ckng

I am happy with the sound. Nothing like a pair of speakers sounding good with nice sentimental music, your wife sitting beside you...

 

My previous power amp was beginning to hum and at low volumes, not so clear. Now only not very happy yet with the treble. Hoping it will smoothen out when run in.

 

I am just curious. These Class D amps sounds best when low volume, the distortion level is low at low volumes. So, with headphones, it must be very good. Or is it just my wishful thinking? Very tempted to get the amp6 basic and try out.

If the AMP6 series is anything like the AMP3 series (I think should be pretty close), then you cannot simply connect a pair of headphones to the output as the outputs are balanced and do not have a common ground like most amps do. In simple terms, the (-) of the Left and the (-) of the Right are different.

Most headphones have a common ground for the L/R ear and unless you mod the cable so that the Left and Right earpieces are totally isolated you might experience problems connecting it to the AMP3/6.

Regards

CK

Finished some mods to the amp5:

1. Changed the input capacitors to Solen 3.3uF and bypass with a small Vishay-Roedenstein 0.01uF. Both polypropylene.

 

2. Changed the outfilter caps to Rifa/Evox 0.22uF polypropylene.

 

3. Added (just for fun) one Rifa/Evox 1uF polypropylene bypass to each large rail power capacitor.

 

Since I also added silver-coated wires to connect up to the RCAs, I don't know which change benefits the most but the sound is so much cleaner and clearer. However, the extended bass and treble make the amp sound a little like it is in "Loud" mode.

 

At low volume, it really sound good. Anyway, I can't test it loud tonight, it's too late. Btw- with the heatsinks, both the Tripath and regulator are in the mid-40s Celcius and lower.

 

Thanks to CK for suggesting this amp.

Sounds good. What speakers are you driving with the AMP5?

Regards

CK

Bought a used pair from N@Z in this forum (hmm, speaking of which I don't see him around anymore) a couple of years back. Excellent headphones for classical, vocal, jazz type of music. Liquid midrange, very natural sounding.

Regards

CK

Thanks CK. I bought a used 7x4.5cm heat sink from Koba for the Tripath chip. Now trying to figure out how to attach it. For the regulator, I am intending to epoxy a long thin aluminium heatsink to the back of the clip-on and epoxy more little fins to the aluminium strip.

 

Can't use the heatsink you suggest in the pic above for the regulator. There is a little electrolytic capacitor beside the regulator which gets in the way.

Hmm, wouldn't epoxy be inefficient at heat transfer? You can also try those U shaped heatsinks for the regulator, commonly available at places like Koba, etc.

Regards

CK

Been listening to the amp. The mids and bass are quite good but the treble is very brittle and artificial. Alto voices and cello were particularly good, portraying the vibrato very well. And the bass is more extended and fuller than my Meridian monoblocs. I guess the treble is where it will need running in. It is very silent, now that the transformer is not buzzing.

 

What are you guys going to do for heatsink? The transformer, Tripath chip (no heat sink) and the LM317 regulator (with clip-on heatsink) were all at about 60 degrees Celsius. (I have a infra-red thermometer).

 

I am still thinking of some way of making the LM317 heatsink bigger and also find a way to add a heatsink for the Tripath chip.

From the reviews of the AMP1 (which is basically the same thing) @ 41hz.com, it does seem to require a long running in time to sound good. This guy has roughly the same experience as you in terms of sound.

http://www.41hz.com/Forums/topic.asp?TOPIC_ID=218

For heatsinking, maybe you can consider bolting regulator and/or the Tripath to the casing? The Tripath chip should't need something too big. Maybe something smaller than this.

http://img342.imageshack.us/my.php?image=dscf15477xs.jpg

For the regular, maybe something like this.

available from Farnell.

Farnell also has some ridiculously expensive heatsinks

Regards

CK

Update on transformer - reading up on internet on this matter led me to the topic of DC offset in AC power supply. I built a DC blocker but it did not solve the buzz. After I complained to Farnell, they are replacing it. I hope the new transformer will be ok.

 

On another note, I tried the amp and it works with my normal speakers, not sure re: the quality since the transformer buzzes so loudly.

 

Regarding the mute switch on the board, do you guys think it is of any use? The amp already have a delay relay so no speaker thump. So, what can we use the mute function for?

When the phone rings and you are playing some loud music....

