Today i tested the second edition of the Mini-Me.
And it sounded very good.
This design has only one 48V power supply. And is very cheap to build for a tube MM phono preamp.
Some spec's:
- Amplification = 175 x(44.5db)
- THD = 1.1%
- Noise = -72 db
- RIAA = < +/-0.5db
- Board size 100 x 100mm
The power supply is a cheap 48V smps, they sell them for power over ethernet.
Schematic is the same as the first Mini-Me with a view adjustments.
http://www.diyaudio.com/forums/analogue-source/242855-mini-me-phono-preamp.html
The tubes i used are 6N28b-v.
And it sounded very good.
This design has only one 48V power supply. And is very cheap to build for a tube MM phono preamp.
Some spec's:
- Amplification = 175 x(44.5db)
- THD = 1.1%
- Noise = -72 db
- RIAA = < +/-0.5db
- Board size 100 x 100mm
The power supply is a cheap 48V smps, they sell them for power over ethernet.
Schematic is the same as the first Mini-Me with a view adjustments.
http://www.diyaudio.com/forums/analogue-source/242855-mini-me-phono-preamp.html
The tubes i used are 6N28b-v.
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Because of the low voltage it is difficult to build the same SRPP MC pre as the first MIni-Me. But you can try adding a same stage as the firststage of the Mini-Me SE without the cathodecapacitor. I can draw the schematic later.
The soundpicture is different as the first Mini-Me. It is less wide but tighter. Tonal they are the same. It is a question of taste with you like most.
Hoexter, is that the village with the bikers castle?
The soundpicture is different as the first Mini-Me. It is less wide but tighter. Tonal they are the same. It is a question of taste with you like most.
Hoexter, is that the village with the bikers castle?
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Thanks.
I will compare the phono pre with:
- Lm4562 opamp Diy pre on accu.:forum.zelfbouwaudio.nl • Toon onderwerp - MM phonovoorversterker op accu/zonnecellen.
- Mini-Me first edition with 6n16 tubes.:forum.zelfbouwaudio.nl • Toon onderwerp - 6N16 phonovoorversterker , Mini-Me
- Project Tubebox SE 2.:Pro-Ject Audio Systems
- Yaqin Ms-12b.:AAAVT SM-12B phono pre-amplifier [English]
I will compare the phono pre with:
- Lm4562 opamp Diy pre on accu.:forum.zelfbouwaudio.nl • Toon onderwerp - MM phonovoorversterker op accu/zonnecellen.
- Mini-Me first edition with 6n16 tubes.:forum.zelfbouwaudio.nl • Toon onderwerp - 6N16 phonovoorversterker , Mini-Me
- Project Tubebox SE 2.:Pro-Ject Audio Systems
- Yaqin Ms-12b.:AAAVT SM-12B phono pre-amplifier [English]
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Dude, there's no way you'll be getting anywhere near 0.025% THD with a 48V supply.
Very nicely built, but aren't you gonna run into problems when driving 10K line level impedances? Your current sinking resistor on the follower output is 18K.
Please run some THD tests my guess is you're gonna be getting well over 5%, probably mostly 3rd harmonic looking at the topology. 0.1% is the maximum amount you should get for it to be hifi.
Very nicely built, but aren't you gonna run into problems when driving 10K line level impedances? Your current sinking resistor on the follower output is 18K.
Please run some THD tests my guess is you're gonna be getting well over 5%, probably mostly 3rd harmonic looking at the topology. 0.1% is the maximum amount you should get for it to be hifi.
THD is even better. See measurement below. Output impedance is 10k.
2d harm. = -39db
3d harm. = -52db
4d harm. = -68db
and the rest is below de noisefloor of -70db.
When i do my calculation, THD = 0.012%.
It is even better as before. I have changed the powersupply. First measurement had linear powersupply, this measurement had the cheap smps.
So the 6n28b is not a bad tube for low voltage phono stages.
2d harm. = -39db
3d harm. = -52db
4d harm. = -68db
and the rest is below de noisefloor of -70db.
When i do my calculation, THD = 0.012%.
It is even better as before. I have changed the powersupply. First measurement had linear powersupply, this measurement had the cheap smps.
So the 6n28b is not a bad tube for low voltage phono stages.
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39dB translates to 1.12% just for the second harmonic..
100 x 10^-39/20 = 1.12
The power supply won't really affect the distortion as most switching supplies are very well filtered + you've filtered the supply well towards the front end.
I don't think you can get good performance out of vacuum tubes at this voltage, it's just too nonlinear. Also 10K output impedance isn't great, that's a level loss of -6dB when driving a 10K load.
100 x 10^-39/20 = 1.12
The power supply won't really affect the distortion as most switching supplies are very well filtered + you've filtered the supply well towards the front end.
I don't think you can get good performance out of vacuum tubes at this voltage, it's just too nonlinear. Also 10K output impedance isn't great, that's a level loss of -6dB when driving a 10K load.
I think you do you calculation wrong, see wikipedia below.
I convert the db to Vrms and use the formula.
-39db = 0.01122 Vrms
-52db = 0.00251 Vrms
-68db = 0.000398 Vrms
-70db = 0.000316 Vrms
I also figured out the difference. My calculation gives the ratio and your the percentage. So i should not use the % symbol.
I convert the db to Vrms and use the formula.
-39db = 0.01122 Vrms
-52db = 0.00251 Vrms
-68db = 0.000398 Vrms
-70db = 0.000316 Vrms
I also figured out the difference. My calculation gives the ratio and your the percentage. So i should not use the % symbol.
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Removing the capacitors allows negative feedback via cathode degeneration. A step in the right direction.
If I were you I'd scrap the passive equalisation and work on getting the highest open loop gain possible then use a negative feedback eq network.
You really want higher supply rails. At least 200V.
Failing that just build yourself the standard all in one single opamp circuit with a correction pole.
If I were you I'd scrap the passive equalisation and work on getting the highest open loop gain possible then use a negative feedback eq network.
You really want higher supply rails. At least 200V.
Failing that just build yourself the standard all in one single opamp circuit with a correction pole.
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