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Yeah, first thing I'll get told is to use the search, which I did. My question is still unanswered! Let me be more specific...Most tweaks/changes in one's system usually ends up in small improvements or changes in the sound. I am wondering, by switching to EL34 output tubes from 6550's, will the difference be ever-so-slight and barely detectable or will it be a large difference in sound? I guess I am not looking for a 'better' sound, since I am very happy right now. But experimentation is always interesting and I'd love to try some EL34's, to hear the difference -- I might like it in my system.
I understand what EL34's sound like in comparison to the 6550's from reading and listening myself, but does the design of the circuit really play that huge of a difference?
These are for an older model JoLida 502A -- which can accept EL34's with a bias adjustment, according to JoLida themselves.
Thanks!
Follow Ups:
Here's a link to Mr. Spafford's discourse on the benefit of proper bias on EL34s to handle the bias debate. (see link below)The sonics you will achieve will depend to a great extend upon WHICH brand(s) you choose to try in your Jolida. What brand 6550 are you using now? I have a Jolida 302a (same circuit, chassis, etc. just a different set of resistors). In my amp, I get a HUGE change just going from Svetlanas to EH (EL34), and therefore I prefer one brand over the other in a big way. I would expect you to have similar results.
Since you state that you're familiar with the difference of EL34 vs. 6550, then what are you looking for with regard to an answer? I'm not challenging you here; you obviously know what you're doing already. Just wondering anyhow.
I guess, I am trying to find out if the sonic difference between the Svetlana 6550's I am running now versus an EL34 type tube will be an actual, easily noticable difference versus a perceived or non-existant difference, or a difference that is so, so slight, that it might not be revealed by my equipment.i.e. is the amount of CHANGE in the sound worth the expense of the tubes?
We'll find out soon enough, I ordered a matched quad of EL34's today. They should be in tomorrow. :)
I hope that you like the Svet EL34s. Those are all that I use (until they become unavailable or a better something comes along that is still affordable) since I can't afford/justify the wonderful NOS tubes out there. The difference between the two should be in the mids I would surmise. You should have more lush mids from one to the other, maybe giving up just a touch in the bass.
I imagine that you will easily be able to perceive the difference between the two. What you like, however, will be the most interesting part of the experiment.
I too have considered trying a tube swap, only in my case, it would be the exact opposite of what you're doing here. My amp would require a resistor change to complete the swap, but I understand that it is a simple matter to complete.
Please drop me an email and let me know what you think of the EL34s - this is probably a fairly common contemplation that 502/302 owners consider once they learn of their amps' multitube abilities!
Take care,
SK
Yep, I'll do that. I'll make another post with my feelings on the issue once I get done.The other weirdness is that I think I now have speakers that are being limited by my JoLida. I am not sure what to think just yet about that one. I've upgraded the internal wirings of the 502 already. I have yet to do the caps, that comes next -- along with the volume and balance pots.
I am not sure yet. Anyway, I am looking for a more apparent midrange. Taming the bass of the 6550's might be a good thing. All these misconceptions about tube setups lacking bass is ridiculous... this JoLida puts out prodigious amounts of it. Anything I can do to help out the mids would be fantastic! Not that the amp or speakers are drowning anything out at all, everything is nice and even -- perhaps too analytical in its balance. Anyway... the experiment will be a success or failure. :) Time will tell!
What speakers are you using? I could see imagine that certain "power hungry" speaker brands would be a tough load for the Jolida, but yours has the extra muscle of 10 watts at the outputs (not to mention the extra room-heater watts).
I am using the brand new Polk LSi9 (the ones with the new Vifa ring radiator tweeter, Polk's re-entry into high-end musical speakers). If you're curious, there's a review in April's The Absolute Sound where they are compared to, quite favorably, the Dynaudio Evidence Temptations ($35,000) by Anthony Cordesman. Needless to say, the new LSi's are serious contenders.They are not the most efficient speakers, however. 88db, 4ohm nominal. But 50wpc is plenty even for these, IMO.
