KT88 advice

CBP

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I currently have Gold Lion KT88s in my Beard 101 power amp, its lost a bit of low down punch and Im assuming this is because the KT88s are starting to fade after a couple of years of use. (all input valves are recent NOS Philips, so no issue there).

I want to replace the KT88s (all 8 of them!) so would welcome advice. Should I buy new Gold Lions or try Psvanes. I can get 8 new basic Psvanes for about £600 on amazon, with the fancy grey ones costing about a grand - and I suspect the only difference is the grey paint!.

Are there any other brands recommended? Do different brands sound much different?

Can't really justify spending more than 1K on the 8 in total.

All advice and experience welcome.

Cheers,

Chris.
 

rabski

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I don't know any of the modern production KT88, but if (a pure guess) the Psvane follows the same sort of path as they do with their other valves, then the TII types, which are part grey glass and have an anodized gold base, are a step up. Hot Rox has them at £418 for a matched quad. Not peanutes, but not insane money.

The last 'new' KT88s I bought were Gold Lions though, and they were perfectly decent. If you've been happy with the sound, maybe stick with them. £800 is a lot to throw at something that may be better, but may not.
 

macvisual

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Only my tuppence worth input;

I’m not a valve guru by any means, or do I have vast experience regarding valves - around twenty years ago I changed the EL84 valves in my Audio Innovation S1000 MkIII mono-blocks to the American made ‘Groove Tube’ valves for a tad more dynamic punch/kick……they gave excellent results.


Cheers.
Peter
 

bencat

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Just looked and Amazon have the Psvane KT88 for £292 for four which seems to be as sensible a price as can be expected . As Richard says do you really want to spend lots more on the hope they will be better ?
 

pmcuk

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I currently have Gold Lion KT88s in my Beard 101 power amp, its lost a bit of low down punch and Im assuming this is because the KT88s are starting to fade after a couple of years of use.
Have them tested! They may be OK, and that would save you money.
 
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toprepairman

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The 'American made' Groove tube EL84's are in fact Russian made.
Have a couple of amps in for repair, a Quad II80 with KR Audio KT88's one of which just went open circuit intermittantly, no other damage, just raised level of hum on output.
The other an Air Tight ATM2. It had Russian Gold Lion KT88's, one of which failed spectacularly and caused other damage, not least blowing the bias meter to bits, really don't know how I'm supposed to replace that. In its' defence the amp does stress the poor old valve beyond what it should tolerate.
 

rabski

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To add to Henry's post, AFAIK, every 'guitar amp' variant of KT88s is rebranded, but then so are a great many others. There are currently very few factories worldwide actually manufacturing valves, and apart from one or two highly specialised and very small volume companies, they are all in Eastern bloc countries or in China.

Overall, KT series valves (especially 88s) seem more prone than others to failure. It's easy to blame poor manufacture, but in a lot of cases, once again Henry has hit the nail on the head. Far too many designs seem to assume that KT88s are as bullet proof as the original GEC variants, so they push the plate voltage and current close to (or even above) the stated maxiumum. Most modern production valves don't take kindly to being run at their maximum ratings.
 

TECUMSEH VALLEY

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To add to Henry's post, AFAIK, every 'guitar amp' variant of KT88s is rebranded, but then so are a great many others. There are currently very few factories worldwide actually manufacturing valves, and apart from one or two highly specialised and very small volume companies, they are all in Eastern bloc countries or in China.

Overall, KT series valves (especially 88s) seem more prone than others to failure. It's easy to blame poor manufacture, but in a lot of cases, once again Henry has hit the nail on the head. Far too many designs seem to assume that KT88s are as bullet proof as the original GEC variants, so they push the plate voltage and current close to (or even above) the stated maxiumum. Most modern production valves don't take kindly to being run at their maximum ratings.
Yes, unfortunately from the OP's perspective, the reality is that very few modern tubes can emulate the sonic performance and reliability of the original G.E.C KT88 output valves. Not good news when potentially, you are looking to source an octet. Have you a friendly bank manager willing to give you an overdraft !
 

bigrod

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Because of the inherent problems that I see regularly regarding valve amps and again the price of quality valves ,will it be inevitable that valve systems will die out ?
 

Juancho

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too many designs seem to assume that KT88s are as bullet proof as the original GEC variants, so they push the plate voltage and current close to (or even above) the stated maxiumum. Most modern production valves don't take kindly to being run at their maximum ratings.
I've converted a lot of these to KT120s for this reason. It generally means squeezing an extra filament supply tx in but then KT120s are happy with higher dissipation and plate voltages
 

rabski

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Because of the inherent problems that I see regularly regarding valve amps and again the price of quality valves ,will it be inevitable that valve systems will die out ?
I suspect not. In fact, I see it the other way round. Valves are still being manufactured and there are anyway massive amounts hidden away in people's collections.

People tend to make a big fuss when a valve amp fails, possibly because it can be more spectaular. However, my experience (and I suspect I am far from alone in this) is that solid-state gear is just as likely to fail. The major issue is that contrary to popular belief, a great many solid-state components are long out of production and impossible to get. Substituting alternatives is also often far more complicated than it is for valves, and sometimes simply not worth it, because a major redesign would be needed.

