New'ish amp from old radios - UK Vintage Radio Repair and Restoration Discussion Forum

Chatterstatic · 3rd May 2015, 5:07 pm

Hi I was hoping some kind folk could help. I have acquired two old 50's French radio's. First uncased one was found at the local tip and works, but a little crackly. The second cased one has a duff power transformer, and the EZ80 heater is blown. Although I had mainly got the cased one for the case, and the chassis, and any parts that can be salvaged as I aim to put smallish amp back in it.

The working radio has an EZ80, EL41, EBC41, EF41, and ECH81 and as I said it functions and even picks up an English sports station.

The cased Sonaphone Symphonie cadre S7C EF41, ECH81, 6BA6, 6AV6, EL84, "EZ80-Duff" and a EM84 Magic eye.

I also happen to have some 6F31's, 6AG5s, 6AL5's and 6C4's

I would have liked to start building a Mullard 3-3, but wondered if any other simple schematics fitted the bits I have at hand, although stress the easier starting out the 3-3 appealed to me as it is well documented. Lot's of you folk are familiar with it.

This will be my first tube project although, I consider myself safe'ish around High Voltages.

Chatterstatic · 3rd May 2015, 6:07 pm

I forgot to add ultimately I will be adding a Raspberry PI with a DAC so I'm turning this into a vintage internet radio.

Diabolical Artificer · 4th May 2015, 1:51 pm

The 3-3 is the perfect amplifier for a "beginner" to build; the parts count is low and are common and easy to come by, that and the build is very well documented. I can't think of a more suitable little amp for you to build.

Andy.

Herald1360 · 4th May 2015, 4:11 pm

But with no EF86, not a zero cost option.

Either of the radios should provide the wherewithal for a simple triode driving pentode amp.

For more gain, add the triode from the other set onto the front end. (The triodes are in the EBC41 and 6AV6).

Chatterstatic · 4th May 2015, 5:16 pm

EF86 is in the post I couldn't resist, I'm trying to work out how to get the chassis out the case.

Which I did work out whilst typing this all the knobs were holding it in.

bikerhifinut · 4th May 2015, 6:48 pm

Saw this and thought I would throw my pennyworth in.

I built a simple EL84 based amp last year based on alex Kitic's RH84 circuit.
It's very simple, sounds excellent and I have just put it back in the domestic HiFi to refresh my accquaintance of it. It doesn't shame itself partnered with some serious sources and speakers.
I've attached the circuits of the original and revised circuits. I built both and the revised version does have the edge but not by a great deal. I also built it using an Armstrong radiogram mains transformer that only gave 250V Ht but with a 150R cathode resistor it worked fine, just lower on power which may not be an issue.
The present incarnation uses a 10H choke on HT and by very careful heater wiring/routing it has a silent background, which is an achievement by Single ended standards.

I didnt use the published PSU, I have a few EZ81's which are perfect for a couple of EL84's. For a single mono amp I'd use an EZ80.

I should add, It's not as sensitive as the Mullard design, unsurprisingly, so might not be that great off a detector stage.
Also the feedback resistor and component values are optimised for the ECC81/12AX7.

You'd need to tweak values for other triodes. I think on the website he has a "universal" circuit that has values for other triodes.

Andy.

Chatterstatic · 4th May 2015, 8:28 pm

Thank's the RH84 has/is been in the line up my next quandary is with the speakers I have a pair of 8 Ohm B&W drivers gathering dust that come from a CC6 S2 center speaker "item zz11681" the unit was rated at 120 Watt max with both speakers I'm not looking for loads of noise the aim is background at night and gentle listening. If I'm barking up the wrong tree with them I would love some suggestions baring in mind this is all going to be a combined unit.

Ed_Dinning · 4th May 2015, 9:06 pm

Hi The 3-3 is a great amp to build, but you will need a good output transformer to achieve it's full potential. These are still available and can be wound to order.
The mains transformer is not so vital as long as it is approx. the right volts and amps, so could come from an old set.

Ed

Chatterstatic · 4th May 2015, 9:37 pm

Will probably invest in the matched set from vvt it seems to be the most common recommendation here.

bikerhifinut · 5th May 2015, 12:05 am

Good advice from Ed.

As to speakers, I hook mine up to the main hi fi ones which are currently Kudos Cardea standmounters, nominally 6 ohm but I dont really worry about stuff like that. The amp works fine in a medium to small sized room into them. I'd suggest you try your speakers before worrying about others.

I made the RH84 circuit as its a lot simpler and less fussy over layout etc than the mulllard one and I also dodnt need tone controls etc. That plus I had a stash of ECC81 aand a fair few EL84.

Hope that helps.

The Mullard circuit is damn good too of course.

