A remote controlled Smash?

[ohshitgorillas]

I've recently gotten my hands on a pair of modded Magnepan MG12 speakers and a recently-serviced Hafler DH-500 power amp. I love the way it sounds, it's really stunning, and I think the addition of a tube preamp is just the thing it needs to take it from amazing to mind-blowing.

The problem: I'm lazy and my living room is big and I want to be able to control the thing by remote. I'm also kind of a noob at this DIY thing, but I have decent soldering skills, a good education and I'm persistent enough to figure things out as I go.

The potential solutions:

• Smash preamp
• http://www.amb.org/audio/delta1/ - AMB passive relay-based attenuator
• http://www.amb.org/audio/delta2/ - AMB passive relay-based input/output switch
• http://www.amb.org/audio/lcduino1/ - Arduino-controlled LCD screen to communicate with delta1 and delta2

One way to look at this would be as an AMB alpha10 stereo preamp with the Smash tubes in place of AMB's line amplifier, and in the Smash box. Another way to look at it would be as the Smash preamp but with an LCD screen on the front and without the need for any of the three knobs.

This post is just to try to assess the level of difficulty that this sort of build would require. If I were to mount the LCDuino screen into the front panel of the Smash, hide the delta1 and delta2 inside the box, and run a line from a cheap wall wart into the LCDuino... would the wiring just be as simple as, for example instead of running a lead from the active "input" to the stock attenuator, run it to the delta1, or instead of running a wire from the stock switch to a given input, I just run it to the delta2's designated input instead?

I'm also wondering if simply bypassing the attenuators would be possible for a line level output to a dedicated headphone amplifier, or if the signal should be attenuated at least somewhat.

Thanks for reading.

 

[Paul Birkeland]

This post is just to try to assess the level of difficulty that this sort of build would require.

You can use an external passive control to drive the Smash.  Cable in all your sources into the passive box, then run a short pair of cables into the Smash.  You can just leave the level control all the way up on the Smash, and there shouldn't be an issues.

I'm also wondering if simply bypassing one of the attenuators would be possible for output to a dedicated headphone amplifier, or if the signal should be attenuated at least somewhat.

The better way to do this would be with a tape output.  If your headphone amp has a volume control, then preattenuation shouldn't be necessary.

I have found that, despite the indications otherwise, that this board can be powered from the 6.3V winding on our PT3/7 power transformers.

The downside to this is that the control board is close to 12" long.  You could likely fit it in the Smash vertically with a bit of an angle, but that's about as helpful as I could be in this situation.  You can also remove the momentary push-button level control buttons and wire up an incremental rotary encoder in the volume pot hole to maintain some similar functionality to the stock kit.  The input selector button could also be replaced with a rotary encoder, though it won't be bidirectional.

I don't know how you would get the LCD display to work in a wood base, that will be tough.

Wiring this up and getting everything to fit will also be tough, and there won't be a ton of support available on our end.  Performing the machining and milling to make all of this look acceptable will be even tougher!

The DH-500 specs a 47K input impedance, you could just move your preamp significantly closer to your listening position and run longer interconnect cables.

-PB

 

[Tubejack]

This link is just a volume control, and may be a little more compact.  I have used these in my own builds. 
http://www.bentaudio.com/index2.html    It does need, however, 8-24V DC & 4ma idle, 75ma turning.

Or possibly you could just use the volume control portion of this unit (mcu board and motor pot), and run it off 6.3VAC.  You could hard wire your RCA's to the selector board instead of the one piece molded RCA bank to add selector capability - the smaller multiple boards may give you availabe space flexibility in an install.  (I have no hands-on experience with this unit.)
http://www.ebay.com/itm/4-Channel-Remote-Control-Volume-DIY-Kit-For-Tube-Preamp-Amplifer-ALPS-100K-LED-/181287112119?pt=LH_DefaultDomain_0&hash=item2a358dcdb7 or many similar on eBay.