Edited by mvrk10256 - 7/20/13 at 5:43pm
Thanks! I ordered all the stuff I need from Mouser for the mods so that should be up within the week.
FWIW, I thought I would add this data to your Bravo tube rolling thread.
So I've been flipping my setups around just to play with things. I'm the curious sort I guess. I decided to tinker with this Pure i-20 a bit more, and it's probably been too long for me to return it. Anyway... the "normal" setups I have for home and work go something like this:
Work: iPod -> (Pure i-20 DAC) -> Bravo V2 -> Sony MDR 7506
Home: Laptop -> Schiit Modi -> Schiit Magni -> Beyerdynamic DT770/250
The setups sound different, but both sound good. The Pure i-20 is the newest addition; it is BRIGHT. Maybe even harsh. I am finding out I can't turn the volume up a lot, or I need to take it out of line and run the iPod directly into the Bravo. Aside from the brightness, it is bringing some unexpected clarity to what I keep calling my "cheap" work setup. Anyway, so I decided to do some tube rolling, and switch this around. Since I can't tube roll at work, I brought the Bravo home and changed the home setup to this:
Home: Laptop -> Schiit Modi -> Bravo V2 -> Beyerdynamic DT770/250
The bottom end on the Beyers went away with this setup. That was a little surprising, given how much headroom the Bravo's volume knob usually has. I presume this was an impedance thing, so I switched out the headphones to the work cans:
Home: Laptop -> Schiit Modi -> Bravo V2 -> Sony MDR 7506
This brought the bottom end back. I was also a little shocked that the Sony's were sounding better than the Beyers on this setup. The MDR 7506's have an impedance of 63 ohms, which seems to work a lot better than the 250-ohm Beyers (and I'm now also kind of curious how 32 ohm cans would sound, but I digress).
So now that I had my tube rolling setup determined, I started a-rollin'. And a rollin, lol. I'm sure someone will laugh at me for blowing a pile of money on 12AU7 tubes to roll a Bravo V2, but there you go. As I mentioned earlier in another post, my family life has been going whacky for the last month or so, so I guess I really needed a distraction from the grief. Besides, it keeps me off the streets and out of trouble. But I digress again. I'll discuss the tubes in a moment.
So because I didn't want to keep carting around my tube rolling setup, I decided to take the other parts to work. So my work setup temporarily turned into this:
Work: iPod -> Schiit Magni -> Beyerdynamic DT770/250
Now, this was a real shocker: the Beyerdynamic cans sounded just as bad as when I was trying to drive them with the Bravo V2. For some reason, the Magni was no longer driving them properly. Ok, the Magni was being driven by an iPod, but can the DAC in an iPod really be that bad? I guess it is. I did not try the Pure i-20 on this setup. I suppose I should have, but I had it parked and out of the way for the moment. Someday curiosity may get the best of me, but I didn't go there for now. Suffice it to say that for a few moments, I resurrected my Sony MDR NC-40's and ran them with the iPod. Then I remembered why that was a bad idea. So this work setup didn't last long. I briefly flirted with the idea of buying another set of cans. Bleh, not now. Spent too much on tubes for now.
So back to the tubes. My music selection is probably smaller than others. But I have some nice selections, and I decided on a selection of tunes that I am now calling my Test Music. The primary selections from the library I use the most (song names eliminated for space):
- Apple Lossless -
Andreas Vollenweider: Book of Roses
Pat Metheney: One Quiet Night
Peter Gabriel: So
- Apple 256 Kbps AAC -
Led Zeppelin: Celebration Day (Live At O2 Arena, London)
Lindsey Stirling: Lindsey Stirling
Seether: Finding Beauty In Negative Spaces
Seether: Holding Onto Strings Better Left to Fray
The 12AU7 tubes I've tried:
GE 5 star 5963 (mil spec 12AU7)
Telefunken x 2 (long grey plate)
Tung Sol x 2 (long grey plate)
Westinghouse clear top (long grey plate)
Westinghouse yellow label (long grey plate)
IEC Mullard (I think this was a short grey plate)
Amperex Mullard (long grey plate)
Conn rebranded, not sure what the original is (long black plate)
Sylvania green label (mid size grey plate)
Sylvania yellow label (long grey plate)
GE white label (short grey plate)
Olympio tv tube (long grey plate)
Baldwin organ tube (rebranded Sylvania, long grey plate)
JJ Electronics new, not NOS, from Amazon.com (short grey plate)
Electro harmonix new, not NOS (short grey plate)
...and of course the original chinese tube
(and I still have a few more to test including a couple of the better Mullards)
I'm not going to torture you with a blow by blow description. I think it's probably more important to point out the lessons learned:
1) Unless you need a distraction like I did, it's probably not worth spending this much money to tube roll a Bravo V2.
