Hi-Fi audio preamplifier using Burr-Brown PGA2310

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philip davies
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Re: Hi-Fi audio preamplifier using Burr-Brown PGA2310

Post by philip davies »

Hi Fotis,

I've had a look at your schematic for your preamplifier. i thought i would ask where did you obtain the panasonic encoder?

I can't wait to try it on real hardware and see it work for real. Are you using an LCD display for your project?

Thanks again for your kind help

Phil

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Re: Hi-Fi audio preamplifier using Burr-Brown PGA2310

Post by fotios »

I've had a look at your schematic for your preamplifier. i thought i would ask where did you obtain the panasonic encoder?
I bought Panasonic encoders from an eBay store located in USA, here the link: http://www.ebay.co.uk/itm/170645192579? ... 1423.l2649. Be carefull, the price of 8.31GBP is for 4 pieces so each encoder costs 2.08GBP; that is a very good price. I allready tried the encoder and is perfectly working. The other option is to I send you an encoder (i have 3 pieces left over) for free.
I can't wait to try it on real hardware and see it work for real. Are you using an LCD display for your project?
Of course i am using LCD display. I bought two pieces (2X16 backlight, blue background + white leters) from two different eBay stores. Both are working just fine. Here the link of the one seller: http://www.ebay.co.uk/itm/130542960619? ... 1439.l2649 Amazing price, i bought for fun but... is working!
Here the link of the other: http://www.ebay.co.uk/itm/170640298624? ... 1439.l2649

Fotis
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Re: Hi-Fi audio preamplifier using Burr-Brown PGA2310

Post by philip davies »

Hi fotis,

I did manage to obtain the panasonic encoder off ebay and I now also have the alps encoder that i bought from farnell. For the display I am going to try a VFD display (2X16 LCD compatible) and I also have an LCD display which has a blue back light and white font, might try both to see which one will look best :)

Hope your pre-amp is coming along nicely :D

Thanks for your help

Phil

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Re: Hi-Fi audio preamplifier using Burr-Brown PGA2310

Post by fotios »

Hello
Attached is the schematic of the analog section of preamplifier. Four top quality buffers (LME49710) are used to isolate the PGA2310 from inputs and outputs. The buffers are configured as voltage followers (i.e. Av = 1) which ensures the maximum ability of LME49710 in bandwidth (GBP). In the feedback loop of each buffer I added a resistor and a compensation capacitor. These components may eventually not be needed; the reason is that I have not tried these OPAs so far. I will know this only when I will test the actual circuit with real instruments on the workbench. For this reason I have marked these parts as optional. On the same board are mounted the relays, five for INPUTS and one for MUTE. Control lines of relays will be implemented on a separate board soldered vertically to the main board in order to avoid a messing of digital and analog lines which can cause interference on audio signal. For the supply of analog section, I have selected LM317 - LM337 adjustable voltage regulators, which under the given circuitry can provide better PSRR from the ordinary 7815 – 7915 fixed regulators. Another one reason is that with a supply of +/- 15.5 to +/- 16 Volts (obtained only from adjustable voltage regulators) LME49710s can provide their top performance in THD+Noise and Dynamic range (please take a look on NSC LME49710 or LM4562 datasheet). The circuit is mounted on the same board with OPAs. If cables were used, their straight capacitance could derate the exceptional PSRR (Power Supply Ripple Rejection) of the given voltage stabilization circuit by turning back the ripple of power supply.
Thanks for your attention
Fotis
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PGA2310 PRE AMPLIFIER 1.pdf
(30.44 KiB) Downloaded 563 times
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Re: Hi-Fi audio preamplifier using Burr-Brown PGA2310

Post by philip davies »

Hi Fotis

Hope your pre-amp is coming along nicely :D

I've been having a bit more of a play with the software and I've had a little idea, how difficult would it be to add another menu in order to select between 2 different Record outputs?

