Mullard ECL86 3 Watt Economical Amp. - UK Vintage Radio Repair and Restoration Discussion Forum

percival007 · 8th Jul 2010, 9:35 pm

I have just finished making the Mullard Single ECL86 Amp as can be found here:-

http://www.r-type.org/static/2-3.htm

I have already built the 3-3 Single Ended EL84 Amp so as i had two ECL86's (one with a White label and one with a Yellow label, but hey!) doing nothing i thought i'd have a go.

The Mullard circuits found on the 'National Valve Museum' i think are a great way for one to 'learn' about Valves in Audio circuits. I am a bit of a novice when it comes to Valves as can be seen from some of the questions i have asked on here! If followed to the letter (and with some advice from you chaps and chapesses) they can form a very good grounding. I can heartily recommend to anyone wanting to gain more knowledge about the subject to 'have a go' at one of the more simple designs found on this website:-

http://www.r-type.org/

I bought the box and transformers second hand from ebay but the rest of the components used were all second hand rescued from dead or dying units. I'm not sure how much i've spent but it's not a lot.

Sorry for going on

but i thought i'd share!!

James.

dave walsh · 8th Jul 2010, 10:15 pm

Very nice James! Maybe novice is not quite the right term. I bet it sounds great as well

. Dave W

percival007 · 9th Jul 2010, 6:24 pm

It does sound nice Dave.

I am possibly not partnering it with the most 'friendly' speakers, i am using my Rega ELA's but it copes quite nicely.

James.

Sideband · 9th Jul 2010, 9:59 pm

Quote:

Originally Posted by percival007

(one with a White label and one with a Yellow label, but hey!)

Don't worry about the colour of the printing....there is a lot of audiophool nonsense about yellow letters and white letters. It's all

!! It may depend on what factory they came from or whether they were made in Europe or the UK...or just that the yellow paint ran out so they used white!

Just use the amp and enjoy it. Bet it sounds good

SB

percival007 · 10th Jul 2010, 9:34 am

Quote:

Originally Posted by Sideband

Don't worry about the colour of the printing...

I can't tell any difference between the two channels.

Quote:

Originally Posted by Sideband

Bet it sounds good...

It does, it sounds lovely.

JC

David G4EBT · 13th Jul 2010, 7:33 pm

Excellent James - very nice cabinet - was that home-brew too?

The article refers to 'the layout being critical - hence PCB construction' but seems not to give any info on PCB layouts. Did you use PCBs or point to point wiring? I've got a scrap unidentifiable German radio chassis which had a stereo audio section using two EL84s. I've toyed with using the mains transformer and the two EL84 audio transformers as the basis of an audio amp.

The 3/3 and 5/10 and Quads all had very neat tag-strip layouts and wiring looms.

David

Aub · 13th Jul 2010, 10:24 pm

I built a stereo amp using an ECL86 for each channel a few years ago. I use it for my everyday hi-fi. Doesnt look as nice as yours though!

Cheers

Aub

percival007 · 13th Jul 2010, 11:30 pm

Thanks folks.

Quote:

Originally Posted by David G4EBT

very nice cabinet - was that home-brew too? ...

No, i'm not that good at the metalwork side of DIY!! It was an ebay purchase from a chap in Hong Kong, complete with connectors, mains switch, volume knob and blue LED.

Quote:

Originally Posted by David G4EBT

Did you use PCBs or point to point wiring? ...

It is all 'Point to Point' wiring. There is little room in there for circuit boards whether they be 'vero-board' or home made PCB. I did though use some 'Tag Strips' for 0Volt points. My wiring is not as neat as some of the old units you find/see on the net. They are things of beauty in my opinion, i am in complete awe of the people who wired them. I am not that patient!

The output transformers are quite small so they are internal (otherwise i would have had to find/make some covers for them) so it is quite cramped in there. However it is virtually 'Hum' free unless the ear is placed directly against the speaker, i was very pleased.

Cheers,

James.

Valvepower · 14th Jul 2010, 5:25 pm

Quote:

Originally Posted by percival007

I am possibly not partnering it with the most 'friendly' speakers, i am using my Rega ELA's but it copes quite nicely.

Hi James,

Very nice job.

I feel the Rega ELA speakers are not to bad a partner for the amp, as the Rega ELA is a uncomplicated two way speaker with a straightforward crossover, it’s also a transmission line speaker which will help the efficiency.

