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I have a Jolida Fushion 3502P power amp. It can use either EL34's or KT6550's. I wanted to try the 6550's but only have three (one went bad) I used with my old Rogue 88. The manual says that I can use KT88's and have a matched quad set of Golden Lions but the amp doesn't seem to like them. It shuts down after a while of playing and the bias seems to drift.My question is if I want to try some 6550's should I just buy one and use it with the other remaining three I have or should I get a whole new quad set. I have no idea what life the 6550's have left. They may have a lot or maybe not. The Golden Lion KT88's are fairly new I know. I have a bunch of Electro-Harmonix KT88's that I don't have any way of matching them for the best quad set.
The three 6550's I have left are Electro Harmonix 6550's.
Appreciate any suggestions.
Edits: 01/09/21Follow Ups:
Does the amp 'require' matched tubes? If so, you've answered, mostly, your own question.
How much heater current will the transformer supply?
Too much is never enough
The 3502P has a switch on the back to select between EL34 type tubes and 6550 type tubes.
You switched before you replaced the tubes, right?
Deep down the rabbit hole
I have the older(-est?) version of this Jolida that was rebuilt with beefier power supply and higher quality parts, had it now almost 10 years.
Most reliable tubes for this amp in my experience was the Svetlana EL34(came with amp) and the EH KT88. I tried the GL KT88, sounded very good but had one tube fail within 2months, purchased from The Tube Depot, factory matched. Got a replacement but another of the original quad failed a few months later, too long after to get another replacement, so gave up on GL88. Tried a variety of others, Tung-Sol 6550, JJ KT77, GL KT77, EH 6CA7, JJ EL34L.
THE GL and JJ 77 sounded very good, but also had failures, so I just stick with the EH KT88 and Svetlana 34 which has been rock solid over the years.
With individual bias pots for each tube you can swap in a replacement tube with no problem. THe main issue is getting reliable tubes, tested and burn in, 'factory matching' is a crapshoot.
Thanks for chiming in. Right now, the Jolida comes with Tung-Sol EL34's. As I said in the OP there's been no problem with them.I now put in a mixed set of EL KT88's. I only had three each left from two different sets of quads. So I use two from each set. I biased them and haven't had a problem since.
I don't know if I have a bad GL Kt88 or more but the amp does not seem to like them and I have no way of checking them. It's not like one is burning cherry red or not at all. So, I guess this set of GL's are out.
I did mention to J Mcshane that when I initially put the GL Kt 88's in and biased them it wasn't until after a couple of days of listening that I realized I didn't change the switch on the back panel from EL34 to 6550. So, I shut it down and moved it to the proper position and then biased again. I may have damaged one, more or all the tubes with that oversight. I just don't know because as I said, I have no way of checking the tubes.
Are there some dealers who will let you send them in for checking if you pay a fee plus shipping both ways?
Edits: 02/03/21
"...Are there some dealers who will let you send them in for checking if you pay a fee plus shipping both ways?..."
They probably will just want you to buy new tubes. Not worth the effort for them to check someone's used tubes.
Thanks, I'm not surprised. I was leaning in that direction anyway.
I'd be more concerned about the amp shutting down.
GL KT88's are fine tubes.
KP
Yes, I have a voltmeter and biased the tubes using that. The amp also has an EZ bias feature where you don't need a meter. I've used both and decided the meter was a little more accurate.
I haven't had the same problem with the EL34 tubes only when I tried the Golden Lion Kt88's. Are Kt88's and 6550's always interchangeable? The amp goes into a standby mode after playing it for an hour or so with the GL's. If I check the bias, it's usually lower than originally set for those tubes.
Your amp will be fine with both KT88's or 6550's. However (and your mileage may vary), that Gold Lion KT88 is the most unreliable version of that tube I have ever used. You probably have at least one bad one in the group and possibly more.
Dan Santoni
as both McIntosh and VTL use Gold Lion KT-88s in production. It doesn't make sense they would choose unreliable tubes.
There is, however, a difference between buying tubes from any random source and purchasing those that has been thoroughly tested and matched in advance. Many are rejected by manufacturers in their supply chain.
I bought the Golden Lion's from an on-line source I found on Ebay I think. Vacuum Tubes Value. They claim to thoroughly test their tubes. Does that mean they actually do? IDK. As I said, I used those tubes in an old Rogue Model 88 before for not very long. So, they didn't have a lot of use on them.
I would choose.
Point taken.
Let me ask this though. If you are buying a tube or tubes with a good rep such as the Genalex GL KT88's and they are supposedly tested, what difference does it make who you buy them from?
What is a more 'reputable' source selling the same tubes going to do that another not-so-known or reputable dealer isn't?
If you are buying a tube or tubes with a good rep such as the Genalex GL KT88's and they are supposedly tested, what difference does it make who you buy them from?
*Tested* how? For how long? Under static or conditions using live voltages?
