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8th Jul 2010, 9:35 pm | #1 |
Heptode
Join Date: May 2005
Location: Oxfordshire, UK.
Posts: 852
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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. |
8th Jul 2010, 10:15 pm | #2 |
Dekatron
Join Date: Jan 2006
Location: Ramsbottom (Nr Bury) Lancs or Bexhill (Nr Hastings) Sussex.
Posts: 5,817
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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
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9th Jul 2010, 6:24 pm | #3 |
Heptode
Join Date: May 2005
Location: Oxfordshire, UK.
Posts: 852
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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. |
9th Jul 2010, 9:59 pm | #4 | |
Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
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Re: ''Mullard ECL86 3 Watt Economical Amp.
Quote:
Just use the amp and enjoy it. Bet it sounds good SB
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10th Jul 2010, 9:34 am | #5 |
Heptode
Join Date: May 2005
Location: Oxfordshire, UK.
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Re: ''Mullard ECL86 3 Watt Economical Amp.
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13th Jul 2010, 7:33 pm | #6 |
Dekatron
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 5,765
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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 |
Nonode
Join Date: Mar 2005
Location: Nuneaton, Warwickshire, UK.
Posts: 2,039
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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
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13th Jul 2010, 11:30 pm | #8 |
Heptode
Join Date: May 2005
Location: Oxfordshire, UK.
Posts: 852
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Re: Mullard ECL86 3 Watt Economical Amp.
Thanks folks.
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. 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. |
14th Jul 2010, 5:25 pm | #9 | |
Octode
Join Date: Aug 2008
Location: Rayleigh near Southend-On-Sea, Essex, UK.
Posts: 1,883
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Re: ''Mullard ECL86 3 Watt Economical Amp.
Quote:
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. |
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14th Jul 2010, 5:51 pm | #10 |
Nonode
Join Date: Jan 2004
Location: 1966-1976 Coverack in Cornwall and Helston Cornwall. 1976-present Bristol/Bath area.
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Re: Mullard ECL86 3 Watt Economical Amp.
Looks great. I always dreamed of building one using a PCL86.
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14th Jul 2010, 7:47 pm | #11 |
Heptode
Join Date: May 2005
Location: Oxfordshire, UK.
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Re: Mullard ECL86 3 Watt Economical Amp.
Do it !!!
It will sound lovely. James. |
15th Jul 2010, 12:30 pm | #12 |
Nonode
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Location: 1966-1976 Coverack in Cornwall and Helston Cornwall. 1976-present Bristol/Bath area.
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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.
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15th Jul 2010, 6:55 pm | #13 | |
Heptode
Join Date: May 2005
Location: Oxfordshire, UK.
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Re: Mullard ECL86 3 Watt Economical Amp.
Quote:
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. |
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15th Jul 2010, 8:56 pm | #14 |
Retired Dormant Member
Join Date: Jun 2010
Location: Co. Limerick, Ireland.
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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 |
Heptode
Join Date: May 2005
Location: Oxfordshire, UK.
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Re: Mullard ECL86 3 Watt Economical Amp.
Thanks for that information, very usefull, and a great web page, thanks for the link.
James. |
15th Jul 2010, 10:49 pm | #16 | |
Rest in Peace
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Location: Solihull, West Midlands, UK.
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Re: Mullard ECL86 3 Watt Economical Amp.
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:
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16th Jul 2010, 10:24 pm | #17 |
Retired Dormant Member
Join Date: Jun 2010
Location: Co. Limerick, Ireland.
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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 |
Rest in Peace
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Location: Solihull, West Midlands, UK.
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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 |
Retired Dormant Member
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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 |
Rest in Peace
Join Date: Sep 2008
Location: Solihull, West Midlands, UK.
Posts: 4,872
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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. |