dc
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Posts posted by dc
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that does look pretty sweet...
and i am pretty lazy!
but damn, the price =(
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Ey spritzer you seen/heard this baby?
Hopefully your Japanese is better than mine but I see D I Y in its description here: http://staxt2.hp.infoseek.co.jp/6BX7.htm
I think this is the schematic for it:
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May you have many more years of prosperity and good health
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just checked out the link, and it's described as the "Eastern Electric MiniMax BBA preamplifier"
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The only similar device I would be interested in is Eastern Electric BBA, which is more of impedance matching device with variable gain. Very interesting concept...
http://www.dagogo.com/EasternElectricBBA.html
doesn't that makes this a pre-amp then?
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I think a lot of tube buffers benefit comes from their impedance matching
ie. ultra high impedance to the source, low impedance to the amp
that way sources with output stages that have trouble with heavy loads don't have to struggle so much
that is my understanding of it.
oh and the tube flavour is pleasing to some.
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Yeah I might do that.
I appreciate the link to your resistor burning thread btw.
Before each measurement of the resistors near the buffer transistors I took a deep breath in and then out and measured on the side away from the transistor legs for extra good measure
Decided not to risk adjusting the trimmer while measuring so I measured, got out, adjusted the trimmer, got back in and measured and repeated until I got where I wanted to be. Took a few goes but it's at least there's no smoke
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yeah one of the first things i checked actually, but i just checked on the outputs between left and ground and right and ground - all stayed <10mV until about 80% of the pot at which point it quickly shot up to like 45mV but there's no way i'd ever go past half way on the pot
OL to IG = 1.5mV
OR to IG = 2.5mV
OG to IG = 0.1mV
With a little help over @ H-F I think I solved the problem with the OPA637/OPA627 opamp combo doing freaky deaky things. it turns out i mis-intepreted my previous readings (i'm a newb)
I measured 45mV across the output resistors but forgot that that is voltage NOT current, and are supposed to divide that by the value of the resistor to calculate current which in this case is 2.2ohm which works out to be just 20mA - which was not enough juice for the DT880 and making the OPA637 cranky
I've now adjusted it so I measure 65mV which equates to about 29.5mA and works just fine now with any of my headphones
the AD843 combo still isn't happy in the PPAv2. AD744 comp pin out with AD829 in ground is still my favourite, and even better with the higher bias on the output transistors.
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wtf. surely he didn't let it go for $23.50...
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Well I took all the essential measurements
Gain: ~9
Output buffer bias: 45mV
Opamp bias: 1mV
However I experienced some strange things.
Only when using my DT880s I got some wierd funky as distortion/white noise when I turned up the volume knob and it got to a loud part of the a song it would go out of control and then even if I turned down the knob the crazy noise stayed. Is this oscillation?
It happened in a couple of opamp combinations:
2 x OPA637 + 1 x OPA627
and
3 x AD843
It only happened with the above opamps and with the 250 ohm DT880, does anyone know what's happening?
Other headphones/opamps used were K501, K701, DT531, 3 x AD8610, 3 x OPA627, 2 x AD744 + AD829.
I've ruled out oscillation due to low gain, unless I'm reading/mesuring the gain resistors wrong (possibly) what else might cause oscillation or whatever's happening?
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Yes, you NEED to open some ports for bit torrent to work to its fullest potential (if you're behind a router that is, if you're directly connected to the net then don't worry)
Due to the nature of torrents they're de-centralised, Peer-to-peer networks, so as the name suggests you discover other peers, through the peers you're already connected to.
So the tracker will get you started and everyone uses that as a single point of reference, but it doesn't store a list of people who have that file, so the best thing to do is stay connected and let it discover others.
Generally seeders are better since they have the complete file, but so long as the complete package is available out there the more people the better. Oh, also configure your torrent software to allow as many simultaneous connections as your computer/connection can handle - this will help speed things up.
The biggest PITA is when there are no seeders and everyone is missing the same section of file because it never ever got uploaded and the seeders have disappeared =(
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800-1000$ is the norm but you can find higher and lower as usual.
damn, i shoulda snapped up the 717 that an aussie was selling for AUD$700. too bad i was broke =(
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Your logic does seem right about not fiddling, apparently this amp is 2 years old and hasn't had any issues so might be a case of "if it ain't broke..."
The soldering on it is very good too, it almost look like it was machine manufactured. Casework and wiring leaves a bit to be desired for though, but that's ok - hammonds anyway.
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how did I know n_maher be one of the first to respond =)
I'm very impressed with it at the moment considering I've only had so little time with it - a very good sign. But it could be new toy syndrome...
I'm aware the minimum recommended gain for the OPA 637 is 5, i believe the amp is at a gain of 8, I will be using the OPA627 for ground so should be ok.
the AD744 (comp pin out) + AD829 is similar to that of the LISA III
thanks for the links, i've already put the tangent page on my list of to-reads before fooling around. resistor smoking sounds interesting though
i'll report back if i've killed the thing =\
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sorry to dig up an old thread, but I believe the OPA2107 is a dual opamp so won't work in the PPA
I do however need some help with my PPAv2 that just landed
At the moment there are 3 x AD8610 opamps in there. I've got a few combos I plan on using: 2 x OPA637 + OPA627, 3 x AD843 and 2 x AD744 + AD829
Now, my understanding of this amp is limited atm but I believe there are trimpots on the board for biasing 1. opamps 2. output buffers
I've got a digital multimetre and I can manage to pull things apart and put them back together if need be, but how the amp works and what all the parts do is out of my scope.
I've had a quick look around and bookmarked a few links but just wondering if anyone can point me in the right direction for where to measure the current draws for 1. opamps 2. output buffers
I am of the understanding the opamps should be given between 1-2mA and the output buffers anywhere up to 50mA
So far I haven't touched anything except adjust the STEPS so it's outputting exactly 24v
I'm going try to familiarise myself with the amp's sound so I have a benchmark for tweaking but already this amp is sounding very good.
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their awesomeness
well, they don't always have as tactile a bass response (if headphones can even have tactile bass)
they're generally more detailed and effortless in their sound than dynamics
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If I cryo my sister in law, will she stop yammering at our family get togethers and start to make some sense?
no she just needs to be burnt
in
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stretchy like latex?
how do you measure stretchiness? did you DBT?
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I reckon burn in should happen first, that way when you cryo treat it all the burnt in goodness gets locked in, sort of like the claims they make with frozen vegetables
It would be terrible to lose all that burnt-in goodness ie, experience the un-burnin phenomena
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don't forget the cryo treatment!
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man they sure squeezed a lot into a small area
what's more surprising is the number of through hole components that they got in there
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never quite understood the dislike for K701s =\
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He could make a cable for the SR-Omega though...
I was hoping more along the lines of the Stax SR001-MK2 portable system
I mean afterall, his forte seems to be in cables for portable rigs right?
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I still can't figure out how to make the "
UPS Sucks
in Off Topic
Posted
damn that's no good. were the goods insured?
i go USPS because it's cheaper and quick enough for me
trackable options to australia are all too $$$ anyway so i have to take my chances