[dogwan]

I'm fairly new to headphones and a few months ago I bought an ASL MG Head OTL on a whim for a song. With extra tubes and all. I just needed some good cans to go with. After some back and forth I finally settled on a pair of Beyer DT-880's.

Now I don't actually listen to this set up very often and after a few months I'm thinking the Beyer's are finally getting broken in.

A couple weeks ago I got curious and opened up the ASL (I'm a constant tweaker) and what do I find? A pair of really cheap 'lytics coupling the OTL output. In the middle attached pic you can see them in the lower right corner. These are the same as the ones used in the PS. Certainly I can do better?

Luckily I was compiling a Mouser order for other projects and threw on a couple of Nichicon KZ Muse series. Same value but a little lower voltage. I'm just shooting from the hip but I don't think I'll be seeing 160v on the output here.

3rd shot is of the Muses installed.

How does it sound? Well I've got about 10 hrs on the caps and it's definitely an improvement. The 1st thing I noticed is that the noise floor dropped dramatically (OTL output only), and bass is better defined. The longer I run it the smoother it seems to get. I know the DT-880's are known to be a little forward in the upper end but in OTL mode I've noticed a marked improvement in the resolution here. Caveat: I've been a cabinetmaker for 17 yrs and I've probably lost some of the higher octaves.

I don't have much else to compare it to but I really like this set up. The OTL mode to me is where it's at! Now I'm trying to figure out how else I can improve this amp.

-Dogwan

 

[archosman]

I've still got mine. First amp I ever bought.

 

[Born2bwire]

You should really replace the mains line that runs to the switch with a shielded line. It runs right by on of the tubes and causes a bad hum in on of the channels.

 

[dogwan]

I have some shielded wire w/ drain that I can use. And the afternoon free.

Do you have personal experience with this amp? If so other mods you have done?

-Dogwan

 

[Born2bwire]

Quote:

Originally Posted by dogwan /img/forum/go_quote.gif I have some shielded wire w/ drain that I can use. And the afternoon free. Do you have personal experience with this amp? If so other mods you have done? -Dogwan

Yeah I had one, my dad has it now I believe. Decent little amps but bad quality control and the North American distributor is horrible, but the amp creator seems ok. The final version finally got the power supply right by moving it off of the amplifier to a separate unit. The biggest problem is that the unshielded mains goes from the outlet in the rear to the switch in the front while passing by one of the tubes. A lot of people get a hum from this and replacing it with a shielded line can remedy this problem. I also had the volume pot replaced because it was unbalanced (I had to pay for this because the distributor claimed it was fine, seriously they are horrible). I can't remember what other mods were done, I think the caps were replaced and maybe the tube seatings replaced as well.

I had great sound out of some Mullard EL84's and Raytheon Blackplate 5751. Don't think you can find the Raytheon anymore without mortgaging your house though.

 

[dogwan]

I agree about the quality under the hood. I did put in some shielded wire for the mains last night and it did drop the noise floor a little bit more. Makes me want to gut it and do a complete rewire.

While I had it open again I did some more serious poking around and sure am glad I didn't pay much for it ($108 +shipping/Ebay). While it does have good sound I took a serious look at the hardware and it's pretty chintzy. Knock off ALPS clone for a pot? Really? The Blues' are not that expensive in bulkl! And the same caps in the PS and to couple the OTL output? All in all it seems to be assembled from all cheap Chinese junk, maybe the better Chinese junk, but still cheap.

But it still does sound pretty good.

BTW, I'm currently running Magnavox branded Mullards EL84's pulled from an old console and a NOS JAN Philips 5751 for the driver. Very fluid.