Bravo / Indeed Headphone amplifiers

[Deleted]

Hi Guys,
To be absolutely honest I guess this appeal is really aimed at Frans . I would be interested in having one of the 'Puzzle Dock' modules if I could USB connect it up to my Indeed G2 amp, but it does not have the necessary female USB connector, so .....
Frans, how difficult would it be for you to put one on my G2 for me, assuming you could be persuaded to do so, and have you any idea how much it would cost me?
Cheers,
Dave.
On the other hand Frans, feel free to use whatever language and words you choose to tell me what you think .

[Deleted]

The i-pod doc's function is for routing the audio to the equaliser which in turn routes it to the amp.
they used USB connectors but there will only be Left, Right, Common (ground) and +24V? or perhaps 5V? running thru it.
The IC on the USB doc is for the remote control.

The G2 would have to be fitted with a 24V/5V out and the input on the back or 3.5 mm will have to be connected to the USB plug on the doc.

I would simply use an line out audio out connector on an i-pod and simply connect it to the G2.
There are remote control/doc with line out that will perform equally well if not better.

the passive equaliser only needs power for the LED's.

[djmattm]

Yes sure, as soon as it arrives i'll try it with my ipod chinese el cheapo dock station, i'm sure it will work, but i asked the price for the module and it's 35$ shipped, so yes it looks good so it can be a nicer solution

[mm38]

hi all..
i am newbie in this forum, and it is my first post

i wanna ask some question bout bravo / indeed, please help...

i use onkyo se200pci Ltd as a soundcard, and my headphone is AD900

i have a little budjet to buy ampli, so i decide to buy bravo or indeed
but i dont have skill to modding and dont have time to do that

so, plesae give me some advice, which ampli is the best to pair with my AD900?

i mean, bravo or indeed? and which type?

i will buy it, and use it directly, without do some mod...

thx for your help

[Deleted]

Consider the many 'Cmoy" amps on ebay too if you look for quality without modding.

The AD900 is pretty 'toppy' so any of these amps like Miridiy, Bravo, Indeed, Muse and similar looking ones perform (about?) the same.
You would at least have to be able to adjust the amps properly for a good sound.
These are not properly adjusted out of the factory.

If you bant a bigger bandwith (more highs) look in the add if they now use IRF510 or IRF610

You should consider the Cmoy alike amps if you do not want/like/can adjust at least the anode voltage setting.
The price range/budget will be about the same.
No tubes though..

The Bravo V2 (12AU7) cannot be set and is dependant of the tube quality.

[mm38]

once more question


i use a good soundcard i think, onkyo se-200pci Ltd

so, if i use the G2, it will bypass the SQ from soundcard? or it will improve that?

and my headphone is AD900 (35 ohm), is it any problem if i use headphone with small ohm like AD900 into G2 ( the ampli with big power an can support to 600 ohm)

i ask bout this again because some people told me, my AD900 will be broken if i use ampli with big impedance output like G2, is it right?

thx

[Deleted]

The G2 should be connected to the line-out of the card, not phones out.
In this case the soundcard's own headphone amp will be bypassed.
If you use the headphone out of the soundcard the SQ will probably only be slightly better.

AD900 is no problem with G2.
It will drive headphones from 32 to 600 Ohms.
the G2, however, is better suited for higher Ohmic headphones with regards to distortion.
In order to get good SQ you will HAVE to adjust the Anode voltage setting properly as in most cases the factory setting is FAR from what it should be.

This amp does not have a big enough power which could destroy headphones.

[lazybum]

Hi solderdude

I'm new to this forum and new to diy as well. You mentioned the setting of "anode voltage". Does this refer to the bias adjustment that ive read? I thought it was called cathode voltage or are they the same? And there is absolutely no way to set in the V2?

And you mentioned that the amp does not have a big enough power which could destroy headphones. May i know what does that mean? Would it mean that using a low ohm headphone with the bravo can shorten the headphone's lifespan?

edit: ok i think i found the anode voltage mod that you posted on the bravo mod thread. Sounds rather complicated though so i think ill attempt any modding only after my exams when i have more time. So just to clarify the anode voltage mod = bias adjustment?

[Deleted]

Oct 7, 2010 12:53:07 GMT lazybum said:

I'm new to this forum and new to diy as well. You mentioned the setting of "anode voltage". Does this refer to the bias adjustment that ive read? I thought it was called cathode voltage or are they the same? And there is absolutely no way to set in the V2?

And you mentioned that the amp does not have a big enough power which could destroy headphones. May i know what does that mean? Would it mean that using a low ohm headphone with the bravo can shorten the headphone's lifespan?

The anode voltage is the voltage that is to be set properly.
It's also called the bias voltage sometimes.
This is done by adjusting the pot in the cathode circuit (except for V2)
It actually bias-es the MOSFET output stage behind the tube in it's proper working point.
Indeed with most tube amps one sets the cathode voltage and calls this the bias voltage.

