Receiver's pre-outs way TOO QUIET

BassFishing

Hey all,

I just got some RTA 15tl's for the fronts on my 7.2 system. Naturally, I'm in love. I decided to set these to large to team up with the powered subs (It's a big room-- 25 x 33, 12' ceilings). My Yamaha receiver HTR-6160 is decent, but I really want to make these speakers sing, and take some load off the receiver as well. So I pulled out a couple old amps (Hafler 120 watt/channel, Crown 300 watt/channel --both at 8 ohms) to use with my receiver's pre-outs to drive the 15tl's. Problem is, it's damn quiet. Way quieter than just keeping my fronts through the Yammie.

Just to test my amps, I ran a cd player straight into them. My 15tl's sounded great. So I called Yamaha and they said I need a a pre-amp between my yammie pre-outs and the power amp. This doesn't make sense to me--I thought the receiver was already a pre-amp, and the Crown and Hafler already have volume knobs on them. The crown even has two input levels settings in addition to the volume knob: 1.4 volts AND +28db. Neither are loud enough.

I've scoured the internet for info on receiver pre-outs--never saw anything about using a pre-amp before the power amp.

Thanks for all the help!

jinjuku

BassFishing wrote: »

Hey all,

I just got some RTA 15tl's for the fronts on my 7.2 system. Naturally, I'm in love. I decided to set these to large to team up with the powered subs (It's a big room-- 25 x 33, 12' ceilings). My Yamaha receiver HTR-6160 is decent, but I really want to make these speakers sing, and take some load off the receiver as well. So I pulled out a couple old amps (Hafler 120 watt/channel, Crown 300 watt/channel --both at 8 ohms) to use with my receiver's pre-outs to drive the 15tl's. Problem is, it's damn quiet. Way quieter than just keeping my fronts through the Yammie.

Just to test my amps, I ran a cd player straight into them. My 15tl's sounded great. So I called Yamaha and they said I need a a pre-amp between my yammie pre-outs and the power amp. This doesn't make sense to me--I thought the receiver was already a pre-amp, and the Crown and Hafler already have volume knobs on them. The crown even has two input levels settings in addition to the volume knob: 1.4 volts AND +28db. Neither are loud enough.

I've scoured the internet for info on receiver pre-outs--never saw anything about using a pre-amp before the power amp.

Thanks for all the help!

Pro amps require different input voltage and impedance. You may need to get an impedance transformer.

What are the exact model #'s on the amps?

ohskigod

you had the volume up on the amps? IF you havent, try just using the hafler on the mains and leave the crown out of the equation (drive the other channels with the Yammie.

let us know what happens

Polkie2009

I've got the exact same AVR and have used a couple of pro amps to run the srrounds(sides, Carvin,DCM 2000,yea,I know....but the amp sounds fine and takes everything dished out to it without breaking a sweat. The back surrounds are handled with a Crest Audio Professional 4000 amp(old ,but well respected in the industry) which also handles everything thrown at it. I do_ have to run cables with rca ends to AVR and 1/4 to amps. Both amps have attenuator controls turned all the way up. In your OSD menu, what are your volume settings for front,side surr.,center,back surr. etc... Depending how you set it up (I did mine with a db meter running 85 dbs on each speaker. The db display on front of AVR is running 0 db. YMMV

BassFishing

jinjuku wrote: »

Pro amps require different input voltage and impedance. You may need to get an impedance transformer.

What are the exact model #'s on the amps?

Hafler Pro 2400
Crown K1

BassFishing

ohskigod wrote: »

you had the volume up on the amps? IF you havent, try just using the hafler on the mains and leave the crown out of the equation (drive the other channels with the Yammie.

let us know what happens

I cranked the volume on both amps AND the Yammie. I only plan on using the front pre-outs, and will drive the other channels with the AVR. I only brought the Hafler out because I thought the Crown wasn't working. I'm surprised that the CD player sends a different voltage to the amp than the Yamaha does!

