Mullard 5-20 - Page 14

Family_Dog · 21st August 2005, 10:56 AM

Hi Ray!

Well, it has it's drawbacks... I seem to have replaced so many light bulbs that are supposed to be rated for 250V since they've upped the national grid. Changed three globes just last week!

But I do remember when I first bought this house, some 30 years ago, that I had AC mains readings as low as 190V during winter. Since they built the new power station though, that is something of the past.

I seem to recall you were also building or repairing 5-20s... or am I thinking of someone else?

-Eric

ray_moth · 21st August 2005, 02:56 PM

No, it wasn't me working on 5-20s. However, I am thinking of building an amp with similar topology but using a 6AU6 as the input pentode stage, a 6SL7 splitter with another 6AU6 as a CCS for the tail, and a pair of EL34s in pentode mode (not UL). I hope the high gain from the pentode input stage, which would be too much for the 5-20 with its UL output stage, should enable me to add enough NFB for a decent damping factor, even with a straight pentode PP ouput stage. I'll also probably include a step network in place of the coupling capacitors between the splitter and the OP tubes, to improve LF phase margin, and use fixed bias. What do you think?

Speaking of the weather in sunny South Africa, it's been unseasonally rainy here in Indonesia since the supposed start of the dry season (May-October, same as northern Australia). Maybe this is a year of el niño?

JDeV · 21st August 2005, 06:55 PM

Quote:

Originally posted by JDeV
Accordng to Mr. Byriths design notes, you should get certain vlotages at certain points. Although I had the HT transformer made according to spec. , I get a little more out of it - HT.
My measured values differ now from the specified values, and I want to know if I must adjust resistors, or are my values acceptable?

After rolling some tubes today, I noticed with some of the older tubes, (for EF86), the voltages are spot on - as specified. So with time the new tubes I am currently using will also give the same voltages.

Just finished a listening session with another hi-fi fanatic and just can not believe the quality of the sound from these amps, truly amasing. My next surprise (pray it will be) is the Seas Thor TL speakers I am bussy building. Hope they do justice to the amps. Will find out within the next week or 2.

Just for the fun, a pic or 2:

Introducing..... the all new super duper Mullard designed, Byrith modified.... EL34 35W monoblock.

JDeV · 21st August 2005, 06:56 PM

And it's belly:

JDeV · 17th February 2010, 08:04 AM

I eventually got the perfect speakers for my Mullards. I build the 'BIB' with Fostex FE207E fullrange drivers. Only one word: WOW!!

This is my definition of Hi-Fi, everything is just perfect, base, mids, highs - it's all exactly how it should be - for my ears ;-)

I now want to replace the tubes, what are the latest, best EL34's, EF86 and ECC83 / 12AX7's recommended for this application?

Thanx for all replies.

Trebla · 17th February 2010, 08:24 AM

My current faves are EH 6CA7 in place of EL34s. Don't really find EH EL34 very interesting though.
Original Svetlanas and JJs always worth trying.
Shuguang can be a bit lightweight sounding but pretty good all the same.
Not tried any exotic ones.

Family_Dog · 17th February 2010, 02:20 PM

Quote:

Originally Posted by JDeV

And it's belly:

Mullard!

Don't laugh - a few years ago I GAVE AWAY 20 x brand new boxed Mullard EL34 tubes, thinking I would have no further use for them. I kept only six, all of which are currently in use.

Heart-breaking, ain't it?

-F_D

JDeV · 17th February 2010, 04:53 PM

Quote:

Originally Posted by Family_Dog

Mullard!

Don't laugh - a few years ago I GAVE AWAY 20 x brand new boxed Mullard EL34 tubes, thinking I would have no further use for them. I kept only six, all of which are currently in use.

Heart-breaking, ain't it?

-F_D

Eric, you should be "named and shamed" for doing that

21st August 2005, 10:56 AM	#131
Family_Dog diyAudio Member Join Date: May 2004 Location: North Western Province of South Africa	Hi Ray! Well, it has it's drawbacks... I seem to have replaced so many light bulbs that are supposed to be rated for 250V since they've upped the national grid. Changed three globes just last week! But I do remember when I first bought this house, some 30 years ago, that I had AC mains readings as low as 190V during winter. Since they built the new power station though, that is something of the past. I seem to recall you were also building or repairing 5-20s... or am I thinking of someone else? -Eric __________________ Vintage Tube Hobby Group: http://groups.yahoo.com/group/vintage_tube/

17th February 2010, 08:04 AM	#135
JDeV diyAudio Member Join Date: Oct 2002 Location: Cape Town	Suggested tubes I eventually got the perfect speakers for my Mullards. I build the 'BIB' with Fostex FE207E fullrange drivers. Only one word: WOW!! This is my definition of Hi-Fi, everything is just perfect, base, mids, highs - it's all exactly how it should be - for my ears ;-) I now want to replace the tubes, what are the latest, best EL34's, EF86 and ECC83 / 12AX7's recommended for this application? Thanx for all replies. __________________ "Be carefull who's advice you buy, but be patient with those who supply it." From Baz Luhrmann's - Everybody’s Free (To Wear Sunscreen)

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21st August 2005, 02:56 PM	#132
ray_moth diyAudio Moderator Emeritus Join Date: Jan 2004 Location: Jakarta	No, it wasn't me working on 5-20s. However, I am thinking of building an amp with similar topology but using a 6AU6 as the input pentode stage, a 6SL7 splitter with another 6AU6 as a CCS for the tail, and a pair of EL34s in pentode mode (not UL). I hope the high gain from the pentode input stage, which would be too much for the 5-20 with its UL output stage, should enable me to add enough NFB for a decent damping factor, even with a straight pentode PP ouput stage. I'll also probably include a step network in place of the coupling capacitors between the splitter and the OP tubes, to improve LF phase margin, and use fixed bias. What do you think? Speaking of the weather in sunny South Africa, it's been unseasonally rainy here in Indonesia since the supposed start of the dry season (May-October, same as northern Australia). Maybe this is a year of el niño?

17th February 2010, 08:24 AM	#136
Trebla diyAudio Member Join Date: Nov 2005 Location: North West	My current faves are EH 6CA7 in place of EL34s. Don't really find EH EL34 very interesting though. Original Svetlanas and JJs always worth trying. Shuguang can be a bit lightweight sounding but pretty good all the same. Not tried any exotic ones.

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