Musical Fidelity P170 Power Amp

[anatech]

Hi Marcus,
I'd leave the LM318 in there. It is blazingly fast, around 70V / uS. If you replace it with another, you may need to redo the HF compensation.

I was never impressed with these toasters. There is not enough current to charge and discharge the gate properly. The driver stage is not well designed. This amp "is what it is".

-Chris

[maggusch]

Hi anatch, maf_au...

thanx for your answers...guys....

OK...I´ll keep the original opamps (+ TL082 in Phono Preamp)....

I´ver heard somany amps against this toaster.....(camtech, arcam, diy, aaron, cambridge)....they all were loosing...

lack of imagestage and this bloomy fatty beat sound that makes your foot tapping to the ground....I´mean just by changing the internal mf a1 FE Phonostage to an external Cambridge 640p my Linn LP12 sounded almost like a cd-player....!

I have some nice diy ETON-Speaker (air motion transformer and 5" bass/mids in d´appolito) together with a double subwoofer that goes with 22cm vifa...

So I´ll just increase the external main transformer, changing the caps to panasonic FC and somecoupling foils and stay with this toaster....

Or have you made a further step in high end growing to musical reality? (I don´t know bigger/newer musical fidelitys)

regards marcus

[AMV8]

Maf au

I own a number of Dr t, P170, P270 and P370.

The P170 uses the slimmed down circuit of the P270 mk 1. ( As used in the Dr T mK 2 ) If you do not have that circuit e mail me. It is an excellant circuit and I prefer it to the P270 circuit with an extra stage in. It produces a clearer sound but uses a lower bias.

On the p170 and P270Mk 1 the LM318 is the input pair. On the P270 Mk 2 the input pair in the lm318 is disabled and replaced by discrete transistors. I think you will find the lm 318 sounds very good in its own right as it is a high speed op amp. I have still to find an advantage in changing it out - and I have tried a lot of alternatives.

For the burned out voltage drop resistors on the rails I have swapped the original 5w resistors for 25w resistors and the temperature is just ok then. Later models use a pass transistor instead of a resistor to eliminate this problem.

I find that changing out all the circuit board capacitors makes the big change with this circuit. Also increasing the value of the power supply caps to about 40,000uf per rail makes a big difference. If you do that add a thermistor in the transformer incoming supply to avoid start up surges.

Don

[anatech]

Hi Marcus,

OK...I´ll keep the original opamps (+ TL082 in Phono Preamp)....

Now those you should change. Try a newer OPA2132 or any other FET input op amp. This will greatly reduce the hiss and improve the sound quality. The new LM4562 or LME49720 might be better still.

I´ver heard somany amps against this toaster.....(camtech, arcam, diy, aaron, cambridge)....they all were loosing...

No kidding!
I have serviced a number of these over here. A Cyrus would sound much better in keeping with English products. Very modern design (cutting edge actually) and reliable. The older type II's need a recap job by now. I just got a pair of Mono X monoblocks. They will dust most amplifiers on the market. The new Creek Destiny is another good sounding amplifier from your neck of the woods.

So I´ll just increase the external main transformer

I'm really not sure why you would do that. The filter caps are the main issue.

Hi Don,

For the burned out voltage drop resistors on the rails I have swapped the original 5w resistors for 25w resistors and the temperature is just ok then.

You know, the sad thing is that there is no reason at all to run them that hot. A simple transistor regulator will do the trick nicely. I used to do the same thing you did. Mount new resistors to the chassis or heat sink assy. You are further ahead just not dissipating that much heat to begin with.

-Chris

[jamie_mcd]

Hello all,

I have a Musical Fidelity P170 and would like to know if anyone can provide the spec for me as I have misplaced my manual and have been asked for the information by a guy who is repairing it.

Can anyone help?

Many thanks

[ianfromnotts]

Is this any help?

[tiefbassuebertr]

Originally Posted by ianfromnotts

Is this any help?

I am looking for an exact circuit description so as calculation rules of this topology. I haven't see similar topology by other commercial brands, and even not by diy projects. What is here very special (particularly benefits compare to others in respect to the sonic transmission) ??

[tiefbassuebertr]

Originally Posted by tiefbassuebertr

I am looking for an exact circuit description so as calculation rules of this topology. I haven't see similar topology by other commercial brands, and even not by diy projects. What is here very special (particularly benefits compare to others in respect to the sonic transmission) ??

any news?

Musical Fidelity uses this topology by various other models like F16/F19 - P170/P270 and A370 - probably at some more models from those days.
here some URLs of the mentioned models:
?? P270-2 MUSICAL FIDELITY ????? ?????? McIntosh/JBL/audio-technica/Jeff Rowland/Accuphase/?/?¾?????
MyAVµøÅ¥°Ó±¡ºô - Musical Fidelity P270 (aÃþ«á¯Å)(¤G¤â/$00000000/®ç¶é¿¤)
Musical Fidelity P270
P270-2 MUSICAL FIDELITY HiFi-Do McIntosh/JBL/audio-technica/Jeff Rowland/Accuphase
Musical Fidelity P-140X PowerAmp without Transformer, need help!
Musical Fidelity P270 - strange power off noise
http://www.audiodesignguide.com/doc/...elity_a370.jpg (A370/F16)
schematic a370
http://peufeu.free.fr/audio/schemas/...arch_D400a.JPG (Audio Research Power Follower D400)

Concerning the P170 on diyaudio there are this threads:
Musical Fidelity P170 Blown Transistors
musical fidelity p170
P170 Power Amp My First Post
musical fidelity p170 power amp
Musical Fidelity P170 Power Amp
Musical Fidelity P170 Bias