Transformers for a Dr.Z Route 66

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Transformers for a Dr.Z Route 66

Postby gilmour_pugliese » 05 Mar 2012, 19:37

Hi guys, I'm pretty interested to build a Route 66, but I don't know the specs of PT and OT...

So, anyone knows the specifications or some valid replacements from Hammond or other manufacturers?

I'm thinking to 1650PA and 290GX or LX... I'm right? :hmmm:
I've attached the schematic...
thanks :thumbsup
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Re: Transformers for a Dr.Z Route 66

Postby PokeyPete » 06 Mar 2012, 02:40

Let's critique your choice of power transformers:

The transformer on the schematic has three sets of secondary windings:
.....740VCT w/ 50V (assumed) tap; current not given
.....5V; current not given
.....6.3VCT, current not given

Your transformer choices:
290GX.....690vCT @ 150mA (no 50V tap); 6.3VCT @ 5A.....(no 5V winding)
290LX.....600VCT @ 230mA (no 50V tap); 6.3VCT @ 4A; 5V @ 2A

Looking at the tube manual we find that the 5AR4 has a heater requirement of 5V, 1.9A.
The heater requirements of the 6.3V tubes are....EF86 0.2A, 12AX7 0.3A (parallel), KT66 1.3A (each) for a total of 3.1A.

I didn't do extensive research but I saw this transformer while checking the Mojo site.

http://www.mojotone.com/amp-parts/amp-t ... ransformer

The MOJO761 has the following characteristics and would be a closer match. Like I said, I didn't look very hard. I'm sure
there are even better matches if you search for them.

.....724VCT @ 150mA, with a 52V tap
.....6.3V @ 4A
.....5V @ 4A

Hope this helps a little on your journey down hwy 66
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Re: Transformers for a Dr.Z Route 66

Postby gilmour_pugliese » 06 Mar 2012, 10:28

Thank you Pokeypete :mrgreen:

So:
-the power transformers from Hammond are not OK... According to your specifications, I've two choices: MOJO761, or give the specs to a manufacturer for a custom-wound PT... I've already used the second one for my Hiwatt DR504 clone :mrgreen:

-the OT question seems to be more simple... this page:
http://www.hammondmfg.com/1608.htm

suggests a 1650PA for a max 60W 6,6k push-pull ultralinear... but any thought?
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Re: Transformers for a Dr.Z Route 66

Postby gilmour_pugliese » 06 Mar 2012, 12:03

I've contacted an Italian manufacturer:
http://www.inmadout.com/index.asp

and here's his proposal for a Route66:

PT: 360V-50V-0-360V@200mA, 3,15-0-3,15V@6A, 5V@3A
OT: 8K with 40% taps (or 6.6k, as used in the past in UL applications), 4-8-16ohm

This set is pretty good, but with 10V in less in the PT... So, a bit of headroom loss, right?
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Re: Transformers for a Dr.Z Route 66

Postby mojah63 » 07 Mar 2012, 16:45

some info here:

viewtopic.php?f=2&t=14124


I'd be more concerned getting the output tranny right. They all sound different..
some over-wound some are under-wound ect...
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Re: Transformers for a Dr.Z Route 66

Postby PokeyPete » 07 Mar 2012, 21:12

gilmour_pugliese wrote:I've contacted an Italian manufacturer:
http://www.inmadout.com/index.asp

and here's his proposal for a Route66:

PT: 360V-50V-0-360V@200mA, 3,15-0-3,15V@6A, 5V@3A
OT: 8K with 40% taps (or 6.6k, as used in the past in UL applications), 4-8-16ohm

This set is pretty good, but with 10V in less in the PT... So, a bit of headroom loss, right?

Hi gil',
That set looks very nice. I've included a link to the KT66 from duncan amps. As you can see from
the chart they list the load resistor as being 8K when the KT66 is setup as normal tetrode; but when
set up as ultra-linear tetrode that the load resistor given is 7K. This would lead me to believe that
the OT from the set or the 1650PA would both be satisfactory in this build.

http://tdsl.duncanamps.com/dcigna/tubes ... t66-3h.gif

I'll include another link from duncan amps (just one layer above the link I just posted) so that you
can see the KT66 stats listed for different setups......tetrod, triode, etc.

http://tdsl.duncanamps.com/dcigna/tubes ... /kt66.html
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Re: Transformers for a Dr.Z Route 66

Postby gilmour_pugliese » 08 Mar 2012, 00:12

PokeyPete wrote:
gilmour_pugliese wrote:I've contacted an Italian manufacturer:
http://www.inmadout.com/index.asp

and here's his proposal for a Route66:

PT: 360V-50V-0-360V@200mA, 3,15-0-3,15V@6A, 5V@3A
OT: 8K with 40% taps (or 6.6k, as used in the past in UL applications), 4-8-16ohm

This set is pretty good, but with 10V in less in the PT... So, a bit of headroom loss, right?

