# Modding an amp....



## screamingdaisy (Oct 14, 2008)

What would happen if I took this amp (Orange AD140);

http://users.telenet.be/orangefg/OFG_SCHEM/AD140TCmainboard.pdf

http://users.telenet.be/orangefg/OFG_SCHEM/AD140TCmainboard2.pdf

http://users.telenet.be/orangefg/OFG_SCHEM/AD140TCfrontpanel.pdf


And converted it to use 6550s?

Also, are we talking a simple bias, swapping a few resistors, or requiring a new tranny?


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## bcmatt (Aug 25, 2007)

While waiting for the experts to reply, I'll give my guesses. 
I'm thinking that would not be easy, and that you would need a new (bigger) OT, at least to handle the higher output. I think going from 6550s to EL34s is more possible. But you never know, maybe Orange is one of those companies that cares more about giving you versatility than about only paying for as big an OT as they need (but I doubt it).
I figured I would sprinkle a little on your parade before the real experts tell you if its going to pour or not.

I'm curious why you want this exactly. Are you having headroom issues? Is it not giving you enough power? Are you dreaming of an SVT and want this to be your new bass amp? Are you wanting to just try new tube types for the tone experience?


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## Ripper (Jul 1, 2006)

The tranny should take it, the ratings with the tube types are very similar. Trannys become more of an issue when converting 6l6 amps to el34s etc.

You should just need to rebias, so what that entails for a particular amp. However, you would need to check and see if the amp will physically accomodate the 6550s as they are a bigger tube and require more space etc, not all amps will fit them.

What type of sound change are you looking for? If you are looking for more clean headroom and more bottom end, consider a pair of true 6CA7's. They are somewhere in the middle of the el34/6l6, more clean headroom, good mids etc.


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## bcmatt (Aug 25, 2007)

Sorry, I was assuming that 6550s are 6L6s. Are they more similar to EL34s? Maybe I should check some charts.


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## Ripper (Jul 1, 2006)

bcmatt said:


> Sorry, I was assuming that 6550s are 6L6s. Are they more similar to EL34s? Maybe I should check some charts.


more along the lines of a el34. Alot of american marshalls were shipped set up for 6550s instead of el34s. They have more headroom, more bottom end, guys like Zakk Wylde run them in their amps. I've tried them but they weren't my cuppa. I'm still more of a cranked el34 person.


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## screamingdaisy (Oct 14, 2008)

bcmatt said:


> I'm curious why you want this exactly. Are you having headroom issues? Is it not giving you enough power? Are you dreaming of an SVT and want this to be your new bass amp? Are you wanting to just try new tube types for the tone experience?


You caught me. I'm getting back into bass. I have my old bass, but no amp or cab. I'm looking to pull off an SVT on the cheap using an amp head I already have.




Ripper said:


> The tranny should take it, the ratings with the tube types are very similar. Trannys become more of an issue when converting 6l6 amps to el34s etc.
> 
> You should just need to rebias, so what that entails for a particular amp. However, you would need to check and see if the amp will physically accomodate the 6550s as they are a bigger tube and require more space etc, not all amps will fit them.














> What type of sound change are you looking for? If you are looking for more clean headroom and more bottom end, consider a pair of true 6CA7's. They are somewhere in the middle of the el34/6l6, more clean headroom, good mids etc.


A number of years ago Orange converted an AD140 Lead (EL34) into an AD140B (6L6s). The version was extremely limted (only 17 made), and soon replaced by an AD200B with a quad of 6550s.

AD140 Lead









AD200B









I have an AD140TC, which is the twin channel version of the AD140 Lead.

I'm sure Orange made some changes to the tone stack, but I figure if I can make the AD140 a little more suitable for bass by squeezing some extra headroom out of it then I can skip buying an Ampeg for the time being... if not forever.


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## bcmatt (Aug 25, 2007)

Sounds like a neat project. It's nice to learn about these other tube types. I think I too commonly just group the different named tubes and declare them as simply just EL34s or 6L6s. Keep us informed how the project works out.

My Traynor amp that I use for bass has a quad of 6ca7 EL34s. So does that mean that they will produce better bottom end than typical EL34s? I do like it for bass, and I noticed a huge difference when I managed to get an actual Ampeg 4x10 cab at a screaming deal.
What are your plans for a cab? I do agree with those who say that once you use a speaker cab for bass, you can't go back. My 15" speaker that I used before sounds horrible with guitar now (and doesn't sound that great for bass either). Anyways, do you have a bass speaker cab, or speakers that you never plan to use for guitar again?


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## Ripper (Jul 1, 2006)

bcmatt said:


> My Traynor amp that I use for bass has a quad of 6ca7 EL34s. So does that mean that they will produce better bottom end than typical EL34s?


The EL34 is a power pentode and the 6CA7 is supposed to be the exact American equivalent, but the U.S. Sylvania 6CA7 is a beam
tetrode, with beam-forming plates and reduced screen current)
along with larger plate and cathode structures.