Terry.

Hybrid tellies · 14th Jul 2010, 5:51 pm

Looks great. I always dreamed of building one using a PCL86.

percival007 · 14th Jul 2010, 7:47 pm

Do it !!!

It will sound lovely.

James.

Hybrid tellies · 15th Jul 2010, 12:30 pm

Yeah I think I have the parts lying around. And you are right all the tellies that used the PCL86 did sound great. I am sure that it is the same as an ECL86 apart from the heater voltage.

percival007 · 15th Jul 2010, 6:55 pm

Quote:

Originally Posted by Hybrid tellies

I am sure that it is the same as an ECL86 apart from the heater voltage.

They seem to have different figures? ...

http://www.r-type.org/exhib/aai0028.htm
http://www.r-type.org/exhib/aaa0034.htm

but i am still getting to grips with what all that info actually means!!

I'm sure someone on here (maybe yourself?) will know for sure.

Regards,

James.

neon indicator · 15th Jul 2010, 8:56 pm

The "P" series are all different voltages. The current on all is 300mA to allow series wiring.

The "E" series are all 6.3V (mostly?) and different currents.

C = triode
L = pentode

A PCL86 is not simply a 300mA version of an 6.3V ECL86
See http://www.bvws.org.uk/405alive/tech/valvenos1.html

Scroll to RECEIVING AND GENERAL PURPOSE VALVES

the 8x suffix (ECC81, ECC82, ECL86 etc) means B9A base
the last digit, even figure denotes sharp cut-off characteristic, odd for variable-mu characteristic
so PCL86 and ECL86 are "similar" but not different heater ratings of same valve.

percival007 · 15th Jul 2010, 9:43 pm

Thanks for that information, very usefull, and a great web page, thanks for the link.

James.

G8HQP Dave · 15th Jul 2010, 10:49 pm

I think for all practical purposes a PCL86 and ECL86 can be considered to be the same valve, apart from the heater. The minor differences relate more to different bias points for different HT voltages (lower HT for P series), rather than any difference in the valve. They are on the same page in the Vade-Mecum (as is the UCL86 and YCL86).

However, this is not always true. The PCL83 and ECL83 have the same pentode but different triodes. The PL84 is the same as EL86 - in effect a low impedance version of EL84.

Quote:

even figure denotes sharp cut-off characteristic, odd for variable-mu characteristic

Not always true, although often said. The EF91 is sharp cutoff, the EF92 is vari-mu. The EBF80 is vari-mu, so is the EBF89. I believe the EF41 and EF42 are both vari-mu? You just have to look at the datasheet - all the number tells you is the valve base. With triodes the ECC84 is semi-remote cutoff, the ECC81 is fairly sharp.

neon indicator · 16th Jul 2010, 10:24 pm

All good points.

Of course it depends how picky a design is too. Some designs I believe needed particular makes of valve? Same part number different makers not always the same?
EF51?

G8HQP Dave · 17th Jul 2010, 3:03 pm

Very few good designs need a particular make of valve. The exceptions are mainly when 'equivalents', even when bearing the same name, are actually different. RF PA valves are one possible area of problem e.g. there are several variants of 6146.

I used to wonder why guitarists were so fussy about which make of valve was used. Some of it is just a matter of fashion, and the placebo effect. However, I recently discovered what some of it is due to: large grid stoppers. Some guitar amps have such poor layout that in order to keep them stable they have high value grid stoppers - 100's of K. The result is that the HF frequency response (cutoff below 10kHz in some cases) depends directly on anode-grid capacitance, amplified by the Miller effect. This will vary a bit from one variant of, say, ECC83 to another. It will even depend on how your particular amp was built, due to variations in exact component location.

Mullard push-pull designs can suffer from a different potential problem, due to the DC coupled phase splitter. The bias for this depends on the anode voltage of the previous stage (EF86), so there is some scope for variation.

neon indicator · 17th Jul 2010, 9:12 pm

Though usually the 6146 variants have a suffix?
One at least is claimed to be simply a more robust heater type. Again the effects are most seen at 30MHz on an FT101, though I've heard the 6146 was developed as a VHF valve. I did have early FT101ZD and now have a MkIII.

