Divided by Thirteen CeeJay Eleven

Tube or solid-state, this section goes to eleven!

Re: Divided by Thirteen CeeJay Eleven

Postby swt » 09 May 2010, 20:20

that look a lot like the trainwreck express with el84 that used to be in lots of version in a pdf at the old forum...
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Re: Divided by Thirteen CeeJay Eleven

Postby conger » 09 May 2010, 21:34

snyder80 wrote:I think the boost is designed in a different way, too.
It looks like there is that cc 100k goes between the pot´s (ungrounded) GND-Side (lug 1) and GND (the brown wires). Just have a look at the pics on page1 !


I'm not familiar with that kind of pot with switch. What is the layout of the switch and where are the pot terminals?
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Re: Divided by Thirteen CeeJay Eleven

Postby snyder80 » 09 May 2010, 23:34

look at this page: http://www.beavisaudio.com/techpages/Pots/

lug1 usually goes to ground. but take a look at gutshot1 on page1 of this thread. you can see the gainpot with the push/pull funktion. there u see the lug 1 from the gain goes to the 100k across the two poles of the combined push/pull switch. from the right pole of the switch the brown cable is connected to the ground-bus.

Its much more easy to undestand what i wrote if yopu look at the gutshots...

or in simple words: the 100k boost-resistor doesnt belong to the tonestack "middleresistor" but to the gainpot´s lug 1.

like this :
from tonestack in (lug3) --> |
|-----> wiper (lug2)
|
v (lug1)
|------------------|
on/off switch 100k
|------------------|
v
GND

EDIT: damn, the boards layout destroyed my fancy ASCii-graphic. but i think you get it anyhow...
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Re: Divided by Thirteen CeeJay Eleven

Postby snyder80 » 11 May 2010, 08:08

i must correct myself!

they made the "boost" in a more common way! after having a look at the pics on page 2 (download/file.php?id=7229&mode=view) you definitly see, the 100k is connected between the wiper of the gain (lug2) and ground (lug1).

so the boost definitly isnt in the tonestack, althoug some do this kind of mod in a fender princeton design.
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Re: Divided by Thirteen CeeJay Eleven

Postby conger » 11 May 2010, 09:11

snyder80 wrote:i must correct myself!

they made the "boost" in a more common way! after having a look at the pics on page 2 (http://freestompboxes.org/download/file ... &mode=view) you definitly see, the 100k is connected between the wiper of the gain (lug2) and ground (lug1).

so the boost definitly isnt in the tonestack, althoug some do this kind of mod in a fender princeton design.

Do you mean something like this? I can't make out the switching from the photos. Also is the 250pF added in parallel to the bright cap?
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Re: Divided by Thirteen CeeJay Eleven

Postby snyder80 » 11 May 2010, 16:10

to me from the pics it looks exactly like what u draw up!
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Re: Divided by Thirteen CeeJay Eleven

Postby sagajam » 11 May 2010, 18:15

Hello,
this boost circuit is quite a riddle :scratch:

I tried to follow the brown wires coming from volume pot and I think
the other is going to ground but other is going to tonestack. If I'm right
it is connected to .1 cap (the bass pot side of it).

Look at this picture and that brown wire connected to .1 cap:
download/file.php?id=7217&mode=view

What could be reason for this connection?
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Re: Divided by Thirteen CeeJay Eleven

Postby snyder80 » 11 May 2010, 18:53

@ sagajam:

i dont think it is or should be connectet the way you think.

1. The pic you linked shows the 2 cathode caps/resistors for V1A and V1B. An definitly the brown cable get to the corresponding ground bus for V1 A/B!

2. Ground in this build is bowrn "colorcoded".

3. Look here : download/file.php?id=6637&mode=view together with the pic YOU linked you see the 100n cap is definitly straight connected to the whity shielded cable from the bass-pots´wiper. Absolutly no connection between that 100n cap and the "suspicious" boost-function for me 8)

So after all i think congers drawing should be right...
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Re: Divided by Thirteen CeeJay Eleven

Postby conger » 11 May 2010, 22:11

This picture below shows what looks like the brown wire connected to the first tube ground point. I cannot see the point of such a connection therefore, I think it is probably connected to the .1uF. Otherwise why would that brown wire be there?
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Re: Divided by Thirteen CeeJay Eleven

Postby sagajam » 11 May 2010, 22:46

conger wrote:This picture below shows what looks like the brown wire connected to the first tube ground point. I cannot see the point of such a connection therefore, I think it is probably connected to the .1uF. Otherwise why would that brown wire be there?


I didn't see ground connection there at first either, but now I see it. The connection
between that brown wire and cathode cap is bit dark but it is there like snyder said.
I just wonder why that brown wire is so long, there is ground points much closer to
vol pot...
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Re: Divided by Thirteen CeeJay Eleven

Postby snyder80 » 11 May 2010, 23:55

it is called something like "corresponding grounding". So the Ground from V1´s cathodes is used to avoid groundloops and such, because the tonestack is placed between V1A and V1B...

