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Post by Deleted on Sept 9, 2010 21:31:36 GMT
An input selector with the needed RCA's on the input and 100 Ohm output resistors connected to some output RCA's. A bit 'overkill' to use it for driving a power amp though.  You can almost use it as a power amp.  Wouldn't recommend using it as a power amp with it's 10 Ohms emitter resistors and 2.2 Ohm power line resistors mind you.  These parts might feel the heat ! Frans, thanks for the reply, what would you put there instead. Or, do you lean towards thinking that it's not really appropriate as a pre-amp? |
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Post by PinkFloyd on Sept 9, 2010 22:06:31 GMT
That looks very smart Mike. The internal shots look better than most consumer products you peep into! Thanks  Sounds a lot better too! |
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Post by PinkFloyd on Sept 9, 2010 22:23:33 GMT
By the way Chris.... you'd be looking at "MEGA bucks" if you were to buy the same (fully built) in an audio boutique £500 =  So.....  Would "easily" be 10 times more (purely on a "parts count" basis)  Trust me guys, this "Panda" is the best thing that has cropped up for MANY a year At just over £100 to build (assuming you have tools, have a good understanding of electronic components and know one end of a soldering iron from the other) this is (IMO) the best value headamp on the market bar none. Mike. |
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Post by Deleted on Sept 9, 2010 23:09:21 GMT
You're right Chris. The LED is mounted behind the switch which has a translucent ring around it. Mike, Mick, if your cases are coming from the same guy mine did you could be disappointed. The first fascia I got was badly scratched. he did send another but it wasn't mint, I posted about it at the time. He also now says they may not be perfect, in his advert. They are lovely boxes if all goes OK though. I shouldn't be looking at that new kit, I'm supposed to be clearing down my cupboard  Syd Edit: Just saw Mike's post further back, his box arrived and looks A1, great. |
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Post by PinkFloyd on Sept 9, 2010 23:16:34 GMT
You're right Chris. The LED is mounted behind the switch which has a translucent ring around it. Mike, Mick, if your cases are coming from the same guy mine did you could be disappointed. The first fascia I got was badly scratched. he did send another but it wasn't mint, I posted about it at the time. He also now says they may not be perfect, in his advert. They are lovely boxes if all goes OK though. I shouldn't be looking at that new kit, I'm supposed to be clearing down my cupboard Syd Syd, The enclosure I received didn't have a mark on it... it is 100% A OK.... it will probably have a few marks on it once I've finished messing about with it tho' Mike. |
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Post by Deleted on Sept 10, 2010 7:02:14 GMT
[/quote] Frans, thanks for the reply, what would you put there instead. Or, do you lean towards thinking that it's not really appropriate as a pre-amp? [/quote] A HP amplifier is designed to drive relatively low Ohmic loads that may be resistive but also inductive and even capacitive. This is not needed to drive a power amp. Most poweramps have relatively high-Ohmic and purely resistive inputs and don't need 'power' to drive it. a preamp only needs to deliver a few volts with only a few mA to completely run poweramps to their maximum output. 10V eff with several hundreds of mA's is simply a bit too much if you ask me. There are plenty of preamp kits and schematics available that are up to the job.  You can basically use this amp and it will have enough amplification and will sound good also. It's just 'overkill' |
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Post by Deleted on Sept 10, 2010 8:31:22 GMT
That looks brilliant Mike That`s a bonus, was not expecting all the "furniture" supplied with the enclosure, makes this exceptional value for money IMHO. So how does it sound in comparison to the V-CAN for example? Great work Mike. |
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Post by PinkFloyd on Sept 10, 2010 8:54:21 GMT
That`s a bonus, was not expecting all the "furniture" supplied with the enclosure, makes this exceptional value for money IMHO. Decent furniture for the money and not a "nut" in sight.... all the screw holes are threaded  |
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Post by PinkFloyd on Sept 10, 2010 11:58:09 GMT
I will be having a prolonged listen tonight Mick, once I get the lid on |
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Post by PinkFloyd on Sept 10, 2010 19:14:57 GMT
CRAP! Put her all together, tested the DC offset etc. all was fine.... switched her on, shoved a CD in the tray, hit play and I was almost deafened  Volume control at ZERO and sound comes out of the left channel at FULL volume... friggin' great I got a very quiet track and hit play again.... FULL volume from left channel but pot is working correctly on right channel. Obviously, the first place I am going to look is the pot itself.... it's too late tonight so I'll do it tomorrow. All I can think is that when I was desoldering it out of those god awful through hole plated pads I have, inadvertently, damaged it in some way.... whatever it is, the left channel is coming through at full blast. Great!  Now I'm going to have to strip the blasted thing down again |
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Post by PinkFloyd on Sept 10, 2010 19:30:00 GMT
It surely HAS to be the pot as the signal goes directly into it so the fact that one channel is coming through at FULL BLAST means the pot is faulty (I hope!!)....
Any observations Frans?
Mike.
