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My audio system.....
#1
My audio.

For outside listening I use the kit:
Xduoo X3II with Rockbox installed (Haas Surround is sensational for long headphones listening)
Koss Porta-Pro headphones (they have no different in their price class, open design, the best review was: on these headphones I heard the bass player for the first time ...).
In this player I use compressed files with the amazing OPUS codec with an average variable bitrate of 224kbit / s (this codec has a low latency and minimized pre-echo effect, it replaced the tuned OGG Vorbis for me)

At home:
Currently Moodeuadio 6.5.2. on Raspberry Pi with DAC ES9038Q2M

Two amplifiers:
The first is an experimental own tube construction based on the Super Triode Connected topology built on the EF80 and ECL86 electron tubes in each channel plus the EM83 double magic eye (only produced in DDR). The STC topology is used to obtain triode characteristics from a pentode, a meter or even an integrated audio amplifier, which are characterized by high linearity at independence with load impedance. Higher powers are obtained than in the case of pentodes or tetrodes in a triode connection. Because the triodes have a low impedance as a signal source, it is also easy to get a wide bandwidth using cheap speaker transformers. 
   
   

The second amplifier is a simple Chinese board with the TPA3116D2 chip - a digital class-D amplifier. Waiting for a slightly better board (at the input of the amplifier, e.g. polyester instead of ceramic with too low capacitances or cheap electrolityc capacitors, better coils in the output filters....).
Despite the very low price and the fact that it is a D-class, it sounds sensational, even on cheap plates from China offering a sound not worse than many expensive HiFi sprats as far as modern and vintage. The variant with a lower maximum power of 2 * 30W, i.e. TPA3118D2, can handle without a heat sink when running at full power. It is solidly secured - instead of a loudspeaker, a screwdriver will survive Wink

TPA3116D2 datasheet: http://www.ti.com/lit/ds/symlink/tpa3130...9091632741

There is a second series with better parameters, higher powers, and unfortunately a higher price. TPA3241, TPA3245, TPA3250, TPA3251 and TPA3255. Double the clock speed offers a lower level of distortions in the upper part of the acoustic band.
TPA3251 datasheet: http://www.ti.com/lit/ds/symlink/tpa3251...9092099537

In these systems it is worth using additional external negative feedback, which improves the load and more importantly, especially with the TPA32xx series allows to eliminate accidental shutdowns during loud playing triggered by short momentary moments at the maximum peak level
It is described here: http://www.ti.com/lit/an/slaa788a/slaa78...9092319316

TPA3116D2 and TPA3118D2 play in great detail. Some say that in comparison to the TPA32xx series they have a minimally withdrawn midrange but this is a subjective rating. At audio freaks and vintage audio events, the chineese kit on the TPA3255 was able to remove the heigh-end tube amplifier for several thousand USD from the pedestal.

I plan to make a hybrid amplifier, quite unusual because instead of the traditional transistor unity-gain buffer in class-A or class-AB after the tube stage where all voltage gain is to be TPAz 32xx series chip with external negative feedback. TPA with external feedback has a gain of about 4, so it does not differ from typical hybrid amplifiers. Maybe I will add a sensational tone control used in the Revox B251 - a bit similar to a two-channel parametric equalizer (35Hz and Q = 1 +/- 12dB, 13kHz and Q = 0.6 +/- 6dB). Electron tuber ars EF80 polish production or EF184 made by RFT from DDR due to a nice mesh screen, ECC81 maybe ECC82 (both ECC are made by RFT) and magic mesh EM83 (also RFT).

   
The visible speakers are for a monitor used as a television connected to the Dreambox DM900UHD

Tomasz
My little brick in this device - a tube buffer similar to the diamond topology (double cross coupled balanced path). http://zweimann.pl/product/zweimann-dac-...e-edition/
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#2
Tubey goodness :-)
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#3
Magic eye? I haven’t seen one of those since my dad’s 1951 Magnavox radio console died Smile  I have fond memories of all things based on vacuum tubes, some I designed and built and some I bought, but I won’t go back.

