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Bravo v3 tranformer upgrade

post #1 of 5
Thread Starter 

Hi everyone this may end up being a double post as i don't see the original one i posted.  but hello all

First off I love tubes and the sound they make.  I got this little amp for 25 dollars and could not say no.  But I do believe the AC converter is pretty much junk, and I was hoping someone has messed with that and has a few suggestions for a better AC converter for this thing.  Sound reproduction with a good converter will go a long way.

     Also I do plan on the mod that removes the equalizer completely from the circuit.  I get annoying crackles from anyone of the sliders.  I move each one a little up and down or side to side till I find what ever one is causing the noise.  It goes away but will start again after about 15 minutes, until I move them again.  I sprayed air first in the sliders then DeOxit + ProGold and that worked for about a day.  So I decided to do the mod this week.

    Next question does anyone know where there is a schematic I can download of the V3.  I am getting older now and tracing the copper tracings on the back of the board is getting difficult, well honestly I just don't want to do it anymore.  I just want to change out the caps in the signal path.  I am also going to change the power MOSFETs  to IRL510s ordered those yesterday.

     Now onto tubes.  I tried a series of tubes that i had lying around the work bench.  Now this is highly subjective and sounded good or bad to my ears.  You may feel or hear different, but I found the tubes that sounded the best and worst were.

1. Amperex 6922 Bugle Boy tubes.  Open and airy gave a good 3d effect

2. Jan Phillips 6922.  The one I put in was from 1983 so one of the more affordable nos tubes.  Still open and airy but just not quite as detailed as the Amperex.

      For those on a budget we now get into new production tubes.

3. New production 6922 Gold Lions, in my opinion have the closest sound to NOS out there today.  I liked them very much in this little amp and would choose these over NOS just because of cost difference, and the fact they sound damned good.  Don't get me wrong, the Amperex and the Phillips still sound better but cost a lot more.

4. EH gold pin 6922 don't sound to bad, they could be a little shrill to my ear, and seem to struggle a little with the bass.  Still a tube I could listen to, but not my first choice.

5. New production JJ 6922.  Well how can I say it.  They sure had the most gain out of all of the tubes I tried, but in my book loud does not equal quality.  This tube was honky.  I did not care for this tube in my cd player either.

6. The Sovtek 6922 was by far the wost of the bunch all mids, the bass was flubby in fact it really sounded like my driver was distorting, and the highs rolled off way early.  I thought hell maybe it was just the tube so i grabbed another one, same deal.

Biasing this amp was easy but the Amperex had the dials maxed out before it got to 16.25 volts.  The rest seemed to get to 16.5 volts around the middle.

I have some Chinese tubes but did not bother with those as I have yet to hear one that sounds good to my ear.

Any way I hope some has some ideas about power supplies and hope i can get a schematic.

Hope my tube rolling trials helps someone.

Thanks in advance for any help.

post #2 of 5
Theres a schematic out there if you google it. I remember someone jumping resistors to bypass the passive eq. That feature could easily be modded with a switchable bypass. I am not sure if anyone has replaced the ac transformer. I upgraded my earmax transformer from 19w to 55w and it made a noticeable difference.
post #3 of 5

EQ bypass...



Schem: You were mentioning transformer upgrades from the OEM 24V, theres a bunch of 25V caps in there so those would have to be up'd accordingly.  You would also be contending with heat build up.  In an amp this small I think theres some risk involved in doing that.

Edited by kramer5150 - 3/27/14 at 8:31am
post #4 of 5
Thread Starter 

Thanks for the reply and the schematic now that i have that I can easily upgrade everything i need to.  as far as heat goes I have a plan to mount the board and leave the top off so air should be free flowing around it.

post #5 of 5
Thread Starter 

I just did the mod to remove the equalizer.  If you have this amp I recommend it greatly.  I am really enjoying the sound now, it seems the equalizer muted the whole audio spectrum.  As far as a new AC converter, I think I am just going to get a monster noise canceling  power outlet.  I need one anyway.  Can't wait til the MOSFETs get here hope to hear even more of a difference.  After changing the MOSFETs  I may or may not change the caps I think I may be getting to the point of diminishing returns on this amp.  I don't know let me know if anyone has changed the caps in the signal path and noticed a pronounced change in the audio reproduction of this amp.

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