There also seems to be a "fashion" to build audio amps with RF PAs in recent years. Seems daft to me.

G8HQP Dave · 17th Jul 2010, 9:28 pm

I did read somewhere once that 6146 suffixes can sometimes be misleading, and initially the problems were denied. A 6146W can be either equivalent to 6146A or 6146B. Yes, I think it was intended for low VHF, which may be why it oscillates when the neutralisation is not quite right.

Using Class C RF PA valves for audio output does seem rather perverse, but these are mainly used in amps intended to be conversation pieces rather than merely apparatus for enjoying music.

8th Jul 2010, 9:35 pm	#1
percival007 Heptode Join Date: May 2005 Location: Oxfordshire, UK. Posts: 852	Mullard ECL86 3 Watt Economical Amp. I have just finished making the Mullard Single ECL86 Amp as can be found here:- http://www.r-type.org/static/2-3.htm I have already built the 3-3 Single Ended EL84 Amp so as i had two ECL86's (one with a White label and one with a Yellow label, but hey!) doing nothing i thought i'd have a go. The Mullard circuits found on the 'National Valve Museum' i think are a great way for one to 'learn' about Valves in Audio circuits. I am a bit of a novice when it comes to Valves as can be seen from some of the questions i have asked on here! If followed to the letter (and with some advice from you chaps and chapesses) they can form a very good grounding. I can heartily recommend to anyone wanting to gain more knowledge about the subject to 'have a go' at one of the more simple designs found on this website:- http://www.r-type.org/ I bought the box and transformers second hand from ebay but the rest of the components used were all second hand rescued from dead or dying units. I'm not sure how much i've spent but it's not a lot. Sorry for going on but i thought i'd share!! James. Attached Thumbnails

8th Jul 2010, 10:15 pm	#2
dave walsh Dekatron Join Date: Jan 2006 Location: Ramsbottom (Nr Bury) Lancs or Bexhill (Nr Hastings) Sussex. Posts: 5,817	Re: ''Mullard ECL86 3 Watt Economical Amp. Very nice James! Maybe novice is not quite the right term. I bet it sounds great as well. Dave W

9th Jul 2010, 6:24 pm	#3
percival007 Heptode Join Date: May 2005 Location: Oxfordshire, UK. Posts: 852	Re: ''Mullard ECL86 3 Watt Economical Amp. It does sound nice Dave. I am possibly not partnering it with the most 'friendly' speakers, i am using my Rega ELA's but it copes quite nicely. James.

13th Jul 2010, 7:33 pm	#6
David G4EBT Dekatron Join Date: Feb 2003 Location: Cottingham, East Yorkshire, UK. Posts: 5,761	Re: Mullard ECL86 3 Watt Economical Amp. Excellent James - very nice cabinet - was that home-brew too? The article refers to 'the layout being critical - hence PCB construction' but seems not to give any info on PCB layouts. Did you use PCBs or point to point wiring? I've got a scrap unidentifiable German radio chassis which had a stereo audio section using two EL84s. I've toyed with using the mains transformer and the two EL84 audio transformers as the basis of an audio amp. The 3/3 and 5/10 and Quads all had very neat tag-strip layouts and wiring looms. David

13th Jul 2010, 10:24 pm	#7
Aub Nonode Join Date: Mar 2005 Location: Nuneaton, Warwickshire, UK. Posts: 2,039	Re: Mullard ECL86 3 Watt Economical Amp. I built a stereo amp using an ECL86 for each channel a few years ago. I use it for my everyday hi-fi. Doesnt look as nice as yours though! Cheers Aub __________________ Life's a long song, but the tune ends too soon for us all.

14th Jul 2010, 5:51 pm	#10
Hybrid tellies Nonode Join Date: Jan 2004 Location: 1966-1976 Coverack in Cornwall and Helston Cornwall. 1976-present Bristol/Bath area. Posts: 2,965	Re: Mullard ECL86 3 Watt Economical Amp. Looks great. I always dreamed of building one using a PCL86. __________________ Simon BVWS member

14th Jul 2010, 7:47 pm	#11
percival007 Heptode Join Date: May 2005 Location: Oxfordshire, UK. Posts: 852	Re: Mullard ECL86 3 Watt Economical Amp. Do it !!! It will sound lovely. James.

