https://theultimatetone.com/ Mon, 11 May 2026 12:48:01 +0000 MyBB https://theultimatetone.com/Thread-Pentode-triode-switch Sat, 25 May 2024 19:28:52 +0000 jmcd]]> https://theultimatetone.com/Thread-Pentode-triode-switch I have two related questions about that resistor:

1. Should it be included?
2. What should its power rating be?

  triode pentode switch-2.png (Size: 24.08 KB / Downloads: 20) ]]> I have two related questions about that resistor:

1. Should it be included?
2. What should its power rating be?

  triode pentode switch-2.png (Size: 24.08 KB / Downloads: 20) ]]> https://theultimatetone.com/Thread-Random-Access-Footswitch Wed, 13 Oct 2021 15:28:44 +0000 Strelok]]> https://theultimatetone.com/Thread-Random-Access-Footswitch

In TUT2 there is a random access footswitch, built around a 74175.


It works perfectly with alternate switches set up as momentarily.

Very cleverly done!

I'm trying to use normally open momentaries but I can't get it to work.
I tried moving the 10K pull-ups to become pulldowns by connecting them to the ground rail, but no go.
Can this only be done with normally closed momentaries?

Or do the diodes need to change direction?


Talk to you later,


Strelok]]>

In TUT2 there is a random access footswitch, built around a 74175.


It works perfectly with alternate switches set up as momentarily.

Very cleverly done!

I'm trying to use normally open momentaries but I can't get it to work.
I tried moving the 10K pull-ups to become pulldowns by connecting them to the ground rail, but no go.
Can this only be done with normally closed momentaries?

Or do the diodes need to change direction?


Talk to you later,


Strelok]]> https://theultimatetone.com/Thread-On-Off-switching-for-preamp-tubes Wed, 22 Sep 2021 18:54:06 +0000 Kai]]> https://theultimatetone.com/Thread-On-Off-switching-for-preamp-tubes
I just posted another thread concerning power tubes. In this thread I would like to raise a similar problem.

I built all LP preamps during the last years. I have a standard layout with one PSU-PRE and two LP preamp boards in one rack unit. For example there is my "British preamp" rack unit with M-PRE and V-PRE. With a simple SPDT I switch between outputs of M-PRE and V-PRE. The SPDT is connected to the main preamp output jack. 

Most of the time I only use either Marshall or Vox sounds while I'm playing. This means, one preamp board including heat dissipating preamp tubes is permanently turned on but not used.

Is there any mechanical switching that would turn off the B+ plate supply and the heater feed at a time between PSU-PRE and for ex. M-PRE respectively V-PRE? Maybe anything better?

Unfortunately, most DPDT switches can only handle DC voltage up to 250V. B+ plate supply usually is much higher. The heater feed can easily be broken. It is 12 V AC from the power supply.

Can anybody help me?

Best wishes 
Kai]]>
I just posted another thread concerning power tubes. In this thread I would like to raise a similar problem.

I built all LP preamps during the last years. I have a standard layout with one PSU-PRE and two LP preamp boards in one rack unit. For example there is my "British preamp" rack unit with M-PRE and V-PRE. With a simple SPDT I switch between outputs of M-PRE and V-PRE. The SPDT is connected to the main preamp output jack. 

Most of the time I only use either Marshall or Vox sounds while I'm playing. This means, one preamp board including heat dissipating preamp tubes is permanently turned on but not used.

Is there any mechanical switching that would turn off the B+ plate supply and the heater feed at a time between PSU-PRE and for ex. M-PRE respectively V-PRE? Maybe anything better?

Unfortunately, most DPDT switches can only handle DC voltage up to 250V. B+ plate supply usually is much higher. The heater feed can easily be broken. It is 12 V AC from the power supply.

Can anybody help me?

Best wishes 
Kai]]> https://theultimatetone.com/Thread-On-Off-switching-for-pairs-of-power-tubes Wed, 22 Sep 2021 18:30:49 +0000 Kai]]> https://theultimatetone.com/Thread-On-Off-switching-for-pairs-of-power-tubes
to cut along story short, I have a PA-10 with two boards, each  with a pair of tubes. A PA-66 with two EL34s and a PX-66 (actually a cut PA-66) that carries two 6L6s. I regularly use either EL34s or 6L6s. Since there is a lot of heat under the hood, I would like to turn off the pair I don’t use while playing through the other one. I'm not talking about muting, rather about powering on/off. 

In TUT, p. 6-57 there is a paragraph on Cathode switching as a stand-by for power tubes. Is this the best way to reduce heat? I am thinking about a solution that completely turns off either the EL34 or the 6L6 pair if technically possible.  

