845 SET "Music Angel" mods

SET Asylum

Single Ended Triodes (SETs), the ultimate tube lovers dream.

There is an archived thread "I'm finally an SET owner BUT" which talks about these "Music Angel" inexpensive Chinese amps.
I've owned one for about 18 months and apart from doing a circuit trace when I first purchased it, I've never had the bottom cover off.
The complaint was that it did not have enough treble response.
On the weekend just passed I decided to tackle exactly that problem with good results.
Mods I performed:
1) The input stage - consists of 6N9P (6SL7) wired as SRPP.
Fitted 47nF/400V Polyester (nothing flash) across the 170V zener and the existing 4.7uF polyester which forms the supply for this stage.

Some of these amps had a DC HEATER supply to the input SRPP stage and some had AC HEATER supply.
If you have one with the AC supply and are experiencing hum then bypass the cathode resistor of the bottom tube of the SRPP with say a 68uF/20V OSCON or a Blackgate or similar.
2) Driver stage - consists of both halves of a 6N8P (6SN7) in parallel. Anode load is approx 36K. There is 20K in the cathode circuit consisting of 19K5 bypassed with a 22uF/250V electrolytic plus a 510 Ohm resistor unbypassed (place to add feedback if desired).
I fitted a 220nF/400V Film/Foil Polypropylene across the 22uF/250V electrolytic.
3) The driver output is coupled to the 845 grid via a 330nF/630V capacitor.
I fitted 3300pF polystryene across the 330nF coupling capacitor
4) Fitted 4700pF/3kV ceramics across the main High Voltage Rectifier Diodes.
Results of the mod were VERY GOOD - Improved Treble response BUT also VERY noticable as a better focussed stereo image.
Hope this is of some interest.
Cheers,
Ian

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Parts Connexion

Topic - 845 SET "Music Angel" mods - Gingertube 18:20:10 02/01/05 (1)

Re: 845 SET "Music Angel" mods - Gingertube 18:37:25 02/01/05 (0)

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