AIYIMA Upgraded 6K4 Valve/Tube Preamplifier

Test the AIYIMA Upgraded 6K4 Tube Pre amplifier.
Purchased from Aliexpress.
First trying the pre amp with the 6K4 valve/tube measuring power used, power output, distortion levels and frequency response. Then swapping out to the GE-5654's and running the tests again.
What I bought..
www.aliexpress...
Comes with GE-5654 valves/tubes..
www.aliexpress...

[@murruti1967]

La elevación de alta fidelidad se puede ajustar libremente y el ajuste de tres velocidades con un interruptor de onda. El interruptor del extremo izquierdo es "Hi-Fi". El interruptor en el centro es "Boost 1". El interruptor en el extremo derecho es "Boost 2"

[@Sonic_Ox]

Thanks for the shout out Elecifun. Yeah that's a bit different than mine with the DC input and hifi switch... I'm really enjoying this video with your scientific testing of the tube set up versus my unscientific ear tests lol. I suspect your pre amp sounds very similar to mine and I'm glad you like it. I hope you feel it's a decent value and the upgraded tubes are worthwhile. I upgraded mine to the GE 5654W as well and can hear a significant improvement that gets even better the more I use it. I've read about "burn in" and suspect its a real phenomenon. I totally agree with your "crap in - crap out" ethos. I use the best cables that my budget will allow and my best sound comes from my classic iPod ( I wish Apple was still making and supporting these). The sound coming from using my phone or computer as a DAC is simply not as good as from my iPod. Thank you for making this video Elecifun. I think you are corroborating what my ears are telling me. Cheers amigo. I hope you have a wonderful 2023.

[@Elecifun]

Glad you enjoyed the video Ox.. Uploading music now as didn't want to make this video longer. I am having an all day music listening day while I get on with my house work. Hopefully letting my tubes burn in a bit, I may hear a difference. I have ordered another tube pre amp kit which will use the 12AX7's and 12AT7's I have, I may take a few weeks on a slow boat from China but I'm sure it will be worth the wait.

[@Sonic_Ox]

I'll be interested to learn your opinions regarding the 12AX7. I have them as pre amp tubes in my favorite guitar amplifier. I know it's sort of "apples and oranges" when comparing guitar amps and hifi amps but it's all quite interesting to me. I've been toying with the idea of getting one of the larger tube amp kits from China but the ones I like start around $400. That's comparable with the USA kit I'm considering without the two month wait and arguably better components.... Decisions decisions... Lol.

[@Elecifun]

@@Sonic_Ox The 12AX7's have the largest gain (100) out of the 12A( )7 range. That's why they put them in guitar amps because the pick ups on the guitar are high impedance so need extra amplification. Looking through the tube power amps is hours of window shopping, great fun. I will start mainly because of money constraints, with a tube preamp that compliments the amplifier channels I built and my bigger 3030i speakers. Its all good fun.

[@Sonic_Ox]

That's my thinking exactly.

[@thefloop2813]

Oh man, get an inexpensive USB DAC and run apple music high res from your phone. It'll be like lifting a pillow off your system compared to the old ipods. Can confirm. I just made the switch myself this year once i realized i could plug my phone into my mixing interface. I also have a completely debugged and performance dialed schematic for the AC 12v version of this preamp if someone want's it emailed (or another route if spam is a worry) or something. It's a shockingly dial-in-able design. Im about to build the debugged schematic as my first p2p tube preamp as i have become very familiar with the circuit, the purposes of all the individual components, and have a really cool old cuban cigar box. i learned a metric shit-ton about the gear i use in the process of figuring out the debugged circuit. Output impedance under 1k, gain id guess at least +6 db. Entire range of volume knob usable until right at the very end. basically Zero noise. Quiet as my SS preamps. It's now the quietest preamp i have potentially i just dont have a way to measure by ear, but its very close, and it delivers the most usable clean gain too (Honestly, of any preamp i've ever played with). Total investment was about $25. cost/permormance ratio off the scales. Started with thestuffmade's (youtube channel) modified schematic. then slowly tweaked certain coupling values tiny little bit at a time, added negative feedback resistors but removed the cap in the proposed negative feedback design and raised the resistance value, carefully paying attention to frequency oscillations with a cranked up power amplifier and freq generator app. Very proud of what ive come up with actually, and it's a good bit simpler then the stuffmade's schematic while also, imho, out performing it. to the ear at least. P.S. i have NoS military spec 6AU6 that sound just as good as the ge 5654 pairs i have, you just get a little bit less gain out of them and they sound better to my ears without a negative feedback loop. Be careful going over 1.5uf with the coupling caps, the stuffmade says 2uf, but i had some slightly iff low frew oscillations. 1.5 UF fixed the low end impedance performance of the preamp. Adding a single reverse poled 470uf cap from r9/tr4 junction and replacing the heater filter cap with a 16v 2200uf instead of 470 or 680 uf completely removes all power supply noise from this arrangement. Negative feedback loop with a resistance value of 200k 1/2w reduced gain to just maxing out and clipping at the very end of the volume sweep, making all available gain intensely usable. Bridging the rearward leg of D1 and the adjacent empty mains ac solder pad, severing the traces for the knob based switch, and adding a switch between the amp and transformer removes all mains hum from the board's volume sweep. But so would building this preamp point to point with proper routing and shielding. Which can be done for about $25 if you figure out a chassis arrangement, outperforming some $500-1000 tube preamps in the process. There are very usable Class A tube power amp kits on ebay for $100 and less too. But you'd have to debug the circuit a little and provide your own chassis and power transformer. Most of them come with the output transformers though that i've looked at. the 12v AC version of this preamp has been my favorite tube preamp to tinker with. Ill be building several of the class A power amps, choosing my favorite after debugging, and the recreate it with a point 2 point build as well so i can properly impedance match it with this preamp perfectly. Goal is truly pure class A tube sound, hand wired, with final builds costing under $200 for preamp and power amp both. Shooing for 12-15w per channel minimum.

