Bravo / Indeed Headphone amplifiers

[Deleted]

Andy,

If you hold up a while, Frans is deconstructing/reconstructing a Bravo for me so there may be some ideas there.

The changes that he's working on involve quite a lot but there may well be some simpler ideas there too. I'll then do a comparison with a stock Miridy and Indeed.

Ian

[andy]

Ian,

sounds good, i will start by stripping everything down, going to have to do that anyway!

I can even get the case built, not sure what case i am going to use but i will start looking.

andy

[PinkFloyd]

Apr 5, 2010 20:22:08 GMT andy said:

Ian,

sounds good, i will start by stripping everything down, going to have to do that anyway!

I can even get the case built, not sure what case i am going to use but i will start looking.

andy

Hi Andy,

I can help you out with caps..... the Panasonic NHG (105C) 1000uF / 35V sound excellent.... PM me your details, I'll send you a couple FOC just pay for the postage.

Mike.

[Deleted]

Andy,

Check out oohms link (5 posts above this one) for some of my pointers too.

Frans

[Deleted]

My modded Bravo arrived from Frans a few days back and my wife got it out herself while I was away and had a sneaky listen. She then emailed me in Germany to inform me that it had arrived and in her opinion, was a lot better!! I was a bit miffed at the fact that she opened my present but also miffed that I couldn't get to hear it!!! Very frustrating.

Result was, I'm an immigrant now. I got into England through it's back door .... I was so desperate to hear it!!!!

Thanks Frans. You are a really nice guy and I appreciate the emails I got while I was away. They really made me homesick actually because being away isn't a favourite part of my work if I'm honest.

The amp itself looks FABULOUS. Frans added a metal plate at the bottom, lifting the board and put some feet on. The result is it's stopped the ice rink behaviour and is now bottom heavy and so much more stable. The bottom plate serves an electrical purpose and wasn't done for that reason. Frans will no doubt explain. In my opinion, the added weight at the bottom is a great bonus (along with what it does for the sound).

At my request, Frans put a lot of the light out. I didn't particularly like looking at it although I can understand people liking it but for me, it smacked of glitzy kidsy stuff so now I have a red light at the back which is enough to let me know that it's on and the delicate glow of the tube itself. Much better for me. You bedroom listeners with wives who try to sleep while you're listening would appreciate this!! Frans has also got rid of the poxy on/off switch at the back and replaced it with something better. Desperately needed.

For me, its more industrial look is better. Then again, I like that kind of look since it looks tougher and as though it will stand up to more than it did before.

I also know that Frans changed capacitors but the interesting part is how he went about changing its frequency response. He is aware that I liked its sound from the start and didn't want to completely alter its original character, even if that meant that the frequency response wasn't ideal. He must have done a lot of pondering over this because I know that he was considering putting a switch in to enable me to go between two types of response at one point!! Me being my usual self asked Frans to just do what he felt was best for its sound. I was curious to see how far up it could go actually, but Frans felt that its signature was altered too much and so he reverted to a compromise. It's more extended than it was, but not as extended as it could be.

Well, I had the wife's message so you can imagine what I did when I got in the door........

Headphones on and have listen. I put the Miridy on beside it to compare.

The gain has been lowered thank goodness and the hiss has GONE. It is lovely and quiet. I am programmed for hiss and hum so for me, it's one of those things that need to be low. I developed it through the years and it won't go away. However, the hiss before was at such a low level compared to the volume that it was never really a big issue. One thing that was for me though was the interference and electrical noise that I was getting. There were literally only two places in my house where I could use it. Now, it's deaf to external interference. That's where (I think) the bottom plate comes in. (and probably the lowered gain)

Frans has done a great job with its sound. Actually, short term listening and comparing with the Miridy (stock) it's a lot better. It's more open. It's retained the bass impact. The sound is more extended so you hear cymbals and the 'after splash' much better. (The decay) The bass impact may have diminished very slightly or that is just the effect of having a different top end response. It definitely feels as though wax has been taken out of my ears.

