Tube rolling MV60SE

[Vick]

Hi everyone,
on Monday I received the final in question, bought used.
It arrived with 4 6550 unknowns, 2 6sn7s also unknown and 2 12ax7 Electro Harmonix.
I have kept at home 4 GE 6550A JAN Military Grade in Green letterings, which I will use instead of the ones it came with, but I don't know whether to replace and possibly with what, the 6sn7 and 12ax7.
Can you help me?
Thanks

[Truth71]

What are you hoping to achieve in terms of the sound?

[admin]

What are you hoping to achieve in terms of the sound?

I think this is a great question. More detail? More warmth? Tube longevity? Lower noise floor?....

[Vick]

I have no other references, I wanted advice from those who did some tests

[AnotherJohnson]

Why not use it with the tubes supplied to get a baseline sound for comparison?

If you’ve priced tubes lately, you may quickly learn to appreciate the ones you already have.

[Vick]

Because I have not and I don't know which are original tubes

[admin]

Hi Vick,
What AJ is alluding to is the massive price increase in tubes recently due to Ukrainian war and subsequent Russian embargos. I think once the conflict resolves and the massive tube buying craze calms down, you will see prices of tubes come down back to normal levels and availability return. Unless money is no object or there is a good reason to, I would probably hold off on rolling tubes for now.

[Truth71]

To start: 12AX7 original spec were not original spec . CJ used 5751.

The JAN GE 6550 were what the amp was voiced on. I have found them fantastic as output tubes.

[Joe Appierto]

Actually it did use 12AX7. This is from the Owner's Manual:

The MV60SE uses eight vacuum tubes of three different types: two
12AX7A (V1 and V2), two 6SN7 (V3 and V4) and four 6550s (V5
through V8). T

[Truth71]

I stand corrected

[Big Dog RJ]

G'day Vick,

With the MV60SE that I had, used the stock tubes that CJ supplied for about three years. Later on I kept the stock / recommended EH 6sn7 and the input tubes (whatever type it was) both EH brands, and they worked fine!

However, for me the most significant improvement was when I changed the output tubes to KT120's. I checked with JF before doing this and he gave the thumbs . It was such an improvement all round, the MV60SE sounded totally different. It was more powerful and had better control over dynamics and transient grip. It drove my Maggie's, and two models of Quad stats effortlessly!(Maggie MGIIIAa, and Quad ESL 2905 & 2912) full range no subs!

The trannys on the MV60SE and its power supplies are well capable of accommodating the KT120's. These were the Tungsol's and I highly recommend it. I also tried the KT88's Genalex Gold Lions, although the midrange was great, it didn't have the overall full sound compared to the KT120's.

Just my 50cts worth...

Cheers, RJ

[Vick]

Thanks a lot Big Don RJ,
so I can use kt120 without any modification?

[Truth71]

This brings me back to a question I've often posed about the "new" KT tubes...that being, as fas as I know, they are only made by ONE firm in Russia, comapred to the 6550, where there are still tons of NOS available as well as multiple current manufacturers.

KT-120 fans might also want to contact Western Electric and try to add KT-120 to the tubes WE is gearing up to manufacture in the US.

info@westernelectric.com

Scuttlebutt has it that most other tubes are quite easier to make than the WE mainstay 300B

[Big Dog RJ]

Thanks a lot Big Don RJ,
so I can use kt120 without any modification?

Yes you can. Like I said, the trannys designed on the MV60SE are capable of supplying the required current for KT120's. So no issues there at all, in fact due to the KT120's having more headroom, they'll be cruising along...

However, very important *Note!* you can only do this on the MV60SE and not on the non-SE version, so make sure this mv60 is the SE version!

Cheers, RJ

[admin]

This brings me back to a question I've often posed about the "new" KT tubes...that being, as fas as I know, they are only made by ONE firm in Russia, comapred to the 6550, where there are still tons of NOS available as well as multiple current manufacturers.

KT-120 fans might also want to contact Western Electric and try to add KT-120 to the tubes WE is gearing up to manufacture in the US.

info@westernelectric.com

Scuttlebutt has it that most other tubes are quite easier to make than the WE mainstay 300B

Western Electric had a recent survey about what tubes we would like them to make. The link to the survey was posted here on CJO so a search should turn it up. I specifically requested KT120's being added as I believe that currently the only manufacturer is Tung Sol.

[AnotherJohnson]

Here’s the thread admin mentioned. I would like to see the KT150s and the 6H30Pis too. https://www.conradjohnsonowners.com/vie ... php?t=2341