Advice on finding a preamp builder

[Ben-M]

I've been looking for a preamp for my main system for more than a year, but recently I got some bad news about the leading candidate and it now looks like I'm going to have to go the custom route, unless someone knows of a readily available product that meets my needs. 

 

System outline:

1. 2 DACs, both XLR outputs only.

2. 5 amps, all XLR inputs only.

3. Only listen to stereo, no multichannel.

4. Only ever use 1 DAC + 1 amp at a time. 

5. Overview:

- The 2 DACs are just different flavours and basically "spot 2" is for visiting DACs that I'm trying to get a feel for. But only XLR.

- The 5 amps are 4 for headphones and 1 pair of active monitors. Due to my setting, I can't rock the speakers all the time and never in the day time. But I like to listen to them when I can. The 4 amps are just ideal pairings for 4 different headphones. I've got rack space and since the amps and the headphones aren't too big or unwieldy like speakers are, I can handle owning multiple sets geared towards specific musical styles/my mood.

- I want it all connected, all the time. I will power components on or off as needed, but I don't want to deal with plugging or unplugging anything.

 

**I did find that a pro-audio "mixer" is pretty much what I'm looking for in regards to I/O and I/O isolation/impedance matching. However, they're mostly pretty ugly, don't have a remote, have too many dials, and won't look good on an audio shelf/rack with all my other components.

-> that is, unless someone knows a good one that mostly fits my needs listed below 🙂

 

Preamp requirements:

1. Needs 2x XLR ins + 5x XLR outs.

2. Everything must be able to be connected at all times and not have any performance difference vs. unplugging anything.

3. Due to impedance loads, the outputs will all need to be isolated and buffered to allow all amps to be connected simultaneously, but not create a parallel impedance situation where the input impedance seen by the preamp is too low. 

4. I don't want anything run in parallel, such as input/DAC 1 is "on" and then all outputs are also "on". Only 1 input and 1 output can be active at any time. 

5. Must work via remote. Apple remote is a handy one. 

 

*A great reference is this custom LDR preamp built by Mike at Redstone Electronics. Mike doesn't do contract work anymore and there are some differences, but overall it's a great reference and he did a beautiful job. Look how flush the OLED is mounted... 

 

Nice stuff, but not 'needs':

1. Volume memory for each "input+output" combination from last use. 

2. Use Tortuga Audio LDR preamp boards.

3. Use Tortuga Audio OLED display and Apple remote receiver. 

4. Use a tube buffer for the outputs.

5. Use output transformers after the solid-state/tubes to create a pure balanced XLR signal (akin to Empirical Audio's Final Drive component).

 

Price range:

$2000-4000. 

*we'll try to mitigate the custom casework costs somehow and put the majority of dollars into the component and workmanship.

 

 

 

So, I'm hoping someone can give me some advice on where to post this info to find a builder, or if you are one, to contact me via PM. Or if anyone knows a suitable preamp that's got 2x XLR balanced ins + 5x XLR balanced outs and can deal with all being connected all the time, then post it up. 

[STC]

Try Mick of http://www.supratek.com.au/

 

He makes custom preamps. I used one his preamp and it sounded fabulous and accurate.  It can be bypassed for HT too. 

 

Not sure if he make all you wanted within $4K though. 

[audiobomber]

DIYAudio would be the best place to ask: 

https://www.diyaudio.com/forums/solid-state/

[Ben-M]

5 hours ago, STC said:

Try Mick of http://www.supratek.com.au/

 

He makes custom preamps. I used one his preamp and it sounded fabulous and accurate.  It can be bypassed for HT too. 

 

Not sure if he make all you wanted within $4K though. 

I just took a look, Mick makes some VERY nice looking preamps. Thanks for the advice, I'll contact him and see where it goes. 

[Ben-M]

28 minutes ago, audiobomber said:

DIYAudio would be the best place to ask: 

https://www.diyaudio.com/forums/solid-state/

Thanks. I've been a member there for ages, but don't frequent it much. I'll see if I can get any bites 🙂

[a.dent]

21 hours ago, STC said:

Try Mick of http://www.supratek.com.au/

 

He makes custom preamps. I used one his preamp and it sounded fabulous and accurate.  It can be bypassed for HT too. 

 

Not sure if he make all you wanted within $4K though. 

I'd contact Mick. He's a great bloke to deal with and is extremely passionate.

The $4k might be a stumbling block though.

[Ben-M]

28 minutes ago, a.dent said:

I'd contact Mick. He's a great bloke to deal with and is extremely passionate.

The $4k might be a stumbling block though.

I just heard back and he said this wouldn't be his cup of tea. He said his focus is on single-in, single-out preamps where he's trying to make the most of the circuit, not connect a nest of ancillaries and add convenience. His stuff did look top notch. 

