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RFT EZ81 rectifiers opening up! (Read 6067 times)
Fireblade
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Re: RFT EZ81 rectifiers opening up!
Reply #15 - 12/30/12 at 00:56:51
 
Thanks, Lon, and happy new year to you too!
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Fireblade
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Re: RFT EZ81 rectifiers opening up!
Reply #16 - 01/15/13 at 00:40:44
 
After an involuntary pause, I finally was able to cook the stash of tubes on hand and I can relate initial impressions (not complete nor definitive yet):

Even though I switched every tube on my complement set with new and differently specd ones, the out of box sound was surprisingly pleasant!

Switched OA3 for OD3, EZ-81 for EZ-80, JJ 6V6 S for Russian black 6V6, RCA 5963 for Brimar 12AT7.

After some 25 hours of music playing, I'm getting into some preliminary conclusions.  For example, I prefer the OD3 to the OA3, as even though the former has less bass, the latter darkens the sound with too much of it in my system.  The OD3 makes the sound more transparent.

I also seem to prefer the EZ-81 to the EZ-80, although it is probably too early to make final conclusions on this one.  The EZ-81 gives it more 'meat' and texture, I believe.

I still need to wait for the Brimar drivers to be really settled, which may occur in about another 25 hours.  This of course is the pivot of the whole set, and it may project more differences in the end.

I also have not tried the current production Tung-Sol 6V6GT, that Les seems to prefer.  Once the whole current set is settled, I'll try those for a long while and then will start to define end conclusions about the ideal set for my particular system.

So far, though, I really love what I'm listening to, in spite of the still raw nature of the complement on test.  The slight dark/warm sound has basically gone, and now I'm starting to get a more articulate, palpable and transparent sound, that evidently is still not rounded or fine-tuned given the relatively early stage of collective burn.
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Fireblade
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Lowering gain in the M-T through OA2 (VR150) input reg
Reply #17 - 01/15/13 at 12:01:39
 
Hi! I'm wondering if any Mini Torii owner has tried to compensate the increased gain of a preferred 12AT7 driver (instead of the ubiquitous 12Au7), by replacing the OC2 (VR75) input stage voltage regulator with a OA2 (VR150)?

The Mini Torii is already a high-gain amp, and when using 12AT7 or higher gain drivers, the volume range becomes too restricted.  I know the OA2 (instead of the ubiquitous OC2) will reduce the input gain, so this may compensate for the 12AT7 choice.

I know these (OA2) tubes are really cheap (i.e. Brent Jessee's $4.00 a piece).  Any caveats?
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« Last Edit: 01/15/13 at 12:02:57 by Fireblade »  

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Les Lammers
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Re: RFT EZ81 rectifiers opening up!
Reply #18 - 01/15/13 at 23:19:24
 
I have 0A2's and am not sure they effect the gain that much. The thing to do is try them and see what you think.  ;)

Keep us posted and have fun!
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« Last Edit: 01/15/13 at 23:24:30 by Les Lammers »  
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Fireblade
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Re: RFT EZ81 rectifiers opening up!
Reply #19 - 01/15/13 at 23:26:40
 
Good to know it works in your case, although I'm surprised it doesn't show gain reductions.  I've been wondering how these may sound, so I'll need to try them too.
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Fireblade
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OA3 vs OD3 vs OC3
Reply #20 - 01/19/13 at 15:12:27
 
Continuing with my rolling experiment, I've finally got rid of that warmish sound by replacing the OA3 with OD3's.  I now believe the OC3 may be the ideal balance between the deep bass from OA3's and detail retrieval from the OD3's.  The OD3's in my current set is a little 'in yer face,' so trying the OC3 may be worth it.

The 12AT7 Brimars continue to sporadically unsettle the sound, in spite of 40 hrs of burning already, although I feel they are slowly but irreversibly coming around.

Tried the Russian NOS black glass (reflector plant) 6V6's with general success, although I think they're still not completely burned in yet, as there's some slightly metallic edginess to them in some passages.  These are more forward than the more laid back (original) JJ 6V6 S's, which by now seem dull in comparison.

