Mini-Me phono preamp - diyAudio
Go Back   Home > Forums > Source & Line > Analogue Source

Analogue Source Turntables, Tonearms, Cartridges, Phono Stages, Tuners, Tape Recorders, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 21st September 2013, 01:15 PM   #1
Koifarm is offline Koifarm  Netherlands
diyAudio Member
 
Koifarm's Avatar
 
Join Date: Aug 2005
Default Mini-Me phono preamp

Dear DIYaudio community,

I like to share this small design from me called Mini Me phono preamp. Last week I have completed the current version that I use.

Click the image to open in full size.

It is a three part design with 6N16 miniature tubes. First part is a MC pre-preamp, second part is a MM impedance selector and the third part is the MM preamp with RIAA correction. I have designed a PCB that you can split if you do not need some parts. For the power supply there is also a PCB design.

Click the image to open in full size.

Schematic

Looking at the schematic, the first triode(V1a) amplifies the signal 16x, after that R15,R24,R25 and C8 reduces the high tones according to the RIAA curve. The second triode(V1b) amplifies the signal also 16x, after that R10,R11 and C5 take care of the lower tones(bass) according to the RIAA curve. The third stage(V2a) just amplifies 16x, followed by a buffer stage(V2b). The total amplification factor is about 350x. That is 16x16x16x0.9 amplification for the tubes divided by 10 for the RIAA correction.

In front of the MM phonostage I like to use a impedance selector. This way I can easy optimize the loading for the MM cartridge. If you do not like to use it you need to use R1(47k) otherwise do not use R1.

The MC pre-preamp is an extra, it has a amplification factor of 9x. This stage I have not tested yet because I do not have a MC cartridge.

The power supply is pretty straight forward design. There is no noticeable hum or noise.

PCB design

Click the image to open in full size.

Click the image to open in full size.

download the PCB film files below,

http://www.monstercore.nl/6n16phono.pdf

http://www.monstercore.nl/6n16phonopower.pdf

RIAA correction

I did some measurements according the RIAA correction.

Click the image to open in full size.

The specs of the MMstage

Amplication = 350x
RIAA curve = +/- 0,5db
SNR = -78db
THD+N = 0,0135%
Channel separation = 47,3db

And with the MC pre,

Measurements with 100 Ohm at the input.

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

I hope i have inspired some people to build this MM phono stage to.
Do not hesitate to ask me any questions.

Ronny

Last edited by Koifarm; 14th May 2014 at 02:47 PM.
  Reply With Quote
Old 21st September 2013, 07:17 PM   #2
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
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.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 21st September 2013, 08:02 PM   #3
Koifarm is offline Koifarm  Netherlands
diyAudio Member
 
Koifarm's Avatar
 
Join Date: Aug 2005
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.
  Reply With Quote
Old 21st September 2013, 08:26 PM   #4
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
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.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 22nd September 2013, 12:42 AM   #5
diyAudio Member
 
Join Date: Jun 2008
Quote:
Originally Posted by kevinkr View Post
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.
  Reply With Quote
Old 22nd September 2013, 01:45 AM   #6
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
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.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 23rd September 2013, 07:05 PM   #7
Koifarm is offline Koifarm  Netherlands
diyAudio Member
 
Koifarm's Avatar
 
Join Date: Aug 2005
Today i did some measurements with a reverse RIAA circuit(+/-0.1db).
I like the results.
Attached Images
File Type: jpg image.jpg (194.1 KB, 142 views)

Last edited by Koifarm; 23rd September 2013 at 07:08 PM.
  Reply With Quote
Old 23rd September 2013, 07:10 PM   #8
Koifarm is offline Koifarm  Netherlands
diyAudio Member
 
Koifarm's Avatar
 
Join Date: Aug 2005
The reverse RIAA circuit in used.
Attached Images
File Type: jpg image.jpg (35.4 KB, 234 views)
  Reply With Quote
Old 23rd September 2013, 08:39 PM   #9
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
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.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 24th September 2013, 09:37 AM   #10
Koifarm is offline Koifarm  Netherlands
diyAudio Member
 
Koifarm's Avatar
 
Join Date: Aug 2005
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.

Last edited by Koifarm; 24th September 2013 at 09:39 AM.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Phono Preamp PCB wanted - Transcendental Sound Grounded Grid Phono Preamp nathanjh13 Analogue Source 0 14th June 2012 11:19 AM
6112 and 6111 Mini-preamp TV7 Tubes / Valves 25 22nd December 2011 11:58 PM
FS: Mini headamp/preamp/buffer boards theAnonymous1 Swap Meet 1 26th November 2008 01:39 AM
new phono stage or old preamp with phono? flohmann Analog Line Level 2 2nd October 2008 10:51 PM
Electret mic preamp - will phono preamp work? darthmullet Analogue Source 6 12th October 2007 08:32 AM


New To Site? Need Help?

All times are GMT. The time now is 09:02 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2