EWS!Warning! Caution! Servicing this preamplifier involves work with high voltages that can kill you. Do not attempt to adjust or modify any circuits or equipment described below without the required training, experience and safety skills when working with dangerously high voltages. It is your responsibility ( I assume none) to ensure that work on this equipment, or DIY build based on information on this web site, is safely done and will not cause life or property threat or damage!


                       ***Shiny Eyes 4P1L Preamplifier***


This a new version of the Shiny Eyes 4P1L preamplifier/line stage that includes an excellent remote controlled volume attenuator made by Khozmo ( This preamp has a deeper enclosure ( Modushop Pesante 3U at 400mm depth) to accommodate the 64 steps Khozmo attenuator. In the picture the wood sides are maple, but other wood choice are available.  The preamplifier has the same specs and can be provided with an input selector and more than one input and/or output ( comes as an additional cost). The price of this preamp, with Khozmo/Takman REY, one input and one output, is $1,950.

frontsidebackfront wiring

Here is a mini -review from the happy owner of the pre with Khozmo:

Hi Radu: 
I wanted to give you an update/mini review on my new “Shiny Eyes” line stage but I have been too busy listening to music.  Blush 
After further listening/break-in, I still find it to be super transparent and detailed but with a touch of tube warmth which is exactly what I wanted.  However, the biggest improvement over my previous LDR-based passive line stage is in dynamic impact!
I didn’t know what I was missing until I heard it.  It started with a well-known audiophile recording on CD that I never really understood what all the hype was about.  With the increase in dynamic range, not only did I “get it” for the first time, I really enjoyed this CD.
Obviously, one example wasn’t enough to establish a pattern but a couple of days later I played an SACD that I recently purchased.  It’s from one of my favorite groups but not one of my favorite albums.  The first time I played it, using my old passive line stage, I thought I had wasted my money of the SACD.  When played through the “Shiny Eyes”, I thought it was fantastic!
Again, it was that significant improvement in dynamic impact.  I know the following statement is a bit of a cliche, but the “Shiny Eyes” really is like my former LDR-based passive line stage but on steroids.  Not only is it a great component, it’s a great value as well!



I’ve started to experiment with the Russian DHT 4P1L  years ago. This design is the result as many hours of breadboarding, testing and listening. I’ve concluded that the best sound, lowest microphonic effect and highest driving capability, was offered by a 4P1L in triode mode, filament biased and line output transformer loaded.

  • This is a single stage 4P1L in triode mode using Lundahl LL1671/30mA line output transformer.
  • The maximum gain is about  x2.2 or 6.8 dB.
  • Typical THD is less than 0.1% at 1kHz and 2.2Vrms output. Usually, earlier production ( 60s and early 70s) are better sounding tubes and lower THD.
  • The frequency response is better than +/- 0.5dB @ 20Hz-30kHz.

The preamplifier is built with 2 PCBs of 2mm, 2oz Cu, one has the power supply and the other one the 4P1L preamplifier stage.

There are 3 options to buy:

  1. Two PCBs…………………………….. $125 ( shipping not included)……..10 in stock

This comes with a guide on how to build and test the preamplifier, including a BOM for easy parts procuring ( most of the parts are from Mouser Electronics). FYI for DIYers : the cost of the parts is about $575 ( $155 Mouser, $245 pair of LL1671/30mA, $35 pair of Coleman regulators, $80 tubes, sockets, mechanical, $60 CCS, resistors and last power caps).


  1. Assembled and tested PCBs…………………….$1000 ( shipping not included)….backordered, allow 2-4  weeks before ready to ship( depending on the parts availability)

In this case I will procure the parts, assembly the Coleman regulators, assembly and test the boards. I will also have the boards wired and ready to install in your proffered enclosure ( recommended enclosure is Modushop  Pesante 03PB 3U 4mm BLACK). It is your job to connect the 115/230V jumps, the signal inputs and outputs.


  1. Ready to use preamplifier………..$1,400 ( shipping not included)… back-ordered allow 3-6 weeks before ready to ship ( depending on the parts availability)

In this case you will receive a finished product. It will come in a Pesante 3U 435x300x120 mm enclosure, American cherry sides, lighted power switch, 1 output and 3 inputs switchable and Alps stereo volume control. It is possible to be wired for 120 or 230V.

There are limited options to upgrade this preamplifier. One of them is to install a different volume control of your choice ( only if there is enough room inside the enclosure). Any modifications will come with their associated extra cost.


For questions please email to

Dave posted here:, a review of this preamp built from scratch using my boards.

Upgrade volume control to TKD CP-2511 improves the resolution. Here is a try for a new front plate look:



Maxed out version of the 4P1L preamp

Another 4P1L preamp using the same excellent Lundahl LL1671/30mA line output transformers, an excellent fit to the 4P1L. This preamp was built to order. I’ve been asked to squeeze all possible sound”juice” out of the 4P1L. The power supply was upgraded to all Lundahl transformers and chokes, except the filament transformers which are custom built Heyboer 16V 2A. Both HV and LV supplies are choke input and using 4 poles Mundorf high quality caps. All connections are made with Neotech OFC  copper wire.

