ASTROSIM (cab simulator)

[deadastronaut]

cheers man,  my mate wanted a small desktop version just so he can plug direct into his mixer

as he has no amp the poor bugger lol. ....but he has pedals.  ...


no etch, just toner transfer...

[Atodovax]

hi guys , finally finished up my cab sim project.

i present ''ASTROSIM''

very happy with it, now i can just plug in a few pedals
and record/play without an amp, and silently too...
special thanks to samhay for his input, and putting up with me annoying him a lot ha ha...cheers man. 
anyway...

includes line out, headphones out, and XLR out.....
Modern/Vintage switch.
and 3 tone/boost options.

at the end of the vid i added
a demo recording of double tracked guitar, with no post EQ at all...so you get an 'honest' idea of it..
with bass and drums...endure or enjoy...

cheers rob. ...

Hi Rob. can i plug the guitar directly to this cab sim and use the headphone out? Or do i need some type of power amp? I was planning on building a cabinet simulator and a headphone amp together in a simple 1590bb box but if this has the two sections inside im going with this one! It sounds spectacular!

[deadastronaut]

Hi yes you can do that, no probs....

Leave off the xlr parts, and you can squeeze it into a 1590bb with a small phone socket. 

[Ripthorn]

I'm actually using it with no XLR as the cab sim and headphone out for some onboard guitar electronics. I've got a surface mount PCB designed that has a Zendrive into an EP-101 preamp into the Astrosim. Still need to breadboard it to make sure I like the sound (mostly concerned about the choice of the zendrive). It will be going in a travel guitar I have designed where there is a separate jack out for headphones and one for an amp. Should make it an all-in-one travel solution.

[Ripthorn]

Alright, so I got my board all populated. I have good signal all the way to pins 5/6 of the NE5532. However, pin 7 is very crackly and something is clearly wrong. Audio probing on pins 5/6 sounds fine, voltages look to be about what is expected for the topology. Is it possible to damage one opamp in a dual opamp package? I don't have any spare 5532's at the moment, so my choice is to see if there is something else wrong or to swap it out. This is a SMD board, so I can't just pop the chip out of a socket, it's a little more hassle than that. Any thoughts on a replacement for this application?

[Ripthorn]

Brief update: I swapped out the NE5532 for a TLC2262 (only other SMD dual opamp I had on hand) and I have the same problem where the pin 7 output is really quiet, buzzy, and nasty. Not too sure what is going on here, but I put the 5532 back as it doesn't seem to be the issue. I disconnected the resistors to the output, same result. I checked the capacitance from pin 7 to the 470R resistors at output and they read 100 uF, as expected. I also checked the components in the feedback loop and they seem fine. Here are my voltages:

Source: 8.5
pin 1: 3.8
2: 3.75
3: 3.75
4: 0
5: 2.34
6: 2.9
7: 1.27
8: 8.5

I am using the schematic from the initial post, excluding the XLR out but using the headphone out. Any thoughts on what might be the issue? That pin 7 voltage seems fishy, but I don't know what could be causing it. I have checked for solder bridges and loose joints and everything appears in order, but clearly something is wrong...

[Ripthorn]

I think I found the issue. I wanted some form of headphone volume control, so I put a trimmer in place of the 6k8 on the pin 5 input. Turns out I wired it like a traditional volume pot and not a variable resistor, which messed with the bias, which would explain the nasty, fizzy, buzzy sound. I still need to try one more thing and make sure that it works end to end, but I think I solved the issue there. I'll report back.

[Ripthorn]

OK, confirmed the miswired trimmer was the issue. Makes sense, since it was bleeding off lots of VREF bias to ground through the trimmer. It now works and sounds great!  I have it wired with a zen drive and EP101 preamp onboard my little travel guitar, and it sounds great! I might be clipping when really digging in a little bit, which is probably a resistor selection issue with the EP101, since it is a fixed level. Still, I'm digging it!

[deadastronaut]

cool glad you got it sorted man.  easy mistake to make with vol trim...

i use mine all the time pretty much now...

