Introducing the HoSo Super Lead Overdrive

[darkbluemurder]

Hi,

Following the discussions in this thread

http://www.el34world.com/Forum/index.php?topic=8989.0

I finished my Liverpool conversion. Attached is the schematic for the HoSo SLO. This beast can do high gain as well as cleaner tones. So far I am really pleased.

Any comments are welcome.

Cheers Stephan

[Bierschinken]

Moin,

pretty small, can´t figure the partvalues 

Swen

[tubenit]

The schematic is unreadable. Can't make out any values on it at all.

Take a SCH schematic ......... save it to bitmap ........... resave it to GIF ............. hit EDIT ......... (under Image) click on strech/skew and stretch it smaller to 45% X 45% ............. then post it.

Then everyone can actually read it and give you positive feedback!   

I'd be very interested in seeing what you came up with.

With respect, Tubenit

[bnwitt]

print to PDF

[darkbluemurder]

Sorry for that. I saved the schematic in a larger file. This should work better now.

Cheers Stephan

PS: The SCH-Program does not work on my computer.

[darkbluemurder]

I attach a file with bigger images. Hope that works better.

Cheers Stephan


EDIT:  I attached the same schematic as Stephan but in a size that allows larger sections to be read.
With respect, Tubenit

[darkbluemurder]

Tubenit,

Thanks for adapting the schematic. I have replaced the schematic in my first post with one that has your suggested picture size of 1404 x 992 pixels.

I checked the SLO schem once more and found that the plate voltage of the direct coupled pair is a lot closer to half the B+ voltage than mine. I guess I will adjust the plate resistor to get the plate voltage down to about 180V. I guess this will be achieved by using a 220k resistor together with a 1.8k cathode resistor.

I also thought about adding the typical 1uf cathode bypass cap but then I will have to make it switchable. Otherwise I am afraid that there is too much gain permanently installed. 

Cheers Stephan

[mtman5821]

Stephan,

How well does that 100K mid pot boost work?  I am thinking of applying this to my 56T(HoSo variant) project.

[darkbluemurder]

It works really well although not as extreme as I thought it would. This is probably because with only the 470k resistor to ground after the treble control there is not much attentuation. I came to this conclusion because the Bump section in my HoSo56 works more extreme when the pre PI volume is at lower settings. I may change the 470k resistor to ground to a 220k/220k voltage divider to drive the PI less hard and get cleaner sounds easier and still have a massive midboost on tap when I want it. We will see - I could change the 100kA mid pot to a 250kA to get even more boost but then there certainly comes the point of diminishing returns.

Cheers Stephan

[darkbluemurder]

I made some further tweaks this weekend to expand the vocabulary of the amp. The 47k resistor after the treble wiper forms a voltage divider with the 470k to ground for a small attentuation and a slightly cleaner tone.

The 220k plate/1.8k cathode resistor combination provides a bit more gain in V2. The switchable 1uf cathode bypass cap provides for even more gain.

The current schem is attached.

Even though I focussed on the overdrive tones this time around the amp is still far from being a one trick pony. It can do nice cleaner tones but of course it excels at overdrive sounds which easily reach into high gain territory by engaging the bright and the boost switches.

I consider that amp done for now, except maybe for the power amp where the 180R cathode resistor still runs the EL84 quite hot (almost 14W idle) but unfortunately I am fresh out on 220Rs.

Cheers Stephan