[abcray]

Hi, jushtanguns
 
Yes, the V1 has the trimmer pots for setting bias, but I'll replace those for better quality ones.
The bias caps are those soldered across the bias trim pot. 
I'm also curious about the power caps, why 2x Nichcon FW 4700uF 35V instead of only one?
Thanks for your attention.
 

 

[abcray]

Thanks for the tip.
By the way, what are those bias cap specs soldered underneath the board?
 

 

[Avro_Arrow]

They are just some I had laying around.
The specs are 680uF @ 10 volts Panasonic FC I think...
I did have a link to some I recommended if you read
through the old threads.
 
I also have ELNA 1000uF @ 25 volt Silmic II
for the output caps and a 10,000uF @ 25 volt
Nichicon VR for the power supply.

 

[-su]

hi guys,
 
sorry if the question has asked before,
93+ pages surely take lots of time to read
 
Just a simple one,
I just got an RCA Black Plate 12AU7, it is still under shipping process though,
planned to use it on my Bravo V2 ( version without trimmer, bias is not yet tuned, difficult to find a good trimpot here ).
 
Based on anyone who have ever tried the RCAs on Bravo V2 here,
do I have to change the bias voltage to accomodate the tube?
Or is it just "plug-and-play-and-sound",
with the bias tuning required only to get a better sound? 
 
Thanks
 
 

 

[jjmai]

 
Quote:

hi guys,
 
sorry if the question has asked before,
93+ pages surely take lots of time to read
 
Just a simple one,
I just got an RCA Black Plate 12AU7, it is still under shipping process though,
planned to use it on my Bravo V2 ( version without trimmer, bias is not yet tuned, difficult to find a good trimpot here ).
 
Based on anyone who have ever tried the RCAs on Bravo V2 here,
do I have to change the bias voltage to accomodate the tube?
Or is it just "plug-and-play-and-sound",
with the bias tuning required only to get a better sound? 
 
Thanks
 
 

My guess is that each Bravo V2 and each tube will behave a little differently.  You use the trim pot to adjust the left and right channels' volumes separately, in order to compensate for the component variation/qualities on the Bravo board and tubes.  Some combination may just hit it right without needing any bias.  Correct me if I am wrong...

 

[Ultrainferno]

The standard V2 will "auto adjust" the bias for the tube, so it's plug and play for the std version
Correct me if I'm wrong anyone

 

[-su]

Quote:

 
Quote:

hi guys,
 
sorry if the question has asked before,
93+ pages surely take lots of time to read
 
Just a simple one,
I just got an RCA Black Plate 12AU7, it is still under shipping process though,
planned to use it on my Bravo V2 ( version without trimmer, bias is not yet tuned, difficult to find a good trimpot here ).
 
Based on anyone who have ever tried the RCAs on Bravo V2 here,
do I have to change the bias voltage to accomodate the tube?
Or is it just "plug-and-play-and-sound",
with the bias tuning required only to get a better sound? 
 
Thanks
 
 

My guess is that each Bravo V2 and each tube will behave a little differently.  You use the trim pot to adjust the left and right channels' volumes separately, in order to compensate for the component variation/qualities on the Bravo board and tubes.  Some combination may just hit it right without needing any bias.  Correct me if I am wrong...

Hi jjmai,
 
thanks for your reply.
 
Yes i am totally agree about the behavioral differences,
but what I was actually pointing out in my previous question is,
can Bravo V2 compensates the RCA black plate 12AU7 without any trimming?

or in other words, can the Bravo V2 and RCA black plate 12AU7 combination hits it all right? 
 
===
Anyway, FWIR, the trimpot adjustment is not really related directly to each channel's volume level,
it is more about adjusting voltage being supplied to the tube (or other parts of circuitry, not really sure about the part

).


Quote:

The standard V2 will "auto adjust" the bias for the tube, so it's plug and play for the std version
Correct me if I'm wrong anyone

thanks inferno, I hope I really don't have to readjust the bias...

