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Thank you for your suggestions...

I had a look at Jacob PCB and it seems to be based around which is what I've built using A.Ziltz's micro buffer schematic.

You're right, the tuner out would not be really isolated, in fact I don't want to use transformers, but the buffer will not let the tuner suck the tone or contaminate signal. Right ?

How you determine that the pedal maximum impedance will be 25k ?

Jacob (JMK) makes a PCB for a buffer-splitter. It's basic but good. And it's tiny.

A buffer/splitter does not "isolate" the tuner out. It just amplifies the split signal sufficiently. An output buffer is unnecessary but not a horrendous idea. The pedal's maximum impedance will be 25K, and that's when it's OFF. Most of the time you're going to be running it between 0 ohms and maybe 10K. That's not enough impedance to worry about. Putting a JFET output buffer would make the impedance ~300 Ohms.

The impedance control can be a DPDT switch to swap the impedance resistors. Jacob notes this in the build doc. Changing them from 10M to 1M would have a big effect on the input impedance. High frequencies are amplified more than low frequencies in pretty much any circuit, so it's not like there was something "wrong" with Thru-tone's buffer. Different guitar pickups may have different impedance requirements.

I'm not sure why you need to make it the "exact" dimensions of the original. There's plenty of room inside a VP.

You could save yourself a lot of trouble, however, my just making yourself a 1590A buffer-splitter box with a tuner out. Put it first in your chain and it'll drive all your pedals, provide a buffer for the VP, keep you from having to drill a quarter inch of aluminum and power your VP, and it can be moved around and used with other boards if you get tired of using the VP. Add a bypass toggle and you are automatically back to your original setup.

Hey guys,
some weeks ago I bought my first volume pedal, a EB VP Jr.
I really like the mechanical build quality, but right after plugging it in my rig, I figured out that this design isn't really useable in every spot of my chain.

I soon discovered that the tuner out (connected in parallel to the input) can suck tone depending on the tuner used and the signal chain, in fact using my polytune for silent tuning was pretty much impossible.

After a quick search on the web I found that some companies (ie. JHS and Thru-tone) offer MODS for this kind of volume pedal.

It seems JHS uses their "Buffered Splitter" circuit to buffer the pedal and split the signal for the tuner out, but I don't know anything about the circuit they use.

Thru-tone does pretty much the same thing adding a impedance control to 'manage' the top end (probably their buffer add too much hi-end ?)

I tried to search the web, but I didn't found much information about active designs in volume pedals.
I have some skills with Eagle and I can etch my pcbs to test some prototypes, but I would like to have your input and do something useful for other DIYers like me.

The goals:
- Making a direct replacement PCB with the same dimensions as the original
- Add a buffered splitter at the input to "isolate" the tuner output
- Add a buffer at the output after the volume pot (not sure if it is necessary)
- Make it totally bypassable-back to stock conditions (just in case)

Optionals:
- Leds on the inside (ala JHS)
- Add a input impedance control (not sure if it could be a feature)

Block diagram:

             INPUT -> BUFFERED SPLITTER -> VOLUME POT -> OUTPUT BUFFER -> OUTPUT
                                                       -> TUNER OUT


Now, I would like to ask your help since I don't know what kind of buffer could be the best for this application. I'm experimenting with some of Jack Orman's designs and I've build a couple of his circuits to test them.

I've also tested Mr.Ziltz splitter (which I really like) and seems to be a really transparent option but I would really like to know if someone else is interested in this and I would like to get your input.

Thanks for your help,
and sorry for my english guys...

Jimmy.... THAT is pure inspiration.

I dig the rust driver, do you think it is going to fit in a 1590a ?
Great tone, great playing, really !
Thank you !

Thank you for the kind words guys !

Hey guys, this time it's time for my latest build.
The firebomb 2-in-1.
This is my first booster, I never used nor owned one before, so I didn't really know what to expect apart from a device meant to add some gain to my guitar signal.

But to my surprise that was something more than just some gain I really like the way this pedal colors the sound, so I decided to make a super quick demo.

Since it really didn't make sense to drive the DI input of my soundcard, I placed the firebomb before the krankosaurus I just built to have "something to drive".

The recording chain is the following:
Guitar -> firebomb -> krankosaurus (set as mild overdrive) -> t.c.electronic konnekt 8 DI input -> Overloud TH2 (blackface '65 amp and cab set clean with just a bit of break-up, mic'ed with a SM57, you'll able to hear the clean tone at the beginning)

This time it is hosted on soundcloud.
http://soundcloud.com/neeeeeeeeno/firebomb-2-in-1

The "effect" might sound a bit "subtle" (especially the comparison between Boost A and Boost B, but it is not at least IMHO, it really worth having one, so thank you one more time for a great project madbean.

P.S.: sorry for my english...

Thank you guys, thank you so much for the kind words.
I'm loving this pedal too, even if I have to admit that with the stock cap value it sounded less interesting to me, but now it sounds more "balanced" less muddy and less fuzzy, especially in the low registers.

jubal81, thank you.
Yes, the riff came up while playing with the pedal after the mod, so I decided to record it... and make the demo.

