[Gradofan2]

Quote:

Originally Posted by drarthurwells You are spot on about heat dissipation. The Bada's internal fan cuts on after 50 minutes or so - depends on the room temperature. I drilled some 5 MM diameter holes along the front edge of the bottom plate. I also tilt the rear of the amp about 35 MM or more higher than the front (put a piece of wood under the rear feet). This allows air to enter from the front of the bottom and exit from the elevated rear vents.

Did that help much... does the fan kick on less often?

 

[drarthurwells]

Quote:

Originally Posted by Gradofan2 Did that help much... does the fan kick on less often?

Not really, but it makes me think that it helps.

Like buying life insurance - does you no good but makes you feel better.
I have replaced them twice and now do not touch the tubes in the amp until it has been off for 12 hours or more. This allows all power in the circuit to dissipate. Here is how to replace a mosfet:

Be careful handling mosfets - can short them easily with static from your fingers.

To remove mosfet, first remove bottom plate. Then remove the fan (don't lose the 4 screws and nuts holding it in) to allow you to put bottom cover aside, or if you prefer, disconnect two wires that run from fan through the side plate cover, to the front of circuit board where it plugs in. Unplug it (may be difficult, some plugs have a vinyl glue covering) then pull it through the side and out the back, and put aside.

Remove 6 screws by the tubes and two screws holding the two Toshiba K1529 mosfets.

Lift cables (on each side of circuit board) out and up from the sides so the main circuit board can be lifted up from the rear where the mosfets are. Lift the board up allowing the front to remain down - tilt it up at the mosfet end. Put a screwdriver in, at the middle of the rear of the board, to prop it up at the rear so it is elevated an inch or so.

The installed mosfets have a insulator between the frame and the mosfet body, and have a small lock washer, then a larger flat washer, under the screw holding it to the frame. Don't lose any of these.

Attach a bare ground wire to your wrist that connects to the ground of you AC wall inlet (not the hot pin) and to the frame of the amp, when working on the amp's mosfets, or when handling new mosfets. This will prevent a static charge from your skin that could short the mosfet and ruin it. Do not handle mosfets unless you are grounded.

Now, snip each of the three pins of the bad mosfet, underneath the circuit board, close to the mosfet body and take the bad mosfet out. Then use needle nosed pliars or a tweezer to grasp the mosfet pins remaining in the circuit board while applying a solder iron on top of the pin, and gently pull the pin through the borad - be gentle so as not to damage copper cylinder inserts in each board hole.

Use a grounded soldering iron of about 40 watts with a pointed (not chisel or screwdriver) tip, along with a separate solder (vaccum) sucker, to remove all the solder you can from the mosfet pins (three per mosfet) from the top. A desoldering iron may also do this. You need the pin holes to be open and clear with no solder in them. If your soldering iron is not a 3 prong plugged grounded one, then touch the tip to the grounded frame of the Bada, to discharge any static, each time before touching the tip to the Bada/'s circuit board.

In putting in a new mosfet, take a new mosfet and (with a ground wire attached to your body) bend the three pins near the body of the mosfet so that they bend bend up (90 degrees) and toward the other end (another 30 degrees or so) of the mosfet body. Use two small pieces of tape on the sides of the mosfet insulator piece to attach the insulator piece to the bottom of the mosfet body, so the insulator will not drop off of it. Put the mosfet body down under the circuit board with the pins sticking upwards and slide the pins under the board, then upwards through the three holes of the board. Bend one (or more) pin tip to hold it in place so it won't slide out. Make sure the insulator piece is in place. Lower the board and screw the mosfets firmly in place, allowing the pins to bend in place as you force the mosfet in position to be screw it in place.

Take two 15V diodes and slide one each in the two outside holes of the mosfet pins so that ends of the diodes with the black bands is sticking upwards, away from the mosfet body. Do this for each of the two mosfet bodies.

