Hammond AO-35 due tomorrow!

[premiumplus]

I've been a forum member for many years, but very rarely post. Mostly, I have just enjoyed reading all the great design and modification information that you all have put down, and I've completely enjoyed the ride...After reading all that I can find on the Hammond AO-35 I finally bought one, and it's supposed to be on the brown truck tomorrow afternoon. Should be a fun project. It looks like for not too much sweat I can have a very nice and quite capable guitar amp...and it should compliment my other Dr. Z amps quite nicely!
Not sure whether I want to make it a combo or a head just yet...but I'm excited to have the amp coming in. It looks very clean and was removed from a working organ. The tubes are mostly original from what I can see on the photos, so it may not have all that many hours on it.
The intent is to leave as much of the vintage componentry as I can intact, and just change out the preamp a bit. Should be a good time, wish me luck!

[dorrisant]

Good luck and happy building!!

Tony

[premiumplus]

Thanks, I really want to thank this forum for all the great info that I've picked up here over the years. You guys are great.

[eniam rognab]

hammond conversions are great! we require build pictures though

enjoy

[premiumplus]

I can make that happen...

[Bob S]

Sounds like a lot of fun.
I'll be interested cos I've got an old A035 chassis wanting some attention.
Good luck !

[M Fowler]

I had built a Carmen Ghia already so when I got my AO-35 chassis I made it into a Marshall Lite IIB instead, that amp is loud great transformers.

Before and after photos.

[premiumplus]

I had built a Carmen Ghia already so when I got my AO-35 chassis I made it into a Marshall Lite IIB instead, that amp is loud great transformers.

Before and after photos.

Nice work! It looks like you drilled out the rivets that held the tube sockets and board inside the chassis and then replaced it after mods with 4/40 or 6/32 screws and nuts. That looks like a tight chassis to try and work inside...

[M Fowler]

I tried to save all the sockets but that was hopeless Hammond did a great job of mechanically wrapping all the wires on those tube socket pins.

I removed the board and removed all the old components and then loaded the board with IIB components. Tried to keep it compact and neat.

The back panel is an old name plate from my job. Used the three existing holes to attach the back plate. Center hole was drilled for 1/4" speaker jack and it worked out well.

Mark

[Structo]

Looks nice Mark!

If you want to add some bling, those transformer bell ends are aluminum and can be polished real shiny.

At least on the amp I have.

The flux bands can also be taken down to the copper.

[M Fowler]

I saw what you did on one of your conversions, very nice Tom.

[billyoung]

I got two hammond chassis i am using one to try out different circuits

it has octal 9 pin and 7 pin socket so you can set up near anything in it

i am running a jtm 45 style preamp board in at moment, last tube i tried

was a 12bh7 push pull think i fried it too lol....just a wee bit more you lil

rascal. Its big was a 6v6 push pull with fairly high voltage. for my next

few tests i think i will need vvr or something buts it been very flexible

and useful. I know alot of lil push pull configurations I dont like... now.

i scrwed wood blocks to ends so it lives upside down on bench....inverted

flight. I probably would sell the extra one as i have a jtm45 chassis coming

and custom transformer being wound, so i got plenty of stuff. I am going to

do a torroidal power transformer which i got, and I can try different

outputs. think my hammonds might be ao-26s like 23 inch chassis with

raft of sockets, i gutted it and put LCR caps in for supply. I pulled the

12bh7 from junkbox and ran a hammond 125B so i did not cry when if just

cut out. I just broke down and bought a 125 E so i dont likely need the

125b only has few hours on it. I am stoked for next round of tests. going

to try 6aq5 s and 6ak5 s few others coming mullard and bugle boys.

orphan number you can get for low $. i built a 5 watt plexi like ten years ago

and sent it to one of billy gibbons guys, It was too loud and rattled my

windows in old house it was not what i was interested in but I learned about

alot of components i did like for certain functions in it. It was single ended,

but my gut told me push pull. My problem started when i got an H&K cream

machine about 15 years ago or more , I did not know what it was but I saw

tubes and it was $30. I soon discovered it had a push pull 12au7 tube amp

built in and it would drive the sh*t out of a 4x12. I looked at scematic which

had IC front end and I said to myself what would this sound like with a proper

tube front end, which idea has cost me more mney than i care to imagine.

leather covered heads and copper lined chassis, geshhhhhhhhh. I now

have a lot of free time and am still in search of my holy grail. I decided the

12au7 wasnt it, so now i am just trying different lil PP configs hoping to find

the "ONE". I have parts coming for at least another 3 or 4 more combos

and the hammond 125 series allows a lot of F ***ing about to Occur.

