Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Ideas for a bluetooth controlled preamp / headphone amp combo (PGA2311)
Ideas for a bluetooth controlled preamp / headphone amp combo (PGA2311)
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 6th August 2019, 10:53 PM   #1
dsteinman is offline dsteinman  Canada
diyAudio Member
 
Join Date: Aug 2019
Default Ideas for a bluetooth controlled preamp / headphone amp combo (PGA2311)

Hi, I have an idea for a miniature preamp in a configuration I haven't quite seen before aside from some headphone amps. I have some experience with the NRF52840 bluetooth chips, they are really good for building remote controlled devices, and I'd like to try using it to control a small desktop preamp that can do double duty as a headset/headphone amp.

The goals of the preamp would be:
  • parts cost under $50
  • low noise, clean sound
  • power supply from a USB 2A 5V wall wart (same as raspberry pi 3)
  • small size (similar to a FiiO portable headphone amp)
  • no source selection (1 source, 1 output)
  • headset jacks instead of RCA's (for size and headset support)
  • pass through microphone line level signal
  • 4-segment clock-style display (or maybe an OLED)
  • ultra-minimalist design, no buttons or switches (100% Bluetooth controlled)
  • use a Bluetooth remote for volume, mute, power, balance

Inspiration:

Basically I want a smaller, more minimalist, all bluetooth version of the Schiit Saga S with maybe better performance.

I wasn't sure if I'd be able to pull this off until I started studying some other diy PGA2311 projects, particularly this one:

This looks fairly easy to build, and can probably be miniaturized, but from what I understand it should have some additional low-noise power supply and filters/buffers.

There are few other PGA2311 projects on this forum that I want to borrow ideas from, like like this one from user @kulamario. He posted an Eagle file I can start with for my analog section:

Parts:
- PGA2311PA (or smd version PGA2311UA/1K)
- LT3045 for the analog +5V
- MAX1044 for the -5V inverter
- NRF52840 feather board for the MCU, 3.3V regulator, and USB 5V jack
- simple 4 digit display like this one

See the attached image for the basic plan.

My main questions that I could use some help answering:

- will this design be suitable for both driving headphones and powered speakers or a power amp, all off a 2A wall wart?

- will this give adequate low-noise sound quality for "most" people?

- any reason to go with RCA jacks's instead of 3.5mm headset jacks?

- any better/newer digital potentiometers I should be looking at? (eg. CS3318)

- are there more efficient / cheaper alternatives to LT3045 that I should look at?

- is daisy chaining a LT3045 to a MAX1044 a good or bad idea?

- is @kulamario's PGA2311 Eagle design a good place to start?

This is my first audio project so I'd appreciate any tips or suggestions before I get in over my head. I haven't really started anything yet other than reading up and buying some of the parts I plan to use.
Attached Images
File Type: png Mini Pre - plan.png (409.8 KB, 130 views)

Last edited by dsteinman; 9th August 2019 at 04:28 AM.
  Reply With Quote
Old 7th August 2019, 04:07 PM   #2
dsteinman is offline dsteinman  Canada
diyAudio Member
 
Join Date: Aug 2019
After a bit of reading, it looks like PGA2311 isn't going to be sufficient for a headphone amplifier.

Do I need an amp for my project using a PGA2311

So if I want to do a headphone out I'd need to add some additional circuitry, and someone there recommended AD8656 as an option. I updated the plan image a bit but will probably only tackle the headphone part after I got the rest working.
Attached Images
File Type: png Mini Pre - plan 2.png (471.1 KB, 114 views)
  Reply With Quote
Old 10th August 2019, 01:10 AM   #3
xrk971 is offline xrk971  United States
Got Foam?
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Metro DC area
Ideas for a bluetooth controlled preamp / headphone amp combo (PGA2311)
Use a $10 Sanwu BT module. Power that with 5v from a cell phone charger. Use 3.5mm output to feed TPA6120A headphone amp module. Now you can drive just about any headphone. It needs a basic $10 10VA 15v toroidal trafo from Antek.

http://www.ti.com/lit/ds/symlink/tpa6120a2.pdf

TPA6120A Headphone Amplifier ALPS Tone Tuning for 32 ohm to 600 ohm Headset 8751762610793 | eBay

It’s tough to beat specs on that without a lot of work.

Sanwu BT:
SANWU Wireless bluetooth Audio Receiver Digital Amplifier Board With Remote Cont | eBay
__________________
XRKaudio https://www.etsy.com/shop/XRKAudio
  Reply With Quote
Old 10th August 2019, 01:29 AM   #4
dsteinman is offline dsteinman  Canada
diyAudio Member
 
Join Date: Aug 2019
Actually I wasn't even going to add Bluetooth "audio" support, but only to use the Bluetooth MCU (NRF52) to remote control all features of the preamp. There won't even be a volume knob on the box itself because I have a bluetooth optical rotary encoder I can connect to the box to perform all the volume and other controls. So unfortunately I can't use any headphone or preamp kit that has a pot built into it. I'll probably have to print my own boards.

I'm still really struggling with figuring out the power supply. I have zero experience with toroidal power supplies and was hoping I could get by with just a 5V usb cell phone charger.

