Input sensitivity and type of inputs

[Codifus]

Here's a question that I've been scratching my head for a while now.
I have a Beresford DAC, the TC-7520. I found out that it has an output thru its pre-amp RCA jacks of 2V rms.

I used to own the Behringer A500 amp. It has an input sensitivity of 1.64 V, with 10kohms unbalanced and 20kohms balanced.

I connected my DAC to the A500 in 2 ways, using the RCA inputs or the 1/4 inputs on the A500.

When I used the RCA input on the A500, the system sounded stronger, punchier.

When I used the 1/4 input on the A500, the system sounded less dynamic.


Of course I used different cables, but the difference should not have been so pronounced. I used either the standard RCA to RCA left and right cables, like this:

http://accessories.musiciansfriend.com/product/AV-Link-Dual-RCARCA-Cable?sku=339008

Or, i used the RCA to 1/4" cable, this one:
http://accessories.musiciansfriend.com/product/AV-Link-Dual-RCA-14-Cable?sku=339009

My question is, why? Was the Behringer using a higher resistance with the 1/4 connection because it assumes that the connection is balanced?

The reason I ask this is because I'm getting another amp and I want to avoid getting an s-convert if I don't have to.

Thanks

CD

 

[bandphan]

you answered your question there within balanced v unbalanced and it was just louder or 11 as we say

 

[WaynePflughaupt]

You were using unbalanced connections either way, so there shouldn’t have been a difference. Did you level-match the two connection options before listening, to remove "improvement" often perceived when one is louder than the other?

I don’t see how adding a level booster is going to help the problem you’re hearing.

Regards,
Wayne A. Pflughaupt

 

[highfigh]

Here's a question that I've been scratching my head for a while now.
I have a Beresford DAC, the TC-7520. I found out that it has an output thru its pre-amp RCA jacks of 2V rms.

I used to own the Behringer A500 amp. It has an input sensitivity of 1.64 V, with 10kohms unbalanced and 20kohms balanced.

I connected my DAC to the A500 in 2 ways, using the RCA inputs or the 1/4 inputs on the A500.

When I used the RCA input on the A500, the system sounded stronger, punchier.

When I used the 1/4 input on the A500, the system sounded less dynamic.


Of course I used different cables, but the difference should not have been so pronounced. I used either the standard RCA to RCA left and right cables, like this:

http://accessories.musiciansfriend.com/product/AV-Link-Dual-RCARCA-Cable?sku=339008

Or, i used the RCA to 1/4" cable, this one:
http://accessories.musiciansfriend.com/product/AV-Link-Dual-RCA-14-Cable?sku=339009

My question is, why? Was the Behringer using a higher resistance with the 1/4 connection because it assumes that the connection is balanced?

The reason I ask this is because I'm getting another amp and I want to avoid getting an s-convert if I don't have to.

Thanks

CD

Read your manual- it's explained there.

You have a piece of equipment that's called 'Prosumer'. Not completely Professional and not completely consumer grade, but it will work for both. The signal levels and impedance in pro audio and consumer aren't the same. You can make the connections but if you use the balanced low impedance inputs, it's not the correct way to connect the preamp and power amp. How did you make the connections on whatever plug you connected at the amp? RCA-1/4"? That should have worked but you're still going into a low impedance input and that's a mismatch. Keep the high impedance sources connected to high impedance inputs.

 

[Codifus]

You were using unbalanced connections either way, so there shouldn’t have been a difference. Did you level-match the two connection options before listening, to remove "improvement" often perceived when one is louder than the other?

I don’t see how adding a level booster is going to help the problem you’re hearing.

Regards,
Wayne A. Pflughaupt

I didn't do a level match but I was under the impression, after looking through the manual, that the unit can accept balanced and unbalanced signals on either input and adjust itself accordingly.

I will just go with the assumption from now on that 1/4" inputs assumes balanced.

Thanks

CD

 

[highfigh]

I didn't do a level match but I was under the impression, after looking through the manual, that the unit can accept balanced and unbalanced signals on either input and adjust itself accordingly.

I will just go with the assumption from now on that 1/4" inputs assumes balanced.

Thanks

CD

The 1/4" jacks are TRS and balanced- Tip, Ring and Sleeve. That means the tip is hot (Pin 2, non-inverted), ring is cold (Pin 3, inverted) and the sleeve is ground (Pin 1). Using a 1/4" mono plug (Tip, Sleeve) will combine the ring and sleeve, which is fine for using an unbalanced source. The only jacks that are really unbalanced are the RCA.

 

[Codifus]

The 1/4" jacks are TRS and balanced- Tip, Ring and Sleeve. That means the tip is hot (Pin 2, non-inverted), ring is cold (Pin 3, inverted) and the sleeve is ground (Pin 1). Using a 1/4" mono plug (Tip, Sleeve) will combine the ring and sleeve, which is fine for using an unbalanced source. The only jacks that are really unbalanced are the RCA.

Sorry, I wasn't clear. When I said balanced I was thinking more in terms of input sensitivity. Even though the 1/4" input can be balanced or un-balanced, the input sensitivity always stays in "balanced" mode, so to speak. Whether the signal is balanced or unbalanced, the input sensitivity, no matter what, remains at 20 kohms.

CD

 

[WaynePflughaupt]

I didn't do a level match but I was under the impression, after looking through the manual, that the unit can accept balanced and unbalanced signals on either input and adjust itself accordingly.

Well, the RCA inputs for sure can’t accept a balanced signal.

Sorry, I wasn't clear. When I said balanced I was thinking more in terms of input sensitivity. Even though the 1/4" input can be balanced or un-balanced, the input sensitivity always stays in "balanced" mode, so to speak. Whether the signal is balanced or unbalanced, the input sensitivity, no matter what, remains at 20 kohms.

Input sensitivity has to do with the voltage level of the signal. That’s a separate issue from input impedance.

Typically a pro amp will be looking for a hotter signal from its balanced inputs, but will automatically adjust its sensitivity “requirements” if you will, when an unbalanced signal is fed to the 1/4” inputs via a TS plug. So to answer your original question...

When I used the RCA input on the A500, the system sounded stronger, punchier.

When I used the 1/4 input on the A500, the system sounded less dynamic.

My question is, why? Was the Behringer using a higher resistance with the 1/4 connection because it assumes that the connection is balanced?

...If you saw a drop in output when you switched from the RCAs to the 1/4”, then it appears that this amp doesn’t do the usual auto-detect, and if that’s the case the gains would have to be re-adjusted. Only a level-matched comparison between the two would be a valid comparison; otherwise the ear is easily fooled into thinking that the louder one is better.

Regards,
Wayne A. Pflughaupt

 

[Codifus]

.......If you saw a drop in output when you switched from the RCAs to the 1/4”, then it appears that this amp doesn’t do the usual auto-detect, and if that’s the case the gains would have to be re-adjusted. Only a level-matched comparison between the two would be a valid comparison; otherwise the ear is easily fooled into thinking that the louder one is better.

Regards,
Wayne A. Pflughaupt

I believe that that is exactly the case here. My observations were not only that the RCA connection was louder, which it was, but it was also more dynamic. The difference between the loud and soft passages was more dramatic with the RCAs. For both connections I left the amps gain set at maximum.

CD