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Post by PinkFloyd on Sept 10, 2010 19:51:00 GMT
Everything was going so well too..... oh well, these things DO happen and are easily rectified but it's bastard annoying... I was so looking forward to having a good session with the Panda tonight (I still COULD if I want to listen to it at FULL volume but I doubt the ringing in my ears would be permanent ) One thing I CAN say is that the noise floor is UBER low.... inky black silence across the entire range of the pot (unless you hit the play button then it's WHAMMO!, blow your eardrums out of your rectum and clean across the living room noisy! ) it's deadly silent (to the human ear anyways) which is a very good sign. I don't think I have any ALPS pots left so (if the pot does prove to be culprit) I'll have to poach one out of another amp.... All my WNA amps have 50K ALPS pots so, hopefully, I'll be back this time tomorrow with an indication of the SQ capabilities of the Panda. In the meantime..... here's how it looked 20 minutes before my left eardrum was almost blown out through my arse (note to self for future reference - when firing up an amp for the first time A: do NOT have the headphones on your head. B: Choose a track that does not begin with a loud cocophany of drums, electric guitars, organs (and other assorted instruments) with a middle aged man screaming like Tarzan) Got to undo all this tomorrow but it's pretty modular so just a case of desoldering a few bits and pieces:        |
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Post by Deleted on Sept 10, 2010 21:06:30 GMT
It surely HAS to be the pot as the signal goes directly into it so the fact that one channel is coming through at FULL BLAST means the pot is faulty (I hope!!).... Any observations Frans? Mike. Sounds like either the connection in the ALPS (the one connected to the ground pin) is faulty or the ground pad is somehow not connected to the ground plane anymore which is highly unlikely. If you place a wire between the ground pin of the ALPS between the left and right channel and it's still bad then the ALPS needs replacement. These are the 2 pads closest to the cooling fins. In this case the connection point of the carbontrack doesn't make contact with solder pin or the track is broken somewhere near this point. You can verify this by turning the vol pot to minimal setting and measure between the centre connection and the one next to it closest to the middle of the board. It should read (close to) 0 Ohm (no power on the board, the ALPS can be measured in cicuit) I think your initial thought of the faulty ALPS is probably the correct one, |
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Post by leo on Sept 10, 2010 22:10:32 GMT
Bugger, thats a shame ! was going to comment how well it looked too It'll be a PITA but any chance you can desolder the pots pins ? ALP's blue usually held together with screws at the back so you could check the wipers, plates containing the track etc for any damage or shorts Is it possible theres any stray solder, strand of wire etc shorting the pads out underneath the pot on top layer of board ? |
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Post by PinkFloyd on Sept 10, 2010 22:44:39 GMT
Certainly NOT!
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Post by leo on Sept 10, 2010 22:48:36 GMT
Just checking The pot will be too blame, just stick your meter on the in and out pin to see if its shorting no matter the position of the knob |
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Post by leo on Sept 10, 2010 22:50:30 GMT
BTW those cases look real smart, wonder if they do ones with plain panels
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Post by Deleted on Sept 10, 2010 23:07:13 GMT
Just checking The pot will be too blame, just stick your meter on the in and out pin to see if its shorting no matter the position of the knob Normally, in a situation like this,when using a decent quality pot like the Alps, I would suggest a dry joint at the earth pin of the volume control on this channel, or perhaps a missing earth strap. However, that's very unlikely with Mike's work. |
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Post by PinkFloyd on Sept 10, 2010 23:19:58 GMT
I wish I hadn't said anything now Yep, it's a dodgy pot (probably caused by ME yanking it out)......... Take "two" this time tomorrow |
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Post by leo on Sept 10, 2010 23:43:55 GMT
I wish I hadn't said anything now |
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Post by Deleted on Sept 11, 2010 6:56:29 GMT
Mike's soldering job can clearly be seen on the pictures he posted as is the layout of the board.
This led me to the firm belief the pot is at fault because the soldering job was A O.K.
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Post by PinkFloyd on Sept 11, 2010 19:31:10 GMT
She lives!  Checked the pot and it was perfect so could only be one of the ground pads not connected to the ground plane and it WAS! How random was that? Frans, it would have been the LAST thing I would have checked so many thanks for pointing it out You are fantastic and a VERY clever man, I wish I knew half the stuff you do. The fix was simple......  I wasn't happy with the LED sitting on top of the switch so I got my drill out and made a nice little 1mm hole right through the front panel, I then went in about 8mm from the rear of the panel with a larger drill bit so the led would fit snugly inside.... I finished off by using a countersink bit on the front of the hole. This is the way the X-CAN V3 has it's LED mounted..... it looks superb!  I had to remove those cable tie holders off the transformer as the flippin' lid wouldn't go on....  Shoved a 275V EPCOS varistor and a 470nF class X2 cap across the line. I will be adding a class Y2 between L/E and N/E tomorrow...  Grounded the pot body to the chassis....  Bolted down the lid...  Am now having a listen through my HD-250ll Linear's.....  This amp is QUALITY! more on the SQ later |
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Post by PinkFloyd on Sept 11, 2010 19:34:22 GMT
By the way.... the green output resistors (attached to the Neutrik head socket) are 75ohm Kiwame types.
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Post by PinkFloyd on Sept 11, 2010 22:19:07 GMT
A quick report on the SQ.....
She's been up and running for a few hours and, already, is the most musical amp I have EVER heard.... the presentation is "grand".... the bass extension is absolutely the most toenail curling I have encountered. This is, undoubtedly, the best sound I have heard from a headphone amp.... I have pulled a "good" few CD's from the rack and the floor is covered with them.... I can't remember the last time my entire CD collection ended up on the carpet.... this is one SERIOUSLY mind blowing amp.
I'll report back tomorrow once she's had a few hours on her.
Mike.
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Post by PinkFloyd on Sept 11, 2010 22:55:09 GMT
My fault entirely. A through plated hole is a bastard (at the best of times) to desolder. I (obviously) shagged the pad to ground plane when I desoldered the pot. Secret with this type of board is "get it right first time" this is NOT a board that will be happy with "rolling" Fit and forget. |
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Sounds a lot better too!
Now I'm going to have to strip the blasted thing down again 
