Author Topic: What would you do with an unused opamp?  (Read 324 times)

Ripthorn

What would you do with an unused opamp?
« on: March 25, 2020, 02:04:10 PM »
I just did up a dirt box that uses three opamp stages and feel it is a waste to leave the one unused one just hanging there. I breadboarded it up and made the unused opamp an MXR micro amp, but running that into the dirt box input just makes it spluttery and nasty. Straight into the amp, the micro amp sounds quite nice.

Anyway, if you had a spare opamp stage, what would you use it for? Boost? Filtering? Treble boost? Something else? Come on, not like we don't have time to play with the idea, right?! Thanks!
Exact science is not an exact science - Nikola Tesla in The Prestige
https://scientificguitarist.wixsite.com/home

EBK

Re: What would you do with an unused opamp?
« Reply #1 on: March 25, 2020, 02:11:07 PM »
My very first post to this forum asked the same question.  :icon_lol:

https://www.diystompboxes.com/smfforum/index.php?topic=115935.msg1071746#msg1071746
« Last Edit: March 25, 2020, 02:13:20 PM by EBK »
No affiliations. If I glowingly mention specific merchants or products, it is because I like them without having to be paid to like them.

Kipper4

Re: What would you do with an unused opamp?
« Reply #2 on: March 25, 2020, 02:14:57 PM »
Was one of the suggestions? Use it as a buffer for Vbias. @EBK? :icon_mrgreen:
"Duck_Arse
otherwise, you might end-up with SOIC or gullwings, for surface mounts."


Smoke me a Kipper. I'll be back for breakfast.

Grey Paper.
http://www.aronnelson.com/DIYFiles/up/

Ripthorn

Re: What would you do with an unused opamp?
« Reply #3 on: March 25, 2020, 03:19:34 PM »
Beautiful! Turns out I wasn't very active on the forum back then. I like the idea of either a clean/dirty blend or a tunable filter. I'll have to tinker more!
Exact science is not an exact science - Nikola Tesla in The Prestige
https://scientificguitarist.wixsite.com/home

EBK

Re: What would you do with an unused opamp?
« Reply #4 on: March 25, 2020, 07:48:40 PM »
Was one of the suggestions? Use it as a buffer for Vbias. @EBK? :icon_mrgreen:
The very first suggestion, in fact.
No affiliations. If I glowingly mention specific merchants or products, it is because I like them without having to be paid to like them.

Nitefly182

Re: What would you do with an unused opamp?
« Reply #5 on: March 26, 2020, 10:43:13 AM »
Buffer VREF
Add an output buffer
Switchable active filter
Run the unused one in parallel with another to double current.

Ice-9

Re: What would you do with an unused opamp?
« Reply #6 on: March 26, 2020, 11:41:04 AM »
I would get the Dremel out and grind it out of the DIL package, thus saving power so the battery will last longer. and the pedal will weigh less.  :icon_wink:

Sorry I couldn't resist just having a joke, I would most likely use it for VRef.
www.stanleyfx.co.uk

It's fairly straight forward, if you want to start it , press start. You can work out the rest of the controls for yourself !

swamphorn

Re: What would you do with an unused opamp?
« Reply #7 on: March 26, 2020, 08:38:08 PM »
I rent out my spare op amps for use by other pedals and audio electronics in general. That combined with ad support allows me to sell my pedals for much cheaper than other manufacturers. I'm still trying to figure out how to charge for the last 10% of a drive knob; do you think I can fit a card reader into a 1590A?

In all seriousness, if I have a spare op amp I'm more likely to get rid of another op amp so I can, say, use a dual instead of a quad package. VREF buffering can be nice, but if my VREF has to source or sink enough current to throw a resistor divider off I tend to rethink my design. That's just my design philosophy though; I certainly don't have a problem with buffered VREF in other people's designs.

Rob Strand

Re: What would you do with an unused opamp?
« Reply #8 on: March 26, 2020, 09:05:07 PM »
I'm not fond of buffered Vref because it can add unnecessary noise.

I like swamphorn's idea of getting rid of an opamp but that's not always going to work.
Putting a single opamp on a board full of duals would be a silly way to (not) solve the problem.
The mind often distorts without gain.

Ripthorn

Re: What would you do with an unused opamp?
« Reply #9 on: March 26, 2020, 09:12:22 PM »
Interesting thoughts on the buffered VREF, Rob. I was thinking I might go that route, as I breadboarded a wet/dry mix and, by the time I put in the buffer on the clean signal, add the blend pot, and some supporting components, I decided it wasn't the right fit for this pedal. I could just leave it unused, but I do use VREF extensively, as it saves me from doing a bipolar voltage supply. I don't want to use two charge pumps, that's just crazy talk :). So I have one charge pump to do +15V, but my entire signal path uses VREF. It sounds great, so I'm thinking I might just buffer it.

I really appreciate the conversation around here, though, lots of food for thought.
Exact science is not an exact science - Nikola Tesla in The Prestige
https://scientificguitarist.wixsite.com/home

Sooner Boomer

Re: What would you do with an unused opamp?
« Reply #10 on: March 27, 2020, 01:25:08 AM »

What would you do with an unused opamp?

Trade it for toilet paper?
Dan of 9 Toes
I'm not getting older, I'm getting "vintage"

iainpunk

Re: What would you do with an unused opamp?
« Reply #11 on: March 27, 2020, 10:10:21 AM »
Interesting thoughts on the buffered VREF, Rob. I was thinking I might go that route, as I breadboarded a wet/dry mix and, by the time I put in the buffer on the clean signal, add the blend pot, and some supporting components, I decided it wasn't the right fit for this pedal. I could just leave it unused, but I do use VREF extensively, as it saves me from doing a bipolar voltage supply. I don't want to use two charge pumps, that's just crazy talk :). So I have one charge pump to do +15V, but my entire signal path uses VREF. It sounds great, so I'm thinking I might just buffer it.

I really appreciate the conversation around here, though, lots of food for thought.

what kind of dirt pedal are we talking about? if you won't mind asymmetric powering of the opamps, you could just use the 9v as the vref, and use the opamp for a summer circuit, which is a "cleaner" way of mixing two signals

If we don't study the mistakes of the future, we're bound to repeat them for the first time.
-Ken M