I see. What dealers in tubes do you recommend that test their tubes so stringently?
I mean the ones you know for sure and not just say they do.
Edits: 01/12/21
As previously mentioned, I prefer those who burn them in for an extended period using live voltages. Manufacturers like Audio Research and VTL do.
Dealers Jim McShane and Keven Deal likewise do the same.
Thanks E-Stat. I have some NOS Mullard 12Ax7 I bought from Upscale Audio years ago but really didn't pay any attention to how they were tested or burned in. I would rather pay more $ for a thoroughly tested tube that may result in more longevity.
Good question. I see if I can find out.
This is what it says on the web site:
We sell factory matched tubes, matched on proprietary factory test equipment. Test results are typically labeled on each tube box. Insist on factory matched tubes, not tubes matched on generic testing equipment.
Just so you know - the "factory" matching is really not very good.
Thanks Jim,
I believe I bought a quad set of EH KT88's from you in the not so distant past. One went bad and I have another set I got from somewhere else and one of those went bad. So I have two sets of three EH KT88's. So, I now have 6 EH Kt88's and 3 EH 6550's not to mention the quad set of Genalex GL KT88's that my amp doesn't seem to care for unless one or more of those is bad which I have no way of knowing.
Now I need to buy another quad set? I'm running out of storage space.
Hey, tubes go. If the factory checked them AND your vendor checked them - I would start looking at your amp.
Dude, you gotta stop buying tubes of ebay.
One quad set came from rogue audio. One from Jim McShane and the golden lions came from the guy that advertises on ebay.
I wonder how many GL kt88's the reputable dealers have to throw out due to bad measurements?
The GL KT-88s are my most reliable power tube - I reject well under 1% of them. However, the factory matching is terrible, just so you know...
Check out my FAQ for some helpful info:
Jim, I was reading the post you wrote about 'Tube Problems That May Not Be Tube Problems'.
The section about making sure the bias is adjusted well below the current value for that tube when replacing them with newer tubes got my attention. I replaced a set of EL34's with the Genalex GL KT88's. There's a switch on the back of the amp that you must move from the EL34 position to the 6550 position. Alas, I failed to do this when I first installed the Golden Lion Kt88's and biased them. I realized what I did and moved the switch to the correct position and rebiased the tubes but maybe the damage was already done? They are not noisy but do cause my amp to go into the standby mode after an hour or two of playing at loud but not ear splitting levels. It doesn't do this with the EL34's or the mix of Elecro Harmonix Kt88's I now have currently installed. So, I'm not sure the amp is at fault. Is it possible that I damaged one or more of the Golden Lion Kt88's? In what way would they be damaged to cause the amp to go into standby when they play noiselessly?
Edits: 01/22/21
They are getting a lot of power out of two 6550s. They must be driving them pretty hard. My Prima Luna makes less than half that power with the same tube compliments.
A note of tubes: Places like Upscale Audio spec the tubes they purchase at higher values than what the factory accepts as a good tube. Then they burn-in and match to eliminate any lessor product. They send the rejected tubes back to the factory and they are sold to somebody else.
Correction: They spec their tubes tighter than the factory but the factory does not allow returns of working tubes.
Thanks again Russ. Good info to have for my next tube purchase.
Yeah, I heard/read similar things about the Golden Lions. They were fine in my old Rogue but coincidentally the Rogue Model 88 died with the GL KT88's in it.
As I said before, I have 3 EH6550's and 6 EH KT88's but have no way of checking the specs or matching them.
Would it hurt to randomly try 4 of the Electo Harmonix KT88's in there to see how it reacts? Of course, I will bias them.
I had 2 quads that ran for years in my Rogue M180's.
replaced them with another 2 quads just because they were running long the in tooth.
Also ran that set for years, although not as much as first set.
Not one issue.
The last set was purchased in 2010, so maybe new prod has issues?
KP
Not ware of any amp that can't take both KT88's and 6550's.
Jolida lists both for this amp, as you mentioned.
So.. you may have bad KT88 as well.
Or something in the amp that is killing tubes? Fun, no?
If you can bias each tube individually, you can just get a single 6550.
Unless this is a used up set, then I'd just get a new set and leave this trio for backups.
The bets tube advice I have received here has been: clean the pins and sockets. Amazing how many issues this can fix. Just passed this on by my ex-bro-in-law a month ago when one of his guitar tubes was making a racket.
Not sure it will help, but can't hurt.
KP
I think I will try a set of the EH KT88's in the Jolida and see if it behaves like it did with the Golden Lions.
I'm good about cleaning pins and sockets and I don't use any contact enhancers on my tubes.
KP
No. Nothing obvious.
Do you have access to a tube tester? Has your tube vendor tested these tubes out?
I don't have access to a tube tester but they were supposedly tested. But who knows?
First, I would do a search and see how others liked using that tube in THAT amp. I would buy a new quad set. Who knows what condition the three remaining tubes are in.
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