Pre Amp - BOSOZ Balanced Zen Line Stage.

[sadik]

Hi Friends,

My earlier thread was regarding Jean Hiraga 30 Watt Class A Amp & Protection Circuit for same. The Project is still under Process and it will still take time to complete.

Basically i really get board if i am just sitting idle. The only hobby i have is making Amplifiers, with home made Complete DIY PCB's & Speaker Enclosures.

It was really getting difficult for me to pass the time after office hours, when there is no other work to do, so i decided to make a Class A Pre Amp. While surfing i came across a very good Class A Pre Amp, You all may be familiar with BOZ & SOZ, this one is the Combination of both "BOSOZ".

It has Balanced Input as well as Balanced Output along with unbalance input & output. Below is the pdf link for same. Its the Design of Mr. Nelson Pass, I really respect this man & thank him a lot for his contribution towards DIY community.

https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=6&cad=rja&uact=8&ved=0ahUKEwjIrq6Ns-zPAhXLMo8KHYh9A2EQFggtMAU&url=http%3A%2F%2Fwww.firstwatt.com%2Fpdf%2Fart_bosoz.pdf&usg=AFQjCNGNQtEEGb8p0D0YMTS-lOMQ6Bsg-Q&sig2=WDP54Eq5CyIlDGuq20D7sg

I have started to built this Preamp for my incomplete Jean Hiraga. And i think this Pre Amp will get Completed before I complete Jean Hiraga. (Bhai investment bhi to low hai as compared to J-H .... )
Below is the PCB layout for Stereo Channel. The Size is 215 mm x 90 mm

I was unable to get 750 Ohm 3 Watt resistors locally, hence i have used 1.5k/2W Resistors in Parallel to get the Value 750 Ohms. (750 Ohm/3W resistors are available on elements 14 but are too costly) There are also some ODD values resistors like 221 Ohms, 22.1 Ohms, 124 Ohms, 4.75k, which I ordered from elements 14.

The Power supply is also as per the circuit diagram shown in literature. but instead on 2 transformers i have used 56-0-56 80VA transformer & Single Bridge Diode.

Below is the PCB layout for PS.(Size is 80 mm x 80 mm) Capacitor Polarity is wrong on "-" side which is to be Corrected in Layout.

Both The PCB's are Complete but i have not yet uploaded on my Drive, More Photos of Complete PCB's are coming Soon.

I also request you all to suggest me a good Tone Control Circuit Diagram for this Pre Amp. I would like to make the PCB myself so please do not refer for ready made kits. Is there anything like Class A Tone Control? Just asking.

Regards,
Sadik

 

[Audiodoc]

I have a boz works great for low level inputs but I prefer the pass b1 as most my sources are 2 mv or greater.bozsoz is a great preamplifier but you should add a good potentiometer or better still a discrete resistor based solution for best results.

 

[captrajesh]

I have a boz works great for low level inputs but I prefer the pass b1 as most my sources are 2 mv or greater.

Good input. How do they compare sonically?

 

[keith_correa]

I have a boz works great for low level inputs but I prefer the pass b1 as most my sources are 2 mv or greater.bozsoz is a great preamplifier but you should add a good potentiometer or better still a discrete resistor based solution for best results.

You should try the Radio Shack transformer solution to boost low levels. It works marvelously. I built it to hook-up my iPod to amp and the sound is near hi-fi. For the price, can't be beaten.

The $20 Passive iPod Preamplifier

 

[sadik]

I tested the Pre-Amp PCB with the Jean Hiraga Amp. (Source was Computer Audio) Sonic-ally i didn't hear any major difference apart from the Gain. It has a good Gain.

With or without this Pre-Amp the Sound Quality is some what the same. But with this Pre-Amp i got enough Gain which can Shake a very large Hall.

Below is the Photo of PCB during testing.

May be i am testing this kit with one of the best amp hence the difference of sound quality may be very little to get noticed by my ears.

Physical Testing Observations:
1. Heat Sinks do get hot and temp is about 60 Deg C, I will replace those heat sinks with Double the Height.
2. 1.5K/2W resistors also get hot. their temp is about 62 to 65 Deg C. These resistors i used as a substitute for 750 Ohm/3W resistors. (mentioned in 1st Post)
3. The Pre-Amp was tested for around 5 to 6 Hours. The above temp reading was taken after 10 minutes after Powering the Pre-Amp & this temp was constant after 5-6 Hours of running.

Friends, your suggestions & opinions are welcomed.

Regards,
Sadik

 

[Audiodoc]

Most of the sources these days don't need much gain in a preamplifier. The use of preamplifier these days is primarily for impedance matching, source selection and a good volume control for all your power amplifiers or monoblocks. I love the pass b1 more than the boz any day as none of my sources are low level.

 

[jls001]

To my ears, DCB1 sounds even better than the stock B1. In fact I would venture to say there's a substantial jump from B1 to DCB1.

@Sadik: what you're doing is the purest form of DIY. Keep the flag flying high :thumbsup: I also want to learn how to design boards so that I can build from scratch some of the interesting, simpler designs I keep coming across.

 

[manniraj]

+1 to Jls001, many of us have only used predesigned boards for DIY but only very few have designed their own, nice going :clapping:

 

[sadik]

Thanks JLS & Manniraj for your appreciation ... I also want to built some good Tone Control, If you have any good circuit to share please let me know.

The Enclosure for this Pre-amp will also be a Complete DIY hand made except for Front and Back Face Plates which will be made from acrylic sheet, these face plates will be laser cutted according to size & will have engraved graphics / logo & fonts on it.

