Baldwin Organ Amp Conversion to Carmen Ghia Clone

[Platefire]

Well it begins! Does anybody have any info that this project has actually been built? I couldn't find any! but I was looking for an instance to see if the results was a good outcome. Some things about this amp seem kind of radical to my conservative fender background regarding tone stack, PI, NFB and power supply. So it's suppose to be a reverse engineered CG but you can't prove it by me. So I've started gutting the Baldwin amp and thinking how I will arrange things in there to make it fit. So attached is the Phoenix Project schematic and Layout that I will go by except I will be doing an old style P to P in my small chassis(no board).  Platefire  

[Platefire]

I'm referencing this link because this tread for the Baldwin Amp conversion actually started on the "Dr Z Carmen Ghia schems needed" thread. So some very good starter information for this project is listed there. Platefire

 
http://www.el34world.com/Forum/index.php?topic=13242.0

[Platefire]

From Dr. Z himself, here in his own words of an interview how the Carmen Ghia came to be:

Was that truly your first amp?

 

Not really. The Carmen Ghia was the first amp that I ever sold. To this day, I’ve probably built more of those heads than any other—somewhere around 400. It wasn’t even called the Carmen Ghia at the time. I named all of the early amps after my children—my grandson Carmen for the Ghia, and the SRZ was named after my daughter Sheree Roses. The original configuration for the Carmen Ghia was based on a Hammond reverb amp. I have a friend named Charlie Jobe, and if you look on Jimmy Smith’s albums you’ll see him credited—he was the Hammond organ master in the U.S., and he was almost in his 90’s when I met him. His house was just filled with Hammond stuff, and one day I saw these little EL84 amps sitting on a shelf and I asked Charlie what they were. He said, “Oh, those are Hammond reverb amps—they weren’t very popular.” They were optional for a B100 and it would tie the input from one of the speakers and drive its own separate speaker through a reverb pan. I thought that would make a cool guitar amp, so I built a few, and I’d take them to guitar shows and sell every one I’d brought for around $350 each. Of course, all of the $1,000 amps that I’d brought would be carried back out at the end of the show because in those days, no one wanted to spend $1,000 on an amp at a vintage guitar show.

[Platefire]

OK, I finished gutting the Baldwin Chassis last night. Here are some shots of what it looks like now.

Genral overall plan to put a bolt on cover plate over those holes in the top of the chassis to cover that area. Locate the input jack/vol/tone in front opposite end of OT end in front of 12AX tube sockets. Pilot light, power switch and standby switch to go in front opposite side in front of existing rectifier socket. The chassis came out of the organ with a bolt on steel bottom plate. So I plan to use that and mount four amp feet on it. Rear of chassis would use the existing power cord hole for a new 3 conductor AC power cord, use existing fuse holder and I'll need to drill another hole for speaker output.  

 So it's a tight fit especially with all the extra Carmen Ghia power supply circuitry. I have two basic plans for the power supply that I'm trying to decide on as follows:

1-Remove the rectifier socket from it's present location and install it in the hole that use to be A.C. Power outlet to the organ between the PT and OT. That would free up that area where the rectifier now occupies to maybe build a small board to mount most of the power supply.

2-Leave the rectifier in present location. Install a 50uf/50uf/500V can cap in the A.C. Power hole between transformers and then string out the remaining power supply circuit on three seperate terminal strips located around the rectifier area.

Right now I favor plan #1. If you have good reasoning why it might not be a good idea to move the rectifier to that location, please let me know! Platefire

[DummyLoad]

what i would do personally, and bear in mind that i'm not the sharpest knife in the drawer; i'd use the the AC power hole for a can cap and leave the 5U4 where it is. i'd make use of 16mm pots for the front panel. drill all the holes before proceeding. along end of the chassis with the four holes, id use one plate to cover all four holes from the inside and mount term strips to the cover plate for some of the pre-amp circuitry. 

happy rosin smoking... :-) 

--DL

[Willabe]

I think your #2 plan is best, and is what DL said too.

