hello people...ive got this fatman itube mk1 13w per channel 😱 the problem is it sounds dull and distorted but when i touch my hand on the metal on the back of the phono lead and put my other hand anywhere on the metal casing it goes normal? strange but true, ive had it apart and looked for anything that could be shorting it out but it all looks good, theres no broken tracks or loose wires, any ideas? this is the first tube amp ive ever owned i got it cheap, when its on the metal at the top of the tubes has got small hole on it, any help or ideas would be greatly appreciated guys, cheers
Sounds like a bad earth,
Check the continuity between the phono socket and the chassis or to where it connects on the circuit board.
Has it got more than one input? is it the same on the other inputs?
If it is then check the selector switch connections.
NB make sure its dead before you touch anything. The amp contains high voltages.
Just a few things to try.🙂
Regards
M. Gregg
Check the continuity between the phono socket and the chassis or to where it connects on the circuit board.
Has it got more than one input? is it the same on the other inputs?
If it is then check the selector switch connections.
NB make sure its dead before you touch anything. The amp contains high voltages.
Just a few things to try.🙂
Regards
M. Gregg
RF oscillation?
Is this a genuine valve amp or a chip amp with a cathode follower in front of it?
Is this a genuine valve amp or a chip amp with a cathode follower in front of it?
amp
hello, thanks for the replies, its the same on both inputs, ile have another look tonight at the selector switch connections, the only other thing im thinking now is i didnt take the actual power supply out of the casing and i could only see so much of it, maybe i should take that out and check it, im not sure what kind of amp it is but i dont remember seeing any chips inside it.. ile lok over it again and report back, thanks again guys cheers
hello, thanks for the replies, its the same on both inputs, ile have another look tonight at the selector switch connections, the only other thing im thinking now is i didnt take the actual power supply out of the casing and i could only see so much of it, maybe i should take that out and check it, im not sure what kind of amp it is but i dont remember seeing any chips inside it.. ile lok over it again and report back, thanks again guys cheers
Yes, just checked. It is not a valve amp. At best it is a hybrid but it could just be a valve preamp (not sure what circuit) in front of a solid-state amp - almost certainly a chip amp given the low price. You can't get 13W from a small twin triode and a magic eye!
The symptoms you describe are consistent with a grounding fault or RF oscillation. If the former it may be easy to fix; if the latter it gets a bit harder as proper fault-finding may be needed. Do you have a DMM and know how to use it?
The symptoms you describe are consistent with a grounding fault or RF oscillation. If the former it may be easy to fix; if the latter it gets a bit harder as proper fault-finding may be needed. Do you have a DMM and know how to use it?
Sure. An analog meter will work fine. Make sure unit is unplugged, caps are discharged, etc... Turn the function selector on the meter to ohms and test away for continuity.
well i took the amp aprt again only this time i took the power pack out, it loks like something has been spilt in there, not sure if that means its shorted out at some point?, suppose ile get the meter out and check a few things, moz
(A quick search showed several threads about the Fatman iTube including this one, so I'm posting here. It may also be of interest in the gainclone forum(s), since it's a tube-buffered gainclone.)
The Fatman iTube (OEM Dared, which also sold its own-branded version, the Dared MP-5) is a tube-buffered gainclone first introduced c.2005, to target the iPod market with a bookshelf tube setup. It became a huge success over the next ~15 years, selling over ~100k units worldwide to a market where it was often their first introduction to vacuum-tube audio on a budget.
http://www.enjoythemusic.com/magazin.../dared_mp5.htm
One of the Fatman versions landed up for auditioning a few days ago, and I must say that I was impressed with its form-factor, pricing, build quality, finish and durability. However, there were some minor drawbacks in its audio quality - very bass-shy (like a lot of tube gear) and with a fair amount of glare/brightness in the upper-mids (not uncommon in chipamps/gainclones). In other words, it had some of the faults of both vacuum-tubes and chipamps.
I tried to address the glare issue first, since I don't really need a thumping bass response (I don't listen much to heavy-metal, disco, hip-hop and similar genres anyway). I generally prefer neutrality, with full-bodied mids for vocals and so on, and the MP-5 seemed to be a great candidate for upgrades.
Opened it up, and noticed that almost all resistors were generic 0.5W CFR, and all electrolytics were generic Chinese 105c TL brand. I swapped out the electrolytics first:
3x 2200uF/35V TL -> 3x 2200uF/35V Elna RKD (chipamp rail bypass, heater/aux DC bypass)
1x 100uF/250V TL -> 1x 100uF/400V Rubycon AXW (cathode-follower B+)
1x 47uF/400V TL -> 1x 33uF/350V Rubycon YK (B+ for magic-eye VU meter, value not critical)
2x interstage coupling capacitors were 1uF/200V, possibly MKT polyesters, and I had excellent MKP substitutes from Asahi Kasei, so that was the next upgrade:
2x 1uF/200V/10% generic MKT ->2x 1uF/250V/5% Asahi Kasei MKP
Finally, a couple of resistor upgrades. The input series resistor was a generic 10k/0.5W CFR, which I replaced with a non-magnetic PRP 10k/0.25W/25 ppm thermal-coefficient. This is in the signal path, so it's critical that it's non-magnetic to reduce EMI/RFI pickup.
The second was in the chipamp voltage-series feedback network - a 560E/0.5W generic CFR in the lower leg of an 18K/560E voltage divider. It's critical for sonics to have an extremely linear resistor here, with very low 2nd- and higher-order voltage coefficient of resistance. Only wire-wounds make the cut, so I swapped in a Vishay 510E/1W wire-wound here - the slightly lower value alters the default chipamp gain by about 10%, which doesn't matter.