The current production Tung-Sol 6V6GT's are more neutral and rich sounding, seemed to have settled quite fast and to me are the ideal balance between the former two.  If the Russian NOS's settle further and that sporadic edginess goes away, I think I'll use the Russians with Jazzy/High PRAT music and the Tung-Sol's with everything else.

I'll conclude on my findings in about another 15 burning hours or so.

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Lon
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Re: RFT EZ81 rectifiers opening up!
Reply #21 - 01/19/13 at 16:00:24
 
Dave so happy you are experiencing better sound! Your MT is seasoning well too, it always amazes me how these amps just get better and better sounding. I've had input tubes that took about five to ten times longer than 40 hours to "settle in"--I bet those Brimars will really blossom with more time.

I'm experiencing a new sonic high right now due to a new additional excellent rack and all the isolation excellence (and convenience and beauty) that has added. I think we seek a different sort of "signature sound" (even an OB3 is way too lean and thin for my Torii's sound, maybe that's the difference in the circuitry as well) but I'm glad we're firmly on the road! I am trying to tell myself "leave everything just as it is!" Sometimes I heed myself. . . .:)
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« Last Edit: 01/19/13 at 16:02:27 by Lon »  

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Fireblade
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Re: RFT EZ81 rectifiers opening up!
Reply #22 - 01/20/13 at 01:46:20
 
Hey Lon, congrats on your new Mapleshade furniture.  You've been lusting after this rack for some time now, good for you! Now you have the complete sets you wanted, plus the added sonic benefits.

It's amazing indeed how much better the Mini Torii can sound once you start dialing-in the right tubes to suit for particular conditions.  In my case, I get significantly more detail retrieval and transparency now, something I did not believe possible a few weeks ago.  I need to thank Les Lammers for his right-on inputs in this topic.

You may be right about the burning times involved, as these 12AT7 Brimars are coming around, but very slowly.  In any case, the sound has improved so much now I don't mind waiting indefinitely while I enjoy the music.

I think the combination of DM945's and OA3's in the Mini may not be ideal, as those speakers tend towards the warm side of the spectrum, and the OA3's have a powerful low-frequency presence in the Mini.  In my opinion, some sound details were lost behind the low frequency wave generated in the heavier bass passages, rendering the sound too dark to discern those details.

One can go to the extremes (from OA3 to OD3) and still get a much preferred result, as I am enjoying.  This is why I guess an OC3 may be just the ticket for the ideal tradeoff there, although I'm not at all in a hurry to try it, as the sound now is just better than ever.

I reckon it is true also, as you point out, that these amplifiers are constantly improving with age.  I know mine keeps doing so.  After all, it is just 8 months old and I guess prone to get even better over time.  By the time my Mini yields its best sound plateau, the final tube complement selection in my Mini will also be quite settled, and I expect a definitely synergistic higher sonic level then.

It's been so much fun, I don't care tube rolling and critically listening for a bit longer now, as the results seem really worth it.   Wink
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« Last Edit: 01/20/13 at 12:22:17 by Fireblade »  

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Fireblade
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Re: RFT EZ81 rectifiers opening up!
Reply #23 - 01/20/13 at 14:38:32
 
I'm curious to know: Are there any Mini-Torii owners who have really successfully used any of the many 6V6 alternatives (i.e., 6Y6, 6K6, 6L6, etc.), and actually prefer them over their favorite 6V6? Is there any real advantage in using these alternatives over the original 6V6's?  Thanks!
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Les Lammers
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Re: RFT EZ81 rectifiers opening up!
Reply #24 - 01/20/13 at 16:28:09
 
I got a pair of Hytron 6K6's and like them. I decided *I* don't care for 6L6's in the Mini. Just personal preference.
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Fireblade
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Re: RFT EZ81 rectifiers opening up!
Reply #25 - 01/20/13 at 22:20:37
 
Great, Les, thanks.  

Can you give us a hint as to the sound effect the 6K6's produce in your setting?  Do you prefer them over your best choice 6V6s, other things being equal? Any particular music context where you feel these are a better choice?