The only way to be able so set the anode voltage in the V2 is by replacing 2 resistors in the anode CCS circuit by potmeters.
the HOW TO is mentioned in a thread in the 'Bravo 12AU7 Mods and Appreciation' thread in the 'DIY' section.

These amps simply do not have a big output voltage + the output resistance of these amps (less true for G2) is high enough to safeguard blowing of voicecoils.
I take it no-one likes to listen to ear shattering levels and turns the volume down before reaching levels that can destroy the headphones.

The maximum output voltage is relatively low (comparable with a Cmoy type amplifier running on 1 or 2 9V batteries) of about 4V eff.
The better headphone amps (like the Panda) easily reach 24 to 30V peak-peak , which is about 8 - 10V eff.
If the output impedance/resistance/Z of these higher output voltage amps is small enough (say anything between 0 and 22 Ohms) AND you are using 16 Ohm or 32 Ohm headphones they might burn out (the headphone drivers voicecoils that is)
Mind you the volume on the drivers will be very high in this case !
High Ohmic drivers are usually more delicate but because of their higher resistance should be fed with amps that can reach these voltages.

I would not recommend using amplifiers that can produce higher voltages then the 8 - 10V eff. output voltage UNLESS measures are taken like higher output impedances or some sort of voltage limiters are in place.

The biggest threat for destroying headphones is the presence of DC on the output.
Voicelcoils simply don't like it because the drivers do not vibrate and thus there is no cooling action like there is with large AC voltages (and thus swing) and give up quickly when this happens.
Trouble is you can't hear DC being there.
This can happen when a dual voltage supply becomes defective (or with C'moy amps WITHOUT a rail splitter 1 battery coming loose from it'scontacts).
Amps with an output capacitor will only give a loud 'plop'.
Only when the output capacitor fails and becomes a resistor (never seen it happen in an output stage) this can destroy a headphone.

The Indeed alike thingies all have output capacitors.

a small note of caution is in it's place though.
WHEN the anode voltage is not set properly the output signal will NOT be clipping symmetrically resulting in a DC voltage effectively.
This is not going to be a huge, destroying DC voltage and the amp will not be sounding very pleasant either and at very high levels, so unlikly unless operated unattended at max volume.

I hope it's not a too technical story..
If it raises more questions don't hesitate to ask.

[lazybum]

Thanks for the write up! I'm a college student so I only have college level physics knowledge but ill try my best to understand.

Ok so just to check my understanding... hooking a low impedance headphone with an amp with low output impedance and high voltage output is dangerous because it may result in too high a current (V=RI)? And that this high ac current can become a square wave which is harmful to the drivers as it has DC characteristics?

But for the V2 at low volumes there should be no danger am i right?

I'm rather clueless with regards to the bias voltage though as I actually have absolutely no idea how a tube amp works (or how an amp works for that matter). But its ok, I think i have a lot more to read up on by myself first before i attempt anything.

[Deleted]

In short..

If there is NO distortion there is no chance of destroying headphones with it.

a squarewave in itself is not very harmfull to headphone drivers.
It consists of a ground sine wave with a certain distribution of harmonics with a (higher then in normal music) presence of higher frequency sinewaves.
It is for LS though as the HF energy is high and a Woofer might be able to handle 100W easily but a tweeter with its very small voicecoil may only handle a few Watts.
For Headphones there is only 1 voicecoil so squarewaves don't hurt it.

What is problematic when asymmetric clipping occurs is that a sinewave has a negative side and a positive side.
Imagine the top side to have a voltage of 6V and the bottom side 2 V (and looking like it's a squarewave.
In this case the average voltage has an 'offset' in the direction of the positive side.
This happens all the time (when clipping in this extreme example making it sound unbelievably crappy and makes you want to turn down the volume) and because it is an average voltage caused by AC not being symmetric it passes the output capacitor.

and yes,

hooking up a low ohmic headphone to a (higher) voltage amplifier WITH a low Ohmic output impedance will be able to blow the drivers.
If you had those headphones on you will probably also had taken them off as the music level would be ear shattering.

[lazybum]

Ok i think i somewhat understood that. My lack of knowledge about the technical terms does make it a bit confusing so i'm going to have to look them up first.

By the way on my V2 i'm noticing a buzzing sound with my highly sensitive headphones plugged in. However, the sound disappears if i touch any metallic part and hold my hand there (e.g. the headphone jack or even the metal pillar thingy supporting the acrylic plates). Is this some grounding issue or something and is there a simple solution to this?

[Deleted]

Looks like grounding and or so called 'common mode' interference that is coming from the power supply or something that has a transmitter very closeby (cordless phone or electronic equipment)

Try to listen to it with nothing attached but the headphone and power supply in different spots in the house at minimal vol pot setting and maximum vol pot setting.

Rabbit has experienced the same things and the amp not having a real (metallic or otherwise screening) casing is probably what is 'bugging' or should I say 'buzzing' at this moment.

