A forgotten and quite odd one from the early days of EHX.
Despite being marketed as a "Microphone Echo" and having "Echo" as one of the labels for the controls, this is actually a tremolo circuit with some quirks. There is no "Depth" control as in most tremolo effects, instead there are the "Echo" control which adjust the output level for the LFO signal. "Volume" control adjust the clean signal. "Speed" adjust the LFO rate.
The schematic is redrawn from a factory schematic dated 1972. Some odd resistor values but I'm pretty sure closest common value will work. Also, the transistors is the same as in Triangle/early Rams Head Big Muffs. They are quite hard to source and Hfe is all over the place. 2N2222's or 2N3904 might be good subs.
Not much info on the web on this one but there is a short writeup HERE.
Nice. Sounds more like a Harelip-copter from the demo: https://www.youtube.com/watch?v=A5bze9-gWaE
ReplyDeleteWell, I built this and it works, kind of. I used it with 2n3904s everywhere and 150nFs instead of 120nFs. It sounds like it works, but the output really below unity gain. Any ideas what I could change? or maybe I'll just add a booster after the output
ReplyDeleteI'll try some troubleshooting/audio prbing, to see if it is a build issue. Thanks for the layout and the schematic!
DeleteOk, so both clean and LFO signal is below unity? You could adjust 124k and 68k resistor at the top left for smaller values. Or simply replace them with jumpers?
DeleteYeah, both below unity. I jumpered those resistors, and the output raised a bit - I would say it achieves unity when Volume is maxed. There is some noise, the pitch of which is adjusted by the speed pot. Rotating the pot above 7 o clock is already too fast. I don't think I made a mistake, but I will keep checking
DeleteNext I will triple check all of my resistors values, then change transistors, see if introducing C7 makes any difference and change the taper of the pot
DeleteDo you have the transistors in correct direction? If you are using 2N3904s you need to rotate all transistors 180 degrees.
Deleteyeah, I checked that, and the resistors, and checked if I had continuity in every strip... Introducing C7 attenuates the noise, but also attenuates the LFO signal as you increase it. 470pF/1nF is a compromise.
DeleteWell, the volume issue is completely solved by lowering the 10K from Q1 to ground. Turns out this one is a keeper :)
DeleteI think a pot in there would do very very nicely acting as Gain. In the extreme (jumpering emmiter to base) you get a pseudo-tremolo-fuzz. Very psychedelic indeed. I ditched the c7 cap, This one paid the effort! Thanks again for finding these amazing obscure pedals and making the effort!
i mean jumpering emmiter to ground, sorry
DeleteGreat job, Man! That mod makes total sense for increasing the volume since Q1 is basically a LÅB-1 booster... I'll add some notes regarding regarding R4.
DeleteI wish there was more gutshots online to verify the values but the schematic is what we have at the moment.
I'll tag it!
Cheers!
Hello all!
ReplyDeleteAs usually, fuzzhead did a great research work. Thank you!
I finished my clone, but it sounds as a ring modulator, not as a tremolo, and I can't understand why. My LFO's frequency is between 150 Hz and 500 Hz, which is much faster than a tremolo one.
Looking at the photo from https://sites.google.com/a/davidmorrin.com/www/home/trouble/troubleeffects/electro-harmonix-hare-lip, it's clear that R4 is 300 ohms (the little resistor in the right corner), which is an almost standard value for LPB-1 (it has a 390 ohms resistor in that position). Also, the 430 K resistor it's soldered on the backside of the PCB.
Looking at http://www.effectsdatabase.com/model/eh/harelip#pictures, I discovered that it was sold as a kit, so I wrote to the owner of Effectsdatabase site and asking to post the kit instructions. Maybe we will have luck :)
Thanks for clearing that out. Makes sense.
DeleteAnd thanks for reaching out to effectdatabase!
Bart from effectsdatabase replied to me and said that it will take some picture when he find the Harelip.
ReplyDeleteAlso, I forgot to mention that the 124K it's for sure 120K (left upper corner of the photo above).
@WTFiCanBuildMyOwnPedals: Your build sounds like in the Youtube videoclip or not? I mean, it sounds like a tremolo in terms of LFO speed?
ReplyDeleteThank you!
Yeah, it sounds like the demo, I don't think it is a very "tremolo"-like effect, in a sense that the dry signal fades out and fades in. The dry signal is controlled by the Volume pot. Then it adds some sort of choppy oscillating signal, its volume and rate are controlled by. I don't know if I am making myself clear, english is not my native language. But I hope this helps!
Deleteare controlled by Echo and Speed*
ReplyDeleteIt's very clear, WTFiCanBuildMyOwnPedals...my English is not my native language, too :)))
ReplyDeleteIt's clear that I made a mistake, but I didn't find it yet. My clone sounds as you said, but not as in the videoclip, because mine oscillates very fast, like a ring modulator. So, I have a ring modulator blender :)
Thank you very much!!!
I replaced both 10nF caps with 330nF caps and now my clone sounds as in the videoclip...very strange :)
ReplyDeleteInteresting! so you say those caps influence lfo speed? Mine oscillates quite fast, but the lower portion of rotation is quite useable. I will definitely try that.
DeleteThe LFO is an Astable Multivibrator: https://www.electronics-tutorials.ws/waveforms/astable.html. Very interesting is the fact that Harelip LFO is not symmetric, so the ON:OFF ratio is something like 1:4 due to 330K:1.2M resistors.
ReplyDeleteWhat means that your build "oscillates"?
@WTFiCanBuildMyOwnPedals: Can you measure the LFO of your LFO, please?
ReplyDeleteBy oscillation I mean the rate of the "tremolo" effect (once again, not a tradicional tremolo). A filter is a good way to describe it I think. You want me to measure the rate? When B100K speed pot is at 9 o'clock it's like in the beginning of demo video, from up there it gets fast. In the end of the demo video he uses slower speeds, I don't think mine gets as slow as the original.
DeleteThanks a lot, WTFiCanBuildMyOwnPedals! It's clear now, so no need to measure the rate. I made a mistake, for sure :)
Delete