Hiwatt Super Hi 50 Marshall mod

  • Thread starter Thread starter RedPlated
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RedPlated

RedPlated

Well-known member
I love my Super Hi 50 and wanted to see how the preamp would sound with a Marshall power section.

This is a 77’ JMP 2203. I converted the preamp to Super Hi spec. This is on 3 stages, plate driven tone stack. I will add the 4th stage and switching soon.

I love the sound. Might prefer it to the Hiwatt. This is pretty much fresh off the bench. Haven’t had time to play with fine tuning it.

 
Sweet! Can definitely hear the thicker first stage compared to other typical Marshall mods.

I think in this context, it might benefit from lowering the slope resistor down to 39K.
 
Yeah I think I too can hear a thicker tone that I assume was needed for the weird Hiwatt PI and driver. I’m so glad you did that and posted it because I was waffling on modding my DR103 clone. That Hiwatt PI concerned me since I know how much I love the Marshally LTP.
 
FourT6and2 said:
Sweet! Can definitely hear the thicker first stage compared to other typical Marshall mods.

I think in this context, it might benefit from lowering the slope resistor down to 39K.
Click to expand...
I’m going to get the 4th stage in and a relay added to switch it in and out. I already added a 12vdc switching supply for the heaters and to power the relay. Then I’ll do some tweaking for sure.

I realized I omitted the 100k from the v1b coupling cap to ground before the 220k/150k divider into the next grid.

Adding the resistor made the amp much tighter and articulate, as would be expected. I even lowered it to 68k and loved it. But it sounds killer without it too. I may add a switch to go between a 680k /68k here to really change the character of the gain.

I have 3 extra inputs now so those must be filled with switches! One will activate the 4th stage relay.

I also switched up the master setup. I have the tone stack coming out of treble pot, into a 1M master and then into one of my active fx loops. Seems to be a much better way.
 
RedPlated said:
I’m going to get the 4th stage in and a relay added to switch it in and out. I already added a 12vdc switching supply for the heaters and to power the relay. Then I’ll do some tweaking for sure.

I realized I omitted the 100k from the v1b coupling cap to ground before the 220k/150k divider into the next grid.

Adding the resistor made the amp much tighter and articulate, as would be expected. I even lowered it to 68k and loved it. But it sounds killer without it too. I may add a switch to go between a 680k /68k here to really change the character of the gain.

I have 3 extra inputs now so those must be filled with switches! One will activate the 4th stage relay.

I also switched up the master setup. I have the tone stack coming out of treble pot, into a 1M master and then into one of my active fx loops. Seems to be a much better way.
Click to expand...

That 100K is important. It really helps shape the feel of the amp as you discovered. In typical Jose mods with dual gains, I like 68K to ground and then 68K feeding the next stage. All personal preference.
 
FourT6and2 said:
That 100K is important. It really helps shape the feel of the amp as you discovered. In typical Jose mods with dual gains, I like 68K to ground and then 68K feeding the next stage. All personal preference.
Click to expand...
Same here on the Jose’s. I prefer 68K. 100K just feels a little too loose and grainy.

I just added a 3 way switch on this amp. One setting is stock 100k. Then 68K and a 680K.
 
Sounds great, good idea to try it with a regular PA
Pretty gained up for only 3 stages too
 
4th stage is in. And switching relay. Sounds killer on 4 stages. It’s nice having the Marshall power section, especially the presence circuit.

A lot going on around that tube. I haven’t even changed the stock grounding in the amp yet but it’s really quiet, even on 4 stages. It’s cool that you don’t have to add a tube, too.

IMG_3403.jpeg
 
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