Tubes - any advise?

acalex

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Hi everybody,

I have opened this thread to understand a bit better the differences between KT88 and KT90 tubes and get some advice on what I could expect if I swap my KT90 with some KT88 in terms of sonic differences.

I actually have some Electro Harmonix KT90EH tubes (4x) and was thinking about getting a matched quad of KT88 from the same brand or the Genalex Gold Lion KT88. I was also wondering why the KT88 from EAT (the diamond ones) are so expensive compared to the Gold Lion?

Lots of questions I know, but I am quite new to this world and would like to dig more. So any comment/advice are more than welcome

Thanks a lot

Alex
 

Overdose

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Before you go swapping bits about, bear in mind that the circuit you are tinkering with has been designed as a whole and the components within it selected for optimal effect. If you change components and you get lucky (and it will be luck), then you may change the sound to be more to your liking, but you might also adversely affect the sound and worse, cause some damage by fitting inappropriate components.

This is no different in this regard, to op amp 'rolling'.
 

CnoEvil

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Well my friend, for once you've picked a topic about which I have nothing to say.....will be reading with interest though.
 

oldric_naubhoff

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Overdose said:
Before you go swapping bits about, bear in mind that the circuit you are tinkering with has been designed as a whole and the components within it selected for optimal effect. If you change components and you get lucky (and it will be luck), then you may change the sound to be more to your liking, but you might also adversely affect the sound and worse, cause some damage by fitting inappropriate components.

This is no different in this regard, to op amp 'rolling'.

you're mixing apples with apes here. most pentode based designs can use different variations of that tube interchangebly. and indeed, in case of Acalexe's amp the user has a choice of using 6550, kt88, or kt90 pentode tubes. see manufacturer's spec sheet if in doubt.
 

acalex

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Overdose said:
Before you go swapping bits about, bear in mind that the circuit you are tinkering with has been designed as a whole and the components within it selected for optimal effect. If you change components and you get lucky (and it will be luck), then you may change the sound to be more to your liking, but you might also adversely affect the sound and worse, cause some damage by fitting inappropriate components.

This is no different in this regard, to op amp 'rolling'.

Overdose, thanks for the warning but the Jadis D50 is produced with KT88 and can accomodate the KT90 and the 6550. So there is no harm/problems in changing them. My Jadis was delivered to me already with the KT90 but I was wondering what would it change swapping with the KT88...
 

acalex

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CnoEvil said:
Well my friend, for once you've picked a topic about which I have nothing to say.....will be reading with interest though.

Great, a person with your experience can always provide great insights/comments on the topic anyway :)
 

eggontoast

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acalex said:
Hi everybody,

...... and was thinking about getting a matched quad of KT88 from the same brand or the Genalex Gold Lion KT88. I was also wondering why the KT88 from EAT (the diamond ones) are so expensive compared to the Gold Lion?
Alex
I take it you are referring to current build Genalex valves and not NOS KT88's as a matched quad of NOS will set you back about £700. The current Genalex Golden Lion valves are built in the same factory as the Electro-harmonix along with Sovtek, Mullard, tung sol, Svetlana (not SED) in the Reflector factory in Saratov. The new sensor corporation pulls the strings and as of late the quality of the valves is extremely inconsistent. Be sure to purchase any of theses valves from a third party distributor which burns the valves in well to stabalise them. If you are of the older generation you will recognise the above names as manufacturing valves back in there heyday, don't confuse the two, New Sensor has simply purchased the rights to the names. The valve designs bear no resemance to the originals in terms of build or quality. IMO one of the best KT88's you can currently still get are SED (svetlana in St Petersburg) ones although these are now no longer manufactured either.
 

Overdose

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oldric_naubhoff said:
Overdose said:
Before you go swapping bits about, bear in mind that the circuit you are tinkering with has been designed as a whole and the components within it selected for optimal effect. If you change components and you get lucky (and it will be luck), then you may change the sound to be more to your liking, but you might also adversely affect the sound and worse, cause some damage by fitting inappropriate components.

This is no different in this regard, to op amp 'rolling'.

you're mixing apples with apes here. most pentode based designs can use different variations of that tube interchangebly. and indeed, in case of Acalexe's amp the user has a choice of using 6550, kt88, or kt90 pentode tubes. see manufacturer's spec sheet if in doubt.

Rethep said:
Sorry to say but they are all TETRODE tubes!

:grin: At least someone knows what they're talking about here.

Either way, using a set of relatively expensive valves as tone controls, seems a bit excessive to me. Does the amp not come with tone controls?
 

acalex

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Who said I want to control the tone? :rofl:

I just would like to know which changes should I expect if I purchase a second set of KT88 instead of KT90. What are the sonic differences between the two sets?
 

acalex

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eggontoast said:
acalex said:
Hi everybody,

...... and was thinking about getting a matched quad of KT88 from the same brand or the Genalex Gold Lion KT88. I was also wondering why the KT88 from EAT (the diamond ones) are so expensive compared to the Gold Lion?

Alex

I take it you are referring to current build Genalex valves and not NOS KT88's as a matched quad of NOS will set you back about £700. The current Genalex Golden Lion valves are built in the same factory as the Electro-harmonix along with Sovtek, Mullard, tung sol, Svetlana (not SED) in the Reflector factory in Saratov. The new sensor corporation pulls the strings and as of late the quality of the valves is extremely inconsistent. Be sure to purchase any of theses valves from a third party distributor which burns the valves in well to stabalise them. If you are of the older generation you will recognise the above names as manufacturing valves back in there heyday, don't confuse the two, New Sensor has simply purchased the rights to the names. The valve designs bear no resemance to the originals in terms of build or quality. IMO one of the best KT88's you can currently still get are SED (svetlana in St Petersburg) ones although these are now no longer manufactured either.