Let me know what you might think of this idea :)

Phil

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Re: Hi-Fi audio preamplifier using Burr-Brown PGA2310

Post by fotios »

Hi to all of you, my good friends
After a long interval - we have big troubles here due to the famous Greek economic crisis - i came back. I completed the 2 main pcbs of preamplifier, it remains just one for the mounting of power supplies, i hope this week will be finished. Then i will have to modify a little the code and to do some audition tests and measurements of the final project. Pcbs are home made, i attach some pics. If you need advices of how you can make diy pcbs at home, please don't hesitate to ask me.
Thank you for your kindness and for your comprehension. I have not words to express my gratitude in all of you. I ask your forgiveness for my absence so long.
Fotis
Attachments
PGA2310_pre4a.jpg
PGA2310_pre4a.jpg (200.72 KiB) Viewed 12350 times
PGA2310_pre3a.jpg
PGA2310_pre3a.jpg (173.36 KiB) Viewed 12350 times
PGA2310_pre2a.jpg
PGA2310_pre2a.jpg (226.55 KiB) Viewed 12350 times
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Re: Hi-Fi audio preamplifier using Burr-Brown PGA2310

Post by medelec35 »

Hi Fotis,
Nice to see you back on the forums, we have missed you!

Sorry to hear about the problems over there :(

Your PCB looks so professional, I would love to be able get my pcb''s to look even 1/2 as good as that, then I would be happy!

I'm sure advice on PCB making will go down very well (for me any way :P )


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Re: Hi-Fi audio preamplifier using Burr-Brown PGA2310

Post by fotios »

Hi Martin
Thank you so much friend for your kind words. I feel better today, after my coming back to all of you :D I will try - in spite of those economic headaces - to be most frequently near you, indeed this forum is a big consolation for me!
As for PCB production at home, have you any good idea of where i can open a related thread? Maybe in "Electronics Products forum"?
Have a nice day
Fotis
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Re: Hi-Fi audio preamplifier using Burr-Brown PGA2310

Post by Steve »

Hi Fotis,

Yes - a post on DIY PCBs would be a good idea. And the "Electronics Products" forum is as good as anywhere.

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Re: Hi-Fi audio preamplifier using Burr-Brown PGA2310

Post by philip davies »

Hi Fotis

It's very nice to hear from you again on this forum :) haven't been on here for a while myself.

Glad to see pictures of your preamp, your circuit boards look extremely professional. I have to agree with the idea of opening a new thread in the "Electronic Products Forum" regarding PCB production at home, I think this would be a very good idea and i would personally find it very helpful, and I'm sure others would to.

It's only now that I have had the time to finally build this project on actual hardware. I have all the parts necessary to build the digital part of the project, so I'm going to put it all together and see how it works with the vfd display I have.

Have a good day

Phil

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Re: Hi-Fi audio preamplifier using Burr-Brown PGA2310

Post by fotios »

Hi Phil
Glad to hear you after so long time. I am on the way to finish the last PCB, this of power supply. Just now i finished the drilling of holes. It still remains to i make the bottom, front and rear aluminum panels to mount pcbs, sockets etc. At the end, i will modify the code to suit in 5 inputs.
As for home made pcbs, i will try to open this thread as soon as possible.
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FlowCode V5: Hi-Fi audio preamplifier using Burr-Brown PGA23

Post by fotios »

Hi to all
I did my upgrade to FC v5. First thing that i did was a test of this project using the new version.
FlowCode v5 works nicely in a so complex project, that includes two different interrupt sources, the PortB or IOC interrupt and the RB0 (from now the RC5 receiver interrupt) interrupts. I also tried on actual hardware with success. Small corrections on my program structure needed, to avoid possible "software stack corruptions" (though i had no problem) as indicates the compiller.
The most important thing is that i have not noticed any mistake of FC5 during simulation. It offers nice new additions, like an error message if we forgot to initialize a variable (i had two such uninitialized variables, of which no one is mentioned using FC v4.5) . PortB interrupt also is - from then - simulated at each pin of PortB (in previous versions, just from RB4 - RB7).
Compiller, Linker, Assembler also work correctly during programming proccess. Nice addition on "Compiller messages" also. I checked the project on actual hardware, and it works correctly. Here the project, you can simulate it:
Attachments
PGA2310preamp_Panasonic_RC5_v5.fcf
(189.78 KiB) Downloaded 272 times
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Re: Hi-Fi audio preamplifier using Burr-Brown PGA2310