I don't think putting a hot Rec. tube so close between the PT/OT and with restricted air flow is a good idea?


                      Brad     

[Platefire]

You guys really threw a monkey wrench in my spokes  

I was about to pull the trigger on a parts order with plan #1---now you got me reconsidering but that's what I ask you to do! So I'll hold off ordering and think about it a little more. No problem with full size pots. I only need a vol and a tone. I even sketched out a full size 4" long board to fit where the existing rectifier is at. I couldn't get it all on the board, the last part of the power supply circuit for V1A would have to go on the existing front terminal strip.
  
Anyway thanks for taking a look at it and I'll re-look at it from your perspective. Platefire

BTW-I have a NOS two 40uf/400v can that plugs into an octal socket. If I were to use that can in the existing hole with an octal socket with loaded voltage running 320VDC--I'm wondering if it would hurt if I skimp from the schematic 50uf/500V?

[John]

BTW-I have a NOS two 40uf/400v can that plugs into an octal socket. If I were to use that can in the existing hole with an octal socket with loaded voltage running 320VDC--I'm wondering if it would hurt if I skimp from the schematic 50uf/500V?

It runs in my mind that you should allow at least 20% for startup (unloaded) voltage, and more is better. But for petey's sake, don't take my word for it!

[Platefire]

Well on the can cap, I went back and looked at it and its 450V--so that's a little better. I never seen one that fits into a octal socket before. My radio station tech friend gave me two of those. The only bad thing is someone could actually un-plug the filter caps--just like a tube.

  I've looked over the situation in the chassis and I really don't have room for a 3 1/8" wide board in the area of the rectifier even if I moved it to the back hole--it would be to cramped up against the pilot light, power and standby switches. I could cut the board down to less than 3 1/8" inches wide but I think I've sketched out a pretty good plan to install the power supply on terminal strips.
  I want to do a layout plan for the rest of the circuit now. Just want to be sure how everything will go before I order the parts. Platefire 

[m3moser]

Sorry to come late to the discussion.  I have built this circuit several times.  They sound great- and I have used Hammond Organ donors or scratch builds for mine.  Here are some pictures.

[m3moser]

Duh, forgot to add pictures.

[Platefire]

Did you go by the schematic I'm using? and I see you have an extra control knob. Carmen Ghia's usually have only two--vol/tone. Platefire

[Willabe]

m3moser,

That is one beautiful wood cab! Nice job!   

[HotBluePlates]

Yes, gorgeous cabinet m3moser!

For Platefire:
I've gotta second DL's suggestion. Stick the cap can between the transformers, in the AC Power hole. If it were my amp, I wouldn't use a plug-in filter can, if for no other reason than you'll probably never find a functioning replacement when it comes time to replace it. Forget the risk of being shocked by a charged and removed filter cap.

If you have more than 1.75-2" in that space, you can easily fit a modern can cap. If you don't have over 335v unloaded output from the PT, then a 475v-rated can will work fine. 50uF/500v is just a leftover from what the reverse-engineered original had; I'd bet you don't need a 500v rating.

Now that I had a chance to grok your original plan (outside the two scenarios), I agree that seems like the sensible way to go. Plate over the holes, and have input enter in the vicinity of where the original can caps were, so that they can go into the 12AX7's and on to the EL84's in a logical manner.

Looks like an exciting project!

[Platefire]

Thanks HBP. Well I did a full size sketch tonight pretty much to scale and found a place to make all connections and place all components. It will require 7 extra terminal strips. Those are 5 term terminal strips and some of them will have to be shortened to fit in the locations shown. My sketch is probably un-readable to anybody else except me. I just needed to prove to myself everything could be fitted. Attached is the sketch but you'll never be able to read it. Platefire

BTW-On the sketch, I see where I left one connection off---V1B plate pin #6 to .01 cap on terminal strip to PI.

