Tube circuits schematics

Today I put schematics of all tube stuff that I have presented on my website. All circuits are checked and tested. Enjoy and have fun in evaluating. Order of bare PCB is possible via email or http://www.muzgaudio.com

Dzisiaj zamieściłem schematy do wszystkich lampowych układów prezentowanych na mojej stronie. Wszystkie układy zostały zbudowane i sprawdzone. Życzę dużo zabawy w budowaniu tych układów. Istnieje także możliwość zamówienia pustej płytki PCB poprzez email lub stronę http://www.muzgaudio.com.

Pozdrawiam,

Konrad

DAC na PCM1794A + DIX9211 Made in Poland

I start a topic concerning my new project that is DAC based on PCM1794A chips. On chips because it may be built either on two or one PCM1794 chip what is configurated by appropiate set of elements (more details on schematic).

Schematics: PCM1794_DIX9211_DAC_V10

As a S/PDIF receiver and I2S switch I used relatively not well known DIX9211 chip. Its main advantages are twelve S/PDIF inputs, support for all formats ranging till 192kHz, a possibility of connecting to three additional 12S signal sources (it may also allow DSD format) and controlling via I2C. DAC also has a space for amanero module with its own power supply and galvanic isolation ISO7640.

Module’s inputs are:

• USB via amanero or similar
• 2x Coax
• Toslink
• AES/EBU
• inner iput I2S e.g. for bluetooth module

DAC is controlled by microcontroller STM32F100RBT6B. STM32F100RBT6B has big amount of periphery that allow to expanse DAC, a lot of GPIO and 128kB of flash memory and that all is well-priced. Additional simplification which is Cube makes there is no other choice. Encoder was planned to be responsible for controlling. Active input indication via separate PCB with OLED on SPI display or 8 LEDs on 74HC595. There is possibility to control via remote control or UART. Updates are made via UART. To PCB programming ST-Link V2 is needed. It is available on each Discovery STM32 module.

Power supplying is extended. I divide it on three sections, each supplied from separate transformer winding.

• USB interface power supply
• PCM + DIX + STM digital section power supply
• PCM analogue section power supply

Each section is built in similar way:

Rectifier -> big snap capacitor -> discrete pre-regulator (V1.2) -> post-regulator

Post- regulators may be chosen between LT1763 and discrete module. Additionally, I put LC filters in digital sections. Thanks to that they are better separated. Digital module contain 10 voltage regulators. In MONO mode (one PCM1794 for canal?) there is possibility to supply the chip from different regulators (4pcs,) or mounting jumper and using only two – one for digital and one for analogue.

The whole construction I divide on two different modules – digital PCB with DAC chips (150x120mm) and totally symmetrical analogue module with the same dimensions (not ready yet). Such division make it elegant and not as big as a computer board, and what matters more it leave a space to experiment with other analogue variants, also with lamps.

I plan to build analogue module as follow:

• I/V converters on single opAmps SMD AD797 or OPA1611 type
• symmetrical filter based on MFB on OPA1632 configuration
• power supply either LT1963/3015 or discreet modules, two per each canal
• mute for noise elimination
• without capacitors in signal path

Later I will work out lamp module.

The whole circuit, where it possible, in SMD. The elements dimensions from 0603 to 1210. PCB is still being worked out. I attach the look/view.

Better and stronger – V2.0 Series Power Supply

Big success of V3.1 regulator shows me that this topology has a huge potential to implement in many applications. For those who uses my V3.1 regulator to create its standalone power supply I have got something interesting! V2.0 power supply which is better and stronger implementation of V3.1 topology.

Better means 3 more current sources which replace resistors. This give us better PSRR, more gain in error amplifier and better immunity to output current ripple.

Stronger means that is equipped with powerful TO220 transistor on dedicated heatsink. This gives me possibility to increase output current up to 3A!

But this is not the end! At the input, after rectifier and smoothing capacitor there is LC pi filter based on Common Mode inductor. Such filter could help to block disturbances which are coming from mains and passes transformer. It is also working in opposite way and blocks disturbances from supplied circuit and not allow them to pass to the transformer.

The PCB of this power supply was created in such a way that helps to remove heat from heatsink. Beneath it there are many holes which in shortest way cool it down.

Dimensions: 45 x 90 mm, high 50 mm

Sine to Square converter/clock buffer

Today I would like to show simple project which I had designed for my friend. My friend has got precision OCXO oscillator taken from old GSM BTS. Device was reworked to support audio frequency 24.576000MHz but at its 50R output it had +3dB sine wave.

Such signal is not sufficient to drive audio chips directly, so some converter was needed. I decided to add the same circuit which I had on the output of my audio clocks.

Tiny PCB contains whole circuit needed to convert signal from +3dB sine wave to CMOS compatible square wave and also its own voltage regulator. Input as well as output impedance is 50R.

Input impedance: 50R
Input coupling: AC
Input signal shape: any
Output impedance: 50R
Output signal shape: square wave
Output amplitude: 3,3 or 5V depends on used regulator

Hot and powerful! – V2.1 Shunt Power Supply

Shunt power supplies always are not so simple in use as series but all shunt fans knows, that this effort will pay of. And for that people’s I have got something special. New power supply with high current capability. Input CCS can be set up to 1000mA!

For everyone who would like to say that it is Salas I want to say: you are wrong! It is my proprietary, bipolar design, similar to V8.0 regulator and taking best from both – V3.1 and V8.0 regulators.