Not only is the sound signature more open with more up top, but it places sounds better as well. That may be the result of having a better response in the treble since the sounds that we use to identify placement are often quite high. So when a cymbal is struck, you hear the 'hit' followed by the cymbal sound itself. The 'hit' often gives the cymbal's locality away and now, the Bravo is more accurate in this respect.

Frans, thank you SO MUCH. You have without a doubt, improved the Bravo big time. I honestly wouldn't have minded you going up as far as you originally planned but I know that you were nervous of changing the sound sig too much.

The big improvements -
More extended.
More open sounding.
More revealing in terms of headstage. (bigtime actually)
original slam has been retained although there may be slightly less 'boomy' bass. In other words, it's cleaner in the depths!!
The volume control can actually be used properly.
It doesn't pick up noise.
It's lost the cross talk completely. (That probably cleans up the sound a lot) - I never noticed it before but I tend to listen fairly low.
My original turn on rustle sound has disappeared.
It warms up 4 times as fast as the Miridy.
It doesn't have the 'cheap' glow look.
It's bottom weighted with feet.

Frankly, it's a better listen.

Frans, send me your hybrid!!!! ;D and a bill for the parts.

You have done a fantastic job on this amp. You have without a doubt improved it and I have compared side by side with an amp that was exacly the same. Now I'll do some extended listening because I do like this amp and now it just got better.

[Deleted]

Hi Ian,

Glad you finally got back.
Don't you hate volcano's now !

Glad you liked what I did to it.
Feel the difference in temp between the Miri and the Bravo that seems about the only thing you 'missed'.

the bottom plate acts as a screen AND cooling plate for the LM317's which have moved to the bottom plate.
It also ads some weight and stability.

No bill for the Parts Ian ....

@ Mick
If you are still interested in having one of your amps modded drop me a P.M.

[Deleted]

Apr 22, 2010 18:26:54 GMT @solderdude said:

Hi Ian,

Glad you finally got back.
Don't you hate volcano's now !

Glad you liked what I did to it.
Feel the difference in temp between the Miri and the Bravo that seems about the only thing you 'missed'.

the bottom plate acts as a screen AND cooling plate for the LM317's which have moved to the bottom plate.
It also ads some weight and stability.

No bill for the Parts Ian ....

@ Mick
If you are still interested in having one of your amps modded drop me a P.M.

Hi Frans,

At last - I can see your mail on a screen not a mobile phone!!!!

I'm in hiding now. I crept in on my own boat. Instead of going to Dover or anywhere like that, I did a Dunkirk and this time, Churchill didn't stop them on the beaches. They tried. Did some fishing too.

The whole thing was pretty poor, but I was lucky in that my replacement couldn't get out either until now. There's no way I'm going around Europe because of a puff of smoke.

I didn't feel the temp. It was something that I wasn't keen on at the start since I felt that it would shorten its life but you are right. No more cooking over the outputs!! Was planning on a barbie with music.

OK Frans ... beer money. You spent a lot of time sorting it out.

Ian

[Deleted]

Hi Ian,

Have you had time to compare the switch-on 'pop' sound between the 2 (use cheap or expendable HP's for this test) didn't have the chance to compare the 'before' and 'after' mod switch-on pop.
It should be less 'unpleasant'.

Yes.. you can forget about the Barbie with the Bravo now.
It runs lots cooler.
You can still cook on your Miri though !

Should I find the time for it I will make a pdf with the mods.

[Deleted]

Apr 22, 2010 21:24:54 GMT @solderdude said:

Hi Ian,

Have you had time to compare the switch-on 'pop' sound between the 2 (use cheap or expendable HP's for this test) didn't have the chance to compare the 'before' and 'after' mod switch-on pop.
It should be less 'unpleasant'.

Yes.. you can forget about the Barbie with the Bravo now.
It runs lots cooler.
You can still cook on your Miri though !

Should I find the time for it I will make a pdf with the mods.

Now you've mentioned it Frans, I just tried it. There's an initial click which isn't too loud and no buzzing/pop noises from the tube on the Bravo.

