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Friday, 18 January 2019
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  My System

"The sole objective of the audio industry as a whole is to sell products..."

The biggest issue is the recording, and it's not the signal processing, it's how it's used. I am very disappointed with the quality of the recordings of most music these days.

There are 2 basic problems:
  1. Compressors are way overused and not used properly. Most recordings have no dynamic because during the mastering phase, the recording engineer squashes the master mix with a compressor to be able to turn it up louder. This is a big NO, this makes mud at its worst yet it is done all the time. Compressors should never be used on a mix down! The compressor should be used only during the recording phase at each channel ( not the master ) to correct for things like vocal popping and multiband compressors are great tool for nailing bad frequencies the mic may pick up.
  2. The recording is made in a simulated situation- a recording studio. The best sounding audio recordings are made ( live ) in a concert hall.

Listen to Hugh Masekela's Hope!

Most recordings i hear never get the bass right. It is either not present, or it is a muddy mess. Most often the problem lies again within the improper use of a compressor, the powerful impact of the kick drum that you experience in a live concert is lost and is too mixed in with the bass instrument whatever it is.
For some reason in a lot of recordings, the bass guitar has these muddy lows that make it too woofy, they are very easy to take out. When you take out the mud you can hear the impact of the strings and it doesn't drown out the impact of the bass drum.
You know how you can literally feel the bass in live concerts regardless if it is a rock concert or a live symphony orchestra, that is the goal.

Juli 2017

Projects which are planned or in progress   Free distortion and performance analysis software that i'm using for my measurements

 Active Components

 Passive Components

Ratings are for transistors, tubes have guidelines

Musical Fidelity M1 DAC   6 Watt Single Ended EL34   SRPP Tube Pre-Amplifier   Tube Line Pre-Amplifier I Dynavox TPR-1 Tube Buffer-Amplifier Tube Phono Pre-Amp MM-Phono Pre-Amp (project) Dynavox VR 70-E Accuphase Passive Pre-Amplifier Transformer Attenuator Passive Mains Filter



Marantz CD-63 MK II KI Signature   Rega P2 RB300 Tonearm Denon DL 160 Metz DE81 Cartridge Specs. Tonearm/Cartridge Capability StepUp Transformers TML Basspipe   in-akustik Reference LS-602 Loudspeaker Cable   Bowers & Wilkins CDM 1   Syntar 200 T Jordan Horn Speaker Interconnect M550i 4PR Loudspeaker Cable PC Satellite Loudspeaker

Musical Fidelity M1 DAC

Best DAC $600 - $700, Awards 2012. A deeply musical DAC with performance and price on its side.

The M1 DAC has a pleasingly open character, one with a strong sense of dynamics and an impressive degree of insight. A solid, overtly powerful bass underpins the presentation, giving the M1 DAC's sound plenty of authority as it thumps out Kanye West's Monster.
Importantly, though, the low frequencies remain agile and tuneful.
Move up the frequency range and the Musical Fidelity's clear and expressive midrange catches the attention: it conveys the subtlety and power in Adele's Someone Like You superbly. There's plenty of detail but the DAC never becomes overly analytical.
It's always energetic and engaging, drawing the listener into the music. Pleasingly, it can also change up a gear and cruise when the music demands, too, delivering a soothing presentation.

M1DAC - Specifications


  • Jitter: <12 picoseconds peak to peak
  • THD(+ noise): <0.0025% 10Hz to 20 kHz
  • Frequency Response: +0, �1dB, 5Hz to 100 kHz


  • 1x XLR AES balanced digital input
  • 1x RCA coaxial connector SPDIF 32-192 kbps (16-24 bit stereo PCM)
  • 1x TOSLINK optical connector 32-96 kbps (16-24 bit stereo PCM)
  • 1x USB type 'B' connector for computer/PDA - 16-24 bits, 32-96 kbps (Determined by source file/computer settings)


  • 1x line level RCA (phono)
  • 1x line level XLR (balanced)


  • Dimensions - WxHxD (mm): 220 x 100 x 300
  • Weight (unpacked / packed): 3.4 kg / 4.1 kg

Tube Pre Amplifier
After 2 years is this project now finished.