I read in another forum that someone mentioned using this 5V dual rail power supply to power his PGA2311:

https://www.digikey.ca/products/en?keywords=NMA0505SC

It's a bit more expensive than I was hoping but if it'll work then I might not need a toroidal?
  Reply With Quote
Old 10th August 2019, 01:26 PM   #5
xrk971 is offline xrk971  United States
Got Foam?
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Metro DC area
Ideas for a bluetooth controlled preamp / headphone amp combo (PGA2311)
That $12 Sanwu module above is 5v USB and can actually power headphones to a certain extent all by itself. I thought you were looking for a pretty powerful headphone amp which is why I suggested TPA6120 but that needs +/-v supply. You can get +/-v DC-DC converter from 5v. But they will need some post filtering and can sound good.

Look for Murata DC-DC converter (get at least 150mA) and look for 5v input and +/-15v output or +/-12v outout. Add a 22uH and 2.2uF film cap filter on the output.
__________________
XRKaudio https://www.etsy.com/shop/XRKAudio
  Reply With Quote
Old 10th August 2019, 03:43 PM   #6
dsteinman is offline dsteinman  Canada
diyAudio Member
 
Join Date: Aug 2019
The headphone section is looking a bit too complicated for me right now, I think maybe I'll revisit that after I get the PGA2311 section fully working and sounding good.

I updated my plan image with a Murata +5-5V supply connected to a 2.5A usb wall wart.

Would I use the 22uH inductor and 2.2uF film cap filter on each of the +5V and -5V outputs of the Murata, before connecting them to the PGA2311?

I already got the MCU and cathode display all hooked up and working. Those cathode segment displays look much better in person than on the photo.
Attached Images
File Type: png Mini Pre - plan 3.png (466.6 KB, 87 views)
File Type: jpg breadboard - mcu display.jpg (198.4 KB, 86 views)
  Reply With Quote
Old 11th August 2019, 06:43 AM   #7
xrk971 is offline xrk971  United States
Got Foam?
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Metro DC area
Ideas for a bluetooth controlled preamp / headphone amp combo (PGA2311)
Quote:
Would I use the 22uH inductor and 2.2uF film cap filter on each of the +5V and -5V outputs of the Murata, before connecting them to the PGA2311?
Yes - it helps to get the noise and ripple of the DC-DC down to about 10mV per the spec sheet. If the PGA has a good PSRR that should be fine. Don’t forget to lots of bypass caps. 10uF and 100nF X7R next to Vcc and Vee pins.
__________________
XRKaudio https://www.etsy.com/shop/XRKAudio
  Reply With Quote
Old 12th August 2019, 05:26 PM   #8
dsteinman is offline dsteinman  Canada
diyAudio Member
 
Join Date: Aug 2019
@xrk971, I really appreciate the help.

There are over 4000 22uH inductors and over 3700 2.2uF film capacitors on Digikey with a huge variety of values. What a nightmare. Do you happen to know a good manufacturer numbers to choose?

I already have some Nichicon capacitors that I was planning to use for the PGA.
  Reply With Quote
Old 12th August 2019, 10:23 PM   #9
xrk971 is offline xrk971  United States
Got Foam?
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Metro DC area
Ideas for a bluetooth controlled preamp / headphone amp combo (PGA2311)
You will have to figure it out with specs. Look at your required current and resistance at DC, and the then go by mounting options (SMT vs through hole) and size. Wurth or Coilcraft or Vishay or TDK are all good. Then price of course. For cap a Wima 2.2uF MKS 50v radial 10% is a good bet. It’s not that critical to get it exactly right. You probably need at least 100mA for the headphone although I would bet it’s a lot less.
__________________
XRKaudio https://www.etsy.com/shop/XRKAudio
  Reply With Quote
Old 14th August 2019, 02:32 PM   #10
dsteinman is offline dsteinman  Canada
diyAudio Member
 
Join Date: Aug 2019
I'm gonna pick up both of those inductors and just try them out. There are just so many of them to choose from I'll have to do some trial and error and see if I can determine which one results in a lower noise floor.

Bourns 22uH - 78F220J-RC

Bourns 22uH - 9230-52-RC

I see there are some really fancy ones too like this.

Digikey also has those 2.2uH caps you mentioned.

Wima 2.2uH - MKS4F042205G00KSSD

I also have a few different resistors to try out. The PGA spec sheet says to use "Ceramic or metal film" for the 0.1uF, and "tantalum or aluminum electrolytic" for the 10uF but I've heard mixed things about tantalum in audio equipment.

Vishay Ceramic 0.1UF - A104K15X7RF5TAA

Nichicon Aluminum Electrolytic 0.1UF - UFG1H0R1MDM

Nichicon Aluminum Electrolytic 10UF - UFW2A100MED1TD

I've decided to add source selection to my design, so I managed to find some 5V relays that have a 1A current rating. I'm just hoping the 2.5A 5V power supply has enough juice to activate them.

Omron 5V 1A - G6K-2P DC5

Last edited by dsteinman; 14th August 2019 at 03:01 PM.
  Reply With Quote

Reply


Ideas for a bluetooth controlled preamp / headphone amp combo (PGA2311)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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
DHT Headphone Amp/Preamp Combo Gungnir Tubes / Valves 8 18th January 2019 02:55 PM


New To Site? Need Help?

All times are GMT. The time now is 01:53 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki