on mosfet gate threshold V you should have enough V headroom to put a jfet or LM334 ccs in series with the mosfet source - pretty much eliminating concerns about the gate V quality that you would have if you simply used a source series R to set the current

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=PVI5013RPBF-ND

looking in PAIR Nelson has paid up his maintance fees on 5,376899, 17 years from 12/27/94 issue date still gives him the rest of this year but from his various statements it seems unlikely that a "public domain" headphone amp project would be a problem for him

I think the tl431 would be best avoided - as an amplified band gap reference working down to low currents it is inherently noisy - and as a feedback loop amplifier it is poorly characterized band gap reference noise can be OK for audio when you insert a lowpass filter after but the required low corner frequency complicates startup dynamics http://www.analog.com/library/analogDialogue/archives/32-1/xfet.html - precision instrumentation designers often look at the .1-10 Hz noise number - audio really doesn't care given low frequency insensitivity of hearing http://cds.linear.com/docs/LT%20Magazine/LTMag-V19N1-03-References-BrendanWhelan.pdf buried Zener LM329 is still available and is probably the cheapest of the buried Zener devices with the heavy output C the feedback amplifier inside the regulator probably ends up with the output Cload determining the dominant pole compensation for T2 use "reasonable" 1/f, drift, tempco could be adequate - I'd look for the 1 KHz S/N - don't forget to divide by the Vref value

I'm still guessing that U7,8 op amps outputs common mode V is unconstrained and its possible the circuit "works" with one of them saturated at a rail I would just use one differential integrator and turn the 2nd op amp into a gnd referenced inverter of the 1st's output then a resistor from each op amp out to the 2 cascode Q would give offset currents that are symmetric about a common bias value

does the offset op amp circuit need a common-mode servo/control? at a 1st glance it looks to me like it would be perfectly happy with one op amp integrating to a rail on one side with the other then working "single ended" to servo the offset

um, I said the 1 mA spice ccs ~= the T2 cascaded pnp ccs - I'm trying to show the circuit mods fit in the existing T2 output ccs topology the push-pull operation of my 1st circuit seems to be one way to increase slew rate using the same number of parts as the existing T2 ccs

the Pass A40 might be considered an ancestor of SS modulated push-pull Class A bias, Pass still uses a variant of the modulated current source in his recent Class A amps I previously showed splitting the "sense" R to get push-pull output with a fet ccs this can easly be done with the T2 Vref+bjt ccs too obviously the sims are just circuit sketches - and the V and Cloads are scaled down/upto keep currents ~ the same as T2 output ccs - the Q models are just what LTspice include common to the T2 output ccs circuit: triple pass Q with 2n2222 models are really bad approximations of the 2sc3675, cascaded pnp ccs is approximated with the spice ccs in the 1st sim I show a circuit with no more parts than already exist in the T2 output ccs but theoretically gives 2x output current swing - which could double slew rate for the same quiescent bias current setting (I assummed ~10 mA output bias) the 1st circuit uses a higher Vref 12 V Zener to get some added "loop gain" (relax, its all local degeneration) - since the circuit modulates the bjt current we can expect distortions from Vbe/Ic and Vref bias varying when the pass bjt base currents change does the 2x gain, doubled slew rate compensate for the now varying ccs Q Vbe, Ib caused errors? - someone would have to build and measure the next two circuits use the same triple pass Q but use local loop feedback to control the current and may be seen as derived from the "ring of two" bjt feedback ccs the feedback Q Vbe is the Vref for the circuit in the 2nd push-pull current source the third uses Hawksford/Baxandall "Super Pair" to give cascode like cancellation of Zcb, and the extra current gain reduces the feedback Q/Vref bias variation gain - the feedforward increases the "Q" and the circuit will have RF problems - but so does the Cascode that is AC referred to the "control" Q emitter - I believe it can be tamed with Zobel like RF damping that has little effect on the performance improvements at audio frequency I also added Zener Vref in the feedback Q emitter to allow higher current sensing R values so the feedforward is more effective (although the improvement may just be from the added current gain) I probe the load C, Vsource currents and look at fft plot to get an idea of the circuit topology effects - all have falling harmonic level with increasing order - the current control feedback versions I(Cload)distortions start ~ 40 dB lower than the 1st circuit, Vsource current are what an "ideally" controlled output tube would have to do to make the V distortion =0 at this point, I(Vsource)is lowest with 3rd circuit the third "kitchen sink" circuit's higher frequency harmonics fall faster with increasing order so some of Hawksford's "slope impedance distortion reduction" appears to be taking place in the sim T2_pp_cs.asc.txt