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Bravo Audio - funny looking little tube amps - Page 173

post #2581 of 2599
Quote:
Originally Posted by Coolmeadow Kid View Post
 

No top on mine at the moment either.  I built an Oak piece for it to sit in, and I incorporated an 80mm computer fan in the top blowing down on it.  After playing for over an hour, the heat sinks were cool to the touch.  So that was a good thing to find out.  Now, if it should have some heat build up to work properly, I might need to reduce the speed of the fan.  I didn't hear anything that would make me think it changed the sound though.  Have any thoughts?

I'm anxious to get the 2 RCA clear tops I ordered Sat. night to see if they will rival the Balwin/Raytheon long black plate that I have settled on as my best tube so far.  Then I think I'll see about doing some of the mods.  Jim.

 

Well, if you're using a computer fan, likely it's running on a DC power supply. That ought to produce less noise, if any. I use a Thermaltake USB fan, and I do not hear any RFI noise as a result of placing the unit behind my amp. (I don't remove the top of my stock amp for cooling purposes - the fan blowing from the rear is sufficient).

post #2582 of 2599
Quote:
Originally Posted by Coolmeadow Kid View Post
 

WOW!!! WOW I Say!!!!  Just got 2 RCA clear tops in today.  I was leery of trying them after the long grey plate RCA I got on my original order was the least of the 3, and these are short plates instead of long plate, but I decided to follow what so many said about them as I re-read the thread last weekend.  Put the least balanced one in first (2800/2900) and I can't make myself pull it out to try the other one (2800/2800).  First few seconds, I thought it had potential.  Left it playing and came back a few minutes later and the mid-range sounded real muddy, almost distorted.  So I left it and took 3 short classes for work and came back to them. WOW!!!!!!!  It may never leave the amp.  I may just file the other one away somewhere safe in case this one dies on me! Tempted to try the two military long black plate Raytheons since I like the other Raytheon I have.  If you are on the fence about the clear tops, jump, NOW!  Jim.

 

Hahahaha nice ;) Yeah, its kind of amazing how much improvement you can get just by rolling tubes in the stock amp. I've been posting about that for about the last year.

 

Now if you rewind about a year and read how many tubes I ended up buying and rolling through this little amp, you'll probably get a good laugh. Or maybe just understand why I did.

 

What I'm still kind of curious about though, is the loss of bottom end on the modified amp. Not sure what to think about that yet. I may end up changing the output caps back to better quality 1000 uF units just to see what happens.

post #2583 of 2599
Quote:
Originally Posted by Coolmeadow Kid View Post
 

OK, a question. Scenario: I built a housing for my Bravo V2 with an 80mm computer fan in the top blowing down on the unit, top acrylic panel removed.  After 1 1/2 hour of playing music, the heat sinks were not even warm. Do some of the components need heat to work properly, or will keeping them at room temperature extend the life of the components with no degradation to sound?  I just want to make sure I'm not hurting anything.  Thanks!  Jim.

 

The only component that requires heat to run properly, is the tube. Part of the reason for the short delay on startup of a tube amp, is for the heater within the tube to reach operating temperature. That happens pretty quickly (10-15 sec), so the circuit kicks in and starts producing sound after that happens.

 

That being said, I don't think you could cool it enough with the fan setup above to degrade tube performance. I didn't go to quite the same effort to cool mine - the fan I linked above stands alone behind my amp (I use two of them, one for each amp), and I keep the output control set to about 2/3rds. Thats enough to bring the heat sinks down to a temp that allows me to touch them while operating. So mine probably operates somewhat warmer than yours does. Just get some air moving over the amp seems to be plenty.

 

I think your setup is pretty awesome (even if it was a quick job), but it's probably overkill... for those considering a fan, the aforementioned Thermaltake USB fan is probably plenty (and it keeps my modified amp cool also, with the stock heat sinks).

post #2584 of 2599
Quote:
Originally Posted by Coolmeadow Kid View Post
 

Thanks man.  It was a quick and dirty project.  Didn't even worry about hiding the air nail holes!  All left over Quartersawn White Oak from another project.  No plywood. Don't know about the static issue.  My computer doesn't affect it, and the fan doesn't make any noise in the amp.  I need to hook up my RF unit to the amp again and see if the pop noise is still present.  It would pop if I stood between the transmitter and receiver, but go away when I sat down beside the unit.  Thought that was weird.  Never had a cell phone next to it. Microwave and 2.4 hz cordless phone system in the house hasn't affected it  I've thought if it did I could line the inside part of the housing with foil to see if that might help.

 

 

razor5c    Thank you for confirming that.  I'd like to do the mods, but I may wait.  If the fan keeping the components cool might extend their usable life, I'll go with that for a while.

 

Have a good weekend!  Jim.

 

My bravo's are both susceptible to RFI. The only thing I keep near mine that causes noticeable RFI is my cell phone. I can tell when I have an incoming phone call or text, because I start to hear curious noises, lol :basshead:

 

I'm sure that occurs for lack of any shielding on the amp.

post #2585 of 2599
Quote:
Originally Posted by Troppo View Post
 

Hi Head-Fi.org,

I joined up as I am having an issue with the Bravo V3 I recently purchased. This thread has helped me diagnose some of the issues but so far I haven't seen anyone with my exact problem. Hopefully someone can provide some guidance!

