opc, nice work!
I'll guess you and I are the only two persons in the world which make SMD headphone amps (OK, possibly a few more).
My monster
... and what is the purpose of your post ?
I think to show his very good DIY work !
Frex
I think to promote his busines ... Sjöström Audio ... Hijacking a topic ...
You could set up a wiki page here so everyone interested can sign up. You can copy the template and possibly also read my guide lines.
Group buy guidelines - diyAudio
Group buy template - diyAudio
Let me know if you want any help to set up your page.
Hi Guys,
This is my first day back home with an actual PC, and it looks like I’ve got a lot to catch up on. I’ll do my best to answer everyone’s questions, but let me know if I miss anything.
I’ll be posting a full BOM with everything included in the kit, and everything that won’t be included for those looking to purchase their own parts. Overall, the kit will come in about $20 cheaper than buying all your own parts, plus you save on the multiple shipping costs which would be about another $15.
I will also be posting an updated list of all those who have expressed interest, so if people can check the list and give me feedback on what they want, that would be great. Some people expressed an interest early on, but I haven’t heard from them since I posted pricing.
Below are answers to any questions that have been posted on the last few pages.
dggs (post #35):
As a few people pointed out already, there is a bit if a gray area around driving headphones in a “balanced” manner. This design uses a ground referenced output, but one could easily run it in bridged (mono) configuration by tying the + from one channel and the – from the other channel to ground, and feeding a differential signal to the remaining two inputs. You could then drive a “balanced” headphone between the outputs of each channel in a bridge configuration. For this setup, you would need two amplifiers.
The design as is, however, provides excellent CMRR and a very low impedance ground return to the PSU, so I would question the benefit of running the amplifier in bridged mode. As long as your headphones have a separate ground return for left and right channels (all the way back to the headphone jack) then there will be minimal benefit.
N-Brock (post #42):
All resistors and caps will be included in the kit, and they will be sourced from Digikey. Part numbers to follow with a complete BOM.
As for a volume control, there isn’t really anywhere on here you can put one. You’ll need to provide an external pot, or use the volume control function on your DAC.
Pidesd (post #51):
I will run some SE measurements with the inverting input tied to ground. I’ll post the measurements sometime during the week of Jan 4th.
Gordy (post #52):
As I mentioned above, I’ll run some SE measurements, and I’ll try a measurement with a 2k series resistor on the output of the AP. I’m not sure why you would think that source impedance would matter with a setup like this, but it’s easy enough to do, so I’ll give it a go to put your mind at ease.
With a circuit like the one above, the input impedance can be whatever you want it to be. I chose 10k since I know the source I’m using can easily drive it, and it helps keep noise low when there is no source attached. If you’re using a tube amp output, it might be desirable to use 100k or even 1M. In this setup, source impedance will have absolutely no impact on performance.
As for output load capacitance, I’ve taken measurements with my Denon headphones attached, and there is no difference in performance. I’ll try it with some capacitance just for fun to get an actual measurement, but I don’t expect to see anything different. This is, however, a valid concern and a good question.
Semola (post #53):
Did you not look at the measurements posted on the first page of this thread? Absolutely everything you’re asking for is posted there very clearly. There are full frequency THD+N plots from 5Hz up to 20kHz, and 5 different load conditions. There are 4 different IMD measurements, and you need read up on how each one works. You don’t just measure IMD at 10kHz since there are two tones involved.
I personally don’t see any advantage to using the LME49610, but you’re welcome to try it out and let me know. All you get with that part is wider voltage range (could be beneficial if you really need more than 10VRMS of output) and wider bandwidth. The wider bandwidth doesn’t give you any advantage in the audible band, and you’ll still be voltage limited on the rails thanks to the op-amps. Just the same though, it could be worth a try.
N-Brock (post #60):
That is more or less correct. The pots and regulators are included in the price, so all you will need to source is the following:
-Input and output connectors on the amp
-Molex connectors on the PSU if you chose to use them
-Heatsinks for the PSU regs if you chose to use them
-Input and output PSU aluminum can caps
-Standoffs (#4 hardware) if you want to mount the boards to something
I’m not including the above parts since they’re subject to personal taste, and they’re also too large to fit in a small mail envelope.