The tend to have a tighter more focused bottom end and more headroom. 
Sylvania 6CA7's are the NOS ones to get if you can find them but the EH Big Bottle 6CA7 aren't bad either.


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## screamingdaisy (Oct 14, 2008)

bcmatt said:


> What are your plans for a cab? I do agree with those who say that once you use a speaker cab for bass, you can't go back. My 15" speaker that I used before sounds horrible with guitar now (and doesn't sound that great for bass either). Anyways, do you have a bass speaker cab, or speakers that you never plan to use for guitar again?


I'm looking at a few options....

My first earge is an 8x12... though I admit it's probably overkill.

I'm leaning towards a 4x10 and a single 15.

I figure that if I need more power than what the AD140 is kicking out I can run a second guitar amp.


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## Ripper (Jul 1, 2006)

Nobody listens to the bass player anyways....


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## screamingdaisy (Oct 14, 2008)

Ripper said:


> Nobody listens to the bass player anyways....


Nobody listens, but there's a reason they're all bobbing their heads.:banana:


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## bcmatt (Aug 25, 2007)

Ripper said:


> The EL34 is a power pentode and the 6CA7 is supposed to be the exact American equivalent, but the U.S. Sylvania 6CA7 is a beam
> tetrode, with beam-forming plates and reduced screen current)
> along with larger plate and cathode structures.
> 
> ...


I'm sorry. I was mistaken. I just checked and I guess my 6CA7s don't say EL34 on them at all. They just say Mullard and 6CA7. As far as I know, they could be the original tubes in this mid 70s Traynor. Are the Mullards from that era ok? How do they compare to the Sylvanias and EH Big bottles? They sound nice enough to me anyways; I just wonder how the descriptions would compare.



As far as cabs go, I originally thought of going 1x15 and 4x12 too, but it seemed that all the 4x10s I found were 4 ohm, and my amp has 4 ohm output. I was hoping to use my existing 1x15 with it, but the sound improvement was so great with the 4x10 on it's own, that I didn't miss the 15 at all (it sounded (and smelled) like ass anyways). I feel like a 2x10 with a 1x15 doesn't allow for any single cab to be big enough to get a nice fat bottom end. I don't really feel that the 4x10 has left me with much to be desired, but I've never had the opportunity to try a real 8x10 in real circumstances anyways.

Your amp can produce more power than mine (75 Watts RMS) so, maybe it would feel safer to have that 15' with a 4x10 as well. Let me know if you find something that works. Those 8x10s are cool too, if you can fit them in your car.

So, are you going for the tube switch, or are you gathering more information?


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## screamingdaisy (Oct 14, 2008)

I'm probably going to sit on it for now. I'll try the AD140 when I get the chance, and if it doesn't work out I'll consider the tube swap.


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## Ripper (Jul 1, 2006)

bcmatt said:


> I'm sorry. I was mistaken. I just checked and I guess my 6CA7s don't say EL34 on them at all. They just say Mullard and 6CA7. As far as I know, they could be the original tubes in this mid 70s Traynor. Are the Mullards from that era ok? How do they compare to the Sylvanias and EH Big bottles? They sound nice enough to me anyways; I just wonder how the descriptions would compare.


Those Mullards should be great, I've yet to meet an old Mullard tube I didn't like. As far I know the mullards are more of a true el34, it was the Sylvanias that were somewhat different.


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## Wild Bill (May 3, 2006)

screamingdaisy said:


> I'm looking at a few options....
> 
> My first earge is an 8x12... though I admit it's probably overkill.
> 
> ...


Just a couple of cautions! First off, the 6550 is more in the 6L6 family than the 6CA7. This means it is not as sensitive for the same amount of drive as the 6CA7, which is why when Marshall changed to them the classic Marshall sound was born. So 6550's sound cleaner than 6CA7's.

Biasing is the easy part. You may have to change a resistor or something to get the proper range on the adjustment pot.

The big deal is that you mentioned you want to use the amp for bass. You should understand that if the output transformer was for a regular lead guitar then you will only be able to run a bit more than 50-60% of the power for a bass guitar.

This is because an output trannie for bass needs to be at least a third heavier and bigger to handle the increased energy of those bass notes. If you compare an Ampeg V4 and V4B you will see the difference right away.

Also, the plate load for 6550's is more similar to a 6L6 than an EL34/6CA7. This means that you should run an 8 ohm cab on the 4 ohm speaker setting. This will transform up to be a better match for the 6550's.

In the words of Gilda Radner "It's always something!".

:food-smiley-004:


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## bcmatt (Aug 25, 2007)

Wild Bill said:


> In the words of Gilda Radner "It's always something!".
> 
> :food-smiley-004:


Wild Bill, I always love the quotes you choose. I think I chuckle every time. I seriously can't think of anyone else I know that would quote Gilda Radner. I'm not even sure who she is, but if I had to venture an ungoogled guess, I would go for either an early 80s (or older) TV character, or the actress who plays one.
I do recognize the name though. Anyways, keep them coming. I will proceed from here to wikipedia and my education shall continue.


