HeadphoneAddict Posted October 6, 2009 Report Share Posted October 6, 2009 after a bit more listening today I feel the smegma pros still have the edge on them for overall balance. The 950 is a bit shouty in the upper mids and are pretty bright. All from the E90 amp and SRD-7Mk2. I'll wait until the eXstata gets here for proper full evaluation but so-far the Stax still have it. In the end I sold the ESP-950 and kept the Smegma Pro. You should be proud. Quote Link to comment Share on other sites More sharing options...
Smeggy Posted October 6, 2009 Report Share Posted October 6, 2009 heh, well the Beyer ET1000 is beating both right now except in comfort. Quote Link to comment Share on other sites More sharing options...
mypasswordis Posted October 6, 2009 Report Share Posted October 6, 2009 heh, well the Beyer ET1000 is beating both right now except in comfort. Uh, you still running it from the E/90? Quote Link to comment Share on other sites More sharing options...
Smeggy Posted October 6, 2009 Report Share Posted October 6, 2009 Uh, you still running it from the E/90? Nah, SRD-7 Quote Link to comment Share on other sites More sharing options...
manaox2 Posted October 11, 2009 Report Share Posted October 11, 2009 My latest pair of ESP950 I am glad to say have no channel imbalance. After whipping up a quick adapter, these kick so much ass out of the T1. Anyone know where I can grab a pro Stax cable? Quote Link to comment Share on other sites More sharing options...
spritzer Posted October 11, 2009 Report Share Posted October 11, 2009 Try calling Yama's and tell them the cable on your Lambda is foobar. I'm guessing though that it would be cheaper to get a SRE-725 extension cable instead. Quote Link to comment Share on other sites More sharing options...
manaox2 Posted October 11, 2009 Report Share Posted October 11, 2009 Try calling Yama's and tell them the cable on your Lambda is foobar. I'm guessing though that it would be cheaper to get a SRE-725 extension cable instead. Thanks, I'll stay alert for the next one to come around at $50. Quote Link to comment Share on other sites More sharing options...
cetoole Posted February 22, 2010 Report Share Posted February 22, 2010 So, I know that it is pretty much public knowledge that the ESP950 bias is 600v, and Koss even says this, but has anyone actually looked at the bias circuit? I got my ESP950 back from RMA today, and noticed that is has the squeal that so many of us know just too well out of my SRM1/mk2, but is dead quiet out of the stock E/90. This has been really, really bugging me, so I finally went ahead and tore the E/90 open to get a look at the bias supply. Well, its pretty simple, a 10M resistor from the 600v (measured 612v) rail to the pin connecting to the bias, and another 10M resistor from that to ground, in parallel with a 0.022uf 630v film cap. My measurement of the bias voltage, using a DMM with a 10Mohm rated input impedance, gave me 202v, just what would be expected from a 10M-(10M||10M) divider. I dunno guys, this sure looks like the E/90 is really just putting out 300v bias, and if that is the case, it would really explain the all-too-common squeal these tend to develop and we have been attributing to dust. Thoughts? Quote Link to comment Share on other sites More sharing options...
GPH Posted February 22, 2010 Report Share Posted February 22, 2010 I'm sorry to break your theory, but the two ESP950 I've had squealed out of the E90. Quote Link to comment Share on other sites More sharing options...
cetoole Posted February 22, 2010 Report Share Posted February 22, 2010 Not if my theory is that the ESP950 bias is ~300v, not ~600v. There are definitely construction issues in the headphones, so I really have no problem believing that there is something going on beyond just the bias voltage. Quote Link to comment Share on other sites More sharing options...
cclragnarok Posted February 22, 2010 Report Share Posted February 22, 2010 My ESP950 also seems to squeal louder and more often from my Headamp KGSS. Quote Link to comment Share on other sites More sharing options...
spritzer Posted February 22, 2010 Report Share Posted February 22, 2010 Well Koss does state the bias voltage to be 600V: SPECIFICATIONS ESP/950 Physical Specifications Size of earcup: Approximately 150 mm h x 100 mm w x 40 mm d (including cushions) Cushions: Large foam filled leatherette type for high ambient noise isolation and conformance to facial structure. Headband: Extendable, stainless steel band with self adjusting, pivoting yokes and headband release mechanism. Headband Cover: Wide leatherette style vinyl with 12 mm thick polythylene foam padding. Yokes: Horizontal and vertical pivoting with integral headband lock and detach mechanism for convenient storage Weight: 12.45 oz. (353 gm) Cord Length: 47 inches (182.9 cm) Extension cord length: 72 inches (182.9 cm) Electroacoustical Specifications Frequency response: 8 Hz to 35,000 Hz Sensitivity: 104 dB, 100 Vrms differential input a 1 kHz Diaphragm radiating surface area: 7 sq. in. (45.6 sq. cm) Diaphragm: Ultra-low mass 1.5 micron C grade polyester film electronbeam coated with a proprietary semiconductive material 250 A thick. Acoustic Design principal: Circumaural open air design incorporating minimal acoustic damping. E/90 Energizer/Amplifier Physical Specifications Dimension: 65mm h x 110 mm w x 155 mm d Weight: 17 oz. (482 gm) Electrical Specifications Frequency response: 1.6 Hz to 50,000Hz (-3dB points) 100 vrms differential output Distortion (THD+NOISE): 0.001% at 1kHz and 100Vrms differential output Input Impedence: 100k ohms Input level: 1 Vrms (for full power output) Voltage Amplification: 60 dB Audio output voltage: 600 Vrms differential, 2300 Vrms push-pull with soft limiting Channel Separation: - 80 dB at 1 kHz, 100 Vrms differential output Signal to Noise: -100 dB at100 Vrms output Bias voltage supply: 600VDC But I've been working after similar lines that the Stax bias supplies simply aren't compatible. 10M/10M will half the voltage but it is strange that there is no ballast resistor. I'm going to ask KG... Quote Link to comment Share on other sites More sharing options...
