SDA-SRS 3.1TL - Need Assistance with Feedback Problem

heroesunplugged

Going to call it a night. Will continue the discussion later today. Thanks everybody!

FTGV

heroesunplugged wrote: »

Does "dual differential" mean bridged/balanced? How can I find out?

It means balanced but they may be just be referring to the input stage of the amp, not its output stage configuration.

Some amps are differential/ balanced from input to output but they tend to be at the spendier end of the scale.

FTGV

Your welcome Chris,good luck.

Toolfan66

The Dreadnought is the best thing you could do, you will get better sound with a common ground or non common ground amp...

F1nut

Toolfan66 wrote: »

The Dreadnought is the best thing you could do, you will get better sound with a common ground or non common ground amp...

^ THIS ^

heroesunplugged

Toolfan66 wrote: »

The Dreadnought is the best thing you could do, you will get better sound with a common ground or non common ground amp...

Have thought of the dread as an option, but was attempting to avoid the added expense by selecting an amp that it isn't necessary. Will research the dreadnaught option in more detail. Skimmed some of the discussions a while back, but not sure I'm fully equipped to build one. And all of the upgrade options can mean added cost for the speaker upgrades necessary. Realizing they are options I tend to lean toward getting the speakon interconnects, but may have to opt for a basic design since the speaker terminals then need to be modded. Its the domino effect that I have been side-stepping by getting an amp that "is compatible". Apparently that didn't work out so well!

No reply from Emotiva yet.

heroesunplugged

Okay, called Emotiva since I didn't get an e-mail, but I took the tech's suggestions and I think its some type of interaction between the preamp and amp when the SDA speaker is being used. Let me explain that when I first received the amp I was using a Pioneer Elite VSX-82TXS as a preamp. I never had any issues and had everything set to factory default settings on the SA-250. Switches were in the 29 dB gain for the RCA input and ground/lift was set to ground.

Rory, with Emotiva tech support, suggested disconnecting everything except the amp, trying various settings and then proceed by adding each device into the chain a step at a time. He also recommended using the same outlet and eliminating any surge protection or line conditioning. His argument is that by minimizing components or equipment, and gradually adding it back in, makes for much easier and more methodological troubleshooting. The following is the play-by- play of what has been done, so that it may potentially assist someone else figure out or isolate an issue. I have also included a few subjective, thoughts concerning the sound differences between the SA-250 and a vintage Sony amp. For "the rest of the story" jump to the last paragraph.

To begin, connect speaker cables, confirm SDA interconnect cable is plugged in, connect power cord to the amp, set amp to Ground, set Gain set at 29 dB (RCA cables disconnected but are the selected option on the amp), flip the main power switch on the back of the amp and then power the amp up using the standby switch in front. The amp alone, posses no issue. There is no signal going in and absolutely nothing coming out. The speakers don't have any hint of noise or sound, as if the amp isn't on.

Next repeat the above with the Gain set to 23 dB setting. Same results - nothing coming from speakers. Next try the amp with ground in the "Lift" position and same resulting lack of any type of audible signal.

Run RCAs from the NuForce MCP-18 preamp into the SA-250 amp, plug in preamp to same/shared power outlet, set switches back to 29 dB gain, set amp to Ground, turn on pre, set to -84 dB (lowest) volume, and power up amp. Amp clicks and then hear a short low volume "feedback". Power down amp.

Decide to try ground switch in "Lift" position and results in same "feedback" but louder than grounded. Decide to go back to Ground on the amp and lower the Gain mode to 23 dB. Ah-hah, no "feedback"! So now raise the volume on the pre gradually until hitting -7.5 dB with no noticeable change. Power down everything.

Move the preamp power cord over to ACP surge protector and repeat power on with same good results. Power on Technics CD changer and hit play, while gradually increasing the level with positive results and now seem to have everything working great. It appears the MCP-18 won't work using the amp's 29 dB gain setting while driving the 3.1TLs. It's good that the amp has the optional 23 dB gain setting so the SDAs can be used. Having said this, there is still a question as to what is happening electrically when adding the dimensional driver to the mix? Emo support did confirm that SA-250 is a common ground amp and is not balanced at the output stage.