These new-fangled Class D amps still seem like magic to me. The components which make them possible at a reasonable price didn’t become available until long after I was designing my own amps. Like every other class of amplification it has its minuses as well as pluses but when done well the amps are a marvel.

Kudos for your builds.

Regards,
Kent
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#4
Class D amplifiers from these series are worth interest. Chinese modules made of the cheapest elements sound really good, but the carefully applied these chips will repay with very good sound. Of course, the optimization of the layout, the correct layout of the PCB is no longer a trivial matter, here you need to feel fast clocked pulse systems. Engineers from Texas Instruments carefully approached the topic. These are no longer clumsy buzzers as at the very beginning of the production of these systems. There was a really significant qualitative and engineering leap as well. The second series (TPA32xx) is clocked at around 2MHz, the first around 1MHz. Quite complex timing schemes were used to smooth out the output waveform to even limit the output filter even to the ferrite "pearl" on the wire plus the Zobel circuits.
These circuits surprise with a very detailed sound, they do not forgive any signal at the input mercilessly exposing the low quality of the signal source. The price is .... the module with TPA3116D2 is 10USD. Only switched mode power supply, e.g. industrial mounted on a DIN35 rail, and you can surprise Hi-Fi fans.
....
Magic eye EM83 in action: https://youtu.be/4MBTfz4qUas
My little brick in this device - a tube buffer similar to the diamond topology (double cross coupled balanced path). http://zweimann.pl/product/zweimann-dac-...e-edition/
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#5
EM83 and EF0 in close-up

https://youtu.be/CCLa5cchYBA
My little brick in this device - a tube buffer similar to the diamond topology (double cross coupled balanced path). http://zweimann.pl/product/zweimann-dac-...e-edition/
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#6
Hi Studi
I'm ordering one of those ES9038Q2M DACs and interested in trying it with a TPA3118D2 amp to drive some little Wharfedale 70w bookshelf speakers
Can you recommend something cheap off ebay?
Thanks!
Edit: I found this I think I'll give it a try!
https://www.ebay.co.uk/itm/TPA3118D2-Dig...3487748760
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#7
(06-18-2020, 09:26 AM)frenchy Wrote: Hi Studi
I'm ordering one of those ES9038Q2M DACs and interested in trying it with a TPA3118D2 amp to drive some little Wharfedale 70w bookshelf speakers
Can you recommend something cheap off ebay?
Thanks!
Edit: I found this I think I'll give it a try!
https://www.ebay.co.uk/itm/TPA3118D2-Dig...3487748760

