Hi all,

I am currently on the hunt for a good DAC/preamp, and of the commercial offerings, nothing really stacks up for reasonable money ( true analog volume control, true analog inputs, and a _good_ DAC section, preferably in one box.

Cyrus make the DAC XP+, but this is getting a bit older in the tooth now, and while the analog side of it appears to be considered at reference level, the DAC is showing its age now. Bel canto make some nice DAC's but the analog side is either non existent, or it goes through A/D conversion. Not what I want to be seeing.

So this has lead me to this Twisted Pear Audio website.

Is it feasible, and practical, to build a preamp using a Buffalo 2 DAC, Darwin input selector ( 2 of, one for the analog side, and one to switch between various SPDIF inputs ) IVY linestage driver, and maybe an OTTO 2:1 ( for HT bypass duties ) with appropriate power supplies and using a custom controller which will allow me full remote control of the unit? Would probably throw a couple of Toslink adapters in there, and maybe a USB one ( although might wait till a 24/192 offering is available for that? )

I have a mostly DIY system - the only non DIY part is the source ( Squeezebox Touch, Pioneer DVD 969AVI, satellite decoder box, HTPC ) and power amps.

The speakers are made up of Focal drivers - 2x 33WX bass drivers in reflex enclosure, 2x Focal 5K4311(?) mids in transmission line enclosures, and a AudioM tweeter, all in a line source array. My amplifiers are either NZ made Perreaux 350P's ( factory customized, these run the bass drivers, putting about 700w into each driver ) and the mids and tweeters are powered by DIY 250W monoblocks, one for tweeter and one for the pair of mids. Crossover duties are by DIY mono pair of Linkwitz Riley, outboard PSU, at 200Hz and 2Khz ( 24dB )

I currently have a NZ made HFA valve preamp ( stunning, but no remote control, which in my situation is not very suitable ) and a Xindak DAC 8 D/A unit. This is okish.

All up, its a pretty stunning system.

Anyway, between myself and an Electrician/tech friend, I was wondering just how well a "preamp/DAC" made of these components would perform? And what suggestions would people make to maximize its performance? Is it going to be comparable to the likes of say, the Cyrus DAC XP+ ( for those of you who know of it! ) or maybe a Bel Canto DAC 3.5?

I did search the forum for "building a preamp" but it didn't show me any results which were relevant, but if someone else has asked this before, please point me to the thread :)

Many thanks in advance!

Thanks for the reply.

The work side of it is not the issue - I am probably the fussy, perfectionist type when it comes to audio, however I am not really up to speed on design/build work to this level, but my friend who is the tech is the one who is very knowledgeable and capable - so it would be a joint effort. He has a controller ( Auduino) which he has used to control all sorts of gear before. Its capable of doing what we need comfortably. So unless the I2C controllers are more cost effective, or there is a genuine reason to prefer that over a self programed option, we would probably go with that.

Now my questions!

Are there links to the MRB1 module's?

Is it more complicated to switch SPDIF based digital inputs that using some relays as in the Darwin?

Why would you suggest that I would want to do digital domain volume control? Is it better to use the Buffalo to control the digital source volume and the Joshua Tree to control the analog volume?

Our initial concept was ( I hope the formatting stays intact - edit. It didnt, lets try it differently. )

Coax and Toslink inputs, selected via a darwin type ( probably 4 input ) selector.
Feeding into a buffalo DAC.
The output from the DAC goes to another darwin type input selector, this one also "collecting" the analog inputs ( probably another 4 source setup, the digital, 3 analog inputs ). This then feeds an Ivy3.
The Ivy feeds out to an Otto2:1, the purpose of the Otto is to achieve the HT bypass abilities ( although maybe the controller could do this using an analog input set to a fixed gain? )


Or do you suggest a different concept, and if so, why would you suggest differently? Is it to reduce the amount of relays? ( I am not 100% on that concept - indeed, I suspect the Auduino might be able to utilize an analog input for HT bypass, with fixed gain, via a trigger, which still goes through the IVY3 and negates the need for the Otto. More simple, and cheaper to boot :)

Now my last question.

This will probably cost me in excess of $2K NZ, about $1K for the Twisted pear gear, about $1K for a case, connectors, hookup wire, etc. Is this going to perform to the level of the Bel Canto DAC's, Wyred4Sound DACs, Cyrus, etc?
Or am I better to spend $4K-$6Kish on a factory made variant?

Edited by user Tuesday, December 7, 2010 6:21:05 PM(UTC)  | Reason: Not specified

Of course they are more cost effective, at the very least for the DAC board. It's just a port you need at the Arduino board. The digital control of the DAC chip is VERY effective, and offers things like smooth increase and decrease of volume, almost perfect channel balance, etc. If you use an Arduino board the cost consists of just the wiring to the DAC board, so not using it is kind of silly.
Running a second I2C controlled attenuator for the analog part will give you a simple user interface for controlling the level of both the analog and digital inputs, while you could also achieve things like similar sound levels on all inputs (it just takes programming different profiles for each input). Just make sure the addresses on the I2C bus are unique so you can program the 2 independently.

MRB1 is not ready yet, so no links that I know of. Also no price.

The Mux unit can be controlled using an Arduino board. It also has a separate receiver, so you could use that one for the SPDIF reception and move it to the DAC using I2S. This combined with a set of relays allows you to switch between different I2S sources on the DAC board. You'll propably want to use I2S as the interface for the new USB receiver, as it will be limited to 24/192 when using the SPDIF interface.

Question is: do you really need an I/V stage in the analog section? In most cases an analog pre can be limited to input selection and attenuation. The answer will determine how you hook things up.

About the performance level: this is a hard one to answer. My system is different, it's now all DIY (DAC, Amp, wires, speakers) so it's basicly uncomparable to anything else. The performance of my system is extremely high. But I'm using a more expensive dual mono setup. I think it'll compare quite nicely against just about anything. Could one improve it? Propably. What would that cost? A lot more, and esp. when factory built. I've listened to systems costing at least 12 times the price I paid, and I'm still satisfied. IMO The markup in high end audio is a lot more than a factor of 2.

The IVY is really an I/V stage, and in this case you would want it (or a Legato) directly coupled to the Buffalo. If you chose to use an active line stage for the preamp section, I would feed that from the IVY outputs.

No, I'm telling you it's not in it's place in the analog section. It's an I/V stage, and should be coupled to the DAC board like Brian suggests. The output of the IVY can be coupled to the power amp directly, provided you use digital volume control in the DAC board. Otherwise it'll get loud.

That is correct. Most current CE sources already have a signal level that doesn't need a line stage, it just needs to be attenuated. I can't tell you if this is the case for you, you'll have to test it. The output level can be matched up to a certain level as you have the ability to change the attenuation for each input. When you want a signal switch, the arduino board should disable the output, set the attenuation level using I2C, select the right input selection and then enable the output. For simplicity you could simply use the Joshua tree to attenuate all inputs, but I'd try the digital attenuation on the DAC board too. After all it's just a couple of relays you need to add if you want to separate things.


Yes, I mean dual mono DACs: 2 DAC boards, 2 I/V stages, 2 Placid BPs, in my case 2 Placids, 2 Trident kits, 1 Mux.
The Mux is here: http://www.twistedpearau...m/digital/cs8416mux.aspx

That one depends on the cartridge used. Put it right after one of the analog inputs.
The AC1/femto has been listed for years, but we're still waiting for it. See the audio controller forum for some information about it.