Some amps are prone to self oscillation when not properly loaded. This is not a universal receiver, this is a dedicated system designed for use with particular speakers. I thought it prudent for the diyaudio.com community to share a little more knowledge than is typically available at BestBuy or Radio Shack.
I have seen subs that tie the common shields of the line level inputs and the negative terminals of the speaker level inputs together. My Sunfire sub is this way. If a BTL amp was used into the speaker level inputs, it would fry.
Also, many third tier manufacturers may use the generic plate amplifiers, but I would bet that Sony has such large manufacturing capabilities that they would build their own amp in even their lowest models. Sony supplies many of the basic parts that other manufacturers use in building their products.
--David
I have seen subs that tie the common shields of the line level inputs and the negative terminals of the speaker level inputs together. My Sunfire sub is this way. If a BTL amp was used into the speaker level inputs, it would fry.
Also, many third tier manufacturers may use the generic plate amplifiers, but I would bet that Sony has such large manufacturing capabilities that they would build their own amp in even their lowest models. Sony supplies many of the basic parts that other manufacturers use in building their products.
--David
I'm with KC here, don't listen to this rubbish,
if you understood my post you wouldn't.
Simply discard your system subwoofer.
It was a reasonable point about grounds that
TBH I was too polite about without thinking.
The sub will be extremely likely to be fully isolated
and not remotely care about ground.
🙂 /sreten.
My advice is if it sounds complicated ignore it, they
are not making it simple and its not relevant.
Your "new" subwoofer will work fine on its own.
if you understood my post you wouldn't.
Simply discard your system subwoofer.
It was a reasonable point about grounds that
TBH I was too polite about without thinking.
The sub will be extremely likely to be fully isolated
and not remotely care about ground.
🙂 /sreten.
My advice is if it sounds complicated ignore it, they
are not making it simple and its not relevant.
Your "new" subwoofer will work fine on its own.
RobAche said:
I don't think it needs to be on a board, in fact that may cause some rattling if the sub tries to move around on it.
The idea is to try to keep the sub from moving around on its own, this would cause a cancellation and reduce the sub's output. I once successfully ran flat head wood screws through the carpet and into the flooring beneath, the placed the subs feet on the screw heads. Helped the bass a lot.
You will notice in my original post I said there may be a problem, once again this is not a standard receiver and I wanted to caution that there might be an issue. It should work just fine, but I didn't want Rob to fry his system on advice he got at BestBuy.
Kelticwizard, if you would like I can email you a scan of the schematic of the Jolida JD1501 amp that clearly shows the negative terminal connected to common chassis ground, which is also A/C ground.
net-david said:
Actually, I think it is pretty much a universal receiver. I think the sub is merely two channels tied together to give an output impedance, (3 ohms) of half the normal impedance for the other channels, (6 ohms). I do not know if there is a crossover at the top end.
Here are the specs for the RT 2500 system, which I think must be similar to the specs for the RT 2580 system. I really think this is just a normal output, and the only thing inside that stock sub is a little 5" speaker of 3 or 4 ohms impedance. Oh, and there is a little light that goes on at overload-my guess a diode set to light a certain voltage.
I sure hope that 40 Hz as a low cutoff is a misprint.
Attachments
net-david said:
I just checked the Jolida. It is an integrated, hybrid amp. That means it contains tubes. Which automatically means "exotic", though the price, at $625, seems reasonable enough.
Actually, I don't know if "hybrid" means tubes in the next-to-last amplifier stage before sending the signal to output transistors, (Mosfets?), or whether that means the Jolida is tube pre-amp, transistor power amp.
I did mention that I thought we could discount the possiblity of exotic designs. This is Best Buy, this is striclty bang-for-the-buck.
Perhaps I should have written that I had never come across a mass-fi amp that tied it's speaker inputs to the AC ground. At that price range, it is all straightforward and all familiar chips, I think.
I would not mind seeing the schematic of the Jolida, though. Let me Email you with my Email address, though in truth I know little of tube designs, (and really, only the very basics of solid-state).
net-david said:
Not familiar with this term. I know BJT, (Bipolar Junction Transistor) and OTL, (Output TransformerLess), but not this.
