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APHEX Thermionics 1100 hotrodding
Old 22nd January 2007
Gear Nut
mas's Avatar

APHEX Thermionics 1100 hotrodding

I wonder what the differences are when using different tubes in the Aphex 1100.

Originally Posted by Levi

"I have the Aphex 1100 that I retubed with NOS tubes (the factory tubes sounded a bit "boxey" in comparison) and it's a wonderful piece. I highly recommend it."

Levi, which specific tubes did you use that sounded less boxey? Where did you get them from?

Anyone else who has tried other tubes in this preamp and made an "objective" comparison, e. g. one channel the stock tube, other channel a different tube?

I´d really appreciate if you share the experiences you´ve made!


(BTW, mine came with 6N1P tubes. The manufacturer stated that he reserves the right to ship units equipped with 6DJ8 tubes depending on availability)
Old 22nd January 2007
Gear Nut
johnnyvince's Avatar

Factory tubes always sound "boxey"! It doesn't matter what factory, or what tubes, they're just plain "boxey"! NOS is always better. More girth and more warmth!

Seriously though, I've got an 1100 that I was thinking about trying this very experiment on. In the process, I have learned (according to that internet) that the 6N1P is a fairly recent model (maybe late '80's?). All new 6N1P tubes, past and present, are from the same factory in Voskhod, Russia, and are rebranded by Sovtek, Svetlana, etc. There is also a Russian military spec version, called the 6N1P-EV, as well: tighter tolerances and longer life, so they say...but who knows: they may have been bribed. tutt

I think it might be a matter of luck wether you'd see an improvement between different 6N1P's made in the same factory. OTOH, new tubes are the audio equvalent of that "new car smell".
Old 22nd January 2007
Gear Addict
Originally Posted by johnnyvince View Post
Factory tubes always sound "boxey"! It doesn't matter what factory, or what tubes, they're just plain "boxey"! NOS is always better. More girth and more warmth! .
Of course factory tubes sound boxy, they came right out of the box!
Old 23rd January 2007
Gear Nut
mas's Avatar

Well, I didn´t mean a 6N1P from a different manufacturer or an NOS example of that tube (??? - doesn´t make any sense).
The manual says that there are a couple of other tubes that are known to work with this preamp, for example the 12AT7, 12AU7, 12AX7, 5751, ect. (see Page 8-1 ; one gets literally encouraged to do that as there is even a switch for changing the filament voltage to accommodate many tube types).
So I was wondering if someone tried some of those tubes (and I guess Levi meant one of those - would be nice if he could clarify that).

I really like this pre as it is. But in case there is a way to get even better results, it sure would be nice to know it.
Old 2nd April 2007
Lives for gear
lord_bunny's Avatar

i would also love to know what people have tried. i wouldn't mind switiching to something a little warmer than the stock tubes.
Old 2nd April 2007
Lives for gear
I must be a luddite, since I love my 1100 with the stock tubes. That's a sound I don't want to mess around with!
Old 2nd April 2007
Lives for gear
Rob King's Avatar
Originally Posted by Confusionator View Post
I must be a luddite, since I love my 1100 with the stock tubes. That's a sound I don't want to mess around with!
I agree with this as well. When I tested the preamp, I was very impressed with it and made the purchase about a month ago. I bought it because I loved the sound of it. I wouldn't change mine.
Old 20th August 2008
Gear Nut
mas's Avatar

I meanwhile settled on Telefunken ECC88 tubes. They don´t give you a "typical tube sound" (whatever that means ;-) but result in an extremely high resolved, clear, 3D sound with quite litte colouration. Way smoother and detailed than the stock tubes wich also seemed to hype the top end a little bit in a harsh way. Sounds really stunning now.

I also tried Amperex ECC88 which had more midrange meat but noticably less resolution - clearly less Hi-fi than the Telefunkens.

I know this thread is not the newest, but maybe there are still two or three people interested in this topic.

Old 8th February 2009
Lives for gear
surflounge's Avatar
An automatic servo biasing feature allows users to swap out the stock (6-volt filament) 6N1P or 6DJ8 triodes for a variety of other tubes, including 12-volt tubes that are accommodated via an internal filament voltage switch. So there's a wealth of alternate "plug-ins" available if users want to experiment with higher-distortion 12AX7/12AU7 tubes for a different sound.
The Model 1100 was designed to use Russian-made 6N1P dual-triode valves in its amplifer stages, although the more readily available American 6DJ8 version can also be used with almost identical performance — perhaps just the merest hint of increased distortion separates the two valve types. These 6N1P and 6DJ8 valves have not been widely used in audio applications, yet they exhibit very low microphony, have a rugged construction, and have low-noise characteristics which make them ideal for this application. However, other more familiar dual-triode valves can also be used, as the RPA circuit topology affords automatic servo-biasing, which not only means that it is self-compensating for small variations in valve characteristics, but also that a number of alternative types may be substituted. For example, the common 12AX7 and 12AU7 (ECC82 and ECC83) dual triodes may be used quite happily to deliver the same general performance — identical gain, frequency response and so forth — but with an increase in the distortion (roughly ten times more with the AU7 and AX7).
To facilitate valve substitution, Aphex have included an internal selection switch for either 12V or 6V heater circuits. Aphex Thermionics include in the handbook a list of ten tested types of alternative valves, as well as a list of untried but theoretically suitable designs, and suggest that the user is free to experiment with substitute valves in order to tailor the sound of the unit, changing the amount and characteristic of the valve distortion to suit personal taste. This provides the Model 1100 with high-end 'tweakability' and the facility to create your own personal sonic signature.
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