The amp is more then 25 years old. I bought this peace on Ebay for nearly nothing because he did not work.

The first thing i did was drawing the schematic.
Then i started to repair this amplifier, this was'nt a big problem (all capacitors, 2 resistors, 1 switch and 2 tubes).

All capacitors are now high quality caps, as the resistors.

I bought the two 12AU7 at 2 years ago.

12UA7 low noise tube        Tube Pre Amp

This two 12AU7 are old ( 1967 ) and shit expencive, $45 each! @*#$:-(#^*@!

Next step: replace the Alps with a 24 step attenuator...

  • All inputs are switched by high quality relais (the 5 red blocks on the top side) to keep signal path as short as possible.
  • The 4 black Capacitors on the left side are for the hight voltage of the tubes. The 2 capacitores above ( the orange and the black) are for the tube heating and the relais.
  • The coupling capacitors are high voltage Solen caps.
  • I used a ALPS potentiometer (not the best solution, but for the moment it's ok)

Heater power is 24 Vdc because the heating of both tubes is in series. Normaly it should be 25.2 Vdc but i think it is beter to use a lower voltage. It's about 4.75% less.

For the high voltage i used 4 very fast diodes and a cascade resistors filters with 4 times 400uF. I also bypass each diode with a small capacitor.

Some measurements:
  • Frequency response: 10Hz-86kHz(-1dB)
  • Harmonic distortion: < 0.11% (1kHz)
  • Signal-to-Noise Ratio: < 91dB (A)

Sound: good bass, mid-range vocals more pronounced, sweet highs

Schematic Amplifier   -   Schematic Power Supply

Tube Pre Amplifier


Through the use of inferior components you get a luxurious noise generator but no high-quality tube preamp!

So, a lot of things on this PreAmplifier are modified:
The first measure is that all resistors are replaced by metal or carbon composite resistors, and especially where it is important to oversized.

The Cathodefollower is recalculated and modified and the potentiometer has be changed with an Alps "Blue Beauty".

The output capacitors (1uF) is loaded by default with only 20kOhms. That strikes me as somehow suspect, and sounds so.

Alps   Vishay Dale    Sprague Vitamine Q

Also the negative feed back is recalculated and modified.
A negative feedback should the circuit stabilize and not working like a tone control.

It is important that the circuit ground is clearly defined, as are the center tap of the filament.
The mass of chassis ground to the actual circuit ground must be made by a separate core cable (copper, 1.5 mm2), since this can lead to potential differences.

The Tubes 6N6 are still the same, because they are good.


Spectrum graph

TPR-1 Frequency Response, measured with RMAA

Spectrum graph

THD + Noise (at -3 dB FS), measured with RMAA

The results are disappointing!
So i decided to rebuild the Pre-amplifier using different tubes (12AX7).

That will be my next project....

A link to a german site about Dynavox TPR-1 tuning:

Dynavox TPR1 tuning...

SE Amplifier with EL34

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


Measurement befor Modifications

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)

Power Supply Circuit (modified)


I will change 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

Pre-Amplifier Project

My new SRPP Pre-Amplifier using the 12AU7 ( ECC82 )

The first idea was to rebuild the Tube Pre-Amplifier TPR-1.

The measurements with RMAA on the TPR-1 are disappointing!

Now i decided to build a new Pre-Amplifierusing the SRPP principe.
Because i wanted to keep the housing and power supply of the TPR-1 the best appropriate tube is the ECC 82.
The reason for SRPP amplifier was the minimum number of parts and minimal distortion (THD) of only 0.03% between 20Hz and 100kHz.
As you can see only 4 resistors and 1 capacitor is used in the signal path.
The gain is 18dB or 8 times which is enough for me.