I have yet to see any valve amplifier that can't be repaired. I have, on the other hand, had more than a couple of solid-state ones here that were pointless to even look at, as the output devices are no longer obtainable.
 

StingRay

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Just looked and Amazon have the Psvane KT88 for £292 for four which seems to be as sensible a price as can be expected . As Richard says do you really want to spend lots more on the hope they will be better ?
Make sure they are exactly the same type. Psvane do several different versions, I got caught out once. Do you have a link to that sale, I can't find it on Amazon. On another sale, meant to be matched quad but the buyer said they were not.
Psvane have a good rep.
 
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Non-Smoking Man

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Psvane are pretty good imo.
But the advice to get them tested seems valid.

Jack NSM

Valve amps are less stressed in a multiway active system where they are doing duties in a narrow frequency band and kept away from punishing bass duties and passive XOs. (Just thought I'd mention that..)
 

montesquieu

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Most modern KT88s are (in general) not very good compared to KT88s of old, and the premium for NOS GE KT88s is justified IMO (assuming there are any genuine ones left out there).

I would suggest in particular you avoid Sophia Electric KT88 which in my case lasted a matter of weeks, bought direct from Sophia but they didn't want to know when ALL FOUR faded away to nothing within a very short space of time. In terms of construciton, I'm told they are basically basic Shuguangs in blue bottles.

Golden Lions are about the best current production in my experience, and I have a set handy, but I tend to use KT90s or KT120s if the circuit will manage it. I'm a big fan of KT90s and use them in my Radford STA100 (a KT88 amp from 1967) - tonally they are like giant EL34s with a bit more grip at the bottom but also slightly sweeter at least in this implementation than current production KT88s or KT120.

KT120s vary in performance according to circut so it's hard to generalise ... in some cases they are drop-in for KT88s and some swear by them, but do check the spec of the specific amp with someone who knows about such things. I whipped mine out though and put KT90s back in, both work in my amp (with Will Moores' Radford Revival transformers) but the KT90s just sound more musical and I can't hear any difference in output or bottom end.

Very very hard to generalise though ... as with a lot of valves it's all about the circuit they are operating in.

I should add, as a recovering single-ender I prefer push pull KT88 configuration to any other amp out there driving real-world speakers. Single ended amps have the potential to sound wonderful but are let down in so many cases by the absence of speakers that can really perform under low output/high output impedance conditions.
 

Non-Smoking Man

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Terrific post, Tom - you are a credit to the Wam with your wealth of hands on experience, and straight from the shoulder delivery.
As a postscript to your last para, I should add that my recently acquired Silk Glowmaster, courtesy of Dom (this Parish) (a PP KT88 design) is doing wonders for my horn system's midbass. The driver in question is quite a rare beast - a Vitavox AK157, the working class, ferrite, version of the AK152, the alnico Vox Olympian midbass driver.

SETs mostly on the compression drivers, but then you would wouldn't you, with 115 db/w available..

Jack
 

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I should add, as a recovering single-ender I prefer push pull KT88 configuration to any other amp out there driving real-world speakers. Single ended amps have the potential to sound wonderful but are let down in so many cases by the absence of speakers that can really perform under low output/high output impedance conditions.
That's why I invested in Atma-sphere amps which give you pentode power but triode sweetness. My PP KT88 amps sounded less silky Vs the Atma-sphere amps, and I can't see myself ever returning to pentodes.

Mine are 150w into 2/4/8 ohm.
 
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montesquieu

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That's why I invested on Atma-sphere amps which give you pentode power but triode sweetness. My PP KT88 amps sounded less silky Vs the Atma-sphere amps, and I can't see myself ever returning to pentodes.

Mine are 150w into 2/4/8 ohm.

Not all speakers work well with the high output impedance of transformerless output. Tannoys generally don't, for the same reasons they seldom shine with single ended. I've found TFL amps very pleasant - smooth as you suggest, but lacking in low-end articulation and midrange timbral texture with the Tannoys in my favoured musical genres that I get with the Radford. I looked at the Atma-spheres and decided against, though can imagine scenarios where they would work very well.

As always it depends on the speaker, what amp or amps you are comparing it with, and your personal preferences. Every topology comes with its own set of compromises.
 

Psilonaught

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Not all speakers work well with the high output impedance of transformerless output. Tannoys generally don't, for the same reasons they seldom shine with single ended. I've found TFL amps very pleasant - smooth as you suggest, but lacking in low-end articulation and midrange timbral texture with the Tannoys in my favoured musical genres that I get with the Radford. I looked at the Atma-spheres and decided against, though can imagine scenarios where they would work very well.

As always it depends on the speaker, what amp or amps you are comparing it with, and your personal preferences. Every topology comes with its own set of compromises.
I can't imagine anyone buying Atma-sphere amps for horns. My point was that you CAN drive tricky speakers with triode amps.
 

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