Pro amp input level

[alexwakelin]

Not sure if this should go here or in DIY. I am using my Sony STR DG510 receiver to send LFE via the subwoofer output to a Gemini power amp. The gemini only has inputs for XLR and 1/4" TRS, so I purchased an RCA to TRS adapter from parts express. I think the output level from my receiver is too low for this amp.

According to my manuals:

Subwoofer output on my sony receiver is 2V @1k (I don't know what this means)

Input sensitivity on my amp is 0.83 Vrms

I have to turn up the amp half way before I get any sound from my subwoofer, any lower then that and the input light on the amp does not come on. At about 3/4 volume I get enough output from my subwoofer for my taste. The amp is rated for 750 watts at 4 ohms, so I don't think I should have to turn it up that much to get an acceptable volume output from it. Is is possible to damage the amp by using it in this manner? Do I need to purchase some type of pre-amp for it to be compatible with my receiver?

One last thought, I also tried turning up the subwoofer level all the way on my receiver, this helps, but not much.

 

[TLS Guy]

Not sure if this should go here or in DIY. I am using my Sony STR DG510 receiver to send LFE via the subwoofer output to a Gemini power amp. The gemini only has inputs for XLR and 1/4" TRS, so I purchased an RCA to TRS adapter from parts express. I think the output level from my receiver is too low for this amp.

According to my manuals:

Subwoofer output on my sony receiver is 2V @1k (I don't know what this means)

Input sensitivity on my amp is 0.83 Vrms

I have to turn up the amp half way before I get any sound from my subwoofer, any lower then that and the input light on the amp does not come on. At about 3/4 volume I get enough output from my subwoofer for my taste. The amp is rated for 750 watts at 4 ohms, so I don't think I should have to turn it up that much to get an acceptable volume output from it. Is is possible to damage the amp by using it in this manner? Do I need to purchase some type of pre-amp for it to be compatible with my receiver?

One last thought, I also tried turning up the subwoofer level all the way on my receiver, this helps, but not much.

No you are fine. Your Sony outputs 2 volts at full modulation, and yet your amp only needs 0.83 volts for full modulation.

Now volume controls are not linear but log, so your rig is operating just like I would expect.

Stop worrying, you will do no damage. This is an easy one, since you have no problem.

 

[alexwakelin]

Thanks for the reply, it still seems odd to me that the signal light on my amp doesn't even come on until it's at half volume. But, if I'm not going to damage anything and I get enough output at 3/4 volume I guess I'll leave it set up the way I have it.

 

[JCW]

Many times the 1/4" input and XLR input on a pro amp are different, as the result of balancing transformers on the XLR, as well as padding back the 1/4" input (not knowing exactly what is coming into it).

Are you taking an RCA out from your preamp into the line in or the XLR in on the power amp? If you are going into the line input, you could try taking an RCA output from your preamp to a "balanced" XLR input and that might wake your power amp up. As stated above, you're fine like your are, but I know how we all like the inputs to appear "equal and balanced" as far as knob controls, etc.

The problem here is that would cost a few dollars to do and if it sounds good now it's probably not worth it.

Enjoy,
John

 

[TLS Guy]

Many times the 1/4" input and XLR input on a pro amp are different, as the result of balancing transformers on the XLR, as well as padding back the 1/4" input (not knowing exactly what is coming into it).

Are you taking an RCA out from your preamp into the line in or the XLR in on the power amp? If you are going into the line input, you could try taking an RCA output from your preamp to a "balanced" XLR input and that might wake your power amp up. As stated above, you're fine like your are, but I know how we all like the inputs to appear "equal and balanced" as far as knob controls, etc.

The problem here is that would cost a few dollars to do and if it sounds good now it's probably not worth it.

Enjoy,
John

Not so! I went on the Gemini site and found that their amps are configured like most pro units these days.

This is the deal.

You can make a balanced 600 ohm connection to the XLR or the 1/4 jack if you use a stereo jack.

If you use a mono 1/4 inch jack it makes an unbalanced 1 K input impedance connection.

Now his receiver's output is unbalanced, so the most he could do, would be to "float" a line, and that would have no advantage over an unbalanced hook up. Putting a transformer at the output of his receiver to balance the line would be an unnecessary expense and just make for the possibility of low bass loss in the transformer.

As long as the OP is using an RCA to single tip (no ring) 1/4" jack he is making the correct terminations for his equipment. Making any other connection will not change the gain or "wake up" his amp, what ever that means.

 

[WmAx]

Frankly, despite what the amp 'specs' might say, it is not uncommon for the pre outs from a consumer device to not be sufficient to drive a pro device. You can of course turn the pro amp gains all the way up - but this will often lead to noise/hiss. So, try it.... and if you get noise.... you will need to use a line level conversion device that is designed to change the consumer level signal to a pro level one, such as an Art Cleanbox or the Rolls equivalent(which probably has a flatter LFE response).

-Chris

 

[TLS Guy]

Frankly, despite what the amp 'specs' might say, it is not uncommon for the pre outs from a consumer device to not be sufficient to drive a pro device. You can of course turn the pro amp gains all the way up - but this will often lead to noise/hiss. So, try it.... and if you get noise.... you will need to use a line level conversion device that is designed to change the consumer level signal to a pro level one, such as an Art Cleanbox or the Rolls equivalent(which probably has a flatter LFE response).

