Chapman 305 - UK Vintage Radio Repair and Restoration Discussion Forum

RojDW48 · 22nd Feb 2021, 8:10 pm

Does anyone have any info, history on this EL84, P/P stereo amp? A friend has one with no info - looks nice.

barretter · 22nd Feb 2021, 10:55 pm

If you go to
www.argaudio.it
and scroll down a bit you will find an article about the repair and restoration of a Chapman 305-ma amplifier.
I may have a circuit diagram somwhere but don't hold your breath.

barretter · 22nd Feb 2021, 10:57 pm

Google translate will turn the article into English for you.

RojDW48 · 23rd Feb 2021, 12:31 am

Many thanks - it does seem to be well found. Surprising there is so little to find about it.

Synchrodyne · 23rd Feb 2021, 1:35 am

Some information here:

http://ukhhsoc.torrens.org/makers/Ch...Amplifier.jpeg

http://ukhhsoc.torrens.org/makers/Chapman/index.html

As best I can determine, the Chapman amplifiers were "ordinary", using standard circuits. I suppose it was the case of a tuner specialist expanding its product line. (Jason did something similar at about the same time.)

I haven't seen schematics for any of the Chapman amplifiers.

Cheers,

snowman_al · 23rd Feb 2021, 8:15 am

I had one and restored it 20 odd years ago. Finally sold it in 2011. I've seen it on eBay twice since then at considerably more than I got!

Only pictures I have are the completed state. (Digital cameras were not common when I first did it up, so no before pictures.)

I will look through my notes and see what I have. I remember it is not the Mullard 5-10 design. It had Partridge transformers and was sweet sounding.

I had the matching control unit too, but sadly 'modified it' beyond saving...

Alan

Valvepower · 23rd Feb 2021, 9:26 am

Hello,

I've one of these amplifiers, which I restored quite some time ago. Can't find the circuit, although off the top of my head its UL and the driver isn't that dissimilar to the Rogers Cadet (by chance in the background of one of the photos) and Junior, although please don't quote me on it! One thing I do remember the EL84's were slightly under run.

I can get it on the bench and take some better pictures to ascertain the exact circuit - before this I need to get the 'odd-ball' Armstrong (which has similar driver) put to bed and off the bench.

I didn't bother with the control unit as I used it with a 'pot in a box' volume control as I remember it having just enough sensitivity to use it with a CD, DAC or a phono amp with decent output.

Regards
Terry

snowman_al · 23rd Feb 2021, 9:53 am

No notes from my rebuild.
But yes EL84 in Ultra Linear push pull and under run so only 8 watts.

From page 24 of Audio Audio, ''Chapman 305, 1959/64 ... EL84 UL PP ... output impedance 3 or 15Ω ... price £21.'' And, ''CT Chapman (Reproducers) Ltd. Chapel Lane, High Wycombe, Bucks. Then Derritron Ultrasonics from 1962.''

rontech · 23rd Feb 2021, 9:54 am

I had one of these amps from 1962 - 1966. I used it with an EMI EPU100 integrated arm and cartridge ( mm ) A rare pickup. Goodmans AXIOM 400 type speakers. The whole system sounded pretty good back in the day. I recall the 305 preamp had poxy individual gain setting pots in the low level signal path and could be very noisy. Otherwise no problems.

RojDW48 · 23rd Feb 2021, 5:10 pm

I used it with an EMI EPU100 integrated arm and cartridge ( mm ) A rare pickup.

I had one of those many years back - lovely thing, but the cartridge died and I couldn't find anyone to repair it.

22nd Feb 2021, 8:10 pm	#1
RojDW48 Octode Join Date: Jun 2014 Location: Bristol, UK. Posts: 1,770	Chapman 305 Does anyone have any info, history on this EL84, P/P stereo amp? A friend has one with no info - looks nice. __________________ '....don't go mistaking Paradise for that home across the road!' (Bob Dylan)

22nd Feb 2021, 10:55 pm	#2
barretter Heptode Join Date: Jan 2006 Location: Todmorden, West Yorkshire, UK. Posts: 849	Re: Chapman 305 If you go to www.argaudio.it and scroll down a bit you will find an article about the repair and restoration of a Chapman 305-ma amplifier. I may have a circuit diagram somwhere but don't hold your breath.