[ruinevil]

So, I bought the Muse 6N11 Amp from Amazon. I believe it will be similar to the Bravo G1. I also purchased some IRF530's from my local electronics shop. When I replace the MOSFET, will I need to use some kind of thermal paste on the mosfet|heatsink junction?

[Deleted]

a very THIN layer of heatsink compound will not hurt.

How thin... just apply it on the part and wipe the excess off with a creditcard alike plastic card.
There should be hardly anything on it.

Also you can use a silicone insulation sheath (not mica) that stuff doesn't need compound.
If the surface is falt and the one you took out doesn't have the compound you can try without that stuff.

[ruinevil]

www.goodvision.com/tubes/

Other than the 6DJ8, anything else on that list usable in a MUSE 6N11 MK1 Amp?

IN BOX
6v6gt Â
ecc83/12AX7-A
ecc82/12AU7A
6679/12AT7/ecc81 Â
5t8
6bk7b
12bh7a

NO BOX
5879
6v6gt Â
6sn7gt
6.00E+05
6x5gt
6sl7gt
6k6gt
6sc7
6dj8/ecc88
6ba6
5br8
6av6
6cd6
bcb6
6c4

albany.craigslist.org/ele/2948986006.html

[Deleted]

ECC85, ECC86, ECC88 and it's equivalents (google these types and add 'equivalent' in the search line) will work.
This still makes up quite a list of tubes though.
ECC85, 6AQ8, 6L12, B719, ECC86, 6GM8, 6N27P, ECC88, E88CC, 6DJ8, CCa, 6922, E188CC, E288CC, 7308, 8223, CV2492, CV2493, 6H23, 6N23 for instance (list is not complete)

They need to be pin compatible 6V type dual triodes with current ratings between 300mA and 365mA, 12V tubes cannot be used.

so the answer to the list above = no

[mrarroyo]

Has anyone tried a 7DJ8 on this amp?

[Deleted]

probably someone already did,

I know the PCC88 (European type equivalent) has been reported to work on these amps.
Chances are the heater voltage will be well above 7V (run on 10% over-current) which means the LM317 will reach their less than optimal working conditions much sooner (read crossover type of distortion at lower output levels)

When heater modded the 7DJ8 and PCC88 will have a 10 to 15% under-voltage (current) on their heaters.
How much effect that will have on emission would have to be tested.

[mrarroyo]

Ok, btw I asked because we can find 7DJ8 for very reasonable prices.

[ruinevil]

ruinevil.com/mad_is_a_moron/IMG_20120622_225836.jpg
ruinevil.com/mad_is_a_moron/IMG_20120622_225908.jpg
ruinevil.com/mad_is_a_moron/IMG_20120622_225920.jpg

So this is the $50 Muse 6N11 from Amazon. I replaced the 6600 25V power capacitor with a 3300 35V one. And dropped some 470uf 16v caps across the red diode and hopefully the right places around the bias potentiometers. My PCB does not look exactly like the Miridiy, so I was wondering if my cap placement is correct.

Also, I will be returning the unused IRF510 and getting a pair of IRL530 (well the NTE version). I could probably talk the guy into giving me store credit for the IRFs, so what should I ask to replace?

I'm not a big fan of the main pot for the volume, what can I replace it with? What can I replace the power switch with?

Also the spacers and bolts are all 4-40. Just in case anyone is looking for that. I found a 1.25 inch 4-40 bolts/nuts bag at Lowes.

[Deleted]

You have the cathode caps in reverse polarity.
The + should be connected to the cathode the - to ground.
Because the voltage on them is very low they will have survived.
The one on the LED is connected correctly.

Go for IRL510 for even more highs extension.
The IRL530 will have a 20kHz -0.5dB cut-off point which is considered to be 'better' sounding.

The pot is probably a linear type.
Check the markings.. if it has a B in there it is lin type and you should replace it with an A type (log).
With a lin type pot the volume comes up quite fast on the first part of the rotation and hardly changes from the centre to full setting.

[ruinevil]

What rating potentiometer should I get, a logarithmic 10k? Currently it goes 0-1 = no sound, 2 click = faint sound only in left ear, 3 clicks listenable, 4 clicks deafening. I have never gone past 5 clicks.

Also... my hearing poops out at 17kHz... so 20kHz should be enough. The IRL510 does not have a generic version, though I currently have the IRF510 generics.

[ruinevil]

When I am trying to bias the channels with the trimpots, I can not get the channels to match above 13.05V. This is with the IRF630.

I've also noticed if I rise the volume past halfway with no input, the right channel is very noisy.

[Deleted]

log type is needed.
10k to 50k is all O.K.

IRF510 is also O.K. with IRL you can get slightly more output power, that's all.

about the 13V max issue read:
rockgrotto.proboards.com/index.cgi?board=b&action=display&thread=7174&page=3
from post #61 to #65.

The noise in one channel may point to a dodgy tube or one that has considerable leakage current to the grid (due to the low anode voltage)