DiY Buffer

Dave Hepworth · Post by **Dave Hepworth** » 2 Jun 2016 8:46 am

Hi Craig,
Thankyou for the complement.Blue is my favourite colour( however my steel is black!! Lol)
I pride myself in how I mounted the Jack.If you look at the inside it is strengthened by a piece of copper cut from sheeting,drilled a jack hole then I covered the copper on one side with solder.After setting I positioned over the Jack hole on tin and remelted the solder with a butane torch and allowed to set in position.Hay ho the Jack area is now strengthened .A large blue sprayed washer is seen on outside of tin to give more purchase .

Dave Hepworth · Post by **Dave Hepworth** » 2 Jun 2016 8:50 am

Hi Again Craig,
If I lighten the colour up on tin it won't be to my liking anymore and could therefore sound different !

Craig Baker · Post by **Craig Baker** » 2 Jun 2016 9:28 am

Dave,
I did notice your washer. . . great idea to stiffen the can.

As I said, I can't explain the relationship of the bright blue color to the sound. I think it's along the line of black steels sounding better. LOL.

All the best,
Craig

Dave Hepworth · Post by **Dave Hepworth** » 2 Jun 2016 9:52 am

Hi again Craig and George,
Latest update......got the new caps this morning ....10 minutes on workbench and it was reconfigured ,also to include an " idiot" diode on + side of battery to earth .See photo.
Just plugged it into my Mullen RP. All I can say is WOW ! The guitar has suddenly come even more alive than I thought possible.String separation is amazing with lots of fine detail,even the low strings growl in an amazing fashion.Harmonics are picked out so well and easily too.I will use this over my first DIY buffer earlier in thread.
Thanks all you guys for the theoretical help in my quest to build this buffer.I just need a better way of securing battery inside.I am using Velcro at moment .Due to space constraints a big battery holder like my first attempt would not be an option.Any thoughts.
Regards Dave.

Brad Sarno · Post by **Brad Sarno** » 2 Jun 2016 9:55 am

Steven Paris wrote:...Some have posted that the outputs of some pedal steel guitars "overload" the front end of old Fender amps---is this true? Anybody done any research on this?

A typically hot PSG pickup can very easily overdrive the first input-tube stage on a Fender amp when plugged directly into the amp without a volume pedal. But, most pedal steelers play well below 50% on the volume pedal travel and this essentially reduces the signal voltage at the amp's input to about 1/10th the original voltage. In that case, it's pretty hard to overdrive a Fender input. I find that the people who complain about that tend to play way to hot on the volume pedal.

John Hughey used to say he played at around 15% of the volume pedal travel and that left him 85% of available volume pedal sustain.

If I play steel into a Fender amp, I can most definitely begin to hear the ghost harmonics if the volume pedal is high, above 50% travel. But since that kind of volume pedal level is only reserved for a soft and decaying note, overdrive never really comes into play.

B

Georg Sørtun · Post by **Georg Sørtun** » 2 Jun 2016 1:51 pm

Dave, it "sounds" like you have built yourself a buffer with characteristics that suit your gear. Great!

As for holding the battery ... my old Goodrich buffer has small thin-metal clips - about half the length of the battery - to hold the batteries in place.
For one looking like yours a "springy" angle-piece made out of a thin metal-sheet - maybe the same as your box is made of - to keep the battery pushed against the rounded side of the box where it is placed on the picture, might work. Glue the sheet to the bottom of the box under the battery and let a tall, wide, lip push against the side of the battery, and it should stay in place there.

Craig Baker · Post by **Craig Baker** » 2 Jun 2016 3:11 pm

Dave,
You might try double faced tape. 3M makes some that can support many pounds and would easily stabilize your battery.

By the way, if you put a lithium battery in there, it might last for years. (I sure wish you'd work on that color.) LOL

Craig

Dave Hepworth · Post by **Dave Hepworth** » 3 Jun 2016 1:30 am

Thank you once again Craig and George,
Will try both battery ideas.On a different tack would it be possible to switch on / off the resistor and cap cap tone boost mod you drew George.If so where would you switch it on diagram and would it need an anti pop addition ....if so what and where.Sorry to keep picking your brains but I am really now into these things for my set up.Craig I will work on another shade of blue lol

Georg Sørtun · Post by **Georg Sørtun** » 3 Jun 2016 4:09 am

Dave, you can switch on/off the high-boost by inserting a switch between the 120pF cap and GND. You will then still get a very slight boost over the entire frequency range, but no extra high-lift.