[tubenit]

m3moser,

That is one of the most beautiful cabs I've seen!  Remarkable job.  I love it.  Looks to be figured cherry with flamed maple.  Nice choice.

Platefire,  he set a pretty high bar for you to meet!   

With respect, Tubenit

[Platefire]

Well it's kinda like Clint Eastwood said, Good to know your Limitations!   In my case it's "Outer Limits"  

BTW-I agree, fine looking cab! Now how about the gut shot!

This amp is a real brain teaser. I should of never gave my customer an option to convert or new scratch build. Live and learn! That's the amp I was planning a Stout for myself.

[HotBluePlates]

Plate:

I didn't check every component and connection, but I do like your overall plan: power/rectifier portion of the chassis blocked off by filter caps, with terminal strips framing the sockets. I am using almost the exact same approach in my current build.

Looks like a winner!

[Platefire]

Good! Tight fit but unless I overlooked anything---should be good to go.

[birt]

that is a great drawing. good work!
i like to do this too before i start building. now i'm working on a B15 where i didn't draw the layout, only the board and it doesn't have the whole circuit on it. even for a 'simple' amp like that it's quite hard to make a layout while building it.

[Platefire]

Thanks birt! but that's a pretty pitiful drawing even by my own standards but-being it was sketched pretty much to scale it did allow me to work out the puzzel of getting everything to fit. At least it's a plan I can follow to git R dun. I did several other previous sketches that made me realize those plans wouldn't work. Not sure what a B15 is but I hope your project turns out well. Platefire

[birt]

ampeg B15n, single channel version. preamp with vol, treble, bass and PP 6L6 cathode biased poweramp.

[PRR]

> Not sure what a B15 is

[Platefire]

Got a bass playing friend that has requested me build him a bass amp. I've been at a loss because most bass players I know just use SS amps and I have no experiance with bass tube amps. That might be a consideration--has anybody ever use that pre section but used it to 4-6L6's? Platefire

[Shrapnel]

  (by OP)

Got a bass playing friend that has requested me build him a bass amp. I've been at a loss because most bass players I know just use SS amps and I have no experiance with bass tube amps. That might be a consideration--has anybody ever use that pre section but used it to 4-6L6's? Platefire

Hmm... Lessee Plate....

Firemedic's most related post as an answer to your question: http://www.el34world.com/Forum/index.php?topic=13458.0

Others talking about building a bass amp:
http://www.el34world.com/Forum/index.php?topic=13324.0
http://www.el34world.com/Forum/index.php?topic=13001.0

 

[Platefire]

Well I'm getting parts in so it's time to start moving out on this CG clone.

I got a JJ can cap 50/50uf 500v 1 3/8" diameter with clamp. So I've never actually installed a new can cap before. The existing hole in chassis where I want to install the can is 1 1/8". It appears to me I could just butt the can up to the chassis hole and let the connectors stick through the hole and it would work that way. If I understood previous discussions about installing a can like this, the norm is to drill the hole out (1 3/8") so the can with stick through the chassis to the inside. Is that necessesary? Don't think I have any means on hand to drill out that big at the moment. Platefire

BTW-the hole between the transformers is where the cap needs to go.

[sluckey]

I prefer to have a smaller hole so the bottom of the cap can rest against the chassis. Here's some I replaced that's a similar case as yours...

[Platefire]

Thanks Sluckey! As they say, a picture is worth a thousand words. Nice layout and lead dress! I wish I had as much chassis space as you do to play with but I'll not complain and consider it a challenge.

One question though, I don't see any grounding wires going to the can cap ground lug--am I just not able to see it or what? Platefire

[sluckey]

Can you see'm now? Black wires connected to a star ground just to the right of the PT.

http://home.comcast.net/~seluckey/amps/hammond/closeup.jpg

[Willabe]

Can you see'm now?

No, I can't see them. Should have used pink colored wire?              