Put the 6 screws besides the tubes in, and attach the board.
Solder each pin (with the diodes in place). Briefly touch the tip of the iron to the frame edge in order to ground it and remove static, each time you go to solder a connection. In soldering the pins of the mosfet, try to get the solder to wick down the pin to the other side of the board for good conductive contact with the other side of the board. Now join the two ends of the diodes together (where they come from the black banded side of the diode body) and solder the joint to bridge the middle pin of the mosfet.

Put the two cables on each side in place so they are inside the bottom plane of the frame. Run the wire from the fan through the side plate to the front of the board and plug it in. Replace the bottom cover.

 

[tbonner1]

Thanks Art for keeping this thread going with ongoing support.

I spoke with Snowy(at Cattylink) and he suggested I wait until after the China holiday is over around Oct . 10 if I order from him. I still may try Pacific Valve as they may be easier to deal with if I want to return it.

You were right about the MG Head mk III, it is good and better than the Ming Da 66. Cleaner throughout the treble and midrange with bass not as wooly as the Ming.

Glad you like the Xiang 708. I think it is so simple with short signal paths the amp gets out of the way and it allows the tubes to sound as they should. The case, boards, volume pot and other parts leave something to be desired.

You are also right on about the AKG 701. I want to love the relaxed Senn 650 but the bass is a bit too strong and midrange a bit too dark and laid back. The Senn 650 with the MG Head Mk III in OTL mode is the most synergestic combination I have ever heard, they both perform above and beyond.

Not one poster on Headfi has been as forthright as you in proclaiming:

1-The 701 is the (best dynamic) headphone at this moment.

2-The clear value of the chinese amps when compared to the old school tube amps.

You have saved countless people huge money and alot of time.

 

[Black Stuart]

Hi,

I have owned a PH12 for a few months now and would have to agree wholeheartedly with Art that this is one cracking h/amp - whether it is the best, I don't know - I hav'nt listened to them all. I bought this h/amp as a relatively cheap way to experience hybrid amps.

I own a WAD HD83 which is a SET amp using the brilliant Mullard ECL 83 valve. This has been heavily modded with Silmics and the only two signal path caps have been changed for Dynamicaps, extra fast diodes and the Alps pot has been shunted.

As standard, I was not that impressed with the Bada - everything was there but muted/shut in. After eyeballing a thread about power cords, I decided to try my homebrew PC I use with my CDP PSU.

WOW what a difference - now the amp had breath and life. Instruments clearly defined, piano ( a very difficult instrument to portray) was piano, guitars were guitars.

With this change of power cord I simply cannot understand the negative comments made about this h/amp.

Changes made - I have shunted the pot and I am currently using Vishay Dale 1W, 47K (nothing fancy): there are two pairs of caps that are in the signal path, these are Solen and I don't like them, maybe they are fine in speaker x/overs but IMO are no good here. I have bought ERSE/Mundorf M-cap Audiophiler and Dynamicap to try.

I changed out the two 1uF x 250V for the Mundorf and this within two days of burning in had a pronounced effect on the sound. I have never used Mundorfs before and I am very, very impressed with the sound. It is a cross between the best polys and PIOs. I have since changed out thw two 2.2uF x 250V for Mundorfs - the difference is not so great but again a positive change.

I have yet to try the ERSE or the Dynamicaps, these latter I know from my HD83 h/amp.

Unfortunately because of the cramped conditions within the Bada (why do designers do this) more changes will be difficult to do.

A big positive is the over-rated mains tranny - this is always a positive, it means there is so much headroom for the amp to operate in.

With these changes this is a star buy. Others may prefer other caps or resistors in the Bada. I use mainly vinyl as my source and a Japanese super deck at that and it is a real pleasure to listen to music through a h/amp now.

I have recently made up some new i/cs using mil. spec. unsheilded, solid core s/plated copper - outstanding. Voices are 3D and in the room, piano is just how piano should sound - I could go on and on.

