AO-35 Rocket

[xk49w]

I have started an AO-35 based Rocket build and was planning to use 6V6s. I measured the OPT and it appears to have a turns ratio of 29. With an 8 ohm load this gives about a 6.7k ohm primary impedance. What other tubes can I safely try with this transformer? Unfortunately KT66 won't fit - there is not enough room between the octal sockets.

The OPT is not very massive and I expect it won't have a lot of bass control of the cone. This will be a single twelve combo. I have an old Jensen P12N organ pull and a Jensen P12P (church PA pull). I will try them all out but I was just curious if anyone had any opinion on how either of these will do in a Rocket style? I am also considering a Cannabis Rex if the Jensens can't cut it. Thanks in advance,

-- Bradley.

[CaseyJones]

I have started an AO-35 based Rocket build and was planning to use 6V6s. I measured the OPT and it appears to have a turns ratio of 29. With an 8 ohm load this gives about a 6.7k ohm primary impedance. What other tubes can I safely try with this transformer? Unfortunately KT66 won't fit - there is not enough room between the octal sockets.

What other tubes can you safely use with that OT? ALMOST NONE. Your choices are limited by the current limit of the OT, beyond that it forms a small mushroom cloud and the fun's all over.

Your choices are 6V6s or 7408s then a whole bunch of 9 pin minis like 6CM6, 6BQ5, ECL86, 7189, 6973, then 6AQ5 or equivalent in 7 pin mini. Which come to think of it are quite a few choices. Just don't go crazy and try KT66s, EL34s or 6550s, that's more than the PT wants to push and more than the OT wants to push through. The PT will handle 6L6s. Barely.

The OPT is not very massive and I expect it won't have a lot of bass control of the cone.

Wrong-O. It's big enough for 6V6s. Big enough to reproduce pedal tones an octave lower than your guitar in other Hammond amps.

This will be a single twelve combo. I have an old Jensen P12N organ pull and a Jensen P12P (church PA pull). I will try them all out but I was just curious if anyone had any opinion on how either of these will do in a Rocket style? I am also considering a Cannabis Rex if the Jensens can't cut it.

I can't believe some people. They got a chicken in the pot and they want duck.

That parts combination is just about perfect for any number of vintage flavored amps. The alnico speaker suggests to me something pre-'62 or so. You have all the parts for a tweed Deluxe, a brown Deluxe, even a Princeton reverb.

Ampeg Jet, sub 12AX7s for 6SL7s.

Gibson GA-18. Your OT is way better than the wimpy Gibby OT ever was.

Lite II, Spitfire clone, buy an EF86 and buld an AC-15. AC-15 w/ vintage alnico Jensen... now that's cool!

[loctal]

I can see two main problems to over come with your Rocket build.
Firstly, your B+ will be way too high. Rockets have about 100V +/- 5 on V1.
Secondly, the AO-35 chassis is very small and you still need to add a tube socket to the deal.
Remember your time is worth something. You could sell your AO-35 to someone who wants to clone a ghia and the speakers fender fan and then buy the correct transformers and chassis. This could save enough work to finish your goal in a timely mannor.

[skyboltone]

I can see two main problems to over come with your Rocket build.
Firstly, your B+ will be way too high. Rockets have about 100V +/- 5 on V1.
Secondly, the AO-35 chassis is very small and you still need to add a tube socket to the deal.
Remember your time is worth something. You could sell your AO-35 to someone who wants to clone a ghia and the speakers fender fan and then buy the correct transformers and chassis. This could save enough work to finish your goal in a timely mannor.

I have murdered two AO-35s and will not kill another. I would sell it on The Organ Forum and let folks install it in a B3/A100 where it belongs. I sent both the PT and the OT to Mercury and he has the specs. The PT is waaaay soft compared to most guitar amps. The secondary HV taps measure 260 ohms or so end to end. Both Ao-35 OT that I measured were spot on 8K primary. That's what MM came up with too. That doesn't mean that your's doesn't measure 29 but I've found that Hammond Organ OTs intended for EL-84 range from 7200 to 8000 ohms. As has been stated this is not a suitable rocket platform. It was the starting point for the Ghia, Matchless Spitfire, and Goodsell super 17. I built one liverpool two tube clone and one sorta bastard brown deluxe with the two and both owners are happy but there are a million other ways to get there. An A0-29 is a far more plentiful and cheap and has a 10,500 primary laydown OT just like the AO-35 and is a larger chassis to boot; but once again the PT voltage is waay too high for a Rocket. In fact it's perfect for a Tweed deluxe as long as you stick with the 5U4 rectifier. The PT is 375-0-375 at about 140ma even though it's huge, it's pretty soft. I got probably three of those PT around. I think that all of the OT from that era will work really well for guitar. The 7200 primary ones are found on just about any EL-84 Hammond Chassis except the AO-35. I've used a ton of them. In fact Abstact has one on his mini express.

[CaseyJones]

These were fun back when you could buy them for $20-$30 each, $80 to well over a "C" note is the norm now. There are cheaper ways to get good transformers...

I'm gonna laaaaugh when they go over $200 each...

[skyboltone]

You want some bitchin iron look for an AO-68. They don't come up often but they used a pair of 7591s cathode biased into 8800 ohms on a 30 watt core. The PT is also 375-0-375 but way stiffer. It will drive a pair of EL-34s.

