›
Please review the site Rules, Terms of Service, and Privacy Policy at your convenience. Rules, TOS, Privacy
Get familiar with the reaction system: Introducing the Reaction System

Recommended amp switch box btwn a SS and a Tube amp (for one set of speakers) ?

tajanestajanes
in DIY

The main issue I have come across is the need for the tube amp to always have a load…  also would be great if included adjustable output to balance the levels to the amps 

Not so much to be used as an A/B test unit (as flipping tubes on and off cause havoc), but when watching TV (if not a concert, etc.) no need to warm up the room with a tube amp…

Can I assume using Y splitters from the pre-amp signal out to both amps – where only one on at a time- is not as issue? Or do both the input and outputs need to be completely separated?

Thanks

Andy

Comments

  • Tom_STom_S
    That's a tough one - you'll need a custom solution for that. I would think someone with basic programming skills could use an arduino to switch some relays on a slight delay. Engage a load for the tube amp, then disengage that amp from the speakers, and then engage the SS amp to the speakers. I think you'll want to switch both the + and - lines on each amp. The Dynacos ground the common (Neg) lead on the secondary of the OPT and that may cause issues with some SS amps.

    Hard to say if you really need to switch the inputs. Most tube amps have a fairly high input impedance, so in parallel with the SS amp, it probably won't drop the imp down to a point where your preamp would have a problem driving it. 
  • WolfWolf

    Highly agreed. If you want to scale for switching both leads, I built a 3-pair relay-driven speaker switcher awhile back (see above). Since mine is for speakers, I used a common negative.

    You need a PC PSU, with both 5V/12V supplies if you build like I did. Anything more than 60W is likely adequate. 5VDC runs the LED indication of what is currently engaged, and the 12VDC runs the relays.

    The problem will be the mandatory load of the tube amp outputs. Will a Boucherot (CR filter of 0.047uF/12ohm) cell be a sufficient load for a tube amp? I really don't know the answer to that. I included them on the input to the switcher so that amplifiers used are always terminated while make/break occurs. I also have avalanche PTCs (Z131-20UL) across the outputs and 5A fuses at the input after the CR Boucherot.

    I used high current SPST Bosch-style automotive relays, but really, anything over 30A should have low enough contact resistance.

    I'm sure something could be adapted to work for you using 8x SPST relays for both +/- connections. I had help from several sources to make sure this was stable and secure, even though it should not be switched under high output load if at all possible. If running a few watts, I have no doubt it will function as it should as constructed.


    InDIYana Event Website

  • tajanestajanes
    Tom and Wolf,
    Thanks for your input.  Probably best for me to just set-up a series of DPDTs and have both amps off before toggling...  
  • WolfWolf
    ...and make sure nobody else throws the switch and fires up the tubes without a load. If you are the only user, then this is a moot point.

    InDIYana Event Website

  • PWRRYDPWRRYD
    Firing up a tube amp with no load is not a guaranteed distaster as is often stated on the internet.  But it's always better to be safe than sorry when dealing with pricey tubes and output transformers.
  • tajanestajanes
    or, sell my tube amp and put in a tube buffer for the upper range- ouch
  • tajanestajanes
    found this Niles amp switch box- thinking this plus a 100ohm 5w resistor across tube common and 8ohm pos tap output to provide load, AND to be safe do the switch with both amps off
Sign In or Register to comment.