I'm sorry, but I couldn't help wondering about other potential fine-tuning avenues.  ::)
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Lon
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Re: RFT EZ81 rectifiers opening up!
Reply #26 - 01/20/13 at 23:22:13
 
David, you could also try rolling the voltage regulation tube for the input tubes. I find a marked difference between Raytheon and RCA examples I have: the former is significantly more "lush" or "blooms more" than the latter.
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Fireblade
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Re: RFT EZ81 rectifiers opening up!
Reply #27 - 01/20/13 at 23:52:11
 
Right, Lon.  Actually, I think the OC2 (VR75, stock) input voltage regulator is fine, but I'm interested in the VR150 version (OA2), as it may also reduce the gain relative to the VR75, and with my 12AT7's that would be welcome.

I can't go as far as anticipating the differences between brands of the same spec regulator as you do, so that may be another variable to consider, thanks.

In general, though, I don't intend to spend my time rolling tubes for much longer, just enough to feel comfortable with the sound achieved, and so far I'm almost there, I think.  I may be missing some potential, but there are surely diminishing returns to get there by now.

Except for the Brimar drivers (12AT7) not settling yet, things are sounding quite good.  I came back to the RFT EZ-80 rectifiers and now I find them more neutral and prefer their contributions over the EZ-81 (an excellent rectifier also), go figure!

I think in the future I'll be interested in rolling a few more promising choices, but for this first stage, I'm almost done (OA2 & OC3 may be included now.)  
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« Last Edit: 01/20/13 at 23:55:26 by Fireblade »  

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Fireblade
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Re: RFT EZ81 rectifiers opening up!
Reply #28 - 02/06/13 at 01:50:44
 
As a follow-up on my Mini-Torii tube-rolling findings, I've found that I can now safely get back to the OA3's, once the Brimar 12AT7's have finally started to settle in.

The outcome is important, since all my earlier issues of slight warmth and slight lack of detail retrieval have started to vanish, to the point I no longer need the OD3 regulator to clear things up.

It is true that the OA3's sound the best in that position, provided the driver can control it, at least in my particular setup. The OD3's are a quick fix when you have not found a synergistic driver that can control the OA3's strong bass manipulation.

OD3's are too much 'in your face' and deprive the overall sound from some texture and body, rendering a less palpable, flatter sound. The combination of OA3's and Brimar 12AT7's is excellent, provided the Brimars are settled (the journey to have these 'ready' is painful and exasperating, but worth it!)

This condition now makes trying OB3 or OC3 purely optional, since the sound now is great with the OA3. I was never able to achieve this with the stock 5963's, an otherwise smooth, good overall driver, which in my setup, unfortunately, could not control the powerful OA3's 'warming' effect.

I keep the EZ-80 rectifier over the stock EZ-81 as per reasons stated in an earlier post. The only other change in the tube complement is the replacement of the stock JJ 6V6 S with the reissue Tung-Sol 6V6GT, a great current production output tube.

I'm going to cook the Brimars a little longer with this set of tubes and then I'll give the Russian Reflektor black glass 6V6's another try. I like this Russian output tube, but have not been able to eliminate its rough edges, especially in higher frequency peak passages. Part of the blame may lie on the Brimars not having been settled at the time. The Russian 6V6's are also quite slow in getting run-in.

Eventually, I may need a different driver to control the Reflektor 6V6, so I'm looking for something like the Amperex 7062, as suggested by Gotog from this forum. These are well reviewed tubes, which are also inexpensive.

I'll report the final results soon.
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« Last Edit: 02/06/13 at 01:52:49 by Fireblade »  

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Lon
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Re: RFT EZ81 rectifiers opening up!
Reply #29 - 02/06/13 at 03:35:15
 
Isn't tube rolling a fascinating experience? Transistor amps have many advantages and some are spectacular (but never one that I found that wasn't pretty expensive). Still, you can't alter the sound of those, tailor or ameliorate, the way you can a resolving tube component as fine and revealing as a Decware one or another of that quality.
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