Great! Well I would presume that your amp with the 6550s should be able to open up those Polks rather nicely. The EL34s may display earlier strain but if I may say so, I run some Spendor SP1/2s which are also listed as 88db efficiency, and I've found that I can run them fairly loudly without signs of amp distress if that helps.
Do let us all know how it goes and congrats on the new speakers.
-SK
Not too worried about it, really. I don't listen at earth shattering volume levels. The 6550's push the LSi9's at 4-ohm very, very well. The JoLida amps have both 4 and 8 ohm outputs.Like I said in my e-mail to you, I am not sure how safe running the EL34's cool is (one would assume this would be perfectly fine), but I did listen at around 15mv for a few minutes and noticed some pleasing differences in the sound.
JoLida needs to get their ducks in a row when it comes to their people telling folks that the 502A will work with EL34's... apparently Mike Allen is wrong, according to a rep there, and the 502A/502B need a resistor change to properly bias for both 6550's and EL34's. Luckily, it's a very, very simple swap.
R14 and R15 need to be changed from 22k ohm to 13.3k/14k ohm for each channel. After this, I have been told, you will be able to bias for each type of tube.
I would be wary of running the EL34s TOO low - 15mv sounds like it's just barely getting the tube going. Well it's fun to experiment anyway.
You're right about the resistors and in fact I was planning on ordering them to get the job done on my amp!
I'm curious about the 6550s but that is where it ends. Maybe I shouldn't bother - I'm very pleased with my sonics.
Take care,
SK
You can also greatly affect the sound with the brands of EL34, 6550, KT88, and KT90 you use. Most posters like NOS versions of the above (except for the KT90, which is a current Ei production tube). I tend to find the EL34 leaner, higher in clarity and detail, more quick and transparent. The 6550 family sounds fuller, richer, with more bass weight, dynamics, and a bigger soundstage to me. I also like the current production versions of the 6550/KT88/KT90 better.
are EL34's interchangeable with KT88's and 6550's in most tube amps?
steve
It depends upon the design of the amp. 6550's require a little more heater current (1.8 amps versus 1.5 for the EL34), which probably won't present much of a problem for the input transformer, but the 6550 requires more negative bias than the EL34. If your amp has user variable bias, it can probably be set to accommodate the 6550, but if it is fixed bias, you may have to change the bias resistors. You should check with the amp manufacturer. My AES DJH version Superamp has variable bias, so I am able to run 6550, KT88, KT90, EL34, KT77, 6CA7, 8417, 6L6 variants. If someone has other experiences please correct me.
You state that you like the current production 6550/KT88/KT90 better. Which brands in particular and which NOS tubes have you compared them to? I have a set of Rogue M-120 Magnums with the Electro Harmonix 6550s right now, but was considering the Tung Sol 6550s.
Actually Tung-Sol 6550's, of which I have the black plate version, are NOS, and yes, they are better than current production versions. They are also much more expensive. I have tried the following current production tubes:Ei KT90
Svetlana 6550
Svetlana KT88
JJ Electronics KT88
Svetlana EL34
JJ Electronics EL34
because in most circuits they will prove superior. I have tried the Russian 6550 and KT88, and the E. European ones, and they do not sound as good as the above mentioned heralded tubes.
Yes, there is a difference between the types. Circuit design and execution is of course a big part of this, but there is still a difference. I prefer the EL34 type, in my gear the current production KT88 and 6550 are much less satisfying, even the famed T-S 6550 is less appealing than a lowly new production EL34. My preference, and I am not alone in this, is the JJ E34L (note the specific designation). They are very nice, and at the price are true audio bargains. Mine have proven to be durable and satisfying.
Hi,
I think you could get quite a difference in sound just by setting the bias to another value on your current tubes... (take care on plate dissapation)
You might like it as well...mvh /Pär
I didn't particularly notice any difference when adjusting the bias between 40-60mv (recommended is 50 for the 6550)... maybe I should listen harder?
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