Commodore 64
Well-known member
Are all your resistors Carbon Comp?
Guess what I'm building....
- Thread starter duhvoodooman
- Start date
ZMAN
Well-known member
- Joined
- Feb 27, 2008
- Messages
- 2,046
- Reaction score
- 0
- City & State/Province
- North of the Equator: I am a Southerner, Southern
Looks very exciting. I may have missed something but what type of amp will it be? I really only have Fender or Marshall as reference points. Will it be a head or a combo?
I guess this is what they refer to as "point to point" wiring?
After having a couple of situations arise lately where some soldering experince would come in handy I feel I should look into a decent iron kit.
I guess this is what they refer to as "point to point" wiring?
After having a couple of situations arise lately where some soldering experince would come in handy I feel I should look into a decent iron kit.
duhvoodooman
Addicted to solder....
Most, but not all. There are a couple of metal oxides and ceramic wire-wounds in the high DC voltage portions of the circuit, one metal film across a couple of the pins of V2, and the four 68K input resistors are carbon films. But the rest of the resistors in the signal path are all carbon composite. I assume they were chosen for "historical accuracy" to the original Marshall 18W circuit. Personally, I would have chosen metal film for their tighter tolerance and reduced thermal noise, but then there's a whole crowd who extol the "warmth & mojo" of carbon comps and deride the "sterility & lack of character" of metal films. Personally, I think it's BS, but "opinions vary", as they say....
It's a Marshall 18W clone, and will be a head. Two channels, Normal and TMB (treble-mid-bass), with one high and one low input jack on each channel. I bought the kit in December 2009 (yeah, you read that right....) from Trinity Amps in Ontario and finally got around to building it. Yes, this is point-to-point wiring, using a turret board.
Commodore 64
Well-known member
Yeah, the most plausible thing I can figure from reading the intarweb is that carbon comps can distort in the 2nd harmonic when there's a high voltage across them (which may be construed by some as "warmth or mojo"). So, in the signal path with high voltage (plate resistors) would be a good spot.
Tig
Valar Morghulis
Ch0jin
Well-known member
Why not meet half way and use Carbon Film
Given the propensity for variation in sound between different tubes, I'd not be losing too much sleep over the choice of resistors, and I'm quite sure you aren't either 
(I ordered Carbon Films for mine. We'll see how they go when they arrive)
Looking good though DVM! What kind of speaker cab are you planning on running it into?
bcdon
Displaced Texan
This quest for 'historical accuracy' in amps brought to mind a quote from Randall Smith, founder/designer at Mesa Engineering.
duhvoodooman
Addicted to solder....
DONE!! Finished it up last night. Fired up perfectly first time. Sounds great--LOUD!! More on that later, but here are the latest batch of photos (don't have final lead dress done w/ wire ties, so don't gig me on that!):
Tig
Valar Morghulis
Wow, that looks top notch!
:applause
:applause
Commodore 64
Well-known member
It really does. Very nice. I'm amazed how fast it went together (once you got started ).
).
bcdon
Displaced Texan
Well done. That looks so nice. What I find so amazing is that such a simple circuit made from discrete components can do so much and produce such art. Bravo! :dude
duhvoodooman
Addicted to solder....
I have a Drive ported 2x12 cabinet that I loaded with an Eminence Red Coat Wizard and a WGS Green Beret (Greenback clone). The cab has a definite British edge to it, so should match up well.
Katastrophe
Well-known member
Beautiful, clean work you did there, DVM! Congrats on completing the project!
Monkus
Well-known member
Looks flawless DVM, great job....clips?
duhvoodooman
Addicted to solder....
Last couple of photos--mounted in the head cabinet, which I also bought from Trinity. Was in a blond mood that day:
duhvoodooman
Addicted to solder....
This amph will most definitely give you screaming solos. Particularly on the high input to the TMB channel, with the gain cranked up around 8.
I will try to post a clip. Hopefully, it will take me somewhat less time to do so than it did to get started on this amp....er, amph.
marnold
Reverend Rawk
- Joined
- Oct 15, 2005
- Messages
- 7,152
- Reaction score
- 25
Considering the length of the build time, could this now technically qualify as a "vintage" amp . . . ??oke
Seriously nice build there, DVM - just as I'd expect. Cheers.
Well, DVM himself qualifies as "vintage" so . . . *ducks*
Good to hear from you again, Nelskie!
duhvoodooman
Addicted to solder....
To both comments, I respond with the words of former Vice-President Spiro T. Agnew: "Nolo contendere"
Good to see you here, Jon!
