A couple o' variations:
EchoPlex Preamp with charge pump for 18V from a 9V supply
Early version EP3 with volume control
Tillman with Gain Switch
Monday, 12 May 2014
A Pair o' Preamps - Echoplex and Tillman
Just a couple of little preamps that have been requested. Some people swear by these little circuits and use them at the input of other effects because they like the way they colour the sound, so a quick build for people to experiment with.
A couple o' variations:
A couple o' variations:
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Tks!!
ReplyDeleteBut isn't this like regular buffers?
Cheers!
Is there a difference between this type of circuit and a buffer?
ReplyDeleteThey both boost the signal by some degree, buffers are usually unity gain.
ReplyDeleteThey're not buffers, they're boosters with a fixed boost set approximately by the drain resistor divided by the source resistor. They do have a high input and low output impedance like a buffer, but they're not unity gain source followers.
ReplyDeleteIf you wanted you could omit the source resistors and put an appropriate pot in there instead so you could set gain, but I just wanted to post them in their raw form, so you can use and adapt as you want.
What would you recommend for a gain control on the Echoplex?
DeleteI'd try a 5K with both
Deleteivlark
Delete5k pot? Log or liner? What source resistor are talking about? I am learning so much here on this site. What a great way to share! thank u for that! lol Cheers
Vince
Cool. Thanks. Will try the Echoplex...
ReplyDeleteMy first real build that wasn't a BYOC kit was the Tillman (with a knob). I made it for my girlfriend to use with her passive pickup ukulele. It fattens it up nicely.
ReplyDeleteThe EchoPlex schematic work to 18v....... You have another schematic?
ReplyDeletePut 18V into it then, as long as your capacitors are rated appropriately you can supply it with any voltage up to the maximum for the jfets.
DeleteThanks for the layouts lvlark. Really nice and thanks for your time. I enjoy so much!
Deletelol
Vince
Is the 3m resistor just a pull down?
ReplyDeleteCheers
Dave
No it also sets the input impedance, but you can still just use your closest resistor, it doesn't have to be exact
DeleteOn the echoplex one, would the gain pot simply be a 100k lin pot replacing the 100k resistor directly after the input?
ReplyDeleteYou could do it like that, but I don't particularly like the method of just increasing resistance in the signal path to affect the signal level going into the stage. I'd much prefer to leave the circuit true to the original and control the true gain of the stage by altering the ratio between the drain and source resistors, which I personally would do by replacing the source resistor with a pot.
DeleteThe Tillman can be made high gain with a cap from source to ground (I use a 10uf) on a switch. I recommend replacing the 51k resistor with a pot in this case. Then you have a preamp & light overdrive- it's my go-to OD.
ReplyDeleteDo you have a link to a schematic for the Echoplex?
ReplyDeleteThanks!
http://www.metalpunk.co.uk/Preamp.aspx
DeleteEchoplex Verified. Tested it on a Strat. It also sounds surprisingly good on my cheapo Hadean EB-510 bass as well.
ReplyDeleteAwesome, thanks for verifying matey
DeleteThis comment has been removed by the author.
DeleteTotal newbie here. Which resistors are the drain and source? The 22K and 3k3? Just want to make sure I'm understanding all this correctly. Just LOVE this site!!
ReplyDeleteYes 22K and 3K3
DeleteForgot to mention- audition J201s and play with the gain cap. Low values make a treble boost!
ReplyDeleteCheers
Hi,
ReplyDeleteHow must I connect the Gain Switch of the Echoplex on to the Veroboard?
Cheers, Jan
If you want to add a gain switch in the same way Peeps described for the Tillman, solder a 10u cap from the 2nd from bottom to the bottom row, with a cut to isolate the cap from the other components soldered on the 2nd from bottom row. Then one wire from the switch goes to the JFET source, and the other goes to the 2nd from bottom row so it connected to the cap you just soldered in.
DeleteHi Ivlark,
DeleteThank you for the explanation. Cheers, Jan.
Hi Lvlark,
ReplyDeleteCan it also been done with a Gain Pot (not a on/on swith, but a turning knob)?
I don't know the correct English word.
How must this be connected? The same as your 09.11 post?
Emitter to pot lug 3, lug 2 to the new 10u cap, lug 1 to ground
DeleteExcuse me Ivlark, could you expand on how to insert a gain pot? I'm just a novice and I tried replacing the 3k3 resistor with a b5k pot. the result was that the volume was practically zero. i took out the 220k resistor, but the effect volume still gets, at max, to 50% of the clean volume. Please help and thanks for your work!
