I’ll ask a dumb question. Any resistor changes for HD650 or if I buy a pair of the ESS 422H.
Got any noise floor / harmonic profile graphs?
Got any noise floor / harmonic profile graphs?
This thing runs a pretty hot bias current at 140mA - it can handle 32ohm headphones like 422’s just fine. Certainly 300ohm like HD650 will be more than enough current.
Like to join the GB for 2 prepopulated boards if you get the minimum # necessary. Otherwise, I take 2 non prepopulated.
pwagner / SMT prepopulated / 2 boards / USA
pwagner / SMT prepopulated / 2 boards / USA
Hi X,
Is this project suitable to be used as preamp for class D amp? If not, could you recommend one from your shop?
Kit
Is this project suitable to be used as preamp for class D amp? If not, could you recommend one from your shop?
Kit
Are you looking for a neutral preamp or one that imparts some SE Class A flavor to the sound? What Class D amp? How much gain do you need?
The Yarra preamp is a great choice because it is a foundation upon which low cost modules like this ACP+, or any number of 7 or 8 other preamp topologies can be selected and used by swapping out the daughterboard.
The ACP+ is a very nice sounding quite neutral preamp with a SE Class A flavor. It is very powerful and can drive low impedance loads like 32ohm headphones.
For general purpose preamp use, I recommend the Melbourne daughterboards.
For simple to build and great resolution and a bit of SE Class A sound, the Hakuin is tops.
The Yarra preamp is a great choice because it is a foundation upon which low cost modules like this ACP+, or any number of 7 or 8 other preamp topologies can be selected and used by swapping out the daughterboard.
The ACP+ is a very nice sounding quite neutral preamp with a SE Class A flavor. It is very powerful and can drive low impedance loads like 32ohm headphones.
For general purpose preamp use, I recommend the Melbourne daughterboards.
For simple to build and great resolution and a bit of SE Class A sound, the Hakuin is tops.
I am looking for preamp for TPA3255 amp that I'm planning to buy or build. At the moment I have a 3116 amp with a bad volume control.
So it's either Yarra + Melbourne or Hakuin/ACP+ depending on the sound signature I'm after.
So it's either Yarra + Melbourne or Hakuin/ACP+ depending on the sound signature I'm after.
If I have the time, that's ideal !
Can I connect 6 ACP+ or Hakuin to single volume pot and use it as multi channel preamp?
Can I connect 6 ACP+ or Hakuin to single volume pot and use it as multi channel preamp?
The Hakuin has 100k input impedance, so 100/6 is 17k. Most DACs can drive 17k just fine. I would not use a pot though in between the source and the 6 way divider - but maybe a 7th one with pot to drive the 6. The ACP is also JFET input and 6 way fan-out is probably fine.
Heat management
I thought I would share some recent experience I've had with the ACP+ circuit.
My application is using this circuit as a gain stage for my MoFo monoblocks. Due to the limited room I have inside the chassis, I'm using a strip board layout that is just a little bit larger than the Yara Preamp IPS. As such, I happen to be using the same size and style heatsinks on the output transistors as those used for the Yara version. I have found that the IRF610 devices run very hot with the standard bias current of 150 mA. With the original circuit parameters, the output devices were rapidly heating up to 70 °C before I shut off the power. This is hot enough that device life is likely to be adversely affected, both for the transistors and possibly also for the adjacent electrolytic capacitors.
The original PCB for the ACP+ had enough room for much larger heatsinks, which look like they should do a good job of managing the temperature. With the reduced board space available on the Yara implementation, as well as my own, the small heatsinks are not quite up to the task. That is, unless other measures are taken to reduce power dissipation or improve thermal performance.
So far I have managed to lower the power dissipation by reducing the quiescent current through the output stage from 150 mA to 133 mA. This gave a noticeable reduction in device temperature. I can now hold my finger on the heatsinks for about one second before having to let go. That translates to about 60 °C using the Nelson Pass temperature estimate. This is still hotter than we would like for reliable lifetime, but an improvement nonetheless. I changed R111 from 1.5k to 3.0k and R115 to 3.2Ω, which is 4.7Ω in parallel with 10Ω. The lower current may affect power delivery for some of the lower impedance headphones, but should be fine for most everything else.
The next thing I plan to do is increase the size of the heatsinks. Since there is only room to go up, I will attach two of the small heatsinks together, one on top of the other, using thermal conductive epoxy. This is a slightly tricky operation, as one needs to avoid clogging the mounting hole. I did spend some time on the Mouser website looking for taller heatsinks with the same small footprint, but came up empty. So epoxy it is. 😉
I thought I would share some recent experience I've had with the ACP+ circuit.
My application is using this circuit as a gain stage for my MoFo monoblocks. Due to the limited room I have inside the chassis, I'm using a strip board layout that is just a little bit larger than the Yara Preamp IPS. As such, I happen to be using the same size and style heatsinks on the output transistors as those used for the Yara version. I have found that the IRF610 devices run very hot with the standard bias current of 150 mA. With the original circuit parameters, the output devices were rapidly heating up to 70 °C before I shut off the power. This is hot enough that device life is likely to be adversely affected, both for the transistors and possibly also for the adjacent electrolytic capacitors.
