Ultimate Hammond Conversions thread

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donzoid
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Re: Ultimate Hammond Conversions thread

Post by donzoid »

I had "hoped" to get this done by tonight's gig...alas, safety and the "honey-do" list got priority...but I did make some progress and hope to fire it up next week.

So, I ended up doing a lot of the power string in P2P. It's just plain easier with the restricted space available. I didn't have a 3 watt 2k2 so I strung two 4K2's in parallel. I put a 22/25 bypass cap on stage 2 'cause I like lotsa gain. I may try RJ's booster also, won't know until I get a chance to hear it.


I'll post voltages when I fire it up to check.
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darefugee
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push-pull to single-ended

Post by darefugee »

Can I use a typical push-pull output transformer in a single-ended amp, if I use only 1/2 the primary? I have some AO-29 transformers here and want to build a single-ended 6v6. If yes, I have to double the speaker impedance, right?

Does anyone have any practical experience doing this?
Thanks,

Roger
billc
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Re: push-pull to single-ended

Post by billc »

darefugee wrote:Can I use a typical push-pull output transformer in a single-ended amp, if I use only 1/2 the primary? I have some AO-29 transformers here and want to build a single-ended 6v6. If yes, I have to double the speaker impedance, right?

Does anyone have any practical experience doing this?
I've done it with a Hammond 125E universal OT but used the whole primary and they have multiple taps on the secondary so you can get the impedance right (did this in a 2 x 6V6 parallel SE build and it sounds good)...FWIW Hammond used to market these as suitable for SE or PP use and mine has been great for experimenting with both.
HOWEVER, from what I've read PP xfmrs generally do not work well at all in SE due to saturation and no air gap. The AO-29 xfmrs and Hammond organ xfmrs in general are REALLY nice and I'd save them for a PP build. Edcor will sell you a SE xfmr with suitable impedance and ratings for only about $20.
billc
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Re: Ultimate Hammond Conversions thread

Post by billc »

donzoid wrote:I had "hoped" to get this done by tonight's gig...alas, safety and the "honey-do" list got priority...but I did make some progress and hope to fire it up next week.

So, I ended up doing a lot of the power string in P2P. It's just plain easier with the restricted space available. I didn't have a 3 watt 2k2 so I strung two 4K2's in parallel. I put a 22/25 bypass cap on stage 2 'cause I like lotsa gain. I may try RJ's booster also, won't know until I get a chance to hear it.


I'll post voltages when I fire it up to check.
Looks good! I recently did a PA amp conversion and stuck with point-to-point wiring and really enjoyed the challenge, worked out well too as it sounds good and noise/hum are low...but that is probably more due to the good design and layout of the donor than my efforts ;-)
I have an AO-68 amp in the pipeline and hope to get started on it before too long, it is also PTP in a small chassis. The PA amp was good practice before tackling it as the PA chassis is huge....anyway the innards of the AO-68 look like this...

[img:1152:864]https://lh5.googleusercontent.com/-fIBQ ... 163837.jpg[/img]
eniam rognab
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Re: Ultimate Hammond Conversions thread

Post by eniam rognab »

ugh, no progress on my end.... way too much shit happening in my world, got hit by a car on my motorcycle thursday morning (his fault, illegal lane change), been laid up since.... im in one piece, and i have a lawyer working for me on a contingency basis, no obligation to me if we lose or anything.... the whole situation is bullshit!! why me?!!?!?! cop lady told me i did everything right, but still, im the one laid out on the road surface.. :evil:

anyway, i did manage to do a swirly-jobber on my chassis the other day though, looks kinda amateurish in the pic, but there is alot of movement and texture in person. i loooove it!! very "mother-of-pearly"

i changed my mind on using turrets on a circuit board. i found some really cool isolated chassis mount turrets, i cant wait, its gonna be soo badass but i need to do alot more planning (and drilling :evil: ) but i think its a gonna be worth it!

i like your build don!! how is it working for you? got any toanz? zener is doing its thang?
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lord preset
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Re: Ultimate Hammond Conversions thread

Post by lord preset »

More progress on my AO-39 to Lite IIb conversion. After sorting out some wiring errors the amp fired up OK but seemed excessivelly bright. After pouring over suggested tweaks and trying a bunch of them I got it a little better balanced bit still not right. Then I did what I should have done 1st a- try a different speaker. Doh.

