3rd Generation ODS 50W

[talbany]

Here is a 3rd generation ODS 50W..

To avoid any confusion between the earlier 2nd generation I started a whole new thread to keep discussions seperate..
Although the revisions were made from the 2nd generation layout posted earlier they better reflect the evolution into the 3rd generation made around the 1978-1979 Ser# around 60-75..
Since these alterations occurred around a 2 year time frame and more than 1 or 2 amps and for the sake of accuracy should be referenced as 3rd generation ODS and shouldn't be looked upon as tweaks or custom voicing s for a certain customer..
Changes are listed on the top right of the layout are


1 Treble: 250KA treble pot

2..005 soldered between the wiper and top of the Bass pot

3.Black RG59/U 75 ohm foam - similar looking as the Tandy Wire RG59/U 75 ohm foam in ODS #094,(see below picture) but without the "Tandy Wire" label

Although this layout wasn't taken from an actual 3rd generation specimen perhaps I'll run across one here in the future..If so I'll make another separate layout better reflect the accuracy's of that amp (3rd Generation)

A 4th Generation is hopefully next time willing..

Max
If you would be so kind as to re-post those clips here of this 3rd generation for a sonic reference that would be wonderful..Thanks
Hope This Helps!!

Tony

[Bob-I]

I'm a little confused. There's a discrepancy between the pics and the layout. The layout shows a big filter cap by V1 and no LNFB, the pic shows LNFB but not filter.

Otherwise looks great, thx.

[talbany]

I'm a little confused. There's a discrepancy between the pics and the layout. The layout shows a big filter cap by V1 and no LNFB, the pic shows LNFB but not filter.

Otherwise looks great, thx.

Bob

The #094 pic was simply to illustrate the similarities in the type coax used that is all.. as described here in my above post.. Sorry if this confused you..

3.Black RG59/U 75 ohm foam - similar looking as the Tandy Wire RG59/U 75 ohm foam in ODS #094,(see below picture) but without the "Tandy Wire" label

Tony

[talbany]

One other thing I would like to make clear that 3rd generation amps replaced the slider switches with toggle's.. I thought about doing this however burning a couple hours to make a somewhat cosmetic change seemed silly..+ I am lazy..
now pass me the remote..

Tony

[stevlech]

Thanks again, sir. You are extraordinarily generous.

I have a question for you gurus: when did Alexander first incorporate the LNFB? Was it used in early # amps or did it appear in 3rd/4th generations?

Just pondering whilst staring at pics...

[talbany]

Thanks again, sir. You are extraordinarily generous.

I have a question for you gurus: when did Alexander first incorporate the LNFB? Was it used in early # amps or did it appear in 3rd/4th generations?

Just pondering whilst staring at pics...

LNFB V1B implimented 4th generation transition (Classic) from around #094
from around 79..Also used throughout 5th generation skyliners up to later HRM's where they were removed..
( This is not to say there were some exceptions like in the 183 case..)
Tony

[Bob-I]

Bob

The #094 pic was simply to illustrate the similarities in the type coax used that is all.. as described here in my above post.. Sorry if this confused you..

So apparently there were pretty big differences between actual amps in the same generation. The pictures DO seem a little short on filters, only one primaries, screens and one preamp, the layout seems better filtered/isolated.


EDIT: Nope I was wrong, I see the can cap now.
Again really great detailed work. I'm looking forward to the next generation, I have a set of xformers dieing to be one.

[talbany]

Bob

The #094 pic was simply to illustrate the similarities in the type coax used that is all.. as described here in my above post.. Sorry if this confused you..

So apparently there were pretty big differences between actual amps in the same generation. The pictures DO seem a little short on filters, only one primaries, screens and one preamp, the layout seems better filtered/isolated.


EDIT: Nope I was wrong, I see the can cap now.
Again really great detailed work. I'm looking forward to the next generation, I have a set of xformers dieing to be one. :wink:

Not to change the topic here AFAIK.. #094 is not in it's original condition.. Possibly started as out as a 4th generation classic later up-dated to high plate skyline specs (5th generation) as evidence by the KOA plates..I believe 124 also had such an upgrade..The 4th generation classics (later updated possibly should not be confused with my 3rd generation layout).. Just so others won't get confused!!
Hope this helps..

Tony

[Drumslinger]

Nice work Tony, thanks man.

[Max]

Thanks again, sir. You are extraordinarily generous.

I have a question for you gurus: when did Alexander first incorporate the LNFB? Was it used in early # amps or did it appear in 3rd/4th generations?

Just pondering whilst staring at pics...