The original PCB for the ACP+ had enough room for much larger heatsinks, which look like they should do a good job of managing the temperature. With the reduced board space available on the Yara implementation, as well as my own, the small heatsinks are not quite up to the task. That is, unless other measures are taken to reduce power dissipation or improve thermal performance.
So far I have managed to lower the power dissipation by reducing the quiescent current through the output stage from 150 mA to 133 mA. This gave a noticeable reduction in device temperature. I can now hold my finger on the heatsinks for about one second before having to let go. That translates to about 60 °C using the Nelson Pass temperature estimate. This is still hotter than we would like for reliable lifetime, but an improvement nonetheless. I changed R111 from 1.5k to 3.0k and R115 to 3.2Ω, which is 4.7Ω in parallel with 10Ω. The lower current may affect power delivery for some of the lower impedance headphones, but should be fine for most everything else.
The next thing I plan to do is increase the size of the heatsinks. Since there is only room to go up, I will attach two of the small heatsinks together, one on top of the other, using thermal conductive epoxy. This is a slightly tricky operation, as one needs to avoid clogging the mounting hole. I did spend some time on the Mouser website looking for taller heatsinks with the same small footprint, but came up empty. So epoxy it is. 😉
I'm back in the game X!
MShipmanPE / SMT Prepopulated / 2 boards/ USA
Carl_Huff / bare PCB / 2 boards / USA
mnichols30030 / bare PCB / 2 boards/ USA
Thompsontechs / bare PCB / 2 boards / USA God Bless it in these trying times!
Aljordan / SMT Prepopulated / 2 boards / USA
Pwagner / SMT Prepopulated (if enough interest) / 2 boards / USA
jwjarch / bare PCB / 2 boards / USA
MShipmanPE / SMT Prepopulated / 2 boards/ USA
Carl_Huff / bare PCB / 2 boards / USA
mnichols30030 / bare PCB / 2 boards/ USA
Thompsontechs / bare PCB / 2 boards / USA God Bless it in these trying times!
Aljordan / SMT Prepopulated / 2 boards / USA
Pwagner / SMT Prepopulated (if enough interest) / 2 boards / USA
jwjarch / bare PCB / 2 boards / USA
Jwjarch,
Great to hear you made the move from CA to CO and are settled in. It’s hammer time!
Cheers,
X
Great to hear you made the move from CA to CO and are settled in. It’s hammer time!
Cheers,
X
GB Interest List update? Is anyone else interested in the pre-populated SMT version? I have the bare PCBs v002 (corrected layout) in for now.
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MShipmanPE / SMT Prepopulated / 2 boards/ USA
Carl_Huff / bare PCB / 2 boards / USA
mnichols30030 / bare PCB / 2 boards/ USA
Thompsontechs / bare PCB / 2 boards / USA God Bless it in these trying times!
Aljordan / SMT Prepopulated / 2 boards / USA
Pwagner / SMT Prepopulated (if enough interest) / 2 boards / USA
jwjarch / bare PCB / 2 boards / USA
meanie / SMT Prepopulated / 2 boards / SGP
Carl_Huff / bare PCB / 2 boards / USA
mnichols30030 / bare PCB / 2 boards/ USA
Thompsontechs / bare PCB / 2 boards / USA God Bless it in these trying times!
Aljordan / SMT Prepopulated / 2 boards / USA
Pwagner / SMT Prepopulated (if enough interest) / 2 boards / USA
jwjarch / bare PCB / 2 boards / USA
meanie / SMT Prepopulated / 2 boards / SGP
MShipmanPE / SMT Prepopulated / 2 boards/ USA
Carl_Huff / bare PCB / 2 boards / USA
mnichols30030 / bare PCB / 2 boards/ USA
Thompsontechs / bare PCB / 2 boards / USA God Bless it in these trying times!
Aljordan / SMT Prepopulated / 2 boards / USA
Pwagner / SMT Prepopulated (if enough interest) / 2 boards / USA
jwjarch / bare PCB / 2 boards / USA
meanie / SMT Prepopulated / 2 boards / SGP
diy40 / SMT Prepopulated / 2 boards / USA
Carl_Huff / bare PCB / 2 boards / USA
mnichols30030 / bare PCB / 2 boards/ USA
Thompsontechs / bare PCB / 2 boards / USA God Bless it in these trying times!
Aljordan / SMT Prepopulated / 2 boards / USA
Pwagner / SMT Prepopulated (if enough interest) / 2 boards / USA
jwjarch / bare PCB / 2 boards / USA
meanie / SMT Prepopulated / 2 boards / SGP
diy40 / SMT Prepopulated / 2 boards / USA
Great to see so much interest in the pre-populated SMT version. If it is high enough, I may have to see what a board house will charge to do this as more than a dozen boards is getting very labor intensive.