OpAmps for DIY Bass & Guitar Pedals

...and how to do so...
User avatar
khanyz
KVRAF
1557 posts since 16 Jul, 2004 from Deepest Yorkshire

Post Sun Aug 28, 2011 4:06 pm

Hi All,

I've started prototyping (breadboard) some preamps and effects for guitar and bass and am on my way to firing up the soldering iron and commiting them to a metal case.

However, before I finalise anything, I'd like some feedback on the myriad of OpAmp available and the hype that goes along with them. I started out with some schematics and the JRC 45xx but have switched to OP27GPZ's for some things. I also got some OP2134's and am trying an OPA404 for a bass preamp (maybe 2 as I need them for gain, drive, opto compressor and tone).

I suppose my question is, what are the key elements/specs in an opamp to look for, and the sound qualities they exhibit. For example, the OP27GPZ is less harsh than the JRC4558.

Also the benefits/hassles of going discrete are still bothering me. Apart from wanting an all germanium circuit, is it worth going discrete?

Cheers,
Nigel

BTW: The TI version of Tina is awesome.
I miss MindPrint. My TRIO needs a big brother.

xtp
KVRian
848 posts since 4 Jun, 2006

Post Wed Aug 31, 2011 10:43 am

This question might be better answered on diystompboxes, freestompboxes, thestompbox or prodigy.

I mainly use TL072's. I am currently considering breadboarding a circuit that has NE5532 opamps spec'd.

Burr Brown stuff is well thought of.

At the end of the day the only real way to find out is to try a range of them and come to your own conclusion - we all have different ears. Either try it on your breadboard or put a socket on your circuit board.

Peoples opinions differ radically. Some people wont use op-amps, they say transistors are more musical, then there's the Jfets sound more like tubes line of thought.

For example when I wired the circuit for my electric guitar I researched a lot of wiring options, read a slew of other peoples opinions, but in the end I just soldered it up a number of different ways until I found the circuit I gelled with.

One of the good things about diy is the ability to customise. :)

@discrete circuit. It will take up a lot more enclosure space, but if you are going to rack your effect and prefer the sound, then why not. It would take up considerable space if your circuit has a lot of op-amps.

User avatar
khanyz
KVRAF
1557 posts since 16 Jul, 2004 from Deepest Yorkshire

Post Wed Aug 31, 2011 11:08 am

^
I've read through a lot of the other forums and there's already too many OpAmp thread so I'd thought I'd get a different perspective here. There's plenty of members who do DIY guitar stuff.

With the number of different OpAmps out there, like with plugins, it's impossible to go through them all but I've tested quite a few and I just wanted a couple more to check out. At the moment, I'm basically going through the ones at www.doctortweek.co.uk at the moment, plus some BB ones I found on ebay. I do have a NE5532P which I haven't tried yet.

As for discrete, I'm heading in that direction for gain stages, but sticking with OpAmps (OP2134) for tone circuits. I've got a selection of Bipolar and FETs, in silicon and germanium, so I've just going to keep switching things round.

As for guitars, I'm just finishing one up. Component placement was easy as I wanted to keep it simple and blend, rather than switch, pickups. The only complication was the values for the treble bleed. I also played with PIO capacitors but stuck with Spragues.

Cheers,
Nigel
I miss MindPrint. My TRIO needs a big brother.

User avatar
antto
KVRAF
2509 posts since 4 Sep, 2006 from 127.0.0.1

Post Wed Aug 31, 2011 11:21 am

LM833 sound good-ish (used 3 of em for a compressor)
TLC272 too
haven't yet tryied TL072 or the NE55** ones
It doesn't matter how it sounds..
..as long as it has BASS and it's LOUD!

irc.freenode.net >>> #kvr

User avatar
khanyz
KVRAF
1557 posts since 16 Jul, 2004 from Deepest Yorkshire

Post Wed Aug 31, 2011 1:52 pm

^
I bought a few more, including the LM833 to try. Thanks.
I miss MindPrint. My TRIO needs a big brother.

User avatar
Dean Aka Nekro
KVRAF
6179 posts since 4 Oct, 2007 from Escaped At Last

Post Wed Aug 31, 2011 6:09 pm

Send off to TI and others for free samples Nigel (under the premise that you are a company and you are prototyping something. If you don't take the piss they do send out a good amount. If you have any friends that would let you do the same then you can get rather alot of free stuff ;) as the address is different all you will have to do is pick up the packages when they have arrived)

Obviously it wont cover old stuff that is not made anymore. Have fun mate :)

Dean

User avatar
khanyz
KVRAF
1557 posts since 16 Jul, 2004 from Deepest Yorkshire

Post Wed Aug 31, 2011 9:30 pm

^
Thank for the tip Dean. I do plan on making some things for others so it should be OK.

