Bravo V2 :Summary mods necessary ;-)

[Deleted]

Are the fans brushless ?
Are the heatsinks grounded ?
With both fans running or only 1 ?
What happens if the fans are fed by an external power supply ?

[floriangerard51]

Well for the fan I don't know because they don't say ansything on the description datasheet...

There is one heatsink to the ground, I have to check which one...;-)



The noise is when two fans are running


I don't have checked with an external supply

I'll do the checks tomorrow!

Thanks!

[floriangerard51]

ok test done with replacing the L7805CV by one resistor (200ohms 5W) and it works perfect without any noise on the right channel ! That's much better! i'll let the resistor mounted and quit the L7805...;-) much better without any noise at low music levels.

[Deleted]

Seems like an oscillation in the 7805.
If it works O.K. with resistors it's best to keep it that way.

[floriangerard51]

yes you're right!
by the way i received the LT1083 this saturday morning so i'll do the final things for the linear power supply....a 24V PSU with a 100VA transfo...i'll don't get bother by the small amp 1 or 2 amps...;-) But that's a good thing to have a larger PSU for my futur projects also.

[floriangerard51]

Hi,

Here is my tuto, Solderdude do you know how to attach this file to the forum thread

here is the link please clic on the TELECHARGER CE FICHIER

[Deleted]

There is no link in your post.

How I do this:
I simply opened a (free) account on 'mediafire' (but there are more free pdf hosters, also google has one I believe).
You upload your file and they host it.
Then you simply copy the download link they supply for that file and you post that.
You can even see how many file downloads there have been.

If you post in an English based forum it might be best to stick with an English (or USA) hoster so people know what to 'click' when they are directed to this site.

Free hosters generally are not free of advertising.

[floriangerard51]

ok good i'll open an account tomorrow and put the file....as i'm working i can't go to much over internet at the moment ;-)

here is the link:

dl.free.fr/mf00QMLw4

You're right it is best to get an english based website....

[floriangerard51]

hi,

here is a question about the classA and the idle current....When you speak of idle current flowing the LMs is this will be the current also getting into the MOSFET if i use the datasheet of the IRL510 i could find the curve with the IDS and VDS....
But with it is better from 0.1 to 0.6A we are far from the zero when we'll have the negative phase of the sound signal ?
Can you explain with some graphs?

Also is it something interesting to get higher current than 0.6A for this design??? As now with the fan and big heatsink i'm no more than 21°C on the aluminium surface....

If i do understand the schematics, the MOSFET gives the sound voltage and the loop from the LM317 to the headphone resistor is the current source? Is taht true? How much voltage do we have at the point between IN of LM, + of 2200cap and out of the MOSFET?

thanks

[Deleted]

here is a question about the classA and the idle current....When you speak of idle current flowing the LMs is this will be the current also getting into the MOSFET

Yes, they are in series for D.C. current.
Yet, they are (up to a certain point) in parallel for A.C. signals

if i use the datasheet of the IRL510 i could find the curve with the IDS and VDS....
But with it is better from 0.1 to 0.6A

higher idle current means a lower output resistance (main difference) but ONLY in the case of this amp simply because it has NO overall feedback.
In 'normal' amps (overall feedback) the output resistance is determined by the overall gain, amount of feedback, intrinsic output resistance (open loop) is less of importance.

we are far from the zero when we'll have the negative phase of the sound signal ?
Can you explain with some graphs?

The negative halve of the sinewave (the peak value) is limited by the LM317 (current source) so the negative half of a sinewave is current limited.
The positive half of the sinewave is NOT limited and can even be several times higher than the negative half of the sinewave (when the power supply allows and load impedance is below a certain value).
This asymmetrical clipping must be avoided as it has a similar effect as a DC offset in a DC coupled amplifier.

The idle current thus should be calculated by including:
a: load resistance (HP impedance + output resistance)
b: maximum output voltage (peak value, not RMS value)

Also is it something interesting to get higher current than 0.6A for this design??? As now with the fan and big heatsink i'm no more than 21°C on the aluminium surface....

0.6A is already higher than sufficient but at the same time ensures 16 Ohm headphones connected while the output resistor is 0 Ohm will not clip a-symmetrical.
The extra heat isn't of any advantage.
The distortion for lower impedance headphones will decrease though so in this aspect some measurable benefits MAY be had.
Most distortion comes from the non-feedback tube and is the one that is liked so much !

If i do understand the schematics, the MOSFET gives the sound voltage and the loop from the LM317 to the headphone resistor is the current source? Is taht true?

The tube supplies the voltage gain.
The IRL merely 'follows' it (at least it should do that perfectly but doesn't in real life) and is used to 'transform' impedance in this case.
The LM is only a (constant) current source in this case and behaves as described above.

How much voltage do we have at the point between IN of LM, + of 2200cap and out of the MOSFET?

IRL = 2V (approx), IRF = 4V (approx)
Hence my choice of IRL as it increases output voltage swing provided the bias VOLTAGE is set at a different point.
You already mentioned this in your pdf.
There are also other benefits which are 'charge' related, as a MOSFET is a capacitive controlled component (voltage controlled current source, similar to a tube/valve) where as a transistor (LM317 = transistor based) is current controlled

Of course the above explanations are kind of 'basic' and in reality some more aspects also play a role and are more complex as explained above.