("Pop" sounds are always caused by the charging/discharging of capacitors when units - or circuit parts - are plugged or switched in/out and when they are powered up/down. Sometimes one will also experience that capacitors continue to charge themselves up or down when circuits are on, because of faults/leaks in caps and/or insulator-leaks and stray fields in the caps' surroundings.
Note: all capacitors leak DC, although good new caps will leak very little and very slowly.)

"Anti-pop" solutions ... if/when deemed necessary.
Usually better to add them early on, then to wait for the "popping" sounds to become a real nuisance and the charging/discharging of caps to cause failing pots.

- a resistor in the 220K to 470K range between output and GND (after caps - at the output Jack), will keep the electrolytic cap's negative side at GND-level and save VP-pot or whatever comes after your buffer from having to discharge it.

- you can also put a 2M2 (2.2 MegaOhm) resistor between input and GND before circuit to keep input side of that small capacitor at GND-level when it isn't connected to the PU.

- if the "hi-boost" on/off switch causes disturbing "pops" or "crackling" noise when switching, a 2M2 resistor over the switch will DC-GND the 100pF capacitor when switch is open.

Craig Baker · Post by **Craig Baker** » 3 Jun 2016 4:35 am

You might try just put a shorting switch across the 27pf cap, thus taking the circuit back to a simple buffer. With no voltage going through the circuit, I wouldn't expect a noticeable "pop". Keep in mind that the offending voltage may either be leaking dc or audio signal. (switching while the music is being played.) Let us know your results Dave.

Craig

Georg Sørtun · Post by **Georg Sørtun** » 3 Jun 2016 5:05 am

Craig Baker wrote:You might try just put a shorting switch across the 27pf cap, thus taking the circuit back to a simple buffer.

Recommended solution.

(Craig, you make it too easy ... short-circuiting my hi-boost

)

ajm · Post by **ajm** » 3 Jun 2016 6:48 am

Battery restraint: You could try a piece of (non-conductive) foam rubber in the circular shape of the case. If it's the right thickness, when you put the cover on it should form itself around the innards and provide enough "fill" to keep things from moving around.

Craig Baker · Post by **Craig Baker** » 3 Jun 2016 8:23 am

ajm,
Good call, can't get much easier than that !

Georg,
With a well-designed buffer, do you really need a high boost? Just the advantage of low impedance should bring back the high frequencies that (before using a buffer) were previously being attenuated.

Many of my customers have told me they can reduce the presence and treble controls and yet experience pleasing overtones they've never heard before.

Craig

Georg Sørtun · Post by **Georg Sørtun** » 3 Jun 2016 9:22 am

Craig,
getting a "crispier sound" was a request in the thread, and boosting the harmonic range in the buffer works at least as well to achieve that as raising them in the amp-eq will do.
Without going through the entire sound-chain in each case, I cannot say if there's a real "need" for high-boost in the buffer, or not.

The higher input impedance of a good buffer does get out all the PU can deliver up high, but players still like to "tune their tone" with the tone controls on their amps so obviously the "optimal load on and sound out of" the PU isn't enough.
The reason - apart from "individual and very personal preferences" - is probably that neither the buffered PU, nor any of the following stages (mainly amps and speakers/cabs), are anywhere near "linear" when run "flat". If they were, then all PUs should at least produce the same sound when mounted identically on a PSG and run through the same sound-chain with no adjustments, and we all know that they do not - far from it.

For myself: as I prefer to bypass all pre/eq stages in amps and only use the power stage - reducing the sound-chain to a minimum, having a little bit of "tone-trim" in the buffer-stage suits me fine.

Usually I do add a little "harmonic range boost" to "get my sound", but I have observed that my PSGs - with me playing - still tends to sound a little less "crispy" than what comes out when my fellow players play their rigs. Seems to indicate that I need less high-boost than others, but I'm not sure and don't want to overanalyze these observations.