The SRPP principle is fundamentally different from other commercially used for preamplifier circuit concepts. The originality lies above all in the push-pull circuit of the tubes having the same voltage terms in series are: Assuming an anode voltage of 150 V per tube must be so 300 V operating voltage. The negative bias is produced in almost all tube circuits through the cathode resistor. The signal voltage is supplied to the grid of the lower tube and the unbridged cathode resistance of the top tube sloping AC used - anode of the lower and control grid of the top tube are joined together - as a counter-phase control voltage for the top tube, while the voltage drop across R2 and R3, the bias of this Tube produces.

This special push-pull circuit, the output resistance of the tube by a factor of 3 to 4 is reduced, which eliminates the otherwise mandatory in tube preamp cathode follower stage with all their known negative effects on the sound. In its operation, the SRPP circuit principle is so simple.

New Schematic with Feedback and doubled Output Capacity
The feedback will reduce the gain with 4dB but the Frequencyresponse and THD will improve

Schematic of Power Supply


Frequency Response 10Hz - 100kHz ± 0.2dB

Simulation is done with B2 Spice A/D v4.2 Lite

Here you can download B2 Spice A/D v4.2 Lite

Oscilloscoop pictures of 4 basic frequencies

100Hz @ 1Volt

1kHz @ 1Volt

10kHz @ 1Volt

100kHz @ 1Volt

Measurements so far:
  • Frequency Response (Sweep sine) -0.56 @ 20Hz, -0.36 dB @ 20kHz
  • THD @ 1kHz 0.018 %
  • Steroe Crosstalk -80 dB
  • Noise Level -88.5 dBA
  • Output Impedance 2360 ohms

  • Frequency Response (Sweep sine) -0.56 @ 20Hz, -0.36 dB @ 20kHz

  • THD @ 1kHz 0.018 %

  • For the first tests and changes the amp is hardwired, later a PCB will be developed.
    The tube fitting in the middle is not used. Perhaps later for a Cathode follower.

    Recommended Reading:
    The Secret Behind the SRPP by John Broskie's Guide to Tube Circuit Analysis & Design.

    TubeCAD article, SRPP Deconstructed (PDF)

    MC 767 RD

    Tube Phono Pre Amplifier

    The MC input of this amplifier sucks!

    The amplification of the cathode stage is to low to amplify the output voltage of a Moving Coil cartridge ( about 0.5mV ) to the needed level of min. 500mV or 60dB.

    The schematic shows that only 2 components are readjusted, the 100 ohms resistor and the cathose bypass capacitor of the second stage.

    Believe me, that's not enough to get 60dB amplification!

    Some data (after modifications):
    • Vacuum Tube 1 x 12AX7, 1 x 5687, 1 x 6N6 for the PowerSupply
    • 2 x 5670 (6N3) for amplification
    • Output resistance 12 kohm
    • MM input Level 2.5 mV 47 kohm / 100pf
    • Output Level max. 2000mV
    • RIAA accuracy: < 0.55dB, 20Hz - 20kHz
    • Stereo Crosstalk (db): -65.0dB
    • Total harmonic distortion (THD): 0.29%
    The 6N6 (E182CC), 5687 and 12AX7 tubes are used in the power supply, where the 6N6 (E182CC) is responsible for rectification and the 5687 and 12AX7 are utilised for smoothing/stabilisation.

    Perhaps i will change the 6N6 (E182CC) for the EZ81 tube...

    The 5670 tube is very microphonic, so i replaced this tube with the 6N3P which is a realy good tube.

    The 6N3P tubes are used for the signal and gain stages. Both tubes compliment each other very well and produce remarkable detail and vivid vocals.

    6N3P Datasheet 6N6 Datasheet


    Original Schematic MC 767 RD of the old version (which sounds better then the new MC 767 RD)

    A lot of things on this PreAmplifier are modified:
    some resistors and capacitors are replaced, the Ouput Stage and RIAA Network is recalculated and modified.

