Mini-Me phono preamp

After 18 years challenging myself, learning from you and sharing nice projects I will leave this forum.
Also because being bullied and get physical threads without support of the moderators for the last 18 years.
See you all on the next forum.

R.I.P by mod.
 
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The unbypassed cathode resistor in the MC amp is a concern because you are amplifying all of the cathode resistor johnson noise. (Most MC have very low internal impedances so you will be adding a lot noise relative to the cartridge's noise floor.) An LED for bias could eliminate this as a concern.

I have used a variety of MC cartridges over the past few years such as the ZU DL-103, DL-103D, and currently own three different models of Ortofon SPU. I use transformers and active devices for step up, gains have ranged from 8V/V to 32V/V depending on MC and phono pre.. Currently I am using 16V/V (sut) and 21V/V (ss active) - you may need more gain. The popular DL-103 has an output of about 300uV @ 5cm/sec to give you an idea. (You did not mention the MM section's gain or I missed it, so 12X could be fine..)

The project looks great, please publish some specifications. :D
 
Thanks for your reply.

As i mentioned i still must test the MC stage. But already in the MM stage the 6N16 surprised me with no noise at all.

The MM stage amplifies 400 times, with the MC stage that is 4800 times so you get more then enough output voltage. ( 2V output with Ortofoon 2M red).

About MC stepup transformers i do not like them at all, they sound dull and liveless compared to some active setups i listened to in Germany and the Netherlands at audio meetings. Until yet i like the pacific MC pre with the 2sk170 with battery power as best.

In Oktober I have the possibillity to measure noise and distortion, but by just listening they are very low for a tube pre.

5 Oktober there is a Phono pre shootout from the people of www.zelfbouwaudio.nl, the Dutch version of DIY audio. the Mini-Me also enters that competition, i am very curious what other people will say about the Mini-Me.
 
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I have had a lot of problems with suts myself, I find very low impedance MC will make fairly mediocre devices perform reasonably well. Higher impedances devices like the DL-103 imo are problematic with suts.

I use Lundahl LL1941in my main phono system (I currently have 2) and these are excellent with the SPU, but rather expensive.

I prefer a really good transformer to active, but I have found very few to like. I will say the amorphous core Lundahls are excellent. (LL1931/LL1941) Excellent HF extension, deep and well controlled bass, clean and very detailed presentation, balanced.

Will be looking forward to updates here, I'm sure the design will be well received.
 
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I will say the amorphous core Lundahls are excellent. (LL1931/LL1941) Excellent HF extension, deep and well controlled bass, clean and very detailed presentation, balanced.

I agree. When I first tried Lundahls I went for the lower priced silicon steel cores, didn't care for the sound much and wrote them off as industrial transformers looking for sales in the audio market. Then for reasons I don't remember I was persuaded to try their amorphous cored transformers and was surprised at the difference.
 
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This is the real problem with audio, the good stuff is expensive and most people are not willing to take the risk that a real improvement is to be had if they spend all of this extra cash. It has worked rather well for me, but I am careful, and stick to stuff where I think there is real engineering content, not marketing hype.
 
Today i did some measurements with a reverse RIAA circuit(+/-0.1db).
I like the results.
 

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Excellent result!

What is the tolerance of your reverse RIAA? My best one (commercial) is +/-0.1dB.

I'm too lazy to do this, but many audio test programs will allow you to run a generator sweep file with as many points as you can stand to calculate values for. (Probably write something for excel or the open office equivalent) This of course would remove the uncertainty of the reverse eq.

FWIW I've never thought it worth the trouble. :D
 
The reverse RIAA circuit is better then +/- 0,1 db. Beter then that i can not verify because my measure equipment is not better.

A lot of people use ARTA software with a good soundcard on the PC. They use then a inverse RIAA file.
 
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I did some more measurements.
But i do not know with one is good according the noisefloor.
Graf 1 = -78db
Graf 2 = -97db

There is also a graf with harmonics.
2nd harmonic = -50db
3nd harmonic = -60db

Graf 1
 

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Today i build one MC stage for testing purpose.
I discovered a fault in the PCB at the MC pre input, i shall correct that a.s.a.p.

I am very happy about the 6N16 tube. This tube has in the MC pre very little hiss, no humm, very little microphonics.

Here the specs i measured for the compleet Mini-Me with MC pre-pre.

Measurements with 100 Ohm at the input.

Amplication = 3000x
RiAA curve = +/- 0.5db
SNR = -77db
THD+N = 0.0244%
Channel separation = 47db

I did not use the Zener in the MC pre because there was no humm at all. I shall modify the schematic a.s.a.p.. For the heatersupply i used an extra LM7806.

I am very pleased:)
 

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