Electro-Harmonix KT90EH Power Vacuum Tube (Matched)

3 Reviews

Availability: Usually ships within 24 hours.

USD $‎83.95

Need matched power tubes? Don't worry! Price includes matching in any quantity you need for no extra charge. Need a matched pair? Just order "2" tubes. For a matched quad order "4" tubes. Matched sextets and octets are available as well.

The Electro Harmonix KT90-EH vacuum tube is a suitable replacement for any KT88 or 6550 power tube. This KT90 tube is an excellent quality tube and a solid performer in both hifi and guitar amps. The bass is solid and defined, mids are balanced, and the highs are smooth and clear.

Other Electro-Harmonix tubesKT88 Tube Types

Additional Information and Downloads

Tube Matching Information:
Power Tube Matching FAQ
Perfect Pair System

Electro-Harmonix KT90EH Datasheet (PDF)

Download Adobe Acrobat PDF reader

Warranty Information and Return Policy

Warranty Period: 3 months

All our tubes are guaranteed for 3 months from the date of purchase. (Any exceptions will be noted on that tube's Warranty tab)

If you receive a tube that does not perform to the manufacturer's specifications, please do the following:

- contact us to get a return authorization
- return it via regular mail within 90 days from when we shipped it, and we will provide an exchange or refund of the full purchase price of the tube.

Returns not related to warranty or defect will be considered at our discretion, and are subject to a 15% restocking fee.

We can not accept returns that don't have an authorization, are past 3 month, or are returned improperly.

These guidelines may be updated without notice.

Ratings & Reviews

3 reviews

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Electro-Harmonix KT90EH | Best tube for KT88 or 6550 equipped Marshall and Blackstar amps.


They sound excellent in my Blackstar Series One 200 amp. Although EHX claims that it sounds like a cross between an EL34 and KT88 but my experience is different. To my ears the sound signature of these EH-KT90 tubes is like a cross between a KT88 and the old Sylvania Fat Bottle 6CA7.

Its mid range response is quite similar to the fat bottle 6CA7. Just like the 6CA7 it has more mid-range than a 6550 and KT88, but it's a lot cleaner and less mid heavy than a British EL34. Its high end response is somewhere between the fat bottle 6CA7 and a KT88. Its low end is deep, big and clear like a KT88 though.

It's an interesting tube, and suits my Blackstar better than the stock KT88 tubes. It isn't as linear and transparent as a KT88, but the flavor added by this tube works right for my amp. It makes the Blackstar Series One 200 sound a lot closer to a Marshall.

Great replacement for KT88


I am using Yaqin MC-100B which come with KT88. The stock amp is powerful but the bass is loose and a bit sharp on the top. The staging also almost flat. Initially I thought it was because my ears are get used to 300B sounds.

One day, I have a change to replace the KT88 with this EH KT90. After setting the bias, I play my favorite music and WOW.

I hear something is very new. The low end is tight and controlled. Top end also softer and smooth and the sound stage is back. I feel my speakers are disappeared.

I am very satisfied with my decision to use this KT90.



Excellent sound quality. This does live up to its description.