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Post by PinkFloyd on Nov 24, 2008 13:04:23 GMT
A comprehensive list of old secondhand headphone amps that often come up on ebay, what you can do to make them sound like new and how they compare to current amps......
I've been meaning to do this for some time and hope to get the full list up by March 2009.
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Post by rossman on Nov 24, 2008 14:41:49 GMT
I will look forward to seeing this Mike, it will be really useful info. Watch the prices rise on ebay once the list is in place though
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rickcr42
Fully Modded
Rest in peace my good friend.
Posts: 4,514
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Post by rickcr42 on Nov 24, 2008 19:49:39 GMT
many times the topology/electonic circuits in vintage electronics are superior to current offerings because things were more often fully engineered to perform the job rather than cater to audiophile whim or cosmetics.The downside is electrolytic capacitors have a very real "shelf life" so anything over five years old usually means a total re-cap of all polarized caps with most other mods being more conforming to modern ideas on what is good rather than any real improvement and especially so when modern high speed parts (opamps for instance) are cobbed into a design optimized with a much slower part in mind so the bypassing/decoupling scheme may also need a total revision which begs the question "is it then the same amp with revisions or an entirely new design ?" Sometimes the sum IS greater than the whole and if a particular circuit is ptimised to sound good with available parts changing one or many will too often result in a sound that is schizoid rather than homogenous so if it is updating a known but good design in order to compare with modern amps a modest update would be more telling than a radical one
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Post by PinkFloyd on Nov 25, 2008 12:10:09 GMT
many times the topology/electonic circuits in vintage electronics are superior to current offerings because things were more often fully engineered to perform the job rather than cater to audiophile whim or cosmetics.The downside is electrolytic capacitors have a very real "shelf life" so anything over five years old usually means a total re-cap of all polarized caps with most other mods being more conforming to modern ideas on what is good rather than any real improvement and especially so when modern high speed parts (opamps for instance) are cobbed into a design optimized with a much slower part in mind so the bypassing/decoupling scheme may also need a total revision which begs the question "is it then the same amp with revisions or an entirely new design ?" Sometimes the sum IS greater than the whole and if a particular circuit is ptimised to sound good with available parts changing one or many will too often result in a sound that is schizoid rather than homogenous so if it is updating a known but good design in order to compare with modern amps a modest update would be more telling than a radical one Totally agree Rick..... a recap is absoloutely essential with old gear as is a solder mop and reflow on each joint, it's amazing just what a difference a new set of caps makes to the sound.... as if "life" has been injected back into the old girl. I have a few "oldies" I'll be covering in depth which will include X-CANS (V1), QED MB45, HFN009 (headcase), Project headbox and this puppy which I won yesterday.......... It is the "Eagle International" HA10 with "HA" standing for "headphone amplifier". I don't know much about this one as they don't come up very often but from the look of it I'd say it was 1970's / 80's vintage. I do remember Eagle International though, a British company who made PA gear (mostly industrious looking stuff) and, as far as I know, they are no longer in business. She certainly "sounds" interesting from the write up: Specifications:
Output Power: 50mW. per channel at 8ohms.
Input: Mag. 5mV
Xtal. 100mV
Controls: Volume, left and right
Battery: 9V. DC. Eveready 216 ro equivalent
Circuit: 10 Transistor preamplifier with RIAA compensation and out put with complementary transistors and OTL circuit.
Case : Walnut
Size : 7 1/4" w. 4 1/4" d. 3" h.Features:
1. OTL (Output Transformerless) all transistor circuit for minimum distortionless sound reproduction.
2. For all magnetic, crystal, or ceramic phono cartridges. RIAA compensation built-in for magnetic cartridges.
3. Individual volume controls for each channel.
4. Input for simultaneous operation for two (2) stereo headphones.
5. Battery operated with spare compartment for extra battery.
6. Beautiful walnut finished cabinet.Full under the bonnet pics and details to appear as soon as she arrives as Rock Grotto HQ
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robertkd
Been here a while!
Electronics Engineer from sunny Queensland
Posts: 111
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Post by robertkd on Nov 25, 2008 12:57:24 GMT
krap it's WOOD like,.. my recollection of gear from the 70's and even 80's is that it was the epoch of noise, sweet little transistor things they were but noisy
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Post by PinkFloyd on Nov 25, 2008 14:38:25 GMT
krap it's WOOD like,.. my recollection of gear from the 70's and even 80's is that it was the epoch of noise, sweet little transistor things they were but noisy Yes..... they were very fond of wood back in the day before all these "green" arseholes came along crying "rain forest" every time they saw something made out of wood.... funny how it's turned out though with MDF / Chipboard crap going into landfill once it goes out of fashion (every year in some instances) but of course...... MDF / Chipboard isn't made from wood is it? ;D Give me a quality piece of WOOD that will last 1,000 years over some cheap, tatty decorated MDF any day. God only knows what the EAGLE will sound like.... one thing is for sure, it doesn't deserve to go into a landfill site just yet does it? Even if it's the shittiest sounding amp of all time the enclosure can be put to good use and £22 is a small price to pay for WOOD and all the other bits and bobs that can be re-used.... Half the fun of buying these unknowns is in popping the hood and seeing what's inside.... jesus, people pay £10 to see a crap film, £22 is well worth the entrance fee to have a look at the pRon isn't it? Of course, I will share the EAGLE pRon with you all as soon as the EAGLE lands
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Post by PinkFloyd on Nov 25, 2008 19:34:29 GMT
And if a restoration as close to the original caps as possible.... keep the unit true to original spec. Alternatively.... totally bastardise it beyond recognition with all sorts of weird and wonderful components and call it "modded"
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rickcr42
Fully Modded
Rest in peace my good friend.
