[lbj]

Quote:

Congrat on the MAD EAR+ !  I still enjoy mine very much. It's a very versatile tube amplifier that will drive and synergize well with low and high impedance headphones. Get yourself a nice Raytheon 5751 with Windmill Getter or GE 5* and sit back and enjoy!!

Thanks!  I do intend to roll some tubes.  Interestingly my kit came with a 12AX7, whereas most people seem to have received a 5751 iirc.

 

[MacedonianHero]

Quote:

Thanks!  I do intend to roll some tubes.  Interestingly my kit came with a 12AX7, whereas most people seem to have received a 5751 iirc.

Some other really good suggestions:
 
5751 Sylvania Gray or Black Plate Triple Mica (I slightly prefer the black plate)
12AX7 Genalex Gold Lion
 
 
 

 

[digic25]

LOL. I was still having a problem with my HD 2 until about an hour ago. Even after installing the ECC99 (as per Lloyd) power tube my amp still sounded horrible when raising the volume past half way. Even with the Auricap upgrade I was thinking of listing the unit back up on head fi for a loss. That was before I decided to take a risk and try a completely different driver tube. I installed a 6922 Sylvania in place of the 12AX7 and what a massive difference in sound. The unit is able to play the way it should when raising the volume, the bass is deep and clear, the highs are very crisp, and the mids have a nice unveiled sound.
 
One negative from doing this is that the tube looks to be heating up a bit more then it should, but it doesn't seem to be over heating any other parts or contributing to anything negative in the sound signature. It's really odd as I've tried to use the 6922 in place of the 12ax7 in past applications but it never worked. (Power tube is running at 190 degrees and the driver at 150 degrees)
 
Looks like my situation was a real oddity with this amp as everyone else seems to be fine.

 

[lbj]

Quote:

Some other really good suggestions:
 
5751 Sylvania Gray or Black Plate Triple Mica (I slightly prefer the black plate)
12AX7 Genalex Gold Lion
 
 
 

The Sylvanias and GE 5-stars are on the short list, they seem to be inexpensive and plentiful on ebay.  I'll look into the Gold Lion.
 
Phase 2 is power and input/output wiring.  Got through a portion of the work tonight.  Power trannies are wired up, and since I won't need to touch them again, the cover can go on.
 


 
Not worth putting up a pic of the interior since it still looks a bit bare, but that'll change tomorrow.  More pics to come!
 

 

[replytoken]

Quote:

That was before I decided to take a risk and try a completely different driver tube. I installed a 6922 Sylvania in place of the 12AX7 and what a massive difference in sound.

You might be taking a risk.  Is it safe to substitute a 6922 for a 12AX7 in your amp?  You might want to get some independent confirmation on that before you have a (possibly dangerous) mess on your hands.  It took an experienced local technician to identify and correct an error that Lloyd made while working on my amp.  He is a nice guy, but he is not infallible.
 
--Ken
 

 

[lbj]

Finished Phase 2 today, except the soldering on the Alps pot, I have a question for Lloyd regarding the pinouts.  A lot of today's work was difficult, lots of little fiddly bits that were hard to get at because space was tight.  Everything worked out though. Now it's starting to look like an amp!
 

 

[diego]

@digic25
 
You can´t use a 6922 tube in the HD2. The heaters on that amplifier work at 12.6v and the 6922 works at 6.3v. You will surely ruin your tube in a short time.

 

[lbj]

Phase 3 is the amplifier circuit.  Got through about half of it today.  Put in a lot of resistors and capacitors, as well as the output transformers.  Getting close to the end now, should be done sometime over the weekend.
 

 

[Petyot]

Phase 3 is the amplifier circuit.  Got through about half of it today.  Put in a lot of resistors and capacitors, as well as the output transformers.  Getting close to the end now, should be done sometime over the weekend.
 

Thanks! I enjoy to follow your work progress.

 

[lbj]

Thanks Petyot!
 
I finished the amp this morning!!  Just had to add a couple more capacitors and several more wires.  Voila, an amp is born.  Here's the last shot of the innards before I button her up:
 

 
With some trepidation I turn it on for the first time, without any input signal or headphones attached.  I watch closely for the fuse to blow or something to billow smoke.  None of that happens, so far so good.  I watch the multimeter read voltage rising to 200, 250 volts, good good, wait what's this, it's going back down to 220??  And staying at 220?  According to the instructions, this particular reading is supposed to settle at around 300.  Hmm, now I'm a little worried.  Plug in a source and a set of cheap headphones (old Sennheiser 545's if you must know), and ahhhh, all the worries are gone.  Sweet, sweet MUSIC.
 


 
I'm going to go listen now, talk to you later....
 
 

 

[digic25]

Thanks for the info on the tube voltages. I've been through a slew of NOS tubes from various manufacturers (12ax7's, 12au7's, ECC188C's, 6dj8's and 6922's) and I still find that the 6922's provide the best sound.
 
Are there any mods that I can do myself to lower the power going to the heaters of the 6922. Even if the tube lasts me 1000 hours (out of 10000 i think) I don't mind as long as no other parts are affected.
 
Regards,
Thomas

 

[Petyot]

.
 


 
I'm going to go listen now, talk to you later....
 
 

Nice! I wish I could do that kind of DIY project...

 

[eucariote]

^ very nice looking amp. 

  The natural color panels look great.  Now it's time for tubes!  I'll re-post the picture from my tube search..  I've acquired even more, but have settled on the very left tube (Raytheon WMG) and variations of the 6th tube (Sylvania TMGP).

 

[Armaegis]

Mmm... I want one...

 

[lbj]

Hmm, well... After several hours of (stellar, gorgeous) play the amp's right channel died.  It didn't just abruptly cut out, but faded away over the course of a second or 2.  I tried swapping the right and left tubes, but no change.  It's too late in the evening to attempt any more troubleshooting, so I'll open it up tomorrow.  Of course, I sent Lloyd an email asking his advice.  Hopefully it's as simple as a bad center tube.  We'll see.