Bogner La Grange

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Re: Bogner La Grange

Postby maoriente » 03 Feb 2017, 07:17

Frank_NH, question:

Any idea how much gain is eaten up in the presence section, if at all?

With the gain switch set at highest, source resistance to ground for the gain switch stage is about 97R.

Looking at the spreadsheet provided (thank you!) I think that indicates with an 18v supply, that stage would have a gain of 37, then passes through the presence "filter" and then if using a 510R source resistor in the next stage, followed by a 330R source resistor in the next stage, the signal would then be increased by an additional gain of about 120 ( 9 x 13.5).

And if all that's true, [gain 37 > presence filter > gain 120] how could it not be squealing :0)
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Re: Bogner La Grange

Postby Frank_NH » 03 Feb 2017, 15:23

I'm not sure how much signal is lost in the presence section, but if the current La Grange schematic is to be believed, this section is nothing more than the Box of Rock (see below). Note how the B.O.R. also has two gain stages in a row, followed by the tone stack and output. Also notice that the boost function is placed at the end. I've built a version of the B.O.R. on vero so I know it works well. With the La Grange, you essentially have all of this boost/gain/tone shaping/clipping being fed into a B.O.R., so no surprise this becomes over the top gainy and subject to feedback/squealing. Thus, it's likely there are still some issues with the current La Grange schematic.

Image
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Re: Bogner La Grange

Postby maoriente » 04 Feb 2017, 03:56

Yeah, and I'm not so sure it even sounds like a plexi as it stands.

I boxed it up, maybe the squealing is a bit better.

The high gain switch is a bit over the top for me, I still need to check the high gain setting with lower gain knob settings and/or other clipping positions. Maybe there is some use for it, but way to much gain with the gain knob mid way.

I also need to pay attention to the actual tone, so far it's been all about eliminating the squeal, oh, and it still squeals fairly easily in the high gain mode. But still, the 5k value seems to give the most flexibility with the gain switch and gain control.

With a 50k gain pot, and 5k source resister (rather than 53R), the low and mid gain settings seemed ok, with more than enough gain/distortion.

Check out the last 30 seconds of this video, sounds familiar... https://www.youtube.com/watch?v=ktqxk3nikz4
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Re: Bogner La Grange

Postby maoriente » 05 Feb 2017, 16:07

I just found this video this morning.

https://www.youtube.com/watch?v=aJrzs4lyfmE

So it seems the high gain flabbiness and squeal are built in to the original pedal after all.

The high gain mode demo starts around 23 minutes and the squealing about 24:35.

Looks like high gain on, variac off, presence on, gain knob about noon, structure any position and the squeal is heard, just like my build.

I have to say, mine does sound a lot like this video.

I am re-inspired to get it dialed in. Going to spend some more time with the 53R - 5k source resistor value to try and match this video.

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Re: Bogner La Grange

Postby Manfred » 05 Feb 2017, 17:18

I have to say, mine does sound a lot like this video.

I am re-inspired to get it dialed in. Going to spend some more time with the 53R - 5k source resistor value to try and match this video.


Thanks for exploring the circuit. :thumbsup
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Re: Bogner La Grange

Postby Tjarko » 09 Feb 2017, 17:39

Hello for all those guys who had the noise problem with from the voltage converter.

I just made the layout for the la grange on tripboard. I used the lay out from tagboard effext.
First I had also the noise/wissle from the from the 7660 chips. When I looked at the photo's from the original PCB, I see a lot of caps and big elco's around the max1044 and TL1054. That is why I did the following:

I put on te 18volt and the negative convertor small 100nf caramic caps on the in and output(to the ground) I soldered them close to the IC's, just on top of the taggboard to one of the ground jumpers.
I also replaced the elco for the 18V for 100uf and the 47uf I used for the negative output. In the 18 volt part I put a LT1054.

After this mods the cirquit is rather sillens...............

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Re: Bogner La Grange

Postby maoriente » 11 Feb 2017, 05:52

"After this mods the cirquit is rather sillens..............."

Thanks for the power supply tips.

Question, does your pedal squeal with feedback when the gain switch is set on high, presence on, and gain knob past noon?
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Re: Bogner La Grange

Postby Tjarko » 12 Feb 2017, 01:27

[quote]Question, does your pedal squeal with feedback when the gain switch is set on high, presence on, and gain knob past noon?

Yes, on the high gain position it can stik squeal. Tomorow I will put the board in a metal box. I will see what that will do.


There is a few more thing that are still not right in the schematic. The vallue of the pot in the booster shoot be lower, in the other fet boosters they use 5K. I have order a 5k reverse log, I hope that wil give a better result.