The Miridy literally takes about a minute to come on and the headphone is dead until you get a plop in on the right speaker followed by another plop in on the left about 15 seconds or so later.

The lack of noise of the Bravo is immediately apparent. At full whack, there is NO noise at all. It's also not RF sensitive any longer.

You did a great job on this Frans. It's really opened out but still has a lot of it's former character. It's still a powerful beastie as well, even with the gain lowered. I'd say it's less tubey sounding with the top lifted.

It's cleaner sounding without a doubt. I've been listening for quite a few hours today. I'd say, a little less 'tip' towards the bass - a bit like the response has been lowered at the bottom and raised in the top with a clear mid-range. I feel that you can actually hear further into the sound in comparison to the Miridy which now feels slightly 'compressed' in sound in comparison. The Miridy delivers a fat bass but perhaps that covers up other details?

You'd better be careful - you'll get thousands of amps being offered to you because it has definitely gone up in terms of sound a great deal.

Ian

[Deleted]

For those that are interested in the changes I made in the schematics of the Bravo/Indeed/Miridiy/Sijosae amps.


(original)


(modded)


You can use the original PCB but have to cut some traces and re-route some wiring, add and replace some parts.
The LM317's cannot remain on their current (very small) cooling fins anymore and have to be placed on a much larger cooling surface for this to work.

Maybe a tutorial in the future.

[mrB]

Thanks Solderdude for your work on this amp. Ian seems to be very happy with the result. I feel confident now to go ahead with some modifications to my Indeed version of this amp.

Having read about the effect of swapping the IRF630s for IRF510s or IRL530s I think I'll stay with the 630s. If I still had my HD650s I'd probably have done the swap because they are bass-heavy, but I am back to using my ER-4S IEMs, which are nicely balanced on the Indeed as it is. Any increase in highs would make them too bright for my taste, and any loss of bass would be unwelcome.

Regarding the independent supply for the filaments, I had been thinking just to feed them from the 24V rail thru a 5 watt 60 ohm resistor. Is that too simplistic? Would it create any problems? (I'm using a PCC88 and I believe I need 300mA flowing).

I see you have changed the output resistor from 47 to 68 ohms. What effect will that have on the frequency response? The output coupling capacitor remains the same value. Which specific brand did you use? and why?

My Indeed seems to have a log pot on the input, so I may not need the extra 2K2 divider to ground?

Re the LM317s; I have been running my amp with the top perspex plate removed to allow for more convection cooling. Will I be able to continue like that if i keep them in place but change to the 15 ohm resistor as in your schematic? How much more power will they be dissipating? Will the LM317s need a different value resistor?

Hope you don't mind me bouncing these questions off you. The last one is: can you point me to a reasonably-priced one-stop online shop in Holland or Germany who can supply all the bits and pieces I will need for this adventure? If I knew specifically the description of the various components that you chose for the job I would try to get the exact ones you used.

[mrB]

I just read about using cathode bypass capacitors over at the Bravo thread on Head-Fi. What do you think about this issue?

www.head-fi.org/forums/f5/bravo-audio-funny-looking-little-tube-amps-444400/index48.html#post6570489

[Deleted]

freq range of the amp (-0.5dB) with IRF630 = 10 kHz
freq range with IRL510 (IRL = 2x better in high freq then IRF) (-0.5dB) = 40 kHz
THIS is where the biggest improvement in sound comes from.

Distortion is lowered a lot by taking the filaments out of the audio path and crosstalk too.
The LM317's really perform very bad when operating at their minimum voltage.
This occurs somewhere in the negative half of a sinewave only... NOT good and can even be seen clearly on a scope !.
This (filaments in audio-chain) was a very cheap and not so good way to make an amp with as few as possible parts.

the suggested resistor in series with the filament would dissipate around 5.5 Watts.
a resistor with a wattage of at least 10W is recommended.
It will become VERY hot !
This is why I use a (switching) 6.5V regulator (TRACO TSR 1-2465), it remains cool and total current consumption is much less as a bonus too .
It needs to be mounted directly on the Power supply cap with shortest wires possible to this cap.

