April 19, 2019 at 4:47 pm #5392
Here is my take on a Hornby Skewes Treble Booster using the Guitar PCB GBOF board. This one has been a long time coming. I completed the enclosure more than two years ago before I moved to Florida from Ohio. Over a year ago I put together the circuit board and switches, then put it on a breadboard to test the circuit before boxing it up, and of course it didn’t work. I wasn’t getting the proper voltages (they weren’t divided properly probably due to a grounding issue). I posted on the old board for help and then got frustrated and put it away for a year. Finally, about a month ago I decided to take another crack at it and after placing what I had done before on the breadboard, it worked fine and all the voltages were as they were supposed to be. Must have been some Gremlins.
So I boxed it up and of course it did not work, but the wiring was an awful mess due to the switchable input and switchable output caps. I thought I had planned out things well, but when boxing it up found out I did a lousy job of planning. I should have placed the rotary input cap switch in the corner of the board, which would have been on the side of board input, but unfortunately I had made the enclosure with the rotary switch going in the middle position at the top of the pedal.
So I disassembled the pedal and found the grounding issue. I lengthened a few wires to give me more room to work with and then carefully secured each component in the enclosure one by one testing the pedal after each one was secure. The pedal now works as it should. It has a 7 position input cap selector so different types of toneal variations can be chosen. At 22nF, it is in the stock HS Treble Booster position when paired with the 1nF output cap. With input and output caps selected at 10nF, you basically have a Linear Power Booster circuit. With the input cap at 5nF or 7nF and the output cap at 10nF, it puts you in the Rangemaster territory, although without a Germanium transistor. The larger input cap values give you a fatter boost. The output caps don’t seem to do much to the tone, although the higher value caps appear to provide more output. The pedal sounds great with input cap at 22nF to 68nF and the output cap at 10nF.
Below is a photo of the top of the pedal.
Below is a gutshot showing the spaghetti of wires. The way the pedal was configured ahead of time, as explained above, I just couldn’t get it any neater. I don’t think I am going to get as aggressive in the future modding a pedal with a multi-position switch due to the complexity – lesson learned!
Below is the basic circuit, although the cap values are slightly different. Input caps are 1nF to 68nF and output caps at 1nF (middle position) as well as 23nF and 11nF (the 22 and 10 positions) due to the additive effect of the 1nF cap which is paired with the other two. I added the 1nF to be paired with the 22nF output cap, one of the rumored combos for the HS. It gives a very thin trebly sound to the pedal and was an obviously wrong observation on the circuit. An A1M pot was used for the output control because it is what I had laying around.April 20, 2019 at 2:31 am #5400BarryKeymaster
Thank you for sharing and your thorough description!April 21, 2019 at 2:59 pm #5425wilkie1Moderator
This is a great detailed description of what can be achieved by changing cap values. If you are reading this, you might want to try the new ROTO-TONE DELUXE. It offers an easy way to do really neat component mods!April 23, 2019 at 8:46 am #5444
I totally agree with Wilkie. If I had only 4 input cap values instead of 7, I would have gone the Rototone way. I supposed I could have run two of them in parallel for even more input cap values, but that would have been even crazier than what I already was doing in the circuit. I do have a few Rototones for future projects such as an Electra style distortion with one Rototone for 4 clipping diode pairs and another switched Rototone with 4 single diodes to make an asymmetrical clipping option. I plan to pair this with a paramix to blend in the straight guitar signal. Crazy!
That is why this is a great hobby, although I think I may using some out of the box thinking on this, but just like everything else, somebody probably has already done this.April 23, 2019 at 1:02 pm #5447wilkie1Moderator
That’s great! Please check out the new options that the ROTO-TONE DELUXE offers. You may like to use some of them when you do your future mods.September 27, 2019 at 2:23 pm #6935
Here is a repost of the images. I changed image hosting sites due to multiple issues.
Below is a photo of the top of the pedal.
Below is a gutshot.
Below is the basic circuit, although I used slightly different input cap values and a 1M pot for the boost control as it was what I had laying around (would have used a 500K instead). Also I later changed out the transistor from an approximately 180 HFE 2N3904 to a similar gain S9013 because the 3904’s I tried I found radio interference in the background when I cranked things up. The S9013 and other transistors I tried didn’t have the radio interference for some reason. The PNP transistor in the original positive grounded circuit was 2N4081 that had gains around 90-330 HFE, so anything in that range should work.
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