Sovtek 6CA7 fat bottle 90s era

[Gtr_tech]

Anyone know anything about these?

http://i69.photobucket.com/albums/i4...7/P1120166.jpg

Found a pair in a box I forgot about that look new and have nice strong emission. Shoved 'em in one of my gig rigs yesterday biased to 15w. Played that nite with 'em, they seemed to work fine but there was somethin' a little funny soundin' about 'em. Kinda muddy at times. Were these any good to begin with? I know they shipped one of the Mig amps with these as output tubes back then.

[Chuck H]

I had a pair in a Traynor amp that I bought as a mod platform. I can only give my opinion, but I thought they lacked the compression and that top end bristle I expect from EL34's. Not quite like a 6550, but leaning that way. I did A/B them with other tubes so I know it wasn't a circuit thing. Sorry I don't remember exact biasing or output measurements. If you have an EL34 amp that needs less bottom end compression (as in more and clearer bass) and is a tad too harsh, these might be a good choice.?. But hardly what most players expect from EL34's

[Gtr_tech]

Well they are a beam tube, not a "real" pentode. I wouldn't expect them to sound like a Mullard EL34. I was basically lookin' for any info as far as reliability problems and the like. They weren't around very long so I figger'd there must be a reason for that.

Either way, they're commin' out of the amp. the pwr xfmr runs too warm for my taste now (filament voltage is 6.4vac), so I have some Sylvania and GE 6L6s to weed thru and find a strong pair that matches within reason.

[Chuck H]

If you like the level of power tube clipping now, try to adjust the drive voltage as the circuit allows. 6L6's will need more drive voltage to reach the same level of clipping as EL34's in the same amp.

[g1]

Sorry I can't tell from the picture, are they different from the current EH branded 6CA7's?

[km6xz]

My experience, limited, with 6ca7's were all GE's but Sylvania made the majority of them and were the original developer. They were listed as the drop in replacement for EL34 by RETMA but they are not the same tube. The ones available now, EH, apparently are the same tube they sell as a EL34 so don't compare 6CA7s from the day with the modern one.
They were like a beefy 6L6, big bottle, higher anode potential of 800volts so were used in some industrial applications and hi-fi. Musicman used them in their amps. They do not have the same specs and should not sound the same as a EL34. It it probably a better hi-fi tube than the EL34 but it came late to the party. It only came out in 1970 so the industry was already well in its decline so few tubes were designed after that time. They are more rugged than current EL34s, and were intended to compete with EL34 coming from Europe in production Hi-Fi gear and with 6L6 which was a RCA design and major income producer through manufacture and licensing. Sylvania was trying to get a new tube that could be licensed and generate income they really needed, if they could get some major manufacturers to adopt that tube for products. It did not save Sylvania which was absorbed by Phillips. Later versions had the Phillips brand on them but were probably made in the US. I do not remember if Phillips ever made any in their plants.
I used them in a power amp back then that I made for 4, 2 per channel and really liked them but I was using them for Hi-Fi so am not an expert on overdriving them. If I had a good pair I would run them, no one disliked them. Originals will probably last longer than any new tube. They were rated at 25 w dissipation but that was marketing numbers so people would swap them into 6L6 devices. They were closer to KT-88 than 6L6 however.