[jk@home]

I've read one can remove all the opamps on the Fosi and just replace the particular ones needed. So in my case, it would just be one per amp (SE mono). Worth a try.



Regarding the FU amp....just got a 2nd strike out, this time the seller's fault."Product Undeliverable", for what ever reason. After it was shipped out, damaged in transit maybe? Or tariff related.

Now considering the (certainly not cheap and cheerful) Muzishare x3t. Thinking the EL84 tubes will be fine for a mid-range only tube amp, driving my Lii speakers. From what I have read that Chinese tube brand has a pretty good track record.

[Jon L]

Now considering the (certainly not cheap and cheerful) Muzishare x3t. Thinking the EL84 tubes will be fine for a mid-range only tube amp, driving my Lii speakers. From what I have read that Chinese tube brand has a pretty good track record.

Better hurry.  Now reports are popping up that products from China (>$800) are getting the >100% tariff slapped on before can clear customs.  The exception for <$800 products are scheduled to expire on 5/2/25. 

[jk@home]

When I had ordered the amp the first time, also ordered some extra RCA 829B and Mullard 12AX7 (plus adapter) tubes, mainly for a backup if the OEM tubes failed. A case of cart before the horse, as it seems.

So anyway, reordered the amp again, this time from the aliexpress vendor on page one. The basic wood sided with cheapest shipping model. And a much more cheap and cheerful price. It's on its way here, fingers crossed.

[jk@home]

So I bought this thing on the 11th, showed up today. 4-5 days shipping, from China to the east coast USA. Wow.


I had bought the cheapest version, the one with the wood sides. They sent me this one instead. Thats OK


Close to half the price the Amazon vendor wanted. Looks like the trannys are a little crooked. I may cover the whole amp with a cage, so no matter.

Does it matter what wires go to each terminal of the FU19s? Also, should there be a problem controlling the power to the amp using a loT relay?

[FullRangeMan]

Yes, the 2 top caps are the plate output to the OPTs, install as showed in the photos.
I dont know what loT relay is.

[jk@home]

Its a relay module that can use a trigger signal to turn stuff on. Basically will add a trigger input to a non-trigger piece of equipment. As long as the current draw is not too high.

https://dlidirect.com/products/iot-power-relay

Before I installed the tubes, popped off the bottom cover.



https://imagizer.imageshack.com/img923/295/lyCMUC.jpg

And here is the instructions, translated to english:



https://imagizer.imageshack.com/img924/786/aNE1uo.jpg

[Jon L]

Tube cap wire can go to either pin.  Doesn't matter.

Some parts inside seem better but some worse than the wood-side version.
For example, that small orange coupling cap seems to be even cheaper version than the cap in the wood-side version.  Still, I would listen to the stock form for at least a week to find out how the stock amp sounds before swapping out parts 

[jk@home]

It appears the the wide chassis models have 4 and 8 ohm speaker taps? The long chassis, only 8 ohm.

[FullRangeMan]

It appears the the wide chassis models have 4 and 8 ohm speaker taps? The long chassis, only 8 ohm.

Small tube amps in the hey days of tubes used only 16 ohms speakers for a more stable operation, 4 ohms is too low for a flea power amp.

[FullRangeMan]

Its a relay module that can use a trigger signal to turn stuff on. Basically will add a trigger input to a non-trigger piece of equipment. As long as the current draw is not too high.

Dont use this gadget with tube amps, it looks suited to cell phone chargers or kitchen appliances.
Plug tube amps direct on the wall outlet.

[renaudrenaud]

So I bought this thing on the 11th, showed up today. 4-5 days shipping, from China to the east coast USA. Wow.

Waiting for your feeling about it!

[jk@home]

I think it is going to work out fine. Still early on, with the Chinese supplied tubes, first tried the amp fed by the single ended outputs on my SMSL-SU-8 (v2) DAC. And then tried adding a line stage in between (W4S Mpre), in order to use the balanced outputs of the DAC, and adjust the gain between. Liking that better. The Lii drivers we have are rated by the manufacturer as 96dB (2.83V/1m) sensitivity. This amp has no problem with that. 
 

[renaudrenaud]

Ha, the SMSL SU8MkII... I bought it because it was cheap and was curious. Received it and sold immediately all the DACs accumulated since years, no need, no more.

Today I use the really cheap DL200 for the readable screen, still with a symmetric output (I use often active monitors with XLR inputs). My LAN player is some 15€ Orange Pi Zero2 and I coded some LCD informations (when no music, it's a clock).



Today the DL200 is used as a DAC with 100% volume, the symmetric output is connect to the symmetric input of the preamp, a Topping. I use the RCA input for the turntable.




I appreciate the timbre quality and the 3D presentation fro the FU19. The input tube was replaced (one channel had stopped working after a month of use), and the new tube seems far superior, with an extended bandwidth. The result is quite incredible, and I'm thrilled to have such a pleasant-sounding setup at a ridiculously low price. It's a golden age for HiFi, where gear delivers astonishing performance at absurdly low costs!


 

[FullRangeMan]

In the hey days of single ended tube amps all amps had good sound, no audio magazines, no expensive amps, the probs started when Transistor amps arrived 

[renaudrenaud]

It was a question for me. I said myself, wait a minute, this simple amp is really nice, so does it means many many years ago it was doable to have some nice quality amp with simple schematic and simple tubes ?

[jk@home]

I replaced the FU-19s with some 829B tubes, will try them for a while. Waiting on an adapter from China to try some Mullard 12AX7s I have on hand. It is a loose fit going to the 829Bs, I was able to use a small eyeglass screwdriver to close the connectors enough, but still would like better connection. Does anyone have a source for a suitable fitting terminal?

BTW, for those who love the 829B sound and want to upgrade...
http://www.finaleaudio.com/829b-special

[viggen]

BTW, for those who love the 829B sound and want to upgrade...
http://www.finaleaudio.com/829b-special

only costs about 50 times more.... makes me think can throw more expensive parts at the FU19 to emulate the finale.

[Jon L]

only costs about 50 times more.... makes me think can throw more expensive parts at the FU19 to emulate the finale.

Finale 829B Evo claims 18 watts of power in "single-ended class A," which probably means the two tetrode sections in one 829B is run in parallel single-ended mode.  The 4-5 watts claimed for FU30/829 leads me to believe it's single-section single-ended, which I would actually prefer for purity of sound quality   

[Jon L]

The input tube was replaced (one channel had stopped working after a month of use), and the new tube seems far superior, with an extended bandwidth.

Can't see the input tube in the photo well.  Which tube is that?

[viggen]

According to site:

829B Push Pull Mono-Blocks

Driver Tubes : 12AX7 x 2

Rectifier Tube : 5U4 / 5T4 / Aqua 274B / 5V4

Mick got a pp version I believe.