Warming up this topic once more (I hope it's worth it......)
The usual audio bug kept biting me, so I did my homework, reading all possible comments and mods done by others, and finally I decided to do the whole gamut, a complete upgrade of this -seriously underrated- amp.
Here is a list of ALL mods I've done in about one month. Important to notice, that I've started this after acquiring an other Intek in its full original glory, untouched, fully working, so I was able to do a direct comparision after each step not to fool myself the usual way -like "it must be better after the mods...."
1. Rectifier diodes replaced with ultrafast BYW 29-200 200v 8A rectifiers
2. Main filter caps replaced with 12.000 uF 56V Elna Audio types
(bypassed with 2.2uF MKP-s)
3. The output Zobel mess is replaced with a single 0.1uF-4.7 ohm network
4. Opamp (NE 5532) replaced with LM 6172 (after trying about 8 different types....) feedback leg bypassed with 10pF to reduce overshot at HF.
5. Power amp feedback parallel leg 220uF replaced with 1000uf Elna SilmicII-s
6. Power amp input HF shunting cap (2.2nF) replaced with 680pF styro
7. ALL other electrolytics (power supplies, local decoupling) either replaced with low ESR types and bypassed, or just bypassed with 0.22uF Wima MKP-s.
8 Transformer is shielded with a copper sheet shorting ring connected to ground.
Well, after all of this I think this amp sounds the way it was intended to. (I didn't touch the phono section, so these observations are only for the high level inputs....) Now it is a tiger in silk kimono, it has Impact, low bass is excellent, the highs are silky smooth, detail and resolution is exemplary. Compared to the factory version.... well, in best case it is sad.
I hope all of you having this little gem find this info useful, give me a feedback of your experience if you decide to do it....
The usual audio bug kept biting me, so I did my homework, reading all possible comments and mods done by others, and finally I decided to do the whole gamut, a complete upgrade of this -seriously underrated- amp.
Here is a list of ALL mods I've done in about one month. Important to notice, that I've started this after acquiring an other Intek in its full original glory, untouched, fully working, so I was able to do a direct comparision after each step not to fool myself the usual way -like "it must be better after the mods...."
1. Rectifier diodes replaced with ultrafast BYW 29-200 200v 8A rectifiers
2. Main filter caps replaced with 12.000 uF 56V Elna Audio types
(bypassed with 2.2uF MKP-s)
3. The output Zobel mess is replaced with a single 0.1uF-4.7 ohm network
4. Opamp (NE 5532) replaced with LM 6172 (after trying about 8 different types....) feedback leg bypassed with 10pF to reduce overshot at HF.
5. Power amp feedback parallel leg 220uF replaced with 1000uf Elna SilmicII-s
6. Power amp input HF shunting cap (2.2nF) replaced with 680pF styro
7. ALL other electrolytics (power supplies, local decoupling) either replaced with low ESR types and bypassed, or just bypassed with 0.22uF Wima MKP-s.
8 Transformer is shielded with a copper sheet shorting ring connected to ground.
Well, after all of this I think this amp sounds the way it was intended to. (I didn't touch the phono section, so these observations are only for the high level inputs....) Now it is a tiger in silk kimono, it has Impact, low bass is excellent, the highs are silky smooth, detail and resolution is exemplary. Compared to the factory version.... well, in best case it is sad.
I hope all of you having this little gem find this info useful, give me a feedback of your experience if you decide to do it....
Some more on the mod.... Add a small heatsink on the poweramp driver stage PS trannies (Q409-419), they get scorching hot without them. Also I was playing with a cap- 0.22 - 2.2uF- ("switch-off speed-up") across the Vbe setting transistors (C-E of Q208-308), but I am not sure of the effect, sommetimes it is better, sometimes it is not. They screw up transients in a way I don't really like- but on certain material the effect is good.
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