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My Favorite Tubes and Their Substitutes

12-03-2014 | By Robert H. Levi | Issue 76

I love and appreciate tube based audio gear and own sixteen pieces of tube gear between my two reference systems. Without a thorough knowledge of tube types and their substitution possibilities, you may be over-paying for your new or NOS tubes you employ, or just pick the wrong ones. This data is based on my experience, and input from my electrical engineering audiophile friends. Substitutes may be used freely for the extreme majority of all circuits. As always, use what sounds best as each tube will have its own character within the type and brand selected. Knowledge is power, and knowing an unusual substitute may be a true joy.

Small Signal Tubes:


Substitutes: ECC83, 12AX7A, 12AX7WA, 7025, 5761,6057,6681,7494,7729, 7025#, ECC83#, 6L13, 12DF7, 12DT7, 5751, 7025A, B339, B759, CV4004, E83CC, ECC803, M8137

The GE 5751 is a bargain basement musical giant! The Mullard CV4004 is still King of the Hill.


Substitutes: 12AU7A, ECC82, 5814, 5814A, 5814WA, 6189, 6680, CV4003, E82CC, ECC186, ECC802, ECC802S, M8136, 7025#, ECC83#, B749, 6067, 6670, 7730, B329, 5963, 7316, 7489

I discovered the 5814A from RCA is a bargain and the best sounding 12AU7 made in the USA!

The Mullard CV4003 is still fairly cheap, plentiful, and magnificent.


Substitutes: 6201,6679, ECC81, 12AT7WA, 12AT7WB, 6060, 6201, 6671, 6679, 7492, 7728, A2900, 8152, B309, B739, CV4024, E81CC, ECC801, ECC801S, M8162, QA2406, QB309

As good as the GE and RCA are, the Mullard CV4024 is not pricey and totally glorious.


Substitutes: ECC88, 6ES8#, 6ES8, ECC189, ECC189#, 6FW8, 6KN8, 6922, E88CC, CV2492

The bargain priced PCC88, the 7 volt version of this tube, works nicely in the vast majority of 6 volt applications. I use them in a cocktail with their 6 volt brethren all the time for top results. You can still actually afford the Telefunken, Dutch Amperex, and Siemens versions of the PCC88! 

Rectifier Tube:


Substitutes: GZ34, 52KU, 53KU, 54KU,GZ30, GZ32, GZ33, GZ37, R52, U54, U77, 5R4GYS (from Philips) The Mullard GZ34 is King of the Hill. Buy it used, but checked, if necessary. The Philips 5R4GYS is a recent find by Upscale Audio in Upland. A killer tube, but huge and requires lots of space (bigger than a KT88.)

Other Dual Triode Tubes:


Substitutions: 6SN7A, 6SN7GT, 6SN7GTA, 6SN7GTB, 6SN7W, 6SN7WGT, 65W7, 5692, B65, ECC33, 6SN7L, 13D2, B65, 6SN7GTY, 6SN7WGTA

The available brands of these tubes are highly variable musically and microphonically. The vintage GE and RCA are very fine if hand selected. The Electro Harmonix is very good, too.


Substitutions: 5691, 6SL7W, 6SL7WGT, 6113, ECC35, 6SL7GT, 6SL7L

Same comment as 6SN7 type.

Output Tubes:


Substitutes: 6BQ5, 6P15, 6267, 7189, 7189A, 7320, E84L, EL84L, N709, Z729, 6BQ5WA, EL84M  I have had little use for these. Am told the NOS Mullard prices are strong, but worth it.


Substitutes: 6CA7, 7D11, 12E13, KT77

Lots to choose from. Usually your manufacturer tuned the gear to a certain brand of these. Be mindful of that before you spend tons of money on vintage NOS versions that end up not sounding as good.


Substitutes: 7D11, 12E13, 6550A, 7027A#, KT88, KT90 Type 2 or 3, KT99, KT100, KT120/KT150 (only if sufficient bias is present)  Unless forbidden by your manufacturer, I would try some of the high powered goodies on the market to boost performance. The EH KT90 or the new KT120 may be astounding in your amp. At least try KT88s!


Substitutes: KT66, 5881, 6L6S, 6L6G, 6L6GA, 6L6GAY, 6L6WA, 6L6WGA, 6L6WGB, 6L6WGC, 6L6WGT, 6L6GB, 6L6GC, 6L6GT, 6L6GX, 6L6Y, 1622, 5932, 7581, 7581A, WT6, EL37

Same comment as EL34 type. 


Substitutes: 6550, 6550A, KT90 Type 2 or 3, KT99, KT100, KT12O/KT150 (only if sufficient bias is present)  Though your manufacturer may have settled on a certain brand of these, the hunt for cool NOS types may be sonically worthwhile, or try switching to EH KT90s or bigger for more impact. I would!

If in doubt, check with your manufacturer before substituting. The above substitutions have been checked as carefully as possible. Rule of thumb for tube rollers: If it sounds good, you will be fine. If it does not, pull it (with the gear off, of course!) and try something else.

I will enhance this list in the future. Write me via Positive Feedback if you have a tube type you want discussed.

Good hunting!

Bob Levi, President Los Angeles and Orange County Audio Society
Now with over 1700 Members
8144 E Bailey Way
Anaheim, CA 92808
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