Fosi Audio 7-Pin 5654W Tested/Matched Vacuum Tubes Substitute for 6AK5 6J1 6J2 6J1P EF95 Preamplifier Tubes (2PCS)

I thought this review would be easy, either thumbs up or down. This was not the case. I used a WiiM Pro Plus with Spotify Connect as the source. I compared the stock 6k4 tubes that came with the Fosi Audio P2 headphone amplifier with the JAN 5654W tubes matched pair, sold by Fosi Audio. To make tube swapping faster, easier I used 2 of the Fosi Audio P2 amplifiers. The headphones I used for this test were all Sennheiser.HD-497 (32 Ohm): The sound with the 5654 tubes was noticeably better than the 6k4 tubes in most categories. I used a custom WiiM EQ setting with the HD-497 headphones for this test.HD-600 (300 Ohm): The sound was pretty much the same when comparing the 5654 tubes to the stock 6k4 tubes. The HD-600 headphones were harder to drive, needed an estimated +6dB (5654) and +8dB (6k4) compared with the HD-497 headphones. I used the Fosi P2 volume control to match levels. Bass and drums were slightly improved with the stock 6k4, otherwise it was a toss up. Male and female vocals were excellent with both tube types. No WiiM EQ was used with the HD-600.HD-560S (120 Ohm): Bass was slightly better with the 5654 versus the 6k4. Male vocals and upper midrange were slightly improved with the 5654. Female vocals were excellent with both tube types. Guitar sounded better with the 5654. Gain with 5654 was 2dB higher than with 6k4 (I set volume one click stop higher when using the 6k4 to match levels). I used a custom WiiM EQ with the HD-560S for this test.Categories:Bass, Vocals (harmony, male vocals, upper midrange, female vocals), drums, cymbals and guitar (acoustic an electric.)I recommend purchasing two of the Fosi P2 headphone amplifiers if you are going to regularly swap tubes when using different headphones. The tube sockets are mounted directly to the circuit board. The stress of repeatedly replacing the tubes can't be good for the long term life of the P2.Get a tube pin straightener (7 pin miniature); check on the bay.

I bought a little Fosi preamp and placed these tubes in it. It sounds incredible, I compared this preamp to a turntable that had a preamp built-in and these tubes in that cheap preamp sounded so much better. So I thought I'd upgrade my preamp so I bought an expensive Project preamp and some expensive Russian tubes. I gave them time to burn in and something just sounded off. I tried all of the configuration dip switch range settings and I could tell something was missing. So I A/B'd against my Fosi with these tubes and it sounded so much better. I wasted over 600$ on a more expensive preamp and Russian tubes. If you have a Fosi or another record player preamp and use these tubes you are going to be blown away. Take it from me, I've done the comparisons. These tubes sound great. I bought a 2nd pair of these tubes just to have a backup from the same factory run. The high end is very clean and crisp compared to the other preamps I've tried. I need my presence open and clean and these tubes do that.

Replaced my 6A2 tubes that came with my preamp, I did notice a bass difference just crisper or more controlled, kinda hard to explain. They are not as loud as the 6A2’s, I had to increase my setting on the preamp from 39dB to 42dB for just a little louder volume, if I didn’t have the option on my preamp to increase the dB setting I would have been disappointed with the lower volume. These tubes are also about half the length of the 6A2’s so when installed they only stick out about a half of an inch, I’m leaving them in but they maybe a little bit harder to remove because you have less to grab on to. Overall a good replacement, I do think the 6A2’s are just fine to use also.***update*** these tubes definitely need some burn in/break in time after 15 hours of use I was able to turn my dB switch back down to 39dB because the volume increases as they burn in. I didn’t notice any more changes from 15 hours to 30 hours so they seem to be good after 15 hours. I didn’t notice any changes in the 6A2’s from right out of the box to 44 hours of use before I replaced them with these. All of the reviews wondering why the box is labeled made in China, Fosi Audio is in China.

Recomendado

Despite some trouble replacing the rather harsh-sounding tubes included with the Fosi T20, with patience and strong light the task was done and the sound vastly improved. Driving a 50 year old pair of Klipsch K-4s augmented with add-on tweeters the Bluetooth sound off YouTube and Amazon Prime is luscious, broad, detailed, transparent and while softer is more room-filling. Highly recommended but install slowly with care. These tubes do not slide right in like a DuMont television of yore.

I gave longevity 4 stars as I just installed the tubes so have no experience on how long they will last. 4 is based on they are working perfectly now and with the warranty they have I am assuming they will.Sound and value I can speak to. There is a noticeable expanding of the sound around the frequencies of singers. The sound is smoother and lost the grating edge it had with the previous 6J1 tubes. Value is very good considering the tubes are tested and matched. There are lower priced tubes available but they are not tested and not all NOS tubes work or are up to spec after sitting for 35 - 50 years.If you need to replace some 6J1 tubes I would strongly suggest these.

These are right on the edge of what you could call matched. I mean they are matched but they're not matched. My particular set is 8% off according to my tester. They promised 5% or less and even 5% is too much. They still sound good I have to adjust my balance a little bit because one of the tubes is weak but they have a nice warm tone and I don't feel like shipping glass back to them and dealing with all that so I'll just buy from someone else next time I guess.