There is such a vast difference in sound between the vintage Sony TA-3200F amp that was used to fill while figuring out the SA-250. The 3200F barely seems to activate the dimensional drivers in the 3.1TLs. The Sony is much more 2 dimensional, but has good left to right sound stage. It is very pleasant tonally and has better than exceptional bass extension.

The SA-250 widens, not only the sound stage, but dramatically deepens and projects sound several feet, to the left and right, into the room. It sounds quite incredible for most music, but can obscure the placement or pinpoint accuracy of instruments and nuanced effects with music that's familiar. To clarify, its not bad, just very different. It will require further evaluation because its an extraordinary change. It is more enveloping, much smoother (grain-free), full bodied and covers a larger spatial area, while using the Sony is much closer to what I'm use to hearing while running the Emotiva with my non-SDA speakers.

The friend I bought the 3.1TLs from was running a Classe CA-200. These speakers were great with that amp, but the dimensional drivers were never this active. The Classe was very pleasant and smooth, but never very exciting regardless of what was being played. It loafed along and shrugged. The SA-250 is very easy to listen to but conveys the mood of the music much more accurately and the NuForce pre is super clean and conveys a sense of immediacy.

The conclusion of my troubleshooting, thus far, is that the NuForce MCP-18 pre combined with the Emotiva SA-250 amp works with the 3.1TL's dimensional array when set to the lower, 23 dB Gain option. The Ground, or Lift Switch, needs to be set to Ground. The next plan is to acquire a set of XLR cables to determine if the gain can be run on the higher setting. Very pleased with the result of the sound of this combination. Will work toward more ideal placement and room integration.

heroesunplugged

Okay. Had to call Emotiva since I didn't get an e-mail, but I took the tech's suggestions and I think its some type of interaction between the preamp and amp when the SDA speaker is being used. Let me explain that when I first received the amp I was using a Pioneer Elite VSX-82TXS as a preamp. I never had any issues and had everything set to factory default settings on the SA-250. Switches were in the 29 dB gain for the RCA input and ground/lift was set to ground.

Rory, with Emotiva tech support, suggested disconnecting everything except the amp, trying various settings and then proceed by adding each device into the chain a step at a time. He also recommended using the same outlet and eliminating any surge protection or line conditioning. His argument is that by minimizing components or equipment, and gradually adding it back in, makes for much easier and more methodological troubleshooting. The following is the play-by- play of what has been done, so that it may potentially assist someone else figure out or isolate an issue. I have also included a few subjective, thoughts concerning the sound differences between the SA-250 and a vintage Sony amp. For "the rest of the story" jump to the last paragraph.

To begin, connect speaker cables, confirm SDA interconnect cable is plugged in, connect power cord to the amp, set amp to Ground, set Gain set at 29 dB (RCA cables disconnected but are the selected option on the amp), flip the main power switch on the back of the amp and then power the amp up using the standby switch in front. The amp alone, posses no issue. There is no signal going in and absolutely nothing coming out. The speakers don't have any hint of noise or sound, as if the amp isn't on.

Next repeat the above with the Gain set to 23 dB setting. Same results - nothing coming from speakers. Next try the amp with ground in the "Lift" position and same resulting lack of any type of audible signal.

Run RCAs from the NuForce MCP-18 preamp into the SA-250 amp, plug in preamp to same/shared power outlet, set switches back to 29 dB gain, set amp to Ground, turn on pre, set to -84 dB (lowest) volume, and power up amp. Amp clicks and then hear a short low volume "feedback". Power down amp.

Decide to try ground switch in "Lift" position and results in same "feedback" but louder than grounded. Decide to go back to Ground on the amp and lower the Gain mode to 23 dB. Ah-hah, no "feedback"! So now raise the volume on the pre gradually until hitting -7.5 dB with no noticeable change. Power down everything.