cetoole Posted February 22, 2010 Report Share Posted February 22, 2010 I know what the Koss spec is, and I am wondering if it is simply wrong. Both my analysis and measurements of the E/90 I have right here show 300v. Pretty obviously this isnt a recent change, as my PCB is dated 7-11-90, and has no obvious modifications made to it. I tried adding in a 5M ballast resistor inline with the ESP950 driven off the Stax amp, no change. Its just fine plugged into normal bias. I wonder if just some drivers are able to handle the voltage and some arn't. Also explains why Smeggy didnt have catastrophic results when he ran his ET1000 off the E/90. Quote Link to comment Share on other sites More sharing options...
spritzer Posted February 22, 2010 Report Share Posted February 22, 2010 Could be but could you do one thing for me, measure the amp output. If the amp sits at -300V then a +300V bias would result in +600. I seriously doubt that this is the case but it was something which KG did with his DC coupled tube amp. Quote Link to comment Share on other sites More sharing options...
Dreadhead Posted February 22, 2010 Report Share Posted February 22, 2010 I know what the Koss spec is, and I am wondering if it is simply wrong. Both my analysis and measurements of the E/90 I have right here show 300v. Pretty obviously this isnt a recent change, as my PCB is dated 7-11-90, and has no obvious modifications made to it. I tried adding in a 5M ballast resistor inline with the ESP950 driven off the Stax amp, no change. Its just fine plugged into normal bias. I wonder if just some drivers are able to handle the voltage and some arn't. Also explains why Smeggy didnt have catastrophic results when he ran his ET1000 off the E/90. Good find man. I never thought to measure this since I assumed it was fine but yes mine most definitely squealed out of the KGSS until I guess I lucked int a pair that worked after 3 rmas. All pairs except the first one were dead quiet on the E/90. This would explain an awful lot. Quote Link to comment Share on other sites More sharing options...
mypasswordis Posted February 22, 2010 Report Share Posted February 22, 2010 This would explain a lot. I was wondering how pretty much every ESP950 had problems, when Koss isn't otherwise known for QC issues. Nice discovery, Colin. Quote Link to comment Share on other sites More sharing options...
spritzer Posted February 22, 2010 Report Share Posted February 22, 2010 Since I don't have an E.90 here I asked Kevin to test his and see what's what. For the record I've never had any problems with the ESP950's I've owned over the years, on Stax amps, adapters, Gilmore amps and that crazy DC-DC supply Marc came up with. Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted February 22, 2010 Report Share Posted February 22, 2010 damn Colin. Nice work there. Quote Link to comment Share on other sites More sharing options...
cetoole Posted February 22, 2010 Report Share Posted February 22, 2010 Could be but could you do one thing for me, measure the amp output. If the amp sits at -300V then a +300V bias would result in +600. I seriously doubt that this is the case but it was something which KG did with his DC coupled tube amp. Nope, all outputs measure under 1v offset. Quote Link to comment Share on other sites More sharing options...
nikongod Posted February 22, 2010 Report Share Posted February 22, 2010 did you account for the input impedance of the volt-meter loading down the output impedance of the bias supply? Every STAX amp i have measured (attempted to...) measure bias on at the jack says ~200-260V (its been a while) Quote Link to comment Share on other sites More sharing options...
cetoole Posted February 22, 2010 Report Share Posted February 22, 2010 My meter is rated for 10M input impedance while measuring DCV, so that in parallel with the 10M resistor to ground in the bias circuit would give 5M. 600v through a 10M/5M divider should give 200v, which is what I measure when doing this. Also, the 300v figure is just from looking at the circuit (10M resistor to bias pin from ~600v rail, 10M||0.022uf from bias pin to ground. Quote Link to comment Share on other sites More sharing options...
Kabeer Posted February 22, 2010 Report Share Posted February 22, 2010 What does this effectively mean in the big scale picture? Quote Link to comment Share on other sites More sharing options...
deepak Posted February 23, 2010 Author Report Share Posted February 23, 2010 This would explain a lot. I was wondering how pretty much every ESP950 had problems, when Koss isn't otherwise known for QC issues. Nice discovery, Colin. Both my ESP950s squealed on the E90. I wasn't able to try other amps. The third one was fine. Quote Link to comment Share on other sites More sharing options...
BoilermakerFan Posted February 23, 2010 Report Share Posted February 23, 2010 What does this effectively mean in the big scale picture? It's potentially part of the problem with Koss driver failures and I'm not sure I would use them off a Stax Pro jack on the SRD7. Quote Link to comment Share on other sites More sharing options...
Salt Peanuts Posted February 23, 2010 Report Share Posted February 23, 2010 If my memory serves me right, my ESP950 squealed on both E90 and SRM-1 Mk2. I sent them in to Koss service and when I got them back, they didn't squeal on E90 but continued to do so intermittently on SRM-1 Mk2. Quote Link to comment Share on other sites More sharing options...
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