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Offline Lotuswins

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Benedini Mini and volume control with 9x pot?
« on: April 09, 2018, 10:36:46 PM »
Hi Luke,

So I have my T55A working great with the TCB, and the Taigen sound card, but its spitting out the PIV sounds (....that is all I know of that they have right now). 

I just rec'd the Benedini Mini with the T55A sounds set up for the TCB, and I read that a 3 position switch is needed to control the volume.  Since the 3 position switch on my 9X turnigy is already reserved for engine start/stop....as it is on all of my tanks....is it possible to control the mini sound volume using one of the pots??  Can you recommend how to set that up? 

thanks for any help,  Jerry

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Offline LukeZ

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Re: Benedini Mini and volume control with 9x pot?
« Reply #1 on: April 10, 2018, 12:10:48 AM »
Sadly that is not an option with Benedini's products. I asked him to consider it once but I think it would have come at the expense of other functions more important. In any event, the present system using a switch is the only way to achieve volume control, this is true regardless of whether you use the Mini with the TCB or on its own.
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Offline Lotuswins

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Re: Benedini Mini and volume control with 9x pot?
« Reply #2 on: April 10, 2018, 12:58:03 AM »
Can I 'simulate' a switch with the pot??  low (zero) ohms, position 1, and high (100k) as position 3, mid level, mid position?

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Offline LukeZ

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Re: Benedini Mini and volume control with 9x pot?
« Reply #3 on: April 10, 2018, 02:19:37 AM »
Yes of course, you can use a "pot" channel as a "switch" channel and the functionality will be the same. When you move the pot all the way to one extreme it will be as if you had put the switch to one position, and at the other extreme the other position. You will not be able to adjust the volume exactly according to the position of the "pot" as you had in mind originally, but if the only physical control you have left is a pot then you can assign it to these functions and it actuate it as if it were a switch.
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Offline Rad_Schuhart

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Re: Benedini Mini and volume control with 9x pot?
« Reply #4 on: April 10, 2018, 09:33:30 AM »
Hi, I did something similar with the benedini micro. With a pot in the minimum position the volume lowers slowly until is completely muted, and at maximum position keeps rising until maximum volume.

You dont need a 3 pos switch, you can do it with any switch in you radio, but if you dont have a heavily modded 9x using a pot is a great idea.

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Offline Shorty54

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Re: Benedini Mini and volume control with 9x pot?
« Reply #5 on: April 10, 2018, 12:28:42 PM »
Thanks for the info guys, as I was wanting to adjust volume with the pots also.
I will give it a try.

Shad

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Offline Lotuswins

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Re: Benedini Mini and volume control with 9x pot?
« Reply #6 on: April 12, 2018, 11:18:34 PM »
Hi Luke,

So I use channel 7 on the 9x for volume, Pot #2, and I setup the TCB with Channel 7 as Aux 3, digital 3 position switch.  Function setup is: Position one is start raising volume, position two is stop volume, and three is start decreasing volume.   It works a treat.

A side question on the Benedini though, I purchased some very small rectangular speakers in 8 ohm impedance, and hooked it up today.  The volume is very low compared to others on 4 ohm speakers like the Taigen sound card.  Same size speaker, just different impedance.  Will I smoke the Benedini with a lower impedance speaker??  It does look rather delicate....

thanks,  Jerry

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Offline LukeZ

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Re: Benedini Mini and volume control with 9x pot?
« Reply #7 on: April 13, 2018, 12:43:04 AM »
So I use channel 7 on the 9x for volume, Pot #2, and I setup the TCB with Channel 7 as Aux 3, digital 3 position switch.  Function setup is: Position one is start raising volume, position two is stop volume, and three is start decreasing volume.   It works a treat.

Thanks for reporting back. In this case we are still using a 3 position switch so far as the TCB knows, but in reality you have a pot as the actual control. It is good to remember the user is free to assign a variable ("analog") physical control as a digital switch in OP Config, and vice-versa, the suggestions are not hard and fast rules. However there is not often a need to do so, but this is an example of a time where it makes sense.


A side question on the Benedini though, I purchased some very small rectangular speakers in 8 ohm impedance, and hooked it up today.  The volume is very low compared to others on 4 ohm speakers like the Taigen sound card.  Same size speaker, just different impedance.  Will I smoke the Benedini with a lower impedance speaker??  It does look rather delicate....

Actually, according to this user who contacted Thomas about speaker impedance, the Mini should only be used with 8 ohm speakers (directly, if you use an external amplifier with the Mini then that may not be a limitation). All else being equal, a 4 ohm speaker will draw twice the current of an 8 ohm speaker, so yes, it would seem 4 ohm speakers may risk damage to your Mini.

I've been using an old Heng Long speaker on my Mini for years, I don't remember where exactly I got it. But it measures 8 ohms so apparently they do exist from the standard manufacturers. It was probably from an old RX18. However like you I measure a more recent Taigen speaker to be 4 ohms.
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Offline Lotuswins

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Re: Benedini Mini and volume control with 9x pot?
« Reply #8 on: April 13, 2018, 04:16:21 PM »
Hi again,

So I looked at the details of the Mini, and it has a whopping 1.2 watts output?   Wow, how are you satisfied with that volume...w/o an amplifier?? I don't know what the HL or Taigen outputs are, but surely it must be at least double this?? 

