So, is it safe to surmise that if a preamp has two...

RE: So, is it safe to surmise that if a preamp has two..., posted on July 20, 2017 at 17:09:18
John Elison Audiophile Posts: 23900 Location: Central Kentucky Joined: December 20, 2000 Contributor Since: January 29, 2004	That's how I use my preamp's second output. It works just fine for me. Try yours and see how you like it. Good luck, John Elison

RE: So, is it safe to surmise that if a preamp has two..., posted on July 20, 2017 at 17:13:16
suretyguy Audiophile Posts: 3022 Location: western Missouri Joined: October 9, 2001	I'd consult the owner's manual or contact the manufacturer.

RE: So, is it safe to surmise that if a preamp has two..., posted on July 20, 2017 at 19:00:33
Kingshead Audiophile Posts: 574 Location: Florida Joined: September 14, 2016	Perfectly safe, it's also what I use mine for. Martin

That's what I do., posted on July 21, 2017 at 04:34:35
tketcham Audiophile Posts: 6701 Location: East of the 100th meridian USofA Joined: March 21, 2005 Contributor Since: October 1, 2005	Hi, popsy, I use the second pre-outs on my preamp to feed two powered subwoofers, one line to each sub. Tom

RE: So, is it safe to surmise that if a preamp has two..., posted on July 21, 2017 at 06:33:34
morricab Distributor or Rep Posts: 9180 Location: switzerland Joined: April 1, 2005	As long as the input impedance of the subs line level inputs is high. The reason is that both your amp and sub see the same output devices in the preamp and act as a voltage divider. If the sub has a low input impedance then this will load down the output of the preamp and might alter the frequency response and drive capability of the preamp.

RE: So, is it safe to surmise that if a preamp has two..., posted on July 21, 2017 at 06:56:42

kentaja
Manufacturer

Posts: 4614
Joined: March 26, 2001

If the preamp is solid state probably not an issue.

Tube preamps like a to see a higher impedance and most subs are quite low on their input impedance. Parallel that with the input impedance of the power amp and it drops even lower. Get it too low and this will have a tremendous impact on frequency response as well as dynamics, slam.

Find the spec. of your preamp to determine the lowest impedance it wants to see.

I would check if it's a fixed or variable output..., posted on July 21, 2017 at 08:28:06
GregK Audiophile Posts: 465 Location: NE Ohio Joined: September 30, 1999	...variable will allow you to change the volume... I've used the second output for my sub for years, both from my old preamp and my new integrated; specifically looked for one with a variable pre out...

RE: So, is it safe to surmise that if a preamp has two..., posted on July 21, 2017 at 08:43:41
BCR Audiophile Posts: 2446 Location: connecticut Joined: April 7, 2009	Same as using a y adapter. That's what I use and never a problem!

RE: So, is it safe to surmise that if a preamp has two..., posted on July 21, 2017 at 08:50:49
Palustris Audiophile Posts: 2408 Location: Cape Cod Joined: September 12, 2008	It's best to check the schematic for a technically accurate response.

Not necessarily, posted on July 21, 2017 at 09:07:23
cawson@onetel.com Audiophile Posts: 2381 Joined: September 27, 2004	Many preamps have a second output that doesn't go though the volume control. In the old days, this would probably be labelled as Tape Out, but many post-tape preamps also have a fixed (full) level output. Beware before you connect up

Thanks everyone! n/t., posted on July 21, 2017 at 23:07:36
popsy Audiophile Posts: 2713 Location: oregon Joined: March 4, 2007	n/t

RE: So, is it safe to surmise that if a preamp has two..., posted on July 22, 2017 at 08:01:45
tketcham Audiophile Posts: 6701 Location: East of the 100th meridian USofA Joined: March 21, 2005 Contributor Since: October 1, 2005	Hi, kentaja, How do you determine the overall input impedance if the preamp is seeing two powered subwoofers connected to one pre-out connection and a main power amp connected to the other pre-out connection? I have a tubed preamp with this setup and although the sound seems pretty darn good, I'd be interested in knowing if the preamp might be operating in the "red" zone. Regards, Tom

RE: So, is it safe to surmise that if a preamp has two..., posted on July 22, 2017 at 09:46:51

kentaja
Manufacturer

Posts: 4614
Joined: March 26, 2001

You will need to know the input impedance of the power amp and sub woofer.

Once you know both numbers you can find an on-line calculator to determine the effective impedance of the two in parallel.

If you have a tube preamp it is probably not going to work. You need to know the lowest load the preamp will tolerate and still have good sound.

RE: So, is it safe to surmise that if a preamp has two..., posted on July 22, 2017 at 12:25:57

John Elison
Audiophile

Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
Since: January 29, 2004

Actually, all you have to do is try it. If your preamp has two main outputs, it is obviously designed for connecting two amplifiers. I have a Vacuum Tube Audio SP14 Preamp and mine works just fine with my Parasound Halo A21 amplifier connected to one set of outputs and my two Rythmik powered subwoofers connected to the other set of outputs.

