jdel77
Well-known member
FourT6and2":304a4kb0 said:Still waiting on transformers so I decided to just get started on the turret board.
And some resistor porn lol. I wen to the Container Store and found some awesome containers, y'all. I got way more excited in there than I should have. I feel like I can really relate to Monica, from the show Friends...
That is incredibly clean work.
FourT6and2
Well-known member
More progress. I discovered I'm missing the V1a plate resistor! The value is pretty obscure and I could only find it in a different brand. My OCD alarm is gonna go off because it won't match the others lol.
scottosan
Well-known member
What brand are the red resistors?
FourT6and2
Well-known member
PRP
A
Alex_S
Active member
FourT6and2":30dcocql said:
You don't need any course anymore. All that I can see on the photos is perfectly executed. You seldomly see that on the internet. Great job!
FourT6and2
Well-known member
Alex_S":1v960xv1 said:
Thank you!
M
marcus262
Member
May I ask what changes have you made to values of components that go from input till the end of tonestack,
compared to Chupa, like slope resistor, v1a resistor, cathode caps and resistors?
Here is the preamp for Yeti, which is quite similar in component values, if you need reference points
and don't mind sharing your tweaks.
compared to Chupa, like slope resistor, v1a resistor, cathode caps and resistors?
Here is the preamp for Yeti, which is quite similar in component values, if you need reference points
and don't mind sharing your tweaks.
Attachments
CrazyNutz
Well-known member
Dual bias supply, Interesting.
FourT6and2
Well-known member
CrazyNutz":79g50378 said:
I love dual bias for a 50-watter. The 100s have individual bias per tube. No more having to pay for matches tubes! I feel like dual bias should be standard in every Marshall style amp.
CrazyNutz
Well-known member
FourT6and2":3ltyvk5m said:
Yeah I hear ya. I have a rm100 that has a bias per tube, the thing I like most about it is I can take older tube quad sets that have drifted from being matched and still use them in my rm100 just fine.
Can also mix different types, el34's with 6l6's, or kt88's etc.
I've just never seen it on a 50w.
Jayy
New member
I love what you are doing with this! That is beautiful, clean work. I'm looking forward to seeing where you go with this and hearing the end result. Thanks for sharing this!
FourT6and2
Well-known member
CrazyNutz":1oxemivz said:
Ceriatone does it on all their amps, I think? At least most of the Marshall-style ones. I think it's an elegant arrangement.
EDIT:
Took a look and nope, I only see it in the Chupa and Yeti. I always thought it was something they added to more amps. But yeah, I like it either way lol. Here's a 100-watter:
amp_2 by lin ceriatone, on Flickr
FourT6and2
Well-known member
marcus262":2xafmccx said:May I ask what changes have you made to values of components that go from input till the end of tonestack,
compared to Chupa, like slope resistor, v1a resistor, cathode caps and resistors?
Here is the preamp for Yeti, which is quite similar in component values, if you need reference points
and don't mind sharing your tweaks.
V1a and V1b cathode bypass resistors have been raised from stock Chupa values. V1a plate resistor is lower. Treble peaking cap is slightly lower. Treble cap is slightly lower. I've added another bypass cap on V1b as you can see in the photos. PI output coupling caps have been lowered in value. PI grid leak resistors have been raised from stock Chupa values. And finally, I'll play with the B+ dropping resistor off-board to fine-tune the preamp voltages.
rottingcorpse
Well-known member
Glorious frapping thread. So jelly of your skills.
SpiderWars
Well-known member
I may have missed it; are you elevating the heaters or DC or anything?
FourT6and2
Well-known member
SpiderWars":3g3j9zcr said:
I was contemplating DC elevation, but the setup as Ceriatone does it, includes regulated DC. Seems to work fine in my Chupa. I posed the question on some other forums and people typically look down upon DC heaters for some reason. The response I got was basically, "it can make the amp sound bad." But nobody would provide any real information or evidence as to how or why.
Elevating the heaters is certainly less complicated than DC. I hate doing heater wiring and DC elevation means I only need to run one string of leads. Whereas with DC I have to run two separate strings (one for V1/V2 and another for V3/V4/V5). But I dunno. I haven't made a final decision yet. The hiccup with elevation is I can't really set it up until after the amp is built. Because you need to know what the actual B+ and preamp cathode voltages are to calculate the appropriate voltage divider.
SpiderWars
Well-known member
FWIW, my 50w has ~430vdc B+ and uses 1M from the screen node and 100k to ground. My mini-Major taps from the ~490vdc PI node (cuz there is no screen node) and uses 1M with 82k to ground. Both are between 35-40v.
FourT6and2
Well-known member
SpiderWars":34frc8is said:
Yeah, that sounds about right. But it depends on the cathode voltages on V1 and V2 as well. You need to elevate the heaters such that their negative swing is above the highest cathode voltage in the preamp. Without knowing that it's a bit futile.
It's typically around 35-40v. But I'd like to be sure. If you're off by 1-3v too low, then you haven't actually elevated the heaters all the way.
FourT6and2
Well-known member
Choke arrived today aaaaaaaaand they sent the wrong one.