Post by philip davies »

Hi Fotis,

Nice to hear that you have tried the fcf file on actual hardware. I've also tried your last fcf file that you modified using FC v5 and it works grate with my test PCB that I put together last week :D . At the moment the display can start to do some weird things, for example sometimes random letters or numbers start to appear or the display starts to fade and then come back to life. This might be down to the VFD display that I am using, although the manufacture assures me that its compatible with LCD commands. I will try a LCD display that I have going spare tomorrow and maybe shorten the length of the wires that go from the test PCB to the display as it could be picking up interference or even induce capacitance and resistance.

Have you tried your pre-amp in your audio system yet? if so, how does it sound?

Best Regards

Phil

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Re: Hi-Fi audio preamplifier using Burr-Brown PGA2310

Post by fotios »

Hi Phil
Nice to hear that you have upgraded in FC v5, it is a great tool and - by far - more flexible than FC v4. I think that the issues of your VFD is a result of the use of cables. Both VFD and LCD displays are affected from the stray capacitance of multistrand cables. You can solve it by using single wire cables. But the best solution is the direct mounting of display on the same board with MCU, please take a look on the pictures of my PCBs. Display is directly soldered on the back side of MCU.
No, i haven't tried the preamp yet. Reason is that i allways prefer to firstly construct the metal case (at least the bottom plate and the front - rear panels) so as PCBs can be securely mounted in their definite place. Yes, yes, i know that i am a DIY... freak :lol: and i like to make everything at home. But the weather conditions are very bad, we live here in North Greece in the region of -6 to +3 degC the last two months (and snow). The warehouse, were i make works like PCB and metal sheet process , is outside from home. Brrrr... :shock:
When i will have ready the metal plates, with In / Out phono sockets screwed and soldered, i will make some workbench tests with DSO and FFT analyser. I have to establish the values of silver mica capacitors and resistors connected at the feedback loop of LME49710s to not overshoot and to have the best bandwidth. After this i usually make audition tests. Of course, i will inform you.
Cheers
Fotis
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Re: Hi-Fi audio preamplifier using Burr-Brown PGA2310

Post by philip davies »

Hi Fotis

Yes it is a much better version of FC and to be honest I find it easier to use. I only have the home/student license for now but I will be upgrading to the professional license soon. As far as the display is concerned I think I'll be doing the same as you by mounting the display on the back side of the MCU, it will definitely make assembling the finished project much easier. That's fair enough that you haven't tried the preamp yet with audio, I'm no where close to doing that yet with my preamp. I think the weather is just as cold or even colder here in West Wales as it is with you, its -9 degC outside as i'm writing this.

I hope you don't mind but I have made some changes to the fcf file that you uploaded on here. After noticing that PORT D had three spare pins I've added two extra menu's, after the "BALANCE" menu I have added an "EQ" menu which allows you to bypass an external Graphic EQ by rotating the encoder. I might be using a Graphic with my finished power amp and preamp project so I thought this might be a useful function if it's not needed. The last menu that can be selected before returning back to volume is a "REC OUT" menu which allows to choose between a Minidisc recorder or a CD recorder and you can also select off which switches the record outputs off. Because I only have the home/student licence of FC v5, I can only experiment on actual hardware by removing the "Serial Data Out" Macro for the PGA chip and also removing the "RC5" Macro because it has some kind of limit, but before I started any modifications I did save the original fcf file. For now though the two extra menus are working but after changing the settings on either "EQ" or "REC OUT" it makes the "INPUT SELECT" jump when i try to change from CD to DVD, it might jump from CD to TAPE and then go from there. I haven't worked out why it's doing this yet but I'm going to keep on trying. I could post my modifications on here if you would like to have a look.

