First of all, thank you for an incredible forum. I have been reading now for some weeks and I really learn a lot.
For some time I have been looking for a preamp to drive a pair of active speakers, and came up with the idea to do it myself. I have some experience with soldering, but this will be my first hifi project.
My initial requirements for the preamp where:
- balanced output to the speakers
- a few (3-5) analogue inputs, one or two balanced and the rest singular
- it should include a RIAA preamp for my turntable
- a jack out for headphones is preferable
- I would like Internet streaming of radio and other services
- since the previous point involves a DAC, including a few s/pdif inputs would be nice
All this should be in one box. Since I am a newbie I am more than happy to receive suggestions for improvements or alternative solutions. After lurking around for a while I came up with the following:
- Pass Balanced Zen Line Stage preamp (BOSOZ)
- Twisted Pear Audio:
* Opus DAC
* S/PDIF 4:1 MUX/Receiver Module
* The OTTO-II 2:1 Digital Switch Module
* Retro RIAA Stage
- Raspberry Pi (RPi) with Volumino using I2S output
So far, so good! The S/PDIF 4:1 and OTTO-II 2:1 combo should allow me to select between S/PDIF and RPi streaming. However, there are still a lot of details to consider.
First is the volume control: There are several options out there. Right now I am leaning towards an Electroswitch Rotary Switch with 23 positions (and one pole per deck, right?). For 140 EUR I get four decks allowing attenuation on the balanced outputs (P3 and P4). Alternatively I buy one with two decks for half the price and adjust the circuit gain (P5).
Second is input selection: I think the analogue input selection could be done by a rotary switch as well. Would I need one deck with four poles and 4-6 positions? Could I do something similar to the 4:1 Receiver and OTTO-II Switch. I would like to switch seamlessly between four s/pdif inputs and the RPi.
Third thing to consider is the power: Pass suggests two 2*30V transformers, but could you use one 2*55V and save some space. But to power all units I need at least: +-30V (BOSOZ), +-(6.5-15)V (Opus DAC), +(5-12)V (S/PDIF), +(4-5.5)V (OTTO-II), +5V (RPi), +-(12-15)V (RIAA). That is a lot of different potentials, but as I see it I need: +-30V, +-12V and +5V. What is the smartest way to do this?
Fourth: I would like to use this as a headphone amp once in a while. Is it possible to get a jack plug on the front with a switch that mutes the monitor output signal with a relay?
Kind regards,
Jakob
For some time I have been looking for a preamp to drive a pair of active speakers, and came up with the idea to do it myself. I have some experience with soldering, but this will be my first hifi project.
My initial requirements for the preamp where:
- balanced output to the speakers
- a few (3-5) analogue inputs, one or two balanced and the rest singular
- it should include a RIAA preamp for my turntable
- a jack out for headphones is preferable
- I would like Internet streaming of radio and other services
- since the previous point involves a DAC, including a few s/pdif inputs would be nice
All this should be in one box. Since I am a newbie I am more than happy to receive suggestions for improvements or alternative solutions. After lurking around for a while I came up with the following:
- Pass Balanced Zen Line Stage preamp (BOSOZ)
- Twisted Pear Audio:
* Opus DAC
* S/PDIF 4:1 MUX/Receiver Module
* The OTTO-II 2:1 Digital Switch Module
* Retro RIAA Stage
- Raspberry Pi (RPi) with Volumino using I2S output
So far, so good! The S/PDIF 4:1 and OTTO-II 2:1 combo should allow me to select between S/PDIF and RPi streaming. However, there are still a lot of details to consider.
First is the volume control: There are several options out there. Right now I am leaning towards an Electroswitch Rotary Switch with 23 positions (and one pole per deck, right?). For 140 EUR I get four decks allowing attenuation on the balanced outputs (P3 and P4). Alternatively I buy one with two decks for half the price and adjust the circuit gain (P5).
Second is input selection: I think the analogue input selection could be done by a rotary switch as well. Would I need one deck with four poles and 4-6 positions? Could I do something similar to the 4:1 Receiver and OTTO-II Switch. I would like to switch seamlessly between four s/pdif inputs and the RPi.
Third thing to consider is the power: Pass suggests two 2*30V transformers, but could you use one 2*55V and save some space. But to power all units I need at least: +-30V (BOSOZ), +-(6.5-15)V (Opus DAC), +(5-12)V (S/PDIF), +(4-5.5)V (OTTO-II), +5V (RPi), +-(12-15)V (RIAA). That is a lot of different potentials, but as I see it I need: +-30V, +-12V and +5V. What is the smartest way to do this?
