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Preamp Q8 Desktop DAC Preamp Development Log

Fosi Audio Team

Fosi Audio Team

Administrator
Staff member
Hi Fosiphiles,

We’re thrilled to officially kick off this thread with exciting news: Q8, one of our most anticipated upcoming products, is finally in development!

Born out of last year’s anniversary co-creation campaign with our community, Q8 is a product that truly embodies your ideas, feedback, and passion. In this thread, we’ll be sharing the latest updates on its progress — from early design concepts to engineering breakthroughs.

As always, your voice matters. The Fosi product team will be here to listen, discuss, and explore your suggestions. Whether it’s a technical detail or a user experience insight, your feedback will help us refine Q8 into something extraordinary.

Brief Introduction:
The Q8 is a multi-input, multi-output DAC preamplifier equipped with both LPF and HPF functions. Designed for users with multiple audio sources or AVR systems, it serves as a powerful system control hub that brings all your devices together seamlessly. It also helps AVR users build a dedicated 2.1 HiFi system with ease and flexibility.

Here is the rendering sketch of the Q8
1749114725618.png

Basic Specs
Input:USB-C, Optical, Coaxial, Phono RCA, RCA*2, Sub-In, HDMI Arc with CEC, Bluetooth
OutputRCA, XLR, Sub-Out
TriggerIn and Out
FunctionsLPF, HPF, Tone Control with Bypass, EQ
In-Built DACAKM AK4493S
Sampling Rates32bit/768kHz+DSD512(USB), 24bit/192kHz(OPT, COA, HDMI), 24bit/96kHz(BT)
Bluetooth ChipQCC3095
Bluetooth CodecsAAC, SBC, aptX, aptX-HD, aptX-LL, aptX-Adaptive, LDAC，aptX Lossless
Remote Control✅

Product Manager in Charge: @Charles

Let’s continue building it together!
 
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What happened, Team Fosi??? Did you interfere with my dreams?
I think that nowadays, having a device that makes implementing a 2.1 system easier is mandatory. I really wouldn't change ANYTHING. I just hope it has a volume control with a maximum and minimum (I really hate the infinitely rotating ones).
I think the choice of the AKM DAC chip, the inputs and outputs (an additional optical one wouldn't hurt, as Jimbob points out), the internal power supply, the master switch on the back, the triggers are totally right.
And of course, the icing on the cake: the HPF and LPF filters.
P.S. The size and aesthetics are perfect! Is it a rack unit? Looking at the front, I'd just put an on/off button on the front as well.
In any case, it's all good news. I look forward to further developments regarding this development.
Cheers, Team!
 
If I have to improve it I will ask for 5.1 output in order to use SACD / DVD AUDIO discs and DSD.files in multichannel format.
 
The unit looks great and not many changes recommended physically other than the ones suggested above. In terms of the display when used as preamp it should show the volume in large font for easy reading from a distance. Hope it comes with a basic remote for changing volume and input selection.
 
If I have an active subwoofer with its own low-pass filter (LPF), does that mean the one that comes with the Q8 would be useless to me, or am I wrong
 
Dafunk5555 said:
Will there be different options for the display or will it be static info display?
Click to expand...
I don't quite understand what you mean. Besides static volume, input mode, and sampling rate, do you want to display anything else? Is it convenient to explain in detail?
 
Carlos Arana said:
If I have an active subwoofer with its own low-pass filter (LPF), does that mean the one that comes with the Q8 would be useless to me, or am I wrong
Click to expand...
You can also turn off LPF, which means you have an additional RCA input port and can connect an additional audio source device.
 
Hi @Charles — I always wonder about the use of displaying the sample rate. The selected input is much more important information, that should be biggest on the display.

I too slightly prefer a dedicated power button, though it’s not a deal breaker. I think a modest, orange button like on the Fosi x5 would look nice on the left.

To be honest, since having tasted room correction I would not put a (pre)amp in my living room without it.
 
Hi @Charles, gentlemen.