All you have to do is try it because you can't hurt anything by trying it. If it sounds fine then you're good to go.

Good luck,
John Elison

.
.

RE: So, is it safe to surmise that if a preamp has two..., posted on July 22, 2017 at 19:37:18

tketcham
Audiophile

Posts: 6701
Location: East of the 100th meridian USofA
Joined: March 21, 2005
Contributor
Since: October 1, 2005

Hi, John,

My setup is basically the same configuration and I've been enjoying it for a few months now. I was just wondering how far into the conventional warning zone, i.e., less than a 1:10 ratio of output impedance to input impedance, I'm operating the preamp. I tried using a tubed buffer stage to effectively lower the output impedance but I didn't like the resulting sound.

Guess I'll just keep on listening to what I have set up and enjoy the music. '-)

Regards,
Tom

RE: So, is it safe to surmise that if a preamp has two..., posted on July 22, 2017 at 19:44:38
tketcham Audiophile Posts: 6701 Location: East of the 100th meridian USofA Joined: March 21, 2005 Contributor Since: October 1, 2005	Thanks. I have an online calculator I can use once I get the specs for the onboard power amps of the subwoofers. I already have everything set up so at this point it may be moot as to whether it should work or not. It does work, and seems to be working quite well. But I'm curious as to how far into the 1:10 buffer I'm running the preamp. Tom

RE: So, is it safe to surmise that if a preamp has two..., posted on July 22, 2017 at 20:37:56

kentaja
Manufacturer

Posts: 4614
Joined: March 26, 2001

Just because you have a preamp with two outputs does mean you can hook up any old thing to those outputs. One must be careful with the actual load the preamp will see. This is not rocket science just basic electronics. Drop the load below what the preamp wants to see and the sound will be degraded pretty dramatically. If one likes the bad sound so be it.

Solid state preamps are far more flexible in this regard than tube preamps.

RE: So, is it safe to surmise that if a preamp has two..., posted on July 22, 2017 at 20:48:36

John Elison
Audiophile

Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
Since: January 29, 2004

> Drop the load below what the preamp wants to see and the sound will be degraded pretty dramatically.

I don't know why you're arguing with me. I understand electronics, too. I was an electronic technician for years. There is no way you will hurt anything by connecting two amplifiers in parallel to your preamp outputs. If you take the time to read what I wrote you would see that I said exactly what you just said, only in reverse. In other words, I said to try it and see how it sounds. If it sounds good then you're good to go.

My tube preamp sounds great connecting an amplifier and two subwoofers to both sets of preamp outputs.

Try it and find out how it sounds. You can't possibly hurt anything.

RE: So, is it safe to surmise that if a preamp has two..., posted on July 23, 2017 at 05:36:59
kentaja Manufacturer Posts: 4614 Joined: March 26, 2001	Agreed. It is not going to hurt anything to hook it up.

RE: So, is it safe to surmise that if a preamp has two..., posted on July 23, 2017 at 07:24:02

SpotcheckBilly12345

I have a Rogue Audio Cronus Magnum (tube) integrated amp with two preamp outputs. One of these outputs is fixed and the other is variable.

I occasionally hook up two powered subs through the variable preamp output jacks. This works fine for me and sounds great even though I don't know the impedances that are involved but I never even worried about it.

As John suggests, just hook them up and have a listen.

I'll betcha that it'll work well for you too and if it doesn't sound right you're not gonna hurt a thing by trying.

Cheers,
SB

good catch, posted on July 23, 2017 at 15:17:22
mbnx01 Audiophile Posts: 7956 Location: Eagle, Idaho Joined: October 22, 2004	Make sure both outputs are variable. And something else to look out for - if one is RCA and one is XLR they can't always be used at the same time. Or sometimes the RCA and XLR will have greatly different gain so matching the speaker and sub output can be tricky. 'A lie is halfway around the world before the truth gets its boots on'. -Mark Twain

RE: good catch, posted on July 23, 2017 at 15:50:23

tketcham
Audiophile

Posts: 6701
Location: East of the 100th meridian USofA
Joined: March 21, 2005
Contributor
Since: October 1, 2005

Hi, mbnx01,

Thank you both for pointing out some important stuff regarding subwoofer connections. Information like this is usually found in the owner's manual if you read it before connecting the item and using the stereo. But in our hurry to set up the shiny new component we sometimes miss something in the manual. Ask me how I know that. :-) Luckily most mistakes aren't serious and do no harm to the setup.

Regards,
Tom

Amp/Preamp Asylum

So, is it safe to surmise that if a preamp has two...

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