Double Bass Impedance matching for Realist pickup

[Ric Vice]

Hey everyone,

So the realist website says that the pickup impedance level is 10mg ohm. My amp's input impedance is 1M ohms (GK 112). I read that ideally an input impedance should be least 10 times bigger than the source impedance. In my case it's totally other way around. I'm still getting pretty loud sound, but I wonder if I get the amp that has higher input impedance, would that improve sound? Add more clarity?



Thanks!

While it's generally accepted that if you set a Impedance Buffer Preamp. like the Headway EDB-2 or FDeck HPF Pre to 10 Meghoms. Then just about any pickup will sound it's best, I found that the with the Realist I preffered the 5Meg Ohm setting. Just my take

 

[darksail]

Hello, I am using a realist by a decade to amplify my double bass, I love It, never had a problem.
Today I Just received a new "micro" combo, this One:
Phil Jones Bass Combo M-7 – Thomann Italia
It's a Phil Jones m7.
(Impedance 8 ohm)

I plugged my realist directly into the amp and, It does not work at all... No sound, nothing!

I've checked the cable and It was ok. Then I've connected a bass Guitar and It worked properly, so the problem is strictly related to my realist.

Do I maybe Need of a preamp? Any your suggestions is really appreciated.
Thanks,
Emiliano.

 

[Ric Vice]

The Phil Jones does not have an 8 Ohm input impedance. That is the impedance of the amplifier out to the speaker. Although I cannot tell from the PJB website,

the Majority of Phil Jones Amplifiers are set at 4.6 ohms, which is really great for Double Bass pickups. I think your pickup may have a broken lead, into the piezo element.

If that's the case, it cannot be repaired as far as I know. It's possible that the 1/4" jack has a broken lead wire inside, which could possibly be repaired.

 

[darksail]

think your pickup may have a broken lead, into the piezo element.

If that's the case, it cannot be repaired as far as I know. It's possible that the 1/4" jack has a broken lead wire inside, which could possibly be repaired.

Thanks Ric for your reply but... I'm using my realist with another combo and It works fine.

 

[Wasnex]

Hello, I am using a realist by a decade to amplify my double bass, I love It, never had a problem.
Today I Just received a new "micro" combo, this One:
Phil Jones Bass Combo M-7 – Thomann Italia
It's a Phil Jones m7.
(Impedance 8 ohm)

I plugged my realist directly into the amp and, It does not work at all... No sound, nothing!

I've checked the cable and It was ok. Then I've connected a bass Guitar and It worked properly, so the problem is strictly related to my realist.

Do I maybe Need of a preamp? Any your suggestions is really appreciated.
Thanks,
Emiliano.

The input impedance is a bit low.

From the Micro 7 manual:

Impedance
High Input: >500KΩ/22pF
Low Input: >30KΩ/22pF​

The High (sensitivity) Input would be best. If there is absolutely no sound I would check the Realist with another amp, as they sometimes go bad.

It's likely a buffer would improve the sound. An HPF Buffer from @fdeck would probably be ideal, but confirm your pickup works first.

Broughton will make an HFP with custom input impedance as well. https://www.broughtonaudio.com/product-page/always-on-high-pass-filter

 

[darksail]

Thanks Wasnex.
Yes, tested with my Combo Markacoustic and realist is ok. No surprises.
Yes, when I plug the realist into the PJ there is no sound at all.

 

[Wasnex]

Thanks Wasnex.
Yes, tested with my Combo Markacoustic and realist is ok. No surprises.
Yes, when I plug the realist into the PJ there is no sound at all.

???? That's seems very strange. AFAIK low impedance will make a piezo sound bad, not make it totally silent. The output of a piezo should be similar to a passive bass guitar.

You are using the same 1/4" instrument cord with both amps and both basses?

 

[darksail]

You are using the same 1/4" instrument cord with both amps and both basses?

Yes.
I wrote to PJB and realist guys to ask info too...

 

[DoubleMIDI]

If it‘s 30 KOhms, then no sound (or a very thin chirp) is totally possible for a Realist.
500 KOhms are not the best, but at least something a bit unpleasant to hear should go out.

The old PolyTone Mini-Brutes were 330 KOhms, and I think most MarkBass amps are 500 KOhms.