Personally, I still prefer a dedicated button to power the device, plus a energy cut-off switch on the back (please do not deviate from the original design)
Would this increase the price much? I don't think so, and if it's only a few dollars, I think we can agree that a limited-rotation knob dedicated only to volume up/down is much better in any case.
As for the power supply, I don't think it should be a cost-cutting factor. It's important to remember that a preamp is, in my opinion, one of the most sensitive links in the audio chain.
Selfishly, I'd save money on the phono stage. Virtually every vinyl lover I know will end up adding an external phono stage to any amplifier or preamp that already has one. I hope I don't offend anyone, but that's what I've actually noticed.
Anyway, just my opinions, and I hope this product comes out soon.
Cheers!
 
Charles said:
We are also considering using a power socket without a switch, similar to the picture below.View attachment 1834
We are also considering using a linear power supply, but the cost needs to increase. I wonder which type of power supply do you prefer?
Click to expand...
Would be very happy to buy a linear power supply, especially if improves sound results. Would it have a similar design and look?
 
Charles said:
Our current definition of knob operation is as follows:
1. Press and hold for 2 seconds to shut down
2. Click: Power on
3. Clockwise/counterclockwise rotation: increase/decrease volume
4. Click: Enter the secondary menu

Can you accept the above operation? Do we still need a separate switch button?
Click to expand...
I hear @Karlaka’s thoughts and completely understand where he is coming from. In my setup a switch at the back would prove tricky for access so I could accept a switch in the front. Especially if it was made an orange feature. To match ZD3 though I’m thinking power control via volume dial. It works for me - unless it reduces noticeable sound quality
 
I agree with your point of view. The information on this display screen is just a randomly selected display content. In fact, we may place the volume at the most important position. I would like to ask if you have any suggestions about the content displayed on the screen. If possible, please describe the information you want to display and arrange its importance level. Of course, it would be even better if it could be represented by pictures. Anyway, thank you very much for your suggestion.
joostdh said:
Hi @Charles — I always wonder about the use of displaying the sample rate. The selected input is much more important information, that should be biggest on the display.

I too slightly prefer a dedicated power button, though it’s not a deal breaker. I think a modest, orange button like on the Fosi x5 would look nice on the left.

To be honest, since having tasted room correction I would not put a (pre)amp in my living room without it.
Click to expand...
 
Karlaka said:
Hi @Charles, gentlemen.

Personally, I still prefer a dedicated button to power the device, plus a energy cut-off switch on the back (please do not deviate from the original design)
Would this increase the price much? I don't think so, and if it's only a few dollars, I think we can agree that a limited-rotation knob dedicated only to volume up/down is much better in any case.
As for the power supply, I don't think it should be a cost-cutting factor. It's important to remember that a preamp is, in my opinion, one of the most sensitive links in the audio chain.
Selfishly, I'd save money on the phono stage. Virtually every vinyl lover I know will end up adding an external phono stage to any amplifier or preamp that already has one. I hope I don't offend anyone, but that's what I've actually noticed.
Anyway, just my opinions, and I hope this product comes out soon.
Cheers!
Click to expand...
Thank you for your suggestion. We are also considering whether to add a separate power button. We would like to ask why it is necessary to maintain the toggle switch of the power input port at the back since the product's switch status can be controlled at the front? Regarding the understanding of the volume limit switch, does it mean that you want a potentiometer knob? This type of knob is prone to slight pitch deviation at low frequencies. What is your opinion on this?
 
Charles said:
does it mean that you want a potentiometer knob? This type of knob is prone to slight pitch deviation at low frequencies.
Click to expand...
Don't use a potentiometer, use an electronic volume control, to avoid non-linearity at low volumes.
It would be good if there was a balance adjustment option - left/right channel.
 
It will be a good option if the screen can display the volume only when to put it up/down, just for 5 seconds. And then display the input source, Khz/bits...
 
