"70ies circuit Bludodrive"

[erwin_ve]

But there is so much guessing right now, because you never have seen such a thing.

Hi erwin_ve,

This is true. I had my own nose only in perhaps 25 Dumble amps and Dumblelators etc. The other perhaps 15 I know indeed only from gut pics.

Cheers,

Max

All EU based where you had a peek?

[Max]

But there is so much guessing right now, because you never have seen such a thing.

Hi erwin_ve,

This is true. I had my own nose only in perhaps 25 Dumble amps and Dumblelators etc. The other perhaps 15 I know indeed only from gut pics. And of course this is probably still less than 10% of all the Dumble amps, Dumblelators etc. Indeed no comfortable database for generalisations. In this I agree.

Cheers,

Max

All EU based where you had a peek?

Please understand that IMO an answer to this question is of no practical relevance at all.

All the best,

Max

[LPSGME]

I save portions of some posts relating to the 'funky OD' entrance and this appears to be what Brandon said:

That amp is the 70's style circuit, 100K slope, 100K/1k5 plate/cathodes, Funky OD entrance network.
Lance isn't using a loop , but he is plugged into the FET input.
5uf bypass caps all around, 100W amp w/1/2 power switch. JJ Pre's Tung-sol 6l6's
Brandon
_________________
What is funky OD?

220K/500pf to ground, 1.2M in series, 33k to ground

[erwin_ve]

All EU based?

Hi erwin_v,

Please understand that IMO an answer to this question is of no relevance at all.

All the best,

Max

Sure Max! Sorry for the derail. Just was a personal question. I won't ask it again...

[Max]

All EU based?

Hi erwin-v,

Please understand that IMO an answer to this question is of no practical relevance at all.

All the best,

Max

Sure Max! Sorry for the derail. Just was a personal question. I won't ask it again...

Hi erwin_v,

No problem at all!

Have a great day!

Max

[drew]

And IMO, please contradict, the pre-classic stack of a 3rd generation ODS is more similar to a skyline stack than to a '79 classic stack of a transition generation ODS.

Bob Simpson, you should make this your signature line. Remember to credit Max.

[Bob Simpson]

And IMO, please contradict, the pre-classic stack of a 3rd generation ODS is more similar to a skyline stack than to a '79 classic stack of a transition generation ODS.

Bob Simpson, you should make this your signature line. Remember to credit Max.

Thanks, Drew.

I think I prefer this one...

Bob Simpson

[Max]

And IMO, please contradict, the pre-classic stack of a 3rd generation ODS is more similar to a skyline stack than to a '79 classic stack of a transition generation ODS.

Bob Simpson, you should make this your signature line. Remember to credit Max.

Thanks, Drew.

I think I prefer this one...

Bob Simpson

Hi drew, Hi Bob,

Thanks for the compliments. Here is some more info concerning this:

3rd generation "pre-classic" tone stack:

Treble: 250K pot / 510pF treble cap
100k slope resistor
Mid: 250K pot / .01 mid cap
Bass: 1M pot / .1 bass cap / .005 soldered between the terminals 2 and 3 of the bass pot / 10K tail


"Skyline" tone stack:

Treble: 250K pot / 326pF treble cap http://ampgarage.com/forum/viewtopic.php?p=28213#28213
150K slope resistor
Mid: 250K pot /.01 mid cap
Bass: 500K pot / .1 bass cap / .001 soldered between terminals 1 and 3 of the bass pot / 10K tail


Transition generation "classic" tone stack:

Treble: 250K pot / 330pF treble cap
100K or 150K slope resistor
Mid: 100K pot / .05 mid cap
Bass: 250K pot /.1 bass cap / no capacitor soldered to the terminals of the bass pot / 1.8K tail

Hope this helps,

Max

[wjdunham]

What's the knob next to the footswitch jack on the back - looks like the FET gain control from the coax cables running to it? Otherwise fascinating discussion.
Bill

[Structo]

What effect do the caps that HAD puts on the bass pot have?
Like in the earlier generation (#13) with the .02uF and .0022uF?

