About my KT88 Tubes

I am fairly new to analog,tube audio equipment so I thought I'd use this thread to gain some insight on a tube situation that I am experiencing.
My Cary 120S amp uses 8, KT88 power tubes and came with 8 matched Electro Harmonix tubes. Recently, I started loosing tubes from both sides. I would replace them and rebias everything and everything sounded good. I started thinking probably these tubes were getting near the end of there useful life so I chose to replace them all with 2 matched quads of "Gold Lions" which I have heard, were superior. Upon installing them, I am noticing that my top end is very shrill almost to a tinny sound. Do these tubes have a break in period? Does anyone else have experience with these tubes?
I'd suggest contacting Kevin at Upscale Audio. He is any expert on tube recommedations and sale thereof for Cary tube based components.
I am no expert either but I replaced my Winged "C" 6550 tubes with Gold Lion KT88's. At first I was not impressed. With my amps it took a week of heavy use for them to come around but when they did I was hooked. My feeling is yours will smooth out real nice so give it a little time.

good luck
Well I've not used any "Gold Lions" or EH's for that matter. I usually use SED 6550's or KT88's, but that is not why I'm posting.

I have a different Cary amp and did quite a bit of research into Cary amps in general, but mainly as to tube selection and biasing, especially since I'd noticed with some Cary amps that owners were complaining about early power tube failure. Including myself. Initially I lost a 6550 in a set biased at Cary's recommended setting. It was the only SED power tube I'd ever lost thru sudden failure.

It seems there is some consensus that Cary's spec's are optimized by maximizing power tube output, thus creating sudden pre-mature failure, and the settings had little to do with maximizing tonal qualities. In fact I found in a discussion Dennis Had commenting on his preferred bias setting on some of his amps and they were markedly different that were recommended in the manuals and produced sound with his preferred tone.

As a result, I dropped the bias setting on my 6550's from 50ma per tube to 45ma per tube and have had zero problems since. Could it be a coincidence? Sure. But I think not.

There are a lot of folks who have posted very favorably about the Gold Lions, which I've never heard. But from comments from folks I trust I've concluded that they sound far more like 6550's or even KT90's than typical KT88's (some of which tend to have a warmer tone).

If I were you I'd lower the bias setting on the tubes, as I have, and give them a good 100 hours to break in. The highs might just be less shrill and the bass develope appropriately. You won't damage anything by doing so, and you might be pleasantly surprised. If the tubes are still 'shrill' look for a brand which has a reputation for more 'warmth.


I put these tubes in my Mc275 about 6 months ago and noticed that after about 30-40 hours they became sonically warmer, but not overly so, and with more dynamic impact while keeping their transparency and detail.
Yes I have an octet of the Gold Lion KT-88 reissues. I am only have experienced the typical break in nothing extra, actually somewhat less.
However the minute I put them in I found them to be excellent. There was and still is more tonal balance with a forward midrange than my previous experience with KT-88s.
I did get the selected by a dealer who is very careful and I think burns them in for 24 hours prior to testing to make up an order. The entire octet is matched. The same fundamental sonics were present when I put them in another amp I bought. I think selection of power tubes in general is important and may be the reason for any discrepancy if the topology isn't one that produces a shrill sound. If the tube was thin in any amp it would have been demnstrated by the second amp, a Jadis DA-60.
You should baer in mind that a well run down set of tubes will frequently become mellow or even just degraded in some areas such as treble. You may not have had a very different experience if you replaced the whole octet at once with the EH's.
BTW factory matching and hand selection by a very experienced dealer are two very different things.
I can whole heartedly recommend Jim McShane over on Audio Asylum. He is very careful and rejects a number of tubes from every batch he carries as unacceptable. It appears he is genuinely commited to selling only good tubes and won't carry any given tube otherwise.
The price for new production is only slightly higher than other sources, but not all that much. He doesn't have an optiional no testing price. He sells the "gamut" from NOS to current. He periodically checks the quality of tubes being issued from manufacturers that he has discontinued due to problems with reliabilty.
With NOS/OS tubes he sells tubes which he thinks are sonically superior and a reasonable value. He frequently eats the cost of a bad bunch of NOS/OS tubes even for microphonics.
I was somewhat skeptical of the over the top, slavish loyal following he has cultivated. I am now fairly certain the praise his customers have given him are earnest.
As an inveterate tube roller I like to discover whether a tube has my kind of sound so i wasn't thrilled with the prospect of being told in a sense what is good and what isn't. However with the current cost of OS tubes at insanely high levels, it may make more sense for you to go with him or other truly good principled seller. I can no longer afford "AS iS" sales. The people I now try to buy from stand behind the tubes they sell.
I have no conflict of interest to reveal and I am ,so far, just a happy customer .
I am no expert either but I replaced my Winged "C" 6550 tubes with Gold Lion KT88's. At first I was not impressed. With my amps it took a week of heavy use for them to come around but when they did I was hooked. My feeling is yours will smooth out real nice so give it a little time.

good luck
I have a 120s and installed a new set of EH kt88's and keep them biased at 150 without any problems about 6mos now..
If you are going to get involved with a complete tube based system I would also suggest you invest in a good used tube tester to take alot of the guesswork out.There are plenty on ebay..I picked up a Eico 635 in great shape and it serves my purpose for basic testing.
I have been using JJ KT88's and they are very good, reliable, and sound great. Be sure your meter is accurate and bias accordingly. Jallen