2x 10k/0.5W generic CFR -> 2x 10k/0.25W/25ppm non-magnetic PRP
2x 560E/0.5W generic CFR -> 2x 510E/1W Vishay wirewound.
Checked everything, and there was a generic A100k carbon-track pot as the volume control. I left that alone, since I didn't have a quality pot like an Alps for a direct upgrade, and 100k wirewound pots are a rare item - it's a future to-do upgrade.
For now, these upgrades were sufficient to completely eliminate the glare and make it more neutral, but still warm, transparent, detailed and full-bodied,
Here's a pic of the circuit board after the upgrades:
The Fatman iTube (OEM Dared, which also sold its own-branded version, the Dared MP-5) is a tube-buffered gainclone first introduced c.2005, to target the iPod market with a bookshelf tube setup. It became a huge success over the next ~15 years, selling over ~100k units worldwide to a market where it was often their first introduction to vacuum-tube audio on a budget.
http://www.enjoythemusic.com/magazin.../dared_mp5.htm
One of the Fatman versions landed up for auditioning a few days ago, and I must say that I was impressed with its form-factor, pricing, build quality, finish and durability. However, there were some minor drawbacks in its audio quality - very bass-shy (like a lot of tube gear) and with a fair amount of glare/brightness in the upper-mids (not uncommon in chipamps/gainclones). In other words, it had some of the faults of both vacuum-tubes and chipamps.
I tried to address the glare issue first, since I don't really need a thumping bass response (I don't listen much to heavy-metal, disco, hip-hop and similar genres anyway). I generally prefer neutrality, with full-bodied mids for vocals and so on, and the MP-5 seemed to be a great candidate for upgrades.
Opened it up, and noticed that almost all resistors were generic 0.5W CFR, and all electrolytics were generic Chinese 105c TL brand. I swapped out the electrolytics first:
3x 2200uF/35V TL -> 3x 2200uF/35V Elna RKD (chipamp rail bypass, heater/aux DC bypass)
1x 100uF/250V TL -> 1x 100uF/400V Rubycon AXW (cathode-follower B+)
1x 47uF/400V TL -> 1x 33uF/350V Rubycon YK (B+ for magic-eye VU meter, value not critical)
2x interstage coupling capacitors were 1uF/200V, possibly MKT polyesters, and I had excellent MKP substitutes from Asahi Kasei, so that was the next upgrade:
2x 1uF/200V/10% generic MKT ->2x 1uF/250V/5% Asahi Kasei MKP
Finally, a couple of resistor upgrades. The input series resistor was a generic 10k/0.5W CFR, which I replaced with a non-magnetic PRP 10k/0.25W/25 ppm thermal-coefficient. This is in the signal path, so it's critical that it's non-magnetic to reduce EMI/RFI pickup.
The second was in the chipamp voltage-series feedback network - a 560E/0.5W generic CFR in the lower leg of an 18K/560E voltage divider. It's critical for sonics to have an extremely linear resistor here, with very low 2nd- and higher-order voltage coefficient of resistance. Only wire-wounds make the cut, so I swapped in a Vishay 510E/1W wire-wound here - the slightly lower value alters the default chipamp gain by about 10%, which doesn't matter.
2x 10k/0.5W generic CFR -> 2x 10k/0.25W/25ppm non-magnetic PRP
2x 560E/0.5W generic CFR -> 2x 510E/1W Vishay wirewound.
Checked everything, and there was a generic A100k carbon-track pot as the volume control. I left that alone, since I didn't have a quality pot like an Alps for a direct upgrade, and 100k wirewound pots are a rare item - it's a future to-do upgrade.
For now, these upgrades were sufficient to completely eliminate the glare and make it more neutral, but still warm, transparent, detailed and full-bodied,
Here's a pic of the circuit board after the upgrades:
Attachments
Linuxguru, thanks for sharing your mods!
I'm a non-techie newbie so please excuse my uneducated comments and questions.
I recently acquired a used Dared MP-5 (not the Fatman iTube version) and my intention is to use it as a base for a first project.
The amp sounds quite good as it is, sweet midrange, but lacks bass definition, on my version I did not hear any brightness as such.
The unit suffers from the usual potentiometer noise as reported by Gainphile in his blog. Linuxguru have you done the Alps RK16 mod?
Your thoughts and any mod suggestions much appreciated, thanks!
I didn't find the schematic online. Attached some actual pics of my unit.
I'm a non-techie newbie so please excuse my uneducated comments and questions.
I recently acquired a used Dared MP-5 (not the Fatman iTube version) and my intention is to use it as a base for a first project.
The amp sounds quite good as it is, sweet midrange, but lacks bass definition, on my version I did not hear any brightness as such.
The unit suffers from the usual potentiometer noise as reported by Gainphile in his blog. Linuxguru have you done the Alps RK16 mod?
Your thoughts and any mod suggestions much appreciated, thanks!
I didn't find the schematic online. Attached some actual pics of my unit.
Attachments
Very interesting modifications for Fatman itube posted here ! It is the same circuit OEM Dared MP5 and also HCT hms-100 .
Hopefully Linuxguru or anybody else at the forum can help with a clue where to find a service manual as the unit I got requires some adjustments/repairs .!
it will be much appreciated.! So far Ive found nothing on the internet, and even the manufacturer in China is not responding to numerous emails sent past 2 weeks..
Thanks in advance !
Hopefully Linuxguru or anybody else at the forum can help with a clue where to find a service manual as the unit I got requires some adjustments/repairs .!
it will be much appreciated.! So far Ive found nothing on the internet, and even the manufacturer in China is not responding to numerous emails sent past 2 weeks..
Thanks in advance !