22nd Feb 2021, 10:57 pm	#3
barretter Heptode Join Date: Jan 2006 Location: Todmorden, West Yorkshire, UK. Posts: 849	Re: Chapman 305 Google translate will turn the article into English for you.

23rd Feb 2021, 12:31 am	#4
RojDW48 Octode Join Date: Jun 2014 Location: Bristol, UK. Posts: 1,770	Re: Chapman 305 Many thanks - it does seem to be well found. Surprising there is so little to find about it. __________________ '....don't go mistaking Paradise for that home across the road!' (Bob Dylan)

23rd Feb 2021, 1:35 am	#5
Synchrodyne Nonode Join Date: Jan 2009 Location: Mt. Maunganui, New Zealand Posts: 2,584	Re: Chapman 305 Some information here: http://ukhhsoc.torrens.org/makers/Ch...Amplifier.jpeg http://ukhhsoc.torrens.org/makers/Chapman/index.html As best I can determine, the Chapman amplifiers were "ordinary", using standard circuits. I suppose it was the case of a tuner specialist expanding its product line. (Jason did something similar at about the same time.) I haven't seen schematics for any of the Chapman amplifiers. Cheers,

23rd Feb 2021, 8:15 am	#6
snowman_al Heptode Join Date: Dec 2018 Location: Llandeilo, West Wales, UK. Posts: 650	Re: Chapman 305 I had one and restored it 20 odd years ago. Finally sold it in 2011. I've seen it on eBay twice since then at considerably more than I got! Only pictures I have are the completed state. (Digital cameras were not common when I first did it up, so no before pictures.) I will look through my notes and see what I have. I remember it is not the Mullard 5-10 design. It had Partridge transformers and was sweet sounding. I had the matching control unit too, but sadly 'modified it' beyond saving... Alan Attached Thumbnails __________________ Never Leave Well Enough Alone...

23rd Feb 2021, 9:26 am	#7
Valvepower Heptode Join Date: Aug 2008 Location: Southend-On-Sea, Essex, UK. Posts: 905	Re: Chapman 305 Hello, I've one of these amplifiers, which I restored quite some time ago. Can't find the circuit, although off the top of my head its UL and the driver isn't that dissimilar to the Rogers Cadet (by chance in the background of one of the photos) and Junior, although please don't quote me on it! One thing I do remember the EL84's were slightly under run. I can get it on the bench and take some better pictures to ascertain the exact circuit - before this I need to get the 'odd-ball' Armstrong (which has similar driver) put to bed and off the bench. I didn't bother with the control unit as I used it with a 'pot in a box' volume control as I remember it having just enough sensitivity to use it with a CD, DAC or a phono amp with decent output. Regards Terry Attached Thumbnails

23rd Feb 2021, 9:53 am	#8
snowman_al Heptode Join Date: Dec 2018 Location: Llandeilo, West Wales, UK. Posts: 650	Re: Chapman 305 No notes from my rebuild. But yes EL84 in Ultra Linear push pull and under run so only 8 watts. From page 24 of Audio Audio, ''Chapman 305, 1959/64 ... EL84 UL PP ... output impedance 3 or 15Ω ... price £21.'' And, ''CT Chapman (Reproducers) Ltd. Chapel Lane, High Wycombe, Bucks. Then Derritron Ultrasonics from 1962.'' __________________ Never Leave Well Enough Alone...

23rd Feb 2021, 9:54 am	#9
rontech Heptode Join Date: Jun 2017 Location: Southport, Merseyside, UK. Posts: 509	Re: Chapman 305 I had one of these amps from 1962 - 1966. I used it with an EMI EPU100 integrated arm and cartridge ( mm ) A rare pickup. Goodmans AXIOM 400 type speakers. The whole system sounded pretty good back in the day. I recall the 305 preamp had poxy individual gain setting pots in the low level signal path and could be very noisy. Otherwise no problems. __________________ Time flies like an arrow, fruit flies like a banana

23rd Feb 2021, 5:10 pm	#10
RojDW48 Octode Join Date: Jun 2014 Location: Bristol, UK. Posts: 1,770	Re: Chapman 305 I used it with an EMI EPU100 integrated arm and cartridge ( mm ) A rare pickup. I had one of those many years back - lovely thing, but the cartridge died and I couldn't find anyone to repair it. __________________ '....don't go mistaking Paradise for that home across the road!' (Bob Dylan)