[Cirric]

Hi L&Gs. My first Bravo V3 started to make a pulsing noise in the left channel. Told the factory and their tech said to turrn the yellow trim pots until sound improved. It did not. Background hiss got steady and louder in the left channel. Bought a seconf unit from eBay. same problem within minutes. Also the LEDs started to pulse as well. Thought it may be overdriven by the ROKU. Used a 1/8" cable with a volume adjuster. Still no joy. But now I have a unit to play with. Both tubes are Electro Harmonix. Read about how to balnce this type of tube (Class "A" configuration dual triode) but I need safe testpoints. Looking for any info on the right way to accomplish this and any good mods to try. Thank you all!

 

[Didhefocus]

  Hi L&Gs. My first Bravo V3 started to make a pulsing noise in the left channel. Told the factory and their tech said to turrn the yellow trim pots until sound improved. It did not. Background hiss got steady and louder in the left channel. Bought a seconf unit from eBay. same problem within minutes. Also the LEDs started to pulse as well. Thought it may be overdriven by the ROKU. Used a 1/8" cable with a volume adjuster. Still no joy. But now I have a unit to play with. Both tubes are Electro Harmonix. Read about how to balnce this type of tube (Class "A" configuration dual triode) but I need safe testpoints. Looking for any info on the right way to accomplish this and any good mods to try. Thank you all!

Welcome,
It took me a while to figure out where to connect my meter for setting the bias even with many mods found on the web. I only found one that actually showed were to hook up the meter. My conclusion is in the pics I just posted. The schematic shows 14v above the tube, that is where I test on mine. I've found many recommendations but all were in the 12-16 vdc range. It will vary depending on mods. IRL510 MOSFET instead of the IRF630 is the mod that was the most effective. If you read through this thread, I believe lots of mods are mentioned or referred to. Bypassing the EQ also helped depending on which headphones I was using.
 
Mine is actually acting up now by shutting down after about 5 minutes of use. With a fan it plays indefinitely! I've had my V3 for a year or so and it only recently started happening. My guess is the LM317 regulators are the culprits. The heat sinks (silver ones) on them are tiny! I have some larger heat sinks on order so I'll report about that when they arrive.
Good Luck!
 
 
 
 

 

[Cirric]

Thank you !  I'll order some parts and get on it. Strange that you had the same symptoms after a period of time. I did a quick review on Amazon while the unit was working and gave  it a good rating. (The unit was DOA but that turned out to be just a bad figure 8 cable. Stuff happens.) Cirric

 

[Euf0ria]

Just want to share what I have done so far with my amp:
- Powercap to 3300uF 35V cap + 70uF flash capacitor in parallell.
- Input capacitors to 1uF WIMA polyester cap
- Output capacitors to 2200uF Nichicon Fine gold 
- Changes blue LED to white
 
At this stage the sound feels more powerful and I think there's a little more power in the lower regions in terms of punch and body. This could also be the fact that the tube has gotten a few hours playtime and have opened up a little, i don't know. I'm actually more excited about the changes I'm about to do very soon!
 
Why can't i post pictures here? Is it because its my first post? For now you will have to settle with a link to the picture =/.
https://dl.dropboxusercontent.com/u/39367418/Headphone_Stuff/bravo_v3-1_LED.jpg

 
More to come:
- Change to IRL510
- Change to LM317AT
- Mount big heatsink

 

[Didhefocus]

I got my Chinese heat sinks in just 7 days, $10.50 including shipping! Installed them this evening and no heat problems so far. The V3 has  been on for over an hour now without any forced cooling! Next step is to modify the top to accommodate them.
 

 

 

[Cirric]

Did you replace the MOS FETs as well? And where did you order the heat sinks from? Curious to see how well they wofk.

 

[Cirric]

I have to agree that these inexpensive amps are great for modding. As with my first computer, a Timex Sinclair 1000 which I modded the heck out of, there was no great investment to lose. Just fun and learning!

 

[Didhefocus]

The MOSFETs were upgraded early on with IRL510. IMO the best MOD out there. Eliminates the crosstalk distortion almost completely. I'll post a link to the heatsinks later.

 

[Didhefocus]

I found the heat-sinks at this listing on eBay. I ended up getting a custom order of 4)35 x 15 x 9mm for the LM317s, 2)40x25x15mm and 2)35x25x15mm for the IRL510s.
 
http://www.ebay.com/itm/231513408888?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

 

[Didhefocus]

Here's the link to the other ones:
 
http://www.ebay.com/itm/231512480622?_trksid=p2060353.m1438.l2648&ssPageName=STRK%3AMEBIDX%3AIT

 

[Didhefocus]

I may have jumped the gun here! 
I was happy with my fix and had no problems when using the original EH tube. I decided to put back the Fisher/Mullard tube that was in the amp when I first noticed the problem. After re-adjusting the bias to 14.3v on both sides(same as the EH) it played fine and shut down after about 10 minutes (estimated).
I'm trying another tube right now...waiting for it to warm up.

 

[Cirric]

I'll "cool my heels" while waiting for your results.

 

[Didhefocus]

Sorry if I kept anyone in suspense...but I think I figured out my problem. I turned on the Bravo and left it alone for a few minutes. When I came back it had already shut down. I felt all the heat sinks and noticed that they were all still quite warm except the left IRL510, which was already cold! The left one was consistently hotter than the right during testing with my new infra-red non-contact thermometer. So I'm thinking that the one that shut down got cooler before the others since they were still working! 
I should still have a good pair of IRL530s so I'll go ahead and install them and see what happens.

 

[Euf0ria]

Didhefocus:
I appreciate your updates since this could practically happen to anyone of us.
 

On my side I have collected the last parts for my final (for now) mod and will soon install the new heatsink that weighs 166 grams. That, comparing to the original heatsinks weighing just 22 grams together. That's a 750% improvement  in terms of mass=)

 

[Cirric]

Both the 510 and 530 MOSFETs are available on Amazon. I have not ordered any yet. 'llI continue to "cool my heels".