[@T0berius]

Hi sir ! Nice review, I have the same AD2 and I was looking for AIYIMA info I did see your post. Thanks for share with us. I have place an order right now. I bougth an unit of this AIYIMA mini preamp. Regards.

[@Elecifun]

I'm glad the video was helpful for you.

[@user-Limaa]

hi dear, could it pre amplifier a microfone or a guitar? adapting xlr plugins

[@elsaarmstrong-zp6ng]

Even harmonics give a sense of presence in valve/tube amps I think! The octave and 1/5th come out strong! Fraser

[@user-wr3km1qo4r]

Thank you @Elecifun for the review, I have a question . Can we use a power bank to power the preamp. Powerbank are known to give clean power.

[@Elecifun]

Yes m8, nice clean power

[@DramaticWave]

Good day! I don’t know English well, I bought the same pre-amplifier. Tell me why this three-position switch on the left?

[@Elecifun]

@DramaticWave Hi, good day. The switch on the left is "Hi-Fi." , Switch in the centre is "Boost 1". The switch on the right is "Boost 2." Play with it see how it sounds best for you.

[@davidleegoth]

Can this be used as a phono preamp? If so what power supply is used for this?

[@Elecifun]

No I don't think so. The power supply would remain the same between 12 and 16VDC

[@elsaarmstrong-zp6ng]

Could it drive a set of studio headphones ?

[@dionatasalmeida9634]

Hi, I'm Brazilian. I don't speak English, but I would like to know if this 6k4 tube preamp is worth buying. ? I've been wanting to buy it for a while, but I don't know about the quality. I want to use this 6k4 tube preamplifier, in the aliexpress C160H TPA7498E 160W amplifier.

[@Elecifun]

It sounds better with the GE tubes

[@Elecifun]

GE5654

[@dionatasalmeida8581]

@@Elecifun Hello. sorry for the delay in replying. thank you very much for the feedback friend. I haven't bought the preamp yet.

[@dionatasalmeida8581]

@@Elecifun bought this amplifier C160H TPA7498E 160W * 2 Bluetooth5.0 + AUX

[@Elecifun]

@@dionatasalmeida8581 Are you talking about this from Aliexpress ? Item number 1005004500079916

[@decem_unosquattro9538]

Oh it has no power it's the audio signal. Okay.

[@decem_unosquattro9538]

Oh incidentally I discovered the problem with my fm transmitter! 😑🤓

[@Elecifun]

Great stuff, what was the issue?

[@decem_unosquattro9538]

@@Elecifun There are two what appears to be zener diodes. One is a zener diode the other is something called a varactor diode which is something new to me. 1. ZD 4.3V 2. FV 1043 The problem is they're in the wrong positions. I need to swap them. I just hope I have not damaged other components on the board. I'll order these components and replace them both. Dec.

[@Elecifun]

Fair play for figuring it out. Hat tip, Sir!

[@decem_unosquattro9538]

@@Elecifun Thank you sir ! 😂👍 I swapped the two components over, and it's WORKING albeit not very clear and I think maybe I need to try to find an empty station slot. 😅👍 There is a 4 pin switch block and another H ~ L switch which gives me multiple different stations to transmit on. I'll have to fk around with it a bit more to try to get it to work properly, still it seems to be working albeit I'm still wondering whether I damaged any components or not? 🤔.

[@decem_unosquattro9538]

A little tube amp ! How much per side? 🤔

[@Elecifun]

Its a pre-amplifier used to drive a power amplifier, it's fits between the source and power amp. This one being valve/tube adds a subtle 2nd harmonic giving a fuller/richer sound which many enjoy.

[@decem_unosquattro9538]

@@Elecifun oh okay I see. . I guess I'll never know what it sounds like unless I build one myself. 🤔

[@Elecifun]

I am uploading music now, couldn't add to this video as it was to long for my concentration.

[@marishkumar607]

@@Elecifun can you suggest me a good vaccum tube preamplifier from fosi audio or aiyima ? Please mention the details of the product and suitable replacement for the stock tubes .

[@poyocru]

@@marishkumar607 aiyima t3 it's cheap and good but by replacing valves to get 5644 (also cheap) you can get a little better sound