Rogue Audio Dark Upgrade.

@mulveling 

thanks for your insight on the dark upgrade.  i am on the fence about a stereo 100 basic or dark.  

@charcoalchuck agreed that Rogue is a steal at the price point.  I've had some really nice tube amps and the ST-100 rates extremely high.  Not sure its at Audio Research Ref level but pretty close IMO. Referring to older Refs and not the newest series. 

Thanks guys for some very informative information plus tube suggestions.  I have several 12au7 to try but will need to search for 12AX7 or 5751 that don't break the bank.  Or wait a little while until prices return to normal.  Hopefully.  This is definitely where I'll start before any other upgrades.  

I have run Rogue Monoblocks for over 20 years starting with the 120s that were upgraded to 150s. That jump was massive. Better amp in all areas. They also ran much cooler as the 120s were mini space heaters.

I then sold the 150s and bought a pair of 180 darks. They have a bit more "darkness" and top end detail, but the difference between the 150s and 180 darks was very subtle. The most interesting thing is to my ear, they need to warm up at least an hour before they really get going. After that hour...they are a steal at the price point.

Also want to add that Rogue has splendid customer service. Usually Mark (the owner) responds personally. Just my 2 cents 

I am totally not recommending this (lol), but I’ve run a 12BH7 sub for 12AU7 in my Apollos for several years. I also have a friend that does the same in his Zeus. It’s a much better driver tube than 12AU7 in my experience. The driver tubes in an amp are often overlooked but can make a big difference. Sometimes it feels like 1 or 2 small tubes are struggling to drive all the KT’s (especially in Apollos). If you want detail & dynamics - this is the sub.

Mark from Rogue used to "OK" me that sub for a couple of components (Apollos and Ares - very hard to find quiet 12BH7 for the latter, though), but Nick has not been friendly to it lately. The issue is 0.6 Amp heater draw per 12BH7 vs. 0.3 A per 12AU7. In context of the 1.8 A per KT120, it’s not much extra total draw (is my reasoning).

Lots of good 12AX7 and 5751, and fun rolling them in the Rogue tube amps. Lots of different tonalities / balances that will work with different systems & ears. Roughly from brightest to warmest, here’s what I liked:

Mazda silver plate 12AX7
Telefunken Ribbed Plate 12AX7
Tung-Sol 12AX7
GE 5751 TM BP "silver clips"
Amperex 12AX7
Mullard 12AX7, CV4004

Despite being on the bright side, the Mazdas are actually my favorite. They have beautiful mids along with more detail and dynamics than the other tubes. It was like a full component upgrade to my non-Dark Apollos. With Apollo Darks and now slightly brighter speakers, it’s not the best match anymore - which kills me because I love that tube. I also recall really liking the GE 5751 "silver clips" version which was only produced for a couple years in the 50s (something like 52 - 54). Both Teles are decent, and easy to find. The Mullards end up being a little warm and thick for my liking. 

I’ve also briefly tried a GE 12AY7, that worked pretty well and lowered the gain (Apollos have a LOT of gain).

The original Apollos shipped with Electro Harmonix small tubes and Electro Harmonix KT90 - the result was a bright and lean sound! KT120, and any of the aforementioned small tubes, are much better. 

@samzx12 The CBS 7729 was their low noise 12AX7 for instruments. From Brent Jesse’s page: "New Old Stock in original boxes. Low noise industrial version of the 12AX7, with heavily gold plated pins. These were made by CBS and then screened for precision laboratory or avionics (Raytheon labeled) use and sometimes sold under the Leeds & Northrop label, with their lab grade number on the tube and box. This is a nice, but very scarce, version of the 12AX7 only made by CBS. Perfect for tube microphone preamplifiers, and incredible in any other hi-fi audio application."

I left out the price cause it’s rare, thus expensive. : ) The plate seems to a standard ladder (long plate). I’m not aware of any long plate triple micas TBH, could be wrong. The CBS 7729 is a fine tube. It appears to pare well with its 12AU7 brother, the CBS 7730, but that could be my imagination, as its the driver tube in the Stereo100 that affects the sound the most.

Gakerty can you give me more specifics on the CBS 12AX7 please?  Are they triple mica 5751WA or another type? I have experience with the 12au7 CBS in a Primaluna integrated amp I used to have and really liked the CBS sound. 

I’ve been mulling whether to send in my Rogue Stereo 100 for the "dark" upgrade, but seems to really not be worth it. I already have good tubes in the ST100. After many combos having found CBS 7729 (gain) 7730 (driver) to be fantastic. More punch and equal clarity to the long plates Amperex and 7316 I had in there. I’ve also tried Telefunken 12AX7s and multiple other tubes, and to me the CBSs trump them all, once the 7729 broke in (There seemed to be some grain in treble that is gone now). That was a nice tube surprise! Rogue will charge $~1350 for the upgrade sans tubes and $1500 with their choice of Telefunken and the like. On another note, I’ve recently sent in my Rogue RP7 for upgrading to RP9 and am VERY happy about the change.

Throw some VH Audio ODAMS in that amp.

@mulveling thank you 1st and foremost with your experience and recommendations.  I have a ST-100 and wondered exactly what you brought up. Would I even like the upgraded caps. Caps probably make a big difference but which one would be preferred. Hiend2 also brings up a good point and that is to purchase caps and have a tech install but again which ones?  In addition,  shipping back and forth isn't cheap plus the possibility of damages if shipped to Rogue for the Dark Upgrade. 

NOS tubes are another recommendation but which 12AX7 are considered popular for the ST-100?  I have several 12au7 to experiment with.  I  prefer a neutral to slightly warm sound. 

Lastly, the only downside of changing caps is it could hurt resale value because some buyers do not want to purchase a modified component unless it was performed by the factory. 

Please Click                       " Capacitor Check"

In the last link for a good read

That upgrade is $$  and shipping damages are always possible not to mention $$

Id say maybe conciser Some excellent NOS Input tubes and have a tech install some Sweet Coupling caps

Good reading

Which amp, specifically? They do it on ST100, M180, Apollo, and even old Zeus.

I went from stock 2010 Apollos to 2017 Apollo Dark. To be quite honest, I feel the stock Apollo were a better value. If I could have this back, I would have stuck with the old Apollos. But everyone is different, and you will find others gushing about what the upgrade did for them.

Two caveats to my circumstances:

1. I had already rolled excellent NOS small tubes into my old Apollos. Which negates the biggest sonic upgrade from the "Dark" model (which usually comes with RCA clear tops and Telefunken smoot plates - there are better vintage tubes than this).
2. I don’t think I like the premium Mundorf EVO coupling caps that go into the Dark models (standard models use plain white M-Caps). I wish Rogue offered a couple choices of premium caps.

The best upgrade would be to move up to the next bigger amp model, culminating in the Apollo monos. It does make a difference over the M180, even if you don't need the power (I have 96dB Tannoys). Unfortunately, I think they only offer the Apollo in "Dark" form now. But Apollo and Zeus amps are a GREAT deal used, if you can deal with shipping / transport issues.

My amp became darker sounding. :)

Dark Extended Features:
- Ultra Premium coupling capacitors
- Increased power supply storage
- Hex Fred high speed diodes in power supply
- Polypropylene bypass capacitors in power supply
- Nude Vishay resistors in critical locations
- Rhodium binding posts (Cardas)
- Rhodium RCA jacks (Cardas)
- Upgraded signal wiring (Cardas)
- Telefunken and RCA small signal tubes

What is it?