So it looks like an amp is in my future.....

Jerry

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Offline LukeZ

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Re: Benedini Mini and volume control with 9x pot?
« Reply #9 on: April 13, 2018, 04:46:54 PM »
I guess each user is different. Personally I don't care for sound to begin with and the only time I've used the Mini or even my own sound card is for testing, and then at reduced volume.

However I will say that with the correct speaker (such as my 8 ohm Heng Long or a Visaton) the Mini can get surprisingly loud. I think it is every bit as loud as stock Taigen/Heng Long/Tamiya.

But yes, 1.2 watts is not very much. I thought I would get ahead of the curve and my original sound card prototype implemented a 2.6 watt amplifer (and was compatible with 4 ohm speakers). People complained and said it needed way more. Already my ears were bleeding. The new design I'm working on now has 10 watts but it amplifies sound so much any dead space in a sound file comes across as a very loud hiss, and it picks up any stray signal or interference and has become nearly impossible to get a clean output from... I don't blame Thomas for sticking with the low watt design!
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Offline Lotuswins

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Re: Benedini Mini and volume control with 9x pot?
« Reply #10 on: April 15, 2018, 01:01:23 PM »
Hi Luke,

So I went trolling for a amall, mono amplifier, and not liking the Benedini options, found this 2.5W model:

https://www.adafruit.com/product/2130?gclid=EAIaIQobChMI6efijeu82gIVDlmGCh0FTwlUEAQYASABEgKdn_D_BwE

The question is how to connect it to the Benedini Mini....I see in the Mini manual that he recommends a 220 ohm resistor in series with a 220 pot from Negative speaker out to ground, and the output is the wiper of the pot and ground.  This kinda seems wierd to me, and I would have to hang the pot and resistor somewhere.  I really would like a much cleaner approach.

I was planning on powering it with the 5.5v BEC off the TBS, so that would go to 2-5VDC and GND on the amp.  The two outputs from the Mini go to the A Plus and A Minus on the board input, and of course I would install a JST male on the board for the speaker to plug into (4 ohms works on this too).  Since A+ and A- are fully differential, it should work?  What do you think?

Thanks, Jerry


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Offline LukeZ

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Re: Benedini Mini and volume control with 9x pot?
« Reply #11 on: April 15, 2018, 01:33:48 PM »
I was planning on powering it with the 5.5v BEC off the TBS, so that would go to 2-5VDC and GND on the amp.  The two outputs from the Mini go to the A Plus and A Minus on the board input, and of course I would install a JST male on the board for the speaker to plug into (4 ohms works on this too).  Since A+ and A- are fully differential, it should work?  What do you think?

I'm not an audio design expert and I don't know why Thomas recommends the hookup arrangement he does. What you suggest seems logical enough and you could try it, but to be safe you should ask Thomas first.

Let us know the results. That's a very inexpensive amp and if it made a noticeable difference without much hookup hassle people would be interested to know.
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Offline Lotuswins

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Re: Benedini Mini and volume control with 9x pot?
« Reply #12 on: April 15, 2018, 02:47:37 PM »
Thanks for the quick reply Luke. 

I just emailed Thomas, so we'll see what he recommends.

Also, as a side note on speakers, I have an old Heng Long KV1 that has remained pretty much stock and was a 2.7khz radio tank initially.  I measured the speaker DC resistance yesterday, and it is 6.5 ohms.   That is wierd.....oh, well.   It's too bulky for the T55A anyways (I would have to cut the speaker enclosure up to make it fit) but I thought it was interesting that its an in-between speaker.....

Jerry

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Online jhamm

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Re: Benedini Mini and volume control with 9x pot?
« Reply #13 on: April 16, 2018, 12:32:46 AM »
I measured the speaker DC resistance yesterday, and it is 6.5 ohms.   That is wierd.....oh, well. 

Hi,
the ohms what you measure is not the speaker impedance...
the speaker impedance is a measure of the resistance of a loudspeaker to alternating current.
this is usually the case at a frequency between 250 and 400 Hz.
what you have measured is the DC winding resistance of the speaker coil
but it is an indicator which impedance the speaker can probably have.
In your case, it seems like an 8 ohm speaker.



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Offline Rad_Schuhart

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Re: Benedini Mini and volume control with 9x pot?
« Reply #14 on: April 16, 2018, 07:54:59 AM »
I don´t have a benedini mini, but with a micro, the impedance is critic! I had a lot of 4ohm speakers of all sizes, ranging from very small and flat laptop speakers to a home cinema ones that I scavenged, and no one of them works well with the micro. No matter what I tried it was a no go for me.

Then I plugged an 8ohm 1w speaker, and sounded very good. Then I tried another 8ohm 1w speaker but bigger and the sound was even better.

So whatever you do, buy a 8ohm speaker. The bigger the speaker and the box, the better. In case you need more power, you can add an amp like this one: https://www.ebay.com/itm/XPT8871-DC-3V-3-7V-5V-Mono-5W-Mini-Amplifier-Board-Audio-Amp-Module-One-channel/322979591569?epid=560313104&hash=item4b33157591:g:1gsAAOSwgZ1XtGeb

Hope it helps... I am not expert and this is not based in any scientific knowlegde, those are just my experiments...

 

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