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Post by jmpsmash on Oct 19, 2017 23:36:45 GMT
Recently splurged a little bit and upgraded my setup. I got a really sensitive pair of IEM (Andromeda) and while it sounds great, it magnifies the hiss coming out of my V2 to the point that anything aside from loud music are unlistenable.
I really like the sound of the V2 so I need to de-hiss his thing. Where is the hiss coming from? What can I do to minimize the hissing?
I have tried different tubes, in fact, 4 different sets of 6922 (Russian Shield, Amperex, Sovtek, original Philips). All give similar amount of hiss.
The PS caps has been changed out already recently, so those should be in good condition.
Diodes?
Change all the resistors?
anything else?
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Post by hodge on Oct 20, 2017 10:35:33 GMT
I'd not heard of these before so had a quick google: quote: 'Campfire Audio Andromeda In-Ear Earphone Review 11 BY TWISTER6 ON MAY 23, 2016 EARPHONES, REVIEWS The galaxy of Andromeda – a constellation of coherency and harmony! PROS: out of this galaxy smooth revealing sound tuning, solid industrial design, premium quality removable cable, luxurious leather case. CONS: the comfort of the fit is eartip dependent, the shell design could have softer corners, expect some hissing. Manufacturer website (Campfire Audio Andromeda 5x BA driver IEM): www.campfireaudio.com/andromeda/ (MSRP $1,099). Many Thanks to Campfire Audio for providing the review unit of Andromeda in exchange for my honest opinion.' this quote is from theheadphonelist.com/headphone_review/campfire-audio-andromeda-in-ear-earphone-review/note CONS . . seems you are not alone. |
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Post by PinkFloyd on Oct 20, 2017 10:50:35 GMT
Recently splurged a little bit and upgraded my setup. I got a really sensitive pair of IEM (Andromeda) and while it sounds great, it magnifies the hiss coming out of my V2 to the point that anything aside from loud music are unlistenable. I really like the sound of the V2 so I need to de-hiss his thing. Where is the hiss coming from? What can I do to minimize the hissing? I have tried different tubes, in fact, 4 different sets of 6922 (Russian Shield, Amperex, Sovtek, original Philips). All give similar amount of hiss. The PS caps has been changed out already recently, so those should be in good condition. Diodes? Change all the resistors? anything else? It's the 12.8 ohm LOW impedance of the headphones that is causing the hiss. Recommended impedance for the V2 is 32 - 600 ohms, 12.8 is too low. Mike. |
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nando
Been here a while! 
The Frying Dutchman
Always look on the bright side of life
Posts: 393 
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Post by nando on Oct 20, 2017 10:58:16 GMT
Could you simply place a resistor somewhere between the V2 and the earphones?
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Post by PinkFloyd on Oct 20, 2017 11:05:41 GMT
Could you simply place a resistor somewhere between the V2 and the earphones? Something like this:  Instead of 73ohm use 75ohm resistors..... that should be fine. The V2 doesn't really like 32ohm so anywhere from 40 - 75 will be fine, feel free to experiment  If you use 30ohm it will be 30 + 12.8 = 42.8ohm etc. etc. The above was an adaptor I made 10 years ago to convert the Etymotic ER4P to an ER4S: www.rock-grotto.co.uk/etymotic.htm |
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Post by jmpsmash on Oct 20, 2017 17:02:47 GMT
wouldn't putting a resistor roll off the bass?
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Post by jmpsmash on Oct 20, 2017 17:04:09 GMT
from the schematic, there is a 33 Ohm resistor just before the decoupling cap. what's the point of that? is it because the gain is too high?
