Projects


DIY Turntable Single Ended Amplifier Open Baffle


Turntable Project


The base is made from walnut, 40mm (1,6 inch) thick.
I will use an AC Motor of the Thorens TD160 mkII, also the platter and platter bearing.
The table is completely solid, with holes cut, of course, for the motor, bearing, On/Off switch and arm mounting.



Building the base from walnut.


A long way to go...


I'm using the Rega RB300


First hole, the main bearing.
I used 40 mm ( 1,57 inch ) Walnut for the Turntable. It's build out of 4 piece walnut to avoid distortion. All holes are machined with high precision.
The distance of mid platter to the tone arm pivot must be exactly 222 mm ( 8,74 inch )for the used Rega RB 300 tonearm.

The used Synchronous motor is from an old Thorens TD 160 Mk II. Also the Platter is from the TD160 Mk II



After weeks of calculating and building...






The Spikes are from eBay...

Specs:
Motor: Thorens TD 160 Mk II Synchronous 230 VAC/50 Hz
Platter: Thorens TD 160 Mk II Aluminium 300 mm / 1,5 kg, Belt driven
Cartridge: Denon DL110

This turntable/tonearm combination was evaluated by 3 of my friends over the last weeks.
The TT1 is very quiet even with old and frequently played records. It further surprises by producing a stable, solid soundstage with a respectable representation of front-to-back depth on suitably recorded albums.

The 180g pressing of Cat Stevens 'Tea For The Tillerman', further shows how the bass is tight, tuneful, fast and weighty.


Next step: Extended Synchronous Motor



TYP LSR 11/16

The Audio Technika AT20 is added (October, 2014)


           

This is a legendary cartridge, considered one of the best MM designs ever made.
During its lifetime it appeared in somewhat different versions, the differences between them are primarily in the styli - with the SL or SLa having the tapered aluminium cantilever and the SS (top version made) having a beryllium cantilever.

 Frequency Range 5-50k Hz (AT20)
5-45k Hz (AT15)
 Channel Seperation @1kHz (db)   >30db AT15/20 SLa
 >33db AT15 SS
 >35db AT20 SS
 Channel Seperation @10kHz (db)   >25db AT20 SLa
  >30db AT20 SS  
 Channel Balance @ 1kHz (db)  <0.75db
 Output Voltage (mV @ 5cm/s))   2.7 mV
 Compliance, Dynamic (100Hz)  9.5 x 10-6cm/Dyne
 Stylus Type   Nude Square shank Shibata 
 Cantilever     Tapered Aluminium (SLa)
 Beryllium (SS) 
 Tracking Force Range (g)  0.75 to 1.75 
 (1.25g nominal) 
 Tracking Angle  20
 Coil DC Resistance (ohm)  500 ohm
 Weight (g)  8g
 Suggested Resistive Load  (ohm)  47k ohm
 Suggested Capacitive load  100 - 200pf
 Replacement Stylus     ATN20 SLa, ATN20 SS
 ATN15 SLa, ATN15 SS 


The Audio Technica AT20 SLa cartridge features a wide frequency response, with a smooth curve resulting in a natural and uncoloured sound, without the high frequency harshness which results from peaky response.

A major side benefit of smooth high frequency performance is decreased groove wear.


Calculate Turntable Motor / Pully

Calculate Tonearm / Cartridge Capability

Vinylengine.com The Home Of Turntables





Single Ended EL34 Amplifier




Driver Tubes: 6J8P
Rectifier Tube: 5Z3P
Power Tubes: EL34
Frequency Response: 16Hz - 22kHz -3/+0dB
THD: 0.1% @ 1kHz
Weight: 18kg


Measurements


My plan is to replace most of the resistors with Carbon resistors and the coupling capacitors with better ( MKP and oil/paper? ) caps.



Some resonances at 25kHz and above of the OT's.
I should buy beter OT's.