68 Ohms output resistor effects vary on the used HP.
the amp itself now 'sees' a minimum load of 100 Ohms (when loaded with a 32 Ohm HP)
slightly less distortion from the output stage as a result.
used MF Multicomp (supplied by Farnell).
Any MF > 0.4 watts is O.K. I.M.O.

The 2k2 is to make a lin pot act more like a log pot and in the process lowers the gain/max output also a bit.
More travel on the pot/better tracking.
Not needed if a log pot is installed.
lin pot has a B on it, log pot has an A on it.

You can only change to 15 Ohms (effectively halving the current in the class A output stage) when the filament has it's own power supply.
The LM's will be dissipating about 0.7 watts in the modded design.
originally they dissipate 0.4 watts so they will be running 10 to 15 degrees hotter if mounted on the same heat-sinks.
The 15 Ohm resistor itself dissipates half the power of the current of a 7.5 Ohms resistor (voltage is the same 1.25 Volts)

I get my parts from Farnell as I do my orders there for my workplace too.
Fast and excellent stock but not cheap.

I use Panasonic 105oC caps.
Cheap and good quality

I do not see much advantages of putting even more electrolyte caps in the audiopath (cathode caps)
When these caps are in place, there would be slightly more gain.
Also there will be less lows if the capacitance is chosen too low (> 220 uF)

a note:
These amps are VERY sensitive to noise on the power supply line.
I recommend using a linear regulated power supply instead of the standard SMPS.

[mrB]

Thanks for this detailed advice. I am well equipped to proceed now.

kind regards

[schawo]

Hello,
Did anyone try E80CC tubes in Bravo V2? Could they work?

[Deleted]

E80CC should work in the Indeed G2 in 12V setting (cannot be used in normal Bravo/Indeed/Miridiy/Sijosae amps that take ECC88/6922 unless you reroute some copper traces on the PCB.
The 12AU7 version of the Bravo should work with the E80CC.
Because of lack of the bias pots (there is a solution) the bias might NOT be in the correct range.

The gain will be less (not a bad thing as it is very high to begin with)
ECC88 = 12.5mA/V E80CC = 3mA/V

post your findings

[schawo]

Thanks. I'm still waiting for my 12AU7/ECC82 Bravo V2 to arrive. I will try the E80CC, I have some fine ones.

[Deleted]

Hi Guys,
Being slightly concerned about the effect of it's normal, hot, running temperature on the longevity of my Bravo V2 I invested in the following items as a trial: -

cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=380210141871&ssPageName=STRK:MEWNX:IT

and

cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=230442467934&ssPageName=STRK:MEWNX:IT

I coupled them up and parked the fan about 5 or 6 mm away from the LH (as viewed from the front) side of the G2 and left everything on for about 4 hours.
Result:
Pros - the G2 was kept warm, rather than hot, such that I could safely remove the valve with my bare hands without any problem.
Cons - in silent intervals in the music the fan was slightly audible from my listening position 3 metres away.
I don't know if this is of any interest but I toss it into the knowledge pool for what it's worth.
Dave.

[Deleted]

May 1, 2010 11:26:39 GMT @davek said:

Hi Guys,
Being slightly concerned about the effect of it's normal, hot, running temperature on the longevity of my Bravo V2 I invested in the following items as a trial: -

cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=380210141871&ssPageName=STRK:MEWNX:IT

and

cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=230442467934&ssPageName=STRK:MEWNX:IT

I coupled them up and parked the fan about 5 or 6 mm away from the LH (as viewed from the front) side of the G2 and left everything on for about 4 hours.
Result:
Pros - the G2 was kept warm, rather than hot, such that I could safely remove the valve with my bare hands without any problem.
Cons - in silent intervals in the music the fan was slightly audible from my listening position 3 metres away.
I don't know if this is of any interest but I toss it into the knowledge pool for what it's worth.
Dave.

Hi Dave,

Flew back from Sheffield last night!! Read the reviews!

I have a metal base on the bottom of my Bravo that Frans altered and the heat just doesn't build up at all. In fact, it's pretty cool.

