Bravo / Indeed Headphone amplifiers

[Deleted]

Jun 16, 2010 17:00:24 GMT @solderdude said:

I will when I have some time for it.
This can ONLY be done if you move the LM317's to a large cooling surface.
I do this by mounting an aluminum plate underneath the amp.
This mod can't be done with the LM317's on the small cooling fins.

Thank you for your reply, Frans!

I would like to mount the LT317A's on an aluminum plate, and I will try to do that. Is the plate that you show on your PDF something you made, or were you able to purchase it already cut from somewhere? If it isn't available for purchase, I will probably have to go to my shop and hand cut one, file it and drill it, but I thought I would ask, just in case there is a way to save a little time and labor.

Thanks again, and All the Best!

[Deleted]

The bottom plate is made by HeliHarris (he made it himself fro his Miri I modded).
The bottom plate for Rabbit's Bravo I made myself from a square piece of aluminium.
I filed the corners of that one round with a file.

No way to save time and labor I'm afraid.

[Deleted]

Jun 16, 2010 19:31:11 GMT @solderdude said:

The bottom plate is made by HeliHarris (he made it himself fro his Miri I modded).
The bottom plate for Rabbit's Bravo I made myself from a square piece of aluminium.
I filed the corners of that one round with a file.

No way to save time and labor I'm afraid.

Oh, well! I guess I am going to have to do it the hard way , but I think it is well worth it!

Thanks for your prompt response!

[Deleted]

The pdf file is expanded with a tutorial to do the mods.

www.mediafire.com/file/vzdwnrlnjjz/modding of a Miridiy amplifier.pdf

here is one of the Indeed G2 too:

www.mediafire.com/file/ccw7g2f8u97elpd/modifying%20the%20Indeed%20G2%20amplifier%28f%29.pdf

[Deleted]

Jun 17, 2010 20:27:41 GMT @solderdude said:

The pdf file is expanded with a tutorial to do the mods.

www.mediafire.com/file/vzdwnrlnjjz/modding of a Miridiy amplifier.pdf

Thank you so much, Frans! It looks very clear, and it encourages me to go ahead with the mods. In my junk pile I just found an old anodized aluminum external hard drive case, which had died a few years ago. I plan to cannibalize it, and make at least 4 bottom plates for the 5 hybrid amps that I have. I will also order the Traco TSR1-2465, as well as a few other parts that I will need, including some hardware to enable me to raise the PCB higher.

Many, many thanks!

[Deleted]

Tip:

Put the alu bottom plate (that acts as a cooling fin) onto high feet so air can pass it easily.

[hellmind]

My Bravo arrived yesterday. It took 5 days from HK to Brazil and another 11 days for customs office check out.
It´s the 12AU7 version with IRF630. One thing i noticed it´s camed without the bias trimpot (resistor instead) and 2 extra eletrolict capacitors near this resistors.
Today i will buy the trimpots and mosfets.
If anyone is curious about this version i will take some pics to show.

[Deleted]

Jul 21, 2010 11:50:01 GMT hellmind said:

If anyone is curious about this version i will take some pics to show.

Hi,
I would like to see some pics, especially ones that show the new (different) components but, more importantly, I'm sure that many other guys who know more about what they are looking at than I do would also be interested. One such, solderdude (Frans) is on holiday at the moment and may not be following the thread.
Cheers,
Dave.

[Deleted]

the 12AU7 version is another version and is different from the others.
It does not have pots for bias adjustment.
The caps need to be nonpolar or bipolar caps instead of the supplied polar electrolytics.

This amp does not have cathode resistors (all the other versions have them in the form of 2 pots) so does not need the cathode caps as the cathode is already hardwired to ground.

For this version please visit the 12AU7 thread in the DIY section:

rockgrotto.proboards.com/index.cgi?board=m&action=display&thread=5297&page=1

[hellmind]

davek, my bravo is just the same as the link above.

solderdude, the electrolytic caps already came with the amp. Can i bypass them? Other thing i notice is that the little cap near the right mosfet is missing, even the holes are not there.

The IRL series are not avaible in Brazil, i'll need to import it . IRF630 sounds awful.

[Deleted]

If your music source does not have a DC on it's output you can safely bypass these 1uF caps (take them out and short the pads).
The 2 big 1000uF/25V caps cannot be bypassed.
They isolate the DC component on the MOSFET Source from the HP output and are essential.

