Expert Amp identification - UK Vintage Radio Repair and Restoration Discussion Forum

Matt Black · 27th Apr 2019, 2:45 pm

Hi, I'm new here. I have a couple of super vintage radios, designed by my Grandad Wells Coates, which need to get repaired.
However my first question here is about an old valve Amp which I want to give away, or perhaps sell. My late dad lent it to me in the 70s, then it returned to him and its been in a box ever since. Think he said it was made by Expert. The amp has no makers name or model visible. I googled around and couldn't get any info, then found this excellent looking site! So hoping someone might enlighten me.
The valves for it are there. So, here attached are some pics.

thanks!
Matt

Refugee · 27th Apr 2019, 2:58 pm

It looks like a mid 1950s PA or cinema amplifier.
I have a pair from that period with mostly the same valves and they are certainly from a cinema having the name Paramount imbossed in the case.

ms660 · 27th Apr 2019, 3:00 pm

Expert Gramophones Ltd. ?:

https://www.americanradiohistory.com...arch=%22expert amplifier%22

https://www.americanradiohistory.com...arch=%22expert gramophones%22

An example of one of their amplifiers:

http://www.gramophonemuseum.com/expert-stereosuite.html

Lawrence.

paulsherwin · 27th Apr 2019, 3:03 pm

Quote:

Originally Posted by Refugee

It looks like a mid 1950s PA or cinema amplifier.
I have a pair from that period with mostly the same valves and they are certainly from a cinema having the name Paramount imbossed in the case.

It looks a bit weedy for a cinema amp, though it might do for a small place. The quality of construction seems high. It might be from a school hall or similar.

Refugee · 27th Apr 2019, 3:10 pm

Those EL37s will give 25W in triode wired mode and a 15 inch speaker behind the screen.
That is what 1950s flea pits used to have.
Bigger venues used to have bigger amplifiers though.

Ted Kendall · 27th Apr 2019, 3:13 pm

I think it may well be an Expert - given the differences between the two examples of the same type in one of the links and the fact that they were hand-built in small quantities, variations evidently came with the territory. If it be an Expert, it will at least be well made.

Radio Wrangler · 27th Apr 2019, 7:07 pm

You're most welcome here.

It looks post-war with a choice of valves based on what was easily available at the time.
The proportions og the transformers and the choke as well as the way that no two are in the same orientation is evidence of some care in its creation. Either it's a one-off or a product of a small-scale firm (or one which was small at the time)

Something for a small cinema or a small dance hall, I suspect.

David

rontech · 28th Apr 2019, 9:18 am

I think some cinema speaker systems used quite large folded horn type drivers. These would have a very high "loudness to watts" efficiency and a a 25 watt amp would produce a surprising sound level.

Back in the 60's / 70's I provided sound effects for a local amateur dramatic society. The system used two large ( moveable ) bass reflex cabinets each a with 12" Vitavox drive unit.

The amp was a domestic Leak TL/25 with the Leak Varislope preamp.

I prided myself on achieving realistic sound effects. ( The theatre has a 400 seat auditorium ) and I regularly struggled with producers about the sound effects being too loud.

Refugee · 28th Apr 2019, 10:13 am

I had a better look at the valves.
There is two rectifiers there and the chassis has seven holders.
I would guess that there was once another pentode that would have driven an exciter lamp and been powered by the second rectifier.

Matt Black · 7th May 2019, 6:56 pm

Thank you all for your info!

27th Apr 2019, 2:45 pm	#1
Matt Black Retired Dormant Member Join Date: Apr 2019 Location: Moreton in Marsh, Gloucestershire, UK. Posts: 2	Expert Amp identification Hi, I'm new here. I have a couple of super vintage radios, designed by my Grandad Wells Coates, which need to get repaired. However my first question here is about an old valve Amp which I want to give away, or perhaps sell. My late dad lent it to me in the 70s, then it returned to him and its been in a box ever since. Think he said it was made by Expert. The amp has no makers name or model visible. I googled around and couldn't get any info, then found this excellent looking site! So hoping someone might enlighten me. The valves for it are there. So, here attached are some pics. thanks! Matt Attached Thumbnails

27th Apr 2019, 2:58 pm	#2
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,554	Re: Expert Amp identification It looks like a mid 1950s PA or cinema amplifier. I have a pair from that period with mostly the same valves and they are certainly from a cinema having the name Paramount imbossed in the case.

27th Apr 2019, 3:00 pm	#3
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Expert Amp identification Expert Gramophones Ltd. ?: https://www.americanradiohistory.com...arch=%22expert amplifier%22 https://www.americanradiohistory.com...arch=%22expert gramophones%22 An example of one of their amplifiers: http://www.gramophonemuseum.com/expert-stereosuite.html Lawrence. Last edited by ms660; 27th Apr 2019 at 3:03 pm. Reason: links added

27th Apr 2019, 3:10 pm	#5
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,554	Re: Expert Amp identification Those EL37s will give 25W in triode wired mode and a 15 inch speaker behind the screen. That is what 1950s flea pits used to have. Bigger venues used to have bigger amplifiers though.

27th Apr 2019, 3:13 pm	#6
Ted Kendall Dekatron Join Date: Jul 2008 Location: Kington, Herefordshire, UK. Posts: 3,675	Re: Expert Amp identification I think it may well be an Expert - given the differences between the two examples of the same type in one of the links and the fact that they were hand-built in small quantities, variations evidently came with the territory. If it be an Expert, it will at least be well made.

27th Apr 2019, 7:07 pm	#7
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,904	Re: Expert Amp identification You're most welcome here. It looks post-war with a choice of valves based on what was easily available at the time. The proportions og the transformers and the choke as well as the way that no two are in the same orientation is evidence of some care in its creation. Either it's a one-off or a product of a small-scale firm (or one which was small at the time) Something for a small cinema or a small dance hall, I suspect. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

28th Apr 2019, 9:18 am	#8
rontech Heptode Join Date: Jun 2017 Location: Southport, Merseyside, UK. Posts: 646	Re: Expert Amp identification I think some cinema speaker systems used quite large folded horn type drivers. These would have a very high "loudness to watts" efficiency and a a 25 watt amp would produce a surprising sound level. Back in the 60's / 70's I provided sound effects for a local amateur dramatic society. The system used two large ( moveable ) bass reflex cabinets each a with 12" Vitavox drive unit. The amp was a domestic Leak TL/25 with the Leak Varislope preamp. I prided myself on achieving realistic sound effects. ( The theatre has a 400 seat auditorium ) and I regularly struggled with producers about the sound effects being too loud. __________________ Time flies like an arrow, fruit flies like a banana

28th Apr 2019, 10:13 am	#9
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,554	Re: Expert Amp identification I had a better look at the valves. There is two rectifiers there and the chassis has seven holders. I would guess that there was once another pentode that would have driven an exciter lamp and been powered by the second rectifier.

7th May 2019, 6:56 pm	#10
Matt Black Retired Dormant Member Join Date: Apr 2019 Location: Moreton in Marsh, Gloucestershire, UK. Posts: 2	Re: Expert Amp identification Thank you all for your info!