ODS #183 Build

[pfarrell]

Hi guys,

First post here. Most of my time has been spent over at TDPRI forum building Fender designs (5 amps so far in progressive states of increasing complexity) and DIYaudio.com building all manner of hifi equipment to make the vinyl sing. I know just enough at this point to know I don't know a thing, LOL. None of these builds were from kits—and the last couple have been entirely from scratch, trying to perfect my Tolexing skills. I have the same username in all places if anyone is project-curious.

I'm deviating from Fender at this point to see about this overdrive business (and my 11-yr-old daughter has been playing Primus)—and the ODS seems unavoidable due to the challenge—and potential sonic lushishness—and it's quite frankly mythic reputation bordering on religion. (I'm building a light wattage version of the JCM800 in the meantime as little snack while planning this ODS build.)

So, I bought the ODS board that @frusciante89 has produced... since coming from the HiFi experience—there are some advantages to PCBs—and well, it's different. Then I started thinking that it was a bit of a cop-out and I do like making eyelet boards...and well, then I found all the board layout pdfs from @martin manning and wow—that's a gift. Now I'm thinking that I will build up a #183 (I've wanted to build an amp with EL34s, only reason for choosing the #183) from scratch/schematic and then also use the PCB to build either the #102 or #124.... since I do want a wall of amps in my house—even though I've only been studying guitar myself for a little over a year—hooked for life I must say.

I'll probably have a lot of questions as I continue the process here... but my first question—maybe more of an opinion poll—is should I build as a head or combo (EVM12L)?
The Fenders I've made so far: 2x Champ, 5E3 combo, Princeton reverb head w/ 2x10 speaker cab, Vibroverb as head (using it into the 2x10) while currently building a 15" speaker cab for it since that's how it was originally offered as a combo. All these amps preserve the stock circuit while also having pretty significant mods—mostly additions that make the amps more versatile, different, interesting.

For some reason I'm leaning towards building it as a combo? Maybe that's so my daughter has easier access to taking it places....Even thought it appears that most of these amps were heads? IDK. I guess I'm wondering about the history and use—I don't have any desire to be overly specific with parts choices with regard to history, more just curious what everyone thinks. My head amp theory is really about being able to mess about with speakers since that's a big aspect, in my experience, of what one gets out of the amp.

I am struggling a tad to find iron for this build. For some reason I don't love love Hammond offerings...and Mercury is $$ (plus their documentation online is tragic)... but maybe this isn't really that important—I just have a bias in my head that I've picked up someplace regarding Hammond. The PCB layout from @frusciante89 references an Edcor that they no longer make—has a 12V winding in addition to the others...they will make you a trafo they don't otherwise carry—so that's cool—just takes a while—I'm looking into it. I have most of the other parts on order, probably missed some stuff—chassis is in the works—I'll design my own faceplates—I've cut some G-10 for all the boards (waiting on eyelets from Mouser, I'm used to turrets)—and I do have tubes, which I suppose is quite lucky given the world climate at the moment.

Anyway—preemptive thanks you dedicated people offering up here an insane amount of information and build help regarding these fine amps. So far it's been fun sleuthing out all the details...

[ijedouglas]

Chris Merren makes killer transformers for an EL-34 ODS. I have tried MM/Classictone/Pacific and to my ear it is not even a contest. Chris specializes in Marshall repros and is probably the best in the game.

http://www.merrenaudio.com/

OT: C1998
PT: T2562

I use either a vintage schumacher choke or a classictone if you can find one

[martin manning]

IMO, eyelet boards are the best and most authentic choice for a Dumble, and I think you'll find eyelets are easier to work with than turrets. As far as portability goes, a combo with an EVM12L probably weighs more than your daughter, and is awkward to carry.

[pfarrell]

Cool. Thanks guys. Sent an email to Merren... so, 1x12 cab? 2x12? Forgetting a bit about portability...what would be "normal"?
Definitely eyelets... ordered a selection from Mouser, I agree in this case eyelets look easier to work with...

[pfarrell]

Chris Merren makes killer transformers for an EL-34 ODS. I have tried MM/Classictone/Pacific and to my ear it is not even a contest. Chris specializes in Marshall repros and is probably the best in the game.

http://www.merrenaudio.com/

OT: C1998
PT: T2562

I use either a vintage schumacher choke or a classictone if you can find one

I haven't heard back from Merren about pricing/availability but I found both on their site... question though... the PT T2562 is listed as 150mA "quiescent load" and much higher bias winding (100V AC), but one of the schematics for the #183 states 450mA DC (the other schematic I have only lists the original seemingly no longer available PTs)... I'm probably at the edges of my knowledge re: loads and power requirements here...There is a "TF130" listed on the magicparts.com site... unclear to me if this is the same or different, they don't list the specs—other than the amps it's designed to go in seem to all be high power...