 

My amp has been cutting in and out on occasions, when it does I get a pop in my headphones followed by crackling and a reduction in volume. When this happens I notice the following :

 

-> Red LED flickers.

-> Bias voltage climbs above 14V on both channels (climbs to about 20V temporarily).

-> If I blow air in the direction of the MOSFET's the sound eventually comes back and the bias voltage returns below 14V. Not sure if this is just coincidence or not, the temps are not abnormally high.

 

My tube was originally biased at 11.5V on the left and 10.1V on the right, based on this thread I then adjusted the bias voltages to 13.5V as recommended  which seemed to make the problem more frequent.

 

Whats going on here? Any ideas?

 

I checked the voltage across the LED and it was about 1.8V from memory so I don't think its bad??

I have reduced the Bias voltage back down to 11V to provide more headroom to the above 14V cut-out issue, is this going to create a problem?

 

Thanks in advance,

Nath.

 

I don't own a V3, but I would suggest adding a cooling fan - especially if it seems to make the amp work.

post #2586 of 2599
Quote:
Originally Posted by briancvrrbs View Post
 

I've already modified my Bravo V2 amp with IRL510, LM317A, and 5k trim pots. I was told that the MOSFET heatsinks would all get a bit hotter but I'm a bit worried at the amount of heat it generates.Is it normal for the IRL510s to get so hot? I also noticed the tube has gotten a bit hotter (I've set the bias on each channel to 13.5V) I can touch the MOSFET heat sinks for about two seconds until it feels like it burns and about five seconds for the tube.

 

I haven't attempted bias mods on mine yet.

 

Every thread I've read on modding includes the caution that the FETs will get hotter. Some people use bigger heat sinks, some mount the chips off the board on huge heat sinks. I'm just not that ambitious. I prefer to use that Thermaltake USB fan. For $11 bucks its the cheapest easiest fix, and doesn't introduce any noise that I can detect.

 

Not sure why the tube is hotter, unless perhaps it's just proximity to everything else being hotter. But the little fan would put that all to rest.

post #2587 of 2599
Quote:
Originally Posted by briancvrrbs View Post
 

I definitely see the improvements that came with these modifications though so I'm really liking them :beyersmile:

Also, should I do that crosstalk mod even if I'm not really bothered by it? Well, I actually havent searched for the crosstalk as I use the 3.5mm output instead of RCA

 

I have mixed feelings about that mod. I could not hear a difference after performing that mod. And I had already replaced the FET's and caps by the time I did that one.

 

The only mod that has a really noticeable impact is replacing the MOSFETs. The rest of them seem rather subtle.

post #2588 of 2599
Hello all,

I've been a V1 owner for about a month now and I've rolled about a dozen tubes so far. I've balanced the left-right pots to ~13.5V. Two quick questions:

#1 Is it normal that the blue LED remains lit after powering off the amp?

#2 I get a slight buzzing in my left channel when music is not playing. It's probably there while music is playing too, but gets drowned out by the other sounds coming through. What component causes this and any recommended fixes?

BTW, some tube notes: my favorites are a 1970 Amperex orange globe A-frame and a 1985 6N23P Voskhod Rocket logo, ECC86 works in this amp, ECC85 does not work
Edited by rwpritchett - 7/22/14 at 9:05am
post #2589 of 2599
How long dues the LED stay on? A few seconds is normal while power supply caps discharge.

I found that hum or buzzing can be from nearby electronic devices. Try moving the V1 around to find the best spot. A bad cable could also be the problem.
post #2590 of 2599
The LED stays on for a few minutes. Maybe 5 min? I think the LED drains the caps eventually and that's the only way to get it to go out. If I take the tube out after turning the amp off the LED turns off, however the thing will stay charged: If I put the tube back in, say 24h after being turned off, the blue LED will illuminate until it discharges everything.

For the buzz, it's not from an electric device as I've used the amp here, there, and everywhere and it always has it. Maybe the switching PSU is to blame?
post #2591 of 2599
Ok, now that I'm home, I timed it and the blue LED remains on for over 10 minutes, slowly dimming as it drains whatever power is feeding it.

I take it this is abnormal?
post #2592 of 2599
Quote:
Originally Posted by rwpritchett View Post

Ok, now that I'm home, I timed it and the blue LED remains on for over 10 minutes, slowly dimming as it drains whatever power is feeding it.

I take it this is abnormal?

I'm home now also and It's definitely not normal. Mine is a V3, the same except for the EQ, stays on only briefly but goes dim quickly. Maximum 5 seconds.

I would now tend to believe your hum problem and the LED are related. I would guess that the external power supply is not the culprit or you would have heard the hum in both channels.

 

Have you done any mods yet? if not... replacing the power caps would be a good starting point for your repair and simultaneous mod.

post #2593 of 2599
No, haven't done any mods yet. I don't have any experience in electrical de-soldering or cap replacement. I wouldn't know where to start in tracking down what makes that LED stay on after turning off. Anyone familiar with the PCB traces?
post #2594 of 2599

The amount of time the led runs really depends on the amount of capacitance in the power supply and the current the LED consumes.  What power supply are you using?

post #2595 of 2599
Quote:
Originally Posted by rwpritchett View Post

No, haven't done any mods yet. I don't have any experience in electrical de-soldering or cap replacement. I wouldn't know where to start in tracking down what makes that LED stay on after turning off. Anyone familiar with the PCB traces?

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