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Post by ana on Oct 11, 2012 3:24:35 GMT
Hi Alex, will see how it goes when the amp arrive. Thanks and appreciated.
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Post by dicky on Oct 11, 2012 6:55:38 GMT
The mod is well worth the effort - if only from a battery life POV.
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Post by Deleted on Oct 11, 2012 7:21:24 GMT
The mod is well worth the effort - if only from a battery life POV. You ideally need at least 1,000mAH rechargable batteries though,and will need to get into some kind of regular charging routine if used without a plugpack.
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mrarroyo
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Post by mrarroyo on Oct 11, 2012 9:56:28 GMT
The manufacturer does not recommend using the amp while it is being charged.
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Post by ana on Oct 17, 2012 8:32:42 GMT
The amp just arrived. Without much delay. I had tested it out and the amp was very hot during operation. I had stopped it immediately after about 15 mins of listening. Opened up and done some measurements and had noticed the voltage for the filament was 11.43v. I was shocked! Really need to install the TSR soon.... Also noticed that 2 of the resistors (directly under the tube) were soldered only with one lead on the board. The other leads of each resistor show signed of being cut. Then, in the same positions, similar valued resistors but bigger were soldered on the under side... put them underside is to prevent heat damage by the tube I think... Furthermore, not sure the reason for adding another one smaller resistor on the underside for? See photo below...kind of strange... Looking at the resistor for the filament, it seem to be 1 ohm? Why they only use 1 ohm resistor? For most case at least they use a 10 ohms. Not sure how long the tube will last in such voltage. The tube used was Sylvania 6111. Thanks.
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Post by ana on Oct 29, 2012 1:28:26 GMT
Just an update...had installed the TSR a while ago. The filament voltage is 6.45v now. The voltage is a little higher but I think I just leave it as it is as 6.45v still falls within the tube's spec.
Would like to improve the following if possible. Is there any mod to prevent them for such portable amp? Please advise. Thank you.
1) The initial "pop" sound when the power is switch on. 2) There is a "pop" sound when the battery gone flat.
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mrarroyo
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Post by mrarroyo on Nov 12, 2012 13:30:39 GMT
Hi, I would like to use the LM4562 and AD797 on this amp. However the NE5532 op-amp can take up to 22 volts versus 17v and 15v respectively for the LM4562 and AD797. Does anyone know what voltage is being supplied to the op-amp in this amp? Thanks.
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mrarroyo
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Post by mrarroyo on Nov 12, 2012 14:40:28 GMT
Ok, I took a chance and did a quick and dirty op-amp swap. I used: - Two AD797 in a dual to single board. - AD8620 - LM4562 - Stock NE5532P I found the sound from both the AD797 and LM4562 kind of dead and with less liveness to the sound. The AD8620 was close to the NE5532P with perhaps an slight sound difference so I left it and will listen to it over the next couple of weeks. BTW I tried the "water towers" for a few seconds and liked the sound, unfortunately they would not clear inside the case so I took them out and did not pursue them since it would not be possible to used them as they are. Below is a link to a couple of pics. picasaweb.google.com/109437154048011247077/OPAmpRolling?authuser=0&authkey=Gv1sRgCMCtxPfImvOXfw&feat=directlink
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Post by dicky on Nov 12, 2012 19:06:57 GMT
Hi Miguel, the voltage on the opamp is the battery voltage, so around 12v. So it should be safe to roll those opamps.
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mrarroyo
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Post by mrarroyo on Nov 13, 2012 11:25:23 GMT
It may be my mind playing tricks but the amp does not get as hot with the AD8620 in place of the NE5532P.
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mrarroyo
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Post by mrarroyo on Nov 24, 2012 12:30:39 GMT
Has anyone replaced the scratchy volume pot? If so what part did you use? Thanks.
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Post by dicky on Nov 24, 2012 13:16:18 GMT
Hi, Miguel. I did - I used a 20k log ALPS pot and was worth the effort.
However, I wouldn't do it again on this PCB, the original was an absolute pig to get out and you could very likely damage the PCB in the process.
Perhaps someone could recommend some switch/pot cleaner?
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mrarroyo
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Post by mrarroyo on Nov 25, 2012 6:12:55 GMT
I did not find any holes on the stock pot to use a cleaner/lubricant and thus why I asked. Thanks.
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Post by wilk561 on Jan 4, 2013 20:24:08 GMT
Hello folks. I'm new in this forum, but i've also did some mods with the small Little Bear tube head Phone amp. First of all, i've bought from eBay a little DC/DC step down convertor (http://www.ebay.nl/itm/400362544457?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649#ht_2611wt_1393. This one is much easier to handle because of it's dimensions. 2nd, i missed something. somewhere in this forum, the tube is changed from a 6111WA into a 6BF7. Is this possible without changing something else?? Please give me a reply if you know the reason for this tube rolling. Thx.
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Post by PinkFloyd on Jan 4, 2013 21:38:32 GMT
The manufacturer does not recommend using the amp while it is being charged. This thread would not exist if anybody gave a shit about what the "manufacturer" recommends....... manufacturer? who's he?
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Post by dicky on Jan 5, 2013 8:53:51 GMT
the tube is changed from a 6111WA into a 6BF7 I think these tubes are equivalent.
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Post by jcinfo on Mar 14, 2013 8:15:15 GMT
Hello i buy one little bear B1, i use your data for update battery life and sound, thanks for yours infos.
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Post by jcinfo on Mar 21, 2013 9:50:14 GMT
Finish update
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mrarroyo
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Post by mrarroyo on Mar 21, 2013 9:56:50 GMT
Nice work, enjoy it.
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Post by techboy on Oct 6, 2013 5:11:53 GMT
How does this perform with HD 650? Does it totally melt the Senn veil?
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Post by PinkFloyd on Oct 6, 2013 19:55:39 GMT
How does this perform with HD 650? Does it totally melt the Senn veil? No Such thing as an HD650 "veil"....... you're basically using an inappropriate amp to drive them correctly. Aune Panda S2 would be my recommendation. Mike.
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Post by techboy on Oct 7, 2013 4:16:22 GMT
I am talking of a portable amp.
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Post by Deleted on Oct 7, 2013 4:32:55 GMT
International Standard IEC61938 requires that headphones should be driven by a 120 ohm source,regardless of headphone impedance.This applies to many headphones, including the AKG K701, Audio Technica W1000 etc. You can't drive these types of headphones correctly from a portable amplifier. Mike suggested the Panda as it has supply rails of + and -20V and is capable of driving such headphones from a 120 ohm source impedance. This would be a 120 ohm resistor at the output of the amplifier. Unless this is done they will not be able to be driven to satisfactory levels, and will have a fatiguing and exaggerated HF response. Alex
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mrarroyo
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Post by mrarroyo on Oct 7, 2013 9:48:41 GMT
You may want to read up on the iBasso D6 or PB2, lots of power from a portable amp.
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Post by PinkFloyd on Oct 7, 2013 10:23:36 GMT
You may want to read up on the iBasso D6 or PB2, lots of power from a portable amp. I can certainly recommend the iBasso amps.... that one you sent me is absolutely amazing for it's size so I'd assume the D6 would have plenty of grunt.
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