Hi @Charles.
In my case, I find a master switch useful, for example, when there are thunderstorms and a power surge could occur. Implementing this type of switch on the back ensures that the power doesn't reach any sensitive areas of the device.
On the other hand, what I propose for volume control is a potentiometer of the highest possible quality, one that doesn't have infinite rotation. On my vintage equipment, or even on the Fosi V3 stereo or T20 I have, I think this is an excellent implementation. In fact, the level scale could easily be silkscreened on the front panel. The feel of this type of potentiometer is extraordinary, and they allow for very fine adjustments. For example, the volume control on the WiiM Ultra is a terrible disaster and has received many negative reviews from users.
 
I have a ZD3 and two ZA3 in mono paired with Emotiva XB2. ZD3 are connected with XLR cables to the two ZA3. The rca out of the ZD3 is connected to a Polka Signature ES12 sub with a build in LPF. What I would like from the Q8 is to remove the lower frequences of the XB2 speakers. So that each speaker is only playing from 130hz and up.
 
adamvondory said:
I have a ZD3 and two ZA3 in mono paired with Emotiva XB2. ZD3 are connected with XLR cables to the two ZA3. The rca out of the ZD3 is connected to a Polka Signature ES12 sub with a build in LPF. What I would like from the Q8 is to remove the lower frequences of the XB2 speakers. So that each speaker is only playing from 130hz and up.
Click to expand...

This will be possible thanks to the implementation of the high-pass filter, or HPF. It really looks like a more than interesting product.
 
zek2024 said:
Don't use a potentiometer, use an electronic volume control, to avoid non-linearity at low volumes.
It would be good if there was a balance adjustment option - left/right channel.
Click to expand...
Yes, we plan not to use a potentiometer, but we do design a balance adjustment function.
 
adamvondory said:
I have a ZD3 and two ZA3 in mono paired with Emotiva XB2. ZD3 are connected with XLR cables to the two ZA3. The rca out of the ZD3 is connected to a Polka Signature ES12 sub with a build in LPF. What I would like from the Q8 is to remove the lower frequences of the XB2 speakers. So that each speaker is only playing from 130hz and up.
Click to expand...
Yes, it's possible. If you don't need so many interfaces with ZD3, you can also purchase our ZP3 directly. ZP3 has HPF function and two adjustable modes (80 and 120Hz).
 
It is more useful to have a RCA preout and a RCA line out
As a general matter every subwoofer has a plate amplifier and adjustable sub frequency adjustment and it looks like the rca outs have defeat switches which is great but just making it a line out is most useful with or without the LPF option and very few are using passive subwoofers
 
Last edited:
Fosi Audio Team said:
Hi Fosiphiles,

We’re thrilled to officially kick off this thread with exciting news: Q8, one of our most anticipated upcoming products, is finally in development!

Born out of last year’s anniversary co-creation campaign with our community, Q8 is a product that truly embodies your ideas, feedback, and passion. In this thread, we’ll be sharing the latest updates on its progress — from early design concepts to engineering breakthroughs.

As always, your voice matters. The Fosi product team will be here to listen, discuss, and explore your suggestions. Whether it’s a technical detail or a user experience insight, your feedback will help us refine Q8 into something extraordinary.

Brief Introduction:
The Q8 is a multi-input, multi-output DAC preamplifier equipped with both LPF and HPF functions. Designed for users with multiple audio sources or AVR systems, it serves as a powerful system control hub that brings all your devices together seamlessly. It also helps AVR users build a dedicated 2.1 HiFi system with ease and flexibility.

Here is the rendering sketch of the Q8
View attachment 1822

Basic Specs
Input:USB-C, Optical, Coaxial, Phono RCA, RCA*2, Sub-In, HDMI Arc with CEC, Bluetooth
OutputRCA, XLR, Sub-Out
TriggerIn and Out
FunctionsLPF, HPF, Tone Control with Bypass, EQ
In-Built DACAKM AK4493S
Sampling Rates32bit/768kHz+DSD512(USB), 24bit/192kHz(OPT, COA, HDMI), 24bit/96kHz(BT)
Bluetooth ChipQCC3095
Bluetooth CodecsAAC, SBC, aptX, aptX-HD, aptX-LL, aptX-Adaptive, LDAC，aptX Lossless
Remote Control✅

Product Manager in Charge: @Charles

Let’s continue building it together!
Click to expand...
Love this design! Love the High Pass and Low Pass filter. There aren't alot of preamps with bass management and so this will differentiate your product against the competition. I strongly suggest having adjustable gain (i.e. low, medium, high). Also, having the option of changing Op-amps (i.e. Sparkos, Burson) will appeal to those audiophiles who enjoy tinkering.
 
