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Post by dejanm on Jan 28, 2009 9:40:39 GMT
I also had the problem with harshness after executing very similar mod of my X-Can V2. The problem dissappeared when I changed the supply transformer. Putting larger caps in PSU (and also exchanging the ZTX's) will put additional pressure on supply transformer, which might saturate generating distorsion, which you can hear as very sharp high tones. When I put stronger trannie capable of delivering 1A at 12V AC, then this harshness dissappeared.
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Post by Deleted on Jan 28, 2009 9:51:20 GMT
Dejan
Krisno had this problem before the mods were done, so the stock PSU should have been O.K.
Just out of curiosity, does anyone have a schematic of one of these, and it's PSU ?
SandyK
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Post by PinkFloyd on Jan 28, 2009 11:18:35 GMT
Kris, the amp should not sound harsh. It will certainly "blossom" after a couple of hundred hours usage but should be pretty nice from the off...... Have you mentioned your source?
Remember the amp will only amplify what you are feeding it. If the source is pretty harsh then expect that to be AMPLIFIED..... I've read a few of your posts and you keep having these problems with the "amps" I think it's time to start looking at your front end my friend.
Mike.
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Post by dejanm on Jan 28, 2009 11:25:45 GMT
Dejan Krisno had this problem before the mods were done, so the stock PSU should have been O.K. Just out of curiosity, does anyone have a schematic of one of these, and it's PSU ? SandyK I understood after the changes ... but never mind ... If you are looking for the schematic of X-Can V2 you can find it here: www.rock-grotto.co.uk/v2schematic.htmIt is placed by Mike and it is correct. The only difference that I've seen comparing my unit with this schematic was the resistor R108 which is in my case 220K and not 100R as claimed here ... PSU schematic I do not have but it is rather simple one ... you will understand it in moment when you see it ...  |
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Post by Deleted on Jan 28, 2009 11:32:20 GMT
Dejan
I have a copy of that one ,(no PSU schematic) but I have a few doubts about it's accuracy. For example, I find it difficult to believe that R102, the input terminating resistor is only 2K2.
That's quite a load on the preceding stage, especially if valve based.
C107 and R108 in the feedback doesn't feel right either. (3.3picofarad across only 100R ?)
Alex
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Post by dejanm on Jan 28, 2009 12:06:12 GMT
I am planning to switch the tubes to see how it works with another brand - I am using at the moment Reflektor 6N23P-EV. When I do that I will check R102. I checked a lot of resistors because I exchanged them but not that one - so I cann't tell you immediately .... Give me a week or so ...
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Post by PinkFloyd on Jan 28, 2009 12:12:13 GMT
I've got one sitting next to me "stripped" so will measure R102 later when I get back from the post office.
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Post by dejanm on Jan 28, 2009 12:43:10 GMT
I've got one sitting next to me "stripped" so will measure R102 later when I get back from the post office. Great Mike. I was not thinking about it before (I must admit) but this SandyK remark about R102 does make sense ... |
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Post by krisno on Jan 28, 2009 13:09:45 GMT
Guys.... let me rephrase myself.
The thing is 'harsh' and fatiguing, specially on higher volume.... this was not the case on the yulong. On lower end it is not that bad, still might seem a bit sharp.
The V2 when doing some google seems to be complained as a bit bright. WILL CHANGING ANY OF THE TRANSISTORS MAKE ANY DIFFERENCE??
Mike.... my DAC is a NOS dac, it was not sharp at all when using the Yulong DAC. So why is it sharp now? NOS dac's I have ever heard are complained about as sharp either.
I think more power might help. Since the V2 and V3 isnt it almost the same amp?? I never tried V3 with stock PSU, V8 either. I saw in a review that amp becoming harsher on high volume = lack of power.
The amp is hardly used, but still under the transistor there are some heat/burn marks. What if I replace the v2 transistors with the once that are in the V3?? Will that mellow it out?
Other than the sharpness, this thing is great. Very dynamic, fast, fun... but still solid state = more details, and solid state is 100% non-fatiguing, atleast the yulong.
I will get the Shanling PH100 discrete amp, it is a bit dark I think and perfect for AKG. That will be the last amp i ever get, but I don't think I will sell this.... will be intereseting to see how the PSU works on this.
BUT GUYS, any way to 'mod' or adjust the GAIN on the V2?? It really is on high volume, volume turned 15-20% and its almost allready too high. This can't be normal? The V3 was not like that.......
Thanks guys for following me through.....
It was as big setback for me, even though it sounds great.... thuogh i think the mids on the jan philips are better than the russian. Maybe I should get the Sennheiser HD800 and 'call it a day'... that these AKG's just are too difficult to get properly running. But on solid state the AKG's fly.!!