BassFishing

Polkie2009 wrote: »

I do_ have to run cables with rca ends to AVR and 1/4 to amps. Both amps have attenuator controls turned all the way up. In your OSD menu, what are your volume settings for front,side surr.,center,back surr. etc... Depending how you set it up (I did mine with a db meter running 85 dbs on each speaker. The db display on front of AVR is running 0 db. YMMV

I calibrated my system with a SPL meter at 75 db (i live in an apartment building, yikes!) I usually don't go past 15 db on the Yammie's front display. The system sounds great through the AVR, but I really want to put more power behind the 15tl's and give the receiver some breathing room.

I'm also using rca-to-1/4 cables and I turned up the attenuator controls when I tried Crown and when I tried the Hafler.

Do you have to use a pre-amp or impedence booster? What I don't understand is when I bypassed the HTR6160 and connected a CD player directly to the amps, they were loud with plenty of headroom. This tells me that the signal is stronger coming directly from the CD player rather than passing through the AVR first. But then that means the CD player's signal becomes diminished inside the Yamaha?

THANKS EVERYBODY FOR THE HELP SO FAR.

ohskigod

only other idea I have is to do the calibration manually to start, and jack up the DB's all around to max in the set up menu. see if it sounds more normal in terms of overall volume. if it dies, you can trim DB's per channel to calibrate from there and hopefully have a good result?

nguyendot

It's true, to get full power from pro amps you must provide additional voltage. This is normal as pro amps are generally driven from further away than home theater amps - higher voltage helps kill noise and drives the signal farther.

BassFishing

nguyendot wrote: »

It's true, to get full power from pro amps you must provide additional voltage. This is normal as pro amps are generally driven from further away than home theater amps - higher voltage helps kill noise and drives the signal farther.

Does this mean that the CD player supplied enough voltage but not the pre-outs of the Yamaha?

I looked up impedance transformer online, and am having trouble finding any good info. Does anyone know what voltage I need?

The Crown K1 has an input impedance of 20k ohms (balanced) and 10k ohms (unbalanced)

Hafler Pro 2400: input impedance: 47k ohms per phase (balanced) 47k ohms (unbalanced)
*also it states the Input Sensitivity is 2.25 volts (unbalanced) and 1.125 volts (balanced) BOTH AT 120 watts/channel at 8 ohms.

**Does using a pre-amp between AVR pre-outs and pro amp do the same thing as a voltage transformer? I can't find much info on these.

Thank you.

BassFishing

Does anyone know any brand names of any voltage transformers?
Bump?

Based on the manuals I checked I need to bump up the one volt from AVR PRE-outs to 2 volts, or 9 volts, depending on which power amp I use.

tonyb

Can't help ya there, but was curious as to why not just spend the money on the right amp to begin with ? A couple hundies can buy a decent 2 channel amp.

BassFishing

tonyb wrote: »

Can't help ya there, but was curious as to why not just spend the money on the right amp to begin with ? A couple hundies can buy a decent 2 channel amp.

I was hoping to use the Hafler or the Crown only because I already own them. They were a gift a few years back. I've read about people using both brands for HT, so I figured it would work. And still, the fact that a CD player connected directly to either amp sounds great, but the AVR pre-outs do not astounds me. I have been looking at Adcoms though, if I can't find a solution to this...

SuigintouEV

One of the reasons I prefer Marantz is that the pre-out jacks are always very high voltage.

You should look into a Samson S-Convert.

You did REcalibrate after installing the amp right? And set the amp gains to max (undesirable in a pro audio situation but no problem for home audio). What I think is happening is that you're not even sending the signal through the pre-outs right now. You might hear stuff, but that's purely electronic crosstalk! Make sure the L/R mains are set to preout!

Polkie2009

I think on these AVRs when you hook up an external amp to the pre/outs, they automatically bypass the internal amp and send the signal to the external amp. There's no menu setting to have to change. On the Crown amp he tried both input (sensitivity?) settings with no change. Sounds like he already tried turned up his speaker settings in the AVR menu.