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Post by PinkFloyd on Oct 20, 2017 18:38:03 GMT
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Post by jmpsmash on Oct 20, 2017 18:53:33 GMT
AAhhhh!!!!!! Thanks Mike, you might have just saved my V2.  |
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Post by PinkFloyd on Oct 20, 2017 19:57:33 GMT
AAhhhh!!!!!! Thanks Mike, you might have just saved my V2. No worries It's the wrong amp for the IEM's you've chosen... anything low Z will hiss like a snake with a V2. The V2 was designed around the Sennheiser HD580 which have an impedance of 300 ohms. The "standard" back then was 120 ohms, it was a universal standard. 12 ohm headphone loads and 0 ohm output impedances are relatively "modern" and not always a good thing. Your V2 is perfectly OK but it won't do zilch for a pair of IEM's with a 12 ohm impedance... well, it WILL..... it will hiss like a snake and bite you in the "asp" for pairing such a ridiculous pair of 'phones with it . Best regards, Mike. |
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Post by PinkFloyd on Oct 20, 2017 20:02:04 GMT
Why on earth would you want to wear in ear monitors with a non portable / desktop amp? 12 ohm? That was never a good idea was it? |
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Post by jmpsmash on Oct 20, 2017 20:09:04 GMT
Why on earth would you want to wear in ear monitors with a non portable / desktop amp? 12 ohm? That was never a good idea was it? let me try the resistor trick and see. It is actually my work setup. I listen to music most of the day. I cannot wear big phones for a long day coz they give me headaches. So IEM is my only choice! I actually got a iFi iDSD as my DAC which works, but I still prefer tubey sound! |
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Post by PinkFloyd on Oct 20, 2017 20:18:54 GMT
Why on earth would you want to wear in ear monitors with a non portable / desktop amp? 12 ohm? That was never a good idea was it? let me try the resistor trick and see. It is actually my work setup. I listen to music most of the day. I cannot wear big phones for a long day coz they give me headaches. So IEM is my only choice! I actually got a iFi iDSD as my DAC which works, but I still prefer tubey sound! The resistor "trick" WILL do the job, no doubt about that. Let me know how you get on with it. In your particular case you're better off going down Frans' route.... that will 101% work, he's a genius: diyaudioheaven.wordpress.com/headphones/headphone-attenuation-adapter/ |
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Post by PinkFloyd on Oct 20, 2017 20:30:22 GMT
It'll be fiddly Smash, when I made my 75ohm adaptors they were 6.3mm jacks and inline sockets..... you'll be making a 3.5mm jack / socket adaptor so space is REALLY limited..... SMD resistors are the way to go but you need damned good eyesight and very good soldering skills to DIY..... I'm sure you have both.
All the best,
Mike.
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Post by jmpsmash on Oct 20, 2017 20:57:01 GMT
It'll be fiddly Smash, when I made my 75ohm adaptors they were 6.3mm jacks and inline sockets..... you'll be making a 3.5mm jack / socket adaptor so space is REALLY limited..... SMD resistors are the way to go but you need damned good eyesight and very good soldering skills to DIY..... I'm sure you have both. All the best, Mike. I plan to just do it inside the amp. I am not selling this thing so heck why not. I still want to nail down the source of the hiss though. If I can root cause it and fix it there, it will be better than patching it. I guess time to dig out the oscilloscope from storage. Btw, I was looking at what a top notch audio grade resistor cost... here: www.mouser.com/Search/Refine.aspx?Keyword=vishay+z201US$25 EACH! I need to start scratching some lottery tickets. For something more realistic, metal film resistors should get it most of the way. they are in the region of US$0.30-0.40 each. Not cheap for a resistor given the V2 has around... 50. I need to get enough to justify $10 shipping! |
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Post by PinkFloyd on Oct 20, 2017 21:09:16 GMT
You're missing the point Smash.... please re-read the article very carefully.
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Post by jmpsmash on Oct 20, 2017 21:23:50 GMT
Even if i add the 3.3R resistor, like it says in this diagram for the V2:  I can do that in the underside of the PCB near the output, no? In addition, I'd still like to root cause and minimize the hiss. |
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Post by jmpsmash on Oct 20, 2017 21:36:25 GMT
I am still wondering though. This is the V2 output stage. It seems like the output impedance is intentionally made high by a 33R R214. Now I imagine I will probably end up blowing up my IEM / ears if i bypass that, but that's more because the V2 is too powerful for sensitive IEM. And the reason why MF put the 33R there to save ppl's ears and IEMs. However, is there something I can do to lower the gain of the output stage or the gain of the diff amp stage? In my iFi iDSD, there is a IEM switch that pretty much do similar as that 33R/3.3R plug, unfortunately it also kills off some low frequencies which is undesirable.  |
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Post by jmpsmash on Oct 30, 2017 4:35:05 GMT
not giving up on the V2 yet.
