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Old 19th February 2015, 01:31 PM   #1
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Location: Germany,17039 Wulkenzin OT Neuendorf
Smile Too much signal voltage...

Hello from germany!

I have a problem with a new old device: Ultramatch Pro from Behringer...
This is certainly a studio device that has to be configured for home use.
My setup: iMac or satelite radio as source into Ultramatch into either hybridamp for Stax 404 or el84 tube amp for speakers...
My problem is that the Ultramatch has too much analog signal output!
So, using the attenuater for the tube amp or the attenuater of the Stax hybrid amp gives me no convienient room for adjustment..

My question is: How do I decrease the output voltage to normal 2V?
Some kind of pad? Built into the signal cable? Symmetrical?
The Ultramatch has symmetrical analog XLR outputs...
The Hybrid has symmetrical analog inputs...

I have seen some calculators for such experiments, but honestly, I give up reading how i is done...

I do have some information maybe interesting for the resistor choosing...

Output impedance is 160 Ohm
Output level is +16 dBu bei 0 dBFS

Hopefully to hear from somebody with knowledge in this case... I have near to some...
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Old 19th February 2015, 06:02 PM   #2
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This might serve your need. Add a dropping resistor as shown.

The added resistor doesn't have to be directly at the volume pot, it could also be at the other end of the conductor connecting to the pot--or you could even cut a wire and solder in the resistor. Just be sure the added resistor is on the input side of the pot, so excessive voltage is dropped before it gets to the pot's wiper.

The values shown in the illustration are only representative, you'll have to guesstimate what you actually need. For your case maybe the dropping resistor might be the same value as the pot. Remember that if the first resistor you add is too large, then you can add a second resistor in parallel.
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Last edited by bentsnake; 19th February 2015 at 06:12 PM.
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Old 19th February 2015, 06:25 PM   #3
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Hi, this is a great idea! I will soon try it out... First I will search for an adequate resistor in my stock...

Thanks!
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Old 19th February 2015, 07:09 PM   #4
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Just to be sure: most Behringer equipment has little switches on the back side to switch between +4 dBu and -10 dBV nominal line level. Are you sure there is no such switch?
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Old 19th February 2015, 07:59 PM   #5
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Hello, Marcel, mine does not have such a switch...I think the former model had one...
Now I have a 470K on both signals...and works very good!
Thankyou also bentsnake for making me happy!
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Old 20th February 2015, 01:40 AM   #6
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You're welcome, glad I could help out a bit.
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Old 21st February 2015, 10:32 AM   #7
forr is offline forr  France
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Quote:
Originally Posted by hifisucks View Post
Hello from germany!

I have a problem with a new old device: Ultramatch Pro from Behringer...
This is certainly a studio device that has to be configured for home use.
My setup: iMac or satelite radio as source into Ultramatch into either hybridamp for Stax 404 or el84 tube amp for speakers...
My problem is that the Ultramatch has too much analog signal output!
So, using the attenuater for the tube amp or the attenuater of the Stax hybrid amp gives me no convienient room for adjustment..

My question is: How do I decrease the output voltage to normal 2V?
Some kind of pad? Built into the signal cable? Symmetrical?
The Ultramatch has symmetrical analog XLR outputs...
The Hybrid has symmetrical analog inputs...

I have seen some calculators for such experiments, but honestly, I give up reading how i is done...

I do have some information maybe interesting for the resistor choosing...

Output impedance is 160 Ohm
Output level is +16 dBu bei 0 dBFS

Hopefully to hear from somebody with knowledge in this case... I have near to some...
Hi Hifisuck,

The Ultramatch user's manual shows how to connect the balanced output to an unbalanced amp.

16 dBu for 0 dBfs means a maximal voltage output of 4.9 Vrms.

To get a level of 2 V, you effectively need an attenuator.
This may be made using two resistors.

Albeit not perfect, a circuit using a resistor in series with a pot may fit your needs if you intend to use this pot as a volume control.
Ideally, the value of this pot should be low.

This is one of the rare 1 kOhm stereo log pot I could find :

PO6S-LIN 1,0K: Drehpoti. linear, 6mm, stereo 1,0 k-Ohm bei reichelt elektronik

Adding a 1.5 kOhm in series with this pot as shown by Bentsnake and the output at the cursor will limit the maximum voltage at the cursor to 2 Vrms.

If you do not intend to use a volume pot at the Ultramatch output, insert an attenuator, its values could be 470 and 330 Ohm.
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Old 21st February 2015, 11:43 AM   #8
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Hi forr, I do have an attenuator after the Ulcermatch...100K... just for the No. 1, inside the aluminum box...
Now I found out, that when I put a 330K to 470K on both channels I arrive at my goal!
Thankyou!

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Last edited by hifisucks; 21st February 2015 at 11:52 AM.
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Old 21st February 2015, 12:09 PM   #9
forr is offline forr  France
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Quote:
Originally Posted by hifisucks View Post
Now I found out, that when I put a 330K to 470K on both channels I arrive at my goal!
4.7 kOhm, 3.3kOhm should be better. 470 Ohm, 330 Ohm even more.
Less noise, less crosstalk, less susceptibility to parasitics.
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Old 21st February 2015, 02:36 PM   #10
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This doesnt work... You may have missed that I have a 100K Alps pot...so, 4.7K Ohm does nothing...
390K is perfect now!
Thanks...
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