Hiwatt Lead 100 (OL103) mods

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Rockwell666
Posts: 136
Joined: Mon Nov 21, 2016 4:56 pm

Hiwatt Lead 100 (OL103) mods

Post by Rockwell666 »

Hi Folks,

I got this Biacrown era Hiwatt years ago, it had sat in a garage for pushing 20 yrs with the serial plate and tolex removed But I recapped it and its been in the jam space for years but doesn't get used as often as id like. the Overdrive is very lackluster. I normally have it rolled back for a more traditional hiwatt tone but I really want to get it to crunch up abit more and abit smoother. Wound up with either the normal or brilliant channels dimed and the overdrive control dimed it still has a nasally tone.
Resale wise, this amp is beat to hell. oxidation is everywhere from the crap storage. So i am not very worried about devalueing a vintage amp. Id rather mod it and use it more then I have been.

So with that said, looking at the schematic ( see attachment) im thinking this:
1- after the brill volume control there is a 470k series resistor. I want to change that out for a lower value. I am thinking 220k to start. (leaving the normal channel alone)..im alittle worried about blocking distortion being generated here.
2-The overdrive pot is 500kA. I am thinking to change it to 1Meg for some more signal to be passed and perhaps a small brite cap across the pot for alittle more crunch clarity. (220p im goona try first)
3- Lastly V2b has a 47n cathode cap and V2a has nothing. Im thinking that 47n is just alittle too small and maybe to try 0.68 or 1uf.

4- OR JUST CASCADE THE TWO CHANNELS?

This is all front end work. Hiwatts tone stack and P.I/presence circuit will be left unchanged.
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Rockwell666
Posts: 136
Joined: Mon Nov 21, 2016 4:56 pm

Re: Hiwatt Lead 100 (OL103) mods

Post by Rockwell666 »

for anyone interested I cascaded the two channels and holy bananas its heavenly.
Thickest high gain tone I have ever heard. Its like a vintage Orange OR120 with added gain stages. It punches you in the chest and there is very little fizz. I changed nothing else. The amp has two GE 6CA7's and all original mullard 12AX7's.(halved impedance switch).
I built a super hot JCM800 clone 100w with the depth mod etc etc and the hiwatt destroys it. I cant believe it!! Clips will be coming as we are hitting the studio tomorrow.
Last edited by Rockwell666 on Mon Jan 30, 2017 4:20 pm, edited 1 time in total.
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martin manning
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Re: Hiwatt Lead 100 (OL103) mods

Post by martin manning »

Sounds interesting! Can you mark up the schematic to show how you did it and any other circuit changes?
Rockwell666
Posts: 136
Joined: Mon Nov 21, 2016 4:56 pm

Re: Hiwatt Lead 100 (OL103) mods

Post by Rockwell666 »

simply removed wire from normal volume pot wiper on the pcb and ran to the Brite channel input jack switch to route the signal through normal channel then brite channel. Its noisey as hell as I didn't use any shielded wire. I will need to replace some plate resistors and put in some quieter tubes but it is the most crushing amp I own now. You can play the brite channel stock.
This is worth doing the audio engineer doing our recording this weekend said it sounded like High on Fire right out of the gates :-)

No other changes.
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martin manning
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Location: 39°06' N 84°30' W

Re: Hiwatt Lead 100 (OL103) mods

Post by martin manning »

Great, a one-wire mod for Hiwatt. Thanks!
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