[Platefire]

Sho Nuff! See'm Now. At pictur is wurth bout 10000 wurds. sluckey I fishally Krown U a "redneck Kammunicator" at means U r Kapeable ov Kammunicaten wid a red neck widout a interpatur.
Corngradulasions!!!!   I'll pass da wurd 2 da udder toob heds hear n Lousyana.


Seriouly-Thanks! Platefire

BTW-Went by Lowes this afternoon and got a 22ga x 6" X 18" steel plate for $5.00 to make a cover for the top holes cover. I usually have some plate on hand to use in a case like this but my stock is running low. Also got a couple of plastic 3/8" plugs($1.07) to cover a couple of un-needed holes plus a package of #6 x 32 x 3/8" long machine screws ($1.26)and nuts to bolt down the plate/terminal strips. Simple little stuff is getting expensive these days!

[Willabe]

Sho Nuff! See'm Now. At pictur is wurth bout 10000 wurds. sluckey I fishally Krown U a "redneck Kammunicator" at means U r Kapeable ov Kammunicaten wid a red neck widout a interpatur.
Corngradulasions!!!!   I'll pass da wurd 2 da udder toob heds hear n Lousyana.

Dog Gone cajin's, don't know what their sayin, but I Love their music & food!!!!!    I-eee!

Save me some of those crawydads!!!!!



                                  

[Platefire]

CORRECTION! Well a Red Neck is what is found in the Northern Hills of Louisiana, can be called by "Bubba" and incorperates two or three English words together into one like "airyago" interpreted "There you go". Cajuns are found in South Louisiana in the swamps/marshes and speak their own brand of French. Shoot Him! Shoot Him! interprted &^%)#@

OK back to the Carmen Ghia!

[Platefire]

Back to my previous Baldwin Output transformer test. The results were as follows:

I put my 14.44 VAC to the OT two primary brown and blue wires to plates and got .37 VAC measuring across the two secondarys/speaker wires.

14.44/0.37=39.03= That Means turns ratio 39:1

39 X 39=1521 turns ratio squared means impedance ratio of 1521:1

So in a given load impedance of 8 Ohms the transformer is 8 x 1521=12168 Ohm or 12.2K

I HAVE QUESTIONS:

1-Does the results of my test indicate the OT output is 12 Ohms??? or am I reading the results right?

2-What Ohm speaker needs to be used with this for best results??

3-My intent was to use 8 Ohm speaker--will this work?

[John]

-Does the results of my test indicate the OT output is 12 Ohms??? or am I reading the results right?

I am only answering this because talking about things helps me learn them, not because I actually know. 

I think that the 12.2K impedance that you came up with means that it's a good match to use the 8 ohm speaker with 2 6v6/6L6 tubes. I think I remember PRR saying that a 6V6 "likes" about 6K. So with a P/P 2 tubes that would be about right. 

Not only "could be" wrong, but "probably am" wrong.

[Platefire]

Well Thanks John. I've got PP/EL84's kinda similar to a 6V6. Yeah I just don't know how to feel about my OT as far as what Ohms it actually is and rather it would be a good match for my 8 Ohms speakers. Impedance and Ohms regarding OT is kinda like Voodo to me---don't understand it. So I was hoping somebody in the know could positively answer my questions in the previous post. Platefire

[Platefire]

Today I drilled the chassis and patched/covered the un-needed holes from gutting out process. Getting close to where I can start wiring it up. First I need to carefully place about 7 terminal strips.
It is starting to look more like an amp now.

Do you think I could get away without painting that unfinished 22 Ga steel cover plate I added or should I prime and paint it? Platefire

[6G6]

I think, sooner or later, that steel is going to rust.
You could paint it with aluminum paint and it would sort of blend in.

[mresistor]

Or, you could clear coat the steel plate so it won't rust. 

Looking good.

