jc
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Post by jc on Jan 27, 2015 21:27:50 GMT
Hi all! I found this thread very helpful and makes a great summary of good mods. The PDF by floriangerard51 was also a great resource (although I do not intend on going as far as florian did with his mods). It doesn't look like this thread gets much attention anymore, but I had some burning questions (I'm fairly new to DIY). I wanted the remove/replace the LEDs (the blue and red lights are very unnatural looking and fatiguing to my eyes). I understand that shorting them can do the trick, but I wanted to add a warm white led under the tube and have the red LED removed completely. Is it a good idea to simply short that connection and then replace the blue one with the warm white? I'm also assuming that this does not affect any of the mods that involve those nodes. You can change the blue LED to anything you want but the red one must remain, its forward voltage rating (different for each colour) is important to the circuit. Maybe turn the red one under the board (being careful to keep polarity correct) to minimise its impact? Or see the suggestion above as regards electronic rating of an alternative. |
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Post by Deleted on Jan 27, 2015 21:50:28 GMT
A dab of black paint on it perhaps?
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Post by Deleted on Jan 27, 2015 21:55:04 GMT
I'm still waiting for a reply here, but I'll try a stab at the answer. From my reading of this entire thread, it looks like the blue can just be shorted by soldering a wire across the leads. The red is needed in the circuit because it helps set the Voltage past it for the CCS if I'm remembering correctly. So go back through the thread or the file and see what specs are needed, and then find one in the color you like that has the same specs. Many modern red and green LEDs have a forward voltage of around 1.8V at a couple of mA, whereas blue and white are normally closer to 3V. |
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Post by zeejet on Jan 27, 2015 22:01:21 GMT
Thanks for the tip CJ! Apparently, alternative colors with the same forward voltage range (red is 2.0-2.2V) include yellow, green and orange. Yellow is the closest to a warm white, but isn't nearly as pleasant. Warm white unfortunately has a forward voltage range of 3.0-3.4V, which is considerably higher relative to red. Unless there is a simple and compact way to step down the forward voltage, I will have to leave the red LED in place. I think I will replace the blue led with just a wire (removal) and leave the red LED since it's a relevant component in the circuit for now. As for using paint, I think that's a very nice lo-tech workaround that I may pursue. I was also gonna ask about replacing output caps with these 2200uF/25V Nichicons: www.amazon.com/dp/B004C50U2M/ref=wl_it_dp_o_pC_nS_ttl?_encoding=UTF8&colid=1ICLEA5N4KDON&coliid=I1H62W69TXWH9K, since they are the same diameter as the stock output caps and also 25mm in height (the amp top plate has a 30mm clearance). However, it turns out they are pricey and this amp has already cost me over 80 bucks when you count replacement parts so I think I'm gonna pass for now. |
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jc
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Post by jc on Jan 27, 2015 23:48:28 GMT
A dab of black paint on it perhaps? Another thought is to use coloured LED "caps". These are common in the car audio trade for changing the display colours of audio illumination or even dashboard lights (though that is more complicated in newer cars requiring the repainting of needle pointers etc). The point being LED caps are available, your only problem being starting with a red LED the effect of the caps will be a little unpredictable as they were meant primarily to work with white LEDS. I also found this handy guide...  |
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Post by Deleted on Jan 28, 2015 0:03:33 GMT
Hi Chris
I think that that may be old data, and the limits are far too wide. The best thing to do, is to check the specs of the LEDs you intend to buy using data sheets at the retailer if available. Jaycar, RS etc. provide this data on their web sites.
With Green LEDs for example, it's the waterclear high millicandella output types, that have a forward voltage drop more like a white or high output Blue LED. (around 3V) The smaller green diffused types are more likely to be approx. 2V at a couple of mA.
Kind Regards
Alex
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Post by jheu02 on Jan 28, 2015 18:26:19 GMT
If you just need the 1.8V, why not string 3 1N4148s in series. Should be right around 1.8. Then there's no artificial light source. Or, is there something else the LED is doing?
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Post by zeejet on Jan 30, 2015 4:10:08 GMT
So i just did the soft start mod and it didn't do anything except maybe reduce the OFF switching sound. The ON sound is just as loud. The LEDs are also just as bright as before (although I did try to mask the red LED).
EDIT: The LED is indeed dimmer, I just didn't realize it at first. I think the mod was done correctly and the ON pop sound might be unavoidable.
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jc
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Post by jc on Jan 31, 2015 23:01:56 GMT
Another thought for masking the red LED. Use some black heat-shrink, 6-8mm cut a little longer than the LED. When shrinking down immediately pinch the the extra length to seal it. Should give you very nearly a full black out.
