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RetroValves !!! Solid-State 12ax7 replacement.

James Freeman

I think this product deserves its own official thread.

Retrovalves are a Solid-State direct replacement of 12ax7 Vacuum Tube.

Official Distributer: http://www.jetcityamplification.com/retrovalves/
Official Wesite: http://retrovalves.com/

I emailed Roberts and got some answers.

----- Original Message -----

Hello Robert.

I am very enthusiastic about this new product, although I am quite skeptical about its performance.
I have a few technical questions about Retrovalves to understand more (and quiet my heart) and make the decision to buy few.
I have read the 3 patents and as I understood correctly the electronics are capable of WAY beyond what is being marketed.

Few questions please:
1. Are the Static Anode characteristics & Transfer characteristics curves are emulated to closely resemble a 12ax7?
2. Will the RV’s input “Screen Grid” will behave the same as a 12ax7 if driven by a large signal from the previous valve?
3. Will the Grid limiting and Plate cut-off (distortion) behaves the same as a typical 12ax7?
4. Are the electronics around the tube (in amps) that shape the sound will have the same effect (Cathode Caps, Biasing, Plate Resistor, etc...)?
5. Has there been a few revisions (tweaks) of the RV since they came? (if I buy an old one from ebay will it behave like an August 2012 one?)
6. I have read in the patent the the electronics are programmable through the filament pins, will I be able to change the RV characteristics?
7. On what actual valve the Amber RV are modeled after? (for example. Tung-Sol have less Bass and more Gain than Mullard).

Some more technical information will be a great help understanding this product and making skeptical tech people like myself make a better decision.

I found an inside pictures of the RVs and it have a great number of SMT Chips inside, it does look like a programmable DSP with HV to LV transformer.

Is this Ebay seller is an actual Authorized Dealer (I am not from US so its my only option)?

Thank you very much.

Ilya Vaisman

Roberts answer:
Hello Ilya:

Thank you for your inquiry.

RetroValves® are designed to have grid and plate characteristics that closely emulate the properties of standard glass vacuum tubes. As such, RetroValves® are designed to operate with similar drive signal levels as anticipated from standard glass vacuum tube stages, and work exceptionally well when used in conjunction with standard glass vacuum tubes. The overload (i.e., clipping) and self-biasing properties of glass vacuum tubes are reflected in the functionality of RetroValves®.

As you know, there are subtle differences between various manufacturer models of glass vacuum tubes, and these subtle differences are some of the reasons users may prefer one model over another (e.g., Tung-Sol vs Mullard). RetroValves® also have subtle characteristics that make them unique, such as an extended dynamic range over traditional glass vacuum tubes. RetroValves® are a nice additional choice to the traditional glass vacuum tube arsenal, yet maintain the native tonal characteristics of the target amplifier.

The RetroValve® design is mature, although we may make refinements to the design from time to time to extend the performance or improve produce-ability. In addition, we continue to develop intellectual property for RetroValves® including a recent patent that has been issued regarding programmability.

It is my understanding that the Ebay seller is authorized, but I recommend that you contact Jet City Amplification directly for any questions regarding marketing, sales, and distribution.

We are very excited about RetroValves® and recommend that you try some of the various models offered for yourself to get a further understanding of the benefits of these devices.

Take care,

Douglas Roberts

Roberts Audio Technologies

From his answer I think we finally have a real good SS 12ax7 replacement.

It even emulates the Transfer Characteristics of a 12ax7 (Grid & Plate behavior).

Sound-wise they should be almost indistinguishable from a 12ax7.

Its no FETRON alright.
It uses the latest and smallest SMT technology like in iPhone's and smallest transformers that can be wound only by hi-tech machines (for high voltage) etc...
Hence the cost of this product.

It also capable WAY more beyond what meets the eye.
The manufacturer can even change the small parameters like Transconductance, MU, clipping softness. etc...

Read the patents if you want to know more:

If anyone would post a review here it would be nice.



Tricky to see much through the gluepoxy. I've listened to some YouTube demos of the RVs in the past and they're pretty good. Maybe not quite as good as a real tube, for a lot more money. That's the killer.


There was a big thread about these a few years back, wasn't there? But why? A good new production 12AX7 is under $20. They last a long time. Years. Why spend $99 for 3 Retrovalves?

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