Splunders
Well-Known Member
Hadn't considered that possibility!
Totally Tubular: The Tube Thread
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Splunders
Well-Known Member
I think you jinxed me @HiFi Guy! 
I just turned on my pre and power amps to warm up a few mins before streaming some stuff. I walked a short distance away, and about a min or so later I hear pop, thump, zzzzp, pop and whip my head around and see a couple flashes from my power amp's power tubes (KT88s) before it all stops. I let it sit there while still on and nothing more happens. All tubes were still glowing as usual, no noises, etc and then turned it off after a couple more minutes. WTF?? Is everything ok to use still but one of my tubes is dying? Amp screwed??
I just turned on my pre and power amps to warm up a few mins before streaming some stuff. I walked a short distance away, and about a min or so later I hear pop, thump, zzzzp, pop and whip my head around and see a couple flashes from my power amp's power tubes (KT88s) before it all stops. I let it sit there while still on and nothing more happens. All tubes were still glowing as usual, no noises, etc and then turned it off after a couple more minutes. WTF?? Is everything ok to use still but one of my tubes is dying? Amp screwed??
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I think you jinxed me @HiFi Guy!
Not screwed. KT88s sound great but are a bit fragile. Mike Allen, the founder if JoLida told me years ago that usually if KT88 fails, it’s early on. That sounds like what’s happened here.
You have likely blown the plate fuse on the adaptive auto bias board. Check your manual. It’s an easy fix. A fuse and fresh tubes and you are golden.
Splunders
Well-Known Member
Ok, I can handle that. Do I have to chuck all the tubes out? Is there a way to know which one was faulty and keep the other 3 for backups?
I would have thought I was past the early on stage with this amp - guessing 300 hrs by now. Good thing I have a back up amp. I guess I have a date with Upscale Audio's website tonight!
Thank you very much for the quick and super helpful advice as usual @HiFi Guy !!!
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Whichever tube you saw “flash” is toast.
If you are going to stay with KT88s, I highly recommend Gold Lions.
Another option would be 6550s- to me they don’t sound quite as good as KT88s (eventhough they are very similar.) They are, however, very durable.
Splunders
Well-Known Member
Was just about to ask, but you beat me to it. Was thinking Gold Lions as well. I'd been wondering about their KT-77/EL34s too - any experience with those? I'm more interested in soundstage than with added "warmth", which seem like possible tradeoffs. Ive been very impressed with the bass Ive gotten from the KT88s, but if I lost some oomph in that dept, it would be ok.
You’ll get more midrange beauty with the EL34, and the expense of some very deep bass. Bass is a bit looser with the EL34 as well. Some prefer the EL34. Not me. But there is no right or wrong answer here. EL34 are generally very durable as well.
Splunders
Well-Known Member
I decided to go with the Gold Lion KT-77/EL34s. I had lived with the KT88s and wanted to see how green the grass was on the other side. I have to say I agree with @HiFi Guy on the preference of KT88s. I've had the KT-77s for a few weeks and while they do add some mid range warmth, it isnt as much as the bass tautness and depth they lose compared to the KT88s. The KT88s have no need to feel ashamed when it comes to midrange capabilities either. If all I listened to was acoustic or jazz, then maybe, but for an across the musical spectrum tube, KT88s are for me.
The good news is if you liked the stock KT88s, you’ll love the GLs.
Check out Tonal Tubes on Reverb. Great prices, fast shipping and a 60 day guarantee in case you have a tube fail prematurely.
OnTheRoad
Active Member
Woo, a new thread to join.
I'm about to head up to my tech to receive my newly-restored Fisher 400 receiver. Couldn't be more excited about my first foray into the world of tubes.
I had hoped to stick with NOS vintage tubes, but damn are the 7868 output tubes expensive (pushing $200 for questionably matched pairs from eBay, even more from reputable sellers).
My new production, Electro Harmonix 7868s just arrived in the mail so I'll make my way to my tech's place to install them this week. Here's a couple before pics for you all to start with.
I'm about to head up to my tech to receive my newly-restored Fisher 400 receiver. Couldn't be more excited about my first foray into the world of tubes.
I had hoped to stick with NOS vintage tubes, but damn are the 7868 output tubes expensive (pushing $200 for questionably matched pairs from eBay, even more from reputable sellers).
My new production, Electro Harmonix 7868s just arrived in the mail so I'll make my way to my tech's place to install them this week. Here's a couple before pics for you all to start with.
displayname
Well-Known Member
That front face plate looks great!
OnTheRoad
Active Member
Thanks @displayname - I've also acquired a reproduction wood cabinet for it, so it should be set as a centerpiece in the system for awhile.
Will update you all this weekend with the final product (hopefully) as time allows for me to get to my tech.
The 9 12ax7's will eventually need replacement, along with some tuner tubes I'll do at the same time, but I'm holding off because all but one tube is original Fisher branded and higher quality than my wallet will currently allow me to go.
I'll probably start with the phono and phase inverter tubes, then progress through the rest.
Will update you all this weekend with the final product (hopefully) as time allows for me to get to my tech.
The 9 12ax7's will eventually need replacement, along with some tuner tubes I'll do at the same time, but I'm holding off because all but one tube is original Fisher branded and higher quality than my wallet will currently allow me to go.
I'll probably start with the phono and phase inverter tubes, then progress through the rest.
vinyldoneright
New Member
My Budgie with Phillips (Amperex made) 7308's
@HuddieLedbetter got some killer new gear today. We need pictures!
I kept waiting for the update. If you still need 12AX7s, try the Sovtek 12AX7LPS. It’s inexpensive, durable, and sounds great.
OnTheRoad
Active Member
Wow @HiFi Guy - my apologies! Quaran-time really got away from me on this one due to what I’m about to share. TL;DR: I have yet to actually fire up the Fisher in my home.
I have some how broken the getter on 6 tubes upon trying to get the pin sockets to expand. If I’m being honest, tubes have made me feel cursed for the first time in my vintage audio journey.
I’ve gotten advice, and followed said advice, from audiokarma and I’m still faced with the reality that I’m 6 tubes down the drain with another quad (subsidized mostly by some record sales) on the way.
I have some how broken the getter on 6 tubes upon trying to get the pin sockets to expand. If I’m being honest, tubes have made me feel cursed for the first time in my vintage audio journey.
I’ve gotten advice, and followed said advice, from audiokarma and I’m still faced with the reality that I’m 6 tubes down the drain with another quad (subsidized mostly by some record sales) on the way.
deathbyart
New Member
Did you notice a difference from stock tubes? I currently have Gold Lion but would love to try others.
What do you want to spend because a tube amp that’s worth having is into 4 figures, they don’t come cheap.
nevermind then