3rd May 2015, 5:07 pm	#1
Chatterstatic Retired Dormant Member Join Date: May 2015 Location: Nantes, France Posts: 8	New'ish amp from old radios Hi I was hoping some kind folk could help. I have acquired two old 50's French radio's. First uncased one was found at the local tip and works, but a little crackly. The second cased one has a duff power transformer, and the EZ80 heater is blown. Although I had mainly got the cased one for the case, and the chassis, and any parts that can be salvaged as I aim to put smallish amp back in it. The working radio has an EZ80, EL41, EBC41, EF41, and ECH81 and as I said it functions and even picks up an English sports station. The cased Sonaphone Symphonie cadre S7C EF41, ECH81, 6BA6, 6AV6, EL84, "EZ80-Duff" and a EM84 Magic eye. I also happen to have some 6F31's, 6AG5s, 6AL5's and 6C4's I would have liked to start building a Mullard 3-3, but wondered if any other simple schematics fitted the bits I have at hand, although stress the easier starting out the 3-3 appealed to me as it is well documented. Lot's of you folk are familiar with it. This will be my first tube project although, I consider myself safe'ish around High Voltages.

3rd May 2015, 6:07 pm	#2
Chatterstatic Retired Dormant Member Join Date: May 2015 Location: Nantes, France Posts: 8	Re: New'ish amp from old radios I forgot to add ultimately I will be adding a Raspberry PI with a DAC so I'm turning this into a vintage internet radio.

4th May 2015, 1:51 pm	#3
Diabolical Artificer Dekatron Join Date: Jul 2009 Location: Sleaford, Lincs. UK. Posts: 7,670	Re: New'ish amp from old radios The 3-3 is the perfect amplifier for a "beginner" to build; the parts count is low and are common and easy to come by, that and the build is very well documented. I can't think of a more suitable little amp for you to build. Andy. __________________ Curiosity hasn't killed this cat...so far.

4th May 2015, 4:11 pm	#4
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,536	Re: New'ish amp from old radios But with no EF86, not a zero cost option. Either of the radios should provide the wherewithal for a simple triode driving pentode amp. For more gain, add the triode from the other set onto the front end. (The triodes are in the EBC41 and 6AV6). __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

4th May 2015, 5:16 pm	#5
Chatterstatic Retired Dormant Member Join Date: May 2015 Location: Nantes, France Posts: 8	Re: New'ish amp from old radios EF86 is in the post I couldn't resist, I'm trying to work out how to get the chassis out the case. Which I did work out whilst typing this all the knobs were holding it in.

4th May 2015, 6:48 pm	#6
bikerhifinut Octode Join Date: Nov 2013 Location: Penrith, Cumbria, UK Posts: 1,993	Re: New'ish amp from old radios Saw this and thought I would throw my pennyworth in. I built a simple EL84 based amp last year based on alex Kitic's RH84 circuit. It's very simple, sounds excellent and I have just put it back in the domestic HiFi to refresh my accquaintance of it. It doesn't shame itself partnered with some serious sources and speakers. I've attached the circuits of the original and revised circuits. I built both and the revised version does have the edge but not by a great deal. I also built it using an Armstrong radiogram mains transformer that only gave 250V Ht but with a 150R cathode resistor it worked fine, just lower on power which may not be an issue. The present incarnation uses a 10H choke on HT and by very careful heater wiring/routing it has a silent background, which is an achievement by Single ended standards. I didnt use the published PSU, I have a few EZ81's which are perfect for a couple of EL84's. For a single mono amp I'd use an EZ80. I should add, It's not as sensitive as the Mullard design, unsurprisingly, so might not be that great off a detector stage. Also the feedback resistor and component values are optimised for the ECC81/12AX7. You'd need to tweak values for other triodes. I think on the website he has a "universal" circuit that has values for other triodes. Andy. Attached Thumbnails

4th May 2015, 8:28 pm	#7
Chatterstatic Retired Dormant Member Join Date: May 2015 Location: Nantes, France Posts: 8	Re: New'ish amp from old radios Thank's the RH84 has/is been in the line up my next quandary is with the speakers I have a pair of 8 Ohm B&W drivers gathering dust that come from a CC6 S2 center speaker "item zz11681" the unit was rated at 120 Watt max with both speakers I'm not looking for loads of noise the aim is background at night and gentle listening. If I'm barking up the wrong tree with them I would love some suggestions baring in mind this is all going to be a combined unit.

4th May 2015, 9:06 pm	#8
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,195	Re: New'ish amp from old radios Hi The 3-3 is a great amp to build, but you will need a good output transformer to achieve it's full potential. These are still available and can be wound to order. The mains transformer is not so vital as long as it is approx. the right volts and amps, so could come from an old set. Ed

4th May 2015, 9:37 pm	#9
Chatterstatic Retired Dormant Member Join Date: May 2015 Location: Nantes, France Posts: 8	Re: New'ish amp from old radios Will probably invest in the matched set from vvt it seems to be the most common recommendation here.

5th May 2015, 12:05 am	#10
bikerhifinut Octode Join Date: Nov 2013 Location: Penrith, Cumbria, UK Posts: 1,993	Re: New'ish amp from old radios Good advice from Ed. As to speakers, I hook mine up to the main hi fi ones which are currently Kudos Cardea standmounters, nominally 6 ohm but I dont really worry about stuff like that. The amp works fine in a medium to small sized room into them. I'd suggest you try your speakers before worrying about others. I made the RH84 circuit as its a lot simpler and less fussy over layout etc than the mulllard one and I also dodnt need tone controls etc. That plus I had a stash of ECC81 aand a fair few EL84. Hope that helps. The Mullard circuit is damn good too of course.