[Ripthorn]

or replace both r25 and r26 with 47r and connect both left and right outputs together?

Yes just one resistor, both outputs tied together.
Or I suppose you could just replace the two resistors with 100R each, with much the same result.

Hey Merlin, hope you see this! If one were to use the 47R resistor, does that mean there is only a single output cap that is effectively 200 uF? I'm looking at ways of simplifying my layout and if I could ditch one of those caps and one output resistor, it would save me quite a bit of space.

[niektb]

OK, confirmed the miswired trimmer was the issue. Makes sense, since it was bleeding off lots of VREF bias to ground through the trimmer. It now works and sounds great!  I have it wired with a zen drive and EP101 preamp onboard my little travel guitar, and it sounds great! I might be clipping when really digging in a little bit, which is probably a resistor selection issue with the EP101, since it is a fixed level. Still, I'm digging it!

So you wired you're volume pot with one leg to ground whilst the signal is floating around Vbias, have you ever considered to connect that volume pot leg to Vbias instead 

[Ripthorn]

OK, confirmed the miswired trimmer was the issue. Makes sense, since it was bleeding off lots of VREF bias to ground through the trimmer. It now works and sounds great!  I have it wired with a zen drive and EP101 preamp onboard my little travel guitar, and it sounds great! I might be clipping when really digging in a little bit, which is probably a resistor selection issue with the EP101, since it is a fixed level. Still, I'm digging it!

So you wired you're volume pot with one leg to ground whilst the signal is floating around Vbias, have you ever considered to connect that volume pot leg to Vbias instead 

That's a great idea! I've never really done a lot with opamps, mostly discreet transistors and tubes, so the while biasing thing is something I'm still learning.

[slashandburn]

Hey all, hate to be a pedant here but the build docs state a dpdt On - Off - On but earlier in this thread Rob mentions it needs to be On - On - On. Will either work, or which is it?

Ive never had to use On - On - On and from a quick search they don't seem to be quite as widely available so hopefully the former.

Also, while I'm here R9 is 220R I take it rather than 220k?

Not meaning to nitpick, just trying to avoid running into problems

Cheers!

[deadastronaut]

on off on will be fine man.........


yep 220r...

vintage modern is a 2 way toggle..

the other is 3 way....

[slashandburn]

Cheers man, good stuff!

Just a few parts to order then. And those xlr sockets I could swear I have somewhere to find.

[slashandburn]

Leave off the xlr parts, and you can squeeze it into a 1590bb with a small phone socket.

Ah crap. My 1590BB just arrived and I was planning on squeezing this thing in with XLR.  And headphones. And a 9v battery. And a belt clip. I was also toying with the idea of throwing in a Muff Fuzz or something similar 

I'm not sure what I was thinking! Time for a rethink. I'm tempted to just go back to sleep in the hope the enclosure looks bigger when I wake up again.

[deadastronaut]

 
Make the 1590b version....

forgot to post these....here is a slimmed down version on the same pcb.

just no phones, or xlr.

[slashandburn]

That's reassuring. I feel a bit better about it now and think I can squeeze it all in.

Now I just need to work up the courage to either venture into the loft in search of some old cat5 for donor wire or just     grow some balls and attempt to wire up 2 pots, 4 switches, xlr and headphones using my big spool of black awg22. I'm a bit fearful of the prospect of having to troubleshooting a birds nest of wire that's all the same colour.

If nobody hears from me by Friday, uhm... Wait a little longer.

[slashandburn]

Cheers Rob this thing is excellent.

Currently using it as a headphone amp attached to my guitar strap with a switchable meathead and bass fuzz up front. Not the best choice of preamp but I just wanted to see how much I could cram into the one enclosure and see how usable it would be. I'll probably switch out the bass fuzz for something else further down the line but for now I'm having a lot of fun. Might be a late night.

[GibsonGM]

I just ordered a board, been meaning to put this one together for a while now!  Sounds very promising.  I currently use an old Digitech pedal to interface with the PC for recording, may go line-in with my pedals as Sim sounds like it can do the job nicely!