Amp Camp Pre+Headphone Amp - ACP+

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#1,044
Panel mount headphone plug?

SuppersReady said:
Another completed ACP+.

I posted some internal photos a page or two back. I've used an eBay sourced relay based potentiometer. At just over £50 it was worth taking a chance. It even has remote volume control. The chassis is a Hifi2000 unit. I haven't got the gear for milling recesses in the 10mm front panels, so I settled for the 3mm front instead. Not quite as classy but not too bad.

I know I'm preaching to the choir here but the amount of detail from this device is incredible. I've been using it as a headphone amp mostly but tried it in the office setup earlier today. In both applications I can turn the volume up without any sense of stress or distortion in the sound.

Pilk, it works well with the ACA, not surprisingly, even through the little Q Acoustic speakers I have in my office. I'm looking forward to trying it in the main system when time allows.

My thanks to Nelson Pass, once again, for giving such excellent circuits to the DIY community.

Cinco, I hope the situation is improving for you in Texas and the power is still on at home.
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Are you using panel mount headphone plug? I am thinking using it instead of mounting on the pcb, but not sure how to wire it.
 
#1,047
Ben Mah said:
JamesHH,
IRFP610 was a typo. IRF610PBF is good. PBF stands for lead free and that is what is available as the non-PBF IRF610 are now obsolete.

Choose a 33pF film cap. Here is one:

https://www.mouser.com/ProductDetai...EpiMZZMukHu%2BjC5l7Ya09z%2BPFYd21tjAO0570ANE=

Please note that R4 may need adjustment, depending on the J113 (Q3) that you receive. There are variations in the properties of the J113. You will not know whether the R4 value of 125R will be OK until after testing in-circuit or during testing before installing.

See this post Amp Camp Pre+Headphone Amp - ACP+ and following posts , and also here: Amp Camp Pre+Headphone Amp - ACP+.

R4 may need to be as low as 36R. So if you do not have easy local access to resistors, then you should order an assortment of resistors between 125R and 36R, say in increments of 10R or so. You will need two of each (one per channel).
Click to expand...

Thanks for your help!

I've finished this build and it half works, the left channel tests and works as expected, but the right channel measures ~19V at DC1 and doesn't audio. I've inspected it for misplaced components and don't see anything obvious. I am curious if this could be the R4 issue and how I'd go about determining this and what value of resistor I might use.
 
#1,050
Press Fit Pin Socket for R4

Am very new to the forum, so hello to you all.

Currently preparing my first BOM and I read that R4 needs to be changed until one gets a c10mA current running through it.

Is there a press-fit pin socket that someone could recommend, so that I could easily switch between different resistors?
 
#1,052
#1,054
MacMikel said:
Am very new to the forum, so hello to you all.

Currently preparing my first BOM
Click to expand...

I thought I'd share some of my discoveries sourcing the parts for one of these over the past few weeks.

Several parts are not specified in art_acp.pdf, and I am not aware of any other published BOM's. A power switch, R22 and LED. For a power switch I believe Blocked is what is used in the guide. R22 and LED have been covered, I was able to supply these from misc parts.

My power jack was slightly wrong, PJ-037B is specified but PJ-037A seems to be the part that will work for me Blocked

Also covered, the 33pF capacitor that's usually used is: https://www.mouser.com/ProductDetail/505-FKP233-1000-10/

I used m3 screws throughout instead of 6/32 for standoffs and m3 for heatsinks, but only because that's what I had on hand.

As for my right channel problems, I performed some of the measurements suggested and found 0 volts across R13. It's been a few decades since electronics lab, but I'm going to work on measuring everything on both channels and trying to find a place where things diverge.
 
#1,058
Manniraj - Potentiometer value is really about your sources, not the stage after it... Get a 10K or a 50K, they will work fine.

MacMikel - The difference is the diameter of the center pin, which needs to match your PSU... the A has 2.1mm, the B 2.5mm
 
#1,059
manniraj said:
A quick question on the volume pot, presently using a 20k Alps Blue velvet on the ACP. Want to move to a motorized pot and I am able to get a 10k/50k/100k pots and is that sufficient for ACP or strictly 20k is recommended?

Thanks
Click to expand...

As 6L6 rightly said, it's about your sources. But what does that mean? Well, the volume POT is a variable resistor providing a certain input resistance/impedance. You can literally replace it with a resistor (or in this case, add to the input resistor R1 in series). And rest assured by trying the different values suggested you are very unlikely to blow anything up. 🙂

The input resistance is also useful to keep shorts on the input from potentially causing damage further down the line, but really its pretty typical that 100R is the minimum you will find, although some use higher etc...

While there are some fantastic guides here, don't take peoples' word for it, not because it is bad advice, but because your particular situation might warrant something different folks here don't understand. What I would suggest is that you prove this to yourself by looking at the circuit and then measure and understand the output specs for your sources with respect to the inputs.

--Tom
 
#1,060
MacMikel said:
James, these have the same physical shape except for the barrel plug. Why do you say that PJ-037B would not work for you? I have one on order 🙁
Click to expand...

The Triad WSU240-0500 specified in art_acp.pdf is 2mm inner diameter, not 2.5mmm, that would likely be the WSU240-0500-13. The difference between the PJ-037A and PJ-037B is the same, 2 vs 2.5mm inner size. I had ordered extra pj-037b jacks and tore one apart to measure.
 
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