Open to thoughts and suggestionsHere are some random thoughts/ideas:
I don't like that amp. Here's the verified schematic...
QuoteOpen to thoughts and suggestionsHere are some random thoughts/ideas:[/list]
- A lot of amps use one pentode (or one per channel) in the preamp - usually in V1, sometimes in V2
- DanElectro did some multi pentode amps - one version of the Gibson EH-185 uses multiple strapped pentodes - I built one from a PA - Sluckey and PRR helped me a lot with that project
And I wish I could figure out how this bullet thing is supposed to work :w2:
- If you stick to one or two pentodes, there are good 7 pin triodes to play with 6c4, 6av7, 6at7
- It'd be fun to try the Clubman preamp using one of the above triodes for V1, and a 7 pin pentode for v2
And I'd considerer using the iron in a different chassis
IMO... The chassis is too narrow and long to be repurposed for guitar use. And I don't like that laydown OT. I'm sure the components are quality stuff just like all the other Hammond electronics.
I studied most of the Hammond amps and the AO-29 is the only one I shied away from.
And do you know for sure if the amp you have is NOT the Field Coil version? Take a look at this pic to be sure which one you have...
QuoteOpen to thoughts and suggestionsHere are some random thoughts/ideas:
- A lot of amps use one pentode (or one per channel) in the preamp - usually in V1, sometimes in V2
- DanElectro did some multi pentode amps - one version of the Gibson EH-185 uses multiple strapped pentodes - I built one from a PA - Sluckey and PRR helped me a lot with that project
And I wish I could figure out how this bullet thing is supposed to work :w2:
- If you stick to one or two pentodes, there are good 7 pin triodes to play with 6c4, 6av7, 6at7
- It'd be fun to try the Clubman preamp using one of the above triodes for V1, and a 7 pin pentode for v2
And I'd considerer using the iron in a different chassis
Open to thoughts and suggestionsHere are some random thoughts/ideas:
Thanks PRR and Shooter: I don't know if its the best way, but copy/pasting multiple pairs of symbols allows more than 2 bullets at the same level.Anyways - back to the subject - I have an AO-14D amp on the waiting shelf. Its pretty similar but all octal preamp and 2x6V6. I have no real plan yet but was going to pull the iron and other useful bits, giving the chassis to my neighbor scrapper. I imagine I am going to run into a similar situation - more PT than I want/need for the simple amps I usually build. Maybe I should use that for a 6L6 amp?
- This is the first bullet
- This is the second one
- and then I copy-pasted the symbols to get this bullet
- and this one
Amber, are you referring to a Bogen PA? model(s)?
That AO-14 appears to be an earlier version that predates the AO-29. Looks like it may have had a 340-0-340 PT and a field coil speaker?Yes, Thanks, I think you are right. I just found a service manual at medias.audiofanzine.com Do you have that? could be useful.
QuoteThat AO-14 appears to be an earlier version that predates the AO-29. Looks like it may have had a 340-0-340 PT and a field coil speaker?Yes, Thanks, I think you are right. I just found a service manual at medias.audiofanzine.com Do you have that? could be useful.
And thanks for the Bogen info - they had a lot of models!
Im not as keen as some of the other members here but every build ive seen (including mine) with an AO-29 wound up going to 6L6's because the available current on most of our designs threw the voltage WAY up and made using 6v6's impossible.
https://el34world.com/Forum/index.php?topic=20482.msg218508#msg218508 (https://el34world.com/Forum/index.php?topic=20482.msg218508#msg218508)
https://el34world.com/Forum/index.php?topic=24756.msg267559#msg267559 (https://el34world.com/Forum/index.php?topic=24756.msg267559#msg267559)
and others. Most just do it with the 6L6's.
On the schematic his PT is showing 340-0-340 which should be approximately the same as what I estimate I will get with 125V wall current.
Not sure how much it will drop with all the tubes loaded in.gueses;
I think I've seen at least one forum post where a guy sawed several inches off one end of one of these chassis to make it shorter. Still skinny, though.
