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Eico ST-70 vs Fisher KX-200

AA6U said:
I remember I worked on a Scott 299C for a customer and I was very impressed with it. The KX-200 seems to be just as good. Of course an A/B comparison is the best way to go, but, unfortunately, I don't have the Scott anymore to do that.
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I have both, to my ears the Scott has a tad better detailed high end, I'm told it's because of the 12AX7's in the KX 200 give it the miller effect or something like that. I prefer the KX-200 though mostly because the built in bias adjustment and meter.
 
I bought an LK 72 but it never made it to me.
Pretty sure I sold it to Larry ( he was PEing it to me and I changed direction) :dunno:
 
Because of previous experience, I don't trust built-in meters, so I use a voltmeter to set bias and balance (cathode to ground dc voltage measurement for bias, and cathode to cathode voltage measurement for balance). Very easy and very accurate.
 
Eico ST70. I purchased one from Allied Radio and built it in my senior hi school year. I had good soldering skills and attention to detail... one couldn't tell if it had been a kit or not. Adjusted bias with my Weston vom, it worked with out a problem. Bought a Lab 80 MK II from a department store and plugged in into the amp and played it through my new Utah Heritage floor standing Allied Radio purchased floor standing speakers. Just reflecting on a memory... it sounded very good to me, Doors Break on Through sounded great. The amp was quiet on the rather efficient Utah's but then it was my first time experience with anything one could call hi fi stereo.... before that it was a Philco rather compact phono only console dated 1961 and a Webcor two direction mono tape recorder dated 1959. I sold the Eico at a garage sale for fifteen dollars years ago... wish I still had it for personal reasons.
 
AA6U said:
Because of previous experience, I don't trust built-in meters, so I use a voltmeter to set bias and balance (cathode to ground dc voltage measurement for bias, and cathode to cathode voltage measurement for balance). Very easy and very accurate.
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I verify the meter before relying on it, and the KX-200 requires a resistor value change to make it spot on.
 
Sometimes the meter movement itself changes value over time, so it can be tedious to make sure it's right even if you change an external resistor. I once worked hard to get the meter on a Citation II working correctly and was ultimately successful using a resistor decade box and a voltmeter to determine the proper resistor value. Nevertheless, I still find a voltmeter to be the most accurate. It's also critical to be sure the cathode resistors are accurate.
 
AA6U said:
Sometimes the meter movement itself changes value over time, so it can be tedious to make sure it's right even if you change an external resistor. I once worked hard to get the meter on a Citation II working correctly and was ultimately successful using a resistor decade box and a voltmeter to determine the proper resistor value. Nevertheless, I still find a voltmeter to be the most accurate. It's also critical to be sure the cathode resistors are accurate.
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Yep, I follow Dave Gillespie's advice and direction whenever possible, resulting in some great performing equipment and no tube failures.
 
I have to say that I really like this amp. We'll see how well the Eico sounds when I get to it.
 
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AA6U said:
Cool factor is not an important issue. Eico has always been an ugly duckling among audio equipment. I am looking for great sound. I am just finishing up rebuilding the KX-200 and then I'll get to the Eico and see which sounds better. Another alternative is to dump them both because they use 7591s which are surprisingly expensive (even the Russian 7591s cost more compared to EL34s, etc.) and get a different classic amp with different output tubes. I'm making suggested mods to the KX-200 so that it doesn't burn out tubes as fast as it's reputation suggests.
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As for the 7591 issue, I'm using a new matched quad of Tung-Sol's in my Sherwood S-5000II, and I really like them. This may be one of my favorite vintage tube integrated amps. Unlike other reproduction 7591's, the TS's are the correct size. At a bit over $100 for them, I felt the price was acceptable and not a lot more than comparable EL34's.
 
I bought a quad of new Tung-Sol EL34s for my Marantz 8B and did an A/B comparison test with Mullards in one channel and the Tung-Sols in the other. I could not tell the difference. I agree that the new Tung-Sols are great tubes. I may opt to try Tung-Sol 7591s in my KX-200 to replace the menagerie in there now, although it sounds great as is.
 
AA6U said:
Totally agree. When I buy new ones, I buy from Jim McShane at http://www.mcshanedesign.net/tubes.htm

He's so honest that he won't sell tube brands that don't meet his high standards even if you want them.
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If the amp I'm working on needs 7591's and has adjustable bias, I have had great success with the so called matched quads from the auction site. But if it has no adjustments we really have no other choice than Jim for matched quads. I really like the new TS 7591's for sound and longevity. They do need quite a break in and tedious adjustment for around 3 hours before they settle in and stay stable.
 
AA6U said:
Good to know. Which seller on the auction site have you had good luck with?
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wpc1896 is the vendor (no affiliation). As an example, when I installed a set in a Fisher 500-C I had to add a 10K trimmer pot in place of the regular bias resistor in order to get the negative bias voltage up since the TS 7591's run hot. After getting the so called matched quad dialed in, they varied between .37V to .33V which is decent but not what I'd call a well matched quad. If you have individual bias adjustment, then these are fine.
 
RS Steve said:
wpc1896 is the vendor (no affiliation). As an example, when I installed a set in a Fisher 500-C I had to add a 10K trimmer pot in place of the regular bias resistor in order to get the negative bias voltage up since the TS 7591's run hot. After getting the so called matched quad dialed in, they varied between .37V to .33V which is decent but not what I'd call a well matched quad. If you have individual bias adjustment, then these are fine.
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That's the seller I've had good luck with. Most recently, I bought a matched quad of Sovtek EL84's for what I thought was a really low price. I popped them into my Pioneer ER-420, and they sounded much better than the tested-good originals.
 
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