Matching impedance 800ohm from audio line output etc...

[betwixt]

No offence meant!

Usually when we use matrix board, the components are on one side and the solder on the other, the component legs passing through the holes.

When you say "not connected" do you mean there is nothing at all connected to the pins?
The voltage on pin 8 (V+) is good
The voltage on pin 4 (V-) is good
The voltage on pin 3 (-in) is good, it should be half of V+ because you are tapping the voltage from two identical resistors.
However, if you do not provide feedback from the output to to inverting input (-in) it will not be able to stabilize it's operating point so the output voltage could drift anywhere between V+ and V-. It sounds like this is what is happening so check the feedback resistor is good (R3 in post #71).

Brian.

 

[Freehawk]

Hi thnx for reaction

I can imagine wondering why i do everything wrong (matrix board, haha) , i really have no idea but i am learning fast thnx to you all

I have now connected pin 1 and pin 2 to the circuit (via wire)

I disconnected the audio input on the (to be sure there is no load coming in)

Now i measure pin1 = 6.03V and pin2 also 6.03V

I thinks this sounds better... yiepiee

But know i want to be sure that i can reconnect the audio in

Can i measure in some way if it's ok to connect them

Two wires (audio signal 1 & 2) ...
how many DC voltage is normal/allowed?
how many AC voltage (its audio) normal/allowed?

The second output comes from the springreverb wich ends in a preamp (so the output of the preamp)

I just tried to measure it and i measure 170mV on the output of the preamp
and only 1.4mV on the output of the original (splitted) signal

Is this something that is ok?

And also i have question about the polarity of the capacitors now

audiosignal 1 goes to the neg side of cap1 (-cap1+) --- 10kOhm
audiosignal 2 goes to the neg side of cap2 (-cap1+) --- 10kOhm

Then they are joined

and then pin2 connected --- 10Kohm -- pin1-- +cap- and then to the outputconnector


Are they installed the right way? Do i have to change them? Please explain to me


I think i ruined the previous opamp via short (matrixboard wrong way up) or ESD

Do you think i can connect the audio signals safely , or will this be a prob for the circuit/opamp

Thnx and warm regards

 

[betwixt]

Now i measure pin1 = 6.03V and pin2 also 6.03V

I thinks this sounds better... yiepiee

But know i want to be sure that i can reconnect the audio in

Can i measure in some way if it's ok to connect them

Two wires (audio signal 1 & 2) ...
how many DC voltage is normal/allowed?
how many AC voltage (its audio) normal/allowed?

Well done!
The capacitors in the input lines are there to block DC so within reason, the DC voltage is not important. Do consider though that if the DC at the input is higher than 6.03V you should reverse the capacitor so the '+' end is to the higher positive voltage. It would be unusual for you to have any DC present when the input comes from a pickup but you should check in case the reverb pre-amp has a voltage present at it's output.

The audio (AC) level should be kept quite low compared to the supply voltage, there are no strict rules but aim for no more than about 20% of the supply voltage as your maximum. Most amplifiers are fine at low signal levels but as the output voltage increases they tend to distort and eventually clip the peaks off the signal. So from a 12V supply you should be safe up to about 2.4V of AC at the output. That is a huge amount for an application like yours though, it would be more normal to expect less than < 1V signal voltage. Any lower voltage is safe and a higher voltage might result in distortion but would be unlikely to cause damage.

Brian.

 

[Audioguru]

The peak-to-peak voltage of the audio input signals must not be more than the mixer circuit's power supply voltage of 12V. A digital multimeter does not measure audio and measures only low frequency sinewaves but not peak-to-peak from mains electricity so I use an oscilloscope. 12V p-p is about 14dBm into 600 ohms but might be double without a 600 ohms load.
The input and output electrolytic capacitors must NEVER have backwards polarity so the positive unmarked wire should be at the positive DC voltage. Frequently you do not know the DC polarity of a signal or it changes which is why I always use film capacitors (they do not have a polarity) for input coupling.

I assume that your inputs signals are at 0VDC with no DC voltage especially the signal connected to a grounded volume control. Your output capacitor probably also connects to something that is at 0VDC.
Then the polarity of your electrolytic capacitors is correct.

I am glad that you got it working. No more audio feedback?

 

[Freehawk]

Well , I am so pleased

It works , hooray , hooray hooray
I have the audiomix and i can turn up volume without feedback , wow it sounds nice to
I will now extend the system to a stereo spring reverb
I will try to replace the preamps (prebuild) with active filters (with gain) , and build a really cool effect-pedal for my synths
(dual op-amp, should be rather easy)


Thnx to all of you , but especially audioguru who was ever so patient to give me answers on maybe 'stupid' questions of me

I learned really a lot out of this.. and i am only started , now i feel confident to make the next step , bandbass highpass lowpass active filters, amplifiers whatever

It all looks easier now thnx to the support i got here

thumbs up

warm regards wherever you are

 

[Audioguru]

I was happy to hear that you got it going and that you will continue adding to it.
Post a recording of it please?

 

[Freehawk]

Dear Audioguru ;-)

I sure will when i finish the project, but it will rather be shared on youtube or something similar

For the moment it's an experimental fase... learning what could be accomplished

I want to add filters , maybe A/R or things like that , and also experiment with different kind of springs and stuff like that (maybe even way's to manipulate the reverb mechanicaly)

So I will def be in touch if i am in trouble (haha) or succeeded

I will never forget your patience and willingness to help, i was pleasantly surprised really

Warm regards

 

[Freehawk]

In fact , how could i post a sound in here?