It seems a lot of Headfiers buy a h/amp and sell on, when what they should do, is a little modding.

My only gripe with the Bada PH12 is the heat issue and that can be solved by yes - modding the chassis and PCB. Other than that, I have no plans anytime soon to sell on this great h/amp.

 

[drarthurwells]

Thanks for your PM to me some time ago ago about power cords. The stock power cord that comes with the Bada is skimpy.

I bought a ZU Birth 1.5 meter powercord new for about $65 on ebay.

I also use a Tice power conditioner.

Makes an audible difference for sure.


BTW, don't forget to protect the mosfets and never change tubes until the residual power in the amp has dissipated - I now wait 12 hours, of the amp being off, before removing a tube.

People who rarely change tubes have no problems with mosfet failure - those who frequently change tubes do have problems, unless they wait a long time before removing a tube.

Anyone having a mosfet failure (losing all volume in one channel) should contact me - I will fix them if you pay shipping both ways and $10 to me for parts (or supply me with a Toshiba K1529 mosfet and two 15V diodes).

 

[kool bubba ice]

I'm getting the BADA12 next week. I kept hearing how great the amp sounds with my SA5000. If it truly is a giant killer I will be very happy.

 

[Black Stuart]

Kool Bubba Ice,
don't forget, ditch the supplied power cord and don't waste good money on buying commercial.
Buy something like 20 AWG stranded, silver plated copper wire and make sure it's mil. spec. this is simply the best wire for DIY and dirt cheap off E-bay.

Use 3 lengths each for pos. & neg. and two for earth. Weave the 3 lengths together - this is dead easy and twist the earth wires. Now use the same weave for all 3 sets of wires - bingo you have a damn fine power cord. To make it look nice sheath the whole thing in something fancy. Before fixing the wires in the plugs use something like De-oxit.

Then when you have done this, let them burn in for a couple of days (they may well get even better). Find someone who likes spending good money for nothing and has bought some expensive power cords and do a head-to-head.

Oh yes and take heed of Art's recs. for tubes - enjoy.

Stuart

 

[Gradofan2]

Quote:

Originally Posted by kool bubba ice /img/forum/go_quote.gif I'm getting the BADA12 next week. I kept hearing how great the amp sounds with my SA5000. If it truly is a giant killer I will be very happy.

OK... OK... OK...

We're anxious to find out how it sounds with your Senns... as well as low impedence phones... and... if the case gets too hot.

And... if you get it from Pacific Valve... how they were as a vendor - especially, if you take advantage of their 30 day satisfaction guarantee.

Let us know when you receive it.

 

[kool bubba ice]

Quote:

Originally Posted by Black Stuart /img/forum/go_quote.gif Kool Bubba Ice, don't forget, ditch the supplied power cord and don't waste good money on buying commercial. Buy something like 20 AWG stranded, silver plated copper wire and make sure it's mil. spec. this is simply the best wire for DIY and dirt cheap off E-bay. Use 3 lengths each for pos. & neg. and two for earth. Weave the 3 lengths together - this is dead easy and twist the earth wires. Now use the same weave for all 3 sets of wires - bingo you have a damn fine power cord. To make it look nice sheath the whole thing in something fancy. Before fixing the wires in the plugs use something like De-oxit. Then when you have done this, let them burn in for a couple of days (they may well get even better). Find someone who likes spending good money for nothing and has bought some expensive power cords and do a head-to-head. Oh yes and take heed of Art's recs. for tubes - enjoy. Stuart

Actually, I bought a Zu new Birth 2 months ago for my old DAC (Modded GM thst I sold)

 

[kool bubba ice]

Quote:

Originally Posted by Gradofan2 /img/forum/go_quote.gif OK... OK... OK... We're anxious to find out how it sounds with your Senns... as well as low impedence phones... and... if the case gets too hot. And... if you get it from Pacific Valve... how they were as a vendor - especially, if you take advantage of their 30 day satisfaction guarantee. Let us know when you receive it.