Use that OT for a pair of EL-84 and now you're stylin'. Big iron big smooth sound. Phil at heyboer is makin' me some right now as a matter of fact. I've told him to tear it to pieces to get at the essential "it" of it. Stay tuned for price and availability.

Here's an AO-29. The seller of course has lost his freaking mind. But some buyer probably will too. $25.00 max on these.
http://cgi.ebay.com/1966-Hammond-Organ- ... 7C294%3A50

[Structo]

Yeah, I saw that earlier, but he is offering free shipping which is probably at least $30 in the states.

[CaseyJones]

You want some bitchin iron look for an AO-68. They don't come up often but they used a pair of 7591s cathode biased into 8800 ohms on a 30 watt core. The PT is also 375-0-375 but way stiffer. It will drive a pair of EL-34s.

I get all confused between the "E" amp and the "H" amp. One has an onboard power supply, multiple secondaries. One secondary/ one rectifier feeds the main amp w/ 7591s, the other secondary/ other recto feeds the onboard reverb amp. It's like a main amp and an AO-44 on the same chassis. I was wondering what the hell I was gonna do wif that PT, eventually I figured it out...

Then there's that other amp w/ 7591s, outboard power supply. Dual 5AR4 rectifiers. If you ever dreamed of a 100 watt Marshall with tube rectifiers... there ya go!

Here's an AO-29. The seller of course has lost his freaking mind. But some buyer probably will too. $25.00 max on these.

Crack baby, crack baby, go get a clue...

Doo ron ron ron, Doo ron ron!

The seller obviously needs the money to buy more drugs.

No tubes, either. Them'r some bad drugs there....

[skyboltone]

You want some bitchin iron look for an AO-68. They don't come up often but they used a pair of 7591s cathode biased into 8800 ohms on a 30 watt core. The PT is also 375-0-375 but way stiffer. It will drive a pair of EL-34s.

I get all confused between the "E" amp and the "H" amp. One has an onboard power supply, multiple secondaries. One secondary/ one rectifier feeds the main amp w/ 7591s, the other secondary/ other recto feeds the onboard reverb amp. It's like a main amp and an AO-44 on the same chassis. I was wondering what the hell I was gonna do wif that PT, eventually I figured it out...

Then there's that other amp w/ 7591s, outboard power supply. Dual 5AR4 rectifiers. If you ever dreamed of a 100 watt Marshall with tube rectifiers... there ya go!

I got one of each. The one with the onboard supply and only a pair of 7591s is the AO-68. The one with the outboard supply and the giganto PT has a pair of 7591s FIXED BIAS into a monster 6K primary OT and two pair of 6BQ5 amps with identical 7.2k OT. I ferget the AO# I'll check it out next time I get to the shop. I think I paid $25 for it.

I think that the E amp is in the tone cabinet. Early (1939-1941) had two 2A3 amps in the tone cab and a pre without HV supply in the consol. The connector cord sends 300VDC back from the tone cab to power the plates in the consol. Post war Es used and identical chassis but 6V6s instead. Like this:
[img:640:480]http://i414.photobucket.com/albums/pp22 ... G_0700.jpg[/img]
It's a shame but E types get parted out all the time because the tonewheel generator drive is pretty finicky, but they are a really cool sound. Like a B3 I'm told, but kinda greasy and pre-leslie heavy baby. Guys are now reclaiming them when they show up and hooking them up to 122/147 cabs. Some of the very last were made in Canada and had a power amp in the tone cab with 6550s in them. Says "Northern Electric" on the chassis. Same font as "Western Electric". Hmmmm. I'd like to find one of them.

[Ron Worley]

Crack baby, crack baby, go get a clue...

Doo ron ron ron, Doo ron ron!

The seller obviously needs the money to buy more drugs.

No tubes, either. Them'r some bad drugs there....

Casey, Ya tryin to get me to do crack???

[CaseyJones]

I think that the E amp is in the tone cabinet. Early (1939-1941) had two 2A3 amps in the tone cab and a pre without HV supply in the consol. The connector cord sends 300VDC back from the tone cab to power the plates in the consol. Post war Es used and identical chassis but 6V6s instead.

It's a shame but E types get parted out all the time because the tonewheel generator drive is pretty finicky, but they are a really cool sound. Like a B3 I'm told, but kinda greasy and pre-leslie heavy baby. Guys are now reclaiming them when they show up and hooking them up to 122/147 cabs. Some of the very last were made in Canada and had a power amp in the tone cab with 6550s in them. Says "Northern Electric" on the chassis. Same font as "Western Electric". Hmmmm. I'd like to find one of them.

There's a later "E" model console, an "H" model console, of course "A", "B", "C", "D" and "L" models. It's too bad the heyday of this stuff was around '65 or so, all the old techs are dead and buried. No joke! Call up Hammond/Suzuki and part after part comes up "NLA".

Crack baby, crack baby, go get a clue...

Doo ron ron ron, Doo ron ron!

The seller obviously needs the money to buy more drugs.

No tubes, either. Them'r some bad drugs there....

Casey, Ya tryin to get me to do crack???

Oh, no. I wouldn't consider it. There's only one kind o' crack I like, that's the crack on one o' those Canadian strip show queens.