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Post by zeejet on Feb 4, 2015 4:43:58 GMT
The warm white LED arrived and I attempted to install it. Partial success! The failure was to fully remove the blue LED; it has a hilt that prevents it from coming out from either the top or bottom of the board (it's stuck behind the tube socket). I was able to install the white LED from below, but the blue one is wedged beneath the tube socket. It has not shorted any connections so I think it should be fine! If you are ballsy, definitely try to remove the tube socket so that you can fully extract the blue LED and then re-solder the tube socket. My final thoughts on the LED swap: not as easy as predicted, but still worth it if you hate the bright blue color of the stock LED. Also, the warm white was not as warm as I anticipated. I should've gone with a yellow LED instead to try and match the glow of the tube.'  |
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Post by wasch on Feb 17, 2015 20:45:47 GMT
Hi sorry for my English, i hope someone can Help me.
My Bravo V2 has no Audio output on Full vol i can heare only a littlebit.
The Tube doesent get warm the only thing that get hot ist on position LM317
and the silver Cooler get so hot that i cant toutch it.
Has someone an idea what is damage?
Thanks alot.
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Post by solderman on Feb 23, 2015 12:39:42 GMT
pin 4 and 5 of the tube (filaments) are connected. This will ensure the annoying crosstalk is present in this amp too. when unmodded  just CUT this connection between pin 4 and 5 and this WILL cure the crosstalk just as oohms suggested in the picture above.  Should you want the BLUE LED out... just short it ! Converting the 6922 (ECC88) version to a 12AU7 version is possible. I might make a tutorial for it in the future. It involves cutting copper traces and adding some wires on the 6922 board too. Bye, bye crosstalk !  I have Ian's amp running straight up to 50kHz instead of 10kHz (-0.5 dB) just by popping in IRL530 (not IRF510, the 530 has half the Vgs voltage so more headroom) and also replacing the LM317 for the higher grade LM317A. The IRF510 will do the trick too but the IRL530 will increase headroom/output power also and clean up the highs roll-off in a similar way. ;D Crosstalk can be cured (and distortion WAY lowered) by NOT using the filaments in the output path (you will need to supply them with their own voltage) and connecting the LM317's directly to ground. The LM317's WILL need a MUCH bigger cooling fin and/or bias current of the output stage reduced in this case (do not take it below 70mA and you have to increase the output resistor from 47 to 68 Ohms). ;D These mods will be used in Ian's amp. Autobias works like a charm but is difficult to build even for more experienced D.I.Y.ers, so a simple but very effective mod it will be. Be careful de-soldering the Bravo board. The quality of the PCB is very crappy.  The copper traces fall off the PCB already when you just point at them. replace the 25 volt power cap for a 35 volts type (will be MUCH larger) the input decoupling caps are highly recommended when you have a DC coupled music source. I would use a bipolar type and not polarised electrolite caps as these need a DC bias to work/form properly which is not present in this amp. These caps will NOT be performing well unbiassed.  Also replace the input pot for a log type when you want better travel. Mike's advice to swap the output caps for a better 105o type is also very adviseable (it seems only the resistors are still in place) 25 Volts will do in this case as the nominal voltage will be around 10-12 Volts DC you can also replace the 47 Ohm output resistor for 68 Ohms. |
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Post by solderman on Feb 23, 2015 12:41:40 GMT
Frans 1 W resistors , or 2 x suitable parallel .5w or .6W (perhaps 2 x 18R .6W MF types) ? Alex |
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Post by mrqs on Mar 31, 2015 22:43:18 GMT
Gents I've got recently an amp, which seems to be a newer version of the Bravo 6922 amp (also the seller describe it as an improved design). It's built with chinese 6n11J tube. The rest is standard: 2x LM317 and 2x IRF630. My intention is to (at least) replace the stock IRF630 to IRL510. After switching the amp on, I can hear constand buzz (or self-oscillating like) noise plus tome "tap, tap" sound every 3-5 seconds. I've decided to try another tube and got Zaerix E88CC. No more self oscillation, but still (however, much more silent this time) "tap" sound. The biggest problem, however, is that the E88CC might be broken - one channel is silent and one LM317 seems to be hotter than the other one. Need to try different tube (as soon as I get something). Until that - any chance that this buzz can be eliminated still using the chinese tube? The headphones I'm using are Sennheiser HD598 Thanks in advance for help!    |
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Post by tubehead on Aug 3, 2015 19:39:46 GMT
Is anyones potentiometer a bit wobbly ?. Mine is kinda wobbly and i cant find a replacement anywhere with no specs
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Post by PinkFloyd on Aug 3, 2015 20:08:59 GMT
Is anyones potentiometer a bit wobbly ?. Mine is kinda wobbly and i cant find a replacement anywhere with no specs Hi, The stock pot is a linear type and, for best performance, you want to replace it with a 50K log type. Whereabouts on the planet are you? I keep these pots in stock (ALPS) and they aren't expensive so don't worry  If your budget is REALLY tight I can send you a free pot that has been poached out of a Musical Fidelity V2 amp........ When I mod a V1 / V2 I always fit a new ALPS pot so have hundreds of 50K log pots kicking about..... you pay the postage and I'll happily send you one of those. When you say your pot is "wobbly", in what way is it wobbly? Is the shaft bent? is the pot "physically" loose on the PCB?...... wobbly can mean a lot of different things. Let me know and don't worry, I'll sort you out with a much better replacement pot for the Bravo. Welcome to the forum, Mike. |