    Here the orginal RIAA network plot:

    RIAA accuracy: > 3.0dB, 20Hz - 20kHz

    • +1.1dB at 1kHz (in place of 0.0dB)
    • -1.3dB at 2kHz (in place of -2.6dB)
    • -5.9dB at 5kHz (in place of -8.2dB)
    • -11.2dB at 10kHz (in place of -13.6dB)
    • -16.9dB at 20kHz (in place of -20dB)
    The yellow line is the output-voltage of the Pre-Amplifier.
    On this plot you can clearly see that this filter is not working as it should.

    The red line shows the network funktion...

    Simulation is done with B2 Spice A/D v4.2 Lite

    Here you can download B2 Spice A/D v4.2 Lite

    (image before modifications)

    Tube Buffer Amplifier
    My Tube Buffer Amplifier with the EF95

    Tube Buffer Amplifier
    • High input impedance - Does not offer any loading to the source CD player and as a result it gives its best possible performance.
    • Low output impedance - Drives any amplifier easily and ensures virtually perfect linearity.
    • Uses 2 EF95 tubes. Excellent technical performance, incredible longevity - great sound.
    • Low noise, low distortion, huge overload margin and wide bandwidth - Extremely clean sound with huge dynamic range.
    This Tube Buffer Amplifier is now used between the Tube-Phono-Preamplifier (MC 767) and the Tube-Preamplifier (TPR-1).
    It's a simple Cathode Follower with high Input Impendance and low Output Impedance.


    • Tube: EF95
    • Amplification: none
    • Output impedance: 300ohms
    • Frequency response: 10Hz-90kHz(-3dB)
    • Noise Level (dBA): < 75.6dB (A)
    • Total harmonic distortion (THD): < 0.015% (1kHz)
    • Stereo Crosstalk (dB): -71.5dB
    • Length 250mm x Depth 185mm x Height 210mm
    • Weight: 3.2 kg

    Accuphase E204

    One of the best...

    I bought this amplifier secondhand, 5 years ago. It's still one of the best for the money.

    But i was alltime interessted in Tube amplifiers, so i bought a secondhand Dynavox VR 70-E.
    Shure you can't compare Dynavox with Accuphase....

    But the possibility to modify my amplifier is for me very important and there is nothing to modify on a Accuphase but a lot on the VR 70E (made in China for no money...)

    Power output: 90 Watt per channel RMS at 4 ohms
    65 Watt per channel RMS at 8 ohms
    Distortion: both channels driven 20-20kHz
    0,02% at 4 ohms
    0,01% at 8 ohms
    Damping Factor: 80, 8 ohm load at 50 Hz
    Output load impedance: 4 - 16 ohms
    Frequency response: 20 Hz to 20.000 Hz: +0; -0,2 dB
    1 Hz to 300.000 Hz: +0; - 3.0 dB

    Dynavox VR 70-E

    I switched....
    From Transssssistor to Tubes.

    I know, it's not the best tube amplifier, but i have a limited budget and i like to modify my equipment.
    The VR 70-E is ideal to upgrade (tubes, capacitor, resistors..)
    The design is straight and even for starters not to difficult to understand :-)

    RightMark Audio Analyzer Measurements

    Frequency Response (swept sine) = +0.1dB, -1.2dB

    Total harmonic distortion (THD), = 0.015%

    Read full RightMark Audio Analyzer Report of the Dynavox VR70e measurement ( opens in a new window )


    Schematic (Amplifier)

    Schematic (Power supply orginal)

    Schematic (Power supply optimized)

    Detail images:

    Image before modification

    Image after modification

    All important capacitors are changed to high quality capacitors
    ( Black Gate & Clarity Caps ).

    The input capacitor ( 0.1uF ) is gone, because it's not necessary.

    The original Potentiometer is now disconnected, it's useless with a Preamplifier..

    The recifier diodes are changed to Fast Recoery diodes.

    I also changed the input tubes ( 6F2 ) against the NOS ECF82 and the China Pentodes
    against JJ EL34 tubes.

    Last update ( september 2007 )