Archive for February 28, 2014

Music and Audio Chain

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There were many discussions about what is the most important component in the music reproduction audio chain. I won’t get into that, we know everything is important but the better question i think is when starting an audio system what components should come first? Where should the investment start?

In my opinion, loudspeakers bring the greatest change in a system and therefore it seems the best choice of a first investment. The sonic differences are clear and the quality of reproduction can have a drastic increase when upgrading to real speakers.

So you want to build a better audio system and you set aside a specific budget for it. You are thinking perhaps to split it to get a good source (record player, cd player, reel to reel tape deck), a good amplifier and a good pair of loudspeakers. This would be a great way to do it if you have a really big budget. Most often than not tho that is not the case. With a limited amount of money at hand i would say to first invest it in a pair of loudspeakers. Especially if you still have an old amplifier and source from previous systems. You can use the new speakers in the old system for a while and still benefit greatly from the increased quality of reproduce sound. Then put aside money again and get the best amplifier to drive the speakers and then save more money and get a good source.

Then reason behind this way is that sources are more abundant. With the availability of high resolution formats you can live with PC-based sound for a while until you save for your favorite source. You can still enjoy better reproduction than your old system as opposed to getting a great record player and using less than good speakers.

With great speakers you immediately feel the increase in performance and this will give you a good feeling that you made the right investment. Money don’t come easy so you will look for an excuse in spending the money. Hearing the difference in sound will make up for that I’m sure.

Starting from the other end of the audio chain might not render such a big difference and you might loose confidence in spending money to upgrade your system.

When choosing components don’t hurry. Excitement can get you to take rush decisions, believe me, i know. Study, do your homework, go to audio expos listen and try out as many products as you can. Take notes, keep a record of what you hear, what you like, what you don’t, what surprised you, features and specs of anything you hear. Don’t rely on your memory. You will soon find out you like a certain type of sound and you will have a list of products that meet your requirements.

Hope it helps and thanks for visiting

[Project Ryu] Ryu Spiders

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A spider for high X-max drivers.

The progressive spider allows for higher excursion. Used with Ryu concept it can have high X-max and keep good linearity of stiffness.

Here is a picture.

Project Ryu Speaker Spider

Balanced Line Attenuator バランスラインアッテネータ

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Hello,

In a home recording environment equipment often doesn’t come in a large variety because of either limited budget or limited space… or both. I am presenting here an balanced attenuator which comes in between fixed gain preamp and recording device/soundcard.

The purpose of this device is to adjust the level and monitor it to prevent saturation of the next stage in the recording chain. It uses a L-pad followed by a balanced buffer stage. The attenuation steps are 0dB, -3dB, -6dB, -9dB and -12dB.

The meter section uses a microcontroller with a 10 bit ADC. It monitors both polarities of the signal and detects the peak within a frame of 1000 samples. ADCs samples the signal every 12us.

Balanced line attenuator schematics バランスラインアッテネータ

 

In the schematics above J7 will be used later on future revisions to indicate symmetry in the balanced signal.

J3 will connect the attenuation selector.

There are certain modifications i did the initial schematic tho. R7, R8 must be of greater value. At least 100k. With 100k you will get a -0.8dB signal at 0 dB setting.

The circuit is pretty straightforward, you can use any quad opamp chip for U3 as long at it operates from a 9V single supply. I do recommend a FET input opamp if R7 and R8 >= 100k as they tend to have lower noise than bipolar with high input impedance.

U2 i used a LM324 as it allows operation at 5V single supply. U2:C is used to bias the ADC inputs at 2.5V.

I will explain how to rectify the signal with a PIC in a future project but you will find the hex file for this one at the end of this article.

Here are the PCB drawings:

バランスラインアッテネータ Balanced Line Attenuator

pcb top layer

バランスラインアッテネータ Balanced Line Attenuator

pcb bottom layer

Balanced Line Attenuator バランスラインアッテネータ

pcb top silk

 

Warning: NONE of the PCB images are mirrored!

Here is how the PCBs turned out:

Balanced Line Attenuator バランスラインアッテネータ

Balanced Line Attenuator バランスラインアッテネータ

Balanced Line Attenuator バランスラインアッテネータ

Balanced Line Attenuator バランスラインアッテネータ

I used a rotary switch to select the attenuation levels. For 0dB you can just omit R15. Use POT2 to calibrate 0dB on your meter. I usually set it to 0dBV.

Balanced Line Attenuator バランスラインアッテネータ

Balanced Line Attenuator バランスラインアッテネータ

 

After building the first unit i made some measurements. I used 5% tolerance resistors so i wanted to see if the attenuation levels are correct. Here are the results:

Balanced Line Attenuator バランスラインアッテネータ

 

-6dB and -12dB settings are about 1dB off and it seems -3dB setting is also a bit off. For -12dB i soldered a 47k resistor in parallel with the 6k8 one and for -6dB i soldered one 100k resistor in parallel with the 22k. For -3dB i soldered a 470k resistor in parallel with the 47k one. Results were much better:

Balanced Line Attenuator バランスラインアッテネータ

 

I will be making kits available for this device with PCBs and programmed microcontroller as well as fully built units. Please subscribe to receive more details about this offer in the next newsletter.

Below you can find the hex file:

PrjRyu Balanced Attenuator

Thank you for visiting

 

Monitoring Amplifier モニターアンプ P4: VU Meter Driver

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Hello, こんにちは,

In this part I will continue with the VU-meter driver for needle instruments. The circuit is very simple just a half-wave rectifier with adjustable gain and a comparator for clip indicator.

POT3 should be chosen to match your meter’s sensitivity but i think 100k will do for most. Components are not critical so it should be fairly easy to build.

Whats important to note is that the voltage at the inverting input of the LM339 comparator will set the clipping threshold, so you can use a voltage divider there to set it to what you want.

You will need to adjust POT3 to your preferred 0dB point, I usually use the dBV scale.

vu meter schematic

Monitoring Amplifier Vu meter circuit アンプVUメーター回路を監視する

Monitoring Amplifier Vu meter circuit アンプVUメーター回路を監視する

 

Monitoring Amplifier Vu meter circuit アンプVUメーター回路を監視する

 

Slowly but steady the whole unit is coming along. In next part i will do the source selection and front end.

Parts List:

Quantity: References Value
3 R1, R3, R5 10k
1 R2 1k
1 R4 680-1k
1 C1 10u
1 C2 3.3u
1 U1 TL072
1 U2 LMV339MT
1 D1 1N4148
1 D2 LED
1 J1 CONN-SIL3
1 POT1 10k
1 POT2 4.7k
1 POT3 100k-470k

Thank you for visiting