Hi gil',
That set looks very nice. I've included a link to the KT66 from duncan amps. As you can see from
the chart they list the load resistor as being 8K when the KT66 is setup as normal tetrode; but when
set up as ultra-linear tetrode that the load resistor given is 7K. This would lead me to believe that
the OT from the set or the 1650PA would both be satisfactory in this build.

http://tdsl.duncanamps.com/dcigna/tubes ... t66-3h.gif

I'll include another link from duncan amps (just one layer above the link I just posted) so that you
can see the KT66 stats listed for different setups......tetrod, triode, etc.

http://tdsl.duncanamps.com/dcigna/tubes ... /kt66.html


thanks Pokeypete... I prefer the Inmadout option because the set has a resonable price (150€) and the manufacturer is italian (speak the same language is important in those cases). BTW, if I choose Inmadout I'll ask a 6.6/7k for OT :thumbsup
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Re: Transformers for a Dr.Z Route 66

Postby wyatt » 16 Mar 2012, 06:39

You'll probably find your filament village will drift closer to 7VAC because your only drawing 3.1A of current and it's spec'ed for 6.3V @ 6A. PT voltages are spec'ed under load; If the load is less than spec'ed, the voltages go up a little.

It's nothing major, but you'll want to check the filament voltage when the amp is built and running to see if you need to correct it down to 6.3V.
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Re: Transformers for a Dr.Z Route 66

Postby ukbrightonbloke » 30 Mar 2012, 12:10

I am currently building a hybrid route 66 with Maz preamp second channel. I looked at transformers and the closest I could come to without resporting to custom built was the following:

Power: Hammond 374BX 750V C.T.@ 201ma. 50v bias tap, 5V C.T. @ 3A, 6.3V C.T. @ 6A
OP: Hammond 1650HA 40watt, 6,600 ct, Push-Pull (2 Tubes), 6L6GC, 807, 5881, EL34

These are readily aailable

My only real concern is the PT is on the edge regarding current but as long as the hammonds can run hot it should be ok.

Thoughts please
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Re: Transformers for a Dr.Z Route 66

Postby PokeyPete » 01 Apr 2012, 10:02

ukbrightonbloke wrote:I am currently building a hybrid route 66 with Maz preamp second channel. I looked at transformers and the closest I could come to without resporting to custom built was the following:

Power: Hammond 374BX 750V C.T.@ 201ma. 50v bias tap, 5V C.T. @ 3A, 6.3V C.T. @ 6A
OP: Hammond 1650HA 40watt, 6,600 ct, Push-Pull (2 Tubes), 6L6GC, 807, 5881, EL34

These are readily aailable

My only real concern is the PT is on the edge regarding current but as long as the hammonds can run hot it should be ok.

Thoughts please

I am very curious to know how you came to the conclusion that "the PT is on the edge regarding current".
Please explain (and show your work).
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Re: Transformers for a Dr.Z Route 66

Postby ukbrightonbloke » 03 Apr 2012, 14:36

Hi Pokey Pete

Like most enthusiasts we get facts (debabtable) and figures from the internet or books. I know basic ohms law etc and thank god I have a calculator.

My work is research, and looking at other designs, datasheets etc and it looks like the current draw on 2 x kt66 in ultra linear mode is between 135 ma and 160ma depending on wattage output (30W - 50w). Adding in the smaller tubes, preamp & driver (I have 2 extra ecc33 tubes) I could be looking at about 175ma, add the desired 20% overhead prefered to not push transformer too hard, makes 210ma. The Hammond transformer is rated 201ma. I may be wrong but I believe Hammonds are not military spec and only have about 2% headroom which means I dont have much overhead.

Please by all means put me straight with this because it will make me stop worrying that my transformer may meltdown!

I have not been able to find a definitive answer to how much current a Rout 66 draws at peaks. I know we should not take everything we read as the truth, especially when looking to build a clone of an amp that dosent have any official plans or data of voltages, currents and tranformer specs.

(shhh dont tell Dr Z i am building one a MAZZ66)

Cheers
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Re: Transformers for a Dr.Z Route 66

Postby PokeyPete » 03 Apr 2012, 21:26

It seems like you have done your homework! :applause:

When you disclosed your transformer specs I thought it was a terrific selection. I even thought it was a little overkill,
but I liked that. If I were going to build a "66" amp, I would definately consider using it. The specs in one of the links
that I provided above uses a similar voltage and load resistor value as the schematic above. It gives a 145mA reading
at maximum signal level. In my mind I was thinking that pre power triodes had plate resistors in the 100k to 220k range
yielding only several hundred microamps to 1 or 2 milliamps per triode. It looked to me like it would take a lot of tubes
to use up all of that 56mA available headroom. That's why I asked you about it. I admit that I haven't looked at the MAZ
schematic so I don't know what is involved. You may be right about it being on the edge. But for the "66" it looks great!
My thinking is that unless the MAZ preamp is some kind of current hog you should be fine with this transformer. Hopefully
one of our "Amp Masters" will step forward and give you proper advice. Best of luck on your project! 8)
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if he takes no other counsel than his own. He that is taught
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Re: Transformers for a Dr.Z Route 66

Postby ukbrightonbloke » 05 Apr 2012, 09:45

Thanks Pete for feedback, this is what makes a good forum!

