ODS 6V6 build?

[Smokebreak]

This is my introduction to Dumble world and I wanted to get some feedback on a build I'm plotting. I've got a Bogen CHA20 chassis/iron. Schem:http://www.webphix.com/schematic%20heav ... cha-20.pdf

Apparently PT is 820CT 70ma, 6AX5 rectifier, 2.7ma filament current, with around 450 plates. I would have to add a 12AX7. I think filament and HT current draw will be ok, but I'm not positive.

If I go SS rect, I would expect 500V plates. This seems a bit high for the circuits and for 6V6, so I was thinking about keeping the 6AX5 rectifier. I'm also thinking about cathode bias 6L6. Do you think I could get away with SS rect if I cathode bias? I believe Fuchs had a cathode biased Dumble type.

I'm thinking I'll do the #183 without the relays.

Edit: the 70ma rating I stated for PT is actually listed after the rectifier on the schematic, so wouldn't the PT be rated higher, taking into account 6AX5 draw?
I'd appreciate any feedback on my ideas or anything I've grossly overlooked.

Thanks, J

[Smokebreak]

filament current draw

2 X 12axy =.6a
6AX5 = 1.2a
2 X 6V6= .9
=2.7ma

I'm hoping that the 2.7a current draw I got off the internet was someone simply adding up what the filaments are drawing, and not the actual rating of PT winding. I see the Carolina blues special(built in same Bogen) used 2 other tubes for vibrato/verb, so I'm thinking filament draw should be fine? Whats another 300ma?

[ToneMerc]

I'm thinking I'll do the #183 without the relays.

My 2 cents, if you don't follow the core topology then its not an ODS. 183 is just a high plate skyliner, no LNFB, small snubber on V2, 250K drive/level pots, Marshall output iron and El34 tubes.

Why reinvent wheel, a 6V6 D'Lite is well documented.

TM

[10thTx]

I'm the guy that gave that Bogen schematic to Schematic Heaven yrs ago.
And I'm the guy that came up with the Carolina Blues Special (still one of my favorite amps).

So, I am familiar with the Bogen and the unusual layout that goes with it.

I don't think you will be successful installing a cathode biased ODS in that Bogen chassis? My best guess is the layout will be problematic and you will oscillation problems?

I built this "Double C" amp for my friend, Chip out of the exact same Bogen you're considering converting. Chip wanted a Hammond trannie so he could use a 5Y3GT, so the PT got converted. However, you could still do this with the Bogen PT, IMO. Since the Hammond trannie is stand up vs. laying down, it does allow more room.

You could consider swapping Bogen PT for this one (als0 stand up) which is reasonably priced:

http://www.ebay.com/itm/PT275-2i-USA-PO ... 232eb2faa2

BTW, with the Bogen PT ........... I typically get 476 volts on the 6V6 plates. I have done 3 of that model Bogen conversions. With the solid state rectifier, I think you would be pushing 560v on the plates. 1.4 X 410 = 574

Please also note that the first filter cap on the 6AX5 rectifier should be 10uf but that you can use larger filter caps after that one.

Anyhow, my friend Chip is happy with the amp and uses it for practice at home. I think he's a really good player and opened up for Dave Matthews once and also Derek Trucks once.

Here is a "one take" soundclip of the Double C amp (Bogen conversion):

http://www.soundclick.com/player/single ... i&newref=1

You can see that the Double C amp (very) loosely borrows from Dumblish topology.

IF you truly want an ODS build it right and skip using the Bogen chassis, IMO.


With respect, 10thtx

[Smokebreak]

Thanks a bunch guys, this is exactly the information I was looking for. The D'lite and Double C look great! The CBS looks cool too...that was what I was looking at when I first started researching this Bogen. I was delighted to see it up on SH. Nice work. Thanks for the tips on the Bogen iron and 6AX5. I figure if I'm gonna start swapping iron in an old chassis, I might as well start scratch , so I'll use the Bogen iron and see what happens, and get to a true ODS at some other time.
Thanks again,
J

[10thTx]

Well, ............. IF you're starting from "scratch" using the Bogen iron.......

Another option IF you are interested in a D-style influence but having a lower wattage (14 watts) cathode biased amp is the Tweed BluezMeister.

I built this into an 18w tweed style chassis and used cathode biasing hence the name. It has relay switching.

Here are a couple of sound bits that give some idea of the tone of the TBM:

OD engaged:
http://www.soundclick.com/player/single ... i&newref=1

Clean to OD:
http://www.soundclick.com/player/single ... i&newref=1

There is a bunch of schematic and layout info here:

http://www.el34world.com/Forum/index.php?topic=9498.0

And Hoffman sells boards for the TBM also along with relay power supply boards and relay boards. His boards don't have the FX on board.