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Post by tubehead on Aug 5, 2015 7:32:20 GMT
Is anyones potentiometer a bit wobbly ?. Mine is kinda wobbly and i cant find a replacement anywhere with no specs Hi, The stock pot is a linear type and, for best performance, you want to replace it with a 50K log type. Whereabouts on the planet are you? I keep these pots in stock (ALPS) and they aren't expensive so don't worry If your budget is REALLY tight I can send you a free pot that has been poached out of a Musical Fidelity V2 amp........ When I mod a V1 / V2 I always fit a new ALPS pot so have hundreds of 50K log pots kicking about..... you pay the postage and I'll happily send you one of those. When you say your pot is "wobbly", in what way is it wobbly? Is the shaft bent? is the pot "physically" loose on the PCB?...... wobbly can mean a lot of different things. Let me know and don't worry, I'll sort you out with a much better replacement pot for the Bravo. Welcome to the forum, Mike. the pot itself is not moving but the shaft has play when i move it. Its still straight tough. Ill send you a pm when i get home from work thanks. I live in the netherlands by the way. And i dont have a budget. I already built a linear power supply and changed the caps to elna. My irl530s are in transit. A little pic of the setup  |
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Post by tubehead on Aug 15, 2015 12:21:36 GMT
i decided to mod my v1 instead of the v2 and sold it last week. well here are some pics of my v1. Output caps and potentiometer thanks to mike. got to test the power supply cap he sent me after all is broken in. to do list: Blacken out red led. Change mosfets to irl530's Cnc the acrylic to fit way bigger heatsinks. Swap tubes anyone got a better 6922 tube for this baby?  |
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Post by tubehead on Aug 18, 2015 19:53:12 GMT
I was just listening to my amp and i accidentaly moved the balance to the left and both channels still had sound but just weaker. Do other bravo audio v1s have this too or is mine screwed?
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Post by tubehead on Aug 18, 2015 20:06:03 GMT
I think i found the problem. If i measure the new potentiometer i get a connection when i measure on l channel v in and r channel v out and vice versa. I kinda broke the original pot when i took it off oh well
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Post by cpcustoms66 on Oct 12, 2015 17:26:43 GMT
Ive been reading some other forums on this little beauty, my amp comes in a couple of days. I an new to tube amps but not to electronics. I ordered the IRL510 mosfets to swap and im going to do the supply cap change to the 35v 2200uf as well as doing the crosstalk mod. But some of the other forums have stated that they also had success with 12AX& tubes. I know that the 12 series tubes would be interchangeable, but would rolling to a tube like the 12ax7 with such a higher gain cause problems? does anyone have any experience with what kind of sound difference this would make? Going to be runnig it with a pair of Senn HD598's
THANKS!!
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Post by cpcustoms66 on Oct 19, 2015 23:14:40 GMT
I have heard some mentions of linear regulated power supplies being used, does anyone have an idea of where to get such a power supply for this amp? I have found some on amazon but they say linear and switching regulated power supply. I cant seem to find a 24v 2+ amp power supply that is simply a linear regulated power supply.
Thanks !!!
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jc
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Post by jc on Oct 20, 2015 12:17:34 GMT
I think it's something that is far less common to find these days with the advent of the very cheap to produce switching psus taking over. At the expensive end there are bench power supplies that would fill the bill but also are rather large. You could also search some of the large Chinese suppliers and see if they supply single units. Another way is scour the auction sites or forums for something that will do the job e.g. €bay |
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Post by tubehead on Oct 22, 2015 19:22:47 GMT
I have heard some mentions of linear regulated power supplies being used, does anyone have an idea of where to get such a power supply for this amp? I have found some on amazon but they say linear and switching regulated power supply. I cant seem to find a 24v 2+ amp power supply that is simply a linear regulated power supply. Thanks !!! I found a nice 230v-24v transformer at work. took it home made a rectifier with 4 diodes folowed by a capacitor and then a 24v voltage regulator. Works like a charm and it really makes a difference in the sound. output looks flat on the scope too ! |
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Post by Deleted on Oct 22, 2015 21:16:40 GMT
I have heard some mentions of linear regulated power supplies being used, does anyone have an idea of where to get such a power supply for this amp? I have found some on amazon but they say linear and switching regulated power supply. I cant seem to find a 24v 2+ amp power supply that is simply a linear regulated power supply. Thanks !!! I found a nice 230v-24v transformer at work. took it home made a rectifier with 4 diodes folowed by a capacitor and then a 24v voltage regulator. Works like a charm and it really makes a difference in the sound. output looks flat on the scope too ! I am not surprised that it performs better now. It may even increase it's longevity by a considerable amount, as many units didn't last much longer than 12 months . Do you have any photos to show other Bravo users how you did it ?
Alex
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If your budget is REALLY tight I can send you a free pot that has been poached out of a Musical Fidelity V2 amp........ When I mod a V1 / V2 I always fit a new ALPS pot so have hundreds of 50K log pots kicking about..... you pay the postage and I'll happily send you one of those.