Different vendor. No problems. Will have it tuesday.

 

[Black Stuart]

Cattylink is an excellant company to deal with and probably the cheapest. Hong Kong Chinese are really good business people and tend to have very good English and Cattylink will probably be the cheapest. Their packing is first class as well.

As an aside I tend to buy caps/resistors/solder etc from a Tawainese co. THL-Audio - totally reliable and again with first class service and amongst the cheapest I know - Victor Chang is the boss.

Kool - so now you have a commercial power cord offering in house - spend a few dollars and see what I am talking about.

I come from a DIY forum where you are considered crazy to buy commercial PCs or i/cs.

Stuart

 

[kool bubba ice]

Quote:

Originally Posted by Black Stuart /img/forum/go_quote.gif Cattylink is an excellant company to deal with and probably the cheapest. Hong Kong Chinese are really good business people and tend to have very good English and Cattylink will probably be the cheapest. Their packing is first class as well. As an aside I tend to buy caps/resistors/solder etc from a Tawainese co. THL-Audio - totally reliable and again with first class service and amongst the cheapest I know - Victor Chang is the boss. Kool - so now you have a commercial power cord offering in house - spend a few dollars and see what I am talking about. I come from a DIY forum where you are considered crazy to buy commercial PCs or i/cs. Stuart

Awesome tube amp. Vety musical & live..Never heard the instruments sound so natural before.. To be fair my Experience with tube amps is scarse.. I only listened to the Cayin 1.. & feel the BADA12 is much smoother.. But I liked the 'tubiness' of the Cayin.. The Cayin seemed to have a deeper sound stage, ofcourse I was wearing the AKG1000 at the time..

 

[gonglee]

Where on the web can I buy Bada ph12?

Thanks in advance...

 

[Gradofan2]

Quote:

Originally Posted by gonglee /img/forum/go_quote.gif Where on the web can I buy Bada ph12? Thanks in advance...

http://www.pacificvalve.us/Headphones.html

And... you can return it within 30 days, if you don't like it.

Local company, someone local to back up the warranty, and... a 30 day return policy - seems like that justifies a few dollars more (very few).

 

[Black Stuart]

Kool,
you don't say if you have ditched the supplied PC. Use an unsheilded one and you will hear the Bada really breathe and come alive.

Also Bada have used a lot of 1uF Solen caps. These caps sit on the sound, unfortunately because Bada have used such a cramped chassis (why), changing out most of these 1uF caps is impossible. This is a shame because Silmics are so much better and I rate them better as coupling caps than BG and only just behind BG in other positions.

Check out Art's photo of the PCB, I think it's on page 3 of this thread. You will see 2 x 1uF Solens' just in front of the first two valve bases. Change these for Mundorf/Audiophiler caps and be amazed at the sound. Also you won't complain of a lack of deep bass. Luckily there are two other caps that can easily be changed 2.2uF - these are easy to identify. Again I have used Audiophilers here but also purchased at the same time some American ERSE caps.It's just that the sound is so good now, that I feel disinclined to try these at the moment.

There is a 15K/2W resistor sitting between the first two valve bases, in my amp it was showing signs of over heating, so I changed it for a Vishay/Dale 3W but it maybe better to use something even meatier like 5W.

The caps and resistor changes can be made without having to remove the PCB, just by cutting the caps and resistor near their bodies leaving the legs and soldering to these.

I now have two source components I have no wish to change (the other a Kenwood TT superdeck). My only gripe with the Bada PH12 is the heat that it produces and has not been dealt with at the design stage. This heat will seriously curtail the life of many of the components. So one day I will have to dismantle it and drill out top & bottom plates and the PCB itself.

This is a truly great h/amp, if it was'nt for the heat issue, I would use the word excellant. Once again a public thank you to Dr Arthur Wells is called for. It was his well written description of this h/amp that made me look further into posibly buying it.