I built a 6V6 Plexi using the AO-29 transformers a while back and ended up with about 420V B+ using the 5U4. It works ok with JJ 6V6s, it's been running for a couple years with no issues. I remember the heater windings being a bit high too...the PT is really not ideal but might as well use it if you've got it.I think I've seen at least one forum post where a guy sawed several inches off one end of one of these chassis to make it shorter. Still skinny, though.
That was me...it's not too bad if you're handy with an angle grinder. It turned out ok and it's a nice small amp, but it took a lot of planning to fit everything in there. I would suggest using a more appropriate chassis if you can.
Here's the schematic with my as-built voltages, hope this helps.
354V and 356V
Adrien, How did you treat the Green wire off the PT that was originally attached to the pedal volume switch? Did you just bolt it to the chassis?
Quote354V and 356V
OK, let's say 355-0-355 and you want to use 6V6's. These are my guesstimates
355 x 1.1 (5Y3GT) = 390v which would be fine with JJ 6V6's as well as many other brands.
355 x 1.2 (5V4 or 5U4GT) = 426v
As an FYI, I converted a Bogen yrs ago and it ran 476v on JJ 6V6's for 7 or 8 yrs with no problems. It was for a guy that plays mostly acoustic so it wasn't used for gigging out.
Tubenit
--{entire message above (https://el34world.com/Forum/index.php?topic=26618.msg291968#msg291968)}--
High Voltage - I and I'm sure others would be interested in hearing what B+ voltages you arrived at, and what methods you used to reduce voltage to appropriate 6V6 levels? I have a 14d waiting in the wings and I think that has the same PT, or similar, to the AO-29 PT for circuits with field coil speakers. I'll likely build a 6L6 amp, but tend to like lower voltage amps. Thankfully I live at the end of the electric service line so my house V is only 115-117 which helps a bit.
High Voltage - I and I'm sure others would be interested in hearing what B+ voltages you arrived at, and what methods you used to reduce voltage to appropriate 6V6 levels? I have a 14d waiting in the wings and I think that has the same PT, or similar, to the AO-29 PT for circuits with field coil speakers. I'll likely build a 6L6 amp, but tend to like lower voltage amps. Thankfully I live at the end of the electric service line so my house V is only 115-117 which helps a bit.
High Voltage - I and I'm sure others would be interested in hearing what B+ voltages you arrived at, and what methods you used to reduce voltage to appropriate 6V6 levels? I have a 14d waiting in the wings and I think that has the same PT, or similar, to the AO-29 PT for circuits with field coil speakers. I'll likely build a 6L6 amp, but tend to like lower voltage amps. Thankfully I live at the end of the electric service line so my house V is only 115-117 which helps a bit.
Sorry it looks like I misled you. I pulled them both out today and one is the 310-0-310 large-but-not-field-coil PT and the other is the small one the same as the OP (355-0-355). I do have a FC one as well but not yet converted.
Some thoughts for you. DaGeezer and I both thought the FAT triode was sort of a "set and forget" thing. It did add a little something but later I used the FAT triode as a cathode follower after the 5879 pentode. The CF after the 5879 helped smooth out the OD tone, IMO. * see attached schematic
The other thing was the 5654 paralleled with the 5879 was kind of an interesting feature. I used them paralleled, just the 5654 and just the 5879. After some time playing all those options, I thought the 5879 alone sounded the best.
The TOS is really not a clean to OD amp. It's more of a pushed mild OD tone to a strongly pushed OD tone.
DaGeezer and I viewed it as a tweakers amp. Something you built with the original design and then changed components and topology until it evolved to what you personally preferred.
With respect, Tubenit
For clarity …………. I am NOT saying you "should" change anything from your original schematic. Just offering some thoughts and considerations that may or may not be useful to you.
:thumbsup:
Keep us posted. I'll be following this with interest. With respect, Tubenit
Sorry it looks like I misled you.Thanks for following up. I'm likely a ways away from doing anything with that AO-14 as I have a few projects in front of it. I do have some 30W resistors though that should be useful to get the voltage down. Or maybe the thing is to run something else off it while playing - like a space heater. :laugh:
Thanks a bunch High Voltage. Like the voltage doc sheet. That is very useful. If its not too much trouble, would you mind sharing what your power supply section consists of? Did you use a choke or not and what dropping resistor values did you arrive at?