When I was little I had my first tube setup... Radiola-type combine with record player, reel tape recorder and receiver. I remember strong booming, warm sound after all those 30 years as if today. I have been listening and collecting some vintage SS stereo for a few years and wanted to try some hi-fi tube amp.
As an opportunity presented itself, I got my hands on this all-original Eico ST-70. It's factory built (not a kit), with factory stickers, QA pencil marks, with a few rusting dots on its chassis and well-preserved everything else aside from being covered in "protective" layer of dust, which also suggested that its cover was probably never removed. Maybe, part of my luck was that smashed fuse holder that it came with, so someone just quit on this amp years ago not being able to simply turn it on. Being a superstitious person, I went for a near complete rebuild without even trying to turn it on first. The tubes were all original, including those EICO/Westinghouse marked 7591, GE 6sn7, Mullard 5AR4/12ax7/7247. I measured almost all resistors and found that those plastic ones tested at about 20 to 30% over the value and those were changed along with all above-1/2 watt resistors (excluding those ceramic coffins). I went for Solen caps for a start, to give me some thinking time for further upgrades down the road. I re-stuffed the can power supply caps with modern electrolytics, messy job, but still fun. Changed power cord to 3-wire one and added X2 and Y2 safety filter caps along with ferrite beads where applies, plus inrush current limiter. Banana speaker terminals. I did all the mods I could find on the Net except those requiring to remove original wiring (center channel, balance, etc. which would be good thing to do, though, I think). I constructed my dim-bulb device, as I don't own a variac, to limit current while gradually bringing the amp to full AC power. Balancing and biasing this thing was pretty confusing even after reading instruction manual. Bias control layout is simply counter-intuitive, so I panicked, initially, failing to get those .38v. However, when I finally got used to it, the amp biased without any problem. I was missing two halves of those dual pot knobs, so I just vandalized my shiny, but useless Lafayette SS receiver for its aluminum controls and Eico looks a little better now.
I recently got this TOTL, 150w/ch Kenwood KA-3300D digital integrated with DLD and VIG systems, with total of 72,000 uF, cooling fan and huge trans... It is a very nice dynamic amp and beats anything around it by power output, but still sounds drastically different and a little flat compared to my EICO, and I am kinda shocked by that. I guess it's all in tube magic. I listen to more of electronic music; so, some say that tube amps are not cut for this style, at least with tube rectifiers... I think that EICO sounds very nice with all kinds of music, actually. It's just different, but never weird. Must be that famous Mullard rectifier and huge trafos which do the trick.
i have listened and owed alot of tube equipment in the last 5 years or so but i have to say the eico-70 is probley 1 of the best amps i ever listened to. i recently just bought my eico-st70 and the matching eico-st97 tuner at a yard sale just down the street from me. i saw it when i was driving my car from the other side of the street and i pulled over probley cutting off acouple of cars. i wasn`t 100% sure if it was what i thought it was. sure enough after racing out of my car i see a price tag on it for $10.00 thats right $10 that included the tuner. i only had a $20 bill and they had no change so i pulled out $7.25 out of my pocket and they excepted it. i was in my glory i could not believe after waking up every saturday being disapointed time and time again i finally got something worth while.to make things even better i opened up the lid to fine it still has all it`s original ecio mullard tubes in the amp and the tuner. man what a deal. i have seen these on ebay and have been tempted to buy one but was affraid of disapointment. i always thought my dynaco st-70 and heathkit aa-121 were the best thing until i listened to the eico. the midrange is to die for i could not believe the detail in the midrange and to be honest it seems to have more punch then my dynaco or heathkit. the base is alot tighter then the dynaco aswell. do not get me wrong i still love my dynaco stuff but if you compared the to you will agree the eico has a much better range in these fields. the ecio looks butt ugly but the quality and sound makes up for it by far. i would have to rate this and and aswell the tuner 5 out of 5 the tuner picks up alot of stations and also sounds amazing.
AS with other reviewers,this amp came to me,for nothing,covered in years of dirt from being stored in a workshop.Took it home and plugged it in.Right off the bat i knew it was,or could be,a gem.Power washed it(kidding),re-tubed with E-H and Sovtek(Fishers for the phono section)as all tested bad and were original in '62,replaced a couple suspect caps,gave it some decent rca's and banana binding posts(will get around to the power cord),and my,my,my.
This thing has amazing sound.Incredible presence,real bottom end,midrange so nice....but the real treat are the incredibly extended highs.I have the original building and service manuals,and this amp was rated 10-50,000 at 2 watts(1pc) driving 8ohm,with 35wpc full out.Now,I know some folks are into the numbers thing,but I am not.Haven't a clue what this thing would do under that kind of scrutiny,and I don't care,frankly....just got these ears.The amp sings.
Took a few hours after the re-tube to really get things tight,but after that,pure magic....detail....slam...the whole nine yards.
And it should....got some very major metal powering it.
We are done with the esoteric stuff...ta-ta Jolida,Carey,Synthesis,SETs of all kinds( definition of SETs >>is like trying to shove an elephant through a funnel).
Maybe if i had a gazzilion bucks to spend on them Tenors...but I don't,so there!
Used with Digital sorce only so far,but will get into the wax soon.
Sorce> Arcam FMJ/M-F sacd
Speakers> Triangle Celius on granite
Cables> Van den hule,XLO
Power conditioning>Blue Circle
Racked on granite.
if you see this amp get it.rewire output sockets for 6l6....easy mod and no more hard to find and expensive tubes. play with it....caps, resistors, remove obselete switcthes if you like. THIS AMP MAKES THE BIG $ AUDIOPHILE RIGS SOUND LIKE THEY ARE WORKING HARD TO KEEP UP......FOR PENNIES TO THE DOLLAR. when you are convinced,then spend some money on good tubes and find the amp's outer limits...your in for a treat.
Well OK. I've spent innumerable hours listening to high-end gear in audio shops so I know something about how expensive stuff sounds. And I've spent even more hours listening to my modest system. I thought I was doing pretty good, considering I can't afford a top-shelf system.
Then came the EICO, butt-ugly, rusty, and nicotine coated from years on an audio technicians test bench...and blew the doors off my old amp. Even with a full complement of bad tubes it images better, has tighter, more extended bass, and presents a nice level of detail in the mids and highs. Built from a kit around 1961, this amp does many things well and none badly.
Then I discovered the difference a good pair of output drivers can make. Yep, all the other tubes in this amp measure BAD, but when I popped a pair of Sylvania VT-231s in there, the bass snapped in tight, the mids and highs became sweet, smooth, and very nuanced. The soundstage expanded not only side-to-side but front-to-back.
I can't say a bad thing about it except its looks. The $125 for the amp yielded great bang for the buck. Another $80 for the VT-231s and a few bucks for caps and that's it. With this, I can live within my means *and* satisfy those auditory cravings. No more constant urge to haunt high-end audio salons.