Time Delay Relay

This is a "time delay relay" board" for tube amps and preamps. This is used on any amp or preamp where you want to delay the application of high voltage. The time delay allows the tube filament heaters to come up before any high voltage is applied. The time delay is nominally about 17 seconds but may be adjusted for more or less delay at the discretion of the user. There are complete instructions for the assembly and installation of the board. In a stock ST-70 the board replaces lugs 5, 6 and 7 of the 7 lug terminal strip. In a VTA ST-70/ST-120 tube amp kit, the VTA-TDB replaces the 3 lug terminal strip. The VTA-TDB may also be easily retrofitted to any VTA ST-70/ST-120 tube amp kit. The board is 1 7/8 inches wide by 2 1/2 inches long. It takes about 1/2 hour to assemble and is powered by a 6.3 volt AC line taken off V2. When the board is powered up a RED LED lights up to show that the board has power. About 17 seconds after power is applied, a GREEN LED comes on, and the relay kicks in to apply high voltage to your amp. Another nice thing is that if you are in an area that has quick ON/OFF/ON power interruptions the board will automatically reset itself. In other words, if your power goes OFF and then ON again a split second later the board will automatically reset itself and no high voltage will be applied for another 17 seconds. The board will soon be an option (August 2011) on all VTA ST-70 and ST-120 amp kits. The VTA-TDR KIT will sell for $35 + $5 shipping or $45 assembled with shipping. This is only a delay board - you still need a solid state or tube rectifier to plug into the rectifer socket. If you use a GZ34 tube rectifier IMHO you can get by without it. If you use a solid state rectifier like the Weber WZ68, which only has a 3 to 5 second delay, I think it is helpful. It would also be helpful if you have the quick ON/OFF/ON power interruptions. The minute you interrupt the power the board will resequence itself and you won't get any high voltage again for 17 seconds after the power comes back on. This board is primarily intended for those running amps withOUT a tube rectifier, like most of the ST120 amps that Bob is selling with the Weber SS rectifier. If you have a tube rectifier you already have a slow turn-on. This board is a relay switch that will not apply the high voltage power to the amplifier until after the tube filaments are warmed up, the board has a 17 second delay and that can be changed by changing one resistor on the board. The can also be used in any preamp that has a solid-state power supply, such as the Transcedence Sound Grounded-Grid preamp, and most all of the AIKIDO preamps sold by Glassware. Another possible use is as a speaker delay mute in an amplifier or preamplifier. This is a very heavy duty industrial relay used for 270vac 3 phase and rated at 8 amps, with 1500v of isolation between the contacts. Similar delay circuits I evaluated for tube amp use had 240v contacts with 1000v of isolation and were physically larger, this is a great addition to your tube amp. It can run on 6vAC or 12vDC.

TDR KIT $35

TDR assembled ready to install $45

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