U47 Build using EF80

[Spencerleehorton]

Hi Everyone,

I am planning on building a U47 with psu and using a EF80 tube, this is the BOM i'm planning on using:

resistors 1/4 watt

R1 - 1G ohm
R2 - 1G ohm
R3 - 29 ohm*
R4 - 100ohm as per alternate schematic by oliver archut*
R5 - 100K ohm
R6 - 30k ohm
R7 - 2M ohm
R8 - 3M ohm

* = fixed bias (1N4148 didoes needed)

Capacitors

C1 - 0.01uf  film (400v) Axial Lead
C2 - 1uf 630v paper in oil * (if used need bigger body to fit in)
C3 - 1uf 250v polypropylene axial (have used these in my versions)

Tube

EF80

PSU (corrected) regulated

4 x 1N4007
2 x 1N4002
2 x 470uf/200v
2 x 4700uf 25v
2 x 10000uf/16v
22uf/16v
10k trimmer
500R trimmer
LM350 regulator
200k 1/4w resistor
910R 1/4w resistor
240R 1/4w resistor
3.3R 1w resistor
2.2R 1w resistor

Transformer is  6:1 ratio out of a those cheap Chinese mics, capsules are K-47 from microphone parts.

regards

Spence.

 

[moamps]

It looks to me that the BOM for the PSU is for VF14 or two 408 tubes..
You will  need two voltages; 120V/0,5mA and 5V/400mA, for EF80 based microphone IMO. 

 

[Spencerleehorton]

hi moamps,

thanks i will account for this in the psu, anything else i need to worry about? is there a better tube for this that is readily available?

regards

Spence.

 

[gary o]

I think 1/4 watt resistor be ok for mic

 

[Spencerleehorton]

HI Gary,

thanks for that as i have all of the resistors in 1/4 watt, just gotta figure out this psu and decide 100% on which tube to go for as i do have a couple of mullard EF86 and a red dot telefunken EF86 which could also fit the bill.

regards

Spence.

 

[Spencerleehorton]

Hi All,

Im also considering the double pentode config, if anyone has any comments on this please?

regards

Spence.

 

[gary o]

Hi Spence very interested in what yr doin I am no expert ...... I have read the EF86 wouldnt be good for a U47 circuit maybe would match the Bv8 style transformer I read it sounded way to middley dont let me put you off tho, have a read around see if you can find out more ...

Whats the double pentode ...... is that two tubes in parallell ? I think the Pentode/s would have to be wired as triodes.....

I Have maxes MK47 kit worked good but had bit of noise I re built it point to point & the noise was better I also tried two 6AK7s with seperate heater supply.

 

[Spencerleehorton]

HI Gary,

Ah ok, so no to the EF86's then, i already have a U67 which uses them so would defo like to have something which gets as close as possible to the U47 sound.
Which tubes do you use in max's MK47?
need to choose the right valve before i put together the psu.

regards

Spence.

 

[gary o]

need to choose the right valve before i put together the psu.

regards

Spence.
[/quote]
 
Dont let me put you off EF86 but I think thats what I read & I have never seen any U47 clones with ef86 but have a google around first tho ...... I get what your saying about different tubed mic to what you have, Im gonna have a mess with the U67 circuit soon Im currently doing a very quick experimental UM75 circuit uses a EF86 I should be testing it in a few hours

I use the 6028 tubes max modded the circuit for Philips brand I have..... I find the MK47 circuit a little noisier than my other tubes mics a slight hiss , I have read about this from other builders of U47 circuits, its not bad , Im thinking it maybe  the way the tube is biased I also read its to do with the 3meg resistor, I also read the V14 would have been a quieter tube.... as i say its not bad didnt notice till I A B my mic closely.....

 

[Spencerleehorton]

HI Gary,

Yeah the 6028 seems to be the one, but i am interested in any other ones that could work.
I am probably going to build two of these and have different parts in each to try and compare, for instance the paper in oil caps i have been told shouldn't have any difference in sound compared with the poly caps, but i want to test this out and listen to it myself.
I came across this:

http://www.saturn-sound.com/products/replacement%20valve.htm

but again its pretty expensive.

regards

Spence.