Explanations would be welcome. 🙂
MY QUEST IS OVER!
😀
First: THANKS TO ALL FOR YOUR INPUT OVER THE LAST WEEK!
I received lots of great advice and actually learned a few things.
------------------------------------------------------------------------------>
I bought the Sony 150 watt sub at Best Buy for 200 bucks last night.
😱
It weighs a hefty 46 pounds and looks serious.
I bought some Monster speaker cable and simply hooked it up as the old RCA was.
The Sony offered two input clip jacks (left and right) and I just hooked it up on the left channel.
(It also has two output jacks and one RCA-type connector.)
I powered it all up and did some sound tweaking and then put in "LOTR - The Two Towers - Battle for Helms Deep" -
and OH MY GOSH! - It was AWESOME!
This "cheap" little sub really rocked.
😎
It EASILY tripled what I had before and gave me EVERYTHING I'd been hoping for and then some.
I only need to turn it up about 40% to fill up and max out my 22' x 17' living room.
And then I watched "Indiana Jones and the Temple of Doom".
WOW. It makes the movies SO much more enjoyable now.
My wife was unusually very pleased as well.
So, let me just say, I don't know what all the fuss is about getting these 400 watt + subs and spending lots of money.
And for that matter, I don't WANT to know.
🤐
I'm sure you'll say the new sub doesn't go low enough or something.
But I love it and don't think I'll ever need anything else.
So if ignorance is bliss - then I'm the one on the couch smiling.
However - I'm "thinking" about running the old sub out from the Sony and placing it in the rear of the room behind a couch (because I CAN).
I was thinking it might help equalize the bass a little as the Sony is on the front right side of the room.
I thought it would be worth a try since I already have the thing and why waste a nifty little sub?...
But since it would be coming from the Sony - would it be getting the same level and thus distort?
I could always use it for a beehive or something.
Any thoughts?
OH - Also -
The Sony has a "reverse" or something switch on it.
What's that do and can I flip it on the fly?
Also also, how high should I adjust the CUT OUT?
THANKS AGAIN Y'ALL!
😀
First: THANKS TO ALL FOR YOUR INPUT OVER THE LAST WEEK!
I received lots of great advice and actually learned a few things.
------------------------------------------------------------------------------>
I bought the Sony 150 watt sub at Best Buy for 200 bucks last night.
😱
It weighs a hefty 46 pounds and looks serious.
I bought some Monster speaker cable and simply hooked it up as the old RCA was.
The Sony offered two input clip jacks (left and right) and I just hooked it up on the left channel.
(It also has two output jacks and one RCA-type connector.)
I powered it all up and did some sound tweaking and then put in "LOTR - The Two Towers - Battle for Helms Deep" -
and OH MY GOSH! - It was AWESOME!
This "cheap" little sub really rocked.
😎
It EASILY tripled what I had before and gave me EVERYTHING I'd been hoping for and then some.
I only need to turn it up about 40% to fill up and max out my 22' x 17' living room.
And then I watched "Indiana Jones and the Temple of Doom".
WOW. It makes the movies SO much more enjoyable now.
My wife was unusually very pleased as well.
So, let me just say, I don't know what all the fuss is about getting these 400 watt + subs and spending lots of money.
And for that matter, I don't WANT to know.
🤐
I'm sure you'll say the new sub doesn't go low enough or something.
But I love it and don't think I'll ever need anything else.
So if ignorance is bliss - then I'm the one on the couch smiling.
However - I'm "thinking" about running the old sub out from the Sony and placing it in the rear of the room behind a couch (because I CAN).
I was thinking it might help equalize the bass a little as the Sony is on the front right side of the room.
I thought it would be worth a try since I already have the thing and why waste a nifty little sub?...
But since it would be coming from the Sony - would it be getting the same level and thus distort?
I could always use it for a beehive or something.
Any thoughts?
OH - Also -
The Sony has a "reverse" or something switch on it.
What's that do and can I flip it on the fly?
Also also, how high should I adjust the CUT OUT?