My two cents:
  • The display should show, in order of importance, the currently selected input as legible as possible from the listening position, the current volume as legible as possible from the listening position, the sampling frequency, the type of digital input (PCM, DSD).
  • On/off control by pressing the volume knob is perfectly adequate
  • the proposed design of the chassis is simple and elegant and matches the Fosi style
  • I agree with the request for two optical inputs (in my case, one for TV and one for a chromecast audio streamer)
  • Linear power supply is a nice to have but not necessary (the improvement in sound quality compared to a really good switching power supply is all to be proven)
  • I agree with @Karlaka, audiophiles will always prefer to use an external phono preamplifier, and they certainly wouldn't like RIAA equalisation done in the digital domain. We can do without the phono input to save some money or, instead of the phono input, it is better to have a second balanced input
  • Finally, the presence of a parametric equaliser would make this new unit very complete and competitive
 
Last edited:
derekinla said:
Love this design! Love the High Pass and Low Pass filter. There aren't alot of preamps with bass management and so this will differentiate your product against the competition. I strongly suggest having adjustable gain (i.e. low, medium, high). Also, having the option of changing Op-amps (i.e. Sparkos, Burson) will appeal to those audiophiles who enjoy tinkering.
Click to expand...
We are preparing to adopt the universal standard gain of 6dB. Generally speaking, 6dB should be compatible with most devices now, right? Or is there any special case where different gain levels are very important to you?
 
I think that it would be great to have some vent holes on the side as the ZA3 have but also some vent holes on top of the chassi for those who upgreade there unit with other opamps
 
adamvondory said:
I think that it would be great to have some vent holes on the side as the ZA3 have but also some vent holes on top of the chassi for those who upgreade there unit with other opamps
Click to expand...

I understand that a preamp shouldn't generate so much heat that it requires extra vents. But maybe I'm wrong. Personally, I'd prefer not to have them unless absolutely necessary and the unit is as sealed as possible to prevent dirt from entering.
 
marcoevang said:
My two cents:
  • The display should show, in order of importance, the currently selected input as legible as possible from the listening position, the current volume as legible as possible from the listening position, the sampling frequency, the type of digital input (PCM, DSD).
  • On/off control by pressing the volume knob is perfectly adequate
  • the proposed design of the chassis is simple and elegant and matches the Fosi style
  • I agree with the request for two optical inputs (in my case, one for TV and one for a chromecast audio streamer)
  • Linear power supply is a nice to have but not necessary (the improvement in sound quality compared to a really good switching power supply is all to be proven)
  • I agree with @Karlaka, audiophiles will always prefer to use an external phono preamplifier, and they certainly wouldn't like RIAA equalisation done in the digital domain. We can do without the phono input to save some money or, instead of the phono input, it is better to have a second balanced input
  • Finally, the presence of a parametric equaliser would make this new unit very complete and competitive
Click to expand...
Hi, Marco!
  1. Agree.
  2. Disagree. Dadicated button so far better!
  3. Agree!
  4. Agree.
  5. I really don't know.
  6. Thanks! No phono stage = less costs.
  7. It's likely to be a good addition.
 
Karlaka said:
Hi, Marco!
  1. Agree.
  2. Disagree. Dadicated button so far better!
  3. Agree!
  4. Agree.
  5. I really don't know.
  6. Thanks! No phono stage = less costs.
  7. It's likely to be a good addition.
Click to expand...
Haha we aren’t getting anywhere with a dedicated on/off button vs using the knob. It’ll have to be a surprise when it’s launched!
Everything else spot on
 
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