 

[darksail]

Thanks Double Midi.
Realist directly to Markacoustic AC121 model (it's what I have) sounds very good imho. (It should have IMPEDANCE
8 ohms)

These are instead the specs of the PJB:

 

[Ric Vice]

Why any company would put out a bass amplifier, with input impedances that low puzzles me as it makes the amp totally unusable for a Double Bass fitted with a piezo pickup. Dark sail, once again, just for clarification, the input impedance of your amplifier is not 8 Ohms. That’s the operating impedance of your amplifier’s output and speaker.

 

[darksail]

I trust you completelly!
But I still don't understand how to solve my problem. (I can send back the amp, it's an option ... )

 

[Don Hergert]

I can send back the amp, it's an option ...

I'd first suggest trying the amp out with another instrument that is known to work, preferably a friend's double bass that uses the same pickup you use (I know, that's hard to do). If it works with that, at least you know it's not your combo amp.

Could you be having trouble with a high-impedance cable?

 

[darksail]

Just made a couple of tests:
1) I used a bass max pickup. The result is the same but, if I tap on the piezo with my fingers, I can hear something exiting by the PJ. (The noise of the tapping).
No music at all if I use the bass max as It must be used.

2) put a Little mixer in the chain, between the realist and the PJ.
The mixer shows signal, but the amp does not play any sounds.

I think that next day PJ or Realist site Will answer to me, and clarify the situation.

@dhergert: I do not know about High impedance cables, thanks, I Will investigate

 

[Wasnex]

Just made a couple of tests:
1) I used a bass max pickup. The result is the same but, if I tap on the piezo with my fingers, I can hear something exiting by the PJ. (The noise of the tapping).
No music at all if I use the bass max as It must be used.

2) put a Little mixer in the chain, between the realist and the PJ.
The mixer shows signal, but the amp does not play any sounds.

I think that next day PJ or Realist site Will answer to me, and clarify the situation.

@dhergert: I do not know about High impedance cables, thanks, I Will investigate

If you put a mixer between the pickup and amp and you still do not get sound, the mixer serves as a buffer so the problem is not impedance. Can you monitor the sound from the mixer with headphones to make sure it sound good? The input impedance of the mixer is problem to low as well, but I think we have shown the problem is either with the amp or your cable.



Does your 1/4" plug look like this?

It should look like this.

 

[darksail]

II Wil check again with the mix/headphones.
The cables have just one Black circle. This is the cable :

 

[dreamadream99]

I have never had a problem running my Realist straight into a Gallien-Krueger or Acoustic Image amp.

I have, however, had problems running it into almost every other amp with standard impedance. They all sounded tinny, with an over-abundance of treble and no discernible bass, so profound that it could not be EQ’d out. The only thing that ever fixed that for me, was the Fishman Platinum Pro Bass EQ (version 1), an active DI/preamp with an impedance matching transformer.

 

[Don Hergert]

/

II Wil check again with the mix/headphones.
The cables have just one Black circle. This is the cable :

What does the printing say on the cable end that doesn't say D'Addario on it? I'm concerned that it may say "Balanced End", which would mean this is a balanced cable, not what you want.

Even if it doesn't say that, I'd still suggest further testing of this cable, or better, try a different, more standard guitar cable.

If that's the only cable you have, you might want to test the cable with another amp.

I use one of these:
Invalid Link Removed
Similar units are also available from a number of different companies.

In my experience, these also do impedance bridging and balanced cable conversion. I use one for connecting my DB's mounted mic to my combo amplifier (Roland), and it makes it so I do not need a pre-amp with that mic. I can also use it with my piezos which do have a mounted pre-amp, and it just adds to the available headroom.

 

[DoubleMIDI]

...
The only thing that ever fixed that for me, was the Fishman Platinum Pro Bass EQ (version 1), an active DI/preamp with an impedance matching transformer.

If there is a transformer, it is not used for the input. If there is a DI out it would be used to decouple the board from the stage electronics. If not it might be used for the output.

A transformer never gets close enough the high impedance needed for a piezo.
The ones you can get separately are meant to convert between mic (600 Ohms) to line (about 10 KOhms or a bit more). Not suitable to connect to a passive piezo output.

 

[DoubleMIDI]

II Wil check again with the mix/headphones.
The cables have just one Black circle. This is the cable :

On one jack there is hardly readable „shielded end“.

Since both jacks are TS, it cannot be a balanced cable.

But what about the other end? Is the shield not connected there? It would be a good idea to use a standard cable, even a cheap one can do for testing, and use a multimeter to check pin to pin and shield to shield connections.