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EQUIPMENT FORUMS >> MINI TORII >> Tube Rolling Final Step? Replace the OC2 for a OA2
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Message started by P K on 01/12/14 at 15:37:48

Title: Tube Rolling Final Step? Replace the OC2 for a OA2
Post by P K on 01/12/14 at 15:37:48

I now wish to try a Mullard OA2WA/CV4100/CV1832/150C2 or a RCA OA2 to replace the OC2 in my Mini Torii MK II.

I am happy with my VA 350b replacing the stock TS 6v6gts.

Any advice would be appreciated.

I am still trying to add some mellow, smooth, less edgy, or more of a tube sound to my Mini Torii.

Any thoughts on tube rolling the OA3 in the Mini Torii as part of the "Final Step"

I hoping to start soon to sit back and just enjoy the music.

Thanks,

Peter

Title: Re: Tube Rolling Final Step? Replace the OC2 for a OA2
Post by seikosha on 01/12/14 at 19:41:00

I found it interesting that you are looking for a smoother more mellow sound with your mini. Of all the amps I own, my mini is by far the most tubey and if anything I wish it had a more airy and open sound to it. What other components are in your system?

Title: Re: Tube Rolling Final Step? Replace the OC2 for a OA2
Post by P K on 01/12/14 at 20:24:19

The 350b tubes makes Mini Torii very airy.

I find I need to have the Mini Torii on the max. neg. feedback (or sometimes the next lower neg. feedback) for it not to be too edgy,

Tube Set up:

FINAL RESULTS AFTER TRYING OUT A BRENT JESSE RCA 6V6G ST, COKE BOTTLE:

Valve Art 350B-coke bottle,blows away the RCA 6V6G ST in my system (mini Torii driving a mid/tweeter at 1000 hz and above)

Amperex NOS EZ80 from Brent Jesse (white lettering with a cartoon of a tube playing a trumpet - Bugle Boy)

RCA NOS Long Black Plates, Old Style White lettering, 12au7 from Brent Jesse.

This is a great combo, 3d deep sound stage, not too hot or bright, airy sound, great definition of instruments, sound stage that is wider than my speakers, balance natural sound.

My System:

Upgraded Linn LP12

Hadcock 242 Tonearm with a Grado Statement Reference1 Wood Body Phono Cartridge.

Vacuum State JLTI Phono preamp (one of the best phono preamps available for under $5k)

Aesthetix Saturn line preamplifier with upgraded Mullard 12ax7 and Amperex Mini Watt SQ 6922 tubes (a great preamp)

Feeding a highly modified custom Behringer DCX2496 two channel digital crossover.

Feeding the Mini Torii for above 1000 hz to a Emerald Physics CS2 mid/tweeter (Selenium D220Ti 1" Titanium Horn Driver 8 Ohm).

Below 1000 hz, a Sunfire amp is being used into dual 15 inch open baffle woofers

Title: Re: Tube Rolling Final Step? Replace the OC2 for a OA2
Post by hifitubes on 01/13/14 at 06:11:18

E80CC / 7062 for the the 12AU7 is a must before anything else. Input tube is very important.

These are interesting - I have something similar: http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&item=200977935226&item=200977935226&vectorid=229466

And some OA2:

http://www.upscaleaudio.com/products/RCA-OA2.html

Title: Re: Tube Rolling Final Step? Replace the OC2 for a OA2
Post by P K on 01/13/14 at 14:51:58

The OD3 Coke bottle tubes may not fit next to my very big and wide VA 350b tubes.

I did find some straight bottle on ebay:

RCA OD3A Tubes, I hope these are as good $11.00 for the pair.

I also purchased some Mullard OA2 tubes for $11.00 each, I hope these are better than the RCA tubes.

I have a pair of Amperex 7062 tubes, however I find the special blackplates, white label, RCA 12au7 tubes I recently purchased to sound better (if you compare the RCAs to the stock JJ 12au7, there is a huge difference in sound quality.

Maybe you could suggest a different 6092 tube for me to try?

Thanks for the comments.

Title: Re: Tube Rolling Final Step? Replace the OC2 for a OA2
Post by grinnell on 01/13/14 at 16:06:46

i tried some GE OB3 instead of the stock OA3, didnt hear a big sound difference but i liked the purple/blue glow it added.

have 2 extra tubes these are coke bottles though

Title: Re: Tube Rolling Final Step? Replace the OC2 for a OA2
Post by P K on 01/23/14 at 20:04:40

The Mullard OA2WA/CV4100 arrived today from the NOS Tube Store in Turkey.

The price was $11.00 per pair plus $10.00 for shipping (packed very nicely).

This is a great sounding tube (darker and crisper than the stock Raytheon OC2). Further the MT is much more quiet, low level passages rise above the noise of the tubes with the Mullard OA2WA /CV4100 tubes in place.
Not edgy or bright sounding.

The OA2WA /CV4100 tube rolling has a much bigger impact than what I was expecting and for the price is a must try.

The next step is to try a:

NOS OC3A (RCA)

and then a

NOS OD3A (RCA)

to replace the stock OA3

Title: Re: Tube Rolling Final Step? Replace the OC2 for a OA2
Post by Fireblade on 01/26/14 at 15:43:08

Has anyone got really good results using a reasonably affordable 12AU7 driver in the Mini-Torii?

I'm under the impression that in my system a somewhat higher gain spec (but not as high as the 12AT7's) is ideal (i.e., 7062, 6414, etc.)

But, I'm willing to try the originally intended 12au7 spec if people have noticed significant improvements with a specific NOS over the stock new production 12au7's.

