ACP+ Preamp/HPA for Yarra Preamp - Page 3

MShipmanPE · 17th June 2020, 06:29 PM

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?

xrk971 · 17th June 2020, 07:29 PM

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.

pwagner · 17th June 2020, 10:43 PM

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

xrk971 · 18th June 2020, 05:23 AM

Quote:

Originally Posted by MShipmanPE

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?

Haven’t had a chance to measure it yet. Will see what I can do.

xrk971 · 18th June 2020, 06:59 AM

GB status update.

Quote:

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

adn6244 · 20th June 2020, 10:02 AM

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

xrk971 · 20th June 2020, 02:32 PM

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.

adn6244 · 20th June 2020, 07:21 PM

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.

thompsontechs · 20th June 2020, 07:28 PM

My advice.... Build them all! The only way to know for sure.

adn6244 · 20th June 2020, 07:49 PM

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?

17th June 2020, 07:29 PM	#22
xrk971 Got Foam? diyAudio Member Join Date: Oct 2012 Location: Metro DC (Virginia)	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. __________________ XRKaudio https://www.etsy.com/shop/XRKAudio

20th June 2020, 02:32 PM	#27
xrk971 Got Foam? diyAudio Member Join Date: Oct 2012 Location: Metro DC (Virginia)	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. __________________ XRKaudio https://www.etsy.com/shop/XRKAudio

20th June 2020, 07:28 PM	#29
thompsontechs Freedom or Death diyAudio Member Join Date: Sep 2019 Location: Illinois	My advice.... Build them all! The only way to know for sure. __________________ Who's your Daddy? Pappa of course.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Modifying a 12ax7 HiFi valve preamp to be a guitar preamp	hoho	Instruments and Amps	109	20th January 2021 08:21 AM
Viking RP61 tube preamp into Mic preamp?	Magnetmaz	Instruments and Amps	1	7th April 2015 09:47 PM
Running a tube preamp into a solid state preamp?	Pckid212	Solid State	5	6th January 2013 11:12 PM
Tube Preamp Popping on Source Input Change (?) / 6DJ8 Preamp On Chip Amps	Travis Clarke	Tubes / Valves	3	16th October 2008 05:52 AM
twisted pear Preamp/other suggestions for Preamp kit	LukeDuke	Chip Amps	1	1st February 2008 10:57 PM

New To Site?	Need Help?
Register to Participate Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	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

17th June 2020, 06:29 PM	#21
MShipmanPE diyAudio Member Join Date: Feb 2012 Location: Alabama	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?

17th June 2020, 10:43 PM	#23
pwagner diyAudio Member Join Date: Nov 2019 Location: San Francisco Bay Area	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

20th June 2020, 10:02 AM	#26
adn6244 diyAudio Member Join Date: Nov 2008	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

20th June 2020, 07:21 PM	#28
adn6244 diyAudio Member Join Date: Nov 2008	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.

20th June 2020, 07:49 PM	#30
adn6244 diyAudio Member Join Date: Nov 2008	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?