Cheers,
Nigel
I miss MindPrint. My TRIO needs a big brother.

insonicbloom
Banned
81 posts since 16 Dec, 2010

Post Thu Sep 01, 2011 12:30 pm

electronics is my bread and butter so out of everything on this forum I am most qualified to comment on this thread.
first of all the BYOC forum is great so go sign up there, you'll see me and some of my guitar based designs on there, oh and my theremin too.
op-amps are things that audiophools have latched onto but in terms of a signal being amplified in the audio spectrum they really don't differ too much and in most cases not at all, you get some which have less gain than others like the NE5532's so these are more suited to things like phasers where the op-amp is part of an oscillator rather than a signal pass-through.

typically if you hear a difference between a TL072 and a burr brown op-amp then you're imagining it to justify the amount of money you spent extra on the burr brown. BB chips are accurate for high speed electronics but they do nothing extra with audio than a TL072 and the JRC4558 don't sound any different either which is why the designers of tubescreamers didn't deem it necessary to put them in the newer pedals. There is one crucial difference between a newer op-amp and a hallowed JRC4558 or a LM308 though and that is that the old ones are prone to failure due to the crap manufacturing process and impurities in the dyes and these don't affect the sound because the nature of op-amps is the dye is either good enough to work or not work, there is no real error they just fail sometimes.

discrete systems can vary in sound purely because of inductance and capacitance. I made a discrete op-amp when I was at college a long time ago to prove this phenomenon so I can buy the fact people prefer one over the other but that is subjective.

something else I should bring up here is the fact I heard someone use the word "sprague" referring of course to the capacitor. trust me when I say this. these capacitors if exactly the same value do not change in sound whether it is a sprague or some grey market low hung piece of shit from china. it is the value of capacitance that affects the sound and not the brand written on it. people latch onto these weird little rumours but it needs to be nipped in the bud, these are electronic components and they follow a logical state and not scriptures from the bible. the only reason one will sound different is if it has drifted from it's value - in which case it needs changing.

Germanium transistors do sound different to silicon, they have a sort of glassy sound to them when you push them to overdrive, this is an unwanted by-product of Ge transistors but it sounds really good with guitars unfortunately their performance alters with ambient temperature.

if you want any help give me a shout, and I took full advantage of the free samples thing, I've got thousands of samples, ASICs, DSP, military grade op-amps which look cool and would survive in space should I ever want to play my guitar there, filters, ADCs and just everything. I got them to send them to Deans house too haha

User avatar
Hink
Rad Grandad
29080 posts since 6 Sep, 2003 from Downeast Maine

Post Thu Sep 01, 2011 12:34 pm

great post insonicbloom thanx :)
Albert Einstein may have been a genius but his brother Frank was a monster

xtp
KVRian
848 posts since 4 Jun, 2006

Post Thu Sep 01, 2011 12:59 pm

khanyz wrote:^
I've read through a lot of the other forums and there's already too many OpAmp threads
It is a distraction sometimes getting bogged down reading a myriad of opinions. I think too it depends what the end product is. I built a filter that I designed myself and Tl072's were fine. I was looking for transparency as opposed to 'mojo'.

I am not a big effect user as my stuff is generally clean tone. I own a Joe Meek optical compressor which I use in front of my reverb.

I have been thinking of breadboarding the ROG Umble drive circuit and one of the available opto compressor circuits available on the net.

The idea would be to try and fit both in a single 1790. Not sure if there will be room. The optos seem to need +/- 15v. The only downside is I can only find one supplier in my country for the Silonex cell and I have to buy 5 minimum.

User avatar
Uncle E
KVRAF
11020 posts since 22 Nov, 2000 from Southern California

Post Thu Sep 01, 2011 1:48 pm

insonicbloom wrote:typically if you hear a difference between a TL072 and a burr brown op-amp then you're imagining it to justify the amount of money you spent extra on the burr brown.
I replaced a TL072 with an OP2134 in an OCD circuit and the sound instantly became clearer, sharper, and cleaner. I have a stock OCD to A/B it with.
BB chips are accurate for high speed electronics but they do nothing extra with audio than a TL072 and the JRC4558 don't sound any different either which is why the designers of tubescreamers didn't deem it necessary to put them in the newer pedals.
Ibanez DID go back to the JRC4558 because the replacement op amp was darker sounding than the JRC4558. I put a JRC4558 into my mid-90's TS9, that made it sound like SRV.

insonicbloom
Banned
81 posts since 16 Dec, 2010

Post Thu Sep 01, 2011 1:58 pm

are you trying to tell me that a general purpose amplifier block in someway acted as an exciter? because if that's the case you better get onto Aphex because they are out of business!

the only reason ibanez will have gone back to the JRC4558 is if they found it cheaper than whatever they were using in place of it.

by the way, if you stick your cables in the freezer over night they will sound better!

go and watch this http://www.youtube.com/watch?v=m7ERMu825m4

User avatar
Dean Aka Nekro
KVRAF
6179 posts since 4 Oct, 2007 from Escaped At Last

Post Thu Sep 01, 2011 2:12 pm

Yep i can confirm that i have signed for alot of sample packages as mentioned and then took them over to insonicblooms' place (So it does work Nigel man). Also i can confirm that his speciallity and earth bound love is electronics, Telecasters and audio/music. John you and Paul would get along famously here and Facebook :)

All the best to all

Dean

xtp
KVRian
848 posts since 4 Jun, 2006

Post Thu Sep 01, 2011 2:22 pm

insonicbloom wrote:...
go and watch this http://www.youtube.com/watch?v=m7ERMu825m4
Hahaha, that was most entertaining. Aussies. :wink:

User avatar
Uncle E
KVRAF
11020 posts since 22 Nov, 2000 from Southern California

Post Thu Sep 01, 2011 2:30 pm

insonicbloom wrote:by the way, if you stick your cables in the freezer over night they will sound better!
Have you swapped out the op amps in the OCD and TS9 circuits?

Return to “DIY: Build it and they will come”