15th Jul 2010, 12:30 pm	#12
Hybrid tellies Nonode Join Date: Jan 2004 Location: 1966-1976 Coverack in Cornwall and Helston Cornwall. 1976-present Bristol/Bath area. Posts: 2,965	Re: Mullard ECL86 3 Watt Economical Amp. Yeah I think I have the parts lying around. And you are right all the tellies that used the PCL86 did sound great. I am sure that it is the same as an ECL86 apart from the heater voltage. __________________ Simon BVWS member

15th Jul 2010, 8:56 pm	#14
neon indicator Retired Dormant Member Join Date: Jun 2010 Location: Co. Limerick, Ireland. Posts: 1,183	Re: Mullard ECL86 3 Watt Economical Amp. The "P" series are all different voltages. The current on all is 300mA to allow series wiring. The "E" series are all 6.3V (mostly?) and different currents. C = triode L = pentode A PCL86 is not simply a 300mA version of an 6.3V ECL86 See http://www.bvws.org.uk/405alive/tech/valvenos1.html Scroll to RECEIVING AND GENERAL PURPOSE VALVES the 8x suffix (ECC81, ECC82, ECL86 etc) means B9A base the last digit, even figure denotes sharp cut-off characteristic, odd for variable-mu characteristic so PCL86 and ECL86 are "similar" but not different heater ratings of same valve.

15th Jul 2010, 9:43 pm	#15
percival007 Heptode Join Date: May 2005 Location: Oxfordshire, UK. Posts: 852	Re: Mullard ECL86 3 Watt Economical Amp. Thanks for that information, very usefull, and a great web page, thanks for the link. James.

16th Jul 2010, 10:24 pm	#17
neon indicator Retired Dormant Member Join Date: Jun 2010 Location: Co. Limerick, Ireland. Posts: 1,183	Re: Mullard ECL86 3 Watt Economical Amp. All good points. Of course it depends how picky a design is too. Some designs I believe needed particular makes of valve? Same part number different makers not always the same? EF51?

17th Jul 2010, 3:03 pm	#18
G8HQP Dave Rest in Peace Join Date: Sep 2008 Location: Solihull, West Midlands, UK. Posts: 4,872	Re: Mullard ECL86 3 Watt Economical Amp. Very few good designs need a particular make of valve. The exceptions are mainly when 'equivalents', even when bearing the same name, are actually different. RF PA valves are one possible area of problem e.g. there are several variants of 6146. I used to wonder why guitarists were so fussy about which make of valve was used. Some of it is just a matter of fashion, and the placebo effect. However, I recently discovered what some of it is due to: large grid stoppers. Some guitar amps have such poor layout that in order to keep them stable they have high value grid stoppers - 100's of K. The result is that the HF frequency response (cutoff below 10kHz in some cases) depends directly on anode-grid capacitance, amplified by the Miller effect. This will vary a bit from one variant of, say, ECC83 to another. It will even depend on how your particular amp was built, due to variations in exact component location. Mullard push-pull designs can suffer from a different potential problem, due to the DC coupled phase splitter. The bias for this depends on the anode voltage of the previous stage (EF86), so there is some scope for variation.

17th Jul 2010, 9:12 pm	#19
neon indicator Retired Dormant Member Join Date: Jun 2010 Location: Co. Limerick, Ireland. Posts: 1,183	Re: Mullard ECL86 3 Watt Economical Amp. Though usually the 6146 variants have a suffix? One at least is claimed to be simply a more robust heater type. Again the effects are most seen at 30MHz on an FT101, though I've heard the 6146 was developed as a VHF valve. I did have early FT101ZD and now have a MkIII. There also seems to be a "fashion" to build audio amps with RF PAs in recent years. Seems daft to me.

17th Jul 2010, 9:28 pm	#20
G8HQP Dave Rest in Peace Join Date: Sep 2008 Location: Solihull, West Midlands, UK. Posts: 4,872	Re: Mullard ECL86 3 Watt Economical Amp. I did read somewhere once that 6146 suffixes can sometimes be misleading, and initially the problems were denied. A 6146W can be either equivalent to 6146A or 6146B. Yes, I think it was intended for low VHF, which may be why it oscillates when the neutralisation is not quite right. Using Class C RF PA valves for audio output does seem rather perverse, but these are mainly used in amps intended to be conversation pieces rather than merely apparatus for enjoying music.