THANKS AGAIN Y'ALL!
Ha!
No, seriously.
I'm tremendously happy.
And I have so MANY other projects to eat money- like-
tornado shelter
sun room
pool
garden shed
sex change
chain link fence
water garden
etc...
PS - I was just kidding about the chain link fence.
No, seriously.
I'm tremendously happy.
And I have so MANY other projects to eat money- like-
tornado shelter
sun room
pool
garden shed
sex change
chain link fence
water garden
etc...
PS - I was just kidding about the chain link fence.
Re: MY QUEST IS OVER!
First, congratulations on your purchase. With very little electronic knowledge, you recognized a glaring deficiency in your home setup and took logical steps to correct it.
Even your RCA home theater setup was a bargain. It offered so much for not so much money, you grabbed it. With modern electronic manufacturing techniques, it is amazing that so much sound can be had for so little money.
If you took the original 20 watt receivers of the early sixties, multiplied the cost for inflation, and figured out what they would cost today for just TWO channels, I'm sure they would be well over $1,000! Here, you paid just $300 for six more powerful channels.
Of course, when you give so much for so little money, you have to scrimp somewhere, and RCA scrimped on the sub. You smartly corrected that situation. Good for you.
I just wrote a long post about how to go about hooking the RCA sub up.
I purposely erased it.
The RCA amp output has a very low impedance, which is good. However, that means the RCA sub might have a very low impedance.
The sub's low impedance might cause problems when you try to hook the sub up. Probably won't, but might.
The low impedance of the RCA amp, (subwoofer out), will not cause problems. However, the low impedance of the RCA sub might cause issues if you hook it up in ways it was not designed to do.
You love the way things are now, by hooking things up in a straightforward, conventional way.
Don't mess with exotic setups. Sometimes they work, sometimes they lead to trouble.
One thing. As another poster pointed out, subs love to be put into a corner. Try the Sony in a corner, and see how it sounds.
Good luck with your new sub!
First, congratulations on your purchase. With very little electronic knowledge, you recognized a glaring deficiency in your home setup and took logical steps to correct it.
Even your RCA home theater setup was a bargain. It offered so much for not so much money, you grabbed it. With modern electronic manufacturing techniques, it is amazing that so much sound can be had for so little money.
If you took the original 20 watt receivers of the early sixties, multiplied the cost for inflation, and figured out what they would cost today for just TWO channels, I'm sure they would be well over $1,000! Here, you paid just $300 for six more powerful channels.
Of course, when you give so much for so little money, you have to scrimp somewhere, and RCA scrimped on the sub. You smartly corrected that situation. Good for you.
RobAche said:😀
However - I'm "thinking" about running the old sub out from the Sony and placing it in the rear of the room behind a couch (because I CAN).
I was thinking it might help equalize the bass a little as the Sony is on the front right side of the room.
I thought it would be worth a try since I already have the thing and why waste a nifty little sub?...
But since it would be coming from the Sony - would it be getting the same level and thus distort?
I could always use it for a beehive or something.
Any thoughts?
I just wrote a long post about how to go about hooking the RCA sub up.
I purposely erased it.
The RCA amp output has a very low impedance, which is good. However, that means the RCA sub might have a very low impedance.
The sub's low impedance might cause problems when you try to hook the sub up. Probably won't, but might.
The low impedance of the RCA amp, (subwoofer out), will not cause problems. However, the low impedance of the RCA sub might cause issues if you hook it up in ways it was not designed to do.
You love the way things are now, by hooking things up in a straightforward, conventional way.
Don't mess with exotic setups. Sometimes they work, sometimes they lead to trouble.
One thing. As another poster pointed out, subs love to be put into a corner. Try the Sony in a corner, and see how it sounds.
Good luck with your new sub!
Thank you sir.
You are a gentleman and a scholar...
I have the sub as close to the wall and corner as possible.
I was gonna try the other in the opposite corner - but it's no biggie.
Regarding the reverse phase switch...
What is it?
Why should I use it?
Can I switch it while the sub is running?
Thankya.
You are a gentleman and a scholar...