He did a helluva job on that amp. Less noise, more treble extension and a 'perceived' slight lowering of bass level. I'm not sure whether the bass thing is a result of extending the top a bit further so you perceive the sound differently. It has a quite different sound to the other two actually. The longer I listen, the more obvious it becomes.

I still like them all though to be honest. I'd like to put a posh tube in them at some time.

Ian

[Deleted]

Hi Ian,

May 1, 2010 12:45:24 GMT @iancraig10 said:

Hi Dave,

Flew back from Sheffield last night!! Read the reviews!
Sorry Ian, we don't take the local 'rag' (Star) any more so I haven't seen or heard any reviews - I take it that the gig went well then? I hope a lot of money was raised for the DJ's charity, which is the thing that matters most
I have a metal base on the bottom of my Bravo that Frans altered and the heat just doesn't build up at all. In fact, it's pretty cool.
I'm a bit puzzled about the location of the metal base and how it extracts the heat. Obviously it can't be in direct contact with the PCB so what is it in contact with other than the corner posts?
I still like them all though to be honest. I'd like to put a posh tube in them at some time.
So would I but knowing nowt about valves I have no idea which ones would fit and which would need 'tweaking from 6 to 12 (v?). So many of them have very similar, almost identical, part no.s, how would a numptie like me know what is what?
Ian

Cheers,
Dave.

[Deleted]

Dave,

6n23's or 6922's are really good. I was fortunate in that I had one on its own here and I just stuck it in. Mike has plenty I think.

Immediate differences were more bass impact and perhaps a tad sharper focus. If you have been listening to the stock valve for a while, you'd notice the differences quicker but if you've only had it a short while, you may think that it sounds very similar. The changes are subtle but work for me.

The nice thing about those amps is the ease with which you can take out a valve and stick a new one in. Ideally, you could adjust the bias, but it's no big deal if you can't. (As long as the tubes aren't getting too bright!!)

They're not too expensive and are a quick way to tweak it.

Sorry, the plate thing is (I think) some kind of earthing system. (Who knows) but he has got it running cooler without a doubt. It has another advantage with the plate in that it's bottom heavy and so more stable - especially with feet attached. It also just doesn't pick up RF interference now which was a terrible problem for me at the start. Probably my house with all its radiating contents!











Ian

[Deleted]

The base plate is also a much larger heat sink for the LM317s which run hotter after Frans mods.

[Deleted]

Sorry, the plate thing is (I think) some kind of earthing system. (Who knows) but he has got it running cooler without a doubt. It has another advantage with the plate in that it's bottom heavy and so more stable - especially with feet attached. It also just doesn't pick up RF interference now which was a terrible problem for me at the start. Probably my house with all its radiating contents!

Ian,

I have just made an Ali base plate for mine before i send it off to Frans. looking at your photo`s i need to make some spacing pillars to provide the gap between base plate and pcb, can you tell me what that gap is in mm please, looks about 10mm. Thanks.

Mick.

[Deleted]

Hi Mick,
Hope the neck repair is going well and you are now allowed to nod your head vigorously . Regarding the spacing pillars between the original base and the Frans heat sink base, I'm very probably preaching to the converted but you do know that Maplins sell brass and nylon/plastic ones of various lengths for peanuts (don't you? ;D ) . Not worth making your own if you have a branch of Maplins handy - just a thought .
Dave.

[Deleted]

May 1, 2010 17:15:21 GMT @davek said:

Hi Mick,
Hope the neck repair is going well and you are now allowed to nod your head vigorously . Regarding the spacing pillars between the original base and the Frans heat sink base, I'm very probably preaching to the converted but you do know that Maplins sell brass and nylon/plastic ones of various lengths for peanuts (don't you? ;D ) . Not worth making your own if you have a branch of Maplins handy - just a thought .
Dave.

Hi Dave

Neck ok thanks, too much of it now, so the wife say`s!! ;D

Thanks for that, but i already have made a sets of extended pillars out of s/steal for my G2, and a couple which have gone out for test, so will only take a few minutes to modify a set i have sitting here for the Miridiy.

Mick.