Best Regards

Phil

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Re: Hi-Fi audio preamplifier using Burr-Brown PGA2310

Post by fotios »

philip davies wrote:I could post my modifications on here if you would like to have a look.
Phil
Hi Phil
Yes, i would like to take a look on your project. Please feel free to upload schematics and fcf file (the FC4 version), this thread is open to everyone, i like to exchange ideas with other people.
Wow, -9 degC! BTW i have another one friend from Wales, i know him 5 years ago from the diyAudio forum, i just know his first name "Andy". He is a great guy like you.
Cheers
Fotis
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Re: Hi-Fi audio preamplifier using Burr-Brown PGA2310

Post by philip davies »

Hi Fotis,

Thank you for your kind words, it is very much appreciated and I can also say the same for you to :D

What I will do is finish the modifications that I'm doing now and then incorporate them into the original fcf that you uploaded which has the RC5 function. I will also try and use the RC5 function to control the two extra menu's that I've added. Once this has been done I will post it on here for you to take a look at.

Best Regards

Phil

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Re: Hi-Fi audio preamplifier using Burr-Brown PGA2310

Post by philip davies »

Hi Fotis,

Well here is the modified code of your pre-amp. It now allows the user to select 2 record outputs and also allows an external Graphic EQ to be switched in and out.

The first thing I did was to add two extra macros, one called "EQ" and another called "Record Out". These two macros allows a setting to be changed via rotating the encoder either clockwise or anti-clockwise. Both of these macros have been added to the existing menu button that is built into the panasonic encoder. By pressing the menu button you enter the Input Select, pressing the menu button for the second time allows you to make changes to the Balance, pressing the button for the third time takes you to a new menu that I've added that's called EQ. Once you have entered the EQ menu it automatically switches an EQ into the audio path and shows "EQ ON" on the display and also turns on an LED labeled "EQ", rotating the encoder clockwise or anti-clockwise will switch the EQ out of the audio path or back in and also turns the LED of and on. When the pre-amp is turned on the EQ is automatically switched on as I always use my Graphic Eq to fine tune the sound to my licking but if this is annoying it can be easily removed from the code so that it's not automatically switched on. Pressing the menu button for the fourth time brings you to the last menu that i've added and this is called "REC". Record outputs are automatically turned off when the pre-amp is turned off/standby also they are turned off automatically when you enter the "REC" out which is showed on the display as "REC OFF". Rotating the encoder allows you to cycle between OFF, MD and CD-R. Choosing MD or CD-R turns on an LED to confirm that one of the outputs are on. I have also added a fail safe method of stopping positive feedback in the record out, for example if the MD has been selected as the input source and you also set the REC out as the MD, normally this will result in a positive feedback once the record button is pressed and a loud squealing noise will be present in the audio speakers (I've done this many times with an old integrated amp I once owned). The fail safe switches off the MD input if the pre-amp has been set to send an audio signal to it for recording, also if the Record Out has been set to MD and then the MD has been selected as input source then the Record Out is automatically switched off from the MD. This also works exactly the same for the CD Recorder to prevent such problems. Pressing the menu button for the final time takes you back to the Volume control.

I have added the two extra macros to the RC5_STA macro but as I only have the home version of FC I can't compile a large fcf file like this one because there is a limit so I cannot confirm yet if the two extra sub menu's work via remote control.

Sorry for the long explanations of the modifications that i've done. If you can Fotis try it out on your hardware to see if it works on yours. For now the next step for me is to upgrade to FC v5 Professional so that i can see all this working on actual hardware.