Delete(i'm referring to the first echoplex preamp on top)
DeleteYou can verify the Tilman with gain switch. Sounds ok, just like a buffer type ciruit would, brings back the highs. The gain cap I'd leave in all the time, it makes the circuit a little louder so that you get just a little boost out of it.
ReplyDeleteCheers
Dave
Thanks for verifying that one mate
DeleteHello ,
ReplyDeleteDo you know any transistor replacement for the Echoplex?
Thanks.
Messbel.
The original used TIS98's or maybe TIS58's which will probably be difficult to find. Try any other JFET, I've suggested the 2N5457 in the layouts above.
DeleteOK , thank you so much. I've got a Belle Epoch from Catalinbread , used as a preamp it sounds really great , I'm gonna look inside and try to locate the JFET. I'll tell you what I'll see.
DeleteCheers,
Messbel.
i see this is based on the ep3 later model. in the schem the 100K and 1M resistors are supposed to be a 500KA pot for volume. cheers
ReplyDeleteThanks for the info. Do you mean that the early model used a 500KA pot instead of the 100K and 1M?
DeleteI requested the early EP-3 layout a while back and included a late model EP-3 to early EP-3 conversion schematic if that would help.
ReplyDeletehttp://guitar-fx-layouts.42897.x6.nabble.com/file/n1472/ep3_conversion_schem.jpg
The 220k and 100k resistors meet at lug 1 of the 500k pot - and lug 2 is going to ground.
That method with the pot wouldn't work very well when just building the preamp, because that is designed to ground the output from the preamp or the output of the echo head and by doing so alter the level of echo. So just a standard volume pot as we usually wire them would be the way to go. I'll add it. Now added
DeleteI found a few posts on various forums from Peter Clinch, who's EP-PRE is considered to be one of the finest EP-3 preamp pedals available. He addressed a couple of things that I'd like to share here as they appear to be important bits of info concerning output impedance and the 500k pot:
Delete"The output impedance of the Echoplex EP-3 is in the region of 200K. In designing the EP-PRE, I included a resistor network that would maintain an output impedance of 200K. I was aware that this may cause problems in some situations, but I tried a number of methods to reduce the output impedance, and found that they all detracted from the magic EP tone. Sadly, a number of EP pretenders have chosen to use those methods in their pedals."
"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."
Here's a (as Peter describes it) snippet of schematic that he also posted:
http://tinyurl.com/pp2js96
Hope this helps and thank you for all your hard work with this blog!
this whole thing makes me laugh. i've owned an ep3 for over 25 years. the circuit these guys are claiming is some "secret boost used by the pros" is bunk. the gent in the above post indeed brings it up. the purpose of this part of the circuit was to get a good signal to noise ratio to the tape, NOT TO BOOST THE GUITAR. it would boost the recorded guitar LOUDER than the dry signal, but never ever ever actually boosted the guitar signal itself.
Deleteat best, most of the plexes i've had (three so far) two were slightly below unity gain, and one just barely above.., which is my original one that i still have now.
the output impedance is for saturating tape. being a preamp, yes, you can use it for a guitar but it's never going to make anything sound like an echoplex.
echoplexes were never overdrives. ;) seriously. find someone that owns one, and put it in the loop of an a/b box.
nice sounding overdrive.. but echoplex?
still don't buy it. ;)
peace out
pjp
He's obviously wired it something like the schematic when it comes to the pot so that he can maintain the output impedance, but the snippet you posted doesn't match the EP3 schematic.
ReplyDeleteIn the schematic, after the output cap is a voltage divider with what appears to be a pot or trimmer to ground, and the 220K going to volume 1 and then a 100K from volume 1 to the output. The snippet has a 220K to ground and a 100K to the output.
I remain sceptical that the subtleties that he seems to believe are crucial make the difference between having a "pretender" pedal and sonic nirvana, but I've posted a layout anyway :o)
It's as per the EP3 schematic rather than the snippet.
Incidentally, if you do want it as per the snippet, then the first layout matches it. Cut the 1M pulldown resistor at the output if you want it exact.
DeleteQuestion: if I connect the ground from the input to the ground on the board there seems to be a shortcut (noise and no signal). But I can't find the cause.
ReplyDeleteSo just to be sure: the minus side of the 47u cap faces to the south right?