Then when he went to the Skyline stack, the .001uF on the bass pot to ground.
Also what purpose does the 10K resistor have?

[boldaslove6789]

What's the knob next to the footswitch jack on the back - looks like the FET gain control from the coax cables running to it? Otherwise fascinating discussion.
Bill

The FET is on a relay- you can see it on the board...I believe funk puts them on all his 70's style builds.

You'll notice in the picture there are three ftsw's, one for PAB, one for OD, and one for FET.

http://www.thegearpage.net/board/showth ... p?t=774643

[David Root]

On a more prosaic note, the iron looks like a Twin PT, Heyboer Twin choke and Marshall 100W OT.

Could be a custom OT I suppose but Funk has said he likes Marshall OTs in 100W ODS.

[Max]

What effect do the caps that HAD puts on the bass pot have?
Like in the earlier generation (#13) with the .02uF and .0022uF?

Then when he went to the Skyline stack, the .001uF on the bass pot to ground.
Also what purpose does the 10K resistor have?

Hi Tom,

Here is an article about these James networks (also known as the passive Baxandall tone control) which you find in the 2nd and 3rd generation (3rd only in "jazz" mode) "pre-classic" ODS amps: http://schmarder.com/radios/tech/tone.htm

Here you find an explanation of the functions of pots, resistors and capacitors in such a kind of James / passive Baxandall tone control. By using one of the tone stack calculators (some of them you can download for free – just do a google search) you can visualize the effects of different values and configurations on the tone shaping. Here is one of these calculators with a "James" option: http://www.duncanamps.com/tsc/

Here again the ODS tone stacks from 1st generation to 5th generation. Please understand the year dates in the sense of "around":

1st generation "pre-classic" tone stack (1972 – 1975):

I am not 100% sure about this because at least my personal database is too small for any generalisation concerning the 1st generation tone stack. There are only perhaps around 10 of these in existence anyway, and many of these have been modified by Alexander at some point, most often to a 1979 - 1988 "classic" tone stack AFAIK.


2nd generation "pre-classic" tone stack (1975 – 1978):

Treble: 500KL pot / 510pF treble cap
100k slope resistor
Mid: 250KA pot / .01 mid cap
Bass: 1MA pot / .1 bass cap / .002 soldered between the terminals 2 and 3 of the bass pot and .02 cap soldered between terminals 1 and 2 of the bass pot / 10K tail


3rd generation "pre-classic" tone stack (1978 – 1979):

Treble: 250KA / 510pF treble cap
100k slope resistor
Mid: 250KA / .01 mid cap
Bass: 1 MA / .1 bass cap / .005 soldered between the terminals 2 and 3 of the bass pot / 10K tail


Transition generation and 4th generation "classic" tone stack (1979 – 1988):

Treble: 250KL / 330 treble cap
100K or 150K slope
Mid: 100KA / .05 mid cap
Bass: 250KL /.1 bass cap / no capacitor soldered to the bass pot terminals / tail resistor values between 1K and 2K, 1.8K being a typical value


5th generation "skyline" tone stack (starting around 1988):

Treble: 250KL / 326pF treble cap http://ampgarage.com/forum/viewtopic.php?p=28213#28213
150K slope resistor
Mid: 250KA /.01 mid cap
Bass: 500KA / .1 bass cap / .001 soldered between terminals 1 and 3 of the bass pot / 10K tail

With some simplification you could IMO perhaps look upon the "skyline" tone stack as some kind of "back to the roots" move into the direction of the "pre-classic" tone stacks.

The 1979 – 1988 "classic" tone stack you could perhaps look upon IMO with some simplification as a bit more of a "Fender kind" than the 1972 – 1979 "pre-classic" and the post 1988 "skyline" tone stacks. This a bit more "fendery" style of the 1979 - 1988 "classic" tone stack may perhaps be the reason why Alexander called this kind of tone stack the "classic". But this is only a guess of course.

Cheers,

Max

[Max]

1st generation "pre-classic" ODS pictures

[Max]

2nd generation "pre-classic" ODS pictures