Move the preamp power cord over to ACP surge protector and repeat power on with same good results. Power on Technics CD changer and hit play, while gradually increasing the level with positive results and now seem to have everything working great. It appears the MCP-18 won't work using the amp's 29 dB gain setting while driving the 3.1TLs. It's good that the amp has the optional 23 dB gain setting so the SDAs can be used. Having said this, there is still a question as to what is happening electrically when adding the dimensional driver to the mix? Emo support did confirm that SA-250 is a common ground amp and is not balanced at the output stage.

There is such a vast difference in sound between the vintage Sony TA-3200F amp that was used to fill while figuring out the SA-250. The 3200F barely seems to activate the dimensional drivers in the 3.1TLs. The Sony is much more 2 dimensional, but has good left to right sound stage. It is very pleasant tonally and has better than exceptional bass extension.

The SA-250 widens, not only the sound stage, but dramatically deepens and projects sound several feet, to the left and right, into the room. It sounds quite incredible for most music, but can obscure the placement or pinpoint accuracy of instruments and nuanced effects with music that's familiar. To clarify, its not bad, just very different. It will require further evaluation because its an extraordinary change. It is more enveloping, much smoother (grain-free), full bodied and covers a larger spatial area, while using the Sony is much closer to what I'm use to hearing while running the Emotiva with my non-SDA speakers.

The friend I bought the 3.1TLs from was running a Classe CA-200. These speakers were great with that amp, but the dimensional drivers were never this active. The Classe was very pleasant and smooth, but never very exciting regardless of what was being played. It loafed along and shrugged. The SA-250 is very easy to listen to but conveys the mood of the music much more accurately and the NuForce pre is super clean and conveys a sense of immediacy.

The conclusion of my troubleshooting, thus far, is that the NuForce MCP-18 pre combined with the Emotiva SA-250 amp works with the 3.1TL's dimensional array when set to the lower, 23 dB Gain option. The Ground, or Lift Switch, needs to be set to Ground. The next plan is to acquire a set of XLR cables to determine if the gain can be run on the higher setting. Very pleased with the result of the sound of this combination. Will work toward more ideal placement and room integration.

txcoastal1

I'm happy that you are moving forward

Have your 3.1TL's been upgraded?

Congrats and welcome to Club Polk

heroesunplugged

Thanks txcoastal1.

No mods yet, they are still untouched. I have considered starting with the crossovers, but realize that there are a series of changes that can be accomplished together while the drivers are removed. Its a matter of coordinating everything together and of course funds.

Had this pair for about a year. The newer preamp is a definitive improvement. The Norman Labs 435s, prior to hooking up the 3.1s, resulted in improved quality. Clarity, tonal balance, texture, micro-dynamics, and sound stage are all improvements with the NuForce.

I have some other NLs I'm going to hook up, but am pretty excited about using the 3.1TLs in my main system.

FTGV

The Emo tech gave you great advice and the correct procedure to track down and eliminate ground loop issues. However I believe earlier you measured 14 ohms across the two negative binding posts with the ground lift switches in the ground position. If so the amp is not truly common ground. That small amount of resistance is likely to cause issue. The simple fix is strapping the negative outputs together. Since the amp is not a bridged/ balanced output design you can safely do so.

heroesunplugged

Agreed FTGV, not truly common ground - although leaning to it is or isn't. Either it is common ground or it isn't.

Still had that thought floating around in my mind that continuity, although low when "grounded", may be the cause of the hyperactive dimensional effect too and forcing the use of the lower input sensitivity. The gain of 29 dB isn't high and is average for home audio so it doesn't add up to have to use the -6 dB setting. While it is actually a pretty cool "effect", this doesn't seem to be the way the SDA speakers are intended to sound. Most vocal tracks seem to collapse into the center. They sound more distant than usual, while the dimensional speakers seem to play as loud (sometimes louder) than the standard stereo portion most of the time. The space between center and extreme left and right is filled in quite evenly and forms an enveloping bubble dependent on the mix. There are instances when there seems to be an emphasis on notes that fall within the 400 to 600 Hz region too and that may attribute to what may be best described as a somewhat hollowed/carved out sound. There is also less solidity to bass than when using the Sony TA-3200F amp and that's surprising. Triple checked the polarity of the connections as a result.

