Musical Fidelity Synthesis Amplifier upgrades

[PinkFloyd]

I gave this old girl a full re-cap and a few other tweaks and the results (compared to the sound before the re-cap tweaks) are a night and day improvement. The owner of the Synthesis (Max) has had the amp since new (over 30 years) and he has told me he wouldn't mind sharing his thoughts on the sound quality after the tweaks so I'll leave that up to him.

All of the electrolytic capacitors were replaced with new ones, like for like values, APART from the 6,800uF / 63V power caps which were replaced by 10,000uF / 63V EPCOS types. The 2200uF / 25V power caps were replaced with 3300uF / 35V types.

10,000uF / 63V 105c EPCOS:

Hosted on Fotki

Hosted on Fotki

3300uF / 35V 105c Rubycon:

Hosted on Fotki

The rest of the recap was done with like for like value caps but decent quality capacitors were employed (ELNA Silmic ll, Panasonic FM etc.)

Hosted on Fotki

Hosted on Fotki

A big thank you to John Sampson (Musical Fidelity's head service engineer for over thirty years) for helping me out with a few extra tweaks which REALLY reaped sonic dividends!

The first of those being the removal of the speaker fuses, these were official MF updates back in the day.

The existing fuses (there are two of them) are removed and replaced by 16 gauge copper wire, you can see the two culprits here:

Hosted on Fotki

Hosted on Fotki

These were removed and replaced with 16 gauge copper wire links / F1L and F1R:

Hosted on Fotki

Hosted on Fotki

The second John Sampson tweak was the removal of the 2 x carbon resistors in the Zobel network which could make the output stage become unstable..... these were replaced with 2 watt metal film types / both 5r6 / 5.6ohm values.

This image shows you what's what:

Hosted on Fotki

As I said earlier, all of the other caps were replaced with like for like "good quality types".

To my ears the results of the re-cap were nothing short of stunning. I expected a major improvement just from the recap alone (remember, this amp is over 30 years old and the caps way past their best) but was pretty much blown away when I implemented John Sampson's fuse and carbon resistor removal "tweaks" so, once again, thank you for your input on this one John it is most appreciated and I owe you one

jsaudiorepairs.co.uk/upgrades/

All in all this didn't just save the Synthesis from the bin, it went to prove that an old amp can be rejuvinated and blow away many brand new amps.... an amp's an amp after all I wish we could do the same with the human body, Jesus the arthritis in my left hand is getting bad.... it's getting to the stage I tend not to use it anymore.... a "re-bone" would be the answer but it would appear that "pain management" is the only "fix" the health service offer...... cutting edge stuff that is.... stick a plaster on it and eat a pain killer.

Anyhoo..... I hope that this is of interest / assistance / help to any Musical Fidelity Synthesis amplifier owners and I trust Max will come along with a review of the sound quality.

Mike.

[PinkFloyd]

Worth doing

[maxwell]

Hi all,
Mike has invited me to comment on the improvements in sound his tweaks to my amp shown below.

Firstly my musical tastes.
Classical:- symphonies, opera, choral, chamber music, piano music and solo voice.
Type of sound:- Most of my early listening took place in concert halls(I still go to concerts, but at £35-£40 for a mid range seat, not that often) Therefore I look for a concert hall sound.
Equipment:- M.F. Synthesis amp(below) bought 1983. Kef reference 102/2 speakers bought 92/93 M.F. A308 cr CD player bought 2003/4. Speaker cables Chord Odyssey 2. Interconnects Cardas.
I had contacted Mike about something different, we exchange emails, chatted and got on well, I eventually mentioned the issues with my amp.
Highs particularly in vocal and choral breaking up.
Bass losing depth and focus and becoming very muddy.
The various strands of the instruments losing focus and merging.
The attack and weight of the brass etc weakening.
The soundstage was narrowing and losing depth
All in all the sound was becoming wishy washy and losing its edge.

Mike gave me a very reasonable quote to tweak it, and I agreed.(the best musical decision I have made in the last 15 years).
The result.
1. Bass much deeper and more defined.
2. Trebles much clearer and not breaking up so much(the Treble sound is still improving)
3. The amp sings again it is fast and rythmic.
4. The attack, speed and weight is suberb. The brass comes in so heavy and fast it sends shivers down your spine.
5. Piano sound like piano again, the decay on the notes is great and it is like being in the room with it.
6. Voices and instruments tonal qualities are bang on.
7. Soundstage is great, both in width and depth.
8. The acoustics are even better than they were.
9. Most importantly for me it has regain the emotion that was one of the main reasons I bought this amp, sad music makes you want to cry and happy music to laugh.

I could go on and on boring everyone with all of the improvements, but I will mention the one downside, yes there is one.
In classical music many great perfomances were recorded years ago(in the 40's, 50's and 60's). Many of them have been transferred to CD's, and I have them in my collection.
The amp now shows all of the shortcomings of the original recordings!
One last word, I would reccomend anyone with a good old amp to get it tweaked as it could outperform many of the new amps and save you a fortune.
Mike a great thank you for all your hard work and expertise in sorting this old girl and turing her back into a sprightly teenager, and also to John for his invaluable advice. Thank you guys.
Max

[nando]

Good stuff! Have fun with it.

