The only choice for "road-rugged" touring applications!


Retrovalve® vacuum tube replacement devices are 100% analog vacuum tube replacements that offer the warm, fat, punchy sound traditionally associated only with glass vacuum tubes.

These pin-for-pin compatible direct replacement devices enhance and extend the performance of tube amplifiers of all vintages!

Enhance the sound, keep the tone, change the gain... these are just a few of the many advantages offered by Retrovalves®.

Retrovalves® are designed to emulate 12AX7 type preamp tubes, both for input and output analog functional compatibility.

What would you like to know?

The Benefits

  • User Adjustable

    RetroValves® allow the user to make custom modifications to their vacuum tube guitar amplifier without any wiring changes to the amp. The user can maintain true tube dynamics and expressiveness with enhanced gain characteristics without sacrificing performance.

  • Robust and Low Noise

    RetroValves® do not exhibit microphonic noise like a traditional glass vacuum tube and are not subject to failure mechanisms such as mechanical shock like a traditional glass vacuum tube. This makes RetroValves® an attractive replacement for professional touring applications.

  • Longevity

    RetroValves® are designed to last the life of the amplifier.

  • Lower Power

    RetroValves® dissipate much less energy than a traditional glass vacuum tube which reduces the thermal stress on the guitar amplifier electronics.

  • Mix With Vacuum Tubes

    RetroValves® work well with, or in place of, glass vacuum tubes.

For Example...

An older vintage tube amp can be modified with RetroValves® to modify the gain and/or make it more rugged for a touring application. If the user wishes to sell the amp for example and maintain its vintage value, they can just put vacuum tubes back in without having made permanent and potentially expensive wiring changes to the amplifier.

Current Models

Lower Gain (blue) Standard Gain (yellow) Higher Gain (red)

RetroValve® Specifications

Plate Voltage Range Rp = 100K 120 – 400Volts
Saturation Current B+ = 350V
Rp = 25K
8 max
Input Resistance G-Pin to C-pin
(no power)
Input Capacitance G-Pin to C-pin
(no power)
10 pF
Output Capacitance P-Pin to C-pin
(no power)
4 pF
Upper Cutoff Frequency B+ = 350V
Rp = 100K
25 KHz
B+ = 350V
Rp = 100K
Av = 40
112 dB
B+ = 350V
Rp = 100K
Vs = 500mVpp/1KHz
B+ = 350V
Rp = 100K
Vs = 500mVpp/1KHz
B+ = 350V
Rp = 100K
Vs = 500mVpp/1KHz
Vgc-cutoffB+ = 350V
See Note 2.
-4 Volts
Filament Supply RangeBetween pin 9
and pins 4,5
4.7 – 9.5Vrms
Filament Supply CurrentBetween pin 9
and pins 4,5
Vnom = 6.3V
53 mArms
Filament Supply Range Between pin 4
and pin 5
8.9 – 13.3 Vrms
Filament Supply Current Between pin 4 and
pin 5
Vnom = 12.6Vdc
160 mArms

Note 1:
SNR equals log of the power ratio: 10Log(max_output_pwr/max_noise_pwr).
Max_output_pwr = (max rms magnitude @ 1KHz)^2.
Max_noise_pwr = (rms noise power spectrum from 50Hz to 10KHz)^2.
Values are measured at 350V plate voltage.
Typical SNR: 10Log(106^2 / 250e-6^2) = 112db.

Note 2:
A typical device demonstrates approximately 65uA of plate current with
grid-to-cathode voltages less than or equal to the specified value.

Note 3:
All values are nominal unless otherwise specified.

RetroValves® VS Vacuum Tubes

Comparing RetroValves® to vacuum tubes presents an interesting situation because RetroValves® have unique transfer characteristics. You will undoubtedly have optimum tone and gain control settings on your amp for glass vacuum tubes. As you can imagine, there are also settings on your amp that you may not like with glass vacuum tubes installed. The same is true for RetroValves®… and the optimum settings for the RetroValves® may not be the same settings used for the glass vacuum tubes.

As such, rather than turning knobs back and forth on an amp, we recommend comparing the sound performance of RetroValves® to glass vacuum tubes by using two “identical” amplifiers…one optimized with glass vacuum tubes and the other optimized with RetroValves®. For all practical purposes, identical amp models should perform close enough to result in a realistic comparative test. This also allows a more “real-time” comparison since you don’t have to wait between tube replacements.


Doug has several US Patent and Trademark Office utility design patents for RetroValve® which include:

  • 7,286,060 - Indicators for vacuum tube replacement devices.
  • 7,408,401 - Vacuum tube replacement device, circuit and system.
  • 7,482,863 - Expanded performance and functions for vacuum tube replacement devices.
  • US2008/0260183 - Communication Method for Vacuum Tube Replacement Devices.

RetroValve® Replacement Procedure

The same precautions should be taken for changing RetroValves® in an amplifier as you would use for changing your stock glass vacuum tubes. Follow the steps listed in the order described below for removal and insertion.


  1. Turn OFF the amp and disconnect the AC mains.
  2. Allow the glass vacuum tubes in the amp to cool down to touch.
  3. When removing the vacuum tube, use a gentle, slight circular motion while removing the tube from the socket… be careful not to bend the pins. We recommend using a soft cloth between your fingers and the glass vacuum tube surface… this also helps to preserve the writing on older glass tube models.
  4. Observe the polarity by referencing the missing pin (the key) at the base of the vacuum tube just as the tube becomes free from the socket. You will appreciate this when it comes time to orient the new replacement tube properly.


  1. Gently set the new tube replacement into the socket with the tube oriented as it was removed.
  2. If the tube does not feel like it has mated properly with the tube socket (because the key is not aligned), DO NOT force the tube into the socket as this will damage the pins. Simply rotate the tube until the proper socket mating is established.
  3. Gently press the tube into place until it is firmly seated on the socket base.

Test Recommendation

Although the first preamp tube stage generally has the most effect on an amplifiers tone, we recommend starting with the phase-inverter tube position first when experimenting with RetroValves® for the first time. Then work backwards towards the first preamp stage (depending on how many RetroValves® you have to work with).

We have found that there can be favorable subtleties that may otherwise be overlooked if one starts out testing with the first preamp tube stage. Note: The phase-inverter socket is usually mounted closest to the power tubes. The first preamp tube socket is usually mounted closest to the input jack.

Enhance the sound, keep the tone, change the gain…
just a few of the many advantages offered by