[Platefire]

Yeah I thought the patch plate matched the existing chassis pretty good as is and the chassis is un-finished steel. Clearcoat might be a good idea or just gray primer.

[mresistor]

I was thinking these Baldwin chassis might be a type of steel alloy like a stainless.

[Platefire]

mresistor

Your probably right or it would have already rusted up. At any rate I will pull the cover plate off and paint it because I do want to build my stuff to last. Platefire

[John]

Back to my previous Baldwin Output transformer test. The results were as follows:

I put my 14.44 VAC to the OT two primary brown and blue wires to plates and got .37 VAC measuring across the two secondarys/speaker wires.

14.44/0.37=39.03= That Means turns ratio 39:1

39 X 39=1521 turns ratio squared means impedance ratio of 1521:1

So in a given load impedance of 8 Ohms the transformer is 8 x 1521=12168 Ohm or 12.2K

I HAVE QUESTIONS:

1-Does the results of my test indicate the OT output is 12 Ohms??? or am I reading the results right?

2-What Ohm speaker needs to be used with this for best results??

3-My intent was to use 8 Ohm speaker--will this work?

I've been thinking about this some more but didn't follow up cuz I thought someone else would. First, why did you think your test meant 12 ohms? The output impedance with an 8 ohm speaker is 12.2K ohms. If you had wanted to use a 16ohm speaker, your impedance would be 24.3K ohms. So if I'm understanding thing correctly, I might actually have been right.

Which explains the heavy storms out west.

[sluckey]

14.44/0.37=39.03= That Means turns ratio 39:1  OK

39 X 39=1521 turns ratio squared means impedance ratio of 1521:1  OK

So in a given load impedance of 8 Ohms the transformer is 8 x 1521=12168 Ohm or 12.2K   OK

I HAVE QUESTIONS:

1-Does the results of my test indicate the OT output is 12 Ohms??? or am I reading the results right?  No

2-What Ohm speaker needs to be used with this for best results??  4Ω will reflect 6K to the tubes. Pretty good for EL84 or 6V6

3-My intent was to use 8 Ohm speaker--will this work?   It will work. 4Ω is mo betta.

[Platefire]

Hay! Hay! Hay! Thanks-----Appreciate you clearing that up for me. Is there any chart or info page I can download as a reference that gives the K impedance required for a OT for each type of tube setup or is that provided in the tube specs?

Also what would the impedance need to have been to be best suited for a 8 Ohm speaker with PP/EL84? Sorry for asking all these dummy questions but I never got into this to deep before---but as you see it's very much needed. I've learned how to test the impedance of any given OT, I just don't know how to interpret the data once I get it! Platefire  

[sluckey]

Is there any chart or info page I can download as a reference that gives the K impedance required for a OT for each type of tube setup or is that provided in the tube specs?

I've seen a chart that has most of the common output tubes with plate impedances but don't know where it is. Probably on this site. Do a search.

Also what would the impedance need to have been to be best suited for a 8 Ohm speaker with PP/EL84?

I'd say 8K:8Ω, or 6K:8Ω

Something you may need to nail down... An OT has no impedance itself. It simply matches the high impedance of the output tube plates to the low impedance of the speaker. When you see an OT spec that says 6600Ω:8Ω, you're really seeing a RATIO. Those numbers mean the OT would make a nice match between 6600Ω plates (think 6V6) and an 8Ω speaker. But it's a ratio and as such, 6600Ω:8Ω is the same as 3300Ω:4Ω, and those numbers make a nice match to 3300Ω plates (think 6L6 or EL34) and a 4Ω speaker. I'm not gonna say anything about power other than the obvious... Higher power tubes naturally want a higher power OT.

So, what happens when you use an OT that doesn't have the proper impedance ratio? This is an impedance mismatch and you cannot transfer all the power from the tube plates to the speaker.That's the main thing you need to know.