Designed in the way that can be used instead of popular „S” power supplies or even replace it in ready designs. Comparing to its famous competitor:

– requires less voltage drop across regulator – typically 1,5V

– is more flexible  – from few up to 1000mA BIAS current
– output voltage can be set from 3 to 15V by fixed resistor or helipot.

– very stable output voltage during warming – no more worry about your circuit!

– stable output voltage in function of output current – no more worry about your circuit!

– CLC input filter to block noise in both ways

From user experience I can guarantee that performance and sound is similar or even better.

New in Family – V9.0 Shunt Regulator

After long break from designing new voltage regulator topologies I decided to create some shunt regulator with opamp based error amplifier.

Like all my shunt regulator this one is also uses Shiklai based current source at the input but rest of design is totally different but it is nothing new on the market. Similar topology is used in TPA Trident regulator and Tent Regulator but it not has a disadvantages of the first one. Output voltages not varies from input voltage and is stable in every load condition.

Current can be set up to 100mA!

Specially designed to power precision audio components like: DACs, ADCs, S/PDIF receivers, clock circuits.

Voltage reference based on LED diode to ensure low noise. There are possibility to use precision voltage reference instead of LED diode for good voltage precision and temperature stability.

Simply decoupling circuit on regulator PCB is sufficient to ensure stability of regulator but external high capacity can be connected to provide low ripple with high speed output current change.

Dropout voltage is at least 1,5V, but I recomend values from 2V to 3V. You must calculate this for power dissipation max. 1W.

Pinout compatible with standard LM78XX regulators like LM7805 and similar. If LM78XX regulator will be replaced by V8.0 only 3 central pins can be used. If board is developed specially for V8.0 all 5 pin can be used.

Dimensions are always the same: 30mm x 15mm.

Fully differential input stage for power amplifiers

After success with my simple input stage in feeding IcePower Amplifiers with signal I decided to design new, complex input stage with XLR/RCA input and differential output.

Module has fully differential architecture with 2 pcs. of single op-amp at the input and differential amplifier OPA1632 at the output. I’m using DIP8 op-amps at the front to allow user to modify sound to its own preferences. Anyway OPA134 is a good choice for class D users (like IcePower) due to its warm Sound generated by FET input circuit.

Switch between XLR and RCA connector is used to choose right input.

Switch located at the centre of the board is used to select the gain which will be applied to the input signal. Differential gain is selectable between -6dB to 6dB in four steps.

Gain: -6dB to 6dB
Imput impedance: 100kΩ
Output impedance: 50Ω
Frequency response (-3dB): 300kHz limited by RC filter
Power supply: +/-12 – 24V (eg. Directly from IcePower module)
Power cunsumption: 100mA with OPA134
Dimensions: 80 x 60 x 35mm

Pinout of the module:

Precise and Fast – V2.1 series regulator

Next design that i want to publish today is V2.1. This design is based on old V2.0 regulator but simple NPN transistor is used as output device instead of Sziklai pair. Design is quite similar to popular regulators like: ALWSR, TT Feeder, Walt Jung low noise regulator.

V2.1 is constant current source biased series regulator. It is closed loop design with error amplifier built of operational amplifier. Operational amplifier provide accurate regulation in wide temperature range, big open loop amplification and fast transient response.

Voltage reference is made in 2 different ways. One is classic in all of my design – simple LED with low noise. Second is based on precision voltage reference to take a advantage of precision operational amplifier. This creates accurate regulator with low temperature drift.

V2.1 regulator is one of the best choice to power precision, low noise and fast switching devices like DACs, ADC, digital filters, S/PDIF receivers.

Output voltage can be set between 3,3 – 5V with standard version. Higher voltages requires to use different operational amplifier. Dropout voltage is at least 1,5V, but I recomend values from 2V to 3V. You must calculate this for power dissipation max. 1W. Maximal output current is 500mA, but for provide good stability I recommend max. 200mA (with precision voltage reference could be more).

Simple but Flexible – V1.2 series regulator

Welcome after a long break from writing!

Today I would like to show You one of my oldest design of series voltage regulator. V1.2 is exactly V1.0 with greater reference voltage and lot of space for output capacitor. It is also produced on gold plated PCB’s.

V1.2 is constant current sourced biased regulator. It is closed loop device with error amplifier based on single transistor. Voltage reference is done by 2 LEDs. Only transistor/diode design allows to make positive and negative versions of this regulator.

This design is mostly used by my to supply analog circuits with voltages +/-12V and +/-15V. It is also good choice as voltage pre-regulator before accurate and fast V3.1 and V2.1 designs. I use it as output regulator of clock power supply:

Discrete Bipolar Power Supply V1.2

Today I would like to show You one of my bipolar power supplies. It is based on same topology like in V3.X series but with cascade bias constant current source and with CCS in Vref.

Board are very compact. Only few largest component are located at top side of PCB – rest are in SMD on bottom side.

Shape of the board, dimensions and mounting holes positions are the same like in rest of my bipolar power supplies so can be swapped for choosing the best for us.

Dimensions of PCB: 60 x 82mm

Integrated constant current sources and voltage reference  circuit consist 12 LED’s so board emits light also. Output voltage is set by feedback voltage divider mounted on board – should be set during assembling.

To use this power supply You must provide only 2 x AC voltage to connectors one one edge of PCB. Here You can find example of use with my transformer board:

Maximal output Current: 500mA @15V

Maximal Power dissipation: 2W/channel