[gtube]

On page 19, ETAHL had sucessfully removed the two resistors to lower the little hum. He is enjoying with his Grado now.

 
Quote:

Once Garry figures out the hum--has he while I was absent???- it'll be fun trying different tubes and molding the sound...this is the fun part!!!

 

 

[ETAHL]

Quote:

Originally Posted by eclein /img/forum/go_quote.gif
 
How hard is the mod, I haven't soldered in years but just don't want to send this back to Canada through the endless customs bottleneck. Does it require special tools, screwdrivers etc..?? How hard is getting the case off??

 
I would not attempt it if you are not comfortable with soldering. No fancy tools is needed, but you do need some care and dexterity. Suitable soldering iron, tweezers and a probe to poke out the resistors help a lot.
Maybe get an electronics technician friend to have a go at it; it is not too hard to do.

 

[openreel]

There are very few electronics service shops left with today's disposable units, but you might consider a reputable car audio installer. They are always soldering and know their way around PCBs. A simple job that might cost only a few dollars or just lunch for the tech. Bring him the torx screwdriver though.

 

[gtube]

I will try to post a complete picture guide to remove the two resistors tonight. It is a 5 minute task.    

 

[Monday]

Garry will the revised version from the factory also be an inside switch?  It'd be great to switch between cans without disassembling the unit.

 

[eclein]

torx screwdriver????  whats that...LOL.....do I need the torx to get to the resistors??

 

[BmWr75]

Yeap, torx is a variant of phillips head or an allen wrench.  6 torx screws hold the bottom plate on, which must be removed to access the printed circuit boards.
 
Quote:

torx screwdriver????  whats that...LOL.....do I need the torx to get to the resistors??

 

 

[BmWr75]

I rolled tubes today.  Reissue Genalex KT-66s for power tubes.  NOS Jan Phillips 6SJ7WGT for drivers.  There is no hum at all driving Beyer DT-770 600 ohm cans.
 
This amp drives high impedance cans wonderfully!!

 

[Skylab]

No doubt, when you have a quiet set of tubes, this is one sweet spending amp for the money.

 

[gtube]

Hi Guys,
Here is the step-by-step modification guide for low impedance headphones users, such as Grado. or you want to lower the hum level when using noisy tubes.
 
http://www.musicalparadise.ca/mp/files/MP-301-MK2-Mod.pdf
 
Thanks,
Garry

 

[gtube]

The factory version will be exactly the same, internal mini switch only. It will be preset to 32 - 300ohm position for better compatability.

 
Quote:

Garry will the revised version from the factory also be an inside switch?  It'd be great to switch between cans without disassembling the unit.

 

 

[wotts]

Hello all!!
 
I've been listening to this amp with my T-1s and loving it thus far. I have the stock tubes in, looking to see what I can roll though. The T-1s sound good, a little low frequency hum at low volume levels, but when the music is playing I can't hear it. I have a few tubes on order to try out in it and really looking forward to the rolling. Thanks for a fun amp Garry!

 

[Rockyhill]

Hi Garry,
 
When you write "or you want to lower the hum level when using noisy tubes" is this for speaker applications too? Or just headphones.
 
Thanks,
 
RH

 
Quote:

Hi Guys,
Here is the step-by-step modification guide for low impedance headphones users, such as Grado. or you want to lower the hum level when using noisy tubes.
 
http://www.musicalparadise.ca/mp/files/MP-301-MK2-Mod.pdf
 
Thanks,
Garry

 

 

[ETAHL]

 
Quote:

Hi Garry,
 
When you write "or you want to lower the hum level when using noisy tubes" is this for speaker applications too? Or just headphones.
 
Thanks,
 
RH

 


 

 
The mod only affects the headphone out. You are modifying the headphone circuit.
 
I don't find noise to be a problem with my speaker setup, even with noisy tubes. A few feet away, the hum is inaudible.

 
 

 

[Rockyhill]

Got it.
 
Besides the stock tubes, I've used RCA and Tung-Sol 6SD7GT and National Union 6SJ7GT.
I thought the stock were a little lacking in the high end.
RCA and NU sound very nice sonically but the hum is not tolerable. NU also extremely microphonic. Garry advised they aren't compatible.
The Tung-Sol is better than stock, IMO, but I would like to improve that.