Sadik

 

[jls001]

A couple of interesting tone control designs:

1) Douglas Self: Anyone built/listened to D Selfs precision preamp. - diyAudio

I believe the Self design is a Baxandall.

2) Rod Elliott: Hi-Fi Preamplifier

Both are highly reputed designers.

 

[Audiodoc]

The norge 1000 and 2060 uses the rod elliot design which is good uses opamps and gives subtly different sound signatures with opamps rolling. You can try building a parametric equalizer or a multi band equalizer which would be better than using simple tone controls. I have made some boards using designs from elektor electronics back in the 90s and they worked better than simple tone controls.
Those were the days when I used to do pcb design using ferric chloride and ohp markers.

 

[doors666]

To my ears, DCB1 sounds even better than the stock B1. In fact I would venture to say there's a substantial jump from B1 to DCB1.

@Sadik: what you're doing is the purest form of DIY. Keep the flag flying high :thumbsup: I also want to learn how to design boards so that I can build from scratch some of the interesting, simpler designs I keep coming across.

B1 is very sensitive to a good power supply, while dcb1 is not. That would be one of the reasons for dcb1 sounding so much better, and of course there is that extra cap at the output.

 

[sachu888]

B1 is very sensitive to a good power supply, while dcb1 is not. That would be one of the reasons for dcb1 sounding so much better, and of course there is that extra cap at the output.

I am sorry, but commercial version of B1 comes with a simple wall wart adapter FIRST WATT B1
NP says its not at all sensitive with power supply, whereas people reported DCB1 sounds better with Salas shunt regulator.

Regards
Sachin

 

[doors666]

I am sorry, but commercial version of B1 comes with a simple wall wart adapter FIRST WATT B1
NP says its not at all sensitive with power supply, whereas people reported DCB1 sounds better with Salas shunt regulator.

Regards
Sachin

B1 uses a single rail supply of 0-20v. Two resistors are used to bias the B1 at 10v. These two resistors will bring the psu junk into your signal, and this being a buffer, it will pass that junk as it is to your output. DCB1 does not have these resistors as it uses a dual supply.

Why would dcb1 sound so much better than a b1. The only other difference in both the designs is the outout cap and that should not make so much of a difference, people have tried really awesome caps with the b1. If dcb1 can benefit from a shunt reg, why would the b1 not get the same benefits.

Try to put a good supply to a b1 and see the results. I havent tried with my b1 as i made a dcb1 with shunt reg (see my bumblebee design) and the b1 is gathering dust. That reminds me that I still need to increase the current on that shunt reg

 

[hifiramr]

Please look on New Aikido 12Vac PCB and part kits

Akido 12v ac which is far superior than B1 in all ways.My first preamp build was B1.Also Nelson pass BA3 which is also a very good option.DCB1 will be always better as it have a unity gain B1 is no gain also it better with salas shunt regulator.You can check the thread on diyaudio forum

 

[sachu888]

B1 uses a single rail supply of 0-20v. Two resistors are used to bias the B1 at 10v. These two resistors will bring the psu junk into your signal, and this being a buffer, it will pass that junk as it is to your output. DCB1 does not have these resistors as it uses a dual supply.

Why would dcb1 sound so much better than a b1. The only other difference in both the designs is the outout cap and that should not make so much of a difference, people have tried really awesome caps with the b1. If dcb1 can benefit from a shunt reg, why would the b1 not get the same benefits.

Try to put a good supply to a b1 and see the results. I havent tried with my b1 as i made a dcb1 with shunt reg (see my bumblebee design) and the b1 is gathering dust. That reminds me that I still need to increase the current on that shunt reg

I have discarded my B1 long back,so I don't remember the sq. I know at least 3 members on this forum, prefer B1 over DCB1. One of them is using it with original Salas shunt. They say DCB1 SQ is on the face and narrow soundstage than B1.
Your power supply is very good. I had a discussion with Joshua. Its an improvement over LM317/337. I would definately try it for me.

Regards
Sachin

Please look on New Aikido 12Vac PCB and part kits

Akido 12v ac which is far superior than B1 in all ways.My first preamp build was B1.Also Nelson pass BA3 which is also a very good option.DCB1 will be always better as it have a unity gain B1 is no gain also it better with salas shunt regulator.You can check the thread on diyaudio forum

Both DCB1 and B1 are unity gain. You are comparing Aikido( preamp) with B1( buffer) not counting the cost. B1 and DCB1 can still be used with Aikido and it might sound better in some cases.

Regards
Sachin

 

[hifiramr]

Sachin yes my mistake both are unity gain.Now coming to cost of Akido and B1 its not that huge when you compare the sound signature Akido is far far superior in all aspects.For the akido kit you need only a 12V ac supply that is its beauty.The entire Kit will cost no more than 15K including transformer.For B1 you need a better power supply which is not cheap at all.B1 is a good buffer I dont think beyond it cannot be compare with very well designed preamps like BA3.JC2 etc

 

[sadik]

Today's Progress...

Mounting of PCB's, Transformer and Diode is complete on Base Plate. I will be out of station for a couple of days so there will be no updates for a while. I will complete the Project as soon as I am back.

Sadik

 

[hifiramr]

Looks great

 

[sadik]

Hi Friends,

I am Back to Pavilion i mean home. Due to Diwali the market will remain closed till Sunday, from Monday all shops will open here. Meanwhile i got the Feets machined. Below is the Pic.

In the Bottom groove a neoprene / rubber "O" ring will be fitted for better grip & this feets will be Black / Silver Anodized depends on which color of Anodization will be in process.

Sadik