Hi guys, I just finished (not really) building a krankosaurus (thank you Brian) and since I had the pcb still lying on the desk (did the input cap mod from 100n -> 22n as suggested by Pauloman80... thank you!) I wanted to make a small sample.

The recording chain is a bit unusual, I know, so take this as a grain of salt.
Guitar -> krankosaurus -> t.c.electronic konnekt 8 DI input -> Overloud TH2 (blackface '65 amp and cab set clean with just a bit of break-up, mic'ed with a SM57, you'll able to hear the clean tone at the beginning)

Guitars had really minor eq and a tiny bit of compression to sound "in context" with the drums.
http://soundcloud.com/neeeeeeeeno/krankosaurus-bor-22n-input-cap

Before the mod the pedal sounded a bit too bassy and muddy, the 22n cap on the input cleans up the low end. Feel free to experiment with different values 33,47n,...

The original mod thread:
http://www.madbeanpedals.com/forum/index.php?topic=359.0

Cheers
Neeno

nzCdog that guitar sound is amazing ! 
Would you like to share the details of the recording chain ?
Amp model, cabinet, microphone, preamp, etc

Thank you in advance and congratulation for this build... it sounds and look so good !

Hi guys !
My first post here... long time Diy'er...
The Deadringer is my 7th stompbox build and I really love it.
I used madbean's single sided PCB layout and etched it myself, followed the actual BOM and the wiring diagram, which I can confirm is perfectly working.

Actually with the 1N914 in parallel with a 1N4005 the "Standard" mode (or silicon) is lower in volume compared to the "Mosfet" mode.

I think this is due to the symmetrical vs. asymmetrical clipping happening. (I did a similar mod on my TS)
Using two 1n4005 in series to replace the 1n914 makes the "Standard" and the "Mosfet" mode equal in volume, exactly like the current Fulldrive 2.

Thank you for this thread Madbean, and for all the great projects !

Neeno

As promised, here is fix for ver.1 of the Deadringer. When I constructed the original schematic, I inadvertently reversed the order of some things, and had at least one portion routed incorrectly. Additionally, there were three incorrect values listed. My apologies for these errors. I was too hasty in releasing it, and while I thought I had worked it out correctly (I did prototype the build, of course) it appears I wasn't paying enough attention.

The value corrections are as follows:

C9 = 10n (orig. 1n)
C4 = 51pF (orig. 100pF)
R15  = 150k (orig. 510k)

Of these three value changes, C9 is the most critical. If you have a ver.1 board, you can probably get away with only changing this value. But, you can change all three, too, if you want to take the time.

Following is a diagram that I believe corrects the wiring situation. My test results with the version 1 build seem to confirm this. The Flat Mids mode is subtle, however this is due to having the incorrect value for C9 (it shold be 10n, not 1n) on my build. When placing another higher valued cap along with C9, the change was much more pronounced.

A brief explanation of how all these clipping choices work: the mos/sil switch (SPDT) does exactly as it indicates. It changes between the Mosfet and Silicon diode clipping in the feedback loop of the opamp. The top position of the 3-way DPDT lets you select compression cut, flat mids and vintage mode. In CC mode, the diodes are actually disconnected, meaning that clipping comes directly via the opamp - not the diodes. This is a much harsher type of clipping, although it can sound very open when the gain is dialed back.

In FM mode, C9 and R13 are placed in parallel with the tone control, thereby altering the frequency roll-off point. It essentially serves to counteract the tone control to make it less severe. Finally, in VIN mode, you have the traditional clipping of a gerenic TS: diode clipping, and the regular active first order tone control.

The Boost mode simply puts a 1M variable resistor in series with the drive control, thereby increasing the overall gain and 'scorching' the diodes a bit more. It has the most impact when the drive control is around half-way or less - this is where you will find the biggest difference in the added gain. In this sense, it's not a boost at all, but rather a "more" option.

On the wiring diagram, you will need to connect the S1, S2 and S4 pads to an On-On-On dpdt (available from smallbear) and run one additional wire from the DPDT to the 3PDT used for the 'boost' option. This should correct the previous wiring/routing errors. S3 should not be connected to anything.

One additional note: looking at a few pics of the insides of the latest FD-2 version, I noticed there is a small change with the clipping setup. It looks like Fuller altered the back-to-back 1N4005/1n914 diodes. The newest change appears to be swapping the 1n914 for two 1n4005 in series. So, following the Deadringer schematic, you would leave D1 the same, but in place of D2 you would solder two more 1n4005's in series. This preserves the asymmetrical type clipping of the previous version, but increases the overall forward voltage with the two new diodes in series. Hence, his description of a more 'open' sound. So, this is technically an additional correction to both ver.1 AND ver.2 of the Deadringer.

Sorry for the long winded post - I thought some of this additional info might shed some light on the design of the pedal. Diagram is attached below.