Rusty Box/Traynor TS50B - are these caps backwards? + any tips

[Hemmel]

WTH is a 33nG cap ?

[Bill Mountain]

I asked about this circuit a while back and it was theorized that those 6 transistors were 3 overdriven differential amps and they are eq'd differently to distort differently.  I wonder if they will work at 9 volts or will require new biasing to clip correctly.  If I were building this I'd use a voltage multiplier to turn the 9V into 30V.

Here's my original thread:

http://www.diystompboxes.com/smfforum/index.php?topic=95021.0

[MrStab]

WTH is a 33nG cap ?

lol! "ground" - there were just a few 33nF's in the region and i thought i'd differentiate!

[Hemmel]

lol! "ground" - there were just a few 33nF's in the region and i thought i'd differentiate!

Oh !!! I thought it was an obscure Austrian way of qualifying caps. Like NanoGustavs or something 

[MrStab]

Oh !!! I thought it was an obscure Austrian way of qualifying caps. Like NanoGustavs or something 

hell no! i'm Scottish, we use the McFarad system.

thanks for the link & info, Bill - it's helping shed more light on the subject. i did plan on using a voltage multiplier to get to 15V, but is the reasoning behind your 30V to get the same range as 15 to -15? thought for a second you might've been looking at the power amp section, but that makes sense. i've already ordered two L7660's, one was as a backup but maybe i could link em as per the datasheet (although i suck at numbers). is voltage tripling (almost) practical for battery usage, or would i need to provide a higher-than-9V DC adaptor? i'll have a search. anyone know what input the actual Rusty Box takes?

[Hemmel]

hell no! i'm Scottish, we use the McFarad system.

Oh wow.... I read "McFarad" and got hungry.... DAMN YOU RONALD !!!!

[Bill Mountain]

Oh !!! I thought it was an obscure Austrian way of qualifying caps. Like NanoGustavs or something  

hell no! i'm Scottish, we use the McFarad system.

thanks for the link & info, Bill - it's helping shed more light on the subject. i did plan on using a voltage multiplier to get to 15V, but is the reasoning behind your 30V to get the same range as 15 to -15? thought for a second you might've been looking at the power amp section, but that makes sense. i've already ordered two L7660's, one was as a backup but maybe i could link em as per the datasheet (although i suck at numbers). is voltage tripling (almost) practical for battery usage, or would i need to provide a higher-than-9V DC adaptor? i'll have a search. anyone know what input the actual Rusty Box takes?

My only worry is that opamps scale up and down with voltage quite easily.  Transistor do not.  Transistors in the differential amp configuration (and also the buffer) may also not like going from a bipolar supply to a single supply.  If you aren't going to use the 30 volts and/or a bipolar supply then you might have to adjust the biasing of the differential amps to work off of a lower voltage single supply.

You may want to experiment with it some before committing to a final layout.

The Rusty Box uses a a 40V adapter.

[MrStab]

http://www.geofex.com/circuits/+9_to_33.htm

aha...

Oh wow.... I read "McFarad" and got hungry.... DAMN YOU RONALD !!!!

lol their food probably lasts longer than most caps!

[MrStab]

damn, the TL072 has a max VCC+ of 18V... in the interests of mimicking the circuit accurately, wouldn't not using a TL07* be an issue? i'm wondering if i'd be better off switching back to the original bipolar setup

[Hemmel]

lol their food probably lasts longer than most caps!

Yup, and I got the gut to prove it 

[Bill Mountain]

damn, the TL072 has a max VCC+ of 18V... in the interests of mimicking the circuit accurately, wouldn't not using a TL07* be an issue? i'm wondering if i'd be better off switching back to the original bipolar setup

I could be wrong but I always thought the 072 could handle a voltage of 36V's.  The datasheets just quote the +/- values because that's how they expected them to be used.

[MrStab]

I could be wrong but I always thought the 072 could handle a voltage of 36V's.  The datasheets just quote the +/- values because that's how they expected them to be used.

in theory, all i'd need to do to test either configuration would be to just switch wires as per this, right?