My transistor (2n5457) values are:
D 1.7V
S 1.25V
G 0V
I'm using the bigger greenies for caps. Could it be that they don't work properly? (I wanted to try them because they look so cool :)
So, when not powered I get a clean signal. When I power it, but not ground it, I get noise/hum and very lwo signal. When I power it, with ground, I get no sound at all.
Still a newbie (this is my fourth attempt in building pedals, but so far with little luck :P But I really want to learn it!
Is there something obvious I'm missing?
This comment has been removed by the author.
DeleteHello!
DeleteI've got similar values for the 2N5457:
D 1,45 V
S 1 V
G 0 V
Did you manage to make it work?
I'm getting very low signal on the output and with the pot (500kA) to the max, the same level as the "dry" signal.
Little help people? :)
Thanks for the site btw, really cool!
Hello
DeleteCurious If you were able to get more output volume since I am experiencing the same issue?
Yes, kind of. I've posted a question on the forum and I was told to get the output resistor out or decrease the value. This got me a little more gain. Not tons of it though but now it's noticeable...
DeleteHave you solved the issue?
DeleteHi All,
ReplyDeleteI've built the first version Echoplex posted here and it works. Nice easy build, good for a beginner.
I tried swapping the 3k3 for a 4k7 log pot but it didn't really work below half way, I got low level crappy sounding distortion, so I wired a 2k2 resistor in series with the pot and I now get a nice clean boost fully down and bit of crunch coming in at full vol/gain.
Thanks IvIark!
For the Tillman with the gain switch is it ok to use 2 prong on off switch?
ReplyDeleteFirst and foremost this is one fantastic site, great job love the info and the helpful hints and etc..
ReplyDeleteMy issue is that I am still at unity gain with the pot at max position ? All the demos I have watched show at least a 10db volume increase with the pedal at max. How can I remedy this and get a bit more volume level, please help.. Thank you and you guys ROCK 👍
Built the early version EP with volume control. Used a 2N5457; volume only got back to unity at full volume.
ReplyDeleteAlso noticed my 2N5457 has a different pinout than the drawing; mine is SDG, not DSG like drawing.
Any ideas how to fix? Has anyone built this version successfully?
Where does lug 3 of the volume pot go on the EP early version II?
ReplyDeleteBit of a newb, but I had a question. I'm planning on building the Echoplex preamp, but from what I can tell, it gives a slight boost. For my application, I don't want any clipping. Is there a way I could add an internal trim pot to adjust the gain (to prevent clipping) without altering the tonal characteristics or volume of the circuit? Thanks!
ReplyDeletethis really shouldn't produce enough of a boost to cause any sort of clipping, but you can make a typical output voltage divider and remove the 100k resistor at the output, and place a trimmer with lug one to ground, lug 2 becomes your new output, and lug 3 connected to the junction of the 100nF cap and 220k resistor.
Deleteanother option would be to look at the echoplex ep3 version 2 layout, which has a volume pot, and put a trimmer in the same location on the other echoplex layouts.
This comment has been removed by the author.
DeleteAhoy and thanks for some more great layouts!!
ReplyDeleteJust one question - I used the first echoplex preamp vero and a 2n5457 FET but i had to clilmb up to 8 kOhm for the source to ground resistance in order to bias the fet to 4.5V (the other 2n5457 that i had available reached 4.3volts or so). Does this sound normal? The sound seemed to be OK though, clean and sparkly! Looking forward to your response, thanks!!!
The more FETs you use, the more you'll realise that they're horribly inconsistent, just as you've seen with your own batch. What you've done is fine and correct. Its getting evermore so important to learn how to bias FETs in some of these layouts that don't include trimmers.
DeleteJust remember to bias by ear and not rely too much on the meter. A DMM will get you in the ballpark but only your ears know what you like the sound of.
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ReplyDeleteAnyone put this preamp directly into their guitar? I'm playing with the idea.. I put a klon buffer in my strat, but am thinking about the echoplex!
ReplyDeletenice pedal to boost an overdrive with :)
ReplyDeletehere's my take,it's the pedal to the right:
http://s29.postimg.org/g26u51m7b/IMG_0495.jpg
template as follows;
ReplyDeletehttp://s9.postimg.org/5tgm14qnj/echoplholes.png
Built the EP3 Early version with Volume and the volume does not change. Should lug 3 of the pot be connected to something? Thanks.