 

[gary o]

Sounds like great plan two mics.... ive tried many capacitors & other components I used sockets so I could plug in & out quickly then sing/record a line to my humble ears paper oil sound softer, nicer to me but thats me.... I love the fact that components change the sound buts its very subtle ...... you can even talk your ears into believing one is better than other maybe because of what you read..... in my humble experiments the capsule makes the a massive difference in sound, I always use same capsule in comparing mic circuits & so far Im finding the differences in mic circuits is quite small..... I have reached a conclusion for myself that the only way to get the real sound of a classic mic is to get the real capsule but I can still make a hell of a good mic cheaply also not having any real classic mics to compare to doesnt help or maybe it does haha.

I have dealt with Asley Styles from saturn sound what a lovely guy ...... interesting read about his valve .... for myself I think Im gonna get myself a Neumann K67 capsule do a U67 as EF86s still about I think its the closest I can get to a real classic mic,as just trannsformer wouldnt be  fully authentic.

 

[Pip]

Look at this.

http://www.tab-funkenwerk.com/id68.html

 

[Spencerleehorton]

hi guys,

so far in the search for what tube to use for the U47 the EF80 is apparently a little nosier than a EF800 so will try this route i think.
unless anyone has any other info?

regards

Spence.

 

[gary o]

Is Pips link the schematic your using Spence ......

http://www.tab-funkenwerk.com/id71.html I threw this together last night to compare to M49 with 6AK5 & Ela with 6072 & a U87 without de emphassis used same Haufe T14/1 & same Violet capsule in lollypop head & again they sound quite simillar I guess there are differences but really small not sure if T14/1 is best match for each circuit but they all sound good the U87 circuit is the most different less 3D smoother or you could say duller but may work better in mix ( I only tested vocals by the way same singer & song for each me) this was very un scientific test but fun Im gonna build U67 circuit now without the feedback as I dont have a K67 capsule yet or the BV12.

Very interested to see how you get on Spence..... I keep thinking about getting a M7 for my MK47,

 

[kidvybes]

hi guys,

so far in the search for what tube to use for the U47 the EF80 is apparently a little nosier than a EF800 so will try this route i think.
unless anyone has any other info?

regards

Spence.

...for what it's worth, Dave Pearlman ships his TM-1 (which is known to be in the 47-ish family) with an NOS Siemens EF80 tube...I have swapped with a Telefunken EF800, with minimal sonic difference...in his circuit at least, noise is not a discernible issue with either tube...I am staying with the EF800 for now...I know Oliver Archut is very fond the EF800 for microphone use...I believe he recommended it to Miktek to be used in combination with his BV-8 transformer in their CV4 microphone...

...another good pentode tube for mic use is the E80F (military grade EF86) but it has a longer glass tube (see my avatar), so you must have the necessary clearance for proper fitment...Oliver recommended that tube as an alternate for the EF86/EF806s:
http://www.neumann.com/forums/view.php?site=neumann&bn=neumann_archive&key=1015290588

 

[Spencerleehorton]

Hi,

just wanted to make sure but on here:

http://www.tab-funkenwerk.com/id68.html

its says 105v and 5.05v for heater using EF80 and EF800 tube?

shouldnt this be a much higher B+ voltage? 160v? and the heater to be 6.3v on the EF80?
but the EF800 i think uses 5.05v on the heater?

regards

Spence.

 

[Spencerleehorton]

HI all,

I have managed to source a EF80 and i will build the Gyraf G7 psu to get 160v B+ and 6.3v heater.
I have all 1/4 watt resistors and have space prototype body to go into (exhaust pipe made mic body!!)
I will knock this up next week and see how it sounds by using mainly point to point.

regards

Spence.

 

[gary o]

hi spence I think you will need 105 volts  .... HT & 5.05V for heater..... I think the underhaeting of the tube is to do with impedence & also lowers noise a little

 

[Spencerleehorton]

HI Gary o,

to my knowledge valves dont like underheating, so i'll start with 6.3v as thats what the doctor ordered for the EF80.


regards

Spence.

 

[Pip]

As to the underheating issue. Sorry valves do so like underheating but it varies valve to valve. They actually will last longer if properly implemented. There is gobs of info on underheating on the web so won't get into it here. It also changes the way a tube responds (sounds). Remember in most of these circuits the valve is not amplifying much mereley impedance converting. As to the power supply issue I believe you want 105VDC at the outout when the mic is hooked up which probably is around 150-160VDC range with no load present.

There is a reason why Oliver has chosen the EF80 EF800 tubes. They are the next in line in the evolution of the EF14 tube.

See this:

http://groupdiy.com/index.php?topic=50694.msg664163#msg664163