[Platefire]

Thanks sluckey

I don't have complete understanding yet but I now know about 100% more than I did. I did some searches on google last night. I've been reading OT specs. I have to say I'm a little confused about
dividing up the K impedance between SE, PP 2tube/4tube. For instance---looking at a Fender Replacement OT for a tweed deluxe indicates Primary impedance=8000CT/8 Ohms. I'm thinking two 6V6's at 8000K x 2=16000K/2 6V6's=8000K. Reason being I'm thinking of my existing 12.2K/2 EL84's=6.1K each that we just discussed.

Also looking at a Fender Blues Jr spec which I know is PP/EL84 Primary Imp. is 6950CT/8 Ohms--I assume the ratio you discussed. Still befuzzeled thinking of the combined impedance of two EL84 output tubes compared the the spec 6950???

I have learned that impedance is like a resistance and Ohms is the measurement of the impedance--from the anology of a water hose with water pressure being voltage and the amps increasing/or decreasing with the water pressure(voltage) and your thumb over the end of the hose holding back the pressure is impedance. I understand as you said the OT is a impedance matching device between high impedance tube plate output and low impedance speaker. At least I think thats what I understand?? Har! if that's correct??   Platefire

[mresistor]

two 8 ohm speakers in parallel would be cool...sound good too..

[HotBluePlates]

I have to say I'm a little confused about dividing up the K impedance between SE, PP 2tube/4tube. For instance---looking at a Fender Replacement OT for a tweed deluxe indicates Primary impedance=8000CT/8 Ohms. I'm thinking two 6V6's at 8000K x 2=16000K/2 6V6's=8000K. Reason being I'm thinking of my existing 12.2K/2 EL84's=6.1K each that we just discussed.

It don't work like that.

But that's okay... Look at what you can find for "replacement OTs" for particular amps. Note the type and number of output tubes, and the spec primary impedance of the OT. You'll start to see typical pairings, although these can vary.

Also looking at a Fender Blues Jr spec which I know is PP/EL84 Primary Imp. is 6950CT/8 Ohms--I assume the ratio you discussed. Still befuzzeled thinking of the combined impedance of two EL84 output tubes compared the the spec 6950???

Well, 6950 is pretty much 7k. 7k is pretty dang close to 8k, at least closer than 3-4k is. So, let's call it "six of one, half-dozen of the other".

You're wanting to rebuild this amp into a Carmen Ghia. The original amp used this OT with a pair of EL84's. You have figured out on your own that the probable speaker load needs to be 4 ohms. I think your work is done.

If we live and die by each clean watt coming out of the speaker, we might need many copies of a set of plate curves, a mechanical pencil, and a lot of time spent trying various proposed plate loads.

But you and I probably won't know the difference between a 14w amp and a 25w amp, except by how high we have to turn up the volume knob before distortion. So laboring over the "perfect load" is probably good for later when you want to work a puzzle.

Instead, we need to know, "will it get up and go?" Kinda like buying a used boat, and considering replacing the motor. Do you slap on the whopping 22HP motor from a professional lawnmower? Or do you strap on a 470HP V8 tweaked for street racing? Probably not, unless you want to either sink with the engine off or turn boat into a really lousy paper airplane with it at full-rev.

Or maybe you pick a 115HP V4 motor similar to what it came with when you bought it. If you really wanted a step up, you might get a 130-150HP motor, not too different than what is already on it. Or, maybe you say, "runs good-enough. I'll leave what's on it."

Don't sweat it. You can leave what's on it. 

[Platefire]

Well It just isn't for this amp. Yeah we have determined a 8 Ohm speaker will work, a 4 Ohm mo-better! Since I was already into this OT learning curve--I was just trying to learn a little bit extra for future reference. My amp knowledge is basically just general at best--not to deep into any one thing but in this paticular area---output tubes to OT I've almost been less than general knowledge--so cut a ol country red neck some slack! It may take me a long time to "get it" but once I got it "I got it", for a day or two anyway!    Thanks, Platefire