MASTER VOLUME FOR EACH PAIR

[rzenc]

I have been thinking about mixing power tubes, i.e. 6V6 and EL84's, into the same O.T.
O.T. specs:
4000 ohms plate to plate
rated @ 50W
secondaries 0 - 4 - 8 - 16
freq 30Hz - 33KHz

P.T. H.T. is 280 - 0 - 280 which would yield around 392VDC with SS rectos and less with tube rectos...5VAC for tube recto capable of 4A's so I can play with different tube rectos...
It will be cathode biased, each pair sharing it's own resistor and capacitor, i.e. resistor + cap for 6V6's and resistor + cap for EL84's.

However my main concern is whether the arragement I draw will work as supposed, so that I can turn each pair as desired.

Have you tried using something similar? what were your impressions? worth the trouble? Any other ideas of implementing this concept?

Thanks in advance
Best Regards

Rzenc

[tubenit]

394v exceeds the max rating for EL84 plates that are cathode biased by maybe 40 volts. You can use that type of voltage if fixed biased like Physconoodler does.

With respect, Tubenit

[rzenc]

394v exceeds the max rating for EL84 plates that are cathode biased by maybe 40 volts. You can use that type of voltage if fixed biased like Physconoodler does.

With respect, Tubenit

So...how about a switch to change from SS to tube recto + fixed bias to cathode bias?

The initial plan was to use this iron to build an AC30 type... but I changed my mind about it...

Thanks for the input!

Best Regards

[kagliostro]

Hi rzenc

I'm a novice so I'm not able to understand your PPIMV schematic

can you give me explanations about ?

also I was thinking to an amp with mix of EL84 and 6V6

here my amp idea (not a definitive schematic)

http://www.mediafire.com/file/mymhnyngozy/AC30 Mix amp v1.01 .pdf

Kagliostro

[Geezer]

I've run EL84's @ 400v+ cathode bias (& many production amps do also) & they survive.

The problem (to me) is that @ those high voltages, the tone suffers.....they become brittle & harsh to my ears.

$.02

G

[kagliostro]

Weber in the dc30 amp (a Matchless - very close to a Vox) uses as PT their WPT30

which is rated to 560v CT and 600v CT (250mA)

the kit has an option for both voltages 560v / 600v and both fixed / cathode bias

http://taweber.powweb.com/store/6d30_schem.jpg

https://taweber.powweb.com/store/pt30sch.jpg

not SS rectifier switch but a 300v-0-300v option

and the use of a WOT45HHR transformer (I suppose in the 3800ohm option of use)

https://taweber.powweb.com/store/wot45sch.jpg

Weber is not Bible but their kits were build by a lot of people

Kagliostro

[rzenc]

I've run EL84's @ 400v+ cathode bias (& many production amps do also) & they survive.

The problem (to me) is that @ those high voltages, the tone suffers.....they become brittle & harsh to my ears.

$.02

G

Actually, the SS recto voltage was only a reference, I'm really willing to use a tube recto since I do not have any amp with this feature ... I sold both 5E3 that I built last year... and I also think the same, regarding 6V6, lower supply yielded a fatter sound... so maybe I will play with a double 5Y3...
Thanks for the insight!!!

can you give me explanations about ?

also I was thinking to an amp with mix of EL84 and 6V6

here my amp idea (not a definitive schematic)

http://www.mediafire.com/file/mymhnyngozy/AC30 Mix amp v1.01 .pdf

Kagliostro

The idea is to have independent, post P.I. master volumes to each set of output tubes, a pair of 6V6 and a pair of EL84's, one tube type per side of the O.T., each pair would share it's own cathode resistor and cap combo to proper bias the stage. I thought I could get away splitting the coupling caps on the P.I. and use them according. Maybe get advantage of tone shaping, since 6V6 are known to give fatter sounds - that's the reason behing 0.047uF as coupling caps to 6V6 grids - whilst 0.022uF to EL84, since they are known for their britter characteristics - and maybe going even further with this idea and use lower/bigger values of capacitance - although gotta take care with blocking distortion. Probably, the cathode bypass cap can be used to pursue such interest and it can be omitted by a switch of course.
And I was/am curious to know whether someone have tried it before and what were the results....

I am aware that 6V6 and EL84 has different needs of drive in order to develop full power and I can play with resistors, both grid stoppers and reference resistors to build potential dividers to accomodate their needs...

also I was thinking to an amp with mix of EL84 and 6V6

here my amp idea (not a definitive schematic)

http://www.mediafire.com/file/mymhnyngozy/AC30 Mix amp v1.01 .pdf

Kagliostro

Your link did not work, redirected thru may different pages...

Thanks for your interest,
I will keep you posted

Best Regards

Rzenc

[tubesornothing]

I dont see any issue with your dual PPIMV.  Give it a go.

As for high plate voltages on your EL84s.  Not a problem.  Marshal 20W does this, same with Dr Z Maz18  and  Dr Z Maz 36.  Tubes dont last as long, but it will be OK.  This is with JJ EL84 tubes BTW.

