[Trogdor]

Quote:

Originally Posted by Michael G. (I've answered your private email...) Michael Mardis was the first to warn of unacceptable levels of DC leakage in the T amp design, as far as I know. Mardis claims to solve the problem by using "a large, DC blocking capacitor". I'll bet the DC leakage problem is not present on all T amps, it is probably an intermittent problem due to quality control issues. It is tempting to try such a cheap amplification source, but maybe it's not worth the risk?

Jeesz, I never thought that perhaps I just have a lemon of an amp and that's why T-amp/AKG folks aren't experiencing this issue.

I agree Michael that its risky but the whole point IS that its a cheap source. Without the T-amp I'm probably going to need to invest a heavy sum into amplification (i.e. $300+).

I'm going to ask Mr. Mardis about the DC blocking capacitor fix which a friend of mine also says would fix it. Another idea is to ask Sonic Impact directly...not sure how they are on technical support...

 

[Michael G.]

Quote:

Originally Posted by Trogdor Jeesz, I never thought that perhaps I just have a lemon of an amp and that's why T-amp/AKG folks aren't experiencing this issue. I agree Michael that its risky but the whole point IS that its a cheap source. Without the T-amp I'm probably going to need to invest a heavy sum into amplification (i.e. $300+). I'm going to ask Mr. Mardis about the DC blocking capacitor fix which a friend of mine also says would fix it. Another idea is to ask Sonic Impact directly...not sure how they are on technical support...

Or, maybe Sonic Impact will accept your "defective" amp back under warranty? If you can demonstrate that the operation is faulty, maybe you can get it replaced. It's worth checking out. I guess you could test the new one out first before using...

 

[Tachikoma]

Quote:

Originally Posted by Trogdor I agree Michael that its risky but the whole point IS that its a cheap source. Without the T-amp I'm probably going to need to invest a heavy sum into amplification (i.e. $300+).

You could give the other tripath amps a try, they aren't that much more expensive than the original T-amp. (TA2020, TA2022 etc)

 

[philodox]

Quote:

Originally Posted by Trogdor I found out from AKG that the headphones on the Disney rides all use AKG K1000 ear speaker drivers!!!! Swear, that's what he told me...

Time to go to Disney world and go on some rides with a screwdriver!

Sorry to hear about your misfortune guys, that are a great set of headphones.

 

[PeeeMeS]

Quote:

Originally Posted by philodox Time to go to Disney world and go on some rides with a screwdriver! Sorry to hear about your misfortune guys, that are a great set of headphones.

Ok where is this Disney world and which rides feature "ear speakers"?

 

[Trogdor]

Quote:

Originally Posted by Tachikoma You could give the other tripath amps a try, they aren't that much more expensive than the original T-amp. (TA2020, TA2022 etc)

I should get them back today from AKG as good as new.

What other Tripath amps are there in the same price range?

 

[Trogdor]

Also, can someone explain to me the ultrasonic issues? I'm wondering if RF overheated my drivers. As far as I can tell, I have NO IDEA why just one of my earspeakers died.

 

[flecom]

I am fairly certain that the tripath chips are supposed to have DC blocking caps after the IC... i am fairly certain my original T-Amp had dc blocking caps... which is good becuase something happened to that amp and it overheated to the point where literally all the solder flowed off and pooled at the bottom of the case I had it in...

what IC is in the super-t? if its one of the chips that the datasheet sais requires dc blocking i would ask the company that made it to pay for your repairs

 

[cosmopragma]