[Blake C]

Can't tell you how pleased I was to read this thread.

I have a Synthesis that I love dearly, and have been considering a re-cap. But it looks like the re-cap will only take me part of the way there: So the speaker fuses will be coming out, and those carbon resistors. I do wonder if there is a circuit diagram still in existence somewhere - I have tried for years to find one. I would love to be able to set the idle currents correctly. And one last comment - those bloody bulbs keep flickering - does my head in. This is such an understated amplifier - I'm lucky it is still working after 30+ years. Thanks for this great thread, and the details you have shared!

Blake

[andrew]

Hello dear friends and fidelity lovers!

I have one short question regarding my beloved 85 synthesis:
Does anyone of you knows the exact current amperage of its' symmetrical transformer. One channel has left me without my permission and we need to rebuild a new transformer
Thanks in advance
and cheers

[PinkFloyd]

Jun 30, 2019 20:52:17 GMT andrew said:

Hello dear friends and fidelity lovers!

I have one short question regarding my beloved 85 synthesis:
Does anyone of you knows the exact current amperage of its' symmetrical transformer. One channel has left me without my permission and we need to rebuild a new transformer
Thanks in advance
and cheers

Hi Andrew,

Welcome to the forum. The only guy on planet earth with that type of detailed info is John Sampson (Musical Fidelity's head service engineer for over 25 years) pop him an e-mail (tell him you've spoken to Mike and I suggested you contact him) [e-mail] if John doesn't know then nobody does.

Hope this helps,

All the best,

Mike.

[andrew]

Hi Mike,

thanks a lot for your welcome greetings and for responding to my post so quickly. I will contact the head engineer, what else does rest me to do in order to get my old friend and companion "SYNTHESIS" alive again.

Bye bye
Andrew

[xris]

Hi all. Good to see this amp is still being talked about.
One of them has come on my bench, the MOSFETs for one side seems to have gone.
But I have a question about the bulbs.
The three here are blown and it would be nice to return this with all bells and whistles. I like your tips on refreshing the sound.
Does anyone know what are the best replacement bulbs.
They're powered straight of one side of the 15v AC supply.
Thanks

[PinkFloyd]

Jul 31, 2019 22:32:18 GMT xris said:

Hi all. Good to see this amp is still being talked about.
One of them has come on my bench, the MOSFETs for one side seems to have gone.
But I have a question about the bulbs.
The three here are blown and it would be nice to return this with all bells and whistles. I like your tips on refreshing the sound.
Does anyone know what are the best replacement bulbs.
They're powered straight of one side of the 15v AC supply.
Thanks

Contact John Sampson, he will be able to point you in the right direction: [e-mail]

All the best,

Mike.

[wardrivingpimp]

Just dug this thread up, thanks Google!
I need to do this upgrade on my Synthesis
Would you have a parts list of the Caps you replaced other than the main 4 caps? Or do I simply pull them all out to identify them?

Much appreciated

[PinkFloyd]

May 25, 2020 20:55:10 GMT wardrivingpimp said:

Just dug this thread up, thanks Google!
I need to do this upgrade on my Synthesis
Would you have a parts list of the Caps you replaced other than the main 4 caps? Or do I simply pull them all out to identify them?

Much appreciated

Simply "look" at the other caps, they all have their values / voltages printed on them.

All the best,

Mike.

[brownz]

Just had one land on my desk today. Lovely sounding box when "refreshed".

"Not a warranty job" ;-)

[wardrivingpimp]

May 25, 2020 20:55:10 GMT wardrivingpimp said:

Just dug this thread up, thanks Google!
I need to do this upgrade on my Synthesis
Would you have a parts list of the Caps you replaced other than the main 4 caps? Or do I simply pull them all out to identify them?

Much appreciated

Recap, resistors and fuses done.
Really pleased with the sound. Slight hum from the amp. May have been there before but nothing noticeable in the audio. Should I be concerned?

Bloody lamps though 🤪

[wardrivingpimp]

Nov 8, 2020 1:58:25 GMT wardrivingpimp said:

May 25, 2020 20:55:10 GMT wardrivingpimp said:

Just dug this thread up, thanks Google!
I need to do this upgrade on my Synthesis
Would you have a parts list of the Caps you replaced other than the main 4 caps? Or do I simply pull them all out to identify them?

Much appreciated

Recap, resistors and fuses done.
Really pleased with the sound. Slight hum from the amp. May have been there before but nothing noticeable in the audio. Should I be concerned?

Bloody lamps though 🤪

The transformer Hum is a little annoying. It has only started since the recap, fuses and resistor swap. Is this possibly something I have done for this to start? Everything I read on this points to simply being mechanical. Maybe just how I have put it back in the case? Is that realistic? Any help greatly appreciated