Ultraphonix adventure

[bepone]

to answer the question 22k instead of 10k makes PI more balanced and clean, and we dont want it here

[neskor]

to answer the question 22k instead of 10k makes PI more balanced and clean, and we dont want it here

Thanks!

[martin manning]

I can see that PI tail resistor is 22K.
Marshall and the rest are using 10K on that position.

The larger tail resistance will have better balance, but it will use more of the available supply voltage and therefore reduce headroom.

[bepone]

amp is completed finally! now i need to find some long stick to power it on

UP4a.jpg

working still on cab yet, tolex etc.. this will not be finished so soon

[bepone]

the brass board behind pots also was dissasebled and fully cleaned

UP4b.jpg

[Reeltarded]

My board replacement is staked and all the parts are arranged. 428v PT and 3k4 OT. Going to rebuild and finish this monster with the schematic PI and see if I like it.

[rootz]

Such a cool amp Bepone! I had loads of fun with this circuit, even though the Marshall flavour isn't really my thing anymore.
Care to share why you did not go channel switching with this amp?

[bepone]

thx, because of simplicity, and following the original!
here on the left is JCM800 / Dumble channel , on the right is basic Fender, you can choose any input which you like,

external A/B switching is possible too

[dorrisant]

I just acquired a '68 drip edge Bassman AB165.

The sickness continues...

[Synchu]

Will be following up this rather addictive thread/trend

I would so love to have the opportunity to get some old tube amps where I am, instead of the all sorts of weird 80s solid state rubbish that is on the local market all the time.

Niki

[bepone]

I just acquired a '68 drip edge Bassman AB165.
The sickness continues...

..impossible..

[bepone]

This schumacher OT is just fantastic, perfect results guaranteed!

[bepone]

Amp started, but with problems , this time unique problems!


Heavy oscilattion in the gain channel, when gain pot is on 4/10, or 10h! And it is low frequency! Too strange.

Problem located in V1 tube, pulled all the others out, V1b is oscillating! If i disconnect V1b, V1a is working normally, gain is possible to the max,
if V1b is ON too, then also V1a is starting with osc!
Probably this coax to V1b is passing below V1a anode res, ill move it somewhere

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[sluckey]

Are you sure that's not a scope/probe grounding issue?

[bepone]

yes cause it happens when you are rotating gain pot up..

p.s. just fixed - with resoldering all the tube socket pins (!! ) and all the elements around V1..
sad because it is sign of bad socket (s) - maybe i need to change them too (i wanted to avoid that)