Except me. I agree that perception may be different, but not the basic functioning of the ear mechanism.
jan didden
Sounds like time for an experiment, try listening to some of your favorite recordings before and after listening to cocktail party noise for 30 minutes.
Although we could just implant electrodes to measure the ear muscle response at home and at a live event, of course the down side is it may leave you deaf. But I know you will do it for science!
But as I started this I said this is an area where we disagree.
... or listening to your fav live music after listening to cocktail party noise for 30 minutes. What's the difference? Of course, good investigation practise ask for 'all other things being equal' if you want to look for changes in a single parameter.
jan
As long as you can get to your live event without experiencing any other stimulus. But if you want to try something, next time wear earplugs up until the event starts.
simon7000,
some reading around the subject could give fewer arbitrary assertions. The human auditory system is a product of millions of years of evolution and most clearly did not evolve to interpret reproduced hip-hop music. The ear`s function does not change except an impairment through aging or injury, brain processes do change constantly, thereby the perception of the outside world, including the perception of sounds.
some reading around the subject could give fewer arbitrary assertions. The human auditory system is a product of millions of years of evolution and most clearly did not evolve to interpret reproduced hip-hop music. The ear`s function does not change except an impairment through aging or injury, brain processes do change constantly, thereby the perception of the outside world, including the perception of sounds.
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speculation about hearing variability, plasticity really doesn't seem too helpful in amplifier thread except to establish outer limits of required electrical signal amplification accuracy
the whole amplifer as source of effects to make listening more pleasing - perhaps by mind reading seems misplaced here
are you really going design, build, keep a array of power amps to swap out because you have a head cold, just had great sex, your dog died?
the whole amplifer as source of effects to make listening more pleasing - perhaps by mind reading seems misplaced here
are you really going design, build, keep a array of power amps to swap out because you have a head cold, just had great sex, your dog died?
That would mean a house full of amps.
I now have a pair of lateral , EF2 and Bob's triple BJT current stages in separate cases. I plug in the 3 most popular topologies, (luxman-hawksford cascode , blameless or symasym) and listen , listen , listen. The triple and the laterals are distinctively better sounding regardless of voltage stage used. This proves that an unloaded VAS is a worthy goal and that sound quality is a variable that is design dependent (they do NOT all sound the same).
. The Luxman (Bob's book - page 144 with a Hawksford cascode VAS) , really comes "alive" unloaded (triple) , sounds average on an EF2. This is with large inefficient speakers and loud , complex passages.
Hopefully , out of the 9 combinations , I too... can pick one that will please.
PS. unfortunately , Class A is out of the question. They just don't work well in a 40C environment (just too dang hot here).
I'm not a troll , but it was so easy to get everybody OT with a simple ?
OS
While I went to the primary literature to suggest that tensor tympani and stapedius muscles are active at normal listening levels, it is purely speculative whether they affect anything OTHER than the amplitude of the signal that enters the cochlea. All of our music systems have volume control!
BTW, at very loud (or distortion-prone) venues I use 'musician's earplugs', which contain -30 dB flat frequency attenuators (held by castings made to the shape of my ear canal). I have more fun with no damaging after-effects!
Frank
I would agree there.. Musician's earplug's are most useful implements in all manor of music venues where in some case's such as the local pub when a band crank's up the amp's to such distorted levels.. the younger one's will in time fined out that loud, distorted music will cause damage there ear's..
And this is why we DIY.... You take one of Bob's fine examples of voltage stages and "free it" from OEM economic factors (cheesy 10Kuf PS caps , barely sufficient trafo and output stage) , NO earplugs needed. Loud CAN be an relative minimum distortion experience. A 200W amp w/ 400w peaks can (should) sound just as good "cranked" as it does at the "first watt". Totally immersed at 120db should be an good experience (spine chillin') , not one where earplugs are needed ...
. The local pub needs more headroom !!!As far as hearing is concerned , at these levels ... ears will try to protect themselves with much wax generated.
OS
And this is why we DIY.... You take one of Bob's fine examples of voltage stages and "free it" from OEM economic factors (cheesy 10Kuf PS caps , barely sufficient trafo and output stage) , NO earplugs needed. Loud CAN be an relative minimum distortion experience. A 200W amp w/ 400w peaks can (should) sound just as good "cranked" as it does at the "first watt". Totally immersed at 120db should be an good experience (spine chillin') , not one where earplugs are needed ...
As far as hearing is concerned , at these levels ... ears will try to protect themselves with much wax generated.
OS
These are good points, OS, but I would say with the caveat that the program material has good dynamic range (crest factor). With good, uncompressed music, those short peaks that require hundreds of watts are very satisfying. Unfortunately, we don't experience enough of that kind of music.
