[78] Modding the EH LPB-1 Nano

Date: March 9th, 2008 | Comments : [18] | Categories: DIY.

EH LPB-1 Nano

The LPB-1 is a good value for the money, but there are two ferrite beads and two 100pF capacitors left in the signal path even when the circuit is bypassed. The additional capacitance could create an upper frequency loss when driven by a high impedance source like guitar pickups.

This mod removes those components, which were not on the 1960s original, and converts the pedal to the more typically understood definition of true bypass.

Remove C4 and C5 – not needed. Replace FB1 and FB2 with jumper wires. Done.

It will then be 100% true bypass with nothing but wire between the input and output jacks when bypassed.

These instructions are for the “Rev. B” circuit board.


18 Responses to “Modding the EH LPB-1 Nano”

[366] Andrew K. Says: 5:24 pm, March 10th, 2008

Wow, they use a 3PDT but it’s not true bypass? Seems kinda silly. Thanks for the tip Jack, but I’m going to stick to better boosters like your mini and mosfet boosts 😉

[372] admin Says: 9:34 am, March 16th, 2008

I first thought this was an error in layout of the pedal’s pcb, but I have now seen gut shots of a couple of the other nano series and they have the same bypass arrangement.

If you had 4 of these pedals in series, there would be 800pF of extra capacitance left across the signal path, along with the series inductance of 8 ferrites. IMHO, that is a recipe for tone sucking.

It is easy for EH to fix and it would be good if they took a look at it. 🙂

[375] Dr. Weezil Says: 11:42 am, March 18th, 2008

I’m sorry but as a longtime reader of the site, FOH engineer, guitar tech, and electronics builder, I must strongly disagree with and advise against this mod.

The LPB is suceptable to noise and interference in its original form and it has no outside protection save the enclosure shielding. It sounds like EH has improved the design to combat this. Similar ferrite bead capacitor networks are used in many pro audio devices as an EMI/RFI filter. Even if you assume the ferrite beads are rated at most 100R each – although my guess is they are much less – plus the 800pF of accumulated capacitance for the 4 assumed EH pedals, the cutoff frequency is almost 500k! What is the point? No interference with guitar frequency reponse, no “tone sucking.”

Once again, the “true-bypass” cult cuts off its nose to spite its face.

A better option to combat loading is to build a buffer hardwired to the input before the LPB circuit so that the guitar always sees a high impedance no matter if the booster is switched in or out.

[377] admin Says: 6:31 pm, March 18th, 2008

The signal line is being driven by a guitar pickup, which is a large inductor, 2H to 7H or more. It’s not just the small ferrite beads that are in series with the additional capacitance. The cutoff frequency will fall into the audio range, i.e. tone sucking.

Also, if a manufacturer makes a claim of “true bypass” then I believe that the pedal should adhere to that claim and not be “almost true bypass”.

Lastly, the ferrites and capacitors could still be used on the pedal to block the RF if the design has placed them on the input of the circuit board instead of before the footswitch. In this case, the circuit would be true bypass when the switch was toggled off but the EMI/RF protection would come into play when LPB was turned on.

This is the proper way to design it and doesn’t cause potential problems with other pedals, cables, amps, etc.

I have long been a proponent of both true bypass and buffers as the application requires, and any suggestion otherwise is just nonsense.

[781] Best Clean/Transparent Boost Pedal - My Les Paul Forums Says: 3:25 pm, September 2nd, 2009

[…] This is a new LPB, not one from the past. Positive. this can explain it better than I could. AMZ-FX Guitar Effects Blog Blog Archive Modding the EH LPB-1 Nano […]

[789] Razvan Says: 5:29 am, September 13th, 2009

How sure are you of this mod? The ferrite resistors measure 0.2 ohm each….. And if u remove the two 100pf caps, it tends to be much treblier and annoying when you boost things with it

[790] admin Says: 5:45 pm, September 13th, 2009

The original LPB-1 did not have those components, so I’m sure of the mod.

regards, Jack

[867] Sledge Meatra Says: 12:54 am, November 20th, 2009

I have this pedal and find that it is too over bearing. It is now in a zip lock bag in my “What should I do with this box”. It way overdrives everything and even causes noise. Why bother?

[2355] alex Says: 10:47 am, October 3rd, 2011

I have heard about another modification consists in changing the values of C1 and C2 (originally 0.022uF) to 0.047uF. It is said that this creates a more beefier sound and also retains definition.

You say that removing C4 and C5 and Replace FB1 and FB2 with jumper wires could also compensate some of the upper frequency loss.
I’d like to know if i have to change the values of C1 and C2 when combining this two modification

[2358] alex Says: 6:12 pm, October 4th, 2011

Ok first I did mod # 1 removing C4 and C5 and Replace FB1 and FB2 with jumper wires. And felt it’s got more definition when I turn the boost on.
I spend a day with the first mod, then the day after I tried step #2: I change C1 & C2 from the original caps to 0.047uf. I was expecting something like I have to use another values like 0.033 caps but when I turn the booster with the 0.047uf caps everything is much better now. I don’t feel like trying the 0.033uf caps. I hope this info to be useful.

[2642] Brad Says: 9:42 pm, February 13th, 2012

Thanks for this info! I’m going to do the mod to my LPB1. I also have a Small Stone Nano, does it have the same problem? If so, does it have the same fix? Thank you very much.

[2881] Jk Says: 12:11 am, May 10th, 2012

This mod really does wonders! Recommended!

[3809] Jan Says: 10:03 am, March 13th, 2013

I just tried it and I have to say it works perfectly! Many thanks =)

[7735] TLpedals Says: 6:15 am, April 18th, 2014

The .047’s work great for me too!

[116067] Soupbone Says: 3:28 am, August 3rd, 2014

Hi Jack.I was reading this page,and had a question about a couple of people that commented about changing the values of C1&C2.They said they changed out C1-C2 (.022uf) to a .047uf.I have a LPB-1(EC-D12.Rev.B) C1-C2 on my board are both 0.1uf!So,I’m a little confused.What is this .047uf changes doing?Thanks Jack,-soupbone

[120436] admin Says: 7:19 am, August 7th, 2014

The 0.047uF as the input cap to the base of Q1 will let all of the low guitar frequencies come through. Same with the 0.1uF.

If you have a 0.022uF on the input, some of the low end will be rolled off.

Usually the value is 0.1uF in the LPB but I don’t have the notes in front of me to say what they were on this version.

regards, Jack

[121253] Soupbone Says: 10:30 pm, August 7th, 2014

Great.Thanks Jack!Here’s a parts list of my PCB:R1-2.2M,R2-430k,R3-43k,R4-10k,R5-390,R6-100k,R7-10k.C1-0.1uf(p.f.),C2-0.1uf(p.f.),C3-47uf/16v(e.l.),C4-100pf(c.r.),C5-100pf(c.r.),C6-100pf(c.r.),C7-0.1uf(p.f.).D1-1N4001,Q1-BC5508.That’s just the main parts on my board.(minus the ferrite beads)Just in case someone needed a parts listing.

[134571] Soupbone Says: 2:02 am, August 19th, 2014

I forgot to mention the abbreviations for the parts listing;PF=Polyester Film,EL=Electrolytic,CR=Ceramic


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