Given how much you like the signature of the AJ connected directly, I'd start with the ACP+. I'd make the small adjustment mentioned for a better impedance match for your 650s. I've used it with various Senn phones (800, 800S, 820, 6XX, and 650), and I like it quite a bit. It helps 'tame' the 800, which I don't care for with many amps. However, this is coming from a person that adores a version of the Babel J2, so... grain of salt... re: sonic preferences and a 'softer' presentation. Don't get me wrong, I adore the WHAMMY too, but... in your case, I'd lean ACP+ to start. You know you'll build both anyway. 
Yes, I saw the posts that explain how to match the ACP+ output impedance to HD650s.
By the way, I also like that Babelfish J2 with its (extensive) current mirroring, capable JFET drive capability... but most of all, its great PCB design. One day when work/family obligations permit...
And... yes, I was going to place an order for both headphone amps... but ACP+ is currently out of stock. I am trying to save on shipping costs (Australia).
I really like ACP+ because there's no cabling required, and I'm a minimalist-approach guy... and I do not like the sound of wire, especially shielded...
The WHAMMY? I like that I can use the regs for MOSFETs only, and "cut in" with my shunt regs for the OP AMP. Then, with something like AD8066 (1pF input bias current and absolutely great sound), I'd get rid of all 4 sound coupling caps. That would be nice.
By the way, I also like that Babelfish J2 with its (extensive) current mirroring, capable JFET drive capability... but most of all, its great PCB design. One day when work/family obligations permit...
And... yes, I was going to place an order for both headphone amps...
but ACP+ is currently out of stock. I am trying to save on shipping costs (Australia).I really like ACP+ because there's no cabling required, and I'm a minimalist-approach guy... and I do not like the sound of wire, especially shielded...
The WHAMMY? I like that I can use the regs for MOSFETs only, and "cut in" with my shunt regs for the OP AMP. Then, with something like AD8066 (1pF input bias current and absolutely great sound), I'd get rid of all 4 sound coupling caps. That would be nice
.
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I finally competed my ACP+ yesterday. I must be lucky because the first two J113 I pulled from the roll worked perfectly with the stock 125ohm resistor in R4. I’m getting 11.2V at DR1 on both sides. Result.
Thank-you Nelson and DIYA, I’m very pleased with this little amp (my first build of an active design).
Thank-you Nelson and DIYA, I’m very pleased with this little amp (my first build of an active design).
After changing the resistors for a better match for the higher impedances, ie HD650 250/300 ohms etc I went back to the original setup for 32 ohms and I honestly cant tell any difference.
What would be the issue with staying at 32 ohms and using a 300 ohm headphone have on the sound?
Would there not be less power at the 300 ohm as well?
What would be the issue with staying at 32 ohms and using a 300 ohm headphone have on the sound?
Would there not be less power at the 300 ohm as well?
My acp+ was used with the amp camp mini driving a set of 98db sensitive horns for a while. It's far better than it has any right to be.
Just switched the speakers to John Busch's Ultras which have an easy impedance load but are fairly low sensitivity ... somewhere in the mid to low 80's. Using a tpa3255 class d amp on that speaker. The acp+ sounds good in that mix, too.
Like it with headphones, too.
Just switched the speakers to John Busch's Ultras which have an easy impedance load but are fairly low sensitivity ... somewhere in the mid to low 80's. Using a tpa3255 class d amp on that speaker. The acp+ sounds good in that mix, too.
Like it with headphones, too.
Thank you ZM!
I tightened down the mosfet screws. I'd used pads, not thermal paste. Q6 was the least tight.
I changed my measurement technique by putting the probe right on the mosfet body. The ambient room temperature has also increased since this morning.
This time, I am getting left Q5 = 56 C, left Q6=57 C. Right Q5= 57 C, right Q6 = 55 C.
Given that I do not have anything but a full-sized automotive torque wrench, I am going to assume that some of the variation is due to differences in connection between the sink and mosfet.
Is this a fair assumption?
In any case, could you clarify what you mean by output node voltage? What points would I measure?
Your help is greatly appreciated!
I tightened down the mosfet screws. I'd used pads, not thermal paste. Q6 was the least tight.
I changed my measurement technique by putting the probe right on the mosfet body. The ambient room temperature has also increased since this morning.
This time, I am getting left Q5 = 56 C, left Q6=57 C. Right Q5= 57 C, right Q6 = 55 C.
Given that I do not have anything but a full-sized automotive torque wrench, I am going to assume that some of the variation is due to differences in connection between the sink and mosfet.
Is this a fair assumption?
In any case, could you clarify what you mean by output node voltage? What points would I measure?
Your help is greatly appreciated!
output node voltage - see schematic - output is between Source of upper and Drain of lower mosfet, then DC which you have here ( approx 50% of PSU voltage) is blocked with output cap, so there is no Killing of speaker
few C degrees up or down is nothing
you got it right so just chill
aha, sole trimpot you have in ACA is for proper setting of output node voltage level
but you already know that, having article and build manual fully read
few C degrees up or down is nothing
you got it right so just chill
aha, sole trimpot you have in ACA is for proper setting of output node voltage level
but you already know that, having article and build manual fully read
That is the clone from withmatt:
https://www.diyaudio.com/forums/pass-labs/344836-amp-camp-pre-headphone-amp-acp-post6217165.html
According to
https://m.blog.naver.com/PostView.naver?isHttpsRedirect=true&blogId=lehong1&logNo=221910475587
that one should fit:
https://www.neutrik.com/en/product/nrj6hf-au
https://www.diyaudio.com/forums/pass-labs/344836-amp-camp-pre-headphone-amp-acp-post6217165.html
According to
https://m.blog.naver.com/PostView.naver?isHttpsRedirect=true&blogId=lehong1&logNo=221910475587
that one should fit:
https://www.neutrik.com/en/product/nrj6hf-au
Hi fellow ACP+-ers!
I wanted to let anyone interested in getting the ACP+ kit that I've sent a new batch to the store, and they should be programmed and available in about a week. Note that as of this run of kits, we are packaging them with all of the LS JFETs and the Papa Pass-specified Triad PSUs only. The only option now is the PCB set, and maybe a separate case.
Enjoy!
I wanted to let anyone interested in getting the ACP+ kit that I've sent a new batch to the store, and they should be programmed and available in about a week. Note that as of this run of kits, we are packaging them with all of the LS JFETs and the Papa Pass-specified Triad PSUs only. The only option now is the PCB set, and maybe a separate case.
Enjoy!