Thanks for the explanation. I indeed saw that the NOS Genalex (made in Britain) are no longer available and quite costly.
Didn't know that all the others brands are now built in the same factory...thanks for that.

Why do you think the Svetlana SED KT88 are the best? I found a matched quad of KT88 SED C, what does the C stands for?

Are the EAT KT88 DIamond any good? As I don't understand their price (around 1400 USD for a matched quad).

How would you describe sonically difference between KT88 and KT90?

Thanks a lot and sorry for all the questions :)
 

Overdose

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acalex said:
Who said I want to control the tone? :rofl:

I just would like to know which changes should I expect if I purchase a second set of KT88 instead of KT90. What are the sonic differences between the two sets?

You did, by implication that you were looking for a different sound by swapping valves. If you are changing the sound presentation, you are changing the tone.
 

SDIESEL77

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IMO After trying multiple brands of KT88 (Golden Lion, Tesla, Electro Harmonix,...), my favourite ones remains the Shuguang Gekt88. They're great tubes! Next time, if I have the money, I ll try the Shuguang KT88 Treasure which are apparently the best new tubes you can now buy.
 

acalex

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SDIESEL77 said:
IMO After trying multiple brands of KT88 (Golden Lion, Tesla, Electro Harmonix,...), my favourite ones remains the Shuguang Gekt88. They're great tubes! Next time, if I have the money, I ll try the Shuguang KT88 Treasure which are apparently the best new tubes you can now buy.

Interesting...why you rate so much the Shuguang compared to other brands? Any direct comparison with KT90?

Thanks
 

acalex

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Overdose said:
acalex said:
Who said I want to control the tone? :rofl:

I just would like to know which changes should I expect if I purchase a second set of KT88 instead of KT90. What are the sonic differences between the two sets?

You did, by implication that you were looking for a different sound by swapping valves. If you are changing the sound presentation, you are changing the tone.

I think you misunderstood the sense of my thread, not a problem at all...I was probably not clear enough!

If you read my OP I say "...and get some advice on what I could expect if I swap my KT90 with some KT88 in terms of sonic differences"

I never said I want to swap now...as my tubes are relative young. I asked what I need to expect in terms of sonic difference between a set of KT90 (which I own) and a set of KT88 (which I never tried). I am thinking about getting a second set of tubes to start expermienting as I like very much to know all the variables in play :shifty:
 

Overdose

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Of course, there is absolutely nothing wrong with what you want to do, but the result is what it is, a tone adjustment.

I have embarked upon a series of DIY projects in the past, including DACs, preamps and power supplies and have done a fair bit of reading (although perhaps not fully understanding). It's fun to experiment and helps make better informed decisions about future purchases. I found it better to reasearch and experiment with relatively cheap DIY kits and components before shelling out big money on finished articles.

Can you not audition said valves from the shop you bought the amp from? Presumably, if the valves in the amp are designed to be swapped, the shop would have some approved samples to try?
 

acalex

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Overdose said:
Of course, there is absolutely nothing wrong with what you want to do, but the result is what it is, a tone adjustment.

I have embarked upon a series of DIY projects in the past, including DACs, preamps and power supplies and have done a fair bit of reading (although perhaps not fully understanding). It's fun to experiment and helps make better informed decisions about future purchases. I found it better to reasearch and experiment with relatively cheap DIY kits and components before shelling out big money on finished articles.

Can you not audition said valves from the shop you bought the amp from? Presumably, if the valves in the amp are designed to be swapped, the shop would have some approved samples to try?

Yes, I think this is the best solution, trying different types and get an idea myself about how different valves would perform. I was trying to llok here for more general guidelines like fore example KT88 is less dynamic but warmer than KT90 (making up this statement now). It is always better to have a well developed idea before letting a sales person stiring you!
 

a91gti

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Just had a butchers on DiyAudio. Your question is of interest to me as my amp runs EL34 and these can be exchanged for KT88. This may be of interest from both a tech' point of view and with regards to sonic differences.

http://www.diyaudio.com/forums/tubes-valves/110058-replacing-kt88-kt90-beginners-questions.html
 

acalex

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a91gti said:
Just had a butchers on DiyAudio. Your question is of interest to me as my amp runs EL34 and these can be exchanged for KT88. This may be of interest from both a tech' point of view and with regards to sonic differences.

http://www.diyaudio.com/forums/tubes-valves/110058-replacing-kt88-kt90-beginners-questions.html

I suggest you read this one also, very interesting exchange

http://www.whathifi.com/forum/hi-fi/tubes-any-advise#comment-2735647
 

eggontoast

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acalex said:
Why do you think the Svetlana SED KT88 are the best?
SED manufacture the best quality valves with regards to consistency and reliability.
acalex said:
I found a matched quad of KT88 SED C, what does the C stands for?
The C refers to the cyrillic S (=C=) used to denote Svetlana, the original Svetlana valve company in St Petersburg (now SED) use this logo since a trademark dispute with New Sensor over the Svetlana name. The New Sensor Svetlana brand name should only be used in North America, they are not allowed to legally use it anywhere else in the world.
acalex said:
As I don't understand their price (around 1400 USD for a matched quad).

if you look hard enough there is always someone ready to rip you off.
 

egoBen

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Alex, did you ever get the chance to compare your KT90 with KT88's?

I tried a pair or TAD KT88 tubes earlier this year but didn't notice any big difference from my current Ei 6CA7. I have recently ordered four GE 6550 (NOS) and four new EH KT90 tubes, just for fun, to compare. And I need spares aswell, just in case my current tubes will blow up or "run out". I am not dissatisfied at all with the tubes I have, but they are no longer in production as the factory in Yogoslavia was bombed or something. I will try to get back later with impressions, if I remember!

Happy new year! :cheers:
 

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