The second issue is the audibility of the individual aspects and the role they play (in essence how much influence each aspect has).
This aspect (actual knowledge about the parts and what they exactly do/are capable off) is the SOURCE of all the subjective/objective differences debate and controversie.
How much one (feels?) they know about the workings of electronics/parts seems to determine how heated the debate becomes.

The LM317 appears to be a single component (just like an op-amp does) but is a very complex component in reality.

[Deleted]

Mar 11, 2012 23:58:17 GMT floriangerard51 said:

here is the link:

dl.free.fr/mf00QMLw4

Some of the explanations, calculations and reasoning in the pdf are not technically 'sound'

[floriangerard51]

And if you consider to increase the perf of this small amp, what it the first change that can be done? The triode tube 12au7 is a great deal has it woks with low voltages...so there is the MOSFET and the Lm.

Changing the way the current source ( lms) is working for example??
Using the tube with higher voltages? Like normal tube design with 160v?

[Deleted]

The 12AU7 was not intended to work on low voltages (15V anode voltage in this amp).
The 6DJ8-ECC88-6922 is better suited (also not intended for these voltages but were designed for lower anode voltages) these, however, are not pin compatible heater wise.

Higher voltages will increase performance (lower distortion) but means lowering idle current as well and changing some parts (and voltage ratings of caps)
An example is the upcoming Horizon as this works on 48V instead of 24V.
Some special measures have to be taken when increasing the PS voltage.

[floriangerard51]

is there a thread on this new amp? Horizon?

[Deleted]

Nope... not yet,

The PCB is on it's way.
We are sorting out the heatsinks as it needs bigger ones than the Sunrise.
I am going to determine the final values and the intention was to pass it around the usual suspects or those interested for evaluation.
After I am finished with it and Jeremy whipped one up they enter the market.

It's basically the Sunrise-II but on a higher voltage
rockgrotto.proboards.com/index.cgi?board=m&action=display&thread=7847
The same PCB and looks.

[floriangerard51]

Ok that's a great challenge! If you want some beta testers for the pcb, I can order all the parts and try to test it....

I'm currently testing my linear psu which doesn't work :-( I dunno if it's due to the lt 1083 or not.... If you don't bother I'll ask you somes questions late today...I'll get all the voltages and tests write down to troubleshoot...

[floriangerard51]

here is the Tutorial for the mod :
www.mediafire.com/?ra9m7q31rs5jyii

[floriangerard51]

I don't understand ?

Quote: Some of the explanations, calculations and reasoning in the pdf are not technically 'sound'

Can you explain me? Should i change some things on the pdf? Have you seen big mistakes?
I'm really sorry for my very bad english ;-) i hope you understand the text ;-)

[maxbara]

Hi, i followed your Bravo tutorial for the first part, I first done the crosstalk mod and everything ok,

Then i made the 3 caps and the irf510 mods and since then every time I turn on the amp after a few seconds and a lot of crackles from the left ch I finish with a burned MOSFET no more sound and a burnt smell...
i have no idea from where to start to check what could be wrong, can you help me?
ciao
Max

[Deleted]

maxbara
I have passed on your query to Frans, who as the author of these modifications, and a very experienced E.E. is the best person to advise you.
Regards
Alex

[maxbara]

Ok Thank you

[siles1991]

Was working on my bravo and replaced the big cap with a nichicon 6800uf/35v everything worked fine until I finished soldering my irl510pbf...right side won't heat up and tube won't heat up no sound from either channel.

[solderman]

Lat night I finally replaced the stock IRF630 with IRL530 and the stock LM317 with the LM317at and WOW,..what a difference. Detail in the instruments I've never heard before. The highs really shined thru. However I'm worried about how hot these 2 compoments are running and life expectancy. I have plenty of fans around but I do want to keep the appearance tidy. The 1st stock item to go was the switching power supply, what type of moran uses a switching supply to audio circuits. It's something of overkill I useing a Sola 24-024t 24vdc @ 2.5 amps and bye bye annoying spikes and noise from the power supply. Afther I changed out the MOSFET and LM317 stock regulators with LM317AT's,..I took the next logical step. prefering to do one mod a time to see whats really changing what. I replaced the 2 1000uF output capacitors to 2200uf Nichicon 25vdc units and the bottom end really opened up, I am really happy with the bass now being a little extra to match the extended highs I got with the MOFET's replacement. Can any tell me (as I'm getting differant reports on this matter) should I have used thermal paste on the MOFET's and LM317AAAAAT's, they use to run warm to the touch, but now I cant keep my finger on them for more than about 2-3 seconds without a big hot pain rolls up my finger, any thoughts. Just asking, the only stupid question is the one you dont ask, many thanks, Audie Milligan Aguirre.

[Deleted]

I always use thermal paste on devices like that.You need larger heatsinks now due to the higher current draw.
They are running too hot at present.

Alex