Anyone play with Bogner circuits?

[Valvehead]

Any of you fellas play around with the Ectasy preamp in a build ?

Im tweaking around on a jmp Marshall --I have a similar circuit going as the Bogner Ectasy OD hi gain channel.

Its sounding nice but Ive lost a lot of low end/bass .

Double checked everything , even changed out the old original bass pot.

To those familiar with this preamp--its has a .0047 and .0022 uf coupling caps in the early stages. I tried changing those to .047 and .022 .

The amp has almost no low end ? Any ideas ?

I cant find the scem on my pc but i could post a pic of the paper one I have If needed.

maybe i could try adding a Resonance control....

[tedmich]

is this it?

http://www.freeinfosociety.com/elect...nerecstacy.pdf

most people knock the bass flubbiness on this circuit, a decent discussion with people who have done similar stuff to you are over at sloclone
www.slocloneforums.com | Login

[Valvehead]

yes--thats the one i have

[Gregg]

http://www.freeinfosociety.com/elect...nerecstacy.pdf

Although the Ecstasy comes in different versions few notes on the schematic (as found in later models):

1/ R2 is 34k, not 68k
2/ Gain pots are 1M in parallel
3/ C8 was never used
4/ Since 2004 I think the amp comes with a factory mod where R14 is bypassed with a 220nF/2k7 combo (in series) which is in parallel to the 10k resistor (as found in CAE preamp).

The amp has almost no low end ? Any ideas ?

Looking at the schematic it's expected not to have low end that's why it has a 3 position (M-L-T) fixed resonance control called Excursion.
It's a 1M/470pF combo in parallel (L positon). In M position a 220k resistor is added in parallel with the filter combo and in T position this filter is completely bypassed.
Also make sure you have a nice big OT

[Valvehead]

Ok, that makes sense. is the Ex. switch a toggle ? on/on/on ?

[soundguruman]

They do it that way because they are trying to avoid a muddy low end sound, like mesa has.
When you get that much gain in a preamp, it's easy to mud out if you don't limit the lows.

[Valvehead]

Im having no luck , tried different stuff where the EX switch would be. It seems to just kill the volume of the amp . This project has been 1 step forward- 3 steps back...

Im simply running out of time on it (band going to record soon) so I might scrap this idea and go back to a tried and true circuit

[imaradiostar]

There was a recent thread about a resonance control in relation to a TW style amp. Look for that one- it had some good info. If the preamp is built correctly there is no reason why a shelving control can't get the bass back.

jamie

[exclamationmark]

Could it be a problem with your circuit? The shelving filters in this circuit don't really seem that extreme, and even so, you can eq back the bass at a later time. The key to a tight sounding amp is not to have the bass distort, which is probably why they removed all the bass in this particular circuit. I've done a 6 stage pre-amp that had waaaay more bass attenuation, and I've used it for both 8 string guitar and bass recording.

The thing was, it had a pseudo-parametric eq, but it still worked okay-ish with the generic FMV tone stack. Which is sort of why I don't understand where the lack of bass is coming from. Maybe if you have the effects loop up and running or have it set up as a preamp, you could get a graphic eq and see if that makes a difference, then work your way back to fixing the tone stack (ie, more bass in the neutral position).

[Gregg]

Ok, that makes sense. is the Ex. switch a toggle ? on/on/on ?

It's a 3 position on-off-on toggle switch (on-on-on is a different beast) but for more options you can replace the 1M resistor with a 1M log pot.

Below is a an updated schematic (it's big, open it in a new tab):

[Setneck]

Sorry for bumping the old thread but I'd like to ask for the Excursion thing in Bogner.

Looking at the schematic it's expected not to have low end that's why it has a 3 position (M-L-T) fixed resonance control called Excursion. It's a 1M/470pF combo in parallel (L positon). In M position a 220k resistor is added in parallel with the filter combo and in T position this filter is completely bypassed.

I try to get the relationship between fixed excursion filter and feedback resistor. It is 100k in XTC. From that info above I assume that in T position I have pure 100k in feedback circuit. And indeed T is very thin sounding.

What is happening when I switch to M or L, is the filter added in series with the feedback resistor or in parallel?

Thanks and regards, Andy

[Gregg]

In T position the Excursion filter is completely bypassed. In M and L positions it's added in series with the 100k FB resistor. In L position you have the 1M/470p combo in series with 100k, in M position the 220k is added in parallel with 1M/470p which results in a 180k/470p. You can imagine the Excursion switch and resistor like a 1M log pot with 3 positions - 0, middle and max.
Checkout Peavey 5150 schematics there it's called Resonance, in other amps Depth. Usually they use a pot combined with a higher value capacitor so there's room for experiments on this one.

[Setneck]

Thanks Gregg, informative as usuall!! .

As You may remember from other threads You helped me in, I am modding quite extensively my XTC to make it more usable in my band context. I have already changed first two gain stages to 1.5k//1uF and 2.7k//1uF (Structure circuit removed). I also lowered 1st CC to 2.2nF and output caps to 22 nF. The bass was reduced quite a lot I must say, most of the blanket fell off my cab thanks to that .

I asked about Excursion because I was also considering to mess a bit with a nfb circuit and first task was to get what the Excursion circuit is all about . I thought about removing 220k resistor and replacing 1M resistor with a pot or eventually with a trimmer. You got to drill a hole for another pot, it isn't necessary as far as a trimmer is concerned .


Thanks again for a help and tips

Regards, Andy

[Gregg]

If you're modding extensively your XTC according to some increasing preamp voltages also has a beneficial effect on the sound.
It's also a good idea to try a higher value (3n3-6n8) cap in the Excursion circuit.

[Setneck]

If you're modding extensively your XTC according to some increasing preamp voltages also has a beneficial effect on the sound

I was told already to do so and I'm still considering that mod. For what I assume, increasing preamp voltage would lower the compression and open the tone more. But the sacrifice would be shorter preamp valves life, especially PI. Plate voltage maximum for the 12AX7 of 300V is already exceeded for V5 in my amp (approx. 310V). I'm still hesitating to do that...

It's also a good idea to try a higher value (3n3-6n8) cap in the Excursion circuit.

But wouldn't larger cap let more bass thru here?