Distortion @ 1Watt



Amplifier Circuit (modified)



Calculate Amplifier Damping Factor

Power Supply Circuit (modified)



Calculate RC and LC Filters for Tube Power Supply


Modification


I changed all electrolytic capacitor of the power supply (47uF and 68uF) with 3 x 22uF Mundorf MKP capacitors (66uF) and 33uF.
The PreAmp Stage capacitor (47uF) will be replaced with 4 x 10uF MKP.
All other capacitors in the signal path are now (russian mil) Paper In Oil capacitors.


One capacitor to go...


Tube Upgrade


I changed the "normal" 6CA7 China tube with the execllent Shuguang Treasure 6CA7-Z

The 6CA7-Z tube's construction features gold grid wires and a new internally coated black glass bottle. This unique HPCC coating is known as High Polymer Carbon Compound glass coating and is unique for its ability to reduce stray electron emission that can otherwise reflect off the glass. Shuguang also uses their new "Super Alloy" technology. Originally applied to aviation, aerospace, and military applications, this technology has been successfully used by Shuguang to accomplish directional solidification and single crystallization. This greatly improves the ability of electron emission and electron current stability. This new Shuguang Treasure series required additional parts selection quality control processes, improved vacuum techniques and additional burn-in time and testing.

This Shuguang Treasure 6CA7-Z tube is their premium export grade and purchased direct from Shuguang in China.

Read the TNT review: Shuguang Treasure 6CA7-Z and KT66-Z - vacuum tubes





October 2012: Open Baffle


The joiner (Dennis) has build the 1,2 inch ( 30mm ) Baffle...

   

   

Looks very good, thanks Dennis!




Baffle Size: 19 x 40 inches / 48 x 100 cm

Drivers: Eminence Alpha 15A, Jordan JX92 and Audax HD13D34

Eminence Alpha 15A


  • Resonant Frequency (fs) 41Hz
  • Total Q (Qts) 1.26
  • Surface Area of Cone (Sd) 856 cm2
  • Sensitivity 97.2dB


  • Jordan JX92 Fullrange


  • Resonant Frequency (fs) 51Hz
  • Total Q (Qts) 0.56
  • Surface Area of Cone (Sd) 78.5 cm2
  • Sensitivity 85.3dB

  • Embracing a range of almost nine octaves, the JX92 offers the widest bandwidth of any single drive unit available.
    This not only provides an exceptionally smooth, high-definition, crossover-free sound quality but allows for a very diverse range of applications.


    Audax HD13D34


  • Resonant Frequency (fs) 1012Hz
  • Total Q (Qts) 1.01
  • Sensitivity 91dB

  • Companies like Spendor and Rogers have used these in studio monitors. Natural timbre strong play.
    Without ferrofluid. Solid aluminum front panel.

    Crossover: 12dB @ 200Hz Woofer, 12dB @ 400Hz Midrange and 12dB @ 8kHz Tweeter




    First Crossover Circuit

    First Crossover Measurements ( October 2012 ):



    Target Response and measured Frequency Response (Nearfield)

  • Some problems (1.6kHz, 2.5kHz and 10kHz) with the Mid-Band (JX92). That is to solve with Notchfilters.




  • Frequency Range between 1kHz and 3kHz is now (almost) ok. A Notch Filter is added to the Fullrange Driver JX92.
    The peak is reduced with 5dB.

  • Yellow Curve without Notch Filter
  • Green Curve with Notch Filter (6R8, 22u and 0m68)



  • Date: February 2013 - Crossover Simulation
  • Woofer fc: 200 Hz, Midrange fc: 200 Hz / 3700 Hz, Tweeter fc: 3700 Hz



  • Date: February 2013



    Final Crossover Circuit


    Date: May 2013 - Crossover Simulation
  • Woofer fc: 200 Hz, Midrange fc: 200 Hz / 3600 Hz, Tweeter fc: 3600 Hz
  • Impedance correction @ 200Hz and @ 13000 Hz



  • Date: May 2013