Posts: 4,514
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Post by rickcr42 on Nov 25, 2008 21:23:13 GMT
The Eagle International may be a prime candidate for "gut it and replace it" it being attractive enough to look good on any shelf either stand alone of as part of a larger system but only if you lose the phono inputs which could then be made into additional line level inputs that in combination with the line and headphone outs make for a tidy package system control pre/monitor amp(hence the stand alone part ). I say this only because I have never heard of the amp in my life and that means a lot coming from someone who suibscribed to all the better audio and electronics magazines from 1970 up until the "Great Magazine Death Virus" sometime in the late eighties/early nineties when many of my favorites either changed into something else (Popular electronics>Popular computing) or went bye bye altogether Audio Magazine for one ). so even if the amp was a "sleeper" it would have had at least some underground chatter and I don't recall any so either 1-The device was a good one but produced in such small numbers or availability so limited it got little exposure or 2-Not worth commenting on. If the former then maybe a re-cap along with a precision resistor and potentiometer upgrade and possibly a power supply cleanup would be in order to bring forth the former glory AND maybe some new glory the available parts at the time (or price point niche) did not allow. If the latter,a real possibility considering the likely audio epoch (days of Dynaco solid state and more bad sounding SS than good ) more likely the amp is unknown because it used a bad circuit topology or grainy sounding transistors (common then) or both making any updates more throwing good money after bad then having a starting platform for good sound (hint,if the transistors are PNP/NPN pairs and those pairs 2N5210/2N5087 the foundation for going further is a sound one ) either way it is NOT ugly (to my taste anyway) and would make a nice addition to any desktop or nightstand or even gear rack if it needs a bit of "warming up" because it is all stark black or all stark natural aluminum with no wood or brass "bits" to make it feel more human freindly rather than lab rat high-tech
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Post by PinkFloyd on Nov 26, 2008 13:13:48 GMT
The Eagle International may be a prime candidate for "gut it and replace it" it being attractive enough to look good on any shelf either stand alone of as part of a larger system but only if you lose the phono inputs which could then be made into additional line level inputs that in combination with the line and headphone outs make for a tidy package system control pre/monitor amp(hence the stand alone part ). Yup.... a nice compact wooden enclosure that would probably scrub up very nicely with a bit of sanding and maybe some tung oil I'm sure it wouldn't be too hard to remove "eagle international" from the facia either..... Of course, if the amp isn't too bad then "eagle international" will remain.
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Post by PinkFloyd on Nov 30, 2008 18:40:35 GMT
Rick, the Eagle has landed! I am still down in Wales and haven't seen it but from what I've been told it is absolutely PRISTINE and comes in original box. Made in JAPAN, full instructions (also includes circuit diagram), original box.... MINT condition. Apparantly the enclosure is SOLID teak and the fascia brushed aluminium. Who knows.... this thing could have been known in Japan back in the day and possibly never made it to the western world. We only get their second rate stuff over here, they keep all the good stuff for themselves...... I can't wait to return home to see this puppy
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Post by PinkFloyd on Nov 30, 2008 18:53:00 GMT
BTW...... this is the type of thing Eagle used to make:
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Post by PinkFloyd on Nov 30, 2008 21:06:39 GMT
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Post by PinkFloyd on Dec 8, 2008 16:51:19 GMT
Rick...... the transistors are B175 / B172 germanium types (in a metal can) I'll pop the board out for a closer look but in the meantime here's a preview of the Eagle........
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Post by keith on Feb 1, 2016 14:38:58 GMT
I just picked up one these on eBay for £10. Am I right in thinking that the mag inputs would work connected directly to a turntable?
Did you ever do anymore with yours?
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Post by PinkFloyd on Feb 1, 2016 20:45:02 GMT
I just picked up one these on eBay for £10. Am I right in thinking that the mag inputs would work connected directly to a turntable? Did you ever do anymore with yours? Hi Keith, Mine is still in the box....... I never got round to doing anything with it...... as Rick said, at the time, it was pretty much an unheard of amp full of pretty crappy 1970's germanium transistors and certainly not worth me restoring as I don't have a turntable OR any vinyl these days...... this was only ever going to be a "rip the guts out and fill with ingredients of your choice" type purchase but I never got round to it. You are correct, you can connect it to your turntable..... that's what it was designed for. I'm not quite sure what it will sound like (as I don't have a turntable / vinyl these days) but give it a go and let me know what you think. It will OBVIOUSLY need a damned good re cap (new capacitors) and rewire (not to mention cleaning / replacing the pots) but you should get an idea of what it has to offer from a brief listen. I'll get mine out (you show me yours, I'll show you mine) in the next few days and will have a look under the hood, I'll also take detailed photos so the Analogue / turntable / Moving coil / "valve generation" expert (Alex) can pitch in with his comments. Alex.... that wasn't a "dig", by the way, that was my sense of humour This sure is a blast from the past but, fortunately, I still have my Eagle in it's nest. Give me a couple of days Keith. All the best, Mike.
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Post by keith on Feb 4, 2016 6:16:59 GMT
Mike,
Thanks.
Still waiting for the postman to drop mine off. As soon as she lands I will take some pictures, connect her her up and have a listen.
Keith
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Post by keith on Feb 6, 2016 12:06:13 GMT
Amp arrived with battery terminal snipped off and missing. This and the distraction of a new pair of cans (unused Grado X Bushmills) will delay any listening.
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Post by PinkFloyd on Feb 9, 2016 20:19:28 GMT
Amp arrived with battery terminal snipped off and missing. This and the distraction of a new pair of cans (unused Grado X Bushmills) will delay any listening. Hi Keith, Sorry to hear that, that's a bit of a bummer Post your thoughts once you get it up and running, you'll probably "need" a bottle of Bushmills to make the distortion a bit more bearable Nah, only kidding Mike.
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