 

So, that one seems to be off the table for now, which is too bad. I've posted over on diyaudio, so we'll see if that goes anywhere. 

 

I'm happy to hear any other opinions here as well, especially on design (without discussing the balanced XLR requirement). I've been looking at Tortuga Audio's LDR preamps for a couple of years now, but I also like the AVCs by Bent Audio. Neither of them offer models like my I/O needs, but the topologies/tech are interesting and DIY friendly. 

[4est]

3 hours ago, Ben-M said:

I just heard back and he said this wouldn't be his cup of tea. He said his focus is on single-in, single-out preamps where he's trying to make the most of the circuit, not connect a nest of ancillaries and add convenience. His stuff did look top notch. 

 

So, that one seems to be off the table for now, which is too bad. I've posted over on diyaudio, so we'll see if that goes anywhere. 

 

I'm happy to hear any other opinions here as well, especially on design (without discussing the balanced XLR requirement). I've been looking at Tortuga Audio's LDR preamps for a couple of years now, but I also like the AVCs by Bent Audio. Neither of them offer models like my I/O needs, but the topologies/tech are interesting and DIY friendly. 

TBH, I have never seen a pre amp with five selectable outputs. Your search would be much easier if you used a separate output selector.

[Ben-M]

5 hours ago, 4est said:

TBH, I have never seen a pre amp with five selectable outputs. Your search would be much easier if you used a separate output selector.

Absolutely. The only things I found like it are pro-audio mixers. They are preamps, but I'm not sure how they're deployed/what their use case is in their setting. 

 

Anyway, yeah, the only things I've found like what I need are not our traditional preamps. That really rots my ass too, as I don't feel my use case is that far out in left field. I don't have a turntable, SACD transport, BluRay transport, and DAC in my setup, where I'd need 4-5 inputs and only 1 output to a set of speakers in the big home that I don't own. I think that's nonsense considering where high-quality digital (DACs), lossless streaming, and Roon are now. I feel times have changed and we've shifted more towards limited inputs and a solid use case for multiple outputs (the rapid rise in popularity of high-end headphones over the past 15 years). 

 

But, it seems I'm the only idiot out there trying to push this need and no one currently meets it... 

 

Now, when you say a "separate output selector", do you mean something like the Pro Co Switch Witch? If so, I did think about that route for a while, but I told myself I've got to push for having a preamp that meets my needs, not lowering my expectations or "just unplug the ones you don't want to use", as another $3000 preamp manufacturer recommended to me...

 

Do you have any other recommendations for "separate output selectors" besides the Switch Witch?

[4est]

I do not have another suggestion, but one needs to do what works for them. Regardless of what you think ought to be available, the market generally bears that out in time. There is no rocket science to this. It merely needs to be made by someone. I wouldn't expect this to be any cheaper hand made.

[Ben-M]

 

9 hours ago, 4est said:

I do not have another suggestion, but one needs to do what works for them. Regardless of what you think ought to be available, the market generally bears that out in time. There is no rocket science to this. It merely needs to be made by someone. I wouldn't expect this to be any cheaper hand made.

 

Thanks for the insight on it. I really hope I can find a builder as I don't have the space at home to go at this myself right now. I'm struggling to even make my headphone cables that I've had all the part for for the past 3 years...

 

One thing I'm struggling with is the topology. 

 

I've always had a thing for some Bent Audio AVC-1 modules or some Tortuga Audio LDR boards, but I need to solve the input isolation and muting and the output isolation and muting, so that I'm not causing a parallel impedance problem and ruining the sonics of the preamp.

 

I've found that I can add buffers to the outputs, but I'm not sure if that's the right approach or if there's another way to disconnect the unused outputs and thus the preamp would only ever see 1 load, the load of the individual output I've selected. 

[4est]

You would be best of buying the Switch Witch and a pre amp unless you are prepared to build it yourself.

[diecaster]

You are way out of the scope of a preamp. They are typically designed with four or five inputs and one or two outputs. That is the opposite of what you require. Preamps usually do not have output selection switches. All outputs are usually active all the the time. Add in your requirements for balanced inputs and outputs and you are really out in left field. The rest of you requirements put you in “not only does it not exist, there is no way anyone could build it for anywhere near you asking price” territory.  You “nice but not needs” list just doubles down on the problem. 

 

You are dreaming......I would guess it would cost at least $15K for just the needs list. That’s assuming you want it to sound great. 

[Currawong]

You could ask Kingwa of Audio-gd if he'll build you a custom HE-9 with all the outputs. I think his remotes would have enough buttons to be able to handle the switching too.

[Panelhead]

  The routing could be a piece of cake. You can use a FPGA to perform the signal routing.

  One stereo balanced LDR and buffer circuit. The FPGA can assign the selected inputs and output. 

