Echoplex Pre-amp Pedal Clone Project

[harddriver]

As I owned an actual EP3 echoplex it's not a myth on the effects of the preamp circuit on guitar tone. Zeppelin and EVH and many others...

I still use my Clinch and CHase Secret preamp still.... I think you will be pleased when you are done.

Yeah, I have had the Badgerplex AC for some time, and it's one of those effects you just leave on all the time.

Not really a boost, just does some difficult-to-describe colorization of the tone.

I want to run two in series the way Jimmy Page and EVH did, to see what that sounds like.

Been there done that with my EP-3 and I used to have two Clinch EP-PRE"S for that very reason. It's kinda cool, not the absolute secret to VH1 but it is an itch that I had to scratch just for my own VH1 curiousity.

[PLX]

completed circuit board:

[PLX]

test fit of all sub sections:

[PLX]

hook-up wiring, final assembly:

[RockyStar]

Nice!

[PLX]

charge pump & transistors installed. Completed project, gutshot, & faceplate.

[PLX]

project update:

Started using this effect in my signal chain and it's really great at creating a core tone !

Noticed the red LED power indicator failed, which was sort of odd since there's no moving parts or filaments to burn out. Perhaps over-current (?) Replaced with a similar type, but blue.

I'm running this pedal with a 12V power supply, which is then doubled to 24V by the internal charge pump.




Here's some interesting conversations I had with Peter Clinch several years ago about this circuit, and the history of the whole EchoPlex pre-amp in a stomp-box thing..

"Hi, I enjoy your quick sense of humour in the pub.

I've been wondering if maybe you believe that Badgerplex was the first EP-3 preamp in a pedal.

I don't want to be involved in an off topic he-said-she-said thing on the thread

I was the first to design a pedal version of the preamp, in 2007. I went into production in 2008, well before Badgerplex existed.

A guy bought an EP-PRE early in 2008. He liked it so much that he wanted a second one. I had a big waiting list, so I told him that I would email him when a pedal became available. When I sent the email, I didn't receive a reply and thought he had changed his mind as folks often do.

Apparently he didn't receive the email, which can happen with server spam filters etc. A little later, posts began to appear on most guitar forums, bagging the EP-PRE, saying it was cheaply made etc. Some time later, the Badgerplex appeared.

Eventually, someone told me that the guy believed that I had purposely ignored his request and decided to teach me a lesson. He had his pedal traced and commissioned someone (Robert?) to make a copy that would put me out of business.

They used a MAX1044 charge pump and had problems with power supply noise. The mains powered Badgerplex appeared after I made a tongue-in-cheek post that the only way of making a "True" EP-3 preamp would be to use mains power.

If you'd like to try an EP-PRE, I can send one to you. If you like it, you can buy it at wholesale price. If you don't like it, you can send it on to someone else. Since 2012, the EP-PRE has a second JFET stage that I designed to reduce the output impedance without any change to the special tone of the preamp.

Cheers,

Peter."


So, a little back story here.. The characters he's referring to are Robert of Badgerplex effects, who coincidentally lived a few miles from me, back in those days. The "guy who wanted a second pedal" is Don Barzini on the old MetroAmp forum.

This whole thing blew up in a thread and ensuing hilarity created one of those legendary threads you don't see anymore because of the nanny-state moderation being done nowadays.

[PLX]

continuing conversations with Peter Clinch concerning the EchoPlex pre-amp circuit:

"I don't believe the (TIS-58 transistor) hype either.

I'm not so sure that there is anything special about the TIS58, except that it has a set of characteristics that just happen to work well with the component values that were chosen for the EP-3 preamp. I get the feeling that Mike Battle and his team were trying to directly convert tube circuitry to solid state with as few circuit changes as possible.

I tried hard to find some TIS58s for testing, but in 2007, there were none listed at any of the obsolete component suppliers. They began to appear a couple of years later, but I had already settled on a current production substitute. I had two very sketchy sets of data for the TIS58, but none of the graphs that could have made it easy to find a substitute. I ended up finding a few JFET types with vaguely similar characteristics, and tried them in the exact preamp circuit (component values and supply voltage) to see how well they biased. The best was 2N5484, so this is what I used in the prototype that surprised me with sound that I hadn't expected.