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Post by krisno on Jan 28, 2009 13:30:39 GMT
We might have 2 things here going on...
1: When I got the amp and listened to it, it was harsh and bright because the tubes where destroyed? Atleast one tube was very microphonic and looked bad
2: After mod and tube swap it is a bit harsh because of lack of power....
So problems solved with the x-psu... time will tell.
But I have to be honest, when using the NOS dac + Yulong, I really heard the 'colors' of the music, and the atmosphere. It is probably the best I have ever heard, but still sounding a bit 'flat'.
This V2, seems again to remove the atmosphere and 'colors' even though using the same NOS dac.
It is brigther than the yulong, no doubt.......
But other than that, best tube amp I've ever heard... not laid back at all. Not boring. ...
** BTW, I just put the led into the hole and a bit of tape on the back to hold it there. How you guys fasten the new LED in the xcan?
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Post by dejanm on Jan 28, 2009 14:40:05 GMT
You can glue the LED in the hole of the front cover ...
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Post by dejanm on Jan 28, 2009 14:41:10 GMT
By the way, I didn't quite understood: do you have external PSU for these Cans or not ?
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Post by krisno on Jan 28, 2009 15:07:38 GMT
No, not external psu this time. waiting for mikes product. probably be here next week (the third pinkie i order last 12months hehe)..... I have tried both the v3 and the v8 before this modded v2 you see. If I am lucky, the PSU will solve my problems.... then it will be as good as tube can ever get.
I have to try that Shaling ph100 discrete... I watch some movie trailers and this nos dac with solidstate + akg k701 = extreme 'drive' and details and positioning in good movies. But again, this V2, best tube I have ever heard, atleast if psu fix the harshness.
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Post by dejanm on Jan 28, 2009 15:30:51 GMT
No, not external psu this time. waiting for mikes product. probably be here next week (the third pinkie i order last 12months hehe)..... I have tried both the v3 and the v8 before this modded v2 you see. If I am lucky, the PSU will solve my problems.... then it will be as good as tube can ever get. I have to try that Shaling ph100 discrete... I watch some movie trailers and this nos dac with solidstate + akg k701 = extreme 'drive' and details and positioning in good movies. But again, this V2, best tube I have ever heard, atleast if psu fix the harshness. Concerning harshness ... it worked out in my case. And my external PSU is a bit weaker than Mike's Little Pinky. It would be interesting to know how it will work in your case. Please let us know ... |
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Post by krisno on Jan 28, 2009 16:21:54 GMT
Of course I will let you know.... Those russian tubes are very dynamic btw... quite a bit more bass than stock jan phillips. Nice to know they are brand new! No microphony at all.. great. I would be quite happy with this , if sharpness get fixed. It is a fun amp, you guys are right. But in the end, I will probably end with a discrete amp, like the Stello or Shanling... but tubes has some magic with it.  |
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Post by Deleted on Jan 28, 2009 22:47:52 GMT
Mike
Are you able to confirm the value of the input resistor R102 as 2K2 ? I would have expected something more like 22K (or higher)
Also are you able to verify the actual values of C107 and R108 ? 3.3picofarads and 100ohms ? If C107 is actually 3.3pf, I would expect a few Zeroes after the 100 of R108.
The trouble is that some people may go fitting "boutique" components as replacements, based on the values given in the schematic.