BassFishing

Polkie2009 wrote: »

I think on these AVRs when you hook up an external amp to the pre/outs, they automatically bypass the internal amp and send the signal to the external amp. There's no menu setting to have to change. On the Crown amp he tried both input (sensitivity?) settings with no change. Sounds like he already tried turned up his speaker settings in the AVR menu.

That's correct. I did all this things, and I think it just comes down to the higher voltage input on the amps. So if an amp is 200 watts/channel, but requires a 9 volt input, and my AVR outputs a 1 volt signal, im not going to get the full power of the amp.

After a bunch of searching I've heard of two line level boosters. I'm looking into a Samson s convert and an ART Clean box, but I want to make sure these don't color the sound. If anyone has experience with these products or has another idea plead let me know. Thanks again for helping me stay afloat here!

Polkie2009

Lol, other than cranking the main speaker settings all the way up and lowering all other speaker settings in the AVR ,maybe you can find a happy medium? You may still have to run the master volume on the AVR up and over 0 db on the front display to get loud enough for you. Believe me, if you overload the input on the power amp you'll know it one way or another. I'm sure running any outboard device between preamp and power amp is going to color the sound even if it's not noticeable by ear. Just throwing this out there, I was wondering if you put a graphic eq between the two and set all faders at 0 but equally turned up each channel's gain ,if that would help boost the signal? Of course you would still have the internal eq in the AVR to do it's thing.

Polkie2009

Maybe the Samson S-Converter is the easiest fix for ya:) Saw one on Ebay for $30.00.

BassFishing

Polkie2009 wrote: »

Maybe the Samson S-Converter is the easiest fix for ya:) Saw one on Ebay for $30.00.

Sweet I appreciate it! I'll let u know what happens.

BassFishing

Well shucks all that research and I missed the Samson s convert on eBay. Someone used "buy it now" last night. I wonder if I got a stand alone pre-amp it would do the same job as a a Clean Box or Samson? I'm not sure if they actually boost the signal. I guess I'm gonna have to wait around til another voltage booster shows up. I'm surprised they don't manufacture them anymore. Yikes.

Polkie2009

Try posting in the "wanted" section of CP flea market:) A number of people have used these things to run a pro amp for their subwoofer at some time.Worth a try, also CL?

BassFishing

Hi everyone. Realized I never finished the story. I did purchase a Samson line level converter and it worked tremendously. I also learned that you can use a digital multi meter and an xlr female-to-female connector to test the voltage that your AVR sends in its pre-outs. https://www.google.com/search?q=how+to+measure+avr+signal+outputs+with+a+multimeter&ie=utf-8&oe=utf-8

My Yamaha was sending1.3 volts, and the Crown K1 amp needed to receive 7 volts of signal to push sound through my speakers. With the multimeter and the adjustable levels of the Samson I was able to precisely decide how much voltage I sent to the Crown. While I did finish my theater set up (it was for my workplace) and it was amazing, after a year I was hardly using it, and I actually found out last week that a co-worker gave the 15tl's to a higher up for his bachelor pad (bizarre and frustrating, I know). But in case someone in the future experiences the same problems, they can learn from all help I got. Also, wanted to thank polkie2009 and all you all chiming in and giving me a hand.

scotvl

Thanks for telling us what the resolution was and its funny you bumped this old thread, I was just reading a very good article about this earlier tonight. Here's a link to help anyone else out who might be mixing in some Pro equipment in their home setup.

hometheatershack.com/forums/home-theater-receivers-processors-amps/35677-gain-structure-home-theater-getting-most-pro-audio-equipment-your-system.html

Polkie2009

Great to hear back on this. I've followed Wayne P.'s post for what seems like decades on various forums. He's a super smart gearhead , respected musician and all around stand up guy. Plus he lives right here in Katy Tx.