With respect, 10thtx

[Smokebreak]

Cool. That's another good option. I like the OD tone in the clip. I've got term strips, new sockets in, PT tests OK(I was worried it was untested from eBay), and managed to get 8 pots and 3 switches across the front. I need to sit down and examine the options.
Concerning the 6AX5, no need for a standby, eh?
I'm gonna use the bogen PT and I figure that 6AX5 will get my voltage as low as I can get it and it's only 1.2a filament current.
Side note: do you have one of those neat original speaker plugs Bogen and others used? One came with another small Bogen i have and I just think its the neatest thing...for no other reason than I was unfamiliar with them...

[Smokebreak]

Ok I finished my 20W D'lite in the Bogen chassis. My goal here was to quickly and inexpensively build something at least "Dumble-esque" to see if I wanted to do a proper build. Well, I'm sold. I'm really diggin the tones. I ended up having to swap PTs as my 6AX5 seemed to have a short, so I had to go SS to get it goin, and had 570v on the plates. Some cheap Chinese tubes actually took that up to a point before redplating , but they never died. I swapped in Webers GP transformer, and got correct voltages.

Anyways, I'd like to build a 50w D'lite version, and I'm hoping some of you can help steer me in the right direction. I've got a blank 16x8x2 chassis, and some blank boards. What kind of transformers do you guys like for this build? EL34 vs 6L6? I discovered the tweeked layout so I imagine I'll work off that.

Thanks a bunch,
J

[rock_mumbles]

A 50 watt would use iron equivalent to what would be used in a Bassman, some people use 50w Marshall PT's.

I recently built a 33 watt D'Lite pretty much to the "Tweaked" schematic using a 16 x 8 x2 chassis as a practice D-styled amp ... it was pretty tight but turned out to be a nice amp without any issues. I used components I had around to build it ... so it doesn't have 'proper' resistors.

I used an undersized but high voltage PT (high voltage Mercury Deluxe) so I'm using china 6L6GB (~20 watt dissipation tubes) and a BrownNote 22/33 D'Lite OT (Vibrolux) ... the PT gets warm when on for four hours but not overly hot.

Built with a larger Bassman PT in a 16 x 8 x 2 chassis it would even be a tighter build.

Here's a gut shot, the amp is only used in OD mode so later I added the PAB relay ...

[img960]http://rh-tech.org/public/D-Lite_22/D-Lite_33_Guts.jpg[/img]

[M Fowler]

Normster built this dlite circuit into a 16x8x2 Hammond chassis years ago and is an easy project last photo.

I built mine into a blank Princeton chassis and head cab. Used JCM800 iron.

[Smokebreak]

Ok that helps a lot. Great looking builds!

Are you guys liking ~450~460 plates? Here is what I've narrowed down my options to:

Bassman 330-0-330 w/ biashttp://www.classictone.net/40-18006.html
Vibrolux 4K OThttp://www.classictone.net/40-18005.pdf

Edcor 300-0-300http://www.rjguitars.net/Digital_Images/EM0726_PT.jpg
Edcor 320-0-320http://www.rjguitars.net/Digital_Images/EM0731_PT.jpg
Edcor 5K OT[url] http://www.rjguitars.net/Digital_Images/EM0806_OT.jpg

The first set seems pretty straightforward, and the second, with the Edcors...I feel like I'm never sure what I'm going to end up with because of their loaded ratings, and how much I'll load them. Would you go with the 600CT or 640CT? They don't have a bias tap but that's not really a big deal.

[Smokebreak]

I went with Hammond 290DX and 1750M.

Concerning PT placement, does it matter which way the flux band is facing?
i.e. for laydown PT does it matter which position it is oriented in? Space is a concern. I've seen them both ways so just wanted to check if one is more desirable than the other.

Edit: also, concerning the filter caps, why go to the trouble of series caps for the reservoir, then have the next cap after the 500R 10W only rated at @450V? V drop is not going to be that much...Why not do 1 reservoir at 500V, and the next 2 at 500V also?

[rock_mumbles]

I put my PT oriented with the long direction across the chassis as I needed as much room as possible for the boards ... my power supply board is elevated over the PT mounting bolts etc.

[M Fowler]

You can see I used the same cap board layout but used IC caps rated at 500v on my build.

I don't see a problem with using 450v caps especially since I have many times. The voltage inrush from first turning the amp on hits the reservoir with slightly more then 450 volts so the series caps handle that just fine. B+2 voltage is settled down by the time it hits this cap rated 450v.

I could be wrong but I have not had a problem.

Mark

[Structo]

I think around 425v-450v is where most ODS type amps have their power tube plates.
My 100w ODS sits right around 434v.

The reservoir caps (the first two big ones) are in series so you add the voltage rating but halve the capacitance.
So if you have two 100uF 350v caps, it comes out to 50uF and 700v rating.
So that is fine for the surge voltage.

The two main caps should come before the standby switch so they charge when the power is applied.

One thing to think about is there is a difference in the way a 50w ODS is tuned, compared to a 100w variant.

Things like cathode bypass and coupling caps can all be tweaked to your taste.

My first build was a Brown Note D'lite 44w amp kit.

But everyone keeps telling me that the 100w version is the one to go for.
So I did and have no regrets at all.
Sometimes more is better all the way around.