Dave Hepworth · Post by **Dave Hepworth** » 3 Jun 2016 9:24 am

Hi again George and Craig,
Tried the 27 cap shorting with a piece of wire ,result no change.I may try the 120 cap as you say George ,or I may just leave alone .The sound the thro a peavey bandit 100 transtube is amazingly clear and bright.Thro my Vegas 400 it is still amazingly very clear but the speaker imparts a certain mellowness ,plus the EQ is differently voiced too.All very subjective ,but certainly a vast improvement over a non buffered signal chain.I am certainly very pleased with my efforts and time spent over this.Now let's see which is best battery holding set up ....thank you ajm for the foam tip too ,could be a winner !
Regards again Dave.
.

Georg Sørtun · Post by **Georg Sørtun** » 4 Jun 2016 1:05 am

Dave Hepworth wrote:Hi again George and Craig,
Tried the 27 cap shorting with a piece of wire ,result no change.

I cannot explain that "no change" result ... the OpAmp should change to unity gain with flat frequency curve when you do that. Are you sure you shorted between the IC's output and its negative input?

Dave Hepworth · Post by **Dave Hepworth** » 4 Jun 2016 4:11 am

Hi George,
Maybe I went wrong .I just put a wire between the 27 cap .I also tried disconnecting and reconnecting the 120 cap to earth and no change. What PIN numbers would you short on the op amp.
Regardless the buffer is defo. more top end than my first buffer with standard non negative feedback.
I have looked at diagram you gave and mine seems wired as per.
Regards Dave

Dave Hepworth · Post by **Dave Hepworth** » 4 Jun 2016 4:16 am

Looking at circuit I should connect 2 to 6 with none of the resistor / cap network ? Would you break at 2 onto a dpdt switch one thro the network and the other pole a wire straight to 6 ?
Dave.

Georg Sørtun · Post by **Georg Sørtun** » 4 Jun 2016 5:08 am

1: To short-circuit the "hi-boost" (via a switch) to bring the circuit back to unity gain - as Craig suggested, connect the two points marked "A" in the drawing above via a switch.
- Open switch = "high-boost" ON / closed switch = "high-boost" OFF.

2: To disconnect the "hi-boost" (via a switch) - as I suggested, disconnect the cap from GND at point marked "B" in the drawing and re-connect that cap to GND via a switch.
- Open switch = "high-boost" OFF / closed switch = "high-boost" ON.

If all else in your build is correct, then either of these two solutions will work and let you switch the "hi-boost" on and off. No need, or point in, using both solutions, as they are in practical terms achieving the same thing.

Dave Hepworth · Post by **Dave Hepworth** » 4 Jun 2016 9:54 am

Hi again George,
The saga continues.I think the electronic shop gave me the wrong value resistors.The colours are Brown ,2 blacks ,green and purple .I think it should be orange white yellow gold for 390 K .Would this thro the HF network out?
The 100K seems correct.

Georg Sørtun · Post by **Georg Sørtun** » 4 Jun 2016 10:44 am

Yes ... orange white yellow gold = 390Kohm.

The 5-band resistor code you say you have now actually confuses me a bit - "100 multiplied with something", but the value is clearly too low for those two resistors and will in effect short out the hi-boost circuit = there is no high-boost now.

Anyway, you can use this calculator to check color codes, and if in doubt about those codes an ohm-meter is always nice to have.

Dave Hepworth · Post by **Dave Hepworth** » 4 Jun 2016 11:48 am

Hi George,
Looks like the shop have given me the wrong values again !.They may have got their stock mixed up or something.The girl behind the counter only goes on product codes which are in designated bins by the look of things.I will take a meter with me and start the HF loop again.
I will report back next week. If that is ok .Hope I am not pestering too much.
Regards Dave.

Craig Baker · Post by **Craig Baker** » 4 Jun 2016 12:39 pm

Georg, Dave. . .
Might be my misunderstanding, but from what Dave stated, With that green band in the mix, I get 10 megohms @ 1% tolerance.
A big departure from the 390 K. (Dave, your 390 K colors are correct.)

Craig

Craig Baker · Post by **Craig Baker** » 4 Jun 2016 12:42 pm

Here's a link to handy resistor color calculator. . .

http://www.hobby-hour.com/electronics/r ... ulator.php

Craig

Georg Sørtun · Post by **Georg Sørtun** » 4 Jun 2016 1:32 pm

Craig, I thought so too at first, but if there are now two 10Mohm resistors in series in the filter and those correct values to GND, there should at least be a change in behavior (sound) when they're shorted. Think we have to give Dave time to go over and check all values.