Tubified Class D Chi-fi amps, or better hybrid . 1

Tubified Class D Chi-fi amps, or better hybrid .

We had a lousy wet winter with gales , so we spend a lot of our time indoors, catching up with reading books and listening to music in the background, we hardly have the TV on.

What we noticed in November last year, is that our use of electricity had gone up by 10%.

In general we consume 40% less Gas and 40% less electricity  of the average dutch household, the 10% difference with other years was the amount of hours we listened to background music  , on heavy amps like Cayin Tube amp, Audiolab 8000 serie, or the Quad Pre amp and power amp, with on average uses 200 watts an hour or more.

But i am addicted to the lush sound from the tube amp  (www.deviantart.com/pagan-live-…), so started looking for a hybrid amp with tubes in the pre-amp , and Mosfet power amp section For background music .

Saw some reviews about very efficient  hybrid class D amps with tubes in the pre-amp,  which had come a long way from the harsh brittle sound from 10 years back.

So in the black Friday weeks on amazon, found the very cheap Chinese Fosi T20 amp for 78,-.

It is very small , 10 x 15 cm footprint and around 8 cm high due to the Chinese 6A2 tubes,  amp rated at 2 x 50watts with 4 Ohm speakers.(more realistic without any form of distortion is a clean 2 x 35 watts at 4 ohm and 2 x 25 at 8 Ohm ), but is still very good!

To put it to the test, i hooked it up to a Marantz CD6005 CD player with the very analog sounding Cirrus Logic DAC, for the  RCA interconnect between the cd player and the amp , and the cables from the amp too the Telefunken TL500 4 Ohm speakers i used my preferred premium  Oehlbach cables.

Fosi T20 hybrid amp:

moonstarreviews.net/fosi-audio…

Marantz cd6005 :

www.marantz.com/en-gb/product/…

Oehlbach cables :            

oehlbach.com/en/https://oehlba…

Telefunken TL500 Speakers :

hifi-wiki.com/index.php/Telefu…

www.deviantart.com/pagan-live-…

I listened for hours to cd's with acoustic instruments , whether cello violin guitar, and most importantly female and male singing voices , i have to say i was pleasantly surprised with the very open airy sound , perhaps not high-end'ish , but really very very good Chinese Hi-Fi amp for so little money !

Only thing was that with very high female voices , and high violins it can become a bit edgy at the top, which could lead to listening fatigue .

So opened the amp to see what it contained besides the 6A2 tubes !

It has a class D amp chip from Texas Instruments the TPA3116, the 2 op-amps are the N5532 from Texas instruments, and the Capacitors and coils are from Paxcon (Taiwan), altogether good quality components.

So the only thing that worried me were the Chinese 6A2 tubes which have a high gain, and presumably that they were the reason that it can become edgy.

Good replacement tubes , can be the 6AK5, 5725, 5654, 5654W , or even better the JAN (joint army navy) mil-specs 5654W tubes, or the European equivalent the EF95 tubes. 

Long story short, i settled for a batch of  NOS (New Old Stock) JAN General Electric 5654W tubes which did the job and gave the higher tones a tube like silky edge ! this also because NOS Telefunken, Valvo, Philips tube pairs are between 100,- and 200,- a pair and are a bit overdone in regard quality versus costs for use in the Fosi T20.

I am very happy with this small amp powering the Telefunken TL500, for background music without listening fatigue, and consumes around less than a fifth , about  40 watt an hour, and that is what started this quest !

Already expanded the Hybrid Quest, for looking for high-end'ish Hybrid class D amps, with the Texas Instruments TPA3250 of even better the TPA3255 chip set, like the Fosi V3