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Post by Deleted on Oct 30, 2010 6:36:48 GMT
@ Mike,
How's the weather ... in other words have you sticked your probe in places yet where the sun doesn't shine (the rear hole of the Panda ?)
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Post by PinkFloyd on Oct 30, 2010 10:04:17 GMT
@ Mike, How's the weather ... in other words have you sticked your probe in places yet where the sun doesn't shine (the rear hole of the Panda ?) 32C Frans
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Post by Deleted on Oct 30, 2010 13:44:02 GMT
That's very comfy ! in the shade ? Only 12o temperature rise ?
I found when the panda is set to 1.3V (on the 1k5 resistors) the 3.9V zenerdiode (ZD2, ZD4) is not yet in it's operating range. With 1.5V on the 1k5 it is much closer to it's operating point and it's dynamic resistance will drop dramatically (it should be as low as possible). The class A current will increase by around 15% (which is a good thing) but so will the heat (a few degrees). around 30oC is a very 'pleasant' operating temperature for most parts.
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Post by Deleted on Oct 30, 2010 18:45:39 GMT
You could take a holiday in there. Home at last!!!!!!!!
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Post by Deleted on Oct 30, 2010 18:50:11 GMT
The amp I am currently working on looks like you're on vacation on mount Vesuvius ... when it erupts !
Good to hear you are back... will get your spirit up again.
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Post by Deleted on Oct 30, 2010 18:56:55 GMT
Yes Frans,
I do find it hard. I'm not particularly sociable I suppose and I just prefer to be at home.
People were lovely but lack of real understanding due to language I suppose. That's where I admire your command of the language. Not only do you understand what we're saying, but you understand the subtleties in what we actually mean if you see what I mean.
I find a lot of mis-understanding can happen with the subtleties of what you mean rather than what you are saying ......
Sorry, that sounds a bit daft.
ie; I can say something that I mean to be harmless and someone in the studio can react to the point of chucking a synth at me because of a misunderstanding. You have to be careful in some languages how you describe/criticise something if the audience doesn't fully understand the subtleties of the language. (I have a black eye as the result of nutting a synth head-on)
(That actually happened!!!)
Look at what happened with me and an American chap recently who totally took offence to something that I said and I had no idea what was wrong until Mike explained it!! .... and we both speak English!!!
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Post by krisno on Oct 30, 2010 19:22:49 GMT
Amazing build that Panda with the golden volume knob. I just read 50% of the thread. Looking at the build, you wont probably get anything better - just different.
I have brought out the V2 again, with the Siemen(tesla?) tubes driving Senn 600 with 650 cable. I can see that many people would think this is good enough. It is very much OK.
I will talk to the EBAY guy, maybe he can put together a package to complete the panda, but another question is if I can put it together myself.
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Post by Deleted on Oct 30, 2010 19:39:16 GMT
I'm absolutely chuffed to bits with it Kris. It's the business and makes my K701's sound so full. It has changed my feelings about the headphone entirely and now realise just how much it seems to react to different amps.
The Panda has a gorgeous, lush and detailed sound with a feeling of real power behind it and now I'm getting nervous because it still has another 600 or more miles to go before it gets back here. Now it has more driving power, it'll make mince meat of the K701's!!
Not only does it sound fantastic, but it's a beautiful piece of furniture in the room and hand built into the bargain!!
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Post by krisno on Oct 30, 2010 19:48:15 GMT
Yes... the K701 really has potential. if you have right equipment i mean.
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Post by Deleted on Oct 30, 2010 19:49:32 GMT
Amazing build that Panda with the golden volume knob. I just read 50% of the thread. Looking at the build, you wont probably get anything better - just different. I have brought out the V2 again, with the Siemen(tesla?) tubes driving Senn 600 with 650 cable. I can see that many people would think this is good enough. It is very much OK. I will talk to the EBAY guy, maybe he can put together a package to complete the panda, but another question is if I can put it together myself. Mine is running fine now, and i have nearly completed a second one, apparently there was nothing wrong with the first one until i started poking around with my meter probes causing a short circuit,(its my big hands which are not made for such delicate work) which caused one of the B649 thingees and a resistor to fail. As my test cd player was giving a DC voltage at the source of my Amp, it was causing the Panda to cut out when volume was increased. frans has shown me how to rectify the problem, at the moment have it hooked up to my iPod with no such problems, and is sounding great, if i can successfully build one of these, anybody can, even the enclosure mods and alterations have been done in my home workshop using hand tools, without the need of my machine shop facilities. Mick.
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Post by Deleted on Oct 30, 2010 20:06:13 GMT
Hopefully, you like the sounds you're getting from it Mick? You kept that quiet!
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Post by krisno on Oct 30, 2010 20:24:08 GMT
I presume this may sound alot like the Burson HD160 which I had one time. Discrete operations etc. The Burson had an AMAZINGLY wide soundstage on the AKG K 701. The Panda me too? for 40 quid... haha. incredible.