Hi stevlech,

AFAIR Alexander did start to use the LNFB loop at V1b in the ODS amps with the release of the transition generation "classic" ODS in late 1979. #075, one of these transition generation "classic" amps has this already (as all the other transition generation / 4th generation "classic" features). If you look at this picture of #094, another transition generation "classic" ODS, you can clearly see the LNFB at V1b.

Cheers,

Max

[Max]

Bob

The #094 pic was simply to illustrate the similarities in the type coax used that is all.. as described here in my above post.. Sorry if this confused you..

So apparently there were pretty big differences between actual amps in the same generation.

Hi Bob-I,

No, this is not the case, the differences between all the 3rd generation "pre-classic" ODS I am familiar with are very minor.

Probably you did completely misunderstand Tony:

#094 on the gut pic is not a 3rd generation "pre-classic" ODS. Please read again what Tony posted here http://ampgarage.com/forum/viewtopic.ph ... 777#136777

After 2nd generation "pre-classic" comes 3rd generation "pre-classic" ODS from around #060 to around #075.

Then the transition generation "classic" ODS from around #075 to around #095

So #094 is a transition generation "classic" ODS and not a 3rd generation "pre-classic" ODS as you obviously assume.

And because #094 is a transition generation "classic" ODS, it has of course a completely different circuit than shown in Tony’s 3rd generation "pre-classic" ODS layout. Some examples:

3rd generation: "pre-classic" tonestack – transition generation #094: "classic" tone stack
3rd generation: "funky OD entrance" network – transition generation #094: "trigger" trim pot OD entrance
3rd generation: no snubbers – transition generation #094: snubbers
3rd generation: no LNFB at V1b – transition generation #094: LNFB at V1b
3rd generation: no ratio control – transition generation #094: ratio control
3rd generation: no dynamic balance control trim pot – transition generation #094: dynamic balance control trim pot
3rd generation: no "h. f. taper" trim pot – transition generation #094: "h. f. taper" trim pot

And as Tony IMO clearly wrote in his post, he posted this gut pic of #094 only to give a general impression how the RG59/U coax cables in his 3rd generation layout look like in real life because they look very similar to the Tandy Wire RG59/U, which Alexander used in the transition generation and 4th generation "classic" amps (#094 one of the "transition" amps - still without the full size presence control of the 4th generation amps).

Cheers,

Max

[Max]

Not to change the topic here AFAIK.. #094 is not in it's original condition.. Possibly started as out as a 4th generation classic later up-dated to high plate skyline specs (5th generation) as evidence by the KOA plates..I believe 124 also had such an upgrade..The 4th generation classics (later updated possibly should not be confused with my 3rd generation layout).. Just so others won't get confused!!

Hi Tony,

#094 is a transition generation "classic" ODS (no full size presence control yet). And I don’t see any hints for a later "skyline update" like in #124, which was indeed updated by Alexander from "classic" to "skyline" specs:

#094 has still the small orange "classic" 330pF treble cap ceramic disc on the board and no terminal 1 > 3 cap at the bass pot like the skyline amps. And all the "classic" ODS that later have been updated to skyline specs now have the white teflon coax, that was a part of the skyline update in all the updated amps I know. And #094 still has the RG59/U "Tandy Wire". So IMO #094 is still a "classic" amp without a skyline update. But these - in a transition generation "classic" ODS indeed unusual - blue resistors may be perhaps the result of another mod or repair than a skyline update.

Have a nice weekend,

Max

[stelligan]

Thanks for the layout, Tony!!

[stevlech]

Thank you all for the replys. It sounds like #75 represented a big change in Dumble's structure.

[talbany]

Not to change the topic here AFAIK.. #094 is not in it's original condition.. Possibly started as out as a 4th generation classic later up-dated to high plate skyline specs (5th generation) as evidence by the KOA plates..I believe 124 also had such an upgrade..The 4th generation classics (later updated possibly should not be confused with my 3rd generation layout).. Just so others won't get confused!!

Hi Tony,

#094 is a transition generation "classic" ODS (no full size presence control yet). And I don’t see any hints for a later "skyline update" like in #124, which was indeed updated by Alexander from "classic" to "skyline" specs:

#094 has still the small orange "classic" 330pF treble cap ceramic disc on the board and no terminal 1 > 3 cap at the bass pot like the skyline amps. And all the "classic" ODS that later have been updated to skyline specs now have the white teflon coax, that was a part of the skyline update in all the updated amps I know. And #094 still has the RG59/U "Tandy Wire". So IMO #094 is still a "classic" amp without a skyline update. But these - in a transition generation "classic" ODS indeed unusual - blue resistors may be perhaps the result of another mod or repair than a skyline update.

Have a nice weekend,

Max

Max thanks for the clarification..

Used this schematic posted here while back.. Obviously WRONG!!
Tony