KT-88??

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Hey, I have a DSL100HR and was thinking about changing out the EL-34’s for KT-88’s. I heard they sound better with tight low end and more punch than the EL’s. Anyone have any suggestions or input on this? Or has anyone else done this? And what’s your opinion on the sound.
 

Filipe Soares

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Generally speaking the direct replacement for EL34s are KT77s. I have swapped it in my Engl Savage, but being extremely honest it is a very subtle change - at least in that amp.

Only worth it if you are going to retube it anyway.

Speakers will be a way more dramatic change.
 

EADGBE

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Yes don't put KT-88s or 6550s in that amp.
 

Kinkless Tetrode

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The KT88 is the KT version of the 6550. It will most likely require modification to the bias supply circiutry of the amp. The KT88 has a plate dissipation of 42 watts, while the EL34 has a plate dissipation of 25 watts. This will require a different voltage range at pin 5 to bias it properly. Some fixed bias amps have enough range in the bias pot but many don't without specific resistor changes.

As Filipe said, the KT77 is the KT version of the EL34 and will usually go into an EL34 amp with no modifications other than an bias adjustment, which should be done with all tube replacements of adjustable bias amps like the DSL100HR.
 

mickeydg5

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If you can bias a set of KT88 at or below 42mA then you will be fine as is other wide bias will need modification.

Yes 6550 type and KT88 will provide a different feel and lower end. A KT88 may provide a bit warmer and more breakup sound to uppers over the 6550 but the 6550 can be more clear.
 

Pete Farrington

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The KT88 has a plate dissipation of 42 watts, while the EL34 has a plate dissipation of 25 watts
That may be an apples to oranges (absolute max to design centre limit) comparison.
In reality the differential will be somewhat less.
KT88 design max limit is 35W, that of the EL34 is probably about 30W.
 

mickeydg5

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25, 30 or 35 watt plate makes not difference since it should be biased per amplifier design which is that of a 100W. The design made use of 25W power tubes.
 

XTRXTR

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I have EH KT 88s in my 20th Anni 2204. I have not played that in a long time, sounds great. Keep the bias cool, and had to modify the bias resistor, I think...

My shuguang KT 66s are to tall, only fit in my rack mounts 2204 4U height had to set with space for 5U to fit.
 
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If you can bias a set of KT88 at or below 42mA then you will be fine as is other wide bias will need modification.

Yes 6550 type and KT88 will provide a different feel and lower end. A KT88 may provide a bit warmer and more breakup sound to uppers over the 6550 but the 6550 can be more clear.
Yes I’m looking for more breakup
 
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If you can bias a set of KT88 at or below 42mA then you will be fine as is other wide bias will need modification.

Yes 6550 type and KT88 will provide a different feel and lower end. A KT88 may provide a bit warmer and more breakup sound to uppers over the 6550 but the 6550 can be more clear.
That’s what I’m looking for: lower end and a warmer feel
 

neikeel

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I think mickeydg5 was comparing KT88s with 6550s, not EL34s. In general the EL34s will be warmer with more crunch when biased at the warmer end of the safe zone. I really like 6550s for heavy stuff in a JMP100w (biased as 25w tube) and KT88s in a 50w but biased more like 30w but you have to have a suitable PT or you will run the risk of melting it!
To me they are fatter with more body and low end than EL34s. YMMV.
 

Kinkless Tetrode

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Yes I’m looking for more breakup


You will probably get less breakup with KT88s compared with EL34s. If you want more bottom but without later breakup go for the fat bottle 6CA7s.

On edit: And they should go right in with no mods. You must always re-adjust bias on a DSL100, nevertheless.
 
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