Elekit TU-8500DX 12AU7 Pre-Amplifier Kit
The TU-8500 is an exceptionally well designed pre-amplifier kit including phono stage. This is a special edition exclusively for the diyAudio store that includes 5% AMTRANS carbon 1/4 W resistors.
The front features a power switch, volume control and 4 way input selector (Line 1/2/3/Phono).
The rear features a pair of RCAs for each input of Line 1, 2, 3 and Phono, and pre-out. There's also a 3.5mm jack bound to Line 3. Switches are offered for MC/MM cartridge selection and a unity gain toggle switch for use with sources that already have enough gain.
It's a perfect match for the TU-8200 power amplifier.
Phono stage features:
- Precision RIAA equalization (CR not NF)
- Supports both MM and MC cartridges
- Low noise Opamps using sockets to allow for the easy substitution of alternative Opamps
Line stage features:
- Two 12AU7 (ECC82) tubes
- Switchable unity gain or 3x gain
- Reduced hum/background noise circuitry
- Low flux leakage R-core transformer
- FET ripple filter for B-power
- Tubes powered by the DC power supply
- DIY friendly PCB with room for larger coupling capacitors
- 100/115/220/230V input voltage selectable during assembly
- Phillips screwdriver
- Diagonal cutter
- Longnose pliers
- Scotch tape
- Hex wrench
- Soldering iron
- Stock tube: 2 x 12AU7 (ECC82)
- Opamp: 2 x NJM2068DD
- Dimensions: 252 x 73 x 270mm including projections
- Weight: ~3.1kg assembled
- Line stage
- Gain: x3.1 (9.8dB) / x1.15 (1.2dB) selectable
- Frequency Response: 2Hz-70kHz / 2Hz - 280kHz (-3 dB)
- SN ratio (IHF-A): 122dB / 129dB
- Max Output Voltage: 22V rms (1kHz)
- Phono equalizer stage
- RIAA equalization: +/- 0.5dB tolerance (20Hz - 280kHz)
- Cartridge: MM / MC selectable
- Gain (1kHz): MM 37dB / MC 63dB
- SN ratio (IHF-A): MM 108dB / MC 88dB
- Input resistance: MM 50kΩ / MC 100Ω
- Max output voltage: 7.4V rms (1kHz)
- Audio Inputs
- Phono (2 x RCA)
- Line 1 (2 x RCA)
- Line 2 (2 x RCA)
- Line 3 (2 x RCA or 3.5mm jack)
- Audio Outputs
- Pre-Out (2 x RCA)
- Input Power: 110/115/200/230V via IEC inlet
- Included tubes: NOS GE 5965
This is a great kit, and a fun build with decent instructions. What struck me is the cleanliness of the sound even at high volume with a complete inaudibility of hiss. At the normal unity gain setting, you'll notice you'll have to really crank the volume to reach your desired spl, but it's ok, because you have the 3x gain option as well and it maintains its tight, fully-fleshed, focused control on sound reproduction even when pushed past a 2 'o clock setting on the volume dial on normal unity gain setting.
I found it to be extremely transparent if your source, power amp, speakers and placement, cables and interconnects are up to the challenge.
It is neutral, transparent, and very easy to listen to over extended periods and not classically "tubelike", warm or even sterile or clinical for that matter. Try listening to something like a SACD player through it and you will be impressed with its detail retrieval, fleshed out bottom end and airy highs.
Like any kit, there are opportunities to substitute your own parts if you like to experiment with the resulting outcome of sound which I did in an attempt to make it even a little warmer, "tubelike" or vintage HiFi sounding. However, all parts supplied are well-considered and of very high quality. In fact I found it somewhat difficult to source parts of higher quality than what is originally supplied. There is no reason to have to sub anything, really. I can tell you it is rock steady and maintains a very clean, accurate, transparent sound whether you stick with all stock parts or substitute some of your own, much like how Elekit gives you an AMTRANS resistor option. Any way you slice it, it's a great sounding preamp with a clean, robust circuit design and a pretty good phono stage as well with the ability to swap its opamps to change the phono's flavor. I only wish it had one more set of RCA inputs however, so I could simulataneously hook up all my stereo gear at once including an HD radio. Great preamp, I reco...
2nd DIY amps from diyaudio. All seemed easier than the first time. PCB design is beautiful, instruction is clear enough. Very happy to have both preamp and pw amp (amp camp amp) done by myself. Thank you very much for your site, will plan the next shopping here, maybe a tube amp.
Fun build and I love the soundquality from this preamp.
I would like som xlr outputs.
Pros: very quiet, even although somewhat veiled transparency
Cons: not tubelike, no xlr connection
Directions were thorough. A lot of parts, but can be done by a careful nubie, this being my third soldering project. Everything fit together well. Sounds good so far, but I haven't tested it with a fancier setup.
One thing that wasn't clear though, was the extra bags of resistors. I didn't realize the Amtrans upgrade means you have a whole extra set of resistors, I had to desolder a few after I figured out what was going on.
Previously I had built a $17 amp and preamp with speakers. HA! It had a zillion resistors. I just took on the challenge of the TU 8500 hoping I could do it. I followed the directions closely, everything worked perfectly the first time! Exceptional!
A fairly easy kit to build (lots of parts) and took about 4 hours to complete. Instructions good. Sound is great....not to tubelike and definitely not to clinical....just easy to listen too.
Playing it into my F5 clone with PMC 20.21 speakers.
Great pre-amp kit and definitely recommended!
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