The TPA3118 data sheet informs about a maximum power of 2 * 30W for 8 ohms and 24V power supply. The first limit is the supply voltage - 26V. The second limit is the cooling method. The system is cooled by the copper surface on the printed circuit board. It is highly recommended that the thickness of the copper layer is 70um. If the cooling is insufficient, the power of 2 * 30W cannot be obtained. These 45W given in the picture attached to the auction are yes but as 2 * 22.5W. Another problem besides the PCB itself is the filter coils, it is not known at what intensity saturation will occur. These coils look similar to those on cheap boards ( https://www.google.com/url?sa=i&url=http...AdAAAAABAM ) where one TPA3118 chip will work as two bridge circuits working in parallel offer theoretically 1 * 60W at 4 ohms. About 45W turns out to be real. These boards have the disadvantage of a "step" of power drop around 90 Hz (frequency response), the reason is that the wrong capacitors were used at the input of the system. I bought a cheap 2 * 50W circuit board on TPA3116 ( https://www.google.pl/url?sa=i&url=https...AdAAAAABAU ). There are no negative or critical comments about the quality. I was tempted to seemingly better, MKT capacitors, coils of filters on large ring cores. ( https://www.google.pl/url?sa=i&url=https...AdAAAAABAH ). Unfortunately I was disappointed. Apart from the start and end positions of the potentiometer, this amplifier module hums. Low quality RCA sockets rhodium plated and not gold plated. Up close, the PCB itself turns out to be of poor quality of laminat and copper layers. Unfortunately, the appearance presented in the picture does not guarantee quality. 
It's hard to honestly recommend something from the cheap Chinese modules offer. It can be satisfied or the purchase is unsuccessful. The risk is low due to low prices.  The alternative is your own PCB design, ordering a PCB from a professional service provider making the PCB and finally soldering the system from the purchased components from reliable suppliers..
My little brick in this device - a tube buffer similar to the diamond topology (double cross coupled balanced path). http://zweimann.pl/product/zweimann-dac-...e-edition/
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#8
Solving noise problem on the other board with MKT capacitors. The main reason is the no clock synchronization of chips. Both TPA3116 works in master mode independently of each other.  Another problem is the manufacturer chose a high gain of 36dB and left the input capacitors of the same value as for the 20dB gain. The difference is in the input impedance. for 36dB it is 9k and for 20dB 60k. The capacity of 1u5 condensers is good for 20dB, for 36dB it should be 10u. The gain is too big for a DAC. 20dB is enough. Then the soldered capacitors will be OK. We peel off the heat sinks. We choose one zTPA3116 as master. Next to it we find a 47k resistor, change it to a 5k6 resistor. We remove the 75k resistor. With the second TPA3116 which will be a slave 47k resistor replace with 51k, 75k resistor replace with 51k. It still allows you to make a synchronization link. we connect together through a 4k7 resistor legs 16 of both systems. They are from the page of the potentiometer and from the page of 3116 inscriptions on the PCB. Additionally, we solder a 27p - 47p capacitor between the leg 16 of the slave system and the mass - e.g. pins 14, 15. End of the modification, we stick with heat-transfer glue heat sinks. The potentiometer may be replaced for better quality. 
Another issue is the choice of timing. Chinese module manufacturers choose a 400kHz clock (pins 13, 14, 15 shorted to ground). You can switch clock speed to 1200kHz. Pin 13 should be desoldered from the pad on the PCB and connected with pin 7 through a 100k resistor. At synchornic operation of two circuits with 1200khz clock on the slave side the capacitor connecting pin 16 with mass should probably have a reduced frequency to 4p7 - 10p. All resistors on the PCB are SMD size 0603.
My little brick in this device - a tube buffer similar to the diamond topology (double cross coupled balanced path). http://zweimann.pl/product/zweimann-dac-...e-edition/
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#9
I have been a tube audio enthusiast for decades. Tube power amps have better high frequency response compared to Class D, but you need high quality audio output transformers (expensive). It is impossible to achieve the low frequency response of Class D with a tube amp, the output transformer would need to be huge. I have personal experience with Icepower modules, but have read excellent reviews on the TI products. What speakers are you trying to drive? That will largely determine the amp you need. Audio is a compromise. High quality Class D amps are here now, and are an excellent choice in many applications.
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#10
(07-02-2020, 03:22 PM)hifinet Wrote: I have been a tube audio enthusiast for decades. Tube power amps have better high frequency response compared to Class D, but you need high quality audio output transformers (expensive). It is impossible to achieve the low frequency response of Class D with a tube amp, the output transformer would need to be huge. I have personal experience with Icepower modules, but have read excellent reviews on the TI products. What speakers are you trying to drive? That will largely determine the amp you need. Audio is a compromise. High quality Class D amps are here now, and are an excellent choice in many applications.

I have a SET tube amp Art Audio Carissa 16WPC 845 and a 6-tube 6DJ8 phone EQ amp. I have a few pairs of loudspeakers. The pair used for the audition of my PCM5122 DAC + Class D amplifier design is Dynaudio Contour 1.3SE. I used the tube amp as the reference of tonality and sound quality. I have not used my tube amp for more than 9 months since my own design "Integrated RPi + PCM5122 DAC + TPA3116" sounds better than the Carissa. I have used a pair of very low jitters TCXOs to drive the PCM5122 in master mode. My TPA3116 class D amp has unique features balance driven input and inductorless output. So, there is no inductor at the output to muddle the sound. Anyone interested in getting this unique RPi integrated power amplifier and/or headphone amplifier can send email to info@soundberryaudio.com. I will also sell DIY kit which includes the complete enclosure hardware without RPi.
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