A nice touch are the Yamamoto loctal sockets. The only thing I don’t like about these loctals is that they lock in too hard.

Volume control is remote controlled by Khozmo. I am very pleased with the sound of this preamp. It is definetely a step up from the standard option. However, the improvement comes with a much higher cost.

It was built in a taller Modushop case to accommodate a bigger and heavier power supply. The finished preamp weights about 50lbs ( double the weight compared to the standard option). The preamp could be a good fit in a system that uses  90-96 dB  speaker sensitivity and not too high gain amps. For more sensitive systems ( for example low power tube amps and high sensitivity speakers) I definitely recommend separate power supply to increase the signal/noise ratio. This is never a perfect recipe and one must try DHT preamp before being confident that it will work in one’s system.



12 thoughts on “Products

  1. Dear Radu,
    Thank you for your so kind and accurate presentation and description.
    Your experience is precious for those who want to navigate in this ultimate-sound world.
    This is my case ans I’m currently working on a high level preamp, based on a DHT triode (maybe 4P1L), and Lundahl output transformers.
    Just to figure out the environmental system configuration, I have already built my SE 300B main amp and I’ve been pinned to the wall by the sonic performance elevation as brought by the SE configuration.
    My speakers are modified Altec VOT A5. Of course the global transparency of the whole system seems to be a pre-requisite and this is my assuption that only very agile drivers such as those having fly-like diaphragms can reproduce the additional micro-signal informations revealed by the SE technology.
    In the frame of myproject , I’m very interested in sourcing some Rod Coleman filament regulators.
    Could you be so kind to show me whom did you purchase yours from?
    Kind regards,

  2. I have ordered “Ready to use 4P1L preamplifier” a week ago, and I received it yesterday.
    I am still listening to the music from it.
    It is gorgeous. Very nice.
    I have used some tube preamplifiers – KK differential parafeed, 7 different Aikido, 01a DHT preamplifier and so on. And I also had built a preamplifier with 4P1L by myself.
    But, Radu’s is the best.
    Before order, I had asked some questions to Radu for its building or modification, and I got to know he had tried all the things I had done. This preamplifier contains his experience.
    For the sound, it’s the sound what I expected. Detailed, 3D, and less coloring.
    Furthermore, no noise and no microphonic, which is hard to solve when building a DHT preamplifier.
    Great build, Great sound. It’s just gorgeous.

  3. I have been using this preamp for a couple of weeks now. It was my first experience of building a valve preampflier. Radu was exceptionally helpful with my list of novice questions and always provided clear and concise guidance. This allowed me to finish the preamplifier build quite quickly. I never waited more than 20 mins for Radu to reply to my queries – great service.

    In my system I’ve had some nice preamps including a Shindo Aurieges and a Monbrison. This 4P1L pre is the nicest I have heard and it represents exceptional value for money.

    Hopefully news of this preamp kit will spread so that others can enjoy it. I’m looking forward to taking it along to local Hi-Fi meet ups.


    • Hi Len,
      The F5 has about 2.4Vrms input sensitivity. The 4P1l amplifies 2.2 times (7dB). The resulting input sensitivity for full 25W power will be about 1.1 Vrms.
      The 4P1L preamp has the power to drive almost everything ( low output impedance and high current drive-ability ). If the 1.1 Vrms satisfies you ( your audio sources will provide the needed output) then you’re all set.


  4. Hi Radu
    Great quality boards which l received a few days ago,now l look forward to completing the project.

  5. Hi there
    How would this preamp fit in with a Mark Levinson 27.5 power amp(solid state). Any modifications needed to be done to make it a good match?
    Input impedance: 50K ohms shunted by 1.5nF. Voltage gain: 26.9dB

    • Hello there,
      In general with DHT tube preamps the main issue is : Does the (amp + speaker) handle the mechanically induced microphonics of the DHT (4P1L)?
      In my experience, using both tube and solid state amps having an input sensitivity of 1Vrms/full power or lower, will be beneficial when using this 4P1L DHT preamp. So the answer is yes, you can use it with Mark Levinson 27.5 which has a 1.25Vrms input sensitivity.
      The preamp will comfortably drive loads down to 10kOhms and 5nF.

      • Thanks Radu… will think about upgrades I may add to order before completing it…Silly question but has to be asked…since my amp has balanced inputs and reportedly works better in XLR connection , is there a balanced version of this preamp and how much would it drive up the costs and is it really beneficial?
        Thanks and talk to you soon

      • I do not have a truly balanced version of the preamp. Yes it would be beneficial to use a truly balanced preamp if your amp is fully balanced/differential. Less noise and more dynamic.

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