I don't know how to do that

warm regards

 

[Audioguru]

I never tried it before but if you change a 123.wav sound file to 123.txt then it can be posted here but tell us that you changed wav to txt.
But I do not know how to change the name of a file type.

 

[BradtheRad]

Edaboard provides each member with an area to store personal files. These can be text, images, projects, sounds, etc.

Click 'Go Advanced', then 'Manage Attachments'. Upload your desired file from your computer. Drag its icon to the designated area to add it to your post. Checkmark boxes as required and click Done. (Please make a small mp3 sound file, rather than a large wav file.)

Forum policy prefers that videos not be uploaded here. If you make a Youtube video, you can embed the link in your post. The video plays within your post, via sharing from Youtube.

 

[Freehawk]

Hi Audioguru ,

I finally got everything together to make a little recording (modular synths are a pain if you really want to do something , haha)

meanwhile i replaced also the first preamp (going to he springtank) with my own circuit with a gain of x2..

So that's the recording after this (therefore it took a while)

I notice rather much noise with headphones in the background (and when all is quiet) don't notice it so much with my speakers on (therefore i was at first verry enthousastic) haha

If you hear this noise and have comments on it how to filter them or what could be the cause , i am happy to hear it
I do not have an oscilloscope , so i can't really tell in what range of frequency

I tried to use the oscilloscope software in my daw , but i can't really see the frequency i have to zoom in too much to see the noise

It's not a verry musical recording , just a short sequencer loop in different tonehights

Warm regards

 

[Audioguru]

I downloaded your Rar file but it is for a URL that says, "Complete this form to add Gmail to your Google Account" and is only 231 or 152 bytes.

This website has a very awkward way to add an image:

 

[Freehawk]

I tried again

Maybe it was my fault...

I zipped it again , hope it's ok now

Warm regards

 

[Audioguru]

I have never used a spring reverb. The acoustical reverb in a concert hall sounds completely different to the "fluttering" sounds in your recording.

 

[Freehawk]

I have never used a spring reverb. The acoustical reverb in a concert hall sounds completely different to the "fluttering" sounds in your recording.

Lol yes , but that's maybe because of me , i think i overdrive the spring tank for the moment


it can do much better , really

haha

Warm regards

- - - Updated - - -

Also i don't really know what kind of level the spring tank wants as input

and also not how much i have to amp it again to bring it at line level


For the moment it's like guessing after trying to calculate it and simulate circuits with modcircuit

But when i measure my voltages it's completely different than that of modcircuit, the output is and the gain

so i don't know really how to do it verry well , sorry for the bad recording and stuff

Warm regards

 

[BradtheRad]

I recall that I realized I might hear 'amateurish' sounding echoes from my spring reverb unit. Back during the era when spring reverbs were built into commercial amplifiers, it was typical to compare their quality. The better sounding reverbs were usually larger. They sounded more 'spacious'.

Congratulations on getting your unit to work. You made great progress. The springs reflect the sound back and forth (several times a second).

Your audio clip sounds as though the reverb is contributing a large portion. Perhaps you are applying such an intense sound, that it reflects loudly back and forth? I think you can reduce the voltage going to the spring unit. Also try taking a small amount of sound emerging from the unit, and mix it back to its input or to the pre-amp input.

Your instrument voice is a quick attack waveform, causing a noticeable echo effect. However if you try a voice with slower attack, you'll hear a more 'spacious' sounding reverb effect.

 

[Freehawk]

Hi ,

I allready use the larger spring tank from accutronics with 3 springs

I think also i have to build a high pass filter before the spring tank input , because now the lower frequencies make the springtank do noisy things...

My circuit is now own amplifier (opamp) circuit.... spring tank ... prebuild preamp (diykit) and then the mixing of the original signal via an opamp (circuit build with help of audioguru)

i will in the next days replace the preamp by my own opamp circuit and experiment with values of gain and so forth

I still wonder why i have the noise problem for the moment , on my daw i can see that there is some noise when there is no signal input , but i can't figure out in what stage it is , and how i could prevent it.

And in fact there are still spring reverb pedal effects commercially vermona spring reverb for example (but it's expensive)

So it's not something nobody uses anymore , haha , even guitaramps do still have the accutronics springtanks build in

Warm regards

 

[Audioguru]

I think your reverb sound is much too loud. "Real" reverb level is much less than the original sound level because it travels a fair distance that attenuates the reverb sound.
Try turning down the level of the reverb sound so we can hear the original sound better.

The tinny sound from the reverb spring product is probably caused by the tinny sound of its transducers.
I think walls, carpets and acoustical ceiling tiles attenuate higher audio frequencies in "real" reverb sound. Try turning down the treble tone control on the reverb and it will also reduce the tinny sounds.

 

[Freehawk]

Maybe it is...
In a previous config (with the two preamps) there was a way to distort the sound a tiny bit ... i liked it , and terefore experimenting with levels that maybe can distort a little bit..

I do not have a treble tone control at this moment

But indeed i need also a variable (potmeter) control of the soundlevel , now it's 2.5x gain to the input of spring tank

I tried to implement it , but strangly enough it didn't work till now (i tought replacing the resistor R2 (paralell to opamp) with a potmeter of combination of lower R2+potmeter) but it did not have the result i tought

Warm regards

 

[Audioguru]

Here are two ways to adjust the level of the reverb: