Beam Echo Avantic SPA11 restoration. Help please!
 

Hello, I’m new here – hello all - and relatively new to valve amplification. I’ve acquired an SPA11 which I want to restore to its former glory. Why? My father had one back in the Sixties and it disappeared sometime in the Eighties. I was born in 1969 and I remember it fondly and was surprised by how good this old amp sounded compared to the solid-state amp in the house. This is already a labour of love and this project is dedicated to my Dad!

For about month I have been gathering schematics, manuals and general knowledge about this amp. As I said I’m new to valve amplification but am aware of things like; high voltages, not switching it on without load (speakers). I have built one of those EAR 834 clones and revealed in the astonishing world of ‘audio’ capacitors. Back story over.

I have disconnected the power transformer from the amp and it tests good with HT+ at 270v (DC) and heater at about 7.7v (AC) – the original metal bridge rectifier has been replaced at some point with 4 diodes and a couple of 100 resistors. The volume pot has also been replaced, which doesn’t have the on/off switch of the original. Finally, the resistor and bypass cap that biases the ECC83 triodes have been replaced.

I have a schematic from the original manual and parts list that I’ve been poring over – I can scan and post these but I’m not sure about copyright etc.

I have removed a few of the old carbon composite resistors and tested – unsurprisingly (60 years old) they are over 20% out. I’ll replace all of the capacitors naturally, even though I’m finding it hard to source some.

I understand that it’s a bad idea to replace -everything- but with the carbons way out I don’t see what choice I have and think that replacing the resistors is inevitable. I would like to use this amp when/if it works once day. I don’t want it to just function as an ornament.

I have no idea how to test the output transformer – will definitely need some help there.

I’m stuck right now trying to find replacements for the old paper capacitors:

From preamp ECC83 anode to tone controls (stack?)
0.05uF 350/500V (guessing I can go for 0.047uf)

Couples the preamp to ECL82 (phase splitter stage?)
0.022uF 350/500V

And this one that’s across the output transformers primary windings.
0.001uF 300V AC (dreaded hunts!)

I’m soliciting all your knowledge and wisdom to guide me through this and I’m looking forward to it! :)

Re: Beam Echo Avantic SPA11 restoration. Help please!
 

Where to start?

1) Be aware that not only the amplifier will have changed since the sixties, but also the speakers, cartridges and the recordings will have changed over the period. The golden memories you have attached to the amp may not be entirely its doing.

2) The amazing things about audio capacitors are their prices and people actually paying them. You'll find that most folk on this forum don't believe in mystic audio properties. They know a lot about what works and what is reliable. You can get very good capacitors at pocket-money prices. Expensive capacitors are not necessarily bad, it's just that the extra money seems to be spent on mythology. The modern lurid yellow plastic film capacitors are superb replacements for the old paper jobs in all respects except for appearance. Stay close to the capacitance value. Higher voltage rating is OK, lower is not.

3) Hunts capacitors were OK for their time. All the ones seen now are far far beyond their intended life expectancy. Change the little beggars on sight but don't blame Hunts, they were average quality of their time. The one across the output transformer primary may be better with a much higher rating than 300V.

4) Carbon comp resistors age a lot. Many will need changing because of drift of their resistance. They are also very noisy. This may not be significant in some places in a circuit, but it is in others. I wouldn't think of trying to source old stock carbon composition resistors, but then I'm not strongly dedicated to originality. Metal film for me!

5) There are two things wrong with changing everything... originality goes out the window, and it's difficult to find any errors you made if you change a lot between tests.

6) The output transformers are the one area where the renowned makers pulled off some subtlety in design. They do make a difference. They are very difficult to replace. You usually have to buy a full amplifier for parts, and for anything with a cult following, that is pricey!

7) There were some very nasty transistor amps, and many not very good, but mankind has eventually learned how to do good ones. Don't write them all off. Would you turn down a new BMW M3 because you once disliked a Morris Marina? They've got the same number of seats, wheels etc.

8) how to test an output transformer? Look for faults. Faults include open-circuit windings, bad insulation (high voltage test not multimeter) shorted turns and losses due to rust getting between laminations.

9) use your ears. YOUR OWN EARS and not anyone else's claims of what they hear. Be honest with yourself. If you can't hear something the pundits rave about, trust your ears, not the pundits. Just don't tell anyone you can't see the emperor's new clothes, stay out of the arguments and save the time for listening to some music. Listen to the music, not the equipment. Improve the equipment if it gets in the way of the music.

There is an amazing amount of bull.... in the audio world. It is seductive and it takes self control to not be sucked in.

David

Re: Beam Echo Avantic SPA11 restoration. Help please!
 

Grim Josef (GJ) has experience of working on these Avantic amplifiers (and many others). Search this forum for his posts.

There is also a well-illustrated rebuild thread out there on another forum somewhere. It would be worth searching for too. If I recall correctly, a lot of the carbon comp resistors needed to be replaced too.

Re: Beam Echo Avantic SPA11 restoration. Help please!
 

I have located the thread I have in mind. It is in Pink Fish Media. The main rebuild thread, with lots of detail and photos about the rebuild of an Avantic Beam Echo SPL12 D21 II, is here: https://pinkfishmedia.net/forum/thre...thread.186543/.

In my limited experience of two mono Avantic integrated amps, they need a lot of restoration.

Re: Beam Echo Avantic SPA11 restoration. Help please!
 

I've just restored a couple of these. They are pretty easy to get right it you watch a few things.

1) The contact cooled rectifier will now be useless. Replace it with 1000V silicon bridge rectifier unit with about 160R in series with its positive DC output. If the rest is OK this should leave the HT about right.

2) Replace all the Hunts and Wima capacitors. I used some nice little Nichicon ones from RS which have the right ratings and are small and brown (therefore inconspicuous). Don't forget the two on top of the output transformer block - they are under the cover so are easy to miss. The output transformers can get ruined if these are defective.

3) It is hard to reach the components behind the ECL82 bases but there is work here to do so the little sub-chassis will have to come out. Unsoldering the wires into the loom from underneath will make it easier - make plenty of notes as to where it all goes! There are four (usually Hunts) 10nF grid coupling capacitors to be found here, along with the 25uF cathode decouplers, the cathode resistors and the anode loads for the triodes of the ECL82s. All are suspect, give the aggro of reaching them I'd replace the lot. I didn't have to replace many resistors but obviously anything over 100k or under 500R is worth running the meter over. Don't get hung up and start cutting the whole thing to pieces for errors or 10 > 20%, these were designed for loose tolerance components and changing resistors this close won't make any difference.

4) The electrical safety aspects of this design are dubious at best. Make sure that the chassis is earthed and that the thermal cutout (between the mains transformer and one of the ECL82s) cannot short to the chassis. Also make sure that the mains switch is properly mounted and isn't about to fall apart.

5) There are two voltage selector plugs underneath, make sure that the correct 'range' plug (red or green) is inserted and that the little screw-in pin is tight. Both of these need to be removed to dismantle the cabinet - this soon becomes tedious.

6) Note that although all the inputs are 'line' level the PU (turntable) one is routed through a 1M resistor shunted by a 25pF capacitor. This may match a ceramic cartridge OK but doesn't suit much else. These components may have already been removed - they reside on the source selector switch.

7) The balance control is in the cathode circuit of the output valves and so passes DC, making crackly operation very likely. The circuit around here was changed a number of times so don't rely too heavily on the diagram when working in this area.

Other than that everything is straightforward. Not a bad little amplifier and quite 'modern' in its feel and layout. If you are using modern loudspeakers leave the impedance tap on the 4 ohm setting - you lose a bit of level but the bass will be all over the place at the higher settings. Since the volume control works passively on the inputs you can't overload this amplifier with modern sources (like a CD player), making it easy to interface to. Against this, the recording output is a bit of a joke as its level changes with the volume control setting. It is best ignored.

If you want to play records you'll need the STEP11 magnetic cartridge equaliser / amplifier. This runs from the HT/LT outputs on the back of the SPA11 and despite being fairly simple works pretty well. The same Wima capacitors and tired cathode decouplers will be found in here too, but it doesn't take long to overhaul this unit.

Re: Beam Echo Avantic SPA11 restoration. Help please!
 

When the ECL86 came out in 1962, there was a flurry of new designs (e.g. Rogers and Tripletone) but prior to that, this Avantic SPA11 Stereo amplifier was one of very few to make good use of the earlier ECL82 - few Hi Fi manufacturers had previouly used single-envelope triode-pentodes. I remember thinking it's circuitry and styling very advanced for the time. Another early example was the EMI/Capitol Stereo unit using ECL83s.

Re: Beam Echo Avantic SPA11 restoration. Help please!
 

Wow! that's a lot of useful replies and very quickly.

I've order a load of Arcol Carbon Composite Resistors so there goes the originality!

I did contact GrimJosef already who runs http://www.ampregen.com

Thanks!

This appears to have been replaced with 4 diodes & resistors some time ago - I've tested this with the power transformer and all appears good - we will see under load!

I assuming polyester are a bad idea here? I have been looking at polypropylene caps as replacements and Wima are the list. As another alternative what about the 715P Polypropylene Orange Drop Capacitors (600V) for the 0.047uf and 0.022uF?

The output transformer caps are rated as '0.001uF, 300 V., AC, Metallized Paper' - what value and rating would you suggest here? would 600V DC caps do?

To retain some originality I'd like to use axial but i have had little luck finding polypropylene caps at 600V in the values i need.

If you could post some links to suitable replacements that would really help!

Re: Beam Echo Avantic SPA11 restoration. Help please!
 

As regards replacing the caps get a 0.047u or 47n. Most of us use 630v rated axial caps like these -
http://uk.farnell.com/vishay/mkt1813...ial/dp/1166877

Andy.

Re: Beam Echo Avantic SPA11 restoration. Help please!
 

Thanks!

so polyester are ok for hi-fi audio and 715P Polypropylene Orange Drops are not?

Some say polyester are for guitar amps - something to do with high distortion. is that nonsense?

Re: Beam Echo Avantic SPA11 restoration. Help please!
 

The differences in the characteristics of different plastic film technologies are completely insignificant at audio frequencies. Capacitors don't have a 'sound'. This is pure audiophool stuff.

https://rationalwiki.org/wiki/Audio_woo

Re: Beam Echo Avantic SPA11 restoration. Help please!
 

Thank you. :)

Re: Beam Echo Avantic SPA11 restoration. Help please!
 

The 300VAC 0.001uf caps, use 1000VDC capacitors for those.

Re: Beam Echo Avantic SPA11 restoration. Help please!
 

Ouch! So I wasn't convincing enough?

Differences in sound for different resistor materials is also audiophool stuff

Why buy carbon composition resistors when you can get long-lived, stable, low noise parts?

I've no qualms about changing everything. If you're a beginner, do it in small stages to put a cap on the number of errors to be traced at any one time. But I'd much rather fit the best components I can get if I'm swapping things.

David

Re: Beam Echo Avantic SPA11 restoration. Help please!
 

I had ordered them already - could be an expensive mistake. :wall:

Re: Beam Echo Avantic SPA11 restoration. Help please!
 

Here are some pictures of mine. It had had a hard life before I got it so it isn't the tidiest in the world, but I did what I could to get it back into decent, original condition without too much fuss. Most of the original resistors are still there simply because there was nothing wrong with them. the Nichicon capacitors are the shiny terracotta coloured things, they came from RS. They are 400V rated and look much like the originals, they were also easily available, from a highly reputable manufacturer and cheap! I agree that capacitors don't have a "sound" unless they are knackered. No point spending out big money on them then.

The big white 'polo mint' thing is a 160R dropper section to keep the silicon rectifier at bay. I left the contact cooled one in place (disconnected) for appearances; the silicon replacement is just next to the smoothing can (underneath).

ECL82s are certainly a blessing, who hasn't got boxes full of those? Also, they seem a lot more reliable than ECL86s, a valve which always seems to have something wrong with it (usually sharp CRACK noises and microphony, with a bit of grid current thrown in). Times that by four in a typical model (e.g. Rogers Cadet) and trouble is never far away, or at least it hasn't been in the ECL86 based amplifiers which I've owned (even the B&O ones...). Incidentally, the Cadet is rated at 6W but the SPA11 claims 7 (midband, and with horrendous distortion figures for both no doubt) so there really is no advantage to the '86.

It works well enough, certainly there is no hum an noise audible from the listening position even with sensitive (90dB/W/1m) loudspeakers. This exposes the 'resistor noise' argument for the myth that it is. It is just a simple circuit with AC heaters and wiring all over the place, a different type of resistor used here and there isn't going to change any of that. Best to keep it as original as possible to preserve the pleasure of owning and using something which is still genuinely "old", rather than a collection of modern parts recently patched into an old box. Remember too that like any old valve amplifier these aren't really 'hi-fi' as one would understand it now but they are a lot of fun to get working, nice to use and pleasant enough to listen to. The best results I got out of it were with an odd system indeed - the SPA11 and STEP11 used with a Technics SL-10 turntable with an AT-85E cartridge in it and Technics SB-F1 loudspeakers! I have the tuner too but that has been more of a struggle to get right, I don't think I'm quite there on that yet.

Re: Beam Echo Avantic SPA11 restoration. Help please!
 

Amps like these weren't built with exotic audiophile components, just good quality mainstream parts largely selected on price.

Re: Beam Echo Avantic SPA11 restoration. Help please!
 

Most of the capacitors are ordered. I went for polyester as suggested - thanks for the help. I already had a big 100uF+100uF and I've ordered 4 32uF's that I'll hide underneath and retain the original 32uF+32uF for looks. I'm going to bite the bullet go with the carbons resistors I have and retain as many of the originals as I can.
I cant find a 200uF 6V electrolytic for the triode bias bypass - any help here would be appreciated.

I wouldn't mind some close ups of your amp for reference - the resistors in mine are (cosmetically at least) in much worse condition - the majority are loosing their colour bands or are blackened. the several i have removed and tested were > 20% out. How did you clean the aluminium? it looks like new my amp is much dirtier internally.

If the amp works again maybe we could put them head to head and see how they compare?

Re: Beam Echo Avantic SPA11 restoration. Help please!
 

The face plate on your amp is slightly different - mine doesn't have the switch on the right hand side - what is it for?

Re: Beam Echo Avantic SPA11 restoration. Help please!
 

220uF will probably be easier to find and will be fine - electrolytic tolerances are quite wide. You don't need to use a 6V part, just something that is rated at 6V or higher. Modern electrolytics are much smaller than vintage ones.

Re: Beam Echo Avantic SPA11 restoration. Help please!
 

Here is the datasheet for the resistors, i have the RCC050 1/2W type. What do you think?

https://docs-emea.rs-online.com/webd...6b81539afb.pdf

Thanks!