Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: tonewood on February 06, 2011, 11:34:56 am

Title: 5879 & Tweed OD Lite II questions
Post by: tonewood on February 06, 2011, 11:34:56 am: I've never tried a pentode in a preamp and this looks fun!

Does anyone know of a 5879 data sheet with a mutual characteristics graph or transfer characteristics graph that has several screen voltage curves on it? Using Merlin's method, I would like to draw the anode characteristics at different screen voltages. An existing spreadsheet would be even better!

Questions about Tweed OD Lite - II
Caps in the pentode section:
180pf paralled with 270k, to pass highs to 5879?
250pf in series with 470k, to pass highs to ground?
.001 across Ra, to dump more highs?
Are these for stopping oscillations or tone shaping purposes?
What are the calcs for these?

Has anyone tried this with an SE 6V6? Do you think it would be OK w/ se 6V6?
I'm trying to attach a .gif of the pentode section I'm referring to but can't see it in the preview.

Thanks!
Title: Re: 5879 & Tweed OD Lite II questions
Post by: kagliostro on February 06, 2011, 12:00:47 pm: Look here

http://tdsl.duncanamps.com/show.php?des=5879

Kagliostro
Title: Re: 5879 & Tweed OD Lite II questions
Post by: tonewood on February 06, 2011, 12:26:18 pm: Quote from: kagliostro on February 06, 2011, 12:00:47 pm
Look here

http://tdsl.duncanamps.com/show.php?des=5879

Kagliostro

Thanks for the reply Kagliostro. Yesterday I looked through what I believe is every one of the data sheets at that link & didn't find it. I may be calling the graph by the wrong name. What I am looking for looks like the sixth page of this data sheet:
http://www.guitaramplifierblueprinting.com/files/PhilipsEF86.pdf
But I want it for the 5879.

Thanks again.
Title: Re: 5879 & Tweed OD Lite II questions
Post by: tubenit on February 06, 2011, 01:06:34 pm: Quote
Questions about Tweed OD Lite - II
Caps in the pentode section:
180pf paralled with 270k, to pass highs to 5879?
250pf in series with 470k, to pass highs to ground?
.001 across Ra, to dump more highs?
Are these for stopping oscillations or tone shaping purposes?

Correct & yes to stop oscillation and tone shaping.

With respect, Tubenit
Title: Re: 5879 & Tweed OD Lite II questions
Post by: kagliostro on February 06, 2011, 01:10:36 pm: isn't this ?

http://tdsl.duncanamps.com/sheets/5879/5879-g2.gif

http://frank.pocnet.net/sheets/127/5/5879.pdf

Kagliostro
Title: Re: 5879 & Tweed OD Lite II questions
Post by: tonewood on February 06, 2011, 02:47:30 pm: Quote from: kagliostro on February 06, 2011, 01:10:36 pm
isn't this ?

http://tdsl.duncanamps.com/sheets/5879/5879-g2.gif

http://frank.pocnet.net/sheets/127/5/5879.pdf

Kagliostro

No,
This is the Static anode characteristic graph:
http://tdsl.duncanamps.com/sheets/5879/5879-g2.gif
I'm looking for mutual characteristics graph aka transfer characteristics graph that has several screen voltage curves like the one on the 6th page (not 7th page) here:

http://www.guitaramplifierblueprinting.com/files/PhilipsEF86.pdf

Thanks again.
Tubenit, thanks for your info also.
I appreciate you guys taking the time to respond.
Title: Re: 5879 & Tweed OD Lite II questions
Post by: kagliostro on February 06, 2011, 03:59:26 pm: No, I'm looking for mutual characteristics graph

Ah, I see .... sorry I'm not able to find a data sheet with those curves

Kagliostro
Title: Re: 5879 & Tweed OD Lite II questions
Post by: tubenit on February 06, 2011, 06:34:29 pm: Layout to go with the schematic. Compare them and check for errors.

With respect, Tubenit
Title: Re: 5879 & Tweed OD Lite II questions
Post by: tonewood on February 06, 2011, 07:55:02 pm: Quote from: tubenit on February 06, 2011, 06:34:29 pm
Layout to go with the schematic. Compare them and check for errors.

With respect, Tubenit

Thanks!
Much neater than my current version is looking. Kalamazoo with the trem ckt replaced by 5879. Getting kinda ugly.
Title: Re: 5879 & Tweed OD Lite II questions
Post by: kagliostro on February 08, 2011, 01:08:55 pm: Hi Tubenit

great contribution yours

Quote
Compare them and check for errors

there are some differences because in the layout there is a different arrangement with respect to the schematic (in the schematic there is a SPDT switch but also a DPDT switch)

other differences are about some resistors here and there (one is cathode resistor of V1) and cap values (about this I would like to know which are the values for resistors and caps that Tubenit prefer)

the resistor connected between volume and pin 7 in V1 is 27k in the schematic and 220k + .001 in the layout

One cap is missing, the 47pf cap between pin 3 and pin 1 in V1

I would like to build one of this very interesting pre as a stand alone unit, at the moment I've some ef86 but, at ham fest, till now, wasn't able to find a 5879 tube, hope to find it next time

Kagliostro
Title: Re: 5879 & Tweed OD Lite II questions
Post by: tubenit on February 08, 2011, 06:48:44 pm: Looks like there are numerous errors on the layout, so go by the schematic that was posted earlier in the thread. That looks correct to me. For example, it's 27k going into V1-7 not the 220k/.001.

With respect, Tubenit
Title: Re: 5879 & Tweed OD Lite II questions
Post by: tonewood on February 09, 2011, 12:37:14 pm: Quote from: kagliostro on February 08, 2011, 01:08:55 pm
I would like to build one of this very interesting pre as a stand alone unit, at the moment I've some ef86 but, at ham fest, till now, wasn't able to find a 5879 tube, hope to find it next time

Kagliostro

I really like the Idea of a stand alone. I'm hoping it sounds as good with an SE 6bq5 & 6v6 as is does with the PP amps. I'll let
you know how it is with the 6bq5.

Tubenit, thanks for the heads up on the layout.

Everyone-Thanks again for all the info.