SDM SILVER JUBILEE
Moderators: pompeiisneaks, Colossal
SDM SILVER JUBILEE
While researching the Lerxst Omega amp in conjunction with my channel-switching Marshall investigation, I came across a layout of a Silver Jubilee drawn by SDM on the metro forum. Seems to be a well-respected amp guy, but I know nothing beyond a few forum posts.
Questions:
1) How would you rate this drawing? It could be the best in the world, I just have no idea myself.
2) How does the 2550 compare to the 2204? I've never played a 2550.
3) There is a "black box"-looking device just next to the bias supply on the board. Vas ist das?
4) Is there a schematic for this amp?
Thank you!
Questions:
1) How would you rate this drawing? It could be the best in the world, I just have no idea myself.
2) How does the 2550 compare to the 2204? I've never played a 2550.
3) There is a "black box"-looking device just next to the bias supply on the board. Vas ist das?
4) Is there a schematic for this amp?
Thank you!
Just plug it in, man.
Re: SDM SILVER JUBILEE
1. Looks nice. Is it accurate? No idea.
3. Bias trimmer pot
3. Bias trimmer pot
I build and repair tube amps. http://amps.monkeymatic.com
- martin manning
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Re: SDM SILVER JUBILEE
1) I would trust that drawing to be accurate much more than I would a Mojo drawing.
2) Google.
3) See above.
4) Google.
2) Google.
3) See above.
4) Google.
Re: SDM SILVER JUBILEE
Thanks, xtian! Makes sense, I've never seen one stand on its side like that. I found some Marshall 2550-5 schematics on EL34world. Might take some time to figure out. How reliable are the Ceriatone layouts?
Just plug it in, man.
- Colossal
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Re: SDM SILVER JUBILEE
All of the Metroamp and SDM drawings are of high quality.
5) what Martin said
6) see #5
5) what Martin said
6) see #5
Re: SDM SILVER JUBILEE
Here's a Marshall 2554 25/50 watt schematic. I see that Friedman puts his very-Metro-looking effects loop after his Master volume on his amps. Any problems moving the loop from the 2554's position? It is in between V2A and V2B.
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Just plug it in, man.
Re: SDM SILVER JUBILEE
Are 220K pots still available? I imagine you’d sub for 250k, but if you’re shooting for accuracy, where would one find those, audio and linear? Thanks.
Just plug it in, man.
Re: SDM SILVER JUBILEE
For sure. AES has three listed. Probably find them all over the net if you just look.
Re: SDM SILVER JUBILEE
Be sure to check the part tolerance/precision. You might want a 220k pot but end up with something significantly higher or lower than the nominal value, which can be maddening and wastefully expensive, meaning, you might need to buy a bunch of pots just to find the one that works for your application. Then what to do with all the losers?... Case in point, I wanted a 300k pot for a build and the two I ordered turned out to be 250k. Useless.
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Re: SDM SILVER JUBILEE
any reason not to use a larger pot (i seem to always have 1M on hand) and run a 220k resistor along the outer lugs?
that's what I've been doing so if there's a reason not to I'd like to know!
that's what I've been doing so if there's a reason not to I'd like to know!
PRR wrote: Plotting loadlines is only for the truly desperate, or terminally bored.
Re: SDM SILVER JUBILEE
You can, but the taper may or may not be ideal. But it's easy to measure the response with a DMM and plot the data in Excel. I did that to get my 300k pot.thetragichero wrote: ↑Tue Feb 18, 2020 3:43 am any reason not to use a larger pot (i seem to always have 1M on hand) and run a 220k resistor along the outer lugs?
that's what I've been doing so if there's a reason not to I'd like to know!
Re: SDM SILVER JUBILEE
A 1MA pot with "283K" across the outer lugs should get you closest to 220K. What about a 270K and a 10K in series? What taper issues have you noticed when doing that? How much better would that be over a 250K pot and calling it good?
Just plug it in, man.
Re: SDM SILVER JUBILEE
Right. At first I was searching for a CTS version, and I couldn't find any. AES seems to have quite a bit of everything, thanks for the recommendation. I've never used them.
Just plug it in, man.
Re: SDM SILVER JUBILEE
Please see OP for this question: What is the purpose of the two LEDs on the board? The two red ones just to the side of the relay on the board. ???
Just plug it in, man.
- pompeiisneaks
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Re: SDM SILVER JUBILEE
I believe the LED's are part of the diode clipping circuit. I'm not super strong on how it does it, but it gives some of the distortion.
~Phil
~Phil
tUber Nerd!