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## Wild Bill (May 3, 2006)

bcmatt said:


> Wild Bill, I always love the quotes you choose. I think I chuckle every time. I seriously can't think of anyone else I know that would quote Gilda Radner. I'm not even sure who she is, but if I had to venture an ungoogled guess, I would go for either an early 80s (or older) TV character, or the actress who plays one.
> I do recognize the name though. Anyways, keep them coming. I will proceed from here to wikipedia and my education shall continue.


Glad to give you a chuckle, Matt! Most of my quotes are "baby boomer" humour. Gilda Radner was one of the original cast of Saturday Night Live. She had a lot of memorable characters, especially one little old lady who would appear on the news desk, railing about some issue that she had mis-heard, like "violins on television". When the news anchor would stop her and gently explain her misconception, she would give a flustered look around and say "nevermind!". "It's always something!" was the title of her autobiography. Sadly, we lost her years ago to cervical cancer. She was as much of a giant as John Belushi.

Many of my quotes I confess are even more obscure. I was really into "head humour" back then, like Cheech and Chong, George Carlin and especially FireSign Theater! They were part and parcel of the psychedelic music scene and so when I make a reference I always know that at least a few of the guys on this board will have a nostalgic chuckle!:smile:

They say if you can remember the 70's you weren't there!:smile:

:food-smiley-004:


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## mhammer (Nov 30, 2007)

In the mid-70's, we used to get the National Lampoon Radio Hour in Montreal on CHOM-FM. Since my English prof at CEGEP (Sean Kelly) wrote for the National Lampoon (itself a derivative of the Harvard Lampoon, a satirical student publication from that same school), I listened keenly to Radio Hour (which retained the title even after switching to 30 minutes). As you can see at this site - http://www.marksverylarge.com/nlrh/nlrhintro.html - most of the notables in comedy during the 70's and into the 80's, and many of the cast members of SNL, were part of Radio Hour. 

Harry Shearer still does many of the same generic characters now on the Simpsons that he was doing for Radio Hour back then. One of my favourite bits of his was a fake interview with him as an effete A & R guy from a big recording company (I think this was the Ron Fields character). According to him, the new trend for the coming season would be whaling songs, and everything else would be "down the dumper". Kep in mind that this is occurring at approximately the same time that Jon Landau is declaring (in New York) that Bruce Springsteen is the "future of rock and roll".

Another loved bit concerned a California hitchhiker being picked up by a driver, who finds out bit by bit that the hitchhiker had been in a coma for several years as a result of being beaten by a Hells Angel at the outset of a Grateful Dead concert that was on a barge released from Golden Gate Park or somewhere like that (for which the Dead had vowed to keep playing until they reached Hawaii). The driver starts to fill in the hitchhiker about changes to pop culture while the passenger had been comatose. One after another, he mentions the assorted early deaths in the music world - Hendrix, Joplin. Al Wilson (Canned Heat), Jim Morrison, Mama Cass - to which the passenger replies "Oh maaaaaaan, not Jim!", (not Jimi!, etc.) for each one. Finally, the driver says "Not only them, but Jim Croce is dead too". To which the passenger says "Who?".

I also remember with fondness a concert that Cheech and Chong did on radio. Two bits stand out there as well. One concerned the two of them stoned, in a car, at an intersection, while Cheech in a psychedelic love-the-whole-world haze urged Chong to "look at the liiiiiiiiiiiights, man............don' walk, don' walk, don' walk, don' walk". A second bit was really more of a monologue in which Tommy Chong successfully persuaded all listeners that the reason why marijuana would never be legalized was because its strongest advocates were basically the very last people you'd want to have serving as your public advocates. "A lot of people say grass wrecks your mind and, and ,and, ruins your...........................memory, man. Well all I can say is, THEY'RE F***ED!". That quick summary of inept citizen advocacy for lost causes remains as true (and pathetically funny) today as it did over 30 years ago.


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## RHGraham (Nov 13, 2008)

Good god, I think I did sound for some of you guys...



:smile:


Just an opinion, but I don't think the Orange is gonna reach down very far, I would suspect it'll get pretty muddy in the low end once you push it, but I may be wrong.
If I was building an amp for bass specifically, 6550's would be on the top of the list, maybe fighting for position with kt88's.

I'd wring it out the way it is first and see what the bottem end is like before I got to deep into it. YMMV

I Miss Gilda... she was over the top funny.
Her, George Carlin, and Sam Kinison spent a lot of time in the tape deck of the gear van. Made the shot from Trois Rivers down to Montreal almost bearable.

We saved Cheech and Chong for the ride to Newfoundland.

:smile:


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## screamingdaisy (Oct 14, 2008)

http://www.youtube.com/watch?v=P0jBQjfNG14

You might have to turn up the volume...


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## RHGraham (Nov 13, 2008)

:smile: :smile: :smile:

To funny man.

Randal


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