spaceace76 wrote:here's the basic schematic made by peter of clinch fx himself, posted on another forum
for the 18 volts, a simple charge pump will do, see this page for info
i don't think clinch uses that particular chip, but it'll work just fine. he also recommends using some small value caps
you can use a 2n5457 instead of the very tough to find TIS58. i scored some NOS TIS58's on eBay, couldn't hurt to look i guess. the only thing i'm not certain of is how the volume control is hooked up. i haven't had the chance to experiment with the circuit, so that's up to you. other folks here have probably tried it out too, maybe they can be of assistance. hope that helped!
clinchfx wrote:Spaceace, we've talked before via PM. How are you?
spaceace76 wrote:I've heard you've been in and out of commission due to heath reasons, and I'm always glad to hear about someone getting one of your pedals in the mail since that means you're doing better. I hear it a lot too, the pedal is a big hit!
Thanks for the info, and stay well!
clinchfx wrote:The output impedance is very important to the phase response of the EP-3 preamp. There's another guy selling PCBs for what he claims is the same thing as an EP-3 preamp, but he just connected a 50K pot to the end of the snippet of schematic that I posted, and that just doesn't cut it.
clinchfx wrote:You didn't by any chance send some of your Melbourne weather up here??
It's cold, wet and miserable here in Brisbane today
clinchfx wrote:Those are nice builds - good shortest path wiring instead of long wires with right angle bends running right around the box Long straight wires with right angles everywhere may look neat to some, but that kind of thing is rarely electrically neat.
clinchfx wrote:I saw your Veroboard (stripboard) layout at FSB. You seem to have gone closer than anyone else to approximate the output impedance of the EP-3 preamp and you've used a 500K pot Without giving anything away, I suggest that you look at the Echo Volume pot on the original Echoplex schematic - I think you probably have a copy. Notice that the pot is not in the main signal path. The wiper of the pot is grounded, therefore the function of the pot is to control the output by bleeding signal to ground, not to pass signal to the output socket.
There has been talk of "correcting" the high output impedance of the circuit, but the high output impedance is one of the things that sets the EP-3 preamp apart from a common JFET preamp. Your SPDT switch will give you more output and lower output impedance, but at the expense of some of the special sound of the real thing. As I said in an earlier post, the EP-4 has a low impedance output buffer, and it is not regarded as having that Echoplex magic.
clinchfx wrote:Also, be aware that changing the capacitor across the source resistor will have a major effect on the phase response of the circuit. Phase response really does have an effect on the way we hear things. BBE have used phase response modification for a long time. Before BBE, Bose used an equalizer to alter phase response in the 901 and 802 series speakers, to create that "in your face" larger than life sound. There is a good write-up about phase response from Analog Devices http://www.analog.com/library/analogdialogue/archives/43-09/active_filters.html It is written for active filters, but it does explain the concept of phase response.
clinchfx wrote:Hope this helps,
Xplorer wrote:very interesting, for my echoplex.
i'm restoring it, and i'd like to have some spare parts, for som replacements if needed. the TIS58 seems ok, but i'd like to have some pieces in my stock. so, the 2n5457 would be the best replacement ? what hfe would be the best, when selecting the rght one ? are there some other transistors that would be good , or even better ?
it's possible to find some TIS98, but quite impossible to find some TIS58 ...
my echoplex is gonna be a monster, with cool mods ; )
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