Hehe, trust me I want the kits 
Just spent a heap on other audio related bits and pieces so I don't want to commit to 8 kits yet but didn't want to miss out on the boards.
There is a very good chance I'll end up getting full kits off you though.
Maybe I could swap you for some CNC machined chassis?
Just spent a heap on other audio related bits and pieces so I don't want to commit to 8 kits yet but didn't want to miss out on the boards.
There is a very good chance I'll end up getting full kits off you though.
Maybe I could swap you for some CNC machined chassis?
They're available in the kit
Honestly guys, unless you already have the mosfets and the LME49830 sitting in a bag on your desk, I can assure you that the kit will be your cheapest option. I know the DK prices listed aren't the cheapest out there, but placing orders from 6 different suppliers to save a few dollars here and there will not be any cheaper. Digikey alone charges $9 for shipping, and that's if you live in NA.
I think a lot of people see the actual price required to build the amp ($78), and they think "Oh, that's a lot... I can do it cheaper than that". But when you add up all the little costs like shipping, picking up parcels, taxes or VAT, etc... you'll end up with the exact same parts, and might have saved $5 for your troubles. Chances are you will have spent more but won't realize it because you did it small bits at a time.
Again, I know a lot of you (like myself) have stashes of parts sitting around, and if you've already got half the kit then it's obviously not worthwhile. If you're starting from scratch though, the kit really is your best choice.
Cheers,
Owen
Owen
if they think they can do it cheaper, just let them.. no need to try to convince them
i think that just for the convenience of not having to find all the parts would be a PLUS
-joe
They're available in the kit
Honestly guys, unless you already have the mosfets and the LME49830 sitting in a bag on your desk, I can assure you that the kit will be your cheapest option. I know the DK prices listed aren't the cheapest out there, but placing orders from 6 different suppliers to save a few dollars here and there will not be any cheaper. Digikey alone charges $9 for shipping, and that's if you live in NA.
I think a lot of people see the actual price required to build the amp ($78), and they think "Oh, that's a lot... I can do it cheaper than that". But when you add up all the little costs like shipping, picking up parcels, taxes or VAT, etc... you'll end up with the exact same parts, and might have saved $5 for your troubles. Chances are you will have spent more but won't realize it because you did it small bits at a time.
Again, I know a lot of you (like myself) have stashes of parts sitting around, and if you've already got half the kit then it's obviously not worthwhile. If you're starting from scratch though, the kit really is your best choice.
Cheers,
Owen
Ok.. You sold me.. this was/is going to be a next year project for me, and was thinking that the Lateral Mosfets would be available at my usual vendors and I could order them when I was ready, but I see that they are not.... So, Please change my order to:
2 PCB and 2 Parts Kits..
Thanks
JD
(Please correct my entry. Thanks!)
2x full kits
I like the Connex SMPS300R (one per channel) because it requires no heat sink. The higher voltage models are an additional cost. If there is enough interest perhaps Connex can do a group buy version for this project?
Connexelectronic
2x full kits
I like the Connex SMPS300R (one per channel) because it requires no heat sink. The higher voltage models are an additional cost. If there is enough interest perhaps Connex can do a group buy version for this project?
Connexelectronic
Hi Guys,
I'll update the list later today.
Q&A:
Mr. Pass:
As one would expect, you are absolutely correct, and this could pose a problem for people looking to use the differential input option with a high impedance source.
The tests I ran were performed with a 50 ohm source, but it's not really safe to assume every preamp will have the same luxury.
To get the 130 ohm value are you assuming a 6-10k source driving the positive terminal with a differential signal? If you ground the positive input the input impedance of the - terminal should be 240 ohms, and the differential impedance should be 480 ohms correct?
On solution would be to increase the value of the 240 ohm resistors up to 1200 ohms and increase the feedback R's to 34K. This would of course impact the noise floor, but would provide closer to a 500 ohm input impedance. I can test this and report back.
While I have you here, I held aside a PCB for the NTD1 project I did a while back with the intention of sending it your way. Would you build it if I sent it?
Cheers,
Owen
I'll update the list later today.
Q&A:
Mr. Pass:
As one would expect, you are absolutely correct, and this could pose a problem for people looking to use the differential input option with a high impedance source.
The tests I ran were performed with a 50 ohm source, but it's not really safe to assume every preamp will have the same luxury.
To get the 130 ohm value are you assuming a 6-10k source driving the positive terminal with a differential signal? If you ground the positive input the input impedance of the - terminal should be 240 ohms, and the differential impedance should be 480 ohms correct?
On solution would be to increase the value of the 240 ohm resistors up to 1200 ohms and increase the feedback R's to 34K. This would of course impact the noise floor, but would provide closer to a 500 ohm input impedance. I can test this and report back.
While I have you here, I held aside a PCB for the NTD1 project I did a while back with the intention of sending it your way. Would you build it if I sent it?
Cheers,
Owen
I have a few questions for everyone looking to build the amp. Can everyone try to reply with the answers?
- What load do you plan to drive?
- What power output do you want?
