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

[Freehawk]

Hi,

I am really new to this kind of thing , sorry for that

I just want to know if someone can explain to me what i need for

a) converting a line level output to an input of 800ohm
b) converting a ouput 2600ohm to a line level input


I need it to use a spring reverb (accutronics) into my audio rig

I am not an electronic specialist , just a musician...
I searched the internet for it but i don't understand a word of it

So i hope someone will know and willing to explain me in dummy-language , haha

Warm regards & thnx

Fhawk

 

[Vbase]

In general impedance matching can be done by a transformer or amplifier.
In your case it is good enough if you connect it directly and forget about impedance matching.

 

[Freehawk]

That sounds good but when i do i hear no reverb
I think the signal needs amplification on both ends, before the accutronics spring and after the output

But what i wanted to look for was a not expensive solution , i can get results if i use my preamps on both ends, but that would mean paying 1600$ (800 each preamp) So i can't imagine there is no better cheaper way to do it


Warm regards

 

[Vbase]

It looks like you already have proven that you need impedance matching or amplification. If you add to the post a link or drawing of both your amplifier and/or reverb I'm sure we can help.

 

[Audioguru]

A preamp circuit costs less than $1.00 so you are being ripped off. Audio circuits do not match impedances:
1) The output of a preamp is the output of an opamp that has an impedance less than 1 ohm and it feeds the input of a power amplifier that is 10 thousand ohms or more.
2) The output of a power amplifier has an impedance that is 0.04 ohms or less and it feeds an 8 ohm speaker.

Why is your input with an impedance of only 800 ohms? Many opamps cannot drive an impedance that is less than 2000 ohms.

The Accutronics USA made (not Korean) Type 8 spring reverb has an input impedance of 8 ohms like a speaker so it can be driven by a little audio power amplifier IC like an LM386 that costs about $1.21. It has an output impedance of 2250 ohms and feeds an amplifier with an input impedance of 5000 ohms or more. If the reverb unit feeds your amplifier that has an input impedance of only 800 ohms then its output level and high frequency resonance will be severely reduced. An opamp that can drive 600 ohms or more can be added for less than $1.00 to boost the impedance the reverb unit is driving.

 

[Freehawk]

Sorry for the confusion... I have a accutronics type 9 9EB2C1B
Input impedance 800ohm
output impedance 2575 ohm

Did i buy the wrong ones??? :-(

I also did not buy the preamps for that prupose , but for mic preamping
But i used it to test out what i needed (only in a much cheaper version i hoped)

So thnx for the answers till now

Warm regards

- - - Updated - - -

Could you for example tell me what kind of amplification i would need?
Is this a simple amplifier of 1W or so??

I really have no idea

Thnx for aswering , warm regards

 

[Vbase]

I forgot to warn you that 'matching impedance' is a swear word in Canadian.

You can use a kit like this one or something similar.
**broken link removed**

 

[Audioguru]

I found your reverb unit in a Fender Junior schematic on a website called "tubes and more" but I lost its address. It shows one opamp in a dual TL072 opamp driving it and the other opamp buffering its output.
The impedances are very far from being matched.

The Chinese preamp/tone board has absolutely NO specifications. It has a very poor translation from Chinese to Engrish.

 

[Freehawk]

Hi ,

thnx for the efforts..

I found something on a website **broken link removed**

And it makes me even more confused ...

especially this diagram https://www.preservationsound.com/wp-content/uploads/2013/08/Reverb_Doa_2.jpg

He uses a spring reverb from accutronics and drives it from a analog output (line level?)

But he has 2 preamps , a converter , and an amplifier in use ....

I don't even understand the schematics of it ... it would set me 180$ back , but i don't know why it is necessary

Is anyone able to explain this to me? Or is this just overkill?

Warm regards

 

[BradtheRad]

I think a low-power audio amplifier is sufficient to start experimenting with. Post #5 recommends an LM386, a popular IC designed to drive a speaker at low volume.

I once had an inexpensive spring-reverb unit, 4 or 5 inches long. I seem to recall hooking it up to a bitty transistor radio, and sending the output through my 3-inch tape recorder for live listening.