Thanks again for your help

Phil
Attachments
PGA - 2310 Preamp Panasonic Encoder FC5 _ Modified.fcf
(254.63 KiB) Downloaded 248 times

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Re: Hi-Fi audio preamplifier using Burr-Brown PGA2310

Post by fotios »

Hi Phil
Your approach on a complette and flexible preamplifier, really is very good. Congrats! :) To be sincere, i never had thinked a such way of signal routing regarding EQ insertion and REC funnctionality. Your way is very proffesional! Hmmm... You put me in thoughts to colaborate with you in developing of a complette project. I have seen simillar efforts (but not so deeply sophisticated) on diyAudio forum. We can upload the project - finished - on this forum. First of all, we need a schematic. What is your PCB software?
As for the code, i tried in simulator and works just fine. But compiling on actual hardware failed because your fcf is too long! See the messages i received:

Code: Select all

ROM available:8192 words, used:9013 words (110.0%), free:-821 words (-10.0%)
Too much code to fit in ROM, overfilled by:821 locations.
Unfortunatelly, simulator does not shows warnings about it. But this is no problem, i can shorten the code to fit in P16F887, there is no reason to we change the micro. Meanwhile - a week ago - i did a last upgrade on my code, because i had stack overflow issues on actual hardware. I resolved it and the code is correct now. At the same time, i did a recoding of Macros - i removed some redundant of them - and i shortened the length of the initial code.
Today i am some busy, my mother is seek - common influenza, hope so :( - and we have to make a visit in her doctor.
Stay tuned, and let me know please about schematics and your BOM (relays etc.). For PCBs, if you can't make at home and to not pay "an arm and a leg" in e.g. PCB-Express for 1 or 2 pieces, don't worry about it. I can make one PCB set for you and one for me, you simply have to post me one or two presensetized PCBs. We have time for this.
Fotis
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Re: Hi-Fi audio preamplifier using Burr-Brown PGA2310

Post by philip davies »

Hi Fotis,

I'm sorry to hear that your mother is i'll, I hope she gets better very soon.

Thank you for your kind words and also for your very kind help to make this project possible to build. It's a shame that it's to large to compile onto a chip but if you know how to shorten it then that would be a huge help. I did try keeping the two macros that I've added short but for some reason they didn't work all the time. I noticed on my first attempt the EQ could not be turned off when the DVD was set as the Input source, it would only work if I either chose CD or AUX so in order to get it to work I had to add in the encoder steps like you did with the Input macro.

I don't own any software to design PCB's. This is where my projects get a little old fashioned because what I usually do is design them on paper and then transfer them onto copper boards by hand. The same applies to making circuit diagram's. What software do you use to produce PCB's and circuit diagrams?

Best Regards

Phil

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Re: Hi-Fi audio preamplifier using Burr-Brown PGA2310

Post by fotios »

The project is finished and is working! :D
A summary of its properties:
1) This device is a complete high quality preamplifier managed either locally thru 2 push switches and a rotary encoder, or remotely by the use of a universal remote control handset compatible with the Philips RC5 protocol. It offers 5 Inputs, 1 Main Output and 1 Record (pre-Gain stage routed) Output. The functions included are the 7 basic: a)Power On/Stand By b) Mute c)Volume increment d)Volume decrement e)Balance f)Input selection in forward sequence and g)Input selection in backward sequence. All these functions are also supported by the remote control except the Balance.
2) The analog signal process is obtained thru a PGA2310 programmable volume control IC. Voltage gain can be adjusted from -95 up to +6dB in steps of 1dB (0.5dB step is supported by PGA2310 and will offered as an option later). The volume control IC is buffered from input and output devices (CD players, Power amplifiers etc.) thru four LME49710 operational amplifiers configured as voltage followers (i.e. their Voltage Gain = 1). That is because PGA2310 demands source impedance of less than 600Ω, unless its performance could be degraded. Additionally, the two output buffers protect PGA2310 outputs from - possible - overloading. High quality passive components are used in every stage. All resistors are Vishay Sfernice MRS25, while electrolytic capacitors are Panasonic Audio grade (ECA series). Foil capacitors are polypropylene WIMA MKP, while at the feedback loop of each LME49710 a Silver Mica compensation capacitor (not so much for its precision of +/-1% but for its nice "Sound Coloration") is used.
3) A separate power supply is used for the analog section. The operating voltage level is +/-15Vdc and is obtained thru two LM317 - LM337 adjustable voltage regulators that offer some better PSRR from the ordinary 7815 - 7915 fixed regulators.
4) Input selection and Output Mute functions are obtained with the use of high quality Latching relays. The Stand By function (i.e. enable – disable the analog power supply transformer) is also obtained with the use of a powerful SPNO / 10A Latching relay. Latching type relays combine both power saving and noise immunity on audio signal as their coils are inactive for most time. A momentary voltage pulse of 15ms is enough to change the location of their contacts.
5) The whole device is managed by a PIC16F887 microcontroller. The appropriate program code has been obtained with the use of the powerful Visual Programming Software FlowCode v5 of Matrix Multimedia.
Here some pictures showing its functionality
Attachments
PGA2310_3.jpg
PGA2310_3.jpg (158.69 KiB) Viewed 11625 times
PGA2310_2.jpg
PGA2310_2.jpg (159.22 KiB) Viewed 11625 times
PGA2310_1.jpg
PGA2310_1.jpg (157.95 KiB) Viewed 11625 times
Last edited by fotios on Sun Feb 12, 2012 2:59 pm, edited 1 time in total.
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Re: Hi-Fi audio preamplifier using Burr-Brown PGA2310

Post by fotios »

Here is a general view picture, and another one that shows the substance of this project:
You can see in the scope picture that the rise time is JUST 200nsec! :shock: That means a frequency response of: BW=0.34/Tr = 0.34/200nsec = 1.7MHz! The overshoot is negligible, i can smooth it completelly by changing the 47pF compensation capacitors with 100pF, in the cost of a reduced GBW at 1MHz. Not so bad...
Attachments
PGA2310_5.jpg
PGA2310_5.jpg (98.92 KiB) Viewed 11625 times
PGA2310_4.jpg
PGA2310_4.jpg (173.16 KiB) Viewed 11625 times
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Re: HERE THE HEX FILE and the FCv5 fcf

Post by fotios »

Here is the last (modified) code. When I programmed the P16F887 I always received a warning message from Boost C compiler: Possible software stack overflow. This caused from the two different interrupt sources I used, the Port IOC and the RB0. In port RB.0 is applied the main interrupt caused from the IR receiver and I can’t remove it. So, I decided to repeal the Port-IOC interrupt that caused from switches and encoder. I simply added inside the main Loop a continuous call of a macro in which is always checked if any switch is pressed. That resolved the problem of possible stack overflow.
When I fired for first time the actual project, I had… nothing in the output.
I had two errors, both from bad understanding of PGA2310 functionality. The first was the inverse transmission of Gain data to SDI port of PGA2310. The second was that its pin Chip Select must be turned in LOW state before the start of data transmission and again in HIGH state after the end of transmission. You can see both in the macro “SER_OUT”.
Now the code is correct. I ask your forgiveness because the file is obtained with FC v5, I had the need of using it due to its upgraded simulator and many others. Up tomorrow, I will post the file and in FC v4.
I also attach the code in hex format, so as any friend from diyAudio forum can program the PIC16F887 with any available programmer.

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Fotis
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PGA2310_PAN_5LATv5.fcf
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PGA2310_PAN_5LATv5.hex
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Last edited by fotios on Wed Feb 15, 2012 10:39 am, edited 4 times in total.
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fotios
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Re: SCHEMATICS HERE!

Post by fotios »

Attached are the modified schematics after the corrections of Analog and Digital sections.

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PGA2310 PRE CONTROL 1.pdf
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PGA2310 PRE AMPLIFIER 1.pdf
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Re: Hi-Fi audio preamplifier using Burr-Brown PGA2310

Post by Stanga »

Hi Fotios, great job :D .
But any chance of also posting the code in FlowCode4? Not all of us have Flowcode 5 yet.

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