Or maybe can think of it as a standby kind of function, i.e. the amp is always "ON" and the components are nice and warm for your listening when you unmute.

Regards

CK

Hi guys, need your help. The transformer I bought started humming. Even when the amp is not connected, just the transformer alone is connected to the mains, there is a hum, like something is loose.

 

Anyone knows what this means? Before today, I did not hear this hum. It appeared when I turned on the transformer to test the relay switch of the amp5. Also could set the DC offset of the amp.

Not sure how to fix a humming transformer, maybe you can post the question to the 41hz forums? Your voltages above looks pretty much ok to me.

Regards

CK

Finished all the miscellaneous parts to connect the transformer to mains and to the pcb, to check the 5V output. Got rubbish setting - started out at 6+ volts and slowly dropped to zero.

 

Turn out my big beautiful lighted switch is faulty. The switch lamp now comes on even in the off position but no AC output discernable to my DMM.

 

Changed the switch to some spares and then I realised the new switch is rated only 4A at 250V. So, I have changed it again to another switch, this one rated 10A 250V. Thank goodness I got spares.

 

So, please do check the ratings of the switch you are buying for the amp5. Like one of my favourite columnist (Jerry Pournelle in BYTE) used to say, "I do stupid things, so that you don't have to do them."

Actually you don't need such a high rating for the switch. For a 200VA transformer at max rating, it will only draw 200/230 = 0.87A @ 230VAC. On the 20-0-20 side, you get 200/40V = 5A max. Your 4A one will probably work well too.

Regards

CK

kross,

The only change I made is the value for R60 - instead of 220ohm, I jumpered it instead. This is the only change necessary due to using the 20V tranformer.

 

I used the general use values for the gain.

I used the General Use values (gain=-1) as well for my AMP3, guess I'll follow suit in AMP5. What I find is that if you are not using a active pre-amp but just a volume pot for volume control, the gain is a little on the low side.

Regards

CK

Hi guys, need some help. I am about ready to check the 5V supply. Any idea where to check it? I know J10 is the + side but where is the negative side?

 

Thanks.

Look for any ground point on the PCB. E.g. the negative side of the big bulk capacitors is a good starting point. Be careful not to short out anything!

Regards

CK

I am surprised that only 1/8W resistors are used in most parts. Surprising because the transformer is huge and the power rating is 100W per channel, this is a really different beast from most amps. Anyway, I know nothing much about Electronics, only what I learned in Physics lessons so many years ago.

Those portions probably run on fairly low current. The huge transformer is more for the output stage to have enough power to drive your speakers at the desired volume

Regards

CK

Did the caps on the back of the board. The BOM missed out C441 which should be 0.1uF, so all 12 pieces of 0.1uF 50V caps will be used up.

 

Also took some time to discover where C44 and C45 are, since the instructions said to omit them first. Turn out they are white lines and circles between C41 and C442, one line is diagonal to the long edge while the other is parallel.

 

Maybe tomorrow got time to do the resistors. Anyone know why most of the resistors are 1/8W type?

I think Jan wanted to keep them as small/short as possible. You know, a bit like SMT components.

Regards

CK

Thanks to CK's advice on using a bench vice. I did the toroids, hope the winding is good enough, anyway got 44 coils around the inductor. Read some advice on the diy forum about not letting the first and last turn touching each other, so I place a short heat-shrink tube on one wire to see if it will do just that.

Looks pretty good! I don't have a bench vice so I had to do the toroids of my AMP3 by hand. Not very fun.

Regards

CK

Thanks CK, I have not started building yet - work very busy. But have checked the components and have read and noted the built instructions up until the power check.

 

I thought I will do the little things like the toroid first with whatever little free time I have.

Same here. Been busy and weekend too tired. Wonder if kross has started...

Regards

CK

Just kidding kross, although I won't mind going back for a makan fest. Great food.

 

CK, can you share your toroid winding technique? Don't want to get into problems winding the little thingy.

 

Thanks.

What I did for the AMP3 toroids is to put in the first turn, pull tight, wind 2nd turn, pull tight, wind 3rd turn etc until the number of turns are completed. You have to make sure all the turns are tight. Otherwise the wire might not be long enough. I *think* if you have a bench clamp it will make things easier as you can clamp the first turn there and wind the rest.

Have you started building?