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Post by PinkFloyd on Oct 30, 2010 20:30:34 GMT
Are you in a hurry to get it back Ian? I'd like to try the 1.5V thing that Frans suggested so will another couple of days be fine?
Frans, it's pretty much "essential" with this amp that you adjust the DC offset with the amp at it's normal operating temperature and that means leaving the lid on for a good hour with your room at normal temperature... I then "quickly remove the lid, attach two meters (croc clips) and quickly trim until both are reading 0.00mV.
It can fluctuate as much as +/- 30mV from cold to warm so this really is one of these amps that has to be warmed up a bit for everything to stabilise. Personally, I leave mine switched on all the time (day and night) and there is almost zero fluctuation with the offset.
Of course, if we want to go the full belt and braces approach then we could also stitch a 1000uF non polar (per channel) on the output.... this would ensure that it is always zero DC but may affect the sonic signature somewhat.
May be worth a try?
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Post by Deleted on Oct 30, 2010 20:40:00 GMT
Are you in a hurry to get it back Ian? I'd like to try the 1.5V thing that Frans suggested so will another couple of days be fine? Frans, it's pretty much "essential" with this amp that you adjust the DC offset with the amp at it's normal operating temperature and that means leaving the lid on for a good hour with your room at normal temperature... I then "quickly remove the lid, attach two meters (croc clips) and quickly trim until both are reading 0.00mV. It can fluctuate as much as +/- 30mV from cold to warm so this really is one of these amps that has to be warmed up a bit for everything to stabilise. Personally, I leave mine switched on all the time (day and night) and there is almost zero fluctuation with the offset. Of course, if we want to go the full belt and braces approach then we could also stitch a 1000uF non polar (per channel) on the output.... this would ensure that it is always zero DC but may affect the sonic signature somewhat. May be worth a try? Have mine running at 1.5 v sounds great, and yes dc offset alters dramatically when Amp is cold, and requires a good hour before settling down to around zero. Mick.
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Post by Deleted on Oct 30, 2010 20:42:40 GMT
No Mike. That's fine!! Good grief, it don't get much better!!! No rush. Don't put pressure on yourself Mike. I'm slumming it down here what with a V1 V2 V8 and V Can!!! (Not forgetting the gorgeous little buffer. (Gorgeous little fcker? )
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Post by Deleted on Oct 30, 2010 21:28:05 GMT
Hopefully, you like the sounds you're getting from it Mick? You kept that quiet! Yes Ian sounding very nice, need to listen to it for a while yet to see how it rates against my other Amps, one thing is for sure, it is certainly good value for money, if building it yourself for pleasure when the labour cost is not taken into consideration. Mick.
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Post by Deleted on Oct 30, 2010 22:25:42 GMT
Are you in a hurry to get it back Ian? I'd like to try the 1.5V thing that Frans suggested so will another couple of days be fine? Frans, it's pretty much "essential" with this amp that you adjust the DC offset with the amp at it's normal operating temperature and that means leaving the lid on for a good hour with your room at normal temperature... I then "quickly remove the lid, attach two meters (croc clips) and quickly trim until both are reading 0.00mV. It can fluctuate as much as +/- 30mV from cold to warm so this really is one of these amps that has to be warmed up a bit for everything to stabilise. Personally, I leave mine switched on all the time (day and night) and there is almost zero fluctuation with the offset. Of course, if we want to go the full belt and braces approach then we could also stitch a 1000uF non polar (per channel) on the output.... this would ensure that it is always zero DC but may affect the sonic signature somewhat. May be worth a try? I found Mick's Panda to vary about 40 mV before it is settled on one channel and 23mV on the other channel. Once he get's it back he will have to re-adjust (probably) too once it's boxed. Though not ideal I wouldn't call it alarming yet as it only get's better the longer it is used (left on). Like you said, once the temperature has stabilised the DC output voltage will be stable around 0mV (once adjusted at the operating temperature to 0mV) Instead of a 1,000 uF non polar I would consider the DC servo route myself. Both will have the same effect but personally don't like non polar electrolites in the signal path. DC servo will be easy to implement but raise the noisefloor slightly too perhaps. If you design the servo so it will have a 10 second reaction time there won't be difference in low freq performance (cutof point 0.02 Hz @ - 3dB regardless of the load's impedance) where 1,000 uF still will have a 1.6Hz (- 3dB) cutoff point (with 68 Ohm output resistor and 32 Ohm cans, anything higher impedant will lower this cutoff point. Not that you can hear much below 30Hz anyway but one can never be sure.. One 'disadvantage' (every upside has its downside) of the Panda is the fact that this amp is DC coupled all the way from the input to the output. If the source has DC on its output it will be amplified 5x too (if standard amplification and vol pot at maximum setting). It is very possible that on the output of the Panda a DC voltage might be present and, if below 0.6V, will remain 'undetected' by the DCoutput detector (U1, uPC1237) which headphones will not particularly like for longer periods and will cause them to sound not as good as they could/should. Input coupling caps will help in this case and can be better quality (Polyprop instead of electrolites) because of their low value. This ofcoarse doesn't adress the DC voltage drift where input FET (K246 Q6,Q8 and Q15,Q16) matching may help, but as you know is a tidious task. About 20mV DC is not really alarming but unwanted as the diafragm of the drivers are not in their exact mid position anymore... they won't go up in smoke or get damaged by these low voltages.