  My current interface does this. But is the normal opposite. Eight stereo selectable inputs and two stereo outputs. But could be programmed for five outputs.

  Mine allows four channel in and four channel output for running stereo main speakers and subs. This is main reason it is used. One pot that allows one knob  level control operation. Plus two stereo balanced headphone circuits with separate level control.

  A diy person could cobble this together with 500.00 in parts. Plus labor and programming. I think 2,000.00 should cover.

 Many diy’ers can program a FPGA.

[sandyk]

4 hours ago, Panelhead said:

A diy person could cobble this together with 500.00 in parts. Plus labor and programming. I think 2,000.00 should cover.

 Many diy’ers can program a FPGA.

 

Your costing is absurdly low for all the options on the wish list, without even adding in suitable metalwork.

 The vast majority of DIYers are not able to program a FPGA.

Quote

You are dreaming......I would guess it would cost at least $15K for just the needs list. That’s assuming you want it to sound great. -Diecaster

 

I agree, but doubt that the total would be quite that high, but it would be quite expensive..

[Ben-M]

Hey guys, thanks a lot for all the discussion in here. I was juggling some crazy projects at work and then spending my spare time actually trying to sniff out the trail I caught wind of, so I didn't end up posting in here. Sorry about that, but I'm not MIA, so that's good.

 

It took a lot of digging and asking around, I will have to do some assembling, but I've really lucked out and mostly covered all my needs. 

 

I found some NIB Bent Audio AVC-1 Slagleformer/autoformer modules and the associated internal PCBs for the front panel/volume, rear I/O, and power input. Then I contacted the Bent Audio owner, John Chapman, and we worked out how to reconfigure the I/O logic to work for me, including the front panel buttons and the remote. 

 

I will have to source a chassis and then assemble the parts, but that shouldn't be too hard where I live now and assembly is easier than "no solution". I know some guys who do CAD work, so I'm just focusing on finding the right chassis and brainstorming on the external looks and optimal internal layout.

 

Preamp will have:

1. 2x XLR ins + 6x XLR outs.

2. Everything can remain connected at all times.

3. DAC output impedance is 22-ohms and collective input impedance is >5000-ohms, so damping remains well over the 10:1 ratio in the worst case scenario.  

4. All inputs and outputs are isolated, so only 1 input and 1 output are "in circuit" at any time. 

5. Uses the Bent Audio, 13 button remote.

  - This includes input switching, output switching, volume control, L/R balance control, mute, and power on/off.

 

Nice stuff, but not 'needs':

1. Volume memory for each "input+output" combination: I'm not sure yet, I'll find out soon. 

2. Use Tortuga Audio LDR preamp boards: Didn't happen, but uses my other leading candidate, Bent Audio Slagleformers. I feel I really lucked out here, I've had my eye on these 2 implementations for several years.

3. Use Tortuga Audio OLED display and Apple remote receiver: Uses Bent Audio displays and LEDS, and Bent Audio remote. 

4. Use a tube buffer for the outputs: No buffer right now, but there is room in the chassis for balanced buffers.

5. Use output transformers after the solid-state/tubes to create a pure balanced XLR signal: The Slagleformers achieve this.

[Ben-M]

I will update the thread as I receive the parts and move through with the build. It's going to take some time because I'm going to try to push the quality level, but I hope the final results can be a good reference for anyone else interested in this kind of situation. 

Oh, and prices. 

The Bent Audio parts so far cost $2400 USD and I'll spend maybe another $1000 USD on the chassis. I expect the assembly wire and such to cost maybe another $100 USD as I already have the soldering equipment, silver solder, and nice wire, but there should be some incidentals. 

 

It is a semi-DIY effort, but coming in around $3500 USD and almost hitting all of my "NEEDS" and "NICE TO HAVES" sounds pretty awesome to me. I wasn't trying to avoid the DIY aspect initially, I just don't have the time for anything intense and in this case, I'd call this more assembly than DIY as everything is already done and all I'll be doing is fastening things to the future chassis and soldering some connections. 

 

Anyway, I'll update the thread as time goes. Hopefully it all turns out as nice as I can see it in my head.

[audiobomber]

Congratulations Ben. Did you ever post your project on DIYaudio? It is a much more suitable and knowledgeable forum for this sort of thing. 

[Ben-M]

Thanks. I did post essentially the same thread over there, but I got pretty similar replies about the offer being way too low and no one really recommending much about how to do it. 

 

I'll follow through over there as well, but I'm more of an AS'er forumite faithful than anywhere else, so I posted my news here first. 

 

Thanks for the heads up, though. I agree and expect that as I get into the assembly part I'll be asking more questions over there. I think I maybe didn't get a warm reception because I'm a newb (like <10 posts) and the post itself was pretty green sounding. I think once I've got some materials on hand and I'm trying to do something, that'll count as paying cover and people will be more helpful.