I have the sub as close to the wall and corner as possible.
I was gonna try the other in the opposite corner - but it's no biggie.
Regarding the reverse phase switch...
What is it?
Why should I use it?
Can I switch it while the sub is running?
Thankya.
RobAche said:
The switch reverses the direction the cone moves in regard to its
input. You can switch when the sub is running. For the correct
setting, which could be either, and can vary depending on the
placement of the sub, the sub and your other speakers will gel
together better.
The frequency setting is also used to obtain a good gel with your
other speakers, but this also interacts with the relative volume
setting of the subwoofer.
It will take you a while to get the settings correct.
I suggest you don't try and use your old subwoofer,
you'll find adjusting all the settings next to impossible.
Also note that you don't need a thick cable to your
new sub, very thin wire will work just as well.
Glad you like it !
🙂 /sreten.
sreten said:
Not to be a pest, but how do you KNOW which setting is correct?
Normal or Reverse?
Do you do it by ear??
Signed,
Baffled
Tiroth:
Thank you very much. As it happens, a question about bridging two channels to send a signal to a single subwoofer was the very first message I posted on diyAudio. I just never knew the term BTL.
Damn. This hobby has so many abbrevations that it is hard to keep up with them. 😉
Thanks again. 🙂
Thank you very much. As it happens, a question about bridging two channels to send a signal to a single subwoofer was the very first message I posted on diyAudio. I just never knew the term BTL.
Damn. This hobby has so many abbrevations that it is hard to keep up with them. 😉
Thanks again. 🙂
Erm you don't ! You have to do it by ear. For a position of the
Sub in room one setting will give better results than the other.
A good position for the Sub is a 1/3 along the wall with the 3
front speakers. The better setting will give more 'body' to the
sound than the other.
🙂 /sreten.
Now that I think about it, some of the stuff net-david posted is beginning to make some sense.
I wonder how many mass-fi manufacturers bridge two of their channels to send a signal to a sub. Maybe many others, maybe RCA is the only one. Hobbyists do it all the time, but that's home brew stuff. For a long time, most AV receivers just had an RCA jack to run to the subwoofer amp.
And it is possible that Sony makes it's own sub amps, even if everyone else uses one or two suppliers. Which might, just possibly, use an input that uses the wall's ground as it's ground, unlike just about everybody else.
Very, very unlikely and a bad choice to make for a sub amplifier that is supposed to hook up to a huge variety of different brands of amplifiers. But every now and then, something like this happens.
I wonder: what would be a safe way to test for that using just a multimeter?
I wonder how many mass-fi manufacturers bridge two of their channels to send a signal to a sub. Maybe many others, maybe RCA is the only one. Hobbyists do it all the time, but that's home brew stuff. For a long time, most AV receivers just had an RCA jack to run to the subwoofer amp.
And it is possible that Sony makes it's own sub amps, even if everyone else uses one or two suppliers. Which might, just possibly, use an input that uses the wall's ground as it's ground, unlike just about everybody else.
Very, very unlikely and a bad choice to make for a sub amplifier that is supposed to hook up to a huge variety of different brands of amplifiers. But every now and then, something like this happens.
I wonder: what would be a safe way to test for that using just a multimeter?
Erm KC,
not that familiar with American mains voltage but
in the UK a two wire mains lead is dead give away
of a fully isolated design.
🙂
not that familiar with American mains voltage but
in the UK a two wire mains lead is dead give away
of a fully isolated design.
🙂
Sreten:
Thanks.
Suppose I take a 2 wire line from the wall, and run a power transformer with 3 terminals out-plus, minus, and ground. Would everything running off that transformer be isolated?
I guess it would be, since there is no physical connections between windings on a transformer.
So as long as everything runs off a transformer, there is no connection between the amp circuitry and the wall?
Thanks.
Suppose I take a 2 wire line from the wall, and run a power transformer with 3 terminals out-plus, minus, and ground. Would everything running off that transformer be isolated?
I guess it would be, since there is no physical connections between windings on a transformer.
So as long as everything runs off a transformer, there is no connection between the amp circuitry and the wall?
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