A Lab PSU (Power Supply)

Two years I was wondering which Laboratory Power Supply to buy. I looked over Agilent and some Musteks, but most of them are expensive for me.

Now I decided to build one functional and cheap. What I do need:

- 3A max current
- 0-30V variable voltage
- variable current

Here is the choosen schematic. After reading on the forum I saw that the schematic has big issues fortunately a friend from out Bulgarian Audiophille Forum has made good work and I just got his PCB error free.
This is his website go and check the real deal

I added a termocontroller with a fan because the module can quickly overheat with this small sink I have for the main power transistor if you push it a lot.

Enjoy!

How to calculate crossovers for speakers

While making my Custom Speakers (inspired by Lampizator's Endorphine 17 project) I was wondering how to calculate the crossovers.

I read a lot of theory, downloaded a bunch of programs, etc., but finally I came to the conclusion that the simplest crossover works best and I will describe you how you can make it by yourself.

First you need to find out the impedance of your speakers. Mine are 5Ohm Saba pairs, so I will make the example calculations based on that.

1) For tweeter you can put a capacitor in series which will form a first order High Pass filter which have to cut off frequencies below ~8kHz-10kHz (above those most midrange drivers became weak). In my case this is a 3-4uf capacitor. I choose 3,3uf capacitor.

You can use this calculator to find out what capacitance will suit in your case:

http://sim.okawa-denshi.jp/en/CRtool.php

2) For midrange you need to make a Band Pass filter, so you can cut the low frequencies where the midrange driver is weak and the very high where it is also becoming weak and the tweeter will support it.

For Saba midrange driver these are below 300-400Hz and above 9-10kHz, so I needed a coil to filter high frequencies and a capacitor to filter very low frequencies - all put in series to the driver.

In my case this is a 0.39mH (mili Henry) coil and a 100uf capacitor. The 0.39mH coil start to cut off frequencies above 2kHz but with decent step so it can match to the tweeter filter correctly at ~9kHz.

And the 100uf capacitor will cut off everything below 318Hz, which is pretty fine.

Here is a band pass calculator which will show you all the curves:

http://sim.okawa-denshi.jp/en/RLCtool.php

More straight forward calculator for the High Pass part of the Band Pass filter: http://sim.okawa-denshi.jp/en/CRtool.php

And a straight forward calculator for the Low pass part: http://sim.okawa-denshi.jp/en/LRtool.php

3) Now we come to the bass section. The goal is to support the midrange. You can use any 12" or 15" speakers here. I choose Saba 10" 5Ohm because my room is pretty small and I had a bass extension boxes (without back wall of course!).

So let's see how we can cut off everything above 300-400Hz with a Low Pass filter (passes everything below the cut off frequency)

Here we have to be more aggresive that's why we will use a Second order Low Pass filter which consists of a coil in series to the driver and a capacitor connected to the ground.

I went with a 4mH coil (because of the price) and a 10uf capacitor. I could use a 50uf capacitor so I can get a 350Hz cut off frequency, but since I use a 10" bass speaker it is a little big weaker than 12" ot 15", I decided to go to higher cut off frequency so I can compensate the small bass speaker size.

But you should definitely make your calculations in a way that you cut everything above 300-400Hz if you have bigger bass speakers.

This is the calculator you can use: http://sim.okawa-denshi.jp/en/RLClowkeisan.htm

*) remember you have to connect bass speakers with reverse polarity! So they can cancel each other with the midrange driver where they overlap, e.g. minimize unwanted destructive acoustic interference in the frequency region covered by both woofers and main/midrange speakers.

Here is my crossover as a final schema.

Coils have to be with low resistance (2-5Ohm). I use Jantzen Audio coils - C-Coil for bass and Wax Coil for midrange - http://jantzen-audio.com/html/coils.html. Very very good coils from Danmark!

Final advice - do not use electrolytes. Buy PIO or Polypropilene capacitors. They are much better and you will hear the difference. Even if you use old russian PIOs (Paper In Oil).

Chinese Obbligato http://www.partsconnexion.com/capacitor_film_obbligato_oil.html and http://www.partsconnexion.com/capacitor_film_obbligato_psu.html are very good.

If you have a small budget you can go with electrolytes, of course, but do not forget that the signal wire have to be connected to plus (+) side of the electrolyte capacitor.

Starting a Headphones Tube Amp project

A month ago I found 4 tubes 6n1p in my stuff, so I decided to use them. But what's the best thing you can use 4 russian tubes - of course, a headphone amp. And I do need one now since I am listening to music on headphones almost 5-6 hours per day.

I found a pretty good schematic for 6n1p headphone amp here (http://gilmore2.chem.northwestern.edu/projects/showfile.php?file=bender_prj.htm) by Bruce Bender.

I ordered all parts that I was missing and here are they.

Like most people I need my drug to get some inspiration and motivation for work - Jelibon beans. :)

I made the power supply for heaters and anodes.

These are the 3 x 6n1p tubes. They are small but should be efficient.

Kenwood KA 1100D

I would like to present you one of the best transistor amplifiers - the mighty Kenwood KA 1100D.

As a friend of mine said "It is the Cadillac of Kenwood's amps during 80s".

