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KT88 vs 6550 vs ? for warm midrange - using Cronos Mag lll

I've been listening to an ST70 with EL34 Tubes & really enjoy the Sound .

Using the Cronos with KT120's  it's a different sound / feel - sounds wonderful but seems either more balance / neutral overall . Maybe more lower end but not as sweet in mid range as the 34's 

34's in the cronos is possible but not really advisable [ too much current into tubes - 1/2 the life span  even with proper biasing ] 

I've been running the amp in Triode mode and seem to prefer sound .  Listening levels are moderate / low  avg 75 db 

I'm good with the kt120's but maybe another tube would bring more mids to the game 

 

* Note - I have changed All the preamp tube to NOS - It has been a significant improvement !-  Telefunken is at center  12au7 , flanked by RCA clear tops , 2 GE ax7 's 

Any suggestions for power tubes is most welcome - Rogue audio is shipping  kt88's in lieu of the 120's [ for yrs due to war etc.] 

what's gained or lost when changing from the 120's ?

 

forgot - Primary Speakers - Dynaudio special 40's , primary source is Vinyl 

 

Thanks  

 

mfm22
dekay's avatar
dekay
5,841 posts
 

Also, have you tried a lower bias setting on the power tubes you are using?

Doing so (within reason) may move you further towards the sound you are seeking.

Try it for free before shopping for alternative signal/power tubes.

 

DeKay

 

PS:

I’m a big ST-70 fan.

 

knotscott's avatar
knotscott
1,154 posts
 

It’s always subjective, and every tube behaves a bit differently in each circuit, but I’m finding the Tung Sol 7581A (a 6L6 variant) sounds superb in my Dyna/VTA 70s. I’ve run a few EL34s, and I really liked the Gold Lion KT66, but have been absolutely thrilled with the musicality, clarity, and texture the 7581As produce, along with 12BH7a driver tubes in these amps. Best of all, they’re not super expensive.

bpoletti
1,566 posts
 

This might be a little extreme, but you might experiment with different output transformer taps.  

decooney
2,358 posts
 

Lots of talk on other/older threads about the center tube in this amp.  While I run KT120s and 12au7s in different brand amps, the sound will change notably with different 12au7s in mine.  Seems like the lowest cost and easiest option to retrace steps on that front-center tube.. If I install the same Telefunken or GEs in mine for this spot, its a more detailed and lean sound with less warmth/body fwiw.   

 

rbstehno
1,552 posts
 

I had the Cronus magnum II with kt-120’s. I changes all the other tubes for the phono and preamp sections. 
The only reason I got rid of that amp is the flabby bass. There was a lot of bass but not impactful. Tried the 4 ohm load setting with not much of a change. So it’s not how much bass these tubes put out, it’s the quality.

There was a big improvement when changing out all the other tubes.

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