Don't worry about the small 100nF cap not being there.
There is already one in there which is more then sufficient for this design.
There are no switching or fast components in there that need this extra decoupling locally.

IMO the MOSFET's need to be changed, the bias pots added (see 12AU7 thread) and oohms crosstalk mod must be done.
You can exchange the 2 output caps for decent 105oC types.
They are quite close to very hot components so for this reason alone it is recommended
I highly recommend you replace the big power cap for a 35 Volt type (will probably become 3300 or 2200uF for it to fit mechanically).

Oh... almost forgot... replace the crappy power switch for something better.
It is bound to give mechanical or electrical problems in the future anyway.

[MaN227]

anyone wants to buy one (G2) , shoot me a msg, I have two and well one is simply not needed. wont hurt to get a bit of recoup on being ripped off with the RG group sale ... pffff

for that matter I have a G1 I will sell too and some portable amps collecting dust

I'd like to pay a certain Pink fellow back for his most generous kindness

anywho

Peace

[cure]

hello

i just purchased the bravo v2 tube amplifier (which has yet to arrive.)
being a total noob in the tube world, i wanted to ask you guys one quick question:

it says that the compatible tubes for the bravo v2 are 6N10/ECC82, does this mean these are
the only viable tube replacements for the bravo? will it take any 12AU7? say siemens, GE, mullard, telefunken? i mean, tubes will fit into the bravo v2 as long as it's 12AU7?
i've seen alot of 12AU7 being sold on the net, too many variants. i don't have an idea which one would fit the bravo v2.
there's the 12AU7/6189, 12AU7/ECC82, 5814A, E80CC / 6085 (12AU7 compatible), etc....

and what do you mean by 'matched pairs'?

i was thinking of buying tubes so when the bravo arrives, i'll be able to do some tube rolling and test which one suits me best.

again, sorry for these ignoramus questions.

kind regards,

cure

[Deleted]

The Bravo V2 isn't the best amp for tube rolling as it has no pots to adjust the bias which is handy if you like to try more tubes.
The G2 is better equipped for that as are the other versions as these have anode voltage adjustment pots.

It should take all 12AU7 (=ECC82) of various makes and age.
Because there are differences between the tubes it is likely not all will work O.K.
E80CC also has somewhat similar v/i characteristics and might not get in the proper anode voltage range.

I say listen to it for a while with an 12AU7 or ECC82 tube and see if you like it.
If you feel up to it do some modding (MOSFET and Oohms mods on page 1) or start rolling some tubes.

If you replace the 3k CCS resistors for 5k pots you can adjust the bias and can roll more types of tubes as long as they are pin-compatible, have somewhat similar specs as 12AU7 and are 12V tubes with centre tap on pin 9.

Matched pairs is used describing 2 tubes that have been selected out of a number of tubes to have the most similar characteristics.
a must in differential amps and serious amps where you want the L and R channel to act the same.
Sometimes they also say a single tube is 'matched' when both triodes in one tube are very close in specs/performance.
This is not always the case, sometimes 2 halves can have quite some differneces in performance.

You do not need a matched pair (2 tubes) as this amp only takes one.

[Deleted]

Jul 22, 2010 1:32:13 GMT MaN227 said:

I will sell too and some portable amps collecting dust

Peace

Hi,
Just out of interest what portable amps do you have spare and what prices are you hoping for for them. Need to be shipped to limey-land.
Cheers,
Dave.

[gearhound]

I just purchased a Bravo EH6922 hybrid headphone amp, and after a few initial problems (voltage bias in one channel, was double the voltage of the other), seems to be working fine now.
I have never been much of a fan of EH tubes, so I rolled a $6 NOS Sylvania 6DJ8 tube in it's place.
Seems to have a slightly smoother presentation with tighter bass response also, IMO.
I'm not sure I understand the logic of spending serious $$$ on European-made 6922 tubes?
This is a cheaply-made (and cheaply sold) amp under anyone's standards.
I can understand modders spending a few extra bucks on better caps, active devices, etc.
Hey, modding is FUN, and a cheap way of sonically improving marginal equipment.
But I think I would be looking at a better headphone amp than the Bravo, Indeed, etc., BEFORE I'd start tube rolling into the hundreds of dollars?