The tech indicated that the ohm reading being taken across the negative terminals doesn't mean that it's not common ground and alluded to a different way to measure this to confirm ground. Will see if he can clarify since we didn't pursue it. He didn't go into detail and I don't understand why there seems to be differing methods to determine ground. Everyone I've discussed this with at Emotiva, including this tech, asks somebody else whether this amp is common ground and consistently have the same answer, but if they're asking the same person, or getting information from the same source, then that explains why. Perhaps the SA-250 amp is meant to be common ground on paper, but in reality is not? There is a corresponding increase in the ill effect with higher continuity readings and worsens with increased gain.

F1nut

I missed that you got 14 ohms across the negative posts. It's not a common ground amp. Do what Fred suggests, strap the negative posts to see if that doesn't fix the issue. If it does and you want to keep the amp seriously think about getting a Dreadnought.

The tech indicated that the ohm reading being taken across the negative terminals doesn't mean that it's not common ground and alluded to a different way to measure this to confirm ground.

That doesn't make sense to me.

F1nut

I didn't want to have to build a dreadnaught or put anything else in the signal path.

The Dreadnought actually improves the performance regardless of whether the amp is common ground or not.

heroesunplugged

Going to try strapping tonight. The Dreadnought may be the resulting option, but timing isn't ideal, because of a downsizing phase that I plan to see through (stuff in general). I have read one discussion where DarqueKnight plots the differences. There is a consensus that the results of increased performance are worth having it in the chain, regardless of the amp being used.

Weighing the overall investment that may be required to get these speakers up to their full potential vs others that require less time and expense. I desire simplicity and sometimes the way to simplicity can involve a bit of complexity to arrive at that point. Maybe it's actually an untangling of the complexity that's been created. Either way, don't want to regret having passed on something that can ultimately lead to the end goal - excellent sound and reduction in the quantity of speakers and components (including a little of everything else).

heiney9

Heroesunplugged, the SDA's are worth the hassle for lack of a better word. Stick with them and you will be rewarded.

H9

FTGV

heroesunplugged wrote: »

Everyone I've discussed this with at Emotiva, including this tech, asks somebody else whether this amp is common ground and consistently have the same answer, but if they're asking the same person, or getting information from the same source, then that explains why.

Its the definition of common ground that's confusing things. Emo's tech is defining it as the negative binding posts of each channel being at ground potential,and he is correct. However the channels grounds are isolated from each other with a small amount of resistance. Polk defines common ground as having no resistance(other than that of the wire) between the negative binding posts to avoid the kind of issue you are experiencing. Others with similarly configured amplifiers have reported having similar issues to yours that were fixed by simple strapping.

heroesunplugged

A simple strapping has moved me from ground potential to find common ground as Polk defines it, as having no resistance, more than a few times. A wire can work wonders. I can connect with that!

F1nut

Now, you can tell the people at emo what common ground really means......LOL

heroesunplugged

Very funny F1nut.

FTGV

So then all is well Chris?

heroesunplugged

Strapped the amp as suggested and its now working on the higher 29 dB setting. Sounds much better than the Adcom GFA-5500 did when strapped. The SA-250 sounds better regardless for that matter. Sound has much better solidity and focus, rather than ethereal, but may run unstrapped with the lower gain from time to time. Really is an interesting effect and the continuity may be low enough to get away with it for demoing a couple of songs.

Still have some reservation as to the tonality of this speaker. Seems a little heavy handed in some midrange frequencies, but this is still early. There are trade-offs with all speakers and the rooms we have them in. Will work with placement and then think a recap of this pair will likely make substantial progress.

heiney9 wrote: »

Heroesunplugged, the SDA's are worth the hassle for lack of a better word. Stick with them and you will be rewarded.

H9

Will take H9's encouragement, to not give up too easily, or early. One thing I have found is how much placement influences the dimensional width. Bringing them closer together broadens the stage the full width of the room. Will continue to work out placement and plan to make a new interconnect cable to go between the speakers. The one that was included with this pair is very thin gauge. Likely about 18 gauge. Want to go to a 12 gauge to match the others.

