Dumbleland Special 150w ser#009 Schematic

[didit]

If there is more to investigate I might open it up once again.
Voltages can be added then aswell.

Thanks! You don't need to open it up to measure the OT. You can feed signal into the speaker jack and measure across that and the output tube plate pins to get voltage ratio. The figure you have for the B+1 voltage is enough, really.

Note, if you measure the OT in place, use a low voltage at the speaker jack, you will be putting AC on the filters through the CT, so keep it low. I would use ~100 mV.

HaenZ, just to be clear, there is no risk of doing any damage here, the AC voltage appearing on the filter will be very very small.

A clearer photo of the stamped codes on the output transformer could potentially help with identifying the details.

..

[Guy77]

I did a search with the help of AI on the Output Transformers that Western Transformers Inc. made for the 4x 6550 Sunn amps and it looks like the Primary falls between 2.2 and 2.5k ohm CT

Here is what came out.
"
These bespoke Western Transformers Inc. Portland-wound output transformers for 4 × 6550 quads feature the following standard specifications: [1]
• Primary Impedance: 2.2 kΩ to 2.5 kΩ center-tapped (CT)
• Taps: 4, 8, and 16 Ω (with some versions also offering a 2 Ω or multiple UL screen taps)
• Power Rating: 120W to 150W continuous (capable of peak outputs up to 240W in strict musical instrument applications) "



Cheers
G

[didit]

I did a search with the help of AI on the Output Transformers that Western Transformers Inc. made for the 4x 6550 Sunn amps and it looks like the Primary falls between 2.2 and 2.5k ohm CT

Here is what came out.
"
These bespoke Western Transformers Inc. Portland-wound output transformers for 4 × 6550 quads feature the following standard specifications: [1]
• Primary Impedance: 2.2 kΩ to 2.5 kΩ center-tapped (CT)
• Taps: 4, 8, and 16 Ω (with some versions also offering a 2 Ω or multiple UL screen taps)
• Power Rating: 120W to 150W continuous (capable of peak outputs up to 240W in strict musical instrument applications) "



Cheers
G

Gemini helped confirm my guess ..

[HaenZ]

A clearer photo of the stamped codes on the output transformer could potentially help with identifying the details.

There are tons but obviously not a single one made it into the post
Ill fix it right away. Thanks for noticing!

[rccolgan]

I second that! It’s been a minute since we have seen new information of this quality. The CF driven PI is new to me too, and I don’t think I’ve ever seen that before. Seeing another implementation of the filters has been very enlightening too, and I think I understand HAD’s intent much better now, and my questions on the 002 hand drawn schematic have been largely cleared up.

is there anything that stands out as different between SSS #002 research the whole team did and anything that helps with this new insight from DLand #0011?

[martin manning]

is there anything that stands out as different between SSS #002 research the whole team did and anything that helps with this new insight from DLand #0011?

I'm referring to the step filters there. The big treble cut in one position of the 002's filters is repeated here x3, meaning there are three levels of it. That makes sense for a bass amp, but it was confusing in the context of the SSS. The other question I had was the relative amount of treble boost in the 002 filters. The same thing happens here, but to a lesser degree.

[rccolgan]

You guys might be interested in Dumbleland #011, schematic attached to this post.

Hey! I was going to reach out to the website to thank the tech for doing all this hard work but I think YOU might be the tech? If so, THANK YOU!!!!!

[Aaron]

You guys might be interested in Dumbleland #011, schematic attached to this post.

Wow! Thank you! The “Odyssey” style power amps amps have always been my preferred output. Thank you for confirming with this amp.

Aaron

[GAStan]

A clearer photo of the stamped codes on the output transformer could potentially help with identifying the details.

There are tons but obviously not a single one made it into the post
Ill fix it right away. Thanks for noticing!

First I too want to thank you for the work you put into this and for sharing it!!!

In one of the pictures I see the Triad inductor that is just before the filters. On it, the part# is clearly SP-117. However in the schematic it shows P-117 (missing the leading S).

[Max]

... A clearer photo of the stamped codes on the output transformer could potentially help with identifying the details.

OT.JPG

Max

[Roe]

... A clearer photo of the stamped codes on the output transformer could potentially help with identifying the details.

OT.JPG

Max

It seems that earlier 150w amps did not use the dynaco a451 but rather the sunn OT 1200s based on it with 120/150w 2k2 specs, which this custom OT could be based on?

For a recent take, see https://shop.piemme-elektra.it/Products/8339

[didit]

Hello --

The "cust no" "28-1312" has been identified in previous TAG commentary with SUNN 1200S transformer that is labeled "3-120T" on the OEM schematics. Using that number in our google search coughs up three prior posts explaining the background.

..