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Post by ngquan on Jul 3, 2008 12:15:37 GMT
Hi guys, just wonder any one else out there owned or played around with the AT-F100. I could not find much info on the web. I am having problem with the volume control - it is way too loud even at lowest level- Just wonder is there any way to trim off so that the volume control can be more useful.
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Deleted
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Post by Deleted on Jul 3, 2008 17:30:13 GMT
PM "DC " as owner of one of these.
You didn't say if it is a problem from new, a development or a result after tinkering?
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Post by ngquan on Jul 4, 2008 9:37:12 GMT
Hi, the vol is already loud brand new from the box and i have not tinkered at all with it.
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Deleted
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Post by Deleted on Jul 4, 2008 9:55:08 GMT
ngquan As it is faulty on receipt, why not just request a replacement and send it back? BTW, a quick search found the comment that G&W is not renowned for it's quality control. Also that it is a jfet/Mosfet design, with supposedly a poorly implemented DC offset design. That may only be one person's opinion,though.
SandyK
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Post by ngquan on Jul 4, 2008 21:53:33 GMT
Hi Alex, the problem is that it was my first buy of a HA from ebay so there is no way back- I see similar comment on head-fi forum where the volume is way too loud even at modest turn. May be an-inline attenuator can be a solution?Roth-well? Unless the schema is available for you guys to dissect and comment on.
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Deleted
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Post by Deleted on Jul 4, 2008 22:16:03 GMT
ngquan
Unfortunately,I couldn't locate much more information about it than I posted, other than the usual subjective stuff. A schematic would make rectification a lot easier . Try posting a few clear internal photos, and perhaps someone like Leo may be able to gather further information about the circuitry.
Alex
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Post by ngquan on Jul 5, 2008 5:24:08 GMT
Hi ,how do i get the pictures onto these pages.
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Deleted
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Post by Deleted on Jul 5, 2008 6:03:52 GMT
ngquan There is an explanation on how to, originally posted by Mike in an answer to DC, at the link below. See reply 74. Alex rockgrotto.proboards39.com/index.cgi?board=149&action=display&thread=2234&page=5There are quite a few places where you can upload photos to, such as Photo bucket and Image Shack. With Image Shack, you register with them for a free account. They then send you an email with setup information. Then you can upload your photos to www.imageshack.us. After that, ImageShack will give you a link to your photos, just copy and paste that link to the forum you want to post your photos.
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Post by ngquan on Jul 5, 2008 8:10:13 GMT
here we go-http://profile.imageshack.us/user/ngquan/ Ngquan I saved this photo to my PC, then uploaded it to ImageShack. I then copied and pasted the Forum Code here into your post.. Alex
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Deleted
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Post by Deleted on Jul 5, 2008 8:31:51 GMT
ngquan When you login to ImageShack, click on a photo that you have already uploaded, and you want to post.It should get a red border around it. Double click on it , and it should enlarge. You should see a dialogue like attached.
ACTION 0 images selected [X] Create slideshow Post to blog Edit images Mark as private Mark as public Delete Get code for Forums Get code for Websites Get code for Email Add tags Remove tags Upload Image Upload Multiple Images
My Profile Logout Classic View
Select "Get code for forums" Highlight the whole Forum code , then Copy (Control "C")Then PASTE (Control "V" ) into your still opened Rock Grotto post. You may need to "Modify" your post to do this. You will need to post less blurry photos.Show the whole lot in one photo. Then try zooming in on the main amplification area ,and saving that. Then zoom in on to the power supply section and save it as well. Post all photos.
Alex
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Post by ngquan on Jul 5, 2008 8:57:41 GMT
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Post by Deleted on Jul 5, 2008 9:29:18 GMT
ngquan Sorry, but I am still unable to help. Perhaps someone else will have more luck. Did you have a good read of the User manual that should have come with it ? Alex
P.S. Did you send DC a Private Message (PM) to see if he can assist ? DC is also in Sydney.