[rzenc]

This is with JJ EL84 tubes BTW.

This is eactly what I have hanging around... 2 quad's 

Have you tried the TAD EL84's????

I have had great success with their 6L6WGC - STR, 6L6GC STR RCA, 12AX7A.

I heard about Sovtek EL84M but have never heard it....

Thanks in Advance

Best Regards

Rzenc

[kagliostro]

Thanks for the infos

so, if I understand, you want to use a couple of assorted tubes

one side of the PP an EL84 and the other side a 6V6

instead of a PP of EL84 and a PP of 6V6 as in my project

the link is ok (I tested it 7 or 8 times)

when connected you must wait till appear => Click here to start download

then close the windows that opens and confirm open or save in the little window that appear

if you are not able to download the schematic post me a message in the forum with your e-mail address and I'll send it to your e-mail box directly

Kagliostro

[rzenc]

Kagliostro:

The link worked now!!!

And yes, it's the same concept, their will be a 6V6 and an EL84 on each side of the O.T., however, what is my concern is whether splitting the signal between the coupling caps could result in detrimental or something rather disgusting....and I would like to mix 6V6 and EL84 sounds to taste instead of having them at full volume all the time...

I will give this a try... let's see....

Still need to draw and drill  chassis and finish arranging things.... I will use Solen capacitors in the power supply and since they are really big it's making life a tad difficult to organize it's layout...not so sure about using a dog house... I would like to keep wiring as simple and direct as possible.

Rzenc

[rzenc]

According to PHILIPS and MULLARD EL84 data sheets, pins # 1, 6 and 8 are i.c. - internal connections - I would like to know if you use them as soldering tabs to keep things as close as possible to the tube socket. Can it wreck havoc something?

Thanks in Advance

Best Regards

Rzenc

[kagliostro]

As reference I used the Weber 6v30 (Vox AC30) schematic and the Mesa Boogie Blue Angel schematic

only I use 2 el84 instead of 4 el84 as in Blue angel

about splitting the signal as to have a PPIMV for each pair of tubes was an idea coming from HotBlueplates here in the forum

http://www.el34world.com/Forum/index.php?topic=8173.msg73188#msg73188

that way you can decide the level of each pair of tubes

so you can have all power in el84 and 6v6

or a little level in el84 and full in 6v6

or vice versa or whatever mix you like more

in my schematic I put also a bypass switch to have no interaction with the MV, if desired

Kagliostro

[rzenc]

about splitting the signal as to have a PPIMV for each pair of tubes was an idea coming from HotBlueplates here in the forum

http://www.el34world.com/Forum/index.php?topic=8173.msg73188#msg73188

that way you can decide the level of each pair of tubes

so you can have all power in el84 and 6v6

or a little level in el84 and full in 6v6

or vice versa or whatever mix you like more

in my schematic I put also a bypass switch to have no interaction with the MV, if desired

Kagliostro

I did not know that, although I should have thought about someone trying o make it....

I'm finishing the layout on acad and might be able to start drilling holes in about 2 or 3 weeks from now...

Many thanks

Best Regards

Rzenc

[PRR]

> pins # 1, 6 and 8 are i.c. - internal connections - I would like to know if you use them as soldering tabs

BAD idea.

> Can it wreck havoc something?

Yes.

"NC" is NO Connection, you may use this tab for anything.

"IC" Internal Connection means "this pin may be connected to something, and we won't tell you what!"

Many-many-many times, the "IC" pin is not actually connected to anything. But you need a bright light and good eyes to confirm this for every tube you want to put in the socket.

A 3-tag strip is $0.59. Do it right.

[kagliostro]

also there are differences between different brand

I investigated the problem and found that the Sovtek tube has NO CONNECTION to pin #1 (the "US" tubes had pins 1 and 2 connected internally)
It functioned as a mica support point and connected to nothing.

http://www.audiokarma.org/forums/showthread.php?t=108492

Kagliostro

[rzenc]

> pins # 1, 6 and 8 are i.c. - internal connections - I would like to know if you use them as soldering tabs

BAD idea.

> Can it wreck havoc something?

Yes.

"NC" is NO Connection, you may use this tab for anything.

"IC" Internal Connection means "this pin may be connected to something, and we won't tell you what!"

Many-many-many times, the "IC" pin is not actually connected to anything. But you need a bright light and good eyes to confirm this for every tube you want to put in the socket.

A 3-tag strip is $0.59. Do it right.

also there are differences between different brand

I investigated the problem and found that the Sovtek tube has NO CONNECTION to pin #1 (the "US" tubes had pins 1 and 2 connected internally)
It functioned as a mica support point and connected to nothing.

http://www.audiokarma.org/forums/showthread.php?t=108492

Kagliostro

I did read the link and it should be repeated as a mantra... I will never solder anything to I.C. tags

Almost ready to start drilling holes on chassis and circuit board... waiting for potentiometers and some resistors.

I will keep ya posted on the progress

Thanks

Best Regards

Rzenc