ST-120 Brighter Driver Tube

12AU7, 12BH7, 5693, 5814 or 6189 can all be used in the driver stage of the ST-120. I'm specifically testing different tubes in the center position. Changing the center tube is where you notice the biggest difference on the ST-120.

The Mullard CV4003 is my favorite flavor for that center driver tube. It is the one I listen to 90% of the time and I'm sure it will remain my favorite because i prefer that darker sound on most of my music.

I would also like to try the opposite end of the spectrum since there is one genre of music that I sometimes listen to where I would like to find the brightest tube for.

What tube brand and model would you recommend that will increase the volume of the frequencies above 10Khz ? I am not asking about frequency response. I'm asking about tonal quality and linearity. I'm looking for a non-linear response in which the very high frequencies are at a higher volume.

Kind thanks,
Eddie

I know that the 12AX7 Telefunken is probably the brightest tube there is. I don't know if the 12AU7 version of that tube is as bright. I love the tube for that reason, many hate it for the same reason. You want old stock version of this tube. I have seen a couple that were for sale used for around $35.

The RCA clear tops tend towards bright, and you can usually find them on the cheap ... no big loss if they don't do what you want them too. Exceptional tone for the money ...

I got a Tele 12AU7 in the center right now, and yes, they are bright. At one time, TOO bright here, but that was the room acoustics. I've since carpeted the ceiling at the primary reflection points and that killed the shrill ...



And it IS fun telling visitors to wipe their feet ... and then pointing up ...   

sailor wrote:I know that the 12AX7 Telefunken is probably  the brightest tube there is. I don't know if the 12AU7 version of that tube is as bright. I love the tube for that reason, many hate it for the same reason. You want old stock version of this tube. I have seen a couple that were for sale used for around $35.

Can the "AX" be plugged right into the ST-120 ? without any mods? The AX is not the same as the AU right?

I believe sailor was suggesting only that Telefunken's 12AU7/ECC82 might have a similar sonic signature to their 12AX7/ECC83.  Don't use a 12AX7 in your ST-120.

Try the RCA "clear top" 12AU7s for your needs.

That's correct, I only brought up the AX because I knew what it sounded like and thought the AU would have similar sound characteristics. skizo confirmed my suspensions that the Telefunken 12AU7 was also on the bright side but very detailed. The AX [100] has 5 times the gain of a AU [20] and you would not want to substitute one for the other. But the good news is that the 12AU7 is easier to get and cheaper. But they still are in short supply so a NOS will be in the $75 range.

What is the general consensus on the 12bh7?  Some say that the 12bh7 is always superior in every respect over a 12au7.  
I just switched over (with great anticipation) to a trio of  70's  grey plate RCA 12bh7 and I think they are just 'so-so'.  
I am not that impressed and I will likely go back to my Mullard 12au7.

Regarding Cleartop 12au7;  I like bright sound, but does anyone else feel that the clear tops lack 'fullness'?  They sound 'thin' to me. I was trying those 'CONN' branded cleartops, maybe I need a set of nos?

I've never gone wrong with RCA clear-tops in at least the 6CG7 and 12BH7A iterations.
There was a batch of RCA clear-tops produced in Brazil in the 1970s as replacements for when the U.S. factories shut down, and I hear their QC was not good. Slugs of them on FleaBay. The Brazil factory had good access to the base metals but not the rare-earths that went into the originals. It was a stop-gap while everyone geared up for solid-state, but TV repairmen still needed vacuum tube subs.

12BH7A clear tops?

That's a new one on me ... tell me more!

I don't see any 12BH7 clear top tubes in that listing.  Does such a thing exist? I have seen 12AU7 and 12AX7 clear tops...

EddieGnz1 wrote:12AU7, 12BH7, 5693, 5814 or 6189 can all be used in the driver stage of the ST-120.  I'm specifically testing different tubes in the center position.  Changing the center tube is where you notice the biggest difference on the ST-120.

The Mullard CV4003 is my favorite flavor for that center driver tube.  It is the one I listen to 90% of the time and I'm sure it will remain my favorite because i prefer that darker sound on most of my music.

I would also like to try the opposite end of the spectrum since there is one genre of music that I sometimes listen to where I would like to find the brightest tube for.  

What tube brand and model would you recommend that will increase the volume of the frequencies above 10Khz ?  I am not asking about frequency response.  I'm asking about tonal quality and linearity.  I'm looking for a non-linear response in which the very high frequencies are at a higher volume.

Kind thanks,
Eddie

Why not use tone-controls ?

skriefal wrote:I don't see any 12BH7 clear top tubes in that listing.  Does such a thing exist?  I have seen 12AU7 and 12AX7 clear tops...

I stand corrected; my BH7As are silver-topped. I was thinking of the 12AU7. Apologize for the mis-information on that.

My information on the Brazil-made RCA 6CG7s being not up to snuff is from Andy Bowman, who is a walking encyclopedia on all things tube.

Make me an offer ...

sKiZo wrote:Make me an offer ...

Nice PhotoShop.

 

I'll work on it a bit and post it around the net.

Years from now, audiophiles will be searching high and low for their very own pair at exorbitant prices ...

sKiZo wrote: 

I'll work on it a bit and post it around the net.

Years from now, audiophiles will be searching high and low for their very own pair at exorbitant prices ...

You could call it the special-edition 12BS7A