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leo
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Post by leo on Jul 5, 2008 19:52:01 GMT
We are going to need a schematic, afraid I can't work that out from the pic, I'd have to see both the top and bottom pcb track clearly to work it out It looks a little crowded in there
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Post by ngquan on Jul 5, 2008 21:38:36 GMT
Hi Leo, i think the schematic is out of the question. Would a pic of underside PCB help?
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Post by minivan on Jul 7, 2008 11:28:37 GMT
i used to have an amp the cutting of the hole of the case is not too precise, and the volume knob can't turn all the way down because of this. check if this is the case, if it is, u will have to use an allen key or screw driver to loosen the volume knob, pull it on a bit.
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Post by minivan on Jul 7, 2008 12:03:37 GMT
this is the schematic of the f100
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Post by ngquan on Jul 7, 2008 21:17:07 GMT
The vol knob certainly moves smoothly. Thanks minivan I contacted the manu no schema available Any comments on schema guys-
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Post by Deleted on Jul 7, 2008 21:49:49 GMT
ngquan Do you have a digital meter, or multimeter ? If so, and assuming that the schematic that Minivan posted is correct, check for continuity between the shield terminations on the PCB coming from the Alps potentiometer, and another PCB "earth" point. (0 Volts line) e.g. The "earth" side (sleeve/barrel) of the Headphone output jack. Stereo Headphone jacks have 3 terminals, commonly referred to, as TIP,RING, and SLEEVE. The active lead from the L Channel goes to the TIP, the active lead from the R Channel goes to the RING, and the earth/0 volts connections go to the SLEEVE. SandyK
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Post by Deleted on Jul 7, 2008 22:29:25 GMT
Miguel Please see attached Regards Alex
Re: G&W AT-F100 « Reply #4 on Jul 4, 2008, 10:53pm »
-------------------------------------------------------------------------------- Hi Alex, the problem is that it was my first buy of a HA from ebay so there is no way back- I see similar comment on head-fi forum where the volume is way too loud even at modest turn.
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Post by ngquan on Jul 8, 2008 10:24:00 GMT
Hi Alex, i have checked the continuity is ok. Also the other problem is hum-not vaires with volumes changes. I noted that on the Jaycar kit -they stressed thew importance of earthing the body of the pot. In the F100- the alps is the blue velvet type but no earthing is seen from body, is this the reason causing the hum?Quan.
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Deleted
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Post by Deleted on Jul 8, 2008 12:12:47 GMT
ngquan
They may be relying on the mounting of the potentiometer to a metal panel to provide earthing of it's body. Sometimes where there is anodising, there is not good contact.This can often be rectified by scraping the metal clean inside the mounting hole area. You could always fit earthing as per this kit. If the shield tags of the Alps potentiometer are in fact connected correctly to chassis/ 0Volts, I am at a loss to explain why the volume control does not function. The hum may also have something to do with the incorrect functioning of the volume control. I still suspect a problem in the area mentioned. Alex
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Post by ngquan on Jul 8, 2008 12:18:25 GMT
HI Alex, the volume control knob is functional. The problem is that the gain may be too high as even a minimal turn of the volume knob for 10degree is way too loud. I hope this make sense.
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Deleted
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Post by Deleted on Jul 8, 2008 12:54:58 GMT
ngquan O.K. That makes a lot more sense. The gain is determined by the ratio of the 2 resistors shown at the gate of the RHS input FET,on the schematc posted earlier. The gain could be reduced by decreasing the value of the resistor that connects from this gate to the output of the amplifier. You would need to trace the circuit physically, or provide a much higher resolution photo of that area ,thyat hopefully someone with sharper eyes than mine could work out it's location from. Alex.
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Post by Deleted on Jul 9, 2008 2:09:08 GMT
Miguel It may help, but a minimum of 12dB would be needed, and that is likely to degrade performance. Alex
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Post by ngquan on Jul 9, 2008 10:39:54 GMT
i try my best for a pic
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