Just my 2 cents, mind you?
Steve

[Deleted]

The Bravo/Indeed's are more novelty amps then anything else.
Lot's of people like the looks and it doesn't sound bad either.
The newer Miridiy and Bravos/Indeeds seem to ship with IRF610 or IRF510 and do not have a 'limited bandwith' anymore.

The quality of the tubes, some parts and quality control of the amps still seem to be below par as is the adjustment of the bias voltage.
I too would only recommend these amps if you like the looks, tubes and like to do some mods and adjustments or just want to hear what 'tubesound' is all about.

If you are looking for 'cheap' and good performing amps I would recommend single or dual chip standard application amplifiers such as the Neco or similar solid state amps (sometimes reffered to as 'Cmoy' though Chu Moy has nothing to do with these amps).

These don't have the mystical glowing bottles ofcoarse which is the funfactor of the Bravo's and alikes.

[gearhound]

My OPA2227 Cmoy amp, has been my go-to portable rig (Senn. PX-100) for years now.

While the little BRAVO amp isn't portable, it is small enough to sit on a little night stand, right next to my bed.
With the channel bias voltage set at 15 Vdc, it has some pretty good dynamics to it, with an el-cheapo NOS Sylvania 6DJ8 tube, driving an old set of 600 ohm Beyerdynamics DT-990 Pro's.
It probably would sound better with an Amperex or Telefunken 6922 tube, but food/gasoline are bigger priorities in my life right now.
I'm sure the BRAVO does NOT do justice to the nice Beyerdynamics, but still, it isn't bad at all?
I have a brand new set of 32 ohm Goldring DR-100 headphones, that I tried out with a solid state amp (nice sound), but haven't gotten around yet to plugging it into the BRAVO.
I picked up a cheap used Mean Well 24Vdc/6.5A power supply, that I'm gonna try out with the BRAVO amp, as soon as I can get a 2.1mm input plug.
I've heard/read that a higher current PSU, brings out the dynamics and bass response better than the stock 24Vdc/1A PSU?
Seriously, I cannot complain much about the price/performance ratio of the BRAVO amp, even if company QC isn't quite up to snuff.

Steve

[beerme]

Hey all,

I have the first version of the Bravo Audio amp, an i just want some advice. The RED led no longer lights.....hold up, let me start ..at the start..

I bought the little amp at a bargin price on the Bay about 18 months ago....I had decided to get into tubes......

Long story short, the little amp has been on for most of the 18 months but not in use, I have had a TESLA PCC88 tube in it for 90% of the time, and now, cos of the grotto I have actually started using it and noticed that the red led is no longer lighting where before it was..??

Any ideas?

[Deleted]

If you have voltmeter/multimeter check if the voltage across the RED LED is still around 1.8V (it should be around that voltage)

If you don't have a meter then the question is if the blue LED still lights up O.K. and the sound is still good I wouldn't worry too much about it.
the parts in these amps are not of great quality.
If you want it back on again just replace the LED with another RED LED preferably a 20mA version instead of a 2mA version.
Mind the anode and cathode !!

[beerme]

Thanks, SD. The voltage across the led is 1.6....[something].

The blue led does not work but this was deliberate, I shorted it as I, or should I say, the missus, thought it was too bright....so I 'popped' it!!

Dave.

[Deleted]

1.6V should be enough and is also temperature dependent (a little).
You can also replace the red LED with 3 diodes in series (1N914 or 1N4148) if you want to kill the red LED too (in your case it doesn't light up anyway).
You would have to re-adjust the Anode voltage again as it is only close to the desired voltage.
I replaced the blue LED with a less bright orange one and lowered the current in this circuit to match the intensity level to my taste.
the blue LED is a bit flashy for my taste too and would rather kill (short) it then leave it on.
But that's personal... a lot of people really like the blue LED.

[rreis]

finally... hmm, forum stoped in time in August 2010?

this was a very instructive thread

cheers!

[Deleted]

I guess it's a logical progression, though I'm certainly not tempted!



If your dead keen look here

[djmattm]

Sept 11, 2010 14:59:54 GMT @cjarchez said:

I guess it's a logical progression, though I'm certainly not tempted!



If your dead keen look here

Hi, i've just won it on the bay for just 32 euro shipped, i think it's just 99% the same of the bravo/indeed/miridiy, as soon as it arrives i will post back