Maybe.
If you do not insert a pot at the input the ACP+ becomes a mini amp (or a headamp) with a gain of 8 (9dB).
Why do you need fixed output at the RCAs?
AFAIK to achieve your goal you'll need to run two separate sets of ACP+, one as a headamp with a pot at the input to vary the volume, and one with no pot with a fixed gain Av = 8.
If you do not insert a pot at the input the ACP+ becomes a mini amp (or a headamp) with a gain of 8 (9dB).
Why do you need fixed output at the RCAs?
AFAIK to achieve your goal you'll need to run two separate sets of ACP+, one as a headamp with a pot at the input to vary the volume, and one with no pot with a fixed gain Av = 8.
What specifically do you want the ACP+ to be doing in the chain when combined with an integrated amp? Are you looking to see what it sounds like when it's in the chain as a gain stage? The "simplest" way to potentially accomplish a "fixed" output would be to use the standard design and set the pot to max, or whatever voltage output makes sense to you when combined with your integrated. The integrated will also have voltage gain. So, there are some potential pitfalls assuming a "hot" input signal could lead to clipping at lower "volume knob" settings on your integrated. Check your integrated's input sensitivity. Not attempting to second-guess your intention, but it is an interesting use case. If we knew what you wanted to accomplish and why, there may be more to add. I think what you want is possible; but practical will be based upon your skills and willingness to fiddle a bit.
My recommendation would be to build it "as-is" and get a functioning, known working-good set up. Use the pot to find the "sweet spot" with your integrated. If you like what you hear using it with your integrated and still do not like using the pot on the ACP+ to move it to the "sweet spot", then you know in the back of your mind that you can alter it to do what you want later.
My recommendation would be to build it "as-is" and get a functioning, known working-good set up. Use the pot to find the "sweet spot" with your integrated. If you like what you hear using it with your integrated and still do not like using the pot on the ACP+ to move it to the "sweet spot", then you know in the back of your mind that you can alter it to do what you want later.
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Thanks. As per my first post I’m primarily looking for a headphone amp with two single ended inputs and a fixed, pass-through line out. I have an amp with no outputs (apart from speaker) and two sources that I would like to use with headphones. I don’t want to use the head amp as pre because the integrated has a better pre stage and I don’t want to have to remember where I left the volume on the head amp when I listen to the integrated.
There are a couple - not many - commercial products that do it but I was looking at other options and the ACP+ has the general bits and pieces I want except the line out is variable, not fixed. My question is can it be made to be fixed easily and it would seem that the answer is no, which is fine, it just means I look elsewhere for solutions.
Plan b would be to build a headphone amp then add a 2 x 2 matrix switch to the chassis to select whether the output goes to the line out jacks or the headphone amp
There are a couple - not many - commercial products that do it but I was looking at other options and the ACP+ has the general bits and pieces I want except the line out is variable, not fixed. My question is can it be made to be fixed easily and it would seem that the answer is no, which is fine, it just means I look elsewhere for solutions.
Plan b would be to build a headphone amp then add a 2 x 2 matrix switch to the chassis to select whether the output goes to the line out jacks or the headphone amp
The ground plane is completely empty, except for the conductive mounting holes to bond the circuit PCB to it via the screws. This makes it quiet and suitable to be run with no chassis. It's pretty neat.
Anything you seen the ground plane in the edge-on photo is actually refections from the circuit PCB. It is mirror smooth.
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Hmmm... This circuit sounds insanely good, I suspect you'd be very pleasantly surprised if you drove the amplifier section with ACP+.
If the "pre" gain stage of the integrated is superior and you just want an HP amp hooked to the same sources, then I'd suggest just building or buying a selector to be used prior to the ACP+ and truly bypass it. A - signal goes to ACP+ for HPs. B - signal goes to Integrated. Unless you want the "color" from the ACP+, why bother to go to the trouble of modifying the ACP+ to feed your integrated?
Either way... to do what you've originally described regardless of why, should not be hard depending on your skills. Just take the pot out of the circuit for the line output using whatever method you'd like and add whatever fixed resistor(s) (or not) you want. Decide if you want to use the HP jack to switch between outputs or some other method. That should get it done. You can use your own PCB design or possibly tweak the existing boards. Others may have suggestions and/or say that what I'm describing is idiotic.
What I've been unsuccessfully trying to say is that you'll still be "doubling up" by using the gain stage of the ACP+ even with a fixed voltage output. That could be a pro or con and have its own pitfalls based on how your integrated is designed and the choices you make.
Either way... to do what you've originally described regardless of why, should not be hard depending on your skills. Just take the pot out of the circuit for the line output using whatever method you'd like and add whatever fixed resistor(s) (or not) you want. Decide if you want to use the HP jack to switch between outputs or some other method. That should get it done. You can use your own PCB design or possibly tweak the existing boards. Others may have suggestions and/or say that what I'm describing is idiotic.
What I've been unsuccessfully trying to say is that you'll still be "doubling up" by using the gain stage of the ACP+ even with a fixed voltage output. That could be a pro or con and have its own pitfalls based on how your integrated is designed and the choices you make.
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Easy-peasy
https://www.mouser.ca/ProductDetail/E-Switch/100DP1T1B1M1QEH?qs=%2BZnE/xbLNR9G99Eu8raqOQ==
https://www.mouser.ca/ProductDetail/E-Switch/100DP1T1B1M1QEH?qs=%2BZnE/xbLNR9G99Eu8raqOQ==
Attachments
What you might do is use ACP+ as a stand alone head amp with no volume control, that is fed from the speaker posts of your integrated via a fixed attenuator circuit.
Like:
Headphone attenuation adapter | DIY-Audio-Heaven
Garage1217 DIY Amplifier Build Parts And Extras
You can build this circuit into the input of the ACP+ based on the impedance of your headphones.
Not saying it's the only way, it is one way it can be done, but I suggest you read more on the topic before attempting to do it.
Regarding ACP+, it's a brilliant design, based on the famous Aleph circuit with a few enhancements.
And everything in that circuit is used, there are no redundant bits.
As for other head amps there are plenty of designs available:
ACP+
Whammy
Noir
Starving Student
Korg Nutube
my favourite - Zen Lite
Like:
Headphone attenuation adapter | DIY-Audio-Heaven
Garage1217 DIY Amplifier Build Parts And Extras
You can build this circuit into the input of the ACP+ based on the impedance of your headphones.
Not saying it's the only way, it is one way it can be done, but I suggest you read more on the topic before attempting to do it.
Regarding ACP+, it's a brilliant design, based on the famous Aleph circuit with a few enhancements.
And everything in that circuit is used, there are no redundant bits.
As for other head amps there are plenty of designs available:
ACP+
Whammy
Noir
Starving Student
Korg Nutube
my favourite - Zen Lite
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Small correction:
the attenuating circuit's values should be based on the input impedance of the headamp.
Also this is a very crude way of feeding signal to a headamp.
Ideally you should take the output of your preamp and feed that into the headamp.
It is quite do-able with lifting of a few PCB tracks and introducing a selector switch in between.
the attenuating circuit's values should be based on the input impedance of the headamp.
Also this is a very crude way of feeding signal to a headamp.
Ideally you should take the output of your preamp and feed that into the headamp.
It is quite do-able with lifting of a few PCB tracks and introducing a selector switch in between.