Pre-Amp - HiFi Newbie

First attempt to get into hifi audio

Design Phase I:  Build speaker towers, treat room, run baseline of room and record audio profile.  Make sure audio matches flatline and decay looks good - Done(ish)

Design Phase II: Replace Yamaha Receiver with good amp.  Add to it a DAC that can allow me to do fine tuning to adjust for room / curve preferences of listening.


I am in phase II...  settled on purchase of new kit ST-120 with cap upgrades and purchased parts for "yellow sheet" upgrade (voltage line in is dedicated circuit with dedicated grounding post but sits between 122-123 volt AC)

The DAC I settled on was
First attempt to get into hifi audio

Design Phase I: Build speaker towers, treat room, run baseline of room and record audio profile. Make sure audio matches flatline and decay looks good - Done(ish)

Design Phase II: Replace Yamaha Receiver with good amp. Add to it a DAC that can allow me to do fine tuning to adjust for room / curve preferences of listening.


I am in phase II... settled on purchase of new kit ST-120 with cap upgrades and purchased parts for "yellow sheet" upgrade (voltage line in is dedicated circuit with dedicated grounding post but sits between 122-123 volt AC)

The DAC I settled on was MiniDSP 2x4 HD kit, a USB DAC+DSP in a low cost package powered by a powerful Sharc 400MHz floating point DSP (I am not allowed to post link.. sorry)
This will allow two inputs from Receiver (Movies), one from USB / OpticaL (HiFi). Output is two RCA for ST-120 and two for Servo Subs.

But.... what I pulled as newbie error is ST-120 expects 0-20v input range. Contacting MiniDSP they told me "The miniDSP 2x4 HD has an unbalanced outputs of 2Vrms max."

Ok.. so I think this means I need to rethink. I may need a pre-amp Or... this thought of miniDSP may be a red hearing. What I liked about it was I could tune it very precisely for the room as well as allow receiver to play through for "movie mode" (laptop / USB fob later maybe for HiFi audio playing)

Thoughts. I have diagram but not sure if of value to try to post. Open to poking and commentary / suggestions.  This will allow two inputs for RCA for ST-120 and two for Servo Subs.

But....   what I pulled as newbie error is ST-120 expects 0-20v input range.  Contacting MiniDSP they told me "The miniDSP 2x4 HD has an unbalanced outputs of 2Vrms max."

Ok.. so I think this means I need to rethink. I may need a pre-amp Or...  this thought of miniDSP may be a red hearing.  What I liked about it was I could tune it very precisely for the room as well as allow receiver to play through for "movie mode" (laptop / USB fob later maybe  for HiFi audio playing)

Thoughts.   I have diagram but not sure if of value to try to post.    Open to poking and commentary / suggestions.

I think the VTA-120 takes 0-2.0 Volts input. Your Mini DSP should be able to drive it quite well without a PreAmp. Install the Stepped Attenuator that Tubes4Hifi sells and leave your MiniDSP on full blast -- control the volume with the Stepper Attenuator. Avoids digital data truncation.

Thanks for response.

"...Stepped Attenuator that Tubes4Hifi sells and leave your MiniDSP on full blast ..."


I think what this translates to is that my diagram of DSP will sit between the Receiver (movie mode for right /left channels), and Optical / USB for direct play via computer. The DSP will be set to full output. And to purchase for the ST-120 "21stepVOL wired" for $75.

I thought about that option, but the "21stepVOL wired" has no remote ability. The amp is not in line of sight of the listening area, so I use a IR repeater (black bean). It also allows me to create "plays" to KISS for wife / kids of "Movie" "Music" to turn on things and set inputs etc. But one other thing I can do with black bean is run a script to turn all volumes down to zero.. then step back up to 10% (in case someone leaves it at high listening levels (aka older son )

If above is what you meant. I have three options:
1) Initially purchase the "21stepVOL wired" for the ST-120 and test and baseline DSP at full volume and using mechanical volume to set level. I think I will also need to get "TDR kit" to delay tube playing before warmed up.

2) Do option 1 but then move the volume control to some kind of IR motorized stepping control board. I wish I could get the parts used in the SP12 (remote stepping volume control etc.. to put into case with the DSP but not seeing any channel to purchase that.

3) Save up money and purchase SP12 (has IR remote and seems like a good kit)... though the 14 / 16 could happen but lack IR and so back to "who is doing volume control" issue again

Thanks

In my set-up, I opted for the ST-70 and purchased the stepped attenuator since at the time it was complete, did not have a preamp. Was strictly running signal from an Ipad. Since then built the system to include a Parasound Halo preamp. Run that direct with the ST-70 volume control set at 95-98%. Options are nice.

Yeah, you understood me exactly. The VTA ST-120 runs on 0 - 2 V. I suggested the stepped attenuator because I don't know how the Mini-DSP cuts volume -- if it does it digitally, you may lose bits of resolution by cutting volume, but the stepped attenuator just cuts the analog voltage with little or no distortion or loss of detail. I have a stepped attenuator on my ST-120, and it works great -- was really useful when the only input source I had was CD Player without a volume control. You could contact Roy and buy the the stepped attenuator he uses with the remote control, and make your own passive pre-amp.

"..You could contact Roy and buy the the stepped attenuator he uses with the remote control, and make your own passive pre-amp...." Exactly.

Can you PM me Roy's contact if you have it? I figure if I build a small box with DSP and IR controllable stepping attenuator, I can also integrate a 12v power trigger also.

Easiest way to contact Roy is at. info@tubes4hifi.com. If it goes to Bob, he can always forward to Roy.