Trogdor, before utilizing a switching amp you should have read the related threads.It's recommended to measure the DC offset before you connect the AKGs.
When you measured the offset you did set the multimeter wrong.200 mV is the right setting.Your measurements are unprecise, but most probably the DC offset is not the reason for the failure.You've measured something like 15-25 mV for the left driver that failed.That's not that much.Not stellar, but acceptable for the K1000s.The 85-95 mV on the other channel are clearly borderline, but still probably not dangerous.
Someone here recommended to purchase a vintage amp.What do you think how these age old amps measure if not refurbished?
100 mV is common.Did you ever hear about someone blowing a K1000 driver by using an old Marantz?
I guess it was just coincidence.
Don't get me wrong, something in the range of 100 mV is crap and should be considered as being defective.I would ask the Super T-amp manufacturer to send you an amp with better specs.I've just sent a speaker amp with 23 mV on one channel back to the lab for adjustment.I would adjust it myself if I had the schematics at hand, but the amp is under warranty anyway and the manufacturer agreed that more than 10 mV is unacceptable for a new amp and they even cover the shipping costs.
BTW, the Tripath 2020 based amp I'm using in the meantime measures 2mV/23mV.

 

[pawlowski6132]

Quote:

Originally Posted by Trogdor I should get them back today from AKG as good as new.

That seemed pretty quick. How long from time you shipped until received in days? Thanx

 

[cosmopragma]

Quote:

Originally Posted by Trogdor Also, can someone explain to me the ultrasonic issues? I'm wondering if RF overheated my drivers.

Again, not likely.Lots of head-fiers have utilized unmodded T-amps, and no failures have been reported.

Short and simple, there is a filter stage applied in switching amps in order to keep the frequency response in the treble area relatively even and to avoid nasty ultrasonic peaks.This filter stage is designed to work when connected to a common 4-8 Ohm speaker load and doesn't work when you connect your 130 Ohm AKGs.A head-fi member did run a simulation and got a nasty extreme peak at 53 KHz.No one actually measured it, so we don't know the real life behaviour.
However, for the peace of mind there's a simple workaround.Just apply some quality high power ( at least 6 Watt, 10 is better) resistors around 6 Ohm in parallel, and the amp basically "sees" a 6 Ohm load.The icing on the cake is that the switching amps sound better this way, and the mod is cheap and absolutely easy to perform.

 

[Trogdor]

Cosmo, your absolutely right. I jumped the gun. I don't even think 100mv would really damage the AKG's. I'm confused at this point on what really killed by AKG K1000's. Perhaps I clipped them but I doubt it. How many watts do the AKG's take (I thought it was like 7-10 watts)?

Can I really put a 6 or 8 ohm resistor on the output terminals and still get enough current to drive the K1000's effectively?

I get my AKG's tomorrow actually. It takes about a week in turn around time.

Quote:

Originally Posted by cosmopragma Trogdor, before utilizing a switching amp you should have read the related threads.It's recommended to measure the DC offset before you connect the AKGs. When you measured the offset you did set the multimeter wrong.200 mV is the right setting.Your measurements are unprecise, but most probably the DC offset is not the reason for the failure.You've measured something like 15-25 mV for the left driver that failed.That's not that much.Not stellar, but acceptable for the K1000s.The 85-95 mV on the other channel are clearly borderline, but still probably not dangerous. Someone here recommended to purchase a vintage amp.What do you think how these age old amps measure if not refurbished? 100 mV is common.Did you ever hear about someone blowing a K1000 driver by using an old Marantz? I guess it was just coincidence. Don't get me wrong, something in the range of 100 mV is crap and should be considered as being defective.I would ask the Super T-amp manufacturer to send you an amp with better specs.I've just sent a speaker amp with 23 mV on one channel back to the lab for adjustment.I would adjust it myself if I had the schematics at hand, but the amp is under warranty anyway and the manufacturer agreed that more than 10 mV is unacceptable for a new amp and they even cover the shipping costs. BTW, the Tripath 2020 based amp I'm using in the meantime measures 2mV/23mV.

 

[bigcat39]

Heh, the only thing that those AKG's were ever driven with was a Cary 300SEI..... now I'm not saying anything here, but.......

 

[Trogdor]

Quote:

Originally Posted by bigcat39 Heh, the only thing that those AKG's were ever driven with was a Cary 300SEI..... now I'm not saying anything here, but.......

LOL