Regards

CK

Hi guys, ya..i kind of like ck's recommendation. but it is overseas....hmmm

anyway, i am thinking...is it recommended to get such a big casing?? the pcb is quite compact right? only the transformer is quite big. so who has started building? i have yet to order the transformer.

 

heady, the terminals are for banana female plugs??

I have yet to start nor order the transformer. Still deciding between external or internal power supply (i.e. transformer). The casing from Thailand looks damned good. Check out their gallery of DIY stuff using their casings!

http://www.atiresearch-anodized.com/diy%20gallery.html

Regards

CK

I kinda like this one :

They are based in Thailand and also has several other casings.

http://www.atiresearch-anodized.com/products.html

I asked for a quote. Not cheap. The shipping is very expensive.

Hello CK,

 

Thank you for to interested in the ATI Research products,

 

The pricing quite in the US dollars.

 

SHIPPING METHODS :

 

1) Express mail (delivered time : 3-5 days)

 

2) Surface mail (delivered time : a month or longer)

 

PAYMENT METHODS :

 

1) via bank transfer (T/T)

 

2) PayPal

 

PRICING :

 

ATI-661U 1 unit = $56

 

SHIPPING COST (choose for one) :

 

Shipped by Express mail = $46

 

Shipped by Surface mail = $28

 

Thank you!

 

Best regards,

 

Arthon

 

ATI Research Company Limited

 

www.atiresearch-anodized.com

I also asked for some other options. Shipping more than one obviously has some savings, but still on the high side

ATI-661U 3 units = $168 (ATI-661U 1 unit = $56)

 

Service for drilled holes = $24 (each case = $8)

 

Power switch on/off = $3 (each power switch on/off = $1)

 

Power switch button knob = $3 (each knob = $1)

 

Large knob = $18 (each knob = $6)

 

PS: I don't know the diameter for selector hole to drill on the front panel. Is it same as the volume knob or not?.

 

SHIPPING COST (choose for one) :

 

Shipped by Express mail for 3 ATI-661U = $62

 

Shipped by Surface mail for 3 ATI-661U = $38

Anyone knows where to get nice casings like that?

Regards

CK

Ah XS 708's own thread

 

Something to add...

 

It's been known lately that the 6N1, which is the tube at the front in the display, is only used as cosmetic purposes. That is, it does not contribute to the sonic quality of the amp itself.

 

As for my XiangSheng 708B, these are the changes so far :

 

1) Replaced stock power cord with Belden 19364 cord (Initial impressions: Tighter bass, bigger soundstage)

2) Replaced 6N3 with Western Electric 2C51

3) Replaced the 2 6N11 with Electro Harmonix 6922

How much is the WE 2C51?

Regards

CK

Hi cnkg,

 

what can we expect if we were to change the rectifier tube. . .

This I am not too sure. I am a tube newbie.

Regards

CK

' date='12 Sep 2006, 05:26 PM' post='78352']

That's funny lol.. CK, show link please!! I want one!!

 

Hey razer, good luck for your prelims!

Here you go.

http://www.coolest-gadgets.com/20060513/th...ssile-launcher/

Regards

CK

i'm quite a n00b with tubes... i only know that the 6z4 is a rectifier tube and the 6n3 is a gain tube. As to what they are for...

6Z4 (Rectifier) converts the AC from the transformer to DC.

The 6N3 acts as a pre-amp to bring the signal level from the input of the amp (e.g. from a CD player) to a level that can be amplified by the output tubes.

The 6N11/6922/6DJ8 are the output tubes which amplifies the signal from the 6N3 and provides the drive for the headphones.

Simple.

Regards

CK

More like changing the cord to something like Belden.

I don't know how a 708A is like inside (I use a 708B), but you can probably buy the required lenght of the Belden cable, unsolder the stock cable, and solder on the new cable?

Regards

CK

I guess this cute USB Missile Launcher is a no-no too?

Regards

CK

This thread in headfi says about the 6N1 being cosmetical!

 

Anyone able to confirm that?

Sounds interesting. Maybe I should try it on mine. If it's really cosmetic then we can save some money on NOT replacing this.

Regards

CK

oh...ok that is good. so now is the waiting time for the boards then. so how you plan to get the transformers, ckng?

No idea man. Either I can get a 25V toroidal and uncoil some windings to get 22V, or get a 20 or 24V EI transformer. Or run 18V and lose some power. Have not decided which way to go

Regards

CK