- Do you plan to run differential or SE input?
- Will you build a higher voltage regulated supply for the front end?
I'm going to take these answers and specifically dial in at least two of the most popular configurations in terms of the compensation network. There are general single-pole values that will work for a large variety of power levels, but I can spend a little more time on at least two configurations to develop a two pole comp network.
Regards,
Owen
- What load do you plan to drive?
- What power output do you want?
- Do you plan to run differential or SE input?
- Will you build a higher voltage regulated supply for the front end?
I'm going to take these answers and specifically dial in at least two of the most popular configurations in terms of the compensation network. There are general single-pole values that will work for a large variety of power levels, but I can spend a little more time on at least two configurations to develop a two pole comp network.
Regards,
Owen
Some more questions:
First how much does those connex supplies cost? Their website seems to be down at the moment.
Will it be a downside using those supplies compared to a toroid and rectifier assuming the front end has a separate supply on linear regulators?
In any case im interested in a GB for supply, i checked my local suppliers and there were no toroids with dual secondaries. I have seen those before but i couldn't find any now for some unknown reason...
Will the mute circuit solve any problems with unbalanced rails when the amp is turned on/off? I don't like the unknown clicks and pops some amps have, relay is one option.
The low impedance in balanced mode doesn't sound good in my ears. Maybe it's a good idea to add a buffer on the input, but that might in turn cause more trouble with supply due to the high voltage and low noise requirement. The cost and complexity is of course also another problem. I'm mainly curious on the available options here.
Is the 3-layer design cheaper than the 4 layer? Because the PCB manufacturers i have found charge the same amount for both 3 and 4 layer boards since the manufacturing process is the same (one layer is just etched away completely). If the price is the same is there a reason for using 3 layers?
I trust your choice but its nice to learn something new.
Finally when is the deadline for the GB? I'm interested in extra PSUs but i would like to check the alternatives first before updating my order (rectifier vs SMPS for example).
@opc
- What load do you plan to drive?
Unknown (need new speakers), but i want an amp that can handle most/all models on average volume without problems. If there is a reasonable GB for power supply im probably in for that.
- What power output do you want?
Unknown, see above.
- Do you plan to run differential or SE input?
I'm aiming for differential but i would like the SE option as well.
- Will you build a higher voltage regulated supply for the front end?
Yes
Thanks for all your time
First how much does those connex supplies cost? Their website seems to be down at the moment.
Will it be a downside using those supplies compared to a toroid and rectifier assuming the front end has a separate supply on linear regulators?
In any case im interested in a GB for supply, i checked my local suppliers and there were no toroids with dual secondaries. I have seen those before but i couldn't find any now for some unknown reason...
Will the mute circuit solve any problems with unbalanced rails when the amp is turned on/off? I don't like the unknown clicks and pops some amps have, relay is one option.
The low impedance in balanced mode doesn't sound good in my ears. Maybe it's a good idea to add a buffer on the input, but that might in turn cause more trouble with supply due to the high voltage and low noise requirement. The cost and complexity is of course also another problem. I'm mainly curious on the available options here.
Is the 3-layer design cheaper than the 4 layer? Because the PCB manufacturers i have found charge the same amount for both 3 and 4 layer boards since the manufacturing process is the same (one layer is just etched away completely). If the price is the same is there a reason for using 3 layers?
I trust your choice but its nice to learn something new.
Finally when is the deadline for the GB? I'm interested in extra PSUs but i would like to check the alternatives first before updating my order (rectifier vs SMPS for example).
@opc
- What load do you plan to drive?
Unknown (need new speakers), but i want an amp that can handle most/all models on average volume without problems. If there is a reasonable GB for power supply im probably in for that.
- What power output do you want?
Unknown, see above.
- Do you plan to run differential or SE input?
I'm aiming for differential but i would like the SE option as well.
- Will you build a higher voltage regulated supply for the front end?
Yes
Thanks for all your time
Mr. Pass,
I'm not sure if that is a question or a warning...
The app note mentions that you can push the value of Rf up to 47k, which would mean the value of Rin could be pushed up to 1k66 while keeping the same gain. They do mention the THD+N will be "slightly" higher due to higher thermal noise from the increased resistance. I'm not sure what constitutes "slightly" but I suppose it's worth a try.
That would push the input impedance up to a usable level for most sources, although it's still on the low side. I'll measure CMRR while I'm at it and see if there's even a benefit to it at all. If the CMRR is poor, then I might just scrap the differential input option all together.
Regards,
Owen
I'm not sure if that is a question or a warning...
The app note mentions that you can push the value of Rf up to 47k, which would mean the value of Rin could be pushed up to 1k66 while keeping the same gain. They do mention the THD+N will be "slightly" higher due to higher thermal noise from the increased resistance. I'm not sure what constitutes "slightly" but I suppose it's worth a try.
That would push the input impedance up to a usable level for most sources, although it's still on the low side. I'll measure CMRR while I'm at it and see if there's even a benefit to it at all. If the CMRR is poor, then I might just scrap the differential input option all together.
Regards,
Owen