Source Mod or Preamp?

 Hey guys,
   Was curious what people thought between two upgrade choices I was considering. Due to fixed disability and limited funds, I can only choose to save for one. I want to add some tubes into the mix, so I was looking at an Oppo Modwright Truth vs. say SP14 preamp. With the side upgrades, both should be around the same price.

   My question for people familiar with these two pieces is which one do you think would be a "better" bang for the money if you could only choose one? A tube mod Oppo I read is nice and can still feed directly into my amp. Or will running the stock Oppo though a nice tube preamp be the way to go?
  My equipment is very simple, so no need for many preamp connections (no TT, etc.) only an Oppo run directly into a First Watt J2, then to Spatial Audio M4s. I think adding a few tubes into the chain maybe nice, just not sure which I should save for, I have never heard either. Thanks in advance.

I’m don’t have experience with tubes, but if it’s one thing I have learned through a lot of R&D is that if the sound signature/quality is not there from the source, you are not going to get it back with any preamp magic. Not to say that the Oppo 105 sonics are bad -- they really aren’t, but adding a tube preamp is going to layer a tube signature on top of a solid state signature. Don’t get me wrong, this may work very well in a certain combination of equipment.

When you use the digital volume in the Oppo, the Oppo will convert the 16/24 bit PCM up to 32-bit PCM and then trim bits to reduce the volume. This supposedly works well, but I can’t keep thinking that something is lost because the DAC has to do processing on 32 different ladder voltages.  I don't know how Sabre does this, probably by re-using ladder pathways in a circular pattern (I definitely don't think it actually has 32 ladder resistors,  probably more like 11 if I remember right).

You could try doing the Modwright Oppo tube modification and then use something like a Khozmo stepped attenuator passive preamp for volume. I’d ask Modwright about the feasibility of this and which impedance value he recommends (if any) for the passive preamp.

Just an idea.

my choice has been to get a used ARC pre-amp

DACs evolve at a rapid rate but a good pre-amp will last years before a really significant upgrade in SQ comes along, so will be very cost effective to do the DAC every couple or few years

there is a new USB DAC out now that claims to have solved the galvanic isolation problem (iFI IIRC) and it is quite cheap

then there is your source material - even w/o going past the redbook std. there are huge improvements to be made from re-releases of any CDs you have from the early to mid-1980s

+1 to the post by AUXINPUT

Your source (and your resulting audio performance) can be significantly upgraded with a quality build upgraded  2-channel digital unit.

I had the very top end CAMBRIDGE Bluray player that shared the same motherboard as the OPPO. It was fine for HT but it was handily bested for 2-channel audio performance by my discrete high-end build CDP/DAC. The improvement was not subtle.

I think you are safer with a tubed preamp. I have a lot of experience with tubes and they are very good at adding dimension to your sound.  They will be very clean sounding and  not that's right not   syrupy slow and warm, using current production tubes.  If you want to add a hint of warmth there are some tubes that may help with that as well. 

Modded anything is harder to sell since there are fewer people familiar with the mods and are wanting to buy a specific component.  So if fluidity is important to you extensive mods are not a good choice.  The cost will likely exceed some of the less expensive tubed pre amp units.

ARC has a particular presentation that I think you should be familiar with before buying if you don't know how they sound already.   I own both an old ARC SP6B (modded) and a tubed pre, a simple AE-3 (an offshoot of Cary).  I love that little pre.