-15V has become ground, ground has become VB, and +15V has become +9V

[MrStab]

from the Rusty Box manual (http://www.tronographic.com/manuals/Tronographic-RustyBoxUserManual.pdf):

"AC Adapter supplied with your Rusty Box. If using an aftermarket AC Adapter, please be sure that it
delivers between 24VDC and 40VDC with a minimum current rating of 100mA".

granted, that includes an LED and a balanced conversion which presumably uses an opamp, but no way can this be run off a battery. i'm questioning whether or not a single charge pump would provide enough current from your average DC adaptor, or whether using 2 in parallel would, or how exactly i would sync their clocks

[Bill Mountain]

from the Rusty Box manual (http://www.tronographic.com/manuals/Tronographic-RustyBoxUserManual.pdf):

"AC Adapter supplied with your Rusty Box. If using an aftermarket AC Adapter, please be sure that it
delivers between 24VDC and 40VDC with a minimum current rating of 100mA".

granted, that includes an LED and a balanced conversion which presumably uses an opamp, but no way can this be run off a battery. i'm questioning whether or not a single charge pump would provide enough current from your average DC adaptor, or whether using 2 in parallel would, or how exactly i would sync their clocks

I don't see anything too current heavy in this design.  I suggest you experiment at alternate voltages and with using a voltage multiplier.  You can always use a single voltage multiplier to get up to 30 volts then use something like this :http://sound.westhost.com/project43.htm  to get a bipolar supply.

[MrStab]

Edit: added an on-switch as recommended by RG on another thread as an extra precaution against noise from the IC


based on:

http://www.geofex.com/circuits/+9_to_33.htm

the L7660SCPA seems to have the boost pin from the MAX1044 - would it be okay to just bridge pins 1 & 8 together like i've done? and to leave pins 4, 5 6 & 7 floating?

[MrStab]

alternatively, maybe this could work - it's based on a post by FrequencyCentral: (http://www.diystompboxes.com/smfforum/index.php?topic=69886.msg561107#msg561107)



not sure where i'd connect the ground for the multiplier board itself in that situation, though (where i put the question mark). also another TL072 would just be adding to the current draw.. either way, as this 2nd circuit is just an extension of the first, i could start with +30V & see how that goes

^^in the hours since posting this i've learned loads about the whole bipolar/relativity thing. lol

[psychedelicfish]

damn, the TL072 has a max VCC+ of 18V... in the interests of mimicking the circuit accurately, wouldn't not using a TL07* be an issue? i'm wondering if i'd be better off switching back to the original bipolar setup

According to the datasheet, 18V is relative to the midpoint between pin 8 and pin 4. I'd say you'll be fine running it on 30V

[MrStab]

relative

that's what blew open my understanding at one point last night. all i really need to change is my perspective and i can wire it up as i would any other stompbox. so i'm really glad you showed me how to reassign the vbias/ground, thanks!

just as a result of how this has evolved, i'm prolly gonna have both V+ and Vbias (or virtual ground, however you look at it) situated off the main board (ie. on the charge pump board) - unorthodox it might be, but it'll help with saving real-estate.

[MrStab]

to make a unity gain buffer for the 30V output as well, is it safe to link both an opamp's non-inverted input and Vcc+, or would i need to isolate Vcc+ in some way?  or is there even any point in doing so - i just figured it'd be good to have the V+ and Vbias both conditioned equally.
on that note, i have no 30 & 15V voltage regulators.

[duck_arse]

mrstab, you can voltage multiply as much as you like. this link has lots on doing with cmos inverters, very helpful.

http://www.gyraf.dk/schematics/Voltage_multipliers_with_CMOS_gates.pdf

as for the differential pairs, they will run happily from a single supply, if you bias the bases to somewhere near half supply. of course, if you do that with only 9V, you'll not get much headroom.

now I'll go and have a squint at your transistors' layout .....

....... pnpr3 and pnpl3: one is backwards, you pick. there are no cuts showing under the 2 18k emitter resistors and the 47nf to 2k2. otherwise, it looks sane ......