Peranders (post #67):
That is a beautiful board, and a very interesting looking design. Can you send me a link to the thread?
I really like the layout and size advantages of using SMD parts. You can keep the signal path shorter, circuits more compact, and you can really optimize PSU bypassing and general layout. I also find the performance of SMD caps and resistors to be significantly better.
I’ll take a look at your wiki pages and decide if I want to go that route. I just finished what I would consider a very successful group buy for the I/V stage I was working on, and I think I’ll take some of what I learned there and use it to improve this GB. The only downside was that the time commitment was much more than I had anticipated, and I ended up about $200 short thanks to the absurdly high Paypal fees, and higher than expected shipping fees.
I have a better idea of those costs now though, and hopefully things won’t run into the red this time around.
qusp (post #74):
You should be the first to get a pair of boards, so your opinions would be very much appreciated. If you can do some listening and comparisons with some of the amps you have there, it would be very much appreciated. The more feedback the better!
Cheers,
Owen
This is my first day back home with an actual PC, and it looks like I’ve got a lot to catch up on. I’ll do my best to answer everyone’s questions, but let me know if I miss anything.
I’ll be posting a full BOM with everything included in the kit, and everything that won’t be included for those looking to purchase their own parts. Overall, the kit will come in about $20 cheaper than buying all your own parts, plus you save on the multiple shipping costs which would be about another $15.
I will also be posting an updated list of all those who have expressed interest, so if people can check the list and give me feedback on what they want, that would be great. Some people expressed an interest early on, but I haven’t heard from them since I posted pricing.
Below are answers to any questions that have been posted on the last few pages.
dggs (post #35):
As a few people pointed out already, there is a bit if a gray area around driving headphones in a “balanced” manner. This design uses a ground referenced output, but one could easily run it in bridged (mono) configuration by tying the + from one channel and the – from the other channel to ground, and feeding a differential signal to the remaining two inputs. You could then drive a “balanced” headphone between the outputs of each channel in a bridge configuration. For this setup, you would need two amplifiers.
The design as is, however, provides excellent CMRR and a very low impedance ground return to the PSU, so I would question the benefit of running the amplifier in bridged mode. As long as your headphones have a separate ground return for left and right channels (all the way back to the headphone jack) then there will be minimal benefit.
N-Brock (post #42):
All resistors and caps will be included in the kit, and they will be sourced from Digikey. Part numbers to follow with a complete BOM.
As for a volume control, there isn’t really anywhere on here you can put one. You’ll need to provide an external pot, or use the volume control function on your DAC.
Pidesd (post #51):
I will run some SE measurements with the inverting input tied to ground. I’ll post the measurements sometime during the week of Jan 4th.
Gordy (post #52):
As I mentioned above, I’ll run some SE measurements, and I’ll try a measurement with a 2k series resistor on the output of the AP. I’m not sure why you would think that source impedance would matter with a setup like this, but it’s easy enough to do, so I’ll give it a go to put your mind at ease.
With a circuit like the one above, the input impedance can be whatever you want it to be. I chose 10k since I know the source I’m using can easily drive it, and it helps keep noise low when there is no source attached. If you’re using a tube amp output, it might be desirable to use 100k or even 1M. In this setup, source impedance will have absolutely no impact on performance.
As for output load capacitance, I’ve taken measurements with my Denon headphones attached, and there is no difference in performance. I’ll try it with some capacitance just for fun to get an actual measurement, but I don’t expect to see anything different. This is, however, a valid concern and a good question.
Semola (post #53):
Did you not look at the measurements posted on the first page of this thread? Absolutely everything you’re asking for is posted there very clearly. There are full frequency THD+N plots from 5Hz up to 20kHz, and 5 different load conditions. There are 4 different IMD measurements, and you need read up on how each one works. You don’t just measure IMD at 10kHz since there are two tones involved.
