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PostPosted: Sun May 17, 2020 2:00 pm 
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viewtopic.php?f=14&t=3264 Might give you a starting point and maybe PM Coco if no one else replies.

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PostPosted: Sun May 17, 2020 9:35 pm 
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zaphod wrote:
+! to kurtlives' comments.

Basically, the VRM/power scaling concept doesn't really work well with Hiwatt type amps. These aren't Marshalls. When developing the Triwatt, which is based very closely on classic Hiwatt designs, it became very clear that there was a specific voltage sweet spot for the right classic Hiwatt tone. If you went much above that, it started to sound shrill. If you went below, it got mushy and lost definition. Just use the built-in MV. If you wanted to add anything to that, you could also install a post-PI MV, which a few folks have tried with regular Hiwatts and appeared to work well.

Sorry, thought Zaphod's comment about a volume pot after the phase inverter might work for you. :oops:

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PostPosted: Mon May 18, 2020 11:26 am 
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matt_garman, as for PPIMV controls, if you're not familiar with them, google, the different types of PPIMV controls. There's an amp guy that wrote some "pages" and in them is contained different types. (Not sure if I'm allowed to say who wrote them of the name of them, I'm not familiar on copy-write.) Specifically do some research on Type 3 master volumes. There are a few different types and they all have pros and cons. I've modified a "presence" control in an amp that I had, which was basically a cut control from old voxes. Turned it into a type-3 master volume. It's very similar to (and may actually also be called) a crossline master volume. Check out the schematic for the TC15, I think it uses this type of master as well.


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PostPosted: Mon May 18, 2020 2:06 pm 
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Matt: Yes, there are various ways to do PPIMV. Most of them use a dual gang pot to vary the two signals coming out of the phase inverter before they get to the output tubes.

The resistor mod you proposed sounds feasible. It would be easy to test the mod out to see if it does what you want. Just remove the wire going to the master volume control and clip in a resistor. If that doesn't work you can experiment with PPIMV.


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PostPosted: Sat Feb 25, 2023 5:32 am 
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Yes, it's definitely possible to add a "bedroom mode" switch to your Triwatt to limit the volume ceiling. Essentially, you would be adding a fixed resistor in parallel with the master volume pot to reduce its sensitivity.
phrazle


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PostPosted: Fri Jul 14, 2023 6:12 am 
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That's a lot more sophisticated than what I'm proposing, which has nothing to do with variable-voltage regulation (VVR). From what I can see, VVR allows the power tubes to be operated at a lower voltage, which not only lowers the overall volume but also keeps power tube breakup/distortion within reasonable bounds. To put it simply, Hiwatt-style amplifiers aren't well-suited to the VRM/power-scaling concept.
mini crossword


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PostPosted: Tue Oct 17, 2023 11:20 pm 
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Adding a resistor with a switch to control the volume in your tube guitar amp is a feasible idea and can be done retro bowl unblocked


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PostPosted: Sun Mar 03, 2024 10:03 pm 
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Your idea sounds quite interesting and could work if done properly. Using a resistor to reduce the input voltage of an amplifier is a way to reduce the amount of volume, creating a lower sound level. fnf


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PostPosted: Fri Mar 22, 2024 10:26 am 
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It appears that the VRM/power scaling concept may not be suitable for replicating the classic Hiwatt tone due to voltage sensitivity. Utilizing the built-in MV or post-PI MV could be preferable. Stay solar!


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