I took out R214, the 33R that is series with the output. bass came back! no longer thin sound.
the hiss though, is still there. but at least we have good response to work with. if i had fixed the hiss and go no bass, then the whole exercise would be worthless.
now onto the hiss!
what is surprising is that it is still able to drive the super sensitive Andromeda at reasonable volume. the knob is at around 8 o'clock.
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Post by jmpsmash on Oct 30, 2017 6:17:45 GMT
more update.
swapped out the Russian tubes that I got many years ago and put back the Sovteks. and the noise almost halved! the hiss is still there but it is tolerable.
I played around with the scope a little. the noise is visible almost everywhere, from the tube output all the way to the end. I have tried disconnecting R108, and that silenced it out, but then, the music and everything else got silenced along with it too! so that's not gonna work.
btw, the hiss is presence all the time, and turning the volume knob don't affect it.
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Post by jmpsmash on Oct 30, 2017 8:32:07 GMT
it is 1:30am. I have been sitting here for the past 2-3 hours listening to the output resistor-less + Sovtek V2 + Andromeda. I don't think I have ever heard the V2 sound so good before. There is a little hiss, but not bad. I'd say it is between a ADD and a AAD CD quality. (anyone old enough to understand what that mean?)
In particular, I am using the DAC of my iFi Micro iDSD BL, and then A/B comparing between the iDSD amp and the V2. V2 wins hands down. treble extension and clarity is better. and along with it, better sound stage. tubey warmth. and BASS. heavy bass. almost too heavy actually. speed is very apparent too, both in the bass and mid end.
when compared to the thin sound with the output resistor still intact, this is a 180 degree difference. So if anyone want to experiment with getting a better bass response, try bypassing that resistor (R114/R214). Btw, I already have the 1000uF output capacitor.
I think I should be going to bed. need to work tomorrow.
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Post by jmpsmash on Nov 2, 2017 20:32:31 GMT
Tried a couple more things.
Swapped in a pair of Telefunken 6DJ8 that I had for another amp. Swapping it out right away as the hiss is even worse than the Russian. I guess I am stuck with the Sovteks which are bearable.
I have ordered a whole set of metal film resistors. Kinda expensive but heck why not. They have arrived at my mailbox, will find out if that makes a different or not. I am the feeling the limitation is the tube itself though.
The amp is listenable despite the hiss. The bass seems very strong but at the same time, the mid is open and the treble is clear. The whole presentation is slightly colored and forward. In fact, I prefer using it as the amp stage instead of the iFi Micro iDSD amp stage, which has a more laid back and neutral sound.
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Post by jmpsmash on Nov 3, 2017 16:33:05 GMT
Changed most of the resistors to Vishay/Dale CMF metal film. most are 0.5W/1W 0.1%/0.5% depending on the availability. The hiss? I'd say lower by 20%. not significant, I believe the tube and the circuit has the most influence. I also tried mucking around with the output resistors like Mike suggested, yes, it did lower the hiss, but also killed the bass (I'd rather have hiss than have no bass!) The sound did improve along with it. I can hear more texture and details from all the instruments. Separation is better. Which is kinda what I expected with better quality resistors and tighter matched values. I still have a few more to go. That was a lot of work and went way passed midnight. After this though. I think I am done with the V2. There aren't many thing else to replace anymore!  |
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Post by jmpsmash on Nov 6, 2017 18:30:07 GMT
I am done with this V2 when it comes to replacing components. Aside from the transistors, there really isn't much to be done anymore. The hiss is still there but at a bearable level. It is a beauty to look inside with the WIMA caps and Dale resistors. Which btw, the Dale resistors made a very noticable improvement to give an extra step in clarify and texture. I have been burning it in 24/7 over the weekend. Maybe it is time to move on?    |
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Post by jmpsmash on Nov 6, 2017 19:01:33 GMT
Mike, did you ever try the Project Ember? How does it compare to the V2?
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