When I began selling EP-PREs, I tested all the JFETs that I bought, to ensure that they would bias properly in the EP-3 circuit, and rejected any that didn't meet bias requirements. I've since found that the SMD version (MMBF5484) has much closer specification tolerances, although this is not documented in data sheets. I test bias in all completed PCBs, and find that maybe one in fifty needs the JFET replaced due to incorrect bias. I have a tweezer soldering iron, and it's easier to replace a JFET now and then than to test hundreds of them before assembly.

So often, I've heard that some EP-3s sound better than others. This is probably due to parameter spread in the TIS58s from back then.

By the way, someone lent me a Secret Preamp. It uses a 2N5457 JFET. I double blind tested it against a number of new EP-PREs and could identify the SP every time. I checked the bias on the SP and it was way off, even though they use "exactly 22V" (in reality 23.2V).

Dunlop/MXR use a Mosfet, LND150, instead of a JFET in their EP-101. It doesn't sound anything like an EP-3 preamp.

I'll leave it at that for now.

Peter."


A little more history: Robert at Badger Effects had managed to source a supply of TIS-58 transistors. At that time, I lived right behind the old Texas Instruments manufacturing plant off highway 290 in Cypress, Tx. You could find amazing electronic things in the dumpsters out back in the parking lot after they closed that facility and before Compaq Computer bought the site.


Peter Clinch conversation dated Sep 21, 2018:

"The original JFET, (TIS58) is unavailable in production quantities, and the parameter spread in TIS58s required a 22V supply in order to bias reasonably well. Even then, no two EP-3 preamps sounded the same. Some "builders" are using a 2N5457, which is one of the first that I rejected as being unsuitable for use in an EP-3 preamp. A 2N5457 will require at least 22V supply, and even then, it will not bias well in the EP-3 preamp circuit without changing some other component values. The result is a muddy tone. I found a current production JFET with a relatively narrow parameter spread, that will bias properly with a supply of 17.6V. We were testing all our JFETs before assembly, but have found that it is better to assemble PCBs and then test. If a PCB fails the test due to out of spec bias, we then replace the JFET in that PCB, maybe about one in fifty PCBs.

The 22V thing is just marketing BS.

My main goal is to manufacture a consistent product, not a hit or miss.

Our preamp circuit is identical to the EP-3 circuit, and we use a 500K volume pot, just like the Ëcho Volume pot in the EP-3. This creates a high output impedance, so in 2011 I developed a second JFET stage that is totally transparent and lowers the output impedance without changing the classic tone. At least one pedal builder has taken a short cut by reducing the value of the pot, which reduces the output impedance somewhat at the expense of authentic tone."

[harddriver]

Peter Clinch is a good guy! I have nothing but good things to say about the man.

I was the first person in the US to receive Peter Clinch's production EP-PRE. I think it was 2008 or so, there was a whole thread on Metro that I made about it. I still have it and use it regularly... it's a great pedal.

Hey PLX was JFETs are you running in your EP PRE pedals?

[PLX]

Peter Clinch is a good guy! I have nothing but good things to say about the man.

I was the first person in the US to receive Peter Clinch's production EP-PRE. I think it was 2008 or so, there was a whole thread on Metro that I made about it. I still have it and use it regularly... it's a great pedal.

Hey PLX was JFETs are you running in your EP PRE pedals?

Yeah, I appreciated the technical discussion I had with Clinch. I learned a lot about the EP-pre circuit design.

The thread on Metro forum that went sideways wasn't the one you started, it was the one Stuntdouble (Ben Wise) started that went ballistic. The former moderators over there deleted the posts from the thread where Peter Clinch created a sock-puppet account (purpleplexi) and started name-calling and arguing. They also scrubbed out posts by Don Barzini and others who were arguing back with Clinch and his sock-puppet.

http://forum.metropoulos.net/viewtopic.php?t=35577


Right now I have the Badgerplex AC version (stamped with manufacture date: May 28, 2011), and the clone I made of the Clinch EP3-pre in this build thread.

The Badgerplex has a single Texas Instruments TIS-58.. since it has no second JFET output stage.

The clone has a 2N5484 for Q1, and a 2N5485 for Q2.. just like the ClinchFX EP3-pre.

They sound very different. The Badgerplex is subtle, but you miss it when it's off. There's very little boost, but it has a sweet sounding phase response added into the original input signal.

The clone has a very noticeable gain boost, especially with the "FAT" switch in the 3 position.