[Joseph Lau]

Hi ! I had a Experiement on MG_Head of modify it to become a Choke Load OTL Headphone amplifiers. It become more bass , more open , better sound stage. It is very easy :

Just remove the nfb loop (R5,C3 , R6,C4) and connect a 100/160V Capacitor to Plate of VB2 and VB3 (6BQ5) . It can drive Headphone 100 Ohm or over. You can keep the Transformers couple function by add a Headphone jack for OTL out or use 1 of Headphone jack for OTL and 1 for Transformer out. (It had 3.5mm Jack and 1/4" Jack).
The original high/low impedance switch can use for nfb control. (Connect or disconnect).

 

[rickcr42]

Thanks for the tip Joseph,I look forward to experimenting with this amp (soon) and the headphone transformer should also be fun.It is soo cool when the "big boys" share

 

[Daniel Pumphrey]

I would like to hear about how this actually sounds. It would be recommended to get the best Cap you can afford though. What size Cap are you going to try? This would be a great mod for the manufacturer to try also. It could be activated with a DPDT switch too. This would be good for use with high imp phones and just might make the MG into the best of both worlds.
Dan

 

[Joseph Lau]

I had try 100/160V Nichicon Cap. It seem to be good at this purpose. I also parellel a 1/450V Infinite Cap on it . It frequency response from 15Hz to 50Khz +1db at 200 Ohm Load. Yes ! A DPDT for Switch Between OTL and Transformers coupling is good idea to keep transformer coupling in Low impedance. It also can use a PARAFEED COUPLING TRANSFORMERS TO GET BETTER BAND WIDTH WHEN USE LOW IMPEDANCE HEADPHONE.

 

[jim]

Please forgive my ignorance, but I'm just getting started with this tube stuff. I'm planning to buy an MG Head or the Opera pretty soon, but don't understand what you're talking about really with all these different designs.

Here is what I think you guys are saying so far...output transformers are used to match with low impedance headphones, but it would be nice to avoid their use if possible because they aren't easy to implement well. OTL means the amp is transformerless? So that would mean OTL amps only match well with headphones of large impedance? So if I wanted an amp to match with my etymotic 4s's, I would want...?

Also, what is the advantage of a SET (single-ended triode? ) amp?

Again, please excuse my questions if this is simply common knowledge. I'm a newbie...have mercy!

 

[Budgie]

Thanks for the information, Joseph. I think it is very nice of you to share your knowledge with us and I really apperciate it. I will give the simple OTL connection a try on my Asusa K2003 amp, when I get a chance. (It is a single ended 6BQ5 design also.)

 

[rajan]

What would be a good online document which can introduce a beginner to a world of tubes (definitions, how-to's, etc.)?

(Sorry Joseph for hijacking the thread).

 

[jim]

Yeah, sorry to mangle this thread with those questions. I should have posted it as a new thread. Could one of the moderators remove my response from this thread and stick it in a new one? Thanks.

 

[Joseph Lau]

Thanks for your idea very much. I will have more time to work on document very soon.


Quote:

Originally posted by rajan What would be a good online document which can introduce a beginner to a world of tubes (definitions, how-to's, etc.)? (Sorry Joseph for hijacking the thread).

 

[RGA]

Okay Joseph.

I am electronically challenged. This will be the first tube amp I've ever owned...one reason it scares me a bit is that it seems if you don't have an electrical engineering degree you could be in for trouble.
But then owning one is a good way to learn

Unfortuneatley, everything you guys are talking about went over my head. You have a modification that will improve the sound for High impedence headphones...That's me...I have the HD600s.

Do I need to solder anything? LOL have not touched a soldering Iron in more than 10 years

First step is getting the amp...which is going to take a little while.
Having documented instructions on modifications is a terrific idea...especially for beginners like me.

Thanks.

 

[Joseph Lau]

Yes ! It is an Good Idea to write a Modification note on MG-Head ! OK ! I will work on it soon. Will be post a meaasage to this board when ready ! Bye !

 

[BP1]

I bought my new AKG K501, and I'm looking for an amp for it. Anyone can tell me where I can buy the MG Head in HK? And Joseph did OTL mod on MG Head, can Joseph do it for me? Or other good chice than MG Head?

Thanks.

 

[Joseph Lau]

Sorry ! We can not direct sell ! Due to we can not provide after sell service if I direct sell to end user. Please Phone to HK telephone no - 27251012 from 1:00PM to 8:00PM . He is our HK distributor.