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Swapping Boss DS-1 Opamps listening test

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Swapping Boss DS-1 Opamps listening test

Postby Martin Walker » Sat Apr 21, 2018 3:47 pm

https://reverb.com/news/swapping-boss-d ... -in-action

Stumbled across this page this morning, and while I know full well that simply swapping opamps in an existing circuit can be prone to problems (and even ultrasonic instability), I was fascinated to hear the HUGE tonal differences between a selection of named opamps being systematically inserted into an IC socket in this simple stomp box.

Comments anyone?


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Re: Swapping Boss DS-1 Opamps listening test

Postby thefruitfarmer » Sun Apr 22, 2018 8:53 pm

A Boss DS-1 is a pedal that is often modded.

A lot of people don't like the sound of it but it is dependant on the amp you use. There has to be a good crunch in the amp sound anyway and the DS-1 will push the amp in a cool way if it is a good valve amp and it works well with my Award Session Blues Baby. It sounds harsh into the clean channel of a Peavey Bandit though...

Not sure why people mod it though, in my mind it is easier to get another pedal that works with the rest of the kit.
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Re: Swapping Boss DS-1 Opamps listening test

Postby resistorman » Sun Apr 22, 2018 9:40 pm

Interesting, for sure. It’s easier to grok when it’s a jfet input, but they all sound different. Another interesting thing from this article... it lead me to the Texas Instruments site to look at the ne5532 and I found they sell interesting evaluation boards and kits. Hmmm...

http://www.ti.com/product/NE5532/toolssoftware
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Re: Swapping Boss DS-1 Opamps listening test

Postby Martin Walker » Mon Apr 23, 2018 12:40 pm

resistorman wrote:Interesting, for sure. It’s easier to grok when it’s a jfet input, but they all sound different.

This is what amazed me - I was fully expecting minimal tonal changes (far less than changing silicon clipping diodes for germanium or schottky for instance), but each one of those opamp changes had a radical effect on the final sound, particularly with regard to the amount of bottom end.

I must look into the DS-1 circuit - perhaps the coupling capacitors are tiny for use with jfet input opamps, so non-FET replacements remove the bottom end, but frankly I was staggered at the size of the changes.


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Re: Swapping Boss DS-1 Opamps listening test

Postby Hugh Robjohns » Mon Apr 23, 2018 2:55 pm

Without knowing the circuit configuration it's impossible to say what's going on. You've obviously got different input impedances affecting signal levels and filter time-constants, but also potentially different output DC-offsets affecting following stages, different overall gains and gain-bandwidth products, completely different behaviours with signals approaching the power rails etc etc...

This is precisely what annoys me with the chip-swap brigade. They treat op-amps like they're sweeties of different flavours when they are much more complicated and involved than that! They may have similar pin-out's but the clever stuff inside is often radically different and requires very different supporting circuitry to operate as intended -- or even to operate to spec at all! This random plug-n-play game diminishes the skill of the electronics engineer and rewards (apparently) ignorance... IMHO

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Re: Swapping Boss DS-1 Opamps listening test

Postby ef37a » Mon Apr 23, 2018 4:00 pm

I completely agree with Hugh, such tests are unscientific and lead to "cork sniffing" claims as to the performance of various components that are simply wrong but there is a paradox here.

The "Guitar Distortion Pedal" does not play fair with amplifiers, op or discrete. This is because once ANY device is driven into serious non-linearity, all bets are off. If the same chip swapping process was done with say the op amp line input stage of a mixer and care was taken to avoid distortion I would defy anyone to tell the difference between a venerable 741 and the rather splendid LM 4562 (maybe a bit of noise?)

One parameter that is very different for various op amps is Slew Rate but, the 742 excepted, I know of no IC that cannot cope with full output to at least 20kHz? However, once the circuit is into serious distortion it is possible that SR COULD be a factor in the sound?

From the circuit* I have found the second chip stage drives a diode clipper through 2k2. Now, the TL072 series are rather poor at such a low load whereas the 5532/4562 will consider it impudent. Another area of sonic difference? Note too that the tone control is hung on the clipper? That will be affected by the change of chip OPZ as it goes into overload. The TLs of course go into a 'latch/flip' mode if drive too hard!

The point of all that rambling is that YES! Different op amps WILL sound different when you 'abuse' them. Then The Story becomes.."There are good and bad sounding op amps" Not so. Used within their ratings I maintain they will all be equally transparent (shades of the SoS 'mic pre amp, 'not' a shootout?)

*I found loads! And interestingly the op amps used were all different. In addition to the NJM 3404A in the link.
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Re: Swapping Boss DS-1 Opamps listening test

Postby CS70 » Mon Apr 23, 2018 4:55 pm

By itself, if the pedal and the amp don’t blow up and the sound is good, it doesn’t matter that people obtains that without knowing why.

What’s annoying is when they think they do, and start to clssify stuff and offer ‘expertise’ out of thin air. We don’t need to understand the physics of light to love a beautiful sunset, but them it’s best to just appreciated it in silence :)
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Re: Swapping Boss DS-1 Opamps listening test

Postby Folderol » Mon Apr 23, 2018 5:50 pm

I think my immediate thoughts have already been covered :(
I would only add, this sort of random swapping could become very expensive if tried on something like a high power amplifier :thumbdown:
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Re: Swapping Boss DS-1 Opamps listening test

Postby Martin Walker » Tue Apr 24, 2018 7:33 pm

Thanks for all your thoughts folks - although I must say when Dave said "From the circuit* I have found the second chip stage drives a diode clipper through 2k2." almost everything about the tonal changes was explained :beamup:


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