To do that I had to have patch cords, jumper clips, inline volume control, etc.

 

[Externet]

Try feeding the reverb input with a headphone output of the preceeding unit. The reverb output to feed another speaker amplifier.
If no success, feed the reverb input from a speaker output of the preceeding unit; be gentle with the volume knob.

 

[Freehawk]

I will try the headphone out ...
But it's a synth module , so it has no speaker output

Anyway I tried it first with two preamps (mic preamps) and i had to crank up to a gain of 35db before i had a good result (both of them) one before the springverb (from synth out to spring in) and one after the spring reverb (from spring out to line input of mixer)

But these preamps are tooo expensive to be used for that purpose

Warm regards

 

[betwixt]

My experience of spring reverbs is they use a small audio amp ($1) driving a small loudspeaker ($1) with a wire spring glued to it to send the sound in and at the pick-up end they either use another loudspeaker or a vinyl record player cartridge with the stylus removed. It fits the diagrams and descriptions in the previous posts.

As you are in Europe, read Euro for $.

Freehawk, don't be fooled by high costs, the audio market is full of 'hyped up' descriptions and super elevated prices. For example, I have a pair of "super fi, mega boost loudspeakers here" which are plastic cases with one 50mm 8 Ohm loudspeakerin them, marked 0.25W. The label on the outside claims 300W peak power rating!

Brian.

 

[Audioguru]

Your spring reverb has an 800 ohm input impedance that can be driven from one opamp in a $.66 cost TL072 dual audio opamp, it is not 8 ohms like some spring reverbs that must be driven from a little power amplifier. The second opamp can amplify its output. Why spend $180?

The article you found uses an 8 ohm spring reverb driven from a 1.5W power amplifier. It was designed by a kid who knows nothing about electronics which is why it is confusing and shows the last amplifier connected backwards and it has two power supplies instead of one.

 

[Freehawk]

Yes, i don't really want to spend 180$ too

But for me it's all like chinese but i will try to find a preassembled DIY kit (opamps) , soldering is not really my hobby But maybe i learn it with some other diy stuff... who knows...

Anyway it's a great help to have your meaning about it... i am now confident i will find a cheaper solution, and if it's only a few dollars it can't go wrong

Thnx a lot

Warm regards

 

[Audioguru]

But for me it's all like chinese

I know. My son is not a mechanic but he changed the wheels on his car. He saw the front wheel go flying past him on the highway. Luckily he stopped the car safely without being hit by another car. I helped him find the wheel that rolled very far along the guardrail.

 

[d123]

Hi,

Hope this showed up while you were searching the 'net:

**broken link removed**

In Elliot we trust, very much. Not "Snake Oil".

Good luck.

 

[c_mitra]

Can you please explain the setup? Impedance mismatch will reduce effective power transfer but then it should not be so critical...

You have mike- it goes to a preamp- then to the power amp- then to reverb unit- and then to the speakers? Or, does it go to the power amp after the reverb unit?

Just put a small speaker close to the mike and you will hear reverb! (joking!)

Or, what I like best, is to introduce reverb in audacity (an audio software)

 

[FvM]

Audio circuits rarely implement impedance matching. In almost every case you have Rsource >> Rload. E.g. a power amplifier driving a 4 or 8 ohm speaker has usually < 0.1 ohm output impedance. The output impedance must not be confused with the nominal or rated load impedance of a power amplifier. But using an amplifier with it's rated load isn't what we call impedance matching.

Similarly, the input impedance of preamplifiers is usually considerably larger than the source impedance.

In case of the reverb unit, this means that the driver amplifier must be rated for a load smaller or equal than the actual send transducer. And the preamplifier for the receive transducer should simply have a sufficient high input impedance and isn't critical at all.

I agree that operating a classical reverb spring in the age of cheap DSP effects is somehow nostalgic. But may be you want exactly the retro tinny sound.

 

[Freehawk]

Well yes i like to have analog effects rather that software or dsp effects