I personally don’t see any advantage to using the LME49610, but you’re welcome to try it out and let me know. All you get with that part is wider voltage range (could be beneficial if you really need more than 10VRMS of output) and wider bandwidth. The wider bandwidth doesn’t give you any advantage in the audible band, and you’ll still be voltage limited on the rails thanks to the op-amps. Just the same though, it could be worth a try.
N-Brock (post #60):
That is more or less correct. The pots and regulators are included in the price, so all you will need to source is the following:
-Input and output connectors on the amp
-Molex connectors on the PSU if you chose to use them
-Heatsinks for the PSU regs if you chose to use them
-Input and output PSU aluminum can caps
-Standoffs (#4 hardware) if you want to mount the boards to something
I’m not including the above parts since they’re subject to personal taste, and they’re also too large to fit in a small mail envelope.
Peranders (post #67):
That is a beautiful board, and a very interesting looking design. Can you send me a link to the thread?
I really like the layout and size advantages of using SMD parts. You can keep the signal path shorter, circuits more compact, and you can really optimize PSU bypassing and general layout. I also find the performance of SMD caps and resistors to be significantly better.
I’ll take a look at your wiki pages and decide if I want to go that route. I just finished what I would consider a very successful group buy for the I/V stage I was working on, and I think I’ll take some of what I learned there and use it to improve this GB. The only downside was that the time commitment was much more than I had anticipated, and I ended up about $200 short thanks to the absurdly high Paypal fees, and higher than expected shipping fees.
I have a better idea of those costs now though, and hopefully things won’t run into the red this time around.
qusp (post #74):
You should be the first to get a pair of boards, so your opinions would be very much appreciated. If you can do some listening and comparisons with some of the amps you have there, it would be very much appreciated. The more feedback the better!
Cheers,
Owen
Hi Guys,
Please find attached the full BOM, and an updated list of everyone who has shown interest.
Please take the time to confirm what is on the list, and let me know if it is correct. I'm not going to worry about numbers just yet, so please don't hesitate to ask for boards or kits.
If you expressed an interest prior to me releasing the pricing info, then please confirm that you are still interested.
A few people have mentioned that they don't want the power supply, but as of right now, it will be included, like it or not. It's a great little supply, and even if you want to use something fancier (I don't see the point with the PSRR of these amps) then surely you can find a use for a regulated +/- 15V supply in another project. It also represents a minimal cost compared to the rest of the project, so it should be easy to live with.
One thing worth mentioning is that preference will be given to those who want a board and a kit together. The more kits there are, the better the pricing is, and I need a minimum number of people interested in kits to meet the pricing I have listed. If most people want just boards, then the kit won't be worth doing. The list, however, seems to indicate that most people are interested in full kits.
Cheers,
Owen
Please find attached the full BOM, and an updated list of everyone who has shown interest.
Please take the time to confirm what is on the list, and let me know if it is correct. I'm not going to worry about numbers just yet, so please don't hesitate to ask for boards or kits.
If you expressed an interest prior to me releasing the pricing info, then please confirm that you are still interested.
A few people have mentioned that they don't want the power supply, but as of right now, it will be included, like it or not. It's a great little supply, and even if you want to use something fancier (I don't see the point with the PSRR of these amps) then surely you can find a use for a regulated +/- 15V supply in another project. It also represents a minimal cost compared to the rest of the project, so it should be easy to live with.
One thing worth mentioning is that preference will be given to those who want a board and a kit together. The more kits there are, the better the pricing is, and I need a minimum number of people interested in kits to meet the pricing I have listed. If most people want just boards, then the kit won't be worth doing. The list, however, seems to indicate that most people are interested in full kits.
Cheers,
Owen
Attachments
Hi Owen,
You have me down for a pair of boards, which I would like to confirm, and you can also put me down for a kit(meaning I'd like a spare set of boards, since I know I'll be kicking myself if I decide to build another one later and didn't take advantage of the opportunity to get a second set of boards)
Thanks
JohnD
You have me down for a pair of boards, which I would like to confirm, and you can also put me down for a kit(meaning I'd like a spare set of boards, since I know I'll be kicking myself if I decide to build another one later and didn't take advantage of the opportunity to get a second set of boards)
Thanks
JohnD