Shiny Eyes SE 300B

front closeuptopThis amp was born because I wanted to re-purpose the awesome output transformers Monoliths Etude -1 used in the PSE 4P1L. The Monoliths were a little overkill for the PSE 4P1L amplifier.

I also used the interstage transformers LL1692As because they were the best fit for the chosen driver C3g.

In addition the Monoliths and the Lundahl interstage were already broken in for about 600 hours. This made possible to built an amp that reproduces music at highest performance out of the box. What better incentives for the desire to built a new tube amplifier.

From the beginning, I chose a very compact layout design, based on my previous experience with PSE 4P1L. I used the beautiful looking Brazilian cheery wood 6″ wide. This allowed an inside height of about 5″ which was excellent because I was able to fit the power supply on the bottom of the enclosure. The  case design is similar to other amps and preamps: a 1/8″ aluminum top plate where all the components and sub-assemblies are attached to, a wooden enclosure  routed in such a manner that the top plate is sitting nicely on it.

Here are few things about the design:

  • The power supply uses for the high voltage a 300W Lundahl LL1651 with 500V secondary feeding on a hybrid bridge 6CJ3 – SiC schottky, choke input PRC-1 at 5.5H/230mA, followed by CLC ( 200uF-5.5H-200uF). This delivers about 400V @ 180mA. Layout with PRC1 and tubes on top and LL1651 and caps on bottom. The LL1651 provides also AC filament for the two tube rectifiers and for the two drivers. The 300B filaments are powered on DC voltage provided by a Antek 100VA/ 2x9V, raw dc supply and superb Coleman regulators. In order to protect and extend the life of the 300Bs, I used a delayed timer for the high voltage. When the amp is turned on, first the filaments of the 300Bs are powered and the delayed timer starts counting. After about 30 seconds, the relay powers the LL1651 and the tube rectifiers allow a soft start after another 20 seconds or so.
  • The main amplifier has a simple schematics: 300B with 1K/12W-220uF/100V cathode(self) bias, driver C3G with 200ohms – 2200uF Cerafine for cathode bias. The driver feeding the IT that has a CCS( constant current source) from the PSU(power supply unit). CCS is adjusted at 16-18 mA. The 300Bs are running at about 65-68mA and 340V Uak and deliver a maximum of 7Watts per channel.

Shiny Eyes SE 300B features:

  • Custom tube PX300B Genalex Gold Lion
  • Monolith Etude-1, high end output transformers
  • Amazingly linear German made (Siemens) C3g driver
  • Lundahl LL1692A, high end interstage transformers
  • Lundahl main power transformer LL1651
  • Choke input with tube rectifiers
  • MKP high voltage capacitors
  • Coleman filament regulators
  • delayed and soft start
  • Cardas binding posts
  • RCA Neutrik
  • switches to mute the speakers

 

Shiny Eyes SE 300B measurements:

THDTHD FFT

FR

FR at 3W

THD % Output Vrms Output power Wrms
1.22 2.89 1
1.73 4 2
2.18 4.9 3
3 6.11 4.66
3.35 6.52 5.3
4 7.5 7

 

Gain:

x6.52 or 16.3dB

Input sensitivity:

  • 440mVrms for 1W output on 8 ohms resistive
  • 1.15Vrms for 7W output on 8 ohms resistive

Frequency response:

20Hz at +0.5 db to 20kHz at -0.84dB for 3 W output

 

Distortions versus frequency:Harmonics distortion versus frequency

Harmonics distortions Zoomed on lower end.

Harmonics distortion versus frequency-expanded LF

Other pictures:

top closeup

 

The sound of this amp is astounding: very tight bass, extremely sweet and vibrant mids and highs. It makes a very good match for high sensitivity full range drivers. I am using it with the Alpair 12P in small reflex enclosure. This amp is a better match to the 92dB sensitivity speakers compared to the PSE 4P1L.

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12 thoughts on “Shiny Eyes SE 300B

    • Hi Miguel,
      My choice for the DC link caps was mostly because I needed a compact layout. I would say that the oil or film-oil ( most of time I’m using Obbligato film-oil) gives a more pleasant, relaxed sound. However, I would use again the Vishays if needed as they are sort of neutral and Compact.
      Cheers,
      Radu

    • Hi Miguel,
      I see no problem. Strapped as a triode the C3m has only half of C3g gain. I’ve never tried it as a pentode, where the gain is 78 and distortions are very low. I am not a fan of very high input sensitivity amps, so I stay with the triode connection.
      Best,
      Radu

      • My new DAC can give 4V output… with C3M triode straped with Mu 20.. could work?? what do you think

  1. Hi, I would be very interested to have the schematic for the driver c3g for 300B. I currently have a design with SV83 / 6N1P, but I have a stock of c3g and would like to use them.

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