kukkurovaca
1000+ Head-Fier
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Judging by my unit: unless you're up to heavier modding than just opamp swapping, yuck.
Portable tube amp from china?
- Thread starter voodoo do-er
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- ttvj-portable-slim
Judging by my unit: unless you're up to heavier modding than just opamp swapping, yuck.
Well finally finished messing with the b4 so here is what i modded and final listening evaluation.
Swapped the op amp to a burson v5i
Changed all the caps to Nichicon's KA Series 16v 105 temp, better stabilty and allows me to tweek the power a bit.
Housing fully copper shielded and it was worthwhile put my mobile phone on the top and no interference... result !
Pcb fully cleaned removing old flux and solder splashes and corrected a few joints that were either a touch dry or over soldered.
High Temp damping rings x 4 added hot glue ( 200 deg melting point so tube heat won't affect).
RTV clear gel added to tips of tubes / pcb for added stability ( ching sound with knock / movement not noticable now)
Added grounding from pcb to chasis, this was a good move as it lowered the noise floor about 5db.
Had a play with the 4 trimmers to get a good combination of power and balance without distortion, did this on various genres of music to get a good balance from the low end to the highs, only moved them maybe a mm or two either way to find the final sweet spot.
Took out the vol pot and cleaned and re greased it, buttery smooth now and no sudden leap in volume ( tweeking the trimmers also helped in this area)
Finally changed the screws to steel torx and a nice new solid aluminium volume knob ( just looked better imo).
Then left the amp running for 10 charges to bed in the new caps and optimize the battery holding charge, i now have an amp that after switching on has no noise whatsoever from the click to the almost immediate low volume ( nicely graduated now no sudden blast) both channels fire up at the same time as well and stay balanced when i sweep up and down the volume scale. Ten o'clock was the max i needed for the 250 ohm 1770 pros and alpha primes to give them the correct drive to make them sing ! did push them a bit more and they stayed clear not that i'll ever use them at that volume but i had to try !
Bass has a nice punch with no muddiness or bleed and vocals are clear without any shrillness, electric guitars have a nice lively sounding ring to them and on the bass guitar on floyds money track i could clearly hear Waters going to town on the strings. All in all a worthy little project that i'm happy with, don't get me wrong if your expecting it to turn into a bottle head crack .....er no ! But it gives enough for me now to keep going back to it just to see what my needle drops and more musical type of tunes sound like with a bit of warmth to it.
Imo the the stock caps aren't bad but I wish I could fit V6 Vivids in it, but I will need to do some work for it.
ledzep
Headphoneus Supremus
Tweeked the trimmers today with excellent results very accurate tuning of balance and no scratching, when dial is switched all the way down it stays balanced and totally black background and also more refined in getting that sweet spot, also was able to turn down the gain so I can use iems with it now without sacrificing power to supply big cans a definite worthwhile upgrade highly recommend.
Regnum
New Head-Fier
A friend had one of these but theirs ended up breaking within a week.
Manzabadman
New Head-Fier
Hi led,
I have insulated my b4 with copper tape and changed the caps like you, I have noticed an improvement in sq and battery life and just wanted to ask where did you buy the trimmers ?
would any good 3 pin trimmer do or are they based on voltage etc
ledzep
Headphoneus Supremus
You need surface mounted 3 pins 2x 200k 2x500k , I'll send you a link later
ledzep
Headphoneus Supremus
https://ie.farnell.com/vishay/tsm4yl204kr05/trimmer-pot-200k-13turn-smd/dp/1141367
https://ie.farnell.com/vishay/tsm4yl504kr05/trimmer-pot-500k-13turn-smd/dp/1141368
I used these as we carry stock at work but there are different manufacturers that vary in price that you can use. Just make sure they are not single turn they are too sensitive the 13 turn are smooth and have plenty of play to be able to gradually get good results. If your not familiar with using trimmers a good starting point is to measure the resistance of the original trimmers and adjust the new ones to the same value before putting them on the PCB that way your not tuning blind just tweeking the stock settings so you don't get lost.
https://ie.farnell.com/vishay/tsm4yl504kr05/trimmer-pot-500k-13turn-smd/dp/1141368
I used these as we carry stock at work but there are different manufacturers that vary in price that you can use. Just make sure they are not single turn they are too sensitive the 13 turn are smooth and have plenty of play to be able to gradually get good results. If your not familiar with using trimmers a good starting point is to measure the resistance of the original trimmers and adjust the new ones to the same value before putting them on the PCB that way your not tuning blind just tweeking the stock settings so you don't get lost.
Manzabadman
New Head-Fier
Thanks for the links and advice ledzep
I found an upgraded version of the b4 - https://www.ebay.co.uk/itm/Little-B...ortable-Headphone-Amplifier-HiFi/283236997632
might be of some interest...
i just bought b4 wish ya sent it earlier!! is that real or fake??
Manzabadman
New Head-Fier
seems to be legit - I bought my b4 from their store (doukstore) about a month ago - I couldn't find this upgraded b4-x on Amazon or anywhere else for that matter so it's fairly new I suppose
- I will order it next week and put a review up if/when it comes
ledzep
Headphoneus Supremus
Yeah thanks, would be interesting to hear the difference
Balanced output and bipolar power supply of the amps must be interesting, but the filament power supply looks to be the same like in old version.
Just try to powered each filament from stable power supply 6.3-6.4V and you will be surprised about sound improvment.
ledzep
Headphoneus Supremus
Bought 4 V5i's need 3 so one is a spare £30 with PayPal or £28 gift I'll cover shipping first come first served.
duals or single?
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