Cheers,
Bob
Anyone know of a reliable source for purchasing the Phillips/nxp version of the BD139/140?
I've tried the obvious sources, and I'm not interested in excess inventory houses or ones with $100 up minimums.
Bob , I have a "apples and oranges" question. In my final choice of devices for your triple output stage ("DBT") , I have 2 choices. #1 is to keep the same (1381/3503 - njw0302/0281 - njw0302/0281) as my pre-driver-output choices. All these are 30 mhz + Ft devices and I have run them successfully in the triple.My other choice is the NJW21193/4 ,they are only 4 mhz w/ much higher SOA and 60 Hfe .... just as cheap , (2$) at mouser.
My real question is 2 part , would it be detrimental to have devices with "mismatched" Ft in a BJT triple ... for example (mje340/15mhz - njw0281/30mhz - njw21194/4mhz) pre-drv-OP ? And if you did use these would it increase the margin for stability beyond the triple with the faster Ft devices. I pondered this after researching the Leach amp with it's slow TIP's (10mhz Ft) and super slow to-3 MJ's (2mhz ). My concern is with how I will implement it.
My voltage stage , predriver and final njw0281/0302 drivers will be on a small PCB and the final 3 pair OP devices , zoble , and OP inductor on a separate board bolted to the main heatsinks. These will be connected by 2 wires (+drive and - drive) to the driver/ VS board. Being of such low impedance and much shorter than a typical leach build (I have seen real long wires) , will I have problems with parasitics ?
Just bought a vintage altec lansing 2204 for US$20 (rare-below) to put my "bobamp" in , huge 800VA trafo and large heatsinks ... just have to choose my outputs and final layout
.
OS
My real question is 2 part , would it be detrimental to have devices with "mismatched" Ft in a BJT triple ... for example (mje340/15mhz - njw0281/30mhz - njw21194/4mhz) pre-drv-OP ? And if you did use these would it increase the margin for stability beyond the triple with the faster Ft devices. I pondered this after researching the Leach amp with it's slow TIP's (10mhz Ft) and super slow to-3 MJ's (2mhz
). My concern is with how I will implement it.My voltage stage , predriver and final njw0281/0302 drivers will be on a small PCB and the final 3 pair OP devices , zoble , and OP inductor on a separate board bolted to the main heatsinks. These will be connected by 2 wires (+drive and - drive) to the driver/ VS board. Being of such low impedance and much shorter than a typical leach build (I have seen real long wires) , will I have problems with parasitics ?
Just bought a vintage altec lansing 2204 for US$20 (rare-below) to put my "bobamp" in , huge 800VA trafo and large heatsinks ... just have to choose my outputs and final layout
.OS
Attachments
I think the recomendation for a triple is for the transistor speed to be monotonic increasing from output to VAS
this is enabled by the smaller die size, lower parasitic junction C for the lower power, current devices
amplifier global loop gain intercept is usually limited by the output speed - faster transistors enable more feedback correction and/or better phase margins - but may demand greater care/extra measures to suppress local RF oscillations
the slowest transistor in the triple will dominate the total speed
the 1st Q after the VAS can sometimes be the same as the VAS, or possibly several of them paralled
this is enabled by the smaller die size, lower parasitic junction C for the lower power, current devices
amplifier global loop gain intercept is usually limited by the output speed - faster transistors enable more feedback correction and/or better phase margins - but may demand greater care/extra measures to suppress local RF oscillations
the slowest transistor in the triple will dominate the total speed
the 1st Q after the VAS can sometimes be the same as the VAS, or possibly several of them paralled
Like this ? :
NJW21194/3 - 4mhz - OP
NJW0281/0302 - 30mhz - driver
Ksc-a3503/1381- 150mhz - predriver (and VAS)
I am not trying to overcomplicate things , but with bob's "DBT", the driver/predriver Vbe vs. temp. should be the same (or close). With the ksa/c's and the NJW's on the same heatsink there is a slight positive coefficient (driver current increases slightly with temperature ). Mje350-340's and NJW's just about cancel out (0 coefficient) ,Vbe wise ... leaving just the OP's Vbe to compensate for. This is one of the main attractive features of this circuit that caught my attention in Bob's book.
With my now standard adjustable coefficient CFP Vbe circuit (thanks PMA and keentoken) , I could easily compensate for the non-perfect pre/driver Vbe "balance". Also , in it's prototype form , it (the dbt) works so well ... I actually might go all the way and use thermal track outputs to have the perfect BJT current stage (thermally and electrically).
I just wondered what effect the MJE340-50 would have on the whole "package" used as the predriver.
OS