And than wiring round the gain pot........... First I had connected the 100nf/33uf to te top op the pot. The middel/sleeve is connected to the 470nf and the 2m2 resistor. That dint not gave a smoot regulation of the gain. Looking at the schematic, there is something strange. A 2m2 resistor paralel over a 22k pot makes no differrend. So I touhgt, maybe the value is not right and I swapped is for a 22k resistor, that will change the pot curve a lot. My fist impression is that it gives a good controle for the gain.
When my build is boxed ands the knobs are on I can give a review of this mod.
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Re: Bogner La Grange

Postby Manfred » 12 Feb 2017, 13:44

The vallue of the pot in the booster shoot be lower, in the other fet boosters they use 5K. I have order a 5k reverse log, I hope that wil give a better result.

That mod has only a little effect, the start gain is about one now and will increased about two using the 5kOhms Pot.

I drew your gain pot mod, is this circuit correct:

GainPotMod.JPG
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Re: Bogner La Grange

Postby Tjarko » 12 Feb 2017, 22:03

The vallue of the pot in the booster shoot be lower, in the other fet boosters they use 5K. I have order a 5k reverse log, I hope that wil give a better result.


Hi Manfred: The gain pot cirquit you drew is rihgt, that's how I did it. I only changed the 2m2 resistor in 22k to give a better range. A 2m2 resistor make no sense in the cirquit becuase the pot gives always a lower resistense.

The 5 k pot...I ment the booster pot. I am still srugling with that one. I have the booster behind the main cirquit. I have the pot from the 4u7 to ground
A 20k lin pot gives does not give a smooth range, only a quarter of the pot gives effect on the gain. I cannot find a 20K reverse log.
The exepriment with the 5 k pot gives a smooth regulation. The only thing, lowest gain is still to high.

Do you haven suggestions to get the booster well working
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Re: Bogner La Grange

Postby diafebus » 28 Apr 2017, 18:31

How is the project doing? :horsey:
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Re: Bogner La Grange

Postby jaimebcn » 26 Jul 2017, 21:45

Hi all!

I read a lot on freestompboxes through years, awesome community!

I came from ... Probably Youtube or another forums feeding my GAS , LOL! I can't remember! Anyways I'm interested in this post. What happened at last?

I'm trying to read and understand all of the info explained.

Cheers,
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Re: Bogner La Grange

Postby Lithium_Grim » 21 Nov 2017, 13:28

If I look at the Eagle trace and the different schematics I see some differences to both the first schematic of Saruman and the updated one of Manfred.

Bogner La Grange Boost only.JPG

The difference is that compared to Manfred's schematic there is an additional pulldown resistor R13 and C2 is reversed. Offcourse the Eagle trace could be wrong, but let's say it's right, than this should be the corresponding boost schematic.
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Re: Bogner La Grange

Postby Manfred » 23 Nov 2017, 00:19

Lithium_Grim wrote:If I look at the Eagle trace and the different schematics I see some differences to both the first schematic of Saruman and the updated one of Manfred.

Bogner La Grange Boost only.JPG

The difference is that compared to Manfred's schematic there is an additional pulldown resistor R13 and C2 is reversed. Offcourse the Eagle trace could be wrong, but let's say it's right, than this should be the corresponding boost schematic.


Thanks for the hint.
On the schematics above the gate-source protection diodes are shown with different values, which is right value?
Is there anything else to make changes, before I redrawing the schematic?
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Re: Bogner La Grange

Postby Lithium_Grim » 23 Nov 2017, 08:28

Manfred wrote:On the schematics above the gate-source protection diodes are shown with different values, which is right value?
Is there anything else to make changes, before I redrawing the schematic?

No, no other real changes. You could consider adding more of the DC filter caps as in the original (100uF/47uF electrolyte and 100nF MKT/WIMA) just after the LT1054/ICL7660s +18V and -9V.
All zeners can be 10V with exception of the zener at the beginning of the power section. I'd take a 12V there.
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Re: Bogner La Grange

Postby Manfred » 23 Nov 2017, 09:44

No, no other real changes. You could consider adding more of the DC filter caps as in the original (100uF/47uF electrolyte and 100nF MKT/WIMA) just after the LT1054/ICL7660s +18V and -9V.


Please, make a sketch to me.
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Re: Bogner La Grange

Postby Lithium_Grim » 23 Nov 2017, 10:52

This is a way to make the powersection (componentnumbers are not the same as in the eagle trace of the la grange!)

Powersection.JPG
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Re: Bogner La Grange

Postby Manfred » 23 Nov 2017, 14:22

Thanks,

as I see it you using the SPlan software too.
I attache the zipped SPlan drawing file, then you can make the changes yourself.

BognerLaGrange.zip
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Re: Bogner La Grange

Postby Manfred » 26 Nov 2017, 02:24

Lithium_Grim wrote:This is a way to make the powersection (componentnumbers are not the same as in the eagle trace of the la grange!)

Powersection.JPG


I made the changes according your sketch and your annotations.

BognerLaGrange2.JPG
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Re: Bogner La Grange

Postby Manfred » 26 Nov 2017, 10:23

I have another question regarding the "J1" switch, by means of which the connection between pin1 and pin8 can be opened and closed.
Is the switch applied in the circuit?
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