My new amps, on the theme of Paramount

[Paul Birkeland]

Something like a 6SN7 doesn't have a center-tapped heater, so there's no option to only heat half of it.

FWIW, I would expect an old stock 6SN7 to last well over 30,000 hours. 

On the other hand, you could migrate to a 6J6 regulator and 6J5 driver tube if you are interested in getting more glass onto the chassis.

[johnsonad]

Thanks Paul.  I've got a stash of 6J5's though I'm so happy with the 6SN7 I find little reason to change it. With a lifetime like that, my stash will last longer than I will.

[johnsonad]

Yesterday thanks to the local tube guys I finalized my selection of 6SN7's to roll through these amps.  I've been using a pair of Sylvania 6SN7WGTA'a 90% of the time but with the recent changes to the system as a whole they are starting to sound a little lean.  Here is what I walked away with:

one Tung Sol VT-231 round plate, black glass (I had one already)
two Ken Rad VT-231's black glass
one Raytheon 6SN7WGT (had one already)
four Sylvania CHS 7N7 tubes in boxes marked 1942.

If your calculations hold true PB, I've got tubes for more than one lifetime

[johnsonad]

I swapped the KBG PF cap for a Rike Audio cap a week or so ago.  I really like the KBG's and they offer a lot of bang for the buck.  The Rike in these amps sounds great.  Strings sound better and the music seems to have more feeling and weight to it.  The attack is not as good as it was with the KBG's and the decay isn't as airy.  This may improve with break in.  We overall like the results and they are going to stick around for a while. 

There were a few rapid changes to the system.  The first being the removal of the grid chokes.  In talking this morning, with their removal the sound was more precise but lost some body We also noticed the music could be painful at times.  Though it was more precise we weren't sure if it was more correct or not.  Next was the PF cap swap.  The music sounded more correct but thin and painful at times.  The strings were better but still lacked some body(not metallic sounding anymore).  This was throughout the mid range.  Today I swapped drivers from the Sylvania 6SN7WGTA (short bottle, brown base) to the Ken Rad VT-231.  The mid range depth and weight returned in spades.  We were both impressed by the improvement overall to the entire frequency range.  The sound became more intimate on our usual test recordings.  The attack is still not perfect but the sound is wonderful.

I've said it many times but everything makes a difference to the overall system.  What works for one person may not work for everyone.  In my case, the Sylvania tubes I think helped compensate for the grid chokes.  When we had used RCA grey glass drivers, the mid range was over emphasized.  When the chokes were removed (with the Sylvania tubes) the sound thinned out some and we compensated with a different driver. 

I've still got a few mods to try.  Once we get a good long feel for these Ken Rad tubes there are Tantalum resistors on standby along with quite a few other driver tubes to roll. 

Overall I'm very happy with these amps and as we continue to refine the system they get better and better!

[johnsonad]

It's been a while since I updated this thread.  The system was sounding like crap.  I started with the BeePre and got it to a point where it sounded great and today I updated these amps.  I replaced the Rike Audio parafeed caps with Auricap 5uF bypassed with a V-Cap 0.1uF.  This sounded better than it did with the Rike's.  The icing on the cake was swapping the Ken Rad drivers for Tung Sol's.  This made a significant improvement in the detail and highs.  I'm happy with this sound as it stands.  I'm going to play around with smaller valued cathode bypass capacitor values and see if that does anything once I'm used to this new sound. 

[johnsonad]

A small update.  I purchased a pair of Elrog 300B tubes after reading many favorable reviews.  They haven't much time on them yet (two days) but I thought people would like to hear about them.  If you haven't read anything about them, they are not really a 300B in the technical sense but work in place of a 300B.  On Paul's recommendation, I dropped them in replacing a pair of EML 300B mesh plates (another none true 300B).  They needed a few hours to wake up but after a couple of days of listening my wife and I are most impressed by them.  Sonically, when compared to the mesh, they have a fuller mid range.  When listening to piano works, notes have a more realistic tonal range.  The decay has improved as has the spacial perspective of the sound.  They are not as holographic as the mesh plates yet but this pair is still breaking in.  They are noisier than the mesh plates.  I attempted to measure the difference this morning but I didn't get any appreciable numbers.  It's not a significant difference and this may dissipate as burn in some.

Overall I'm very pleased by the purchase.  They were expensive but if they last, they will pay for themselves in sonic improvement.

I wonder though if my amps can be better optimized for them.  My operating point is 350v P-K, -76v, 50mA, 5k.  Thoughts from PB or PJ?

[Paul Joppa]

My rule of thumb target impedance is 4858 ohms - I'd call that pretty close to 5000  :^)

Thanks for the update, will be curious to hear how they progress.

[johnsonad]

Thanks Paul! A question, in looking at the curves, do you feel that 50mA is enough? I could work it up to 60mA before needing to swap out PF chokes.

[Paul Joppa]

60mA would call for a 3700 ohm transformer. At 70mA, it wants a 3000 ohm transformer. These options will give you a bit more power, but to get REAL power from these tubes you need more voltage. They really are closely related to the 845 from which they were derived!

[johnsonad]

Thank you sir! I seem to be in an optimal area and the sound shows as much. Power isn't needed and the sound is sublime. Thank you for the reality check Paul!

[johnsonad]

A short update on the ER300B tubes.  That have been in the amps a week now with my wife getting more play time than I have.  She loves them for classical piano, strings and choral voices.  With the EML mesh plates, she wouldn't listen to the system.  Now she is playing music every day.

I've had two short listening sessions with the new tubes.  With my music, I find that they are a little thick in the mid and lower mid range if that makes sense.  The mesh plates have a certain clarity to them that the Elrog's don't.  It could be my operating point or system synergy as all the reviews I've read so far are favorable.  As they continue to break in I'll keep you updated.

[johnsonad]

Another update.  These tubes change with time!  We are both happy with them on most recordings.  The meshies sound great but these are better, more life like if you will.  It's nice having the best of both worlds!

[Gerry E.]

Another update.  These tubes change with time!  We are both happy with them on most recordings.  The meshies sound great but these are better, more life like if you will.  It's nice having the best of both worlds!

Thanks for the update Aaron!  I'm still waiting for mine.  I pre-ordered them from True Audiophile in early or mid February with delivery expected to be late February or first week of March. 

Now it's mid March and still no word on the next shipment.  That's the way it usually goes with items like this and hopefully our patience will be rewarded soon!                 

[johnsonad]

A little something that came in the mail today. They work for the BeePre so why shouldn't they help with the power amps. The Elrog tube disapated heat from the base or so it's written. So far no melted rings.

[Paul Birkeland]

The silicone rings are very likely to melt in a power amp (others have melted them); we don't recommend them in that position.