Connecting the 100n "bass cap" to Ground would simply bypass the Bass pot /Middle resistor.

EDIT:

I think i found it out now for sure. Look here : download/file.php?id=7213&mode=view
and there download/file.php?id=7226&mode=view !!!

100k goes between the 10uF cathode from V1B cap and ground. THAT is a typical boost-design (by jumpering the 100k).
maybe the 250pF cap is across the 100k, too. Because of the camera angles of the close-ups for the gain pot it could look like the 250pF is connected from wiper to GND.
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Re: Divided by Thirteen CeeJay Eleven

Postby sagajam » 12 May 2010, 06:23

snyder80 wrote:100k goes between the 10uF cathode from V1B cap and ground. THAT is a typical boost-design (by jumpering the 100k).
maybe the 250pF cap is across the 100k, too. Because of the camera angles of the close-ups for the gain pot it could look like the 250pF is connected from wiper to GND.


Now this is starting to make sense :D
It definetly looks like 250p is connected from wiper to GND, in that case it should darken
the tone pretty much. I have to try that in practice...
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Re: Divided by Thirteen CeeJay Eleven

Postby conger » 12 May 2010, 09:43

snyder80 wrote:I think i found it out now for sure. Look here : http://freestompboxes.org/download/file ... &mode=view
and there http://freestompboxes.org/download/file ... &mode=view !!!

100k goes between the 10uF cathode from V1B cap and ground. THAT is a typical boost-design (by jumpering the 100k).
maybe the 250pF cap is across the 100k, too. Because of the camera angles of the close-ups for the gain pot it could look like the 250pF is connected from wiper to GND.

I think you are onto what is happening with the 100K. As you pointed out, in the picture below, the second stage cathode bypass cap ground is led off to the brown wire that goes back to the switch. The only reason for this must be to switch that cap in and out of the circuit.

The 250pF is still a bit of an enigma. The first idea that it adds an additional bright cap makes more sense than anything else I can think of at the moment. A silver mica cap has been chosen so it probably has a signal passing role.
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Re: Divided by Thirteen CeeJay Eleven

Postby sagajam » 12 May 2010, 11:06

The 250pF is still a bit of an enigma. The first idea that it adds an additional bright cap makes more sense than anything else I can think of at the moment. A silver mica cap has been chosen so it probably has a signal passing role.[/quote]

Hello,
That 250pF could be so called "Anti-bright cap", when volume is turned up it starts to dump
more and more treble to the ground. It works like bright cap but opposite. That could cure fizziness
I had with higher gain settings..
When volume is turned down 250pF becomes less effective, just like
100pf bright cap becomes less effective when vol is turned up.
That way cleans are nice and bright and gain is less fizzy.
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Re: Divided by Thirteen CeeJay Eleven

Postby snyder80 » 12 May 2010, 11:18

sagajam should be right !

250pF is def. no bright cap, since its undoubtfull connected between the gain-pot´s wiper and ground.

BUT myserious was wether there is another connection from 250pF cap (wiper-side) to the swith. I think the pics fooled myself now i attached some work to clarify.
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Re: Divided by Thirteen CeeJay Eleven

Postby conger » 12 May 2010, 11:23

Looking at this schematic for the FTR37, the first stage has a 1k5 with a switched 22uF boosted cap but the 1k5 also has a 100pF across it. So maybe the 250pF (scaled up for the 3k3) is permanently across the cathode? I have never used such a small cap for a cathode bypass but you never know, it may be a magic ingredient.
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Re: Divided by Thirteen CeeJay Eleven

Postby snyder80 » 12 May 2010, 11:30

Its an argument for such a "corprate design", and i thought it were like this at first, tooo!

BUT:

look at that attached pic (and 2nd & 4th pic in the posting above). 250pF is definitly beween GND and Wiper...
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Re: Divided by Thirteen CeeJay Eleven

Postby conger » 12 May 2010, 11:59

snyder80 wrote:look at that attached pic (and 2nd & 4th pic in the posting above). 250pF is definitly beween GND and Wiper...


Yes, you are correct judging by that picture. Question is why have a 250pF to ground? I would expect that to remove everything the 100pF passes plus a bit more.
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Re: Divided by Thirteen CeeJay Eleven

Postby sagajam » 12 May 2010, 13:13

conger wrote:
snyder80 wrote:look at that attached pic (and 2nd & 4th pic in the posting above). 250pF is definitly beween GND and Wiper...


Yes, you are correct judging by that picture. Question is why have a 250pF to ground? I would expect that to remove everything the 100pF passes plus a bit more.


Look at my previous post, basically it will remove high-end fizzyness when volume is turned up.
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Re: Divided by Thirteen CeeJay Eleven

Postby conger » 12 May 2010, 14:02

sagajam wrote:Look at my previous post, basically it will remove high-end fizzyness when volume is turned up.

Cool. I must try that.

In that case the schematic should be about finished. Thanks all.
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