Fourth: I would like to use this as a headphone amp once in a while. Is it possible to get a jack plug on the front with a switch that mutes the monitor output signal with a relay?
Kind regards,
Jakob
That's pretty involved for a first project. Your parts selection seems generally sound. Missing seems to be analog source selection. Does Twisted Pear still have that? Also, OTTO-II and the S/PDIF 4:1 seem to be redundant. The latter will allow you to select your Raspberry PI output and three other digital sources.
Build it piece by piece and get each one working before going to the next. I'd start with the BOSOZ and volume control. A 4 pole 23 position switch seems reasonable for balanced out volume control. Twisted Pear once had a balanced relay based volume control you might consider. Also look at Dantimax.
As for headphone automatically muting the outputs, look for a jack with a switch that doesn't connect to any of the TRS (maybe S is OK). Use this to control a mute relay, or mute signal to your volume control board.
Power supplies are going to require multiple transformers unless you are willing to throw away a lot of voltage as waste heat. Yes you can use one 2 x 55 transformer for BOSOZ. You can use a single transformer for all of your +/- 12-15V requirements, although it is a good idea to use separate regulators for each component. I'd use another low voltage transformer for the +5V supplies to keep digital noise out of the audio. You probably should shield the digital components from the analog side. You're packing a lot of stuff into one box - layout and attention to potential ground loops will be critical.
Build it piece by piece and get each one working before going to the next. I'd start with the BOSOZ and volume control. A 4 pole 23 position switch seems reasonable for balanced out volume control. Twisted Pear once had a balanced relay based volume control you might consider. Also look at Dantimax.
As for headphone automatically muting the outputs, look for a jack with a switch that doesn't connect to any of the TRS (maybe S is OK). Use this to control a mute relay, or mute signal to your volume control board.
Power supplies are going to require multiple transformers unless you are willing to throw away a lot of voltage as waste heat. Yes you can use one 2 x 55 transformer for BOSOZ. You can use a single transformer for all of your +/- 12-15V requirements, although it is a good idea to use separate regulators for each component. I'd use another low voltage transformer for the +5V supplies to keep digital noise out of the audio. You probably should shield the digital components from the analog side. You're packing a lot of stuff into one box - layout and attention to potential ground loops will be critical.
Onkyo's flagship preamp handles all that -- the PR-SC5509
😕
As a beginner at DIY i would recommend the Balanced Zen Line Stage as a first project.
One of the most well written DIY articles of all time. Great project to get your feet wet,
in preparation for crossing the river to reach your ultimate (PRE) goal.
😕
As a beginner at DIY i would recommend the Balanced Zen Line Stage as a first project.
One of the most well written DIY articles of all time. Great project to get your feet wet,
in preparation for crossing the river to reach your ultimate (PRE) goal.
Thanks for the quick reply, though the Onkyo seems a bit intimidating
I really appreciate all the help I can get.
The webpage states you can choose from four different S/PDIF inputs and get one I2S output. How do you exchange one S/PDIF input with an I2S?
Will digital noise also come from the Opus DAC and S/PDIF 4:1? In that case I could use a +7.5VD and +5VD for the RPi, S/PDIF and digital part of Opus and +-12VA for analogue part of Opus and RIAA. Sjöström Audio - Home has several PSUs that I have been looking at, but getting an overview is not easy.
I really appreciate all the help I can get.
Hey 🙂
There are also the possibility, that you build the diyaudio psu :Super Regulator V2.2 - Power Supplies and Accessories - Circuit Boards
You can buy parts at RS Components | elektronik- og el-komponenter
You can make both 5vdc, 7,5vdc etc... But be aware that the PI, use as 700-800mA, so a "lot" of heatsinking is proberly needed, but then you also got state of the art supply 😎
// Jesper
There are also the possibility, that you build the diyaudio psu :Super Regulator V2.2 - Power Supplies and Accessories - Circuit Boards
You can buy parts at RS Components | elektronik- og el-komponenter
You can make both 5vdc, 7,5vdc etc... But be aware that the PI, use as 700-800mA, so a "lot" of heatsinking is proberly needed, but then you also got state of the art supply 😎
// Jesper
Where would you get good pcb's for the bosoz? I saw that twisted pear had an x-bosoz a few years back. Is it possible to get one of these?
Etch it yourself
could look like this http://www.diyaudio.com/forums/pass...-your-diy-pass-amplifier-260.html#post3844586
😀
on Passdiy i didn`t find the layout anymore
if you need it pm me
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