ZMAN
Well-known member
- Joined
- Feb 27, 2008
- Messages
- 2,046
- Reaction score
- 0
- City & State/Province
- North of the Equator: I am a Southerner, Southern
Absolutely stunning!
Last couple of photos--mounted in the head cabinet, which I also bought from Trinity. Was in a blond mood that day:
ZMAN
Well-known member
- Joined
- Feb 27, 2008
- Messages
- 2,046
- Reaction score
- 0
- City & State/Province
- North of the Equator: I am a Southerner, Southern
If you don't mind me asking what tubes did you use. The recommended " The Tube Store" on the Trinity Web site is just down the road from me. I have bought several tubes from the. I am one of the few people who have used there walk up sales desk.
duhvoodooman
Addicted to solder....
The EZ81 rectifier came from our own Tunghaichuan (tip-o-the-hat....a very generous guy!), but the rest are JJ's from Eurotubes.com. Bob & the gang do a great job over there--super service and excellent pricing. And I've had good luck with JJ tubes.
otaypanky
playin' from the heart
- Joined
- Jun 29, 2009
- Messages
- 926
- Reaction score
- 0
- City & State/Province
- Mechanicsburg, Pennsylvania, U.S.A.
Sweet build DVM
duhvoodooman
Addicted to solder....
UPDATE 2/29/12:
To tame the output volume while maintaining the nice Marshall crunch, I bought a voltage reduction module (VRM) kit from Trinity Amps and installed it. These units install on the DC rail of the amp and let you drop the DC voltage while the AC filament heater voltage remains unaffected. They have the reputation of doing a great job of reducing the output volume without a significant amount of tone loss, which is a common complaint with external attenuators. For a cathode-biased amp like this 18W, it's a very straightforward installation, and it works exactly as advertised. I can dial down the DC voltage enough to run the preamp gain up all the way and the master volume high enough to get some nice power tube saturation, and still keep the volume to a non-lethal level! Pretty slick little modification!
Couple of photos below. The VRM consists of a MOSFET mounted against the chassis (with an insulator pad in between) to facilitate heat dissipation, a small PCB with a handful of components, and a 1M pot to control the DC voltage output. It's wired in between the standby switch and the first filter cap, and I have the control pot mounted through the back of the chassis, between the mains connector and the output impedance selector switch. The Trinity kit also came with a couple of DC blocking caps for the inputs to the first preamp tube, in case you find that the volume pot(s) on your guitar pick up some scratchiness. This can happen due to a very small amount of low voltage DC current getting back to the guitar controls through the input jacks when the voltage is cranked way down, but I haven't had to install those on mine.
To tame the output volume while maintaining the nice Marshall crunch, I bought a voltage reduction module (VRM) kit from Trinity Amps and installed it. These units install on the DC rail of the amp and let you drop the DC voltage while the AC filament heater voltage remains unaffected. They have the reputation of doing a great job of reducing the output volume without a significant amount of tone loss, which is a common complaint with external attenuators. For a cathode-biased amp like this 18W, it's a very straightforward installation, and it works exactly as advertised. I can dial down the DC voltage enough to run the preamp gain up all the way and the master volume high enough to get some nice power tube saturation, and still keep the volume to a non-lethal level! Pretty slick little modification!
Couple of photos below. The VRM consists of a MOSFET mounted against the chassis (with an insulator pad in between) to facilitate heat dissipation, a small PCB with a handful of components, and a 1M pot to control the DC voltage output. It's wired in between the standby switch and the first filter cap, and I have the control pot mounted through the back of the chassis, between the mains connector and the output impedance selector switch. The Trinity kit also came with a couple of DC blocking caps for the inputs to the first preamp tube, in case you find that the volume pot(s) on your guitar pick up some scratchiness. This can happen due to a very small amount of low voltage DC current getting back to the guitar controls through the input jacks when the voltage is cranked way down, but I haven't had to install those on mine.
Ch0jin
Well-known member
Nice one. Am I right in thinking this amp doesn't have a master volume hence the need for the VRM? I considered a similar approach for my JTM45 project, but instead went for a Lar/Mar style MV setup. Hopefully that works!
duhvoodooman
Addicted to solder....
Yes and no. The Normal (low gain) channel is non-master volume, but the TMB (high gain) channel has Gain (preamp) and Master Volume controls. The problem is that it's one of those MV controls where it goes from silent to ear-bleeding loud between 0 and 2. So the VRM actually lets me dial the MV control up far enough to get some power tube saturation before it's so loud that my brains start leaking out of the holes in my head....
Similar threads
Latest posts
-
-
-
Gig Report: Amber & the Antidotes at Cypress & Grove Brewery, 5/29/26
- Latest: Brian Krashpad
-