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Being it's a long weekend,I've been working on stuff and listening to different tubes in my Eico HF-87 with my I-pad plugged directly in thru my CAL tube DAC streaming JAZZ RADIO .COM. I listened to my XF1s for three hours straight and it was quite enjoyable.Really nice mids and lower highs and reasonably good upper bass.Now, I don't recommend doing this next step but I was very gentle when I did it..I took out each XF1 while it was playing and I put in an EH 6CA7..I had a thick glove on and did one tube at a time and I would let each tube warm up before I pulled the next one so I didn't get a loud pop thru the speakers.The sound was pretty consistent until I put the last EH 6CA7 in and about 30 seconds later,more presence came in as well as the bottom octaves of the percussion section and it just got better as the tubes warmed up..To be fair,my XF1s are two matched pairs and they are not new old stock anymore but, they test very strong.We are talking 90% on both the TT-1 and the 739C. The EHs are new quad I have had in stock for seven years with about 250 hours on them. I cannot say enough about how great these tubes are..This is in two different amps now and if you recall the other was the Scott 272.You want to get these in the higher testing GM,(8300 to 9000) for audio because it makes all the difference in the world.
I'm not going to say these are as good as the Genelex KT77s but I can tell you that they beat the snot out of my XF1s.
I never cared much for the EL34 for overall response but the EH 6CA7s should satisfy even the most adamant vintage Mullard EL34 tubeophile.I'm just amazed at the full bodied sound with definition from top to bottom.This is on the NewForm Research 645 ribbon speakers.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Edits: 09/04/16Follow Ups:
Mike, I'm not sure what vintage Mullard tubes you have... but the tonal difference from what I've heard between the Mullard and any 6CA7 is day-&-night. The 6CA7 gives the amp more of a 6L6GC sound and response, IMHO. Not the warm vocal midrange of a good EL34. 6CA7 = cleaner highs, tighter bass. Midrange a bit scooped out. A more sterile, less harmonic-rich tone. 3D imaging is a better with the 6CA7, IMO.
As 6CA7 go, the EH is a fine tube. I personally like the GE 6CA7. And still have quite a stash, thanks to UncleStu (RIP)... these are what I've been putting into Marshall head units. But, I have to warn ppl that they change the tone over Mullard or Tesla, which were in the amps. Tone knob tweaking usually helps. Or sometimes, I'll change coupling caps in the tone stack.
The EH last. They are as tough as the old US made tubes. Even in combo amps, which are being beaten to death by would-be axe heroes.
8^)
Steve
I have every Mullard EL34 made from XF1s to XF2s,both single and dual getter,I have Amperex square DD getter and the metal based Philips.
Maybe this quad of EHs I have are exceptional because I did not get this sound with my first quad of EHs which tested in the low 7000 range.
When you did your test,were you doing it in a guitar amp or a hifi amp? That changes the perspective entirely. These particular EHs have a very warm and full bodied midrange and I didn't have this with my other EH 6CA7s.
This is why I say the test results may be key in this case..
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
it happened to me too with a quad of 6ca7 eh factory tested :
gm> 8500
lp> 63
The price was the same ,the quality astounding.
I think could happen with other lucky selected quad by other brands
(i had a rft el34 tfk marked that sounded ....just perfect!
on the contrary i have a Ge 6ca7 quad measured on Sophia equipment
which lasted 3 months and blew my fuse away....there is an "alea "
with tubes i found mirrors aspects of life...it is important
to have skills ,but luck or fate has great impact on what is going on)
I have never heard these tubes described as warm, or full-bodied midrange. In either guitar or hi-fi amps. At least ones designed to take the EL34 as OEM. You didn't change any coupling caps or idle settings in the gain stages? Idle bias dissipation the usual 6CA7 range?
What vintage are those EH 6CA7 tubes? Be nice to pick up a few sets of them.
Steve
I did do the typical McShane rebuild with all the upgrades of the common point ground,820uf caps in the doubler,Teflon coupling and decoupling caps,
Schotkys in the doubler and added choke. Both tubes ran in the same amp.Maybe Jim can explain more why these higher GM testing EHs sound so good.
Maybe mine are exceptional because I have written about these tubes about five times now. You have known me long enough to know that when I keep posting about the same things,I'm pretty excited about it.This is how I was with the K40ys and the 6P3SE tubes..I only put teflons in this amp because I feel they add some sparkle to the more dull sounding EL34s I have tried which is most of them.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Edits: 09/12/16
I don't have any EH 6CA7 or 6L6GC on hand at the moment. Is there a code to read manufacturing date, like in Svetlana (St Petersburg) tubes?
Thanks!
Yes, there is a four digit date code. The first two numbers are the year, the last two are the month.
The quad of mine are 02 07 gm 8500 Ip 63
That's July of 2002. But don't put a lot of faith in the "matching" numbers. The "factory" or "distributor" match is not so hot. Also realize Ip stands for plate current - yet when adjusting the bias the VAST majority of audio (and many guitar) amps read CATHODE current via a resistor between the tube cathode and ground. When I match tubes I match using CATHODE current since that's how I and most other audio guys measure the bias current in our amps.
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