Rory, with Emotiva, was very helpful yesterday and said he will get with Lonnie, the company's VP of Engineering, to see if they can take a look at the possible interaction between crossover and amp. He looked at the schematic of a 2C, to see how the dimensional part of the crossover is designed. Lonnie designed this particular amp so he may have some insight. Don't know if there is anything they can recommend other than what's been said here. Rory confirmed that adding the wire for strapping is an option as FTGV has encouraged from the start. Rory also proposed possibly buying another amp, but I'll get a dreadnought as F1Nut and Toolfan66 have suggested before buying another amp from Emotiva. I've owned the UPA-500 and XPA-100 mono-blocks and was a little disappointed with the lack of detail. Sold them within 3 months of purchasing. The SA-250 has been the best amp I've owned out of five. The Sony TA-3200F bested the other Emotiva amps by a slight margin. The gain structure isn't very aggressive, but the detail and imaging is still very good and the bass is full and controlled for an amp that has relatively low damping factor, but a passive crossover can influence the damping factor's effectiveness, so may negate the usefulness of that spec anyway (so I've read).

Now I can get a plan together as to what the next step will be, since the amp issue is basically solved. With the amp strapped it now has an extremely low amount of AC noise, but it can only be heard placing my ear within a few inches of the speaker. At the seated position it isn't audible. The Dreadnought will likely be an option several months away.

Thanks for the suggestions and helping a relatively new SDA owner work through an incompatibility issue. Looks like there is a great community to support going as far as one desires, in getting these to reach their highest potential. Thanks for sharing your time and knowledge.

Chris

pitdogg2

SDA's should be 6-8' apart and 6-8" off the wall behind them and no walls close to their sides for best effect. Absolutely no toe in like you would do with regular speakers. best if there is nothing in between them as well. YMMV

F1nut

He looked at the schematic of a 2C

I believe you meant 1C, which is not a good choice to study. Have them study any of the TL models.

heroesunplugged

Alright pitdogg2, will take the placement suggestions under advisement.

heroesunplugged

F1nut wrote: »

He looked at the schematic of a 2C

I believe you meant 1C, which is not a good choice to study. Have them study any of the TL models.

Probably right. Not well versed with all of the SDA-SRS models. Only thing for sure is that he didn't include "TL" in the model. Will call him in a few minutes to check in and suggest that they look at the TL since you've advised it.

pitdogg2

here you go since this is what you have

3.1TL

https://us.v-cdn.net/5021930/uploads/attachments/1/8/5/1/1/26697.pdf


and 1.2TL

https://us.v-cdn.net/5021930/uploads/attachments/1/8/5/1/1/26687.pdf

heroesunplugged

Thanks for the links for the schematics.

heroesunplugged

Doing a search for the Dreadnought schematic or wiring diagram. Would like to share this with Emotiva if it's okay and available. Do realize that many have moved to the 1000VA transformer.

Rory wrote back telling me that the SA-250 amp is incompatible. Basically the circuit protection is highly susceptible to back EMF from the dimensional driver. He gives a fairly detailed explanation of the voltage and how the protection sees an out of phase signal. May apply to a few other non-common ground and "common ground potential" amps like this one. Thinking there should be another term, such as absolute ground or resistive common ground, so we are absolutely sure we're speaking with a common language. Get that common doesn't translate "exact same". They won't recommend this amp to anybody that asks in the future. Since this was a limited production amp may be the only one using this model with SDA speakers at their recommendation, so don't figure there is any risk of this happening again, unless they design another amp later on with a similar/"common" design.

txcoastal1

You may post a WTB for either an 800 or 1000....and bump it ever so often. There was a huge buy recently, and the 1000's are only available on a qty order.

The 800 is still a great value, and there might be someone willing to let one go, or you could start from scratch.

Sorry you had to go through all this trial and error stuff, but the thread laid out some great info.

Good luck on your journey and hope you stick around

--Ron