[ijedouglas]

I haven't heard back from Merren about pricing/availability but I found both on their site... question though... the PT T2562 is listed as 150mA "quiescent load" and much higher bias winding (100V AC), but one of the schematics for the #183 states 450mA DC (the other schematic I have only lists the original seemingly no longer available PTs)... I'm probably at the edges of my knowledge re: loads and power requirements here...There is a "TF130" listed on the magicparts.com site... unclear to me if this is the same or different, they don't list the specs—other than the amps it's designed to go in seem to all be high power...

Correct, the bias winding is 100V. I use a 13K resistor in the bias circuit instead of the 3K9 and it's just perfect.

Not sure about the 150mA "quiescent load" but I have a set in my 183 and BluesMaster and they run just fine. Probably just fine considering they are technically built for a 100W plexi.

The TF130 may be the same model number but it is a completely different transformer. I have one if you are interested

Chris can be a little difficult to get hold of at times but you will honestly not regret getting a set from him. Charlie Wilson from the forum put me on to them and I'm sure he will agree on how good they are. I have no affiliation with Chris but I do know what a big difference these made to my builds.

[martin manning]

Not sure about the 150mA "quiescent load" but I have a set in my 183 and BluesMaster and they run just fine. Probably just fine considering they are technically built for a 100W plexi.

Most power transformer spec's quote full-load voltage, and sometimes no-load voltage is also listed. The idle (quiescent) condition where most people measure voltages in their finished amp is a part-loaded condition, which Merren is using to list expected voltage: "Typical B+ voltage: 465V @ 150mA quiescent load."

[professormudd]

IMO, eyelet boards are the best and most authentic choice for a Dumble, and I think you'll find eyelets are easier to work with than turrets.

I agree with this whole-heartedly. I am not a pro or even a seasoned hobbyist, but I have built out a couple of amps using both the AA Electronics PCB as well as a set of boards from Taylor at Amplified Nation that use Mr. Manning's layouts.

The AA Electronics PCB is very well built and sturdy, and I do like the amplifier I got out of it. It posed a few challenges for me. Namely since the power section is designed to accomodate several different configurations, I got confused with the proper holes for some of the filter caps and ended up nearly going mad chasing down the resulting hum. I am not proud of how long it took me to notice this snafu, and I do not blame the layout at all. Another challenge was changing out the relays. I needed to replace both of the replays at one point, and getting them back out of the all-in-one board was a huge pain in the ass. The board being an all-in-one is both a blessing and a curse.

I found the eyelets helped me keep a tidier build and the chassis is definitely less crowded since the FET, rectifier, and relay supply are mounted to the sides. With multiple boards, it is also easier to do modifications or troubleshooting since you don't have to disturb everything every time.

I think the AA boards are great for just wanting to get a killer amp up and running relatively quickly. I prefer the eyelets for a build where I want to take my time and show off what's under the hood.

Just my $0.02

[ijedouglas]

I couldn't agree with Matt any more. In my experience, you will need to tweak the circuit multiple times and an eyelet board is the way to go.

[pfarrell]

Thanks for your work on the boards Martin... was able to make quick work of this...

PF-183_01.jpg

[martin manning]

You're welcome, looks great! Which version of the power supply boards are you planning to use?

[galtjunk]

Heyboer makes a twin pt with dual 6.3v taps so you can power your relays.
They have enough ma to power a quad of El-34's and the pre amp tubes plus some.
They also make a suitable OT.
Call Phil at Heyboer. He will find the transformer numbers for you.

[pfarrell]

You're welcome, looks great! Which version of the power supply boards are you planning to use?

This one... but with some values modified for the #183 schematic. (?)

DIY_Eyelet_Boards_100W_ODS_Radial.pdf

[martin manning]

This one... but with some values modified for the #183 schematic. (?)

The 183 changes would be 330u for the reservoir caps, but choose the relay supply circuit based on your AC source (12.6 vs. 6.3VAC) and chosen relay voltage. If you build with all radial caps and mount the regulator on relay supply board, I believe you would be the first to do that. You could attach a small heat sink to the regulator, but my math says it should be ok without one.

[pfarrell]

This one... but with some values modified for the #183 schematic. (?)

The 183 changes would be 330u for the reservoir caps, but choose the relay supply circuit based on your AC source (12.6 vs. 6.3VAC) and chosen relay voltage. If you build with all radial caps and mount the regulator on relay supply board, I believe you would be the first to do that. You could attach a small heat sink to the regulator, but my math says it should be ok without one.

Understood. All radial and mounting regulator per your layout looked great, logical and efficient to me—saves some space too—I have some small sinks laying about, might as well use one. If I get the Merren Iron, which is likely—I'd need the extra 12V trafo., which I also have laying about. (What I don't have is 15mm trimmers for the main board!)