It has a very, very good phono preamp and desent sound compared to most of the good tube amps.

Inside view.

You can see 4 big Elna capacitors here - total capacitance 60 000uF!

If you can get one - do not hesitate! It's a perfect solid state amplifier!

Modding/Upgrading Marantz CD50 - part 5

Other mods to this player:
part 1
part 2
part 3
part 4

part 5 (this paper)

Download PDF - TDA1541A reclock/DEM clock

Almost a year since my last mods to this Marantz player, yesterday I came up with new ideas about it.

Here's what I decided to do and deep listening test after every mod step by step I confirm here only those that really do change the sound to a even higher level than before.

1) I removed the crappy Nichicon Muse 22uf output capacitors and put perfect Ampohm 4.7uf Polypropillene capacitors directly to the output RCA sockets.

Here you can use every PIO (Paper In Oil), polypropillene, styroflex capacitor with value between 1uf and 10uf.

Please do not use old russian ship container like caps or the small ceramic caps.

2) I had some Blackgates 100uf-470uf/25V and put them everywhere - around DAC, around digital chip, around opamps. They make the best sound for opamps in matter of not distorting the signal in any way. I've tried Nichicon Muse, Elna Silmic II, etc. but they all put some of their taste to the sound and I do not like that. I wanted pure, flat, without distortions capacitors and these are only Blackgates.

3) Variable output board was removed. It uses the +/-15V from the power supply which are used by the TDA1541A DAC and opamps, so this step will relieve a little bit the PSU.

4) For opamps I decided to switch to LM4562HA. They are really good!

5) Before the main 7805 regular in the PSU I decided to put in ~20000uf capacitance.

The rule of thumb says that if you drawn 1A of current you need at least 20000uf capacitance so you can filter perfectly the 50Hz/60Hz noise from the main line.

Here we do not have such currents, although I decided to put 7 x 3000uf caps in parallel forming 21000uf multicap

6) All diodes was change to schottky ones. Schottky are smoother. You have to change all diodes in the played so you can hear a real difference. Changing only one rectifier won't have any effect you can hear.

7) After all regulators (7805, 7806, 7815, 7915) I put 2x the original capacitance tantalum capacitors (yellow ones on the pictures below)

8) I removed all small 100nf ceramic SMD capacitors on TDA1541A's decoupling pins and then I put 0.47uf WIMA. You really have to remove the SMDs first! Believe me!

9) Have you read about DEM clock for TDA1541A? It's time! You should read THIS PDF.

After that just change the capacitor between 16th and 17th pins for 120pf/1% tolerance one and you will be amazed.

Here are some photos during these interventions.

Multicap bank of 7 x 3000uf/16V put before the main 7805 regulator.

0.47uf Wima caps on the 14 decoupling pins of TDA1541A. You see the little blue cap of 120pf for DEM lock.

Upgraded capacitance to 6600uf before 7815 regulator.

View of the whole player with clock, main line AC RFI filter, all Blackgates, big 21000uf caps bank, etc.

The great output Ampohm 4.7uf capacitors.

Some Blackgates.

More Blackgates for the digital filter chip.

Main capacitor bank installed in the player.

AC RFI filter. Very, very important! And costs only 8EUR.

That's it for now!

I am very pleased with my last upgrades to this player.

What's comming:

* +/-15V PSU low noise, low impendace for DAC and opamps

I will try one of these:

- Jung, Sulzer, D44H11 - regulator designs

- shunt regulator:

http://www.diyaudio.com/forums/digital-source/201057-marantz-cd-50-cd-60-tda1541-cdm4-19-a-12.html

http://img21.imageshack.us/img21/3240/shunt.jpg

http://www.acoustica.org.uk/t/3pin_reg_notes4.html

*) Please, do not bother saying that it looks awful. I know. It's a test player for different type of mods, so I do not care for the look. I just want to hear if something is worth the effort applying in my primary player and/or some player of a friend.

Shure V15 Type III - Wonderful Turntable Cartridge

Today I received my "new" Shure V15 Type III cartridge for my Lenco L75 turntable.

After inspecting the stylus (it's hiperelliptical! A perfect diamont shape for great analogue sound) I saw minor traces of wear.

I went for careful cleaning the tip because after a dozen of hours listening it usually gets carbon deposits from the dust in the records' grooves.

And ... miracle! The tip now looks very, very good ... near perfect!

Shure cartridge mounted on the Linn Basic LV V tonearm

Shure V15 Type III in all it's glory!

If you wonder what should be the next cartridge you have to try on your turntable - go for Shure V15 Type III!

Its fantactic sound deserves every penny.

Enjoy!

Open Baffle Speakers - Finished!

In May 2011 I wrote that I am going to build my first Open Baffle Speakers with Saba drivers.

Now six months later I have finished my first speakers' project and I am very very glad.

I choose the Open Baffle design for it's simplicity but added a bass extender. It works great!
Cross over is very very simple and effective. Here's the schema:




Left speaker



Right speaker


Open Baffle in its glory!








Speaker's body after painting and polishing




Back side after wiring speakers and crossover


Bi-wiring to the amplifier


My final decision: the best speakers I have ever had under 500EUR!

They sound like new 3000EUR Jamo and maybe better clarity.

Yes. That's right! :)