Adding a Pre-Out to an integrated tube amp

millercarbon,

     I may be mistaken, but I thought the main benefit of speaker level connections was for powered subs, that accept speaker level inputs, with the sub's input coming from the speaker level outputs of your main speakers' amp or amps.  The idea being the matching or blending of the sound and characteristics of your subs and mains more seamlessly.
     Of course, it's your system but I just wanted you to know, imho, that if there are any sq benefits they will be very subtle and likely not worth the effort. 
     Prior to the Swarm, a local dealer here in Indy let me borrow a couple of smaller REL powered subs for 2 weeks that had both line and speaker level inputs.  I experimented with many different locations for these subs in my room and I compared using line vs speaker level inputs at each new positioning of the subs. Both methods sounded very good to me but I honestly couldn't convince myself I heard a benefit to either method.  I switched to just line level inputs rather quickly, mainly to save time but I honestly could not distinguish between the two.  You may be able to but I'd still suggest not setting your expectations too high.
     I run all my subs via line level and the bass response quality and integration with my mains is exceptionally good.  The hookup is simple and easy.  Just thinking of what you're planning on doing is hurting my head.

Best wishes,
    Tim

     I may be mistaken, but I thought the main benefit of speaker level connections was for powered subs, that accept speaker level inputs, with the sub's input coming from the speaker level outputs of your main speakers' amp or amps

I think of it more of a convenience feature. They don't implement a high pass filter since that would be expensive and prone to error due to variable nature of speaker impedance from model to model.

Line level crossovers can implement low and high pass filtering more consistently.

This is by far the simplest, clearest explanation of why and what and how to do it as I have been able to find. http://www.epanorama.net/circuits/speaker_to_line.html

There's also tons of LOCs I could buy, but they are all the same inside and so you are paying mostly for a box and some connections with hardly any of the budget going to the parts inside. Which, come to think of it, just described the majority of high end components! lol! But seriously, look at it- two 10k and two 1k resistors. Grand total $2 with tax, and I can pick em up at Vetco tomorrow.

The Melody has 4 inputs. I'm only using 2. So here's what I do:

Disconnect the internal wiring from one pair of input RCAs. Solder a wire from the hot leads of the speakers to the hot pin of the RCAs, with one 10k resistor in series. (See circuit diagram link above.)  Solder one 1k resistor across each RCA. Done.

Now the Melody amp sees a 10k load, which is insignificant, and the Dayton sees a 1k impedance, which is fine. The line voltage the Dayton will see at the max output of my amp is about 2v, maybe 3v, which again is fine. Well within the Dayton's level adjustment range.

This by the way is exactly what I've been doing the last 10 years running my Talon sub off the speaker outputs. Which I know. Because some guys posted the plate amp circuit diagram. The only difference is the location of the circuit- inside my amp vs inside the plate amp.

Solder two wires, and four resistors, slap a PRE-OUT label on the back, hook er up she's ready to go!

Thanks, guys!

Well I went to Vetco and bought two 10k and two 1k resistors, soldered the 10k in series with the speaker out, soldered the 1k across the RCA to ground, and guess what? Nothing blew. Works just fine.

The hardest part turned out to be getting enough heat into the speaker binding post to get a good connection. Cost me a grand total of $1.54 for parts. So even cheaper than the cheapest LOC, not to mention it looks a lot better (looks completely stock from the outside) and trick as hell because, mod!

And oh yeah- the Swarm is AWESOME!!!!