ReplyDeleteLug 3 does not connect to anything, also omit the 100k output resistor and create a jump over the cut where the 100k would have been, so that there is no cut in the line going to the output wire
ReplyDeleteThank you very much. That did the trick. It sounds a bit bright. Lots of top end. Is that normal?
ReplyDeleteThanks again.
It does bring back the top end much like a buffer would. You could also try A500k instead of the A100k pot and try a few different J201 transistors also
ReplyDeleteI did go with the 500K and the 2n5457. I do have some J201's. Would that make a difference?
ReplyDeleteI found that J201's work better, also keep in mind that this circuit was never meant to produce huge boost levels it's very subtle but noticeable, that being said it's a nice amount of bump in volume but most importantly the notes come to life.
ReplyDeleteI will give them a try, Thanks.
ReplyDeleteYes, it does add some "life" to the notes. I was not looking for a huge boost. I have an EP Booster clone and wanted to compare this one to that. The EPB has it's own thing going on, for sure.
Tried out the J201...huge difference! Tamed the highs quite nicely. The pedal is not quite the same as the EPB, but it is much better.
ReplyDeleteMaybe I'm wrong, but in the one with the 18V charge pump, pin 3 and 5 of the IC7660S shouldn't be linked for allowing pin 5 to be grounded too?
ReplyDeleteBuilt the "early version with vol control" EP-3 Preamp with a J201. Nice one indeed - not a huge amount of boost but definitely useable - doesn't seem to alter my clean tone so much either. I was waiting to find a nice boost to box together with another circuit and I think this is the one. Cheers!
ReplyDeletehey people,
ReplyDeleteI would like to build the echoplex with a gain pot. could you please explain me how can I add the pot to the first layout?
thank you
I'd try a 500k pot with vol 2 to ground and vol 1 to where the 100k and 220k resistors meet. adding one extra column to the layout would be a good idea too.
DeleteThis comment has been removed by the author.
ReplyDeleteI've found J201's a bit hard to get hold of so I put together a 2 JFET Preamp made with J112's. I'm not sure how it compares sound wise but it works. Just thought that with J201's only going to get rarer it might be of use. https://postimg.org/image/cszgbtcxp/
ReplyDeleteComments appreciated.
Hi there!
ReplyDeleteWhere it was placed in the EP? at the beginning?
Honestly, anywhere you feel it would sound better. Usually before drive pedals or at the end of your pedal signal chain, just before your amp.
DeleteI built this preamp, although i've used the actual schematic, which differs only so slightly, also i had to use 100k pot with 10k to 68k resistor instead of 500k because i didn't have one at the moment, and this thing is stupidly loud, only at 100k it matches a volume of my rig, transistors i've used are A30K, but all in all at 18v in the end of the chain it sounds awesome, sort of adds things that are missing, substracts things that aren't necessary and glues everything together nicely, but really, you can put it wherever you want, or even build a few and complement various pedals at the same time, also i was surprised as to how it dealt with high gain big muff sound and high gain in general, a really transparent thing. Can't recommend enough.
ReplyDeleteplease Danich: Your schematic published would be appreciated...
DeleteMammoth doesn't have a 3 meg resistor. They do have a 3.9 or 2.2 meg resistor. Is either one useful?
DeleteAnything from 1M and up will be fine in that position.
Delete+m
On the Tillman with Gain Switch, can someone help me with the switch connections? The SPDT switch has 3 terminals, am not sure which 2 to use. Thanks!
ReplyDeletethe lugs are as follows
Delete1
2
3
you only need to use the middle lug (lug 2) and the top (lug 1).
Thanks Zach!
DeleteHi, How can I add a tone control to echoplex, thank !
ReplyDeleteRe: the question of voltage: purists often say the Echoplex preamp must be run at 22-24V to get the "mojo." IvIark's first layout here will work fine at 24V. Just make sure the transistor and caps are rated for it. (My 2N5457s max at 25V both D-S and D-G. J201's are higher, I think.)
ReplyDeleteThe key is the lDSS of the JFET, which should be around 3mA. Aion Electronics has a good explanation included with their Ares Preamp project:
https://aionelectronics.com/project/ares-echoplex-ep3-preamp/
To measure a JFET's lDSS:
http://tagboardeffects.blogspot.com/search?q=JFET+matcher
AND:
http://www.runoffgroove.com/fetzervalve.html
Forgot to mention: here's a handy charge pump that takes 9V and puts out 17V, 25V, and 33V:
Deletehttp://3.bp.blogspot.com/-SQ39S5PKGaY/T55VbDB8WNI/AAAAAAAABYk/NnF-rwLgLno/s1600/Charge+Pump+33V.png
To fine tune to the voltage, just fashion a simple voltage divider. Might be worth boxing up standalone.
