Bravo Audio - funny looking little tube amps - Page 109

@trazom

BTW, what is the original tube ?

With which part did you replace it ?

The problem is that everything seems normal. With the original tube or other pops are still present.
No transistor seems burnt. I'll take some pictures tomorrow.

Thank you for your help.

Is the nice looking tube amp worth to buy?

Quote:

Originally Posted by trazom 

The problem is that everything seems normal. With the original tube or other pops are still present.
No transistor seems burnt. I'll take some pictures tomorrow.

Thank you for your help.

I'm not good in electronics, I know the blue LED is only for esthetics, but the red one is pretty important for creating some reference voltage. Too me a LED is dead  or there's some bad soldering on them.

Hello, I'm using Bravo V2 (unmodded) with my Shure 240 (38 ohm) and am getting lot of parasite noises. I've basically given up trying to fix the amp to stop producing the sounds (it picks EMI from the air, I also suspect power supply to give humm). So I'm thinking of replacing my headphones with ones with higher impedance to 'filter out' the noises.

Currently my volume knob is turned just little above nothing, because the headphones are so sensitive. When I turn the volume knob up (with no music playing) the noises remain the same.

So will replacing my 38ohm headphones with some 60-100ohm help to hide the noises? (I will need to turn the volume knob up to achieve the same sound volume), or am I thinking just wrong and have failed from basics of electronics? :-)

The humming interference and/or static noices may also come from bad soldering contacts.

This happens quite often when you have some oxidation at the pins of your tube/valve. You may

want to have a check at that as well.
 

Quote:

Originally Posted by ostap 

Hello, I'm using Bravo V2 (unmodded) with my Shure 240 (38 ohm) and am getting lot of parasite noises. I've basically given up trying to fix the amp to stop producing the sounds (it picks EMI from the air, I also suspect power supply to give humm). So I'm thinking of replacing my headphones with ones with higher impedance to 'filter out' the noises.

Currently my volume knob is turned just little above nothing, because the headphones are so sensitive. When I turn the volume knob up (with no music playing) the noises remain the same.

 

So will replacing my 38ohm headphones with some 60-100ohm help to hide the noises? (I will need to turn the volume knob up to achieve the same sound volume), or am I thinking just wrong and have failed from basics of electronics? :-)

Quote:

Originally Posted by trazom 

The problem is that everything seems normal. With the original tube or other pops are still present.
No transistor seems burnt. I'll take some pictures tomorrow.

Thank you for your help.

Hi again Trazom,

I have some news ...

I built a brand new headphone amp, like Bravo/Indeed/Muse (on a pcb, I chose every component) and I had a problem ...

Apparently, the MOS-FETs are VERY sensitive to electrostatics, because of the FE (field effect transistors), so you should NEVER touch it by the pins, only by the body.

I lost 1 then 2 IRL MOS-FETs, so I changed them with 2 IRF 510, kept really care.

Now, with a Sylvania tube, it's a pure sunshine !

So, even if the d'ont seem "burnt" maybe your FETs are dead

- check the IRL/IRF (forget the bad IRF 630 or 730/740 ... use only IRL 510/530 or IRF 510/512, but other could perfectly match ...)

- and, depending on your small TO-92 transistor *

* (I use 2SK117, audio N-FETs ; but if you use something like 2N3906, it' less critical)

By the wan, I tested :

- 6N11 china tube (1$ piece) very microphonics (like ugly ampli-op), maybe the worse tubes but still OK for the price (a test tube ?)

- 6DJ8/ECC88 RCA/Matsu****a (4~10$) : they are much better, very deep basses, clear sound, never tiring

- 6DJ8/ECC88 GE/Sylvania (paid 1$ on eBay, but 6~15$) : less lower basses, but very large presence, very clear

I'd like to find a 6922 EH, some say the russian 6N23P-EV are better, less microphoonics (for lower price).

Comments on tube tests are welcome :)

I bought one of these about a year ago from ebay.

The power supply is useless, giving a constant mains hum through the audio.  I substituted it for a decent one I had in my shed.

The sound quality seams pretty good, although the base is noticably clipped.

On balance, I think would not recommend this amp.  I think spending a bit more would be prudent.

Is there an official Bravo Store link? I want to make sure to get the right one if ever I do get one.

Quote:

Originally Posted by donunus 

Is there an official Bravo Store link? I want to make sure to get the right one if ever I do get one.

This is the official Bravo seller: http://stores.ebay.com/bravoaudio

But you might wanna go for an Indeed G2 ;)

Is it already documented what the main differences in sound are? what about reliability? I could only read about 20 pages and didn't find clear answers :) 

Is there anything else very near it that is turned on?

Quote:

Originally Posted by ostap 

Hello, I'm using Bravo V2 (unmodded) with my Shure 240 (38 ohm) and am getting lot of parasite noises. I've basically given up trying to fix the amp to stop producing the sounds (it picks EMI from the air, I also suspect power supply to give humm). So I'm thinking of replacing my headphones with ones with higher impedance to 'filter out' the noises.

Currently my volume knob is turned just little above nothing, because the headphones are so sensitive. When I turn the volume knob up (with no music playing) the noises remain the same.

 

So will replacing my 38ohm headphones with some 60-100ohm help to hide the noises? (I will need to turn the volume knob up to achieve the same sound volume), or am I thinking just wrong and have failed from basics of electronics? :-)

yes, it was there even with no other devices turned on or plugged in. However, meanwhile I have moved to another town and the high EMI sounds are gone. So I suspect there was some GSM transmitter on the roof of the building or something. I had big troubles with that, not even putting the amp into metal box (for shielding) did not help. But now it's gone, all that remains is the power supply's humm.

I have a biasing question.  I tried adjusting the bias to get to 16v but is impossible to do. When I adjust one side's bias voltage, the other side's voltage goes the opposite way. They seem to be not independent of each other. The best I could do to get them about the same voltage was at 12v. Will that be fine? Is it a tube problem?

16V is to high, target 13.5V