Title: Re: Tube Rolling Final Step? Replace the OC2 for a OA2
Post by grinnell on 01/26/14 at 21:44:45

using RCA blackplate 6414 with good results

had some philips ecc81 in there not a huge difference

Title: Re: Tube Rolling Final Step? Replace the OC2 for a OA2
Post by Fireblade on 01/26/14 at 23:31:20

Thanks. My next purchase will include the 6414 from Jessee's but I saw RCA 12AU7 black plates at a reasonable price there, so I was wondering.

Title: Re: Tube Rolling Final Step? Replace the OC2 for a OA2
Post by P K on 01/27/14 at 19:15:35

I have a pair of AMPEREX 7062 for sale at $25.00 (used in a Mini Torii to replace a 12au7 with great results, see forums)

Let me Know.

Peter

Title: Re: Tube Rolling Final Step? Replace the OC2 for a OA2
Post by mark58 on 01/27/14 at 22:18:24

Peter, are you sure a 12AU7 can be replaced with a 7062? When I was looking for 12AU7 options for my ZP3, I don't recall this being an option. Maybe you mean 12AT7? Mark.

Title: Re: Tube Rolling Final Step? Replace the OC2 for a OA2
Post by Fireblade on 01/27/14 at 22:33:23

Mark, the 12AT7, which I've used as my first choice on the Mini for a long while, is perfectly acceptable, and yet it is even more out of spec than the intermediate 7062 for this application. I'm assuming it will work the same with the ZP3 if it can already accept the 12AT7.

I already enjoy the 7062's very much when paired with 6V6 G ST's (Coke shape), so I want to try what would probably be a side step change with the 6414's, but who knows, it may even surprise me.

The 12 AT7's are great with darker (warmer), more dense sounding tubes like the Russian Reflektor Plant 6V6's. Otherwise, the typical 6V6 tube tends to be overdriven by these drivers, becoming sibilant or worse.

I have yet to try an RCA black plate 12AU7, as these are supposed to be really good and after all the amp was originally voiced with these 12AU7's.

My $0.02 (YMMV)

Title: Re: Tube Rolling Final Step? Replace the OC2 for a OA2
Post by mark58 on 01/27/14 at 23:05:00

Fireblade, after I posted my question, I realized it was in the Mini Torii thread. The only Amp that I have that uses a 12AU7 is the ZP3 and I'm not sure I should use the tube you guys were speaking of as a replacement. In my ZP3 in the 12AU7 spot I really like RCA Black Plates both 12AU7 and 5814A which is currently in the ZP3...the below are some I've used. They were all cheap. I would recommend giving them a try. I like the old RCA Black Plates better than the RCA Clear Tops and Amprex 12AU7 I've also tried....they're warmer in the ZP3. I think the RCA long black plate 12AU7 is better (the last one) than the RCA short plate 5814A. Mark.

RCA 12AU7 TIGHTLY MATCH PAIR ECC82 LONG PLATE SQUARE GETR FOR CONN VINTAGE 1959... a pair cost $12 on ebay

Strong 1962 RCA Short Black Plate O Getter JRC-5814A Tube w Mica Support Rods this one cost $14.50 on ebay

Strong RCA Long Black Plate True D Getter 12AU7 / ECC82 Tube cost $14 on ebay

Title: Re: Tube Rolling Final Step? Replace the OC2 for a OA2
Post by Fireblade on 01/27/14 at 23:29:19

Ok, I thought you already had some reference as to the 12AT7 in the ZP3. In this case though, I'd ask Steve just to be on the safe side.

If anything, the risk would be less with an intermediate 7062/6414 than with the full gain 12AT7, but I have no experience in anything other than the Mini.

Thanks for the tips on the drivers. I will eventually try those 12AU7 black plates too, as now they also seem affordable at Jessee's.

Title: Re: Tube Rolling Final Step? Replace the OC2 for a OA2
Post by P K on 01/30/14 at 22:17:41

Final Results:

A Mullard OC2 for a OA2 is a big improvement.

A NOS RCA OC3 for a stock OA3 is a very slight improvement.

Time to just listen to the music.

P K

Tube Set up:

FINAL RESULTS AFTER TRYING OUT A BRENT JESSE RCA 6V6G ST, COKE BOTTLE:

Valve Art 350B-coke bottle,blows away the RCA 6V6G ST in my system (mini Torii driving a mid/tweeter at 1000 hz and above)

Amperex NOS EZ80 from Brent Jesse (white lettering with a cartoon of a tube playing a trumpet - Bugle Boy)

Valvo/Mullard NOS Blackburn 12au7 (the Mullard's allow the Neg. feedback on the Mini Torii to be turned down by one notch, the other 12au7s I tried needed the max. neg. feedback setting. Even with the Mullards12au7s I use the highest neg. feedback setting for Digital Playback (thus the Mullard 12au7s create a more flexible system).

This is a great combo, 3d deep sound stage, not too hot or bright, airy sound, great definition of instruments, sound stage that is wider than my speakers, balance natural sound.

My System:

Upgraded Linn LP12

Hadcock 242 Tonearm with a Grado Statement Reference1 Wood Body Phono Cartridge.

Vacuum State JLTI Phono preamp (one of the best phono preamps available for under $5k)

Aesthetix Saturn line preamplifier with upgraded Mullard 12ax7 and Amperex Mini Watt SQ 6922 tubes (a great preamp)

Feeding a highly modified custom Behringer DCX2496 two channel digital crossover.

Feeding the Mini Torii for above 1000 hz to a Emerald Physics CS2 mid/tweeter (Selenium D220Ti 1" Titanium Horn Driver 8 Ohm).

Below 1000 hz, a Sunfire amp is being used into dual 15 inch open baffle woofers