Is there any mechanical switching that would turn off the B+ plate supply and the heater feed at a time between PSU-PA and PA-66 respectively PX-66? Maybe anything better?

Unfortunately, most DPDT switches can only handle DC voltage up to 250V. B+ plate supply usually is much higher. The heater feed can easily be broken. It is 12 V from the power supply.

Can anybody help me with this issue?

Best wishes 
Kai]]>
to cut along story short, I have a PA-10 with two boards, each  with a pair of tubes. A PA-66 with two EL34s and a PX-66 (actually a cut PA-66) that carries two 6L6s. I regularly use either EL34s or 6L6s. Since there is a lot of heat under the hood, I would like to turn off the pair I don’t use while playing through the other one. I'm not talking about muting, rather about powering on/off. 

In TUT, p. 6-57 there is a paragraph on Cathode switching as a stand-by for power tubes. Is this the best way to reduce heat? I am thinking about a solution that completely turns off either the EL34 or the 6L6 pair if technically possible.  

Is there any mechanical switching that would turn off the B+ plate supply and the heater feed at a time between PSU-PA and PA-66 respectively PX-66? Maybe anything better?

Unfortunately, most DPDT switches can only handle DC voltage up to 250V. B+ plate supply usually is much higher. The heater feed can easily be broken. It is 12 V from the power supply.

Can anybody help me with this issue?

Best wishes 
Kai]]> https://theultimatetone.com/Thread-Help-with-Relay-Switching-ala-the-Jim-Kelly-Project-SOLVED Sat, 09 Feb 2019 17:17:11 +0000 makinrose]]> https://theultimatetone.com/Thread-Help-with-Relay-Switching-ala-the-Jim-Kelly-Project-SOLVED
The pre-amp I'm using different than the Jim Kelly but the concept of how I wanted to switch the channels is the same.  My problem is the when I switch channels the relays I'm using are make no connection at all when the panel channel switch is in the open position.  When it is closed and grounding the relays go the Normally Closed position. 

I'm using the Hammond 272JX and using the 5V taps with the same power supply circuit as the Kelly project.  I'm using this 12V relay: http://www.futurlec.com/Relays/DS2Y-S-DC12V.shtml

With the panel switch closed I'm getting ~12 VDC on the positive terminal on the coil and 0 VDC on the negative terminal.  With the panel switch open I'm getting ~13.5 VDC on both the terminals. 

Any ideas?  Thanks!]]>
The pre-amp I'm using different than the Jim Kelly but the concept of how I wanted to switch the channels is the same.  My problem is the when I switch channels the relays I'm using are make no connection at all when the panel channel switch is in the open position.  When it is closed and grounding the relays go the Normally Closed position. 

I'm using the Hammond 272JX and using the 5V taps with the same power supply circuit as the Kelly project.  I'm using this 12V relay: http://www.futurlec.com/Relays/DS2Y-S-DC12V.shtml

With the panel switch closed I'm getting ~12 VDC on the positive terminal on the coil and 0 VDC on the negative terminal.  With the panel switch open I'm getting ~13.5 VDC on both the terminals. 

Any ideas?  Thanks!]]> https://theultimatetone.com/Thread-Channel-switching Wed, 22 Aug 2018 19:22:46 +0000 K O'Connor]]> https://theultimatetone.com/Thread-Channel-switching
Channel switching is the most common requirement in guitar amps as far as having any kind of "switching" system. It is truly quite simple, but can be made "too simple" sometimes impairing the ergonomics for the player.

As we know from "The Ultimate Tone" (TUT) series, ANYTHING can be put on a switch and once you've done that, all the switchable things can be synchronised and/or be made remotely accessible, all at the whim of the builder or player.

London Power offers a range of switching kits and has a PDF to make selection easier.

Switching can be done using relays, transistors (BJTs), jfets, mosfets and even tubes, depending on what needs to be switched. Sometimes the simplest circuit can turn out to be tricky to design or to get working reliably, but we will show step-by-step methods of design and get you to a satisfying finish.

Have fun]]>
Channel switching is the most common requirement in guitar amps as far as having any kind of "switching" system. It is truly quite simple, but can be made "too simple" sometimes impairing the ergonomics for the player.

As we know from "The Ultimate Tone" (TUT) series, ANYTHING can be put on a switch and once you've done that, all the switchable things can be synchronised and/or be made remotely accessible, all at the whim of the builder or player.

London Power offers a range of switching kits and has a PDF to make selection easier.

Switching can be done using relays, transistors (BJTs), jfets, mosfets and even tubes, depending on what needs to be switched. Sometimes the simplest circuit can turn out to be tricky to design or to get working reliably, but we will show step-by-step methods of design and get you to a satisfying finish.

Have fun]]>