-Chris

His amp control is only 75% round the clock. His max modulation from his SONY is 2 Volt, I suspect that is with the LFE output set to maximum and the inputs fully loaded. If he does have hiss, which the OP did not complain of, then I would advance his LFE output first. His amp is below 1 volt sensitivity for full modulation, so I think it unlikely he would need to boost his LFE output. If he does, then the specs from Sony are just plain fiction.

 

[alexwakelin]

Thanks for all the informative replies. IIRC, this is what I purchased from parts express to go from the RCA subwoofer output on the receiver to the amp.

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=090-285

The subwoofer level on my receiver goes from -10 to +10 (I think those numbers are arbitrary, they don't represent actual dB), I currently have it set at +10. I'm not getting any audible hiss from the sub, even with the levels cranked on the amp/receiver.

Would either of these deveices be suitable for boosting the signal from the receiver to the power amp?

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=320-204
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=245-035

This can be had for pretty cheap on ebay as well:
http://www.behringer.com/EN/Products/MIC800.aspx

Here's my amp:
http://www.geminidj.com/gxa750.html
and the manual, it's the 750 watt model:
http://www.geminidj.com/product_manuals/gxa750_1600_man.pdf

I got a really good deal on this amp, I don't mind spending a few more $$ to set it up properly.

 

[TLS Guy]

Thanks for all the informative replies. IIRC, this is what I purchased from parts express to go from the RCA subwoofer output on the receiver to the amp.

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=090-285

The subwoofer level on my receiver goes from -10 to +10 (I think those numbers are arbitrary, they don't represent actual dB), I currently have it set at +10. I'm not getting any audible hiss from the sub, even with the levels cranked on the amp/receiver.

Would either of these deveices be suitable for boosting the signal from the receiver to the power amp?

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=320-204
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=245-035

This can be had for pretty cheap on ebay as well:
http://www.behringer.com/EN/Products/MIC800.aspx

Here's my amp:
http://www.geminidj.com/gxa750.html
and the manual, it's the 750 watt model:
http://www.geminidj.com/product_manuals/gxa750_1600_man.pdf

I got a really good deal on this amp, I don't mind spending a few more $$ to set it up properly.

Please stop worrying about a non problem. You have now answered an important question, you have satisfactory signal to noise, and your sub has adequate output plus reserve.

Now any amp is a quality spoiler to a degree, so adding a device you don't need makes no sense.

You system IS set up correctly, please enjoy the your system and your monetary investment, and stop looking for non existent problems.

The position of your volume controls is irrelevant with the data you have provided.

And by the way none of those devices you posted are suitable in any shape or form, and would produce horrid results if inserted in the signal chain. If you had inadequate signal to noise, which you don't, you would need a line level amp.

 

[ParadigmDawg]

TLS is likely correct but if you feel like you need something, it would be this, as explained by Chris.

http://www.sweetwater.com/store/detail/CleanBox/#anchor

I had to use the passive version to eliminate a ground loop issue that developed when I added a pro amp into my system.

 

[JCW]

TLS Guy, you left me no choice but to respond-

1) There are professional amps which have different line level (1/4") vs. XLR levels....keep reading...

2) Why not disagree and use your ninja powers to claim victory and not attempt to make everyone else appear to be an idiot

3) Sorry for using the term "waking up the amp". I should have known that was over your head. It means making the amp come alive earlier...as in more sensitive to the input.

Why can't people disagree and be courteous and at least somewhat nice?

 

[TLS Guy]

TLS Guy, you left me no choice but to respond-

1) There are professional amps which have different line level (1/4") vs. XLR levels....keep reading...

2) Why not disagree and use your ninja powers to claim victory and not attempt to make everyone else appear to be an idiot

3) Sorry for using the term "waking up the amp". I should have known that was over your head. It means making the amp come alive earlier...as in more sensitive to the input.

Why can't people disagree and be courteous and at least somewhat nice?

I don't think I possess any special Ninja powers. I do however apologize if I gave any offense to you.

Just one observation, when reviewing threads of technical questions from individuals just starting out, if they are getting good advice from other members, I stay out of the discussion. Only if I think they are receiving bad, incomplete or confusing advice do I enter the thread. I think this helps avoid confusion for those just starting out.

 

[JCW]

Thank you for the comment. I am new to this site and certainly I do not know all of the answers either. However, I have 30 years of experience in major concert sound systems (as in tri-amped rigs running over 5000 watts RMS), church installations and design, as well as studio engineering, and I've probably owned as many speakers and amps as anyone (that probably isn't a sign of competence, but of addiction).

I am here because I recently got back into some vintage gear and had some questions in that area. I had to post before I could post a WTB add in the classifieds. I will move on and do it elsewhere.

You are the man here and I greatly appreciate your apology. I'm out of here and sorry for getting upset.

Enjoy your site,

John

 

[alexwakelin]

I will likely leave my system the way it is for now, if it ain't broke don't fix it. But just one more question...let's say I purchased the clean box, how would the total volume output of my sub with and without compre? Would I get more output from my sub with the clean box, or would the amp just clip/distort sooner?