 

[Ultrainferno]

Btw, I only use rca tubes in the V2, and I've never ever adjusted anything

 

[Avro_Arrow]

As I have mentioned before, the version of these amps with trim pots uses Cathode Bias and
the version with no trimmers uses Grid Leak Bias. The Cathode Bias models should
be adjusted for between 0.65 and 0.7 of the supply voltage at the anode of the tube.
In the case of 24 volts supply, this wound be 16 to 17 volts as measured at the anode of the tube.
The Grid Leak Bias version may appear to not need adjustment, but the grid leak resistor value
should be calculated from the charts for the tube used. It would be interesting if someone with
the Grid leak bias version would measure their anode voltage and see how close it is to
the 0.65 to 0.7 range...

 

[-su]

Plugged in the '50s black plate,
let it warms up for 10mins,
wow it is totally a noticeable improvement, especially on music separation and details, as if someone has opened up a thin layer that was there before...
IMHO the hi freq is also extended as I always felt there's some roll-off there before.
 
For 30 bucks, I think this is really a worth upgrade.
(well, yeah a stock china tube won't do any good anyway).

 

[Bacci]

How does bass & bass extension compare to your original chinese tube (6n11?) ?
I'm looking to roll tube as well and the 12at7 rca black plate is a prime candidate

 

[-su]

Quote:

How does bass & bass extension compare to your original chinese tube (6n11?) ?
I'm looking to roll tube as well and the 12at7 rca black plate is a prime candidate

I don't think there's a significant improvement over the low section, maybe just a bit tighten up.
But well, FYI I'm using DT880/250 which known to be not having much bass itself
and I don't have a gold analytical ear anyway

so YMMV
 
But, I do think this tube makes the overall reproduced sound become much better refined.

 

[justhandguns]

Quote:

Hi, jushtanguns
 
Yes, the V1 has the trimmer pots for setting bias, but I'll replace those for better quality ones.
The bias caps are those soldered across the bias trim pot. 
I'm also curious about the power caps, why 2x Nichcon FW 4700uF 35V instead of only one?
Thanks for your attention.
 

 
Hi, here is the list of resistors
 

2 x	(REY50-170) - 47R 0.5W TAKMAN Metal Film Resistor
2 x	(REY50-495) - 24K 0.5W TAKMAN Metal Film Resistor
2 x	(REY50-385) - 3K 0.5W TAKMAN Metal Film Resistor
1 x	(REY50-350) - 1K5 0.5W TAKMAN Metal Film Resistor
2 x	(REY50-330) - 1K 0.5W TAKMAN Metal Film Resistor
2 x	(REY50-190) - 68R 0.5W TAKMAN Metal Film Resistor
2 x	(REY50-080) - 8R2 0.5W TAKMAN Metal Film Resistor

2 x	(REY50-250) - 220R 0.5W TAKMAN Metal Film Resistor
2 x	(REY50-385) - 3K 0.5W TAKMAN Metal Film Resistor

 
There may be a bit of extra ones which I used to played around with.

And why I have  2x Nichcon FW 4700uF 35V? It just I want them to fit through the hole on the top plate.
One through the hole and the other sits underneath.
 
As for the bias in the V2, I think it is better if you have the trimmer to adjust the bias if you want to roll some tubes.
I don't want to spend time explaining it, just search the forum and the net to find the answers.

 

[Bacci]

Quote:

Quote:

How does bass & bass extension compare to your original chinese tube (6n11?) ?
I'm looking to roll tube as well and the 12at7 rca black plate is a prime candidate

I don't think there's a significant improvement over the low section, maybe just a bit tighten up.
But well, FYI I'm using DT880/250 which known to be not having much bass itself
and I don't have a gold analytical ear anyway

so YMMV
 
But, I do think this tube makes the overall reproduced sound become much better refined.

Okay thanks! I decided to pick up a 12at7 as well, went for RCA 6201 with wide black plates.
As you said these are still affordable at 30 around bucks. 

 

[momostallion]

just won a bravo v2.  now i get to play the waiting game.  at least i have 60 more pages to read on this thread to help decide what else to order!