Can anyone else verify the "Early version EP3 with volume control"? Off board wiring is sound, and scraped out between Vero tracks but no signal passing through?
ReplyDeleteI should mention I've used an MPF102 and had to sub the 1meg for a 1.2m
ReplyDeleteIn the EP3 echoplex version with volume control, would it be correct to say that the 220k resistor should be connected to ground and the 500k potentiometer should be in parallel with the 220K resistor?
ReplyDeleteThis comment has been removed by the author.
ReplyDeleteWhat kind of diodes are used with the 18V version of the Echoplex?
ReplyDelete1n5817 were used for other charge pumps - that's the way to go?
Thanks for the post checkout the best max volume booster app for android.
ReplyDeleteI don't get it
ReplyDeleteAfter unsuccesfull trying to build the perfboard-version of the Echoplex with volume control, I went to the veroboard.
Unsuccesfull too with the same problem.
I do get sound but no boost at all, it even sounds weaker and thinner than bypassed.
Just checked everything but it seems all fine.
Any idea what voltage I should have on the transistor?
I'm using a 2N5457.
Before the last 2 resistors, 100K and 220K, the signals sounds nice and boosted.
DeleteAny idea what could be wrong?
I'm going to a homemade mini practice amp with a Kemo 3.5W amp module.
This thing has no real preamp so I thought this echoplex would be nice to put in front.
Just throwing this out there, but you’re having a similar issue with the fender Bassman preamp with the same Kemo 3.5W amp. Your problem may be the amp not the preamp boards.
DeleteHehe, who knows.
ReplyDeleteThe gain issue with the bassman was solved actually.
That Kemo amp has a pot on the input, perhaps those 2 resistors combined with the pot gives the problem.
I don't know much about impedances, just guessing around.
If I bypass those 2 resistors separately with a switch, would it do harm to the volume control?
Hi all,
ReplyDeleteWhat would be the best way to make ep3 a little brighter, with more high medium and high?
Probably with a smaller input cap, a simple trick for sure. Replace the 22nF on the left with a 10nF or smaller. This will cut some bass, potentially it could be a treble booster.
DeleteI'm finding the pedal just a bit too bright. Presumably, increasing the input cap value would solve this? Is there a way to add a treble roll off pot into the circuit somewhere? (I can build these vero board circuits fine, but i don't really understand HOW they work).
DeleteJust to be clear. Everything else is fine with it. I don't want more bass or anything. It's just the very high-end treble needs taming.
DeleteIt's the 'Early version EP3 with volume control' by the way.
Deletethe "echoplex preamp" thing cracks me up.. what a freeking scam/sham. the echoplex has a BUFFER between input and output. they took the next stage, which is to drive the record head's bias and isn't actually part of the audio path of the actual echoplex, and used it as a booster stage. echoplex's don't boost. they can't, in fact.
ReplyDeleteall hype. i realize they're popular, but it may as well be a klon lol
Hi all, how would I wire a volume pot to the 18v version of the echoplex circuit?
ReplyDeleteTake the Output wire shown on the layout to lug 3 of a log pot (try any value you have to hand). Volume lug 1 goes to ground and luge 2 is your new output wire back to the switch
DeleteThnx so much. Now for last question people are talking about a gain pot. On the Dunlop ep101 it only has one pot and its a gain pot. Does this work the same as the methods described here. Or is this more of a volume pot linked to the output?
DeleteHi i know this is an old thread, but in the first EP3 circuit without a volume control, is the output at unity gain? If there is a slight boost how much of an increase in dB is it?
ReplyDeleteI've wired the Tillman with a tonemender and I get a little howling. Not too much just a little. Could this be due to the due to the fact that both circuits have the same power source?
ReplyDeleteI also notice that the hum is present even if there is no FET.
ReplyDeleteHow does this compare to the catalinbread epoch boost?
ReplyDeleteQuick question that, how would it differ if I place a Tillman before or after Volume pot of the guitar (between switch and volume pot, or between output jack and volume pot) Or would it make a difference at all?
ReplyDelete