Upcoming project ---1954 Bassman Amps 5D6 circuit, almost!!

Ken Fox · From: Nashville GA USA

After working on and listening to Albert Talley's 1954 Bassman, 5D6 I have decided to build ten of these. The dual 5Y3 rectifier in the 5D6 Bassman was only made for a very short period. The later 5D6A and 5E6 used dual 5U4GB rectifier tubes.

So far I have decided on:

Mallory 150 caps
Sprague Atom filtering caps
JJ power tubes and 12AX7 tubes
Electro Harmonix 12AY7 tubes
NOS American 5Y3GT tubes!!!! (Sylvania and CBS)
Mercury Magnetics for all transformers and chokes
carbon comp resistors (except the 2 watt power resistors, Metal oxide)
Carling switches
Switchcraft jacks and plugs
CTS pots and 1 Alpha pot
Jensen P10R speakers with bells for the lower 2 speakers

cabinet with lacquer finish
Vintage cloth covered wire, like the originals

Slight mods to the original:

The original was a 2-hole chassis, single channel with 2 jacks. The one I am building will be schematically the same but with a second channel,
like the low power tweed Twin. The bias will also be adjustable. Also a grounded power cord will be used. Dark Brown chicken head knobs and an amber jewel.

Hopefully I will be starting on these amps or after Aug 3rd.

Any thoughts appreciated!!

Bill Duncan · From: Lenoir, North Carolina, USA

I hope they turn out great.

I suppose if one has to ask how much they cost you can't afford one?
_________________
You can observe a lot just by looking

Ken Fox · From: Nashville GA USA

I have been looking at offerings for Bassman clones and see they are as high as $2700 (Victoria amps) and as low as 1400. The amps at $1400 will not have the nicer cab, speakers and transformers.

I am shooting to stay in the $1800.00 range on the amps.

Bill Duncan · From: Lenoir, North Carolina, USA

Thanks Ken,
That isn't so bad.
_________________
You can observe a lot just by looking

J Fletcher · From: London,Ont,Canada

Hi Ken
How do these amps differ from the 5D6A and 5E6 amps? Just the rectifier and output transformer?
I know you couldn't duplicate the output transformer, but did you get any of it's specs? Turns ratio and physical dimensions?
Just curious as I've never seen one other than in your pics...Jerry

Ken Fox · From: Nashville GA USA

Mercury Magnetics has a 2 ohm, 2 hole transformer that will actually have a little more iron than the original output transformer. The orignanl was pretty light for a 2-6L6GC amp. Impedance is based on a 2 ohm output with a 2-6L6GC input.

The power transformer will be the same, except with a bias tap. The old 5D6 used the high voltage winding to get its bias.

The 5D6 tone circuit is different than the 5D6A or the 5E6.

There are a few other minor resistor differences here and there,

There were never any drawings of the 5D6 made. I made them based on Albert's amp.

I am not making an exact clone. If so the chassis would have to be custom made, a minimum of 300 pieces!! The 5E8A chassis layout is identical with the exception two extra input jacks and 1 extra 12AY7 tube for that extra channel.

Ben Jones · From: Seattle, Washington, USA

sounds really cool Ken.

what was it about that amp in particular that inspired you? I mean specifically hows it sound difffernt than the 59 bassman most are familiar with (at least in reissue form)?

what will you use for 5Y3's?

Ken Fox · From: Nashville GA USA

We will be using 5Y3 rectifers from Electro Harmonix. I have quite a few 5Y3 American tubes in stock I can compare to.

The tone is just unbelievable! I plugged it into a Super Reverb cab with 4 Alnico speakers after I finished the amp and all I can say is it was guitar heaven. I could play all night with no reverb or echo!!

I think the 5Y3 rectifiers make a difference. The voltage drop is 60 volts as opposed to 50 volts on the 5U4. I would think that would account for a difference in the sag of the amp.

I have a friend of a friend who had one and played harp thru it. He said it was a dream harp tone!!! He sold his when times were a bit tough. Here is a link to his 5D6 with a harp.

http://www.youtube.com/watch?v=1oiFsigLaO4

Ken Fox · From: Nashville GA USA

I am moving ahead on the parts. Ordered a large part of the items today. Will be order the cabinets, transformers and a few other small items tomorrow.

I added the Jensen bells for the two lower speakers, like the original amps.

I am considering a cover for the amps as well. A well made cover and no logo on it!!!

Ken Fox · From: Nashville GA USA

I am now set up as an OEM buyer for Jensen speakers. If anyone needs Jensen in the future, I can help out there as well.

Tomorrow I should have the balance of this ordered.

I can't wait to get the first one done!

I am still shooting for August, after we get back, to have the first ones ready to go.

Roger Crawford · From: Griffin, GA USA

No logo?

Ken Fox · From: Nashville GA USA

Now I like that!!! Actually I am trying to get a logo plate with similar lettering to the old Bassman that says: FOX VINTAGE AMP

I like the little fox! Maybe we could use him on the tube chart.