I feel much better about the hammond, i just wont turn it up to 11!

I will post my build pics and diy drawings soon.

Again, thanks and hope others find our post useful
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Re: Transformers for a Dr.Z Route 66

Postby ukbrightonbloke » 05 Apr 2012, 09:49

I forgot to add, if anyone uses the Hammond 374BX make sure you check the current. They changed it from 175ma to a 201ma version about a year half ago, so if you buy one, make sure its a later version rated at 201ma and some companies are still showing it as 175ma on their data sheets.

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Re: Transformers for a Dr.Z Route 66

Postby ukbrightonbloke » 10 Aug 2012, 18:23

P8080014.JPG
Thought you might like to see the build :)

Waiting for Tubes, then final testing

P8090023.JPG


The amp is a two channel with switching amp a Route 66 with a MAZ Junior channel added

WIll mess with some of the values to tweak it once tubes have arrived. So far no smoke!

Teh tramsformers are the hammonds I suggest in previous post.

CM
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Re: Transformers for a Dr.Z Route 66

Postby BaldPaul » 10 Aug 2012, 18:42

Looking good! I know you must be chomping at the bit the bit to get her tubed up and into testing. Best of luck and may the tone be with you!
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Re: Transformers for a Dr.Z Route 66

Postby ukbrightonbloke » 01 Oct 2012, 09:37

P9280010.JPG


Got the amp Tubed up with

Matched Pair Russian Genalex Gold Lions KT66
2 x JJ ECC83s (for maz channel)
1 x TUNGSOL EF806 (for 66 channel)
1 x TUNGSOL Re-Issue 12AX7 (phase splitter tested)
Sovtek 5AR4

The KT66's are massive! if you are going to use these in a project, make sure you leave airspace between them!

All from HOTROX in UK who have a great selection and so far a great service.

Had to tweek the bias supply resitors as couldnt get the bias violtage high enough to get the right bias, which i set at 37ma.

The amp spunds gorgeous, sparkle on the top ends with nice warm low end, and thats with a crappy 1x12 cab I have! Cant wait to get the new 2 x12 cab made up with a vintage 30 and one of the new 'celestion cream back' speakers.

The tranformers seem to be ok, need to push them for a while to see how warm they get.
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Re: Transformers for a Dr.Z Route 66

Postby PokeyPete » 13 Oct 2012, 14:32

ukbrightonbloke wrote:The tranformers seem to be ok, need to push them for a while to see how warm they get.

You did a terrific job with your amp build.....looks Wonderful !!!

You stated earlier that you were thinking that "the PT is on the edge", and apparently you are still
holding on to that belief. You've had a chance to crank it up a bit ( I assume ). Do you still have
reservations about this PT when adding the MAZ front end? I would love to hear a sound sample
featuring both MAZ and "66" inputs! Since the two amps normally use different power tubes, how
satisfied are you with the sound of the Maz? Would you mind showing us how you combined the
two preamps?
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Re: Transformers for a Dr.Z Route 66

Postby ukbrightonbloke » 31 Oct 2012, 11:00

Hi Pete, thanks for message.

I have cranked it and to be honest it seems all ok! the PT seems to be working fine and not getting hot, only warm from the massive gold lions (which are great!)

Here is the final schematic with switching and bias component change. I had to tweak the resistors in the bias circuitry to get the desired bias (38ma for me at mo)

mazz66-v2.JPG


The 66 chanel sounds pretty much like the 66 i tried at a local shop. the Mazz chanel sounds great too, harder than the 66, and much more like a jtm 45/plexi with kt66

I am waiting on the cab to be made for the amp and speaker (from cabs by chris, ampmaker)

will be fitting into this

TWEXPHeadcabgreenfrontview44.jpg


The cab will be based on the Drz 2 x 12 which has a mix of a vintage 30 celestion and a 12h greenback but i will be using the vintage 30 (50w) and one of the new creambacks (60w)

Hope all this info helps

Chris
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Re: Transformers for a Dr.Z Route 66

Postby snofla1900 » 31 Oct 2012, 14:44

Looks great!
What I like to do in fixed bias amps is make the biascontrol double and feed them to the 220 K gridresistors of the outputtubes so you can bias them seperately.

Could you perhaps post a soundclip ?
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