2) The newly made tubes from JJ Electronics, Electro Harmonix, and the stock chinese tubes really do suck. Not by a whole lot, but it is a noticeable difference. I would sooner throw them in the trash then listen to them. I would only use them if they were the last tubes on Earth.
3) Long grey plates sound better than the short grey plates. Brand doesn't matter.
4) Black plates of any length, seem to sound as good as the long grey plates. Brand doesn't matter.
5) Sometimes people sell tubes on eBay because they are worn out. The first Tung sol tube I bought that really got me going on this, had a background hum that has never gone away. I am now assuming this is because the tube is worn out or defective in some manner, and the jerk who sold it to me on eBay really should have thrown the damn thing away. Instead, he made $12 bucks and screwed me. The second Tung Sol tube I tried did not exhibit any hum. I've heard a little hum from one or two of these tubes, but nothing too bad.
6) Telefunken tubes really are nicely balanced and pretty sounding, especially with music like Andreas Vollenweider. Even on a Bravo V2. But I find that I actually prefer other tubes, unless I'm listening to a particular type of music. Don't spend the money on them unless you really know you need to, or you get a good deal.
7) Newer Mullards like the IEC Mullard I tried, aren't worth spending a bunch of money on. Don't bother.
8) Tubes newer than the 1960's should be avoided if at all possible.
9) Rebranded tubes sometimes sound pretty good, but sometimes they don't. Examples: The Conn tube sounds pretty damn nice, but the Baldwin/Sylvania is leaning more towards the quality of the new JJ electronics crap. Don't spend a ton of money on rebranded tubes.
10) The mil spec 5963 tubes sound damn nice with gritty rock and roll like Seether. I'm really liking the GE 5-star 5963 tubes I found (got a pair for cheap).
So for now things are back to where they started, and I'm back to using the Pure i-20 at work. It is bright, but it brings a certain quality to the music stored on the iPod that I am finding that I like. I just have to remember not to crank it up very high. The side effect of this is that when I get home, my Magni+Modi stack on my Beyer cans sounds a little flat. Not tubey at all. I am now kind of disappointed in this development. I am also wondering if I'm just turning into a tube guy, and maybe I need to get a Valhalla+Bifrost for home instead, LOL.
I guess once you roll tubes, you don't go back?
It actually LM317AT
Sorry for my ignorance but I was wondering if the FETs were the silver heatsinks? I found a diagram here http://i30.photobucket.com/albums/c306/oohms/bravo12au7/shem.png but I just wanted to be sure. Sorry for the bother and thank for your help! :)
Excellent write up! I had the same experiences with my mods, fets made all the difference. This amp got me started in tube sound and indeed there is no going back for me. My bravo hasn't been used in over a year but I can't bring myself to part with it :)
At long last, this weekend I had some time to start on modding one of my Bravo V2 amps. Some pics and notes to follow (please see notes at the end)...
Here's a shot after removing the IRF630's, the LM317's, and the input+output capacitors...
The first component removed was one of the IRF630's. I have a decent Ungar 42 watt soldering iron that I've had for years. I read that some people had difficulty de-soldering components due to the lead-free solder used on the original. I had the same issues. I probably damaged one of the reverse-side circuit traces on this component for this reason. Note in this picture that solder extends to both sides of the circuit board, which just makes things that much more fun...
So after the first attempt, I went back online to read some more. I found a couple posts that gave me the best suggestion yet: before attempting to remove anything, re-flow the original solder joint using leaded solder. After doing this, I had a much easier time removing solder from the leads. However, I still had to improvise, which I will detail further below.
In the case of the LM317 below, I had to actually remove the heat sink, in order to get to the leads of the device (so I could cut them). The reason for this will be detailed at the end of this post.
A bottom view of the circuit board after removing several components. If you zoom in you can see the damage to the circuit trace on the upper left solder connection.
So here I want to summarize several important lessons learned, for anyone else who is going to attempt these mods to their Bravo:
Finally, I should mention that one should not attempt this exercise unless you're willing to lose the whole amplifier. It became clear to me that I might not figure out how to pull these parts before destroying something, that I could not repair. I was glad I stopped in the middle, to find the hint about re-flowing the solder. That made all the difference.
And, please, don't ask me to modify yours LOL. After going through this, I can really see why nobody wants to do this for anyone else.