Support Head-Fi.org by
starting all of your
Amazon.com shopping by
clicking here.
____________________________________________________________________
Today's Featured Head-Fi Blog: Jude's Blog
____________________________________________________________________
Please help
support Head-Fi by becoming a Contributing Member
CLICK
HERE -- Contributing Members, thank you
for your generous support! --
Are you planing on getting someone to make the front panel for you? That size of a chassis will give you plenty of room to work with and as you said, you'll have the room to upgrade to a better circuit in the future. Good idea about putting the pot and the selector switch in the back to keep the signal wire as short as possible. Here's a place that has some nice wood knobs BTW:
Guess I'll post some pics of what I'm planning as well:
I'm trying to find something nicer to use for a transformer cover. I found a nice brushed stainless steel jar that would work, but it's 5" diameter which is a bit to big. The shortened camping cup in the above pics is 4" diameter and is the perfect size, but would have to be painted and I'd much rather use something SS. To give a cleaner look I'm going to fabricate a new top panel out of aluminum to cover the vent slots and the socket mounting screws. I cut the bottom flange of the cover off last night so it can now be removed from above instead of having to slide on from the back.
This entire thread has been a very interesting read, but these modifications lead me to make a comment...with all due respect why didn't you all just build a Morgan Jones? You can purchase inexpensive pcb's for the MJ from China and it would have saved you a great deal of time, effort, and money.
__________________ Former Headphone Rig: Sony SCD-CE595 (modded) > Kimber PBJ > DIY P2P SOHA (w/ JJ 12au7) or DIY Morgan Jones Headamp (w/ Mullard 6x4 and JJ 6922's) > HD-650's w/ Zu Mobius
"Human being and fish can peacefully coexist." - George W. Bush
This entire thread has been a very interesting read, but these modifications lead me to make a comment...with all due respect why didn't you all just build a Morgan Jones? You can purchase inexpensive pcb's for the MJ from China and it would have saved you a great deal of time, effort, and money.
The 708B is the first tube amp that I've owned and I knew that it would probably need a lot work to get it to its best, but that's exactly why I bought it. If I was just looking for a good tube amp then building a MJ would've been the way to go as you said, but my intent was to further my electronics knowledge through doing extensive mods to a cheap commercial product. The amount that I've learned about tube circuits while doing research for the mods was worth the price of the amp alone to me.
I've decided not to do the case mod or the MJ mod to the 708B as I'd much rather save those efforts and money for other amp projects. While I'm pretty happy with how this amp is now, I'll probably end up selling it eventually to fund bigger and better projects, which will be fully DIY by the way. So no offense taken and hopefully you see were I'm coming from.
This entire thread has been a very interesting read, but these modifications lead me to make a comment...with all due respect why didn't you all just build a Morgan Jones? You can purchase inexpensive pcb's for the MJ from China and it would have saved you a great deal of time, effort, and money.
My thoughts exactly except I thought the MJ had to be point to point because no one made PCB's, where are you finding the PCB's ?
I finally got in my Westinghouse 6X4 rectifier tube today. So I got the old soldering iron heated up and started on the process written up by dcheming on page 2 of this thread. Thanks Derek!
Everything went super smoothly and I was done in about a half hour or so. The amp's been up and running for nearly an hour now with no problems, and the heater voltage is at 6.92V. Just as a reference, the stock 6Z4 heater ran at 7.09V.
Now for some pictures... naturally.
First off, I wanted to make note of this, as it was (and still is) a pleasant surprise to me as I'm sure it will be for others here on the forum as well. The Westinghouse 6X4 rectifier tube is slightly SHORTER than the stock Chinese 6Z4 tube! This means that people CAN do this mod and still put the lid of the amp back on without a problem!
Here's a pic of the unmodded socket.
Here's both the pins desoldered, rebent, and the one pin moved over one space. Also, the corner of that one trace has been scraped away.
One of the jumpers. I only took one picture since these things are very unexciting.
This is the first jumper installed.
And the second jumper.
And one last pic of the new 6X4 glowing away.
As of yet, I really can't pin-point the difference in sound I'm hearing, other than it seems as if the amp is "stronger" sounding. It's hard to describe. It definately didn't hurt the sound at all, that's for sure. I'll get back to the sound in a day or so when I've had a little more time to listen to the amp with several different CDs.
How about you Derek? Any new views on the sound of your amp since the 6X4 mod?
__________________
HOTT Modded Xiang Sheng 708B Sennheiser HD600 Sony CDP-397 CD Player FEEDBACK My NEW Website!
For those who are modding the rectifier to 6x4, I have tried a number of NOS 6x4's in my MJ and a NOS Mullard 6x4 is absolutely the best. Highly recommended and long lasting.
__________________ Former Headphone Rig: Sony SCD-CE595 (modded) > Kimber PBJ > DIY P2P SOHA (w/ JJ 12au7) or DIY Morgan Jones Headamp (w/ Mullard 6x4 and JJ 6922's) > HD-650's w/ Zu Mobius
"Human being and fish can peacefully coexist." - George W. Bush
As of yet, I really can't pin-point the difference in sound I'm hearing, other than it seems as if the amp is "stronger" sounding. It's hard to describe. It definately didn't hurt the sound at all, that's for sure. I'll get back to the sound in a day or so when I've had a little more time to listen to the amp with several different CDs.
How about you Derek? Any new views on the sound of your amp since the 6X4 mod?
As you said it's kind of hard to pin-point what the difference is, which is why I haven't really said much about it yet. I agree that the amp does sound a bit stronger now with the 6X4 and listening to music such as Thievery Corporation and Bjφrk makes me feel that it generally sounds more "open" as well. There also seems to be a bit more snap to the sound now. I'm looking forward to installing those Vishay-Telefunken SF4007 diodes as well, hopefully they'll help a tiny bit more.
I finally got a replacement 6N3 by the way so I finally now have all nice tubes under the hood. I have all the PRP and MILLS resistors as well as 4 gold plated sockets coming from PC and I can't wait to get them installed.
I'm glad the mod went smoothly for you. That's quite a surprise that your 6X4 is actually shorter than the 6Z4 considering how tall mine is. I should be able to make mine fit under the case too, but it will be pretty close. On a side note I haven't had any problems with the transformer overheating even with daily use for multiple hours, but I still feel it every now and then just to be sure.
For those who are modding the rectifier to 6x4, I have tried a number of NOS 6x4's in my MJ and a NOS Mullard 6x4 is absolutely the best. Highly recommended and long lasting.
I'll have to get a NOS Mullard 6X4 to try then. Thanks for the recommendation.
It definately didn't hurt the sound at all, that's for sure. I'll get back to the sound in a day or so when I've had a little more time to listen to the amp with several different CDs.