Alex
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Post by dejanm on Jan 29, 2009 8:45:12 GMT
Mike Are you able to confirm the value of the input resistor R102 as 2K2 ? I would have expected something more like 22K (or higher) Also are you able to verify the actual values of C107 and R108 ? 3.3picofarads and 100ohms ? If C107 is actually 3.3pf, I would expect a few Zeroes after the 100 of R108. The trouble is that some people may go fitting "boutique" components as replacements, based on the values given in the schematic. Alex SandyK, I already mentioned that: R108 is 220K and not 100 Ohm. I replaced it with better resistor ... |
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Post by dejanm on Jan 29, 2009 8:52:27 GMT
Has anyone tried the JJ Tesla E88CC tubes? I read that they are very mello and warm. If so they could be use by krisno to remove some of the edge he hears. The JJ Tesla E88CC sells in the US for $9.95 each which is a very good price, if you do not like it you cant trash them and you would only be out $25 or so w/ S&H. I listened to Tesla and they are ... so - so ... Not tragic but not exceptional as well. I didn't try them in X-Cans though ... The goal is I believe not to get mellow but accurate sound. And that means to find tubes that are as linear as possible for these working conditions. According to Borbely, 6N23P are more linear and have less THD than Tesla e88cc. I believe that first the issue with PSU should be fixed. Then 6N23P-EV should be listened carefully and then the decision could be made to go for another tubes or not. My (unqualified) opinion is that 6N23P are better than most e88cc in this price range. If you want better sound then something like Mullard, Siemens or Telefunken should be taken into consideration. Unfortunately, they are in completely different price range ... |
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Post by Deleted on Jan 29, 2009 9:00:03 GMT
Dejan Sometimes resistor values change with different revisions of a model, but the fact that I was able to so easily pick 2 errors in the schematic, does not bode well for the accuracy of the rest of that "reverse engineered" schematic,even though it has been around for several years. I hope that you measured , or at least had a very close look at the colour codes of the removed resistors before replacing them ? Alex P.S. Why is C102 a 10uF 25V electrolytic ? For that matter what is its's purpose , other than than preventing minor amounts of DC from the previous equipment from causing a rustling noise as the volume control is advanced? The majority of sources will (should) have buggerall D.C. out. C102 should normally not be necessary, and it's inclusion will cause a small audible degradation. In all fairness, Mike has already pointed out that it is better off without it. Has anybody measured the difference in voltage between the anodes of the twin triodes ? (no signal) It is possible that this differential stage could be further enhanced by fitting a Zener diode(S) equal to the difference in potential between the 2 anodes, between the tied base and collector junction of Q102 and the anode of V1b. To reduce sensitivity a little, perhaps R107 (27K) could be increased to 47K. P.S. A closer look at the schematic reveals that the transistors in the current mirror supplying both anodes, have only about 600mV (!!) between their collectors and emitters.  |
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Post by dejanm on Jan 29, 2009 12:59:18 GMT
Dejan Sometimes resistor values change with different revisions of a model, but the fact that I was able to so easily pick 2 errors in the schematic, does not bode well for the accuracy of the rest of that "reverse engineered" schematic,even though it has been around for several years. I hope that you measured , or at least had a very close look at the colour codes of the removed resistors before replacing them ? Alex Alex, I did that because I was ordering these "boutique" resistirs, how you are calling them, and therefore I didn't want to make any mistake. So I measured them first and also checked their colours ... and I think I didn't make any mistakes there ... |
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Post by dejanm on Jan 29, 2009 13:02:52 GMT
P.S. Why is C102 a 10uF 25V electrolytic ? For that matter what is its's purpose , other than than preventing minor amounts of DC from the previous equipment from causing a rustling noise as the volume control is advanced? The majority of sources will (should) have buggerall D.C. out. C102 should normally not be necessary, and it's inclusion will cause a small audible degradation. In all fairness, Mike has already pointed out that it is better off without it. I believe that Mike provided a good answer to this question in one of his comments to this design. My assemption is that these caps are there for security reasons - in case if you have something connected to this small amp that does not filter DC. This is one of the points where big HiFi vendors rather sacrifise a bit of sound reproduction quality in order to play safe ... |
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Post by dejanm on Jan 29, 2009 13:05:14 GMT
Has anybody measured the difference in voltage between the anodes of the twin triodes ? (no signal) I did - no difference ... (If I remeber correctly) ... |
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Post by dejanm on Jan 29, 2009 14:59:48 GMT
Just a thought ...
It would be maybe interesting to develop a PCB of the same size as PS PCB of X-Can V2 with that big hole in the middle for a tube. That new PS PCB should do practically the same thing as original one but the regulator might be a better one. That would mean instead of putting so much caps, to try to regulate voltages with descrete elements ...
Then we could simply exchange the PCB in our X-Cans V2 instead of exchanging all these parts ... and maybe get a better sound as well ...
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Post by krisno on Jan 29, 2009 16:03:06 GMT
Before:  After:  Looks somewhat different doesn't it? ;D .... but I will sell also this beauty if it does not behave. The dark Shanling discrete and very powerfull pure SS amp probably is what this AKG needs! But will try PSU first. I might keep it though, as I have spend so much time on this. K |
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Post by PinkFloyd on Jan 29, 2009 21:37:51 GMT
Before: After: Looks somewhat different doesn't it? ;D .... but I will sell also this beauty if it does not behave. The dark Shanling discrete and very powerfull pure SS amp probably is what this AKG needs! But will try PSU first. I might keep it though, as I have spend so much time on this. K Looking good Kris  Your PSU shipped yesterday, I think you will notice a bit of improvement Having said that, if your source is pretty sharp then it'll probably sound even sharper with the PSU.... is it still coming across as sharp or is it starting to mellow out a bit now? As the other posters have pointed out..... remove those 10uF caps and jumper over the pads, they are not necessary and you will find the amp sounds a bit more open without them in circuit. |
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Your PSU shipped yesterday, I think you will notice a bit of improvement