Nobsound T7 Little Bear Tube CD RIAA Preamplifier User Manual
- June 14, 2024
- Nobsound
Table of Contents
Nobsound T7 Little Bear Tube CD RIAA Preamplifier
RIAA phono part
RIAA freq response 20hz-20kHz +/- 0.5dB, S/N ratio >85dB
THD <0.05%, input sensitivity 3.0mV, gain 40dB,
Nominal / max output 300mV / 1.8V
Output impedance 200 ohms, input 47k ohm / 220 pF
AUX part:
Input voltage :AC12~18V
Frequency response :20 HZ – 20 KHZ
Input sensitivity 300 mv
SNR : 96 db
Total harmonic distortion <3% (1 KHZ)
Power range output : 0.2 W
Output impedance : 100K
Input impedance : 50K
Tube model : 6J1
Wire connect guide
Remark:
-
Make sure turntable’s GND jack wire to TT’s GND jack.
If turntable without GND jack . ignore it -
Make sure both 6J1 tubes are full plug into tube socket.
-
Make sure the selector switch is set to correct position.
-
If possible. wire TT’s GND jack to Ground
Function manual
A :T?’s GND jack, wire your turntable GND to this jack, and if possible.
wire this GND jack to ground also (We also package a 3M ground cable inside
the box)
B :PHONO input jack, connect to your turntable PHONO output jack
C :LINE OUTPUT jack, connect to your power amplifier
D :Power ON/OFF switch
E :lnput source selector: set T7 work mode, AUX or PHONO, if you need it
work for turntable, just set it on ” PHONO” mode
F :AUX input jack: this interface support CD,lpod,Mp3 player …… or
similar player music input
NOTICE:
-
In first time use this T7, please do not use the BACKUP tube which is there is a “B” character outside the glass,
-
Before use this T7, make sure your turntable with PHONO output. Check your Turntable output Jack. if it’s just with “PHONO “character, or nothing on it. That’s usually is PHONO output. You could use it with T7, but if it’s with “LINE OUT” or “LINE”, that’s mean your turntable is bulit-in phono preamp already. Don’t need T7 any more. some of turntables with a switch for setup turntable output signal mode, Please setup it in “PHONO” mode.
And, if you feel the sound like on the water. That’s usually mean your turntable isn’t output PHONO signal. It’s LINE OUT signal, or the T7 phono function broken.(please contact us for warranty). -
Suggestion: if you connect T7 to Digital amplifier. please make sure your power supply for digital amplifier is good quality, the cheap power supply will make loud back noise. We suggestion you better use your laptop power supply for the digital amplifier. at last ,we suggestion connect T7 to a normal AV amplifier or tube power amplifier or pure HiFi power amplifier. that’s the best way
Q&A about the hum problem
Q: I got a loud hum with this T7 phono preamp.
A: For the hum noise, in the beginning, we have to clarified that all phono preamps have a certain of background noise. It won’t be loud, while a little loud is just normal. Turntable is a kind of analog players and cannot be compared with digital players in this respect. Besides, there are many factors which may lead to bad noise. To find the right reason, you need to do some tests and here are some instructions.
Reason A: T7 isn’t connected to ground well.
This is the most common and unnoticed reason. Please test it following the steps as below.
While the device is playing music, picking up the GND copper part of T7 with your fingers. If the background noise is much lower, then T7 isn’t connected to the ground. For this issue, we prepared a 3m wire in the package for you to solve it by yourself. Just use it to connect the GND with any large mental item in your home like windows or mental tables.
Reason B: T7 doesn’t match with your amplifier well.
There is a possibility that T7 may not match with some digital amplifiers well, which may lead to very loud noise.,(we’ve test it with few T and D Class digital amplifier. And found that. The T Class amplifier is best. Very quite back noise.. But. The D Class amplifier with loud noise. )
That’s why we recommend using professional pure HiFi amplifiers like AV amplifier or vacuum tube amplifiers (it will be better if the amplifier isn’t equipped with Bluetooth).
Reason C: The RCA wire has a poor quality.
A good RCA wire will be equipped with an anti-jamming magnetic ring, which can effectively reduce various interference.
Q &A about the sound distortion problem:
Reason A : your turntable output signal isn’t PHONO. Maybe is LINE OUT.
Please check the turntable output JACK. if there is a PHONO/LINE OUT switch.
Please set it in “PHONO’ mode.
Reason B : T7’s RIAA function part broken. Please contact us to get
replacement main board. (or if you’re DIYer. You also can replacement it. It’s
80% the OP chip burn. (the IC mode is: 2068, you can replace it to 5532 or
similar chip.