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Post by PinkFloyd on Oct 30, 2010 23:03:14 GMT
I still reckon 1000uF NP is the way to go A "good" NP cap like a MUSE shouldn't rock the boat too much
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Post by Deleted on Oct 31, 2010 7:51:27 GMT
It is much easier to do in any case. The amp doesn't really need an output cap when it has some time to warm up before you plug in the HP's. everything below +/- 10mV is not bad. Arguably a DC servo will be sonically better as it is not in the audiopath where a NP electrolite is.
You can make your own nonpolar with 2*2,200uF in anti series (connect the - of the 2 caps together and use both +'s of the caps as the cap itself. You may call it 'the poor mans non polar' but won't be better quality then a single NP.
I see there is a PCB available for the SC class A amp thread reply 180 that can be used directly...
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Post by Deleted on Oct 31, 2010 11:47:07 GMT
Hopefully, you like the sounds you're getting from it Mick? You kept that quiet! Yes Ian sounding very nice, need to listen to it for a while yet to see how it rates against my other Amps, one thing is for sure, it is certainly good value for money, if building it yourself for pleasure when the labour cost is not taken into consideration. Mick. You have me curious now Mick. How long do you reckon it takes to put it together. I'm considering doing it myself maybe but it's been so long that I haven't the confidence any longer. I built synths from kits way back but I was too stupid to know how difficult and dangerous it could be. Now I'm over cautious. No confidence. I love the amp's sound so much that I'd put them in different rooms in the house!! For me, it totally changed and absolutely made my mind up about the K701. It's such a different headphone on the Panda and offers a much more serious (and in control) bass with a warmer sound than I was getting before. I'm kind of moving away from the Senn sound and now realise that it's the warmth and bass that I was missing from the AKG that kept me as a solid Senn man. (Shows what a tart I am! )
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Post by Deleted on Oct 31, 2010 14:45:00 GMT
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Post by Deleted on Oct 31, 2010 14:54:10 GMT
What a lovely job. It looks REALLY good. Same box as mine.
What worries me apart from electrocuting myself (which I did once rather severely) is that first switch on; when you hope everything's right and then when nothing happens, the tracing can be a nightmare.
I'm glad you've got it sorted because I had thought you'd got into difficulties at one point and it's such a disappointment after all that hard work if it goes pear shaped.
What is really good is just how neat that lot looks in the box. Really good!!
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Post by toad on Oct 31, 2010 15:37:59 GMT
Blimey that's a nice looking build Mick. It looks like you've been building Amps for years. I wish I had soldering skills but I'm limited to attaching 13 Amp plugs. Once again, many thanks for building me a panda. If it has the synergy with the 701s that Ian says and why shouldn't it, I'm going to be like a pig in sh1t Ian
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Post by Deleted on Oct 31, 2010 15:47:15 GMT
Yes that happened on both of mine Ian, as unknown to me my test cd player was given out a dc voltage at the input stage of my Panda, and it doesn`t like it, but with Frans help, just a telephone conversation for the 2nd PCB, and its sorted. Unfortunately i blew a 649 thingemejig and a resistor, poking around with my meter on my first, so Frans has very kindly mended that for me, and tweaked it a little, so should finish Ian`s soon, just waiting on some parts i ordered from Mike, (toroid, wire and switch etc.). On my first attempt i suppose i spent about 20hrs in total, populating PCB, modifying enclosure, and fitting all the parts into it. The second one has taken far less time, as i kinda know what i am doing. PS. yes i got 3 good belts of mine while messing around with it, so decided it was time to insulate the terminals on the input socket connectors, quiet enjoyed the first 2 but the third made me feel a little strange Ian. ;D
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Post by Will on Oct 31, 2010 15:54:59 GMT
Mick, that's a lovely clean build you've done, nice attention to detail Talking of first switch, there was a thread once of a similar vane. I'm definitely a 'remote' first switch on type (plug the amp/psu/whatever into an extension cable, switch the kit on locally, and then switch the mains on the extension, from the other side of the room! ) I've built loads now, but still get that 'flinchy' feeling on first switch, although I've never died from it yet.
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