In keeping with the cheapo theme I used a cabinet I previously built but decided not to use on an earlier project. I covered it leftover tolex and grill cloth. It has a ceramic Weber Blue 12 in it now. I am using the RCA power and rectifier tubes that came with the chassis and the best sounding 12ax7 I could find in my junk tube box. The control panel was an experiment with inkjet waterslide decals on the backside of acrylic with gold spray paint. Not entirely successful as the decal edges show through, but it's not as bad it seems in the pictures.

The reason I am not done is that once I got the amp in the cabinet and fired it up I am getting some nasty crackles that weren't there on the bench. The cracklings and sputtering starts with notes but can continue on its own after the note stops. I am assuming its a microphonic bad joint or possible an oscillation issue, but I don't have the patience to dig into it tonight.
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Last edited by lord preset on Thu May 08, 2014 2:52 pm, edited 1 time in total.
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donzoid
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Re: Ultimate Hammond Conversions thread

Post by donzoid »

Wow sorry to hear about that motorcycle adventure Neal. Yep, they are fun, but my surgeon calls them "donorcycles" so you are fortunate to be on the mend.

I quit owning and riding after a "72 stitch ride", 3 surgeries including pins and a bone graft and even then felt "blessed". Hey at least I didn't grind half my face off (full face helmet's serve their purpose!).
Thanks all for the comments. The PA chassis looks like a dream for space compared to this thing I'm workin' on! But now that I have the layout sussed out, I'm going to take the same stab at an 18watt stout using an identical chassis.

Preset that's a very nice looking amp and I'm sure with a little more chopsticking etc. it will sound as good as it looks. I hope mine turns out half that aesthetically pleasing! NO progress on mine yet this week, but it keeps calling my name from the other end of the room....it won't be much longer!
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lord preset
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Re: Ultimate Hammond Conversions thread

Post by lord preset »

Touched all the solder joints and the crackles are gone. So it's done done. Sounds good for medium gain rock from half up to dimed. Not much usable headroom but I guess that's the nature of the 18 watt design. Now that I've had my fun I will throw this up on Craigslist to see if anyone wants to live dangerously. "Yeppers, I done wired this all by mahself. Purfectly safe, yep.."
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lord preset
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Re: Ultimate Hammond Conversions thread

Post by lord preset »

...and a short sound clip. The amp is dimed using the guitar volume for cleans. Guitar is a Reverend Flatroc.
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eniam rognab
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Re: Ultimate Hammond Conversions thread

Post by eniam rognab »

finally, progress! since i have been laid up after being hit by a car on my motorcycle i have had some time to work on my baybaaaayy!

are all the holes lined up? no. do i care? no, this is my build and i want it to look homemade. i love how this is turning out!!
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xtian
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Re: Ultimate Hammond Conversions thread

Post by xtian »

I build and repair tube amps. http://amps.monkeymatic.com
eniam rognab
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Re: Ultimate Hammond Conversions thread

Post by eniam rognab »

hahaha, does that mean you like it?
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xtian
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Re: Ultimate Hammond Conversions thread

Post by xtian »

Yup. I think it is most metal.
I build and repair tube amps. http://amps.monkeymatic.com
eniam rognab
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Re: Ultimate Hammond Conversions thread

Post by eniam rognab »

hey thanks, uses alotta haahd-wayah, thats for sure, those nylock nuts are awesome and terrible at the same time, no threadlocker and you know their not going no wheres, but the installation was a beotch.

just got confirmation today that my school has entered this project into the california state fair again for me! now i REALLY need to get it done in time, but looks like all the fun stuff is just around the corner so *maybe* i can flow some solder on at least the PS end. still need to run to work real quick and grab a couple of my tools i need, plus a glob of thermal compound for the zeners.

luckily i have a schoolmate who is super smart and creates AMAZING word documents for his lab reports to work with me to create a best-of-show winning report. we are entered together in the fair so we would both be awarded and he would obviously get all the prize winnings and such since i am keeping the amp. wish us luck!

anyway enough of all that, im just super jazzed with my jazz hands flyin!
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Blackburn
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Re: Ultimate Hammond Conversions thread

Post by Blackburn »

Great looking build!

Have you accounted for tone loss due to lack of a circuit board? :P
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