I called the 5 watt StudioPlex and people would say WHY ????????

Until they played it. It gave you the leslie west concept. when you hit a big

E chord you iit in yer ballz. Once again I am on the freaking trail of the

F**K*IN* grail. Shoot me Please. Joe Hardy a decent studio engineer

and producer now played it when they were tracking rythemean, said he
...
liked it alot but ............ after months of being insulted i realized by my

he was dead accurate, I just didnt see the circuit differences, which I now

hope to correct. When I started looking on net at the number of freaking

mini amps I was STUNNNED... wish i had had time to pursue it. I undestand

why it took ken fischer so long to complete amps. I had almost the perfect

tone I wanted but when i added one vintage cap it sounded so sweet, but it

got ghost notes only around the octave. I spent weeks trying to make

it unhaunted. I wanted the tone but not the issues. This time i have

rounded up real vintage mustard caps tested one in my shit guitar and O

my God what a lovely tone in the sweet spot. I am coninced that this time

the amp gods will not deny me. You know all these guys doing every form

of analysis and tests have still not bothered to run spectral analysis on signal

caps ....you can almost do it on pc now would yield you some data.

heck just get john mayall and the blues breakes and analyize those tracks.

People know an exceptional tone but I dont think they can differentiate the

differences in components. A nice amp is like a tailor made suit where every

detail is set to the player who its for, like stevie ray only like certain 12ax7s

in certain possition and when the tech ran out of em Stevie knew and called

him on it. Everyone seems to think link a jtm50 with tube rectifiers is it,

so its worth a bloody fortune, change minor components and see who can

actually tell. its a big surprise. Myself and an engineer friend set up a triamp

sorta filter playing with national chips called af 100 s .....jimmy work for

dinky dawson who had a super reputation. Any way we came up with a sort

of audio test puzzle , we took a complex af100 filter and it had a bunch of

knobs to adjust frequency amplotude and q etc. We set up some very

expensive silver plated multi signal toggle switches to switch the filter

from music source to square input into an oscilliscope. Now heres the

puzzle bit, a square wave can be approximated by a summation of a series of

sine waves ......so you listen to music say the bluesbreaker with the filter

perfectly set to flat then you switch over to test and you see a good square

wave with a nice pretty square corner, the you mix up all the knobs so its

not at all flat then you tell an audio or studio engineer set the sound back to

exactly to what you heard. This is a very difficult thing to due and the

square corners will be round if its off hardly any. So jimmy and I tested our

ears and he was better than I was but we were both pretty good. We used

Mc Itosh tube amps and jbl speakers so n excues there. We could not wait

to test Dinky as people like steely dan would pay him $3000 a day to rent

all his microphones ( several hand made studers calibrated by Willie Studer

himself) he would mike up things and set everything he did. To other he

was like a jedi master with his ears and equipment......Guess What ??????


Dinky could not even get anything that remotely ressembled a square after

tuning our af100 tone filters, in fact he was the worst one eDinver to try it.

Jimmy and I were just Fu**cking Dumbfounded, We never could explain it,

or any aspect of it. Yet as far as all the artists were concened he was the

Audio Master, in fact he taught others , mixing engineering and wrote for

mix magazine. I still cant reconcile any of it. But I can tell you he cant tell

a perfect flat unmolested signal and thats a tested scientific fact. In fact

we did not find really many pro s had a good ear ... good enough to adjust

a parametric eq to flat when it had no markings on knobs and middle was

not middle if you get my drift. However we did conclude its very subjective

and probably black magic. Anyway I hope I find the tone before I end up

5150 only long term.

bill young
half fast something or other

[vibratoking]

what just happened?

[premiumplus]

I got the amp this afternoon, it's super clean and has all original tubes. All marked "Hammond" and made in Holland and USA. Very cool! I'm going to reform the caps first, then bring it up and see if she'll work. I expect it will, then I can decide which schematic to begin following...there seems to be several versions out there so I'm going to ask for verification here first, and analyze the schematics I have. Hopefully somewhere in the middle lies the truth.

[M Fowler]

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