Bob Hoffnar · From: Austin, Tx

If you are into experimenting with them after a bit you might try out beefing up the transformer and using KT88 power tubes. I had a builder do that with a princeton clone and its the perfect sound for my ear.
_________________
Bob

Ken Fox · From: Nashville GA USA

The power transformer will have a little more iron for sure. I need it ti run cool, as I am powering 1 more 12AX7 than the original amp. Voltages will be the same as the early 1954-1955 amps for sure.

Got all the parts ordered today. Delivery will start on or after Aug 3rd.

Here is my aged tube chart, coming from Canada:
Address, phone number and email deleted to avoid spammers!

Ken Fox · From: Nashville GA USA

Here's my Tweed Pro, 5E5A clone I recently built. Uses the Mallory 150 caps, etc. Transformers were Heyboer. The speaker is a 12", instead of a 15".

This is the best sounding amp I have ever owned! It even out did my Blackface Super Reverb. The new amps will be hand-wired, cloth covered wire and very similar in look to this:

Jerry Erickson · From: Atlanta,IL 61723

Ken, You're inspiring me to get my Tweed Pro restored. It's either a 5C or 5D Pro that someone painted the tweed black a long time ago.

Ken Fox · From: Nashville GA USA

Albert's had been recovered in some sort of Tolex. Hopkins is the best at correct tweed amp cabinet restoration. Expect a 8-12 week turn around time! He still has Albert;s amp cab, hope it will be back to him soon. I know it will be perfect!!

We have all the parts scheduled for delivery now. I have also got the parts coming for 1 amp. That way I can test the fit and look of all the components. I hope to have the prototype up and running in about a week.

I have a 4-10 Tweed cabinet I just finished doing the tweed and finish on. We are making a Tweed Bassman, piggyback amp out of this first chassis!!
Ruth made some Tweed piping for the grill. I thought that was a nice twist!!

Mark MacKenzie · From: Franklin, Tennessee, USA

Ken, is that 39.6 ma bias on those 6L6's?

Ken Fox · From: Nashville GA USA

Yes it was. I do not run 70 percent as a lot of folks prescribe. I go by the actual plate voltage and use a spreadsheet to insert that and the tube types for my range of bias. The lower the plate voltage the higher that current will be.

Mark MacKenzie · From: Franklin, Tennessee, USA

Cool, Ken. I wasn't making any kind of critique, just wondered if you liked your tubes on the hot side or not. Wonder what your plate voltage is....

I bet your project will be awesome!

Ken Fox · From: Nashville GA USA

I generally stay around 32-35 ma with JJ tubes. You can go a lot higher when approaching the 70 percent rule. I just can't hear the advantage and I know that idle current wears tubes out faster.

I have set amps for harp players as low as 22 ma and they sounded fine as well!!

Finally got the last parts ordered. Today it was the Switchcraft lock nuts for the pots and jacks. If you buy a kit from folks on the net they never include those. I have made the effort to include a lot of things that you will not get in the typical kits amps that are on the net.

Ken Fox · From: Nashville GA USA

Got the prototype almost done. I am waiting on a bell cover for the Mercury Magnetics power transformer. They do not normally use a bell cover inside the amps but I want this like the originals and that was a must.
Waiting on a bit of hardware for mounting the transformers. No devices, circuit board or tube sockets will be mounted with sheet metal screws! The circuit board is mounted to the 6/32" x 1/4" standoffs which is mounted to the chassis with a 6/32" locking nut with plastic insert. Tube sockets are mounted with 4-40" screws and lock nuts. Transformers will be mounted with 8/32" screws and lock nuts.

Ben Jones · From: Seattle, Washington, USA

VERY cool Ken!

"No devices, circuit board or tube sockets will be mounted with sheet metal screws!"

-why no screws for the board?

Ken Fox · From: Nashville GA USA

I prefer the 6/32" x 1/4" stand-off. The current production replacement circuit board screws for the old Fender amps are available from Mojotone. The threads are so soft that the slightest torque will strip of the threads. Just junk!!
The stand-off holds the insulating board against the chassis and allow just the right space for all the cloth covered wires running under the board. The old amps often had broken top boards from the over tightening of the old sheet metal screws. This will not occur with this method. It is more expensive but worth the cost.

The 1954 Bassman amp used 4-40" screws and nuts for the tube sockets. It also used 8-32" screws and nuts for transformers and choke mounting.

Ben Jones · From: Seattle, Washington, USA

interesting. Thanks. I found those self tapping screws holding the boards kind of a weak point in the design myself, but I guess they allowed fender to assemble em quickly and they didnt have to pay for nuts and washers and standoffs. what your doing seems like a logical "upgrade".

Forum Index > Electronics	Goto page 1, 2, 3 Next	Next oldest topic :: Next newest topic