To boldly go, where I haven't gone before....

[digi2t]

Well, I must admit, although I'm a hard core solid state amp guy, tube based effects have always peaked my curiosity somewhat. It all started with my first multi effect that I ever bought, a Digitech RP-7. It had an 12AX7 in the preamp section, that for some patches, sounded pretty gosh darn good.

Now, Faustone has gone and pushed me to the point where I would like to try and build something tube based. In particular, their Valve Klipper. The guys over there are even righteous enough to supply schematics for their effects (both of them, and one amp), so I thought I would give it a bash.

What I really need is some input from some tube gurus. Specifically, where the transformer is concerned. I'm not quite sure what kind of current demand this circuit will require, and on their web site, they state that the transformer used in the Klipper is a custom job. Here is the circuit;



After scouring the net for a suitable transformer, I came across this on Ebay;



The input is 115/230, and the outputs are;
260-230-0-230-260 (90mA). - Got the 230v here.
2.5-0-2.5 (3A). - Not needed.
3.15-0-3.15 X2 (3A). - For the tube heaters.

So, it looks to be a winner to me, fulfilling the required 230vac, and two 3.15vac outputs required, voltage-wise. But, do you think it can supply enough current for this circuit?

Thanks guys!

EDIT: I realize that there are outputs on the transformer that will not be used, but it's the only one I can find with 230v and 3.15v outputs. I've seen some others with (only) higher (250-265v), and lower (170v) than 230v, but I would prefer to stay true to the schematic.

[Govmnt_Lacky]

Regardless of where you journey takes you Dino.....

Im confident that it will be exciting and the outcome will be EPIC!!!

Good luck bro!  I have been itching to build a tube amp myself. I have the PCB layout for my Valveking 112 and have been debating on whether or not to try a reproduction 

[digi2t]

Regardless of where you journey takes you Dino.....

Im confident that it will be exciting and the outcome will be EPIC!!!

Good luck bro!  I have been itching to build a tube amp myself. I have the PCB layout for my Valveking 112 and have been debating on whether or not to try a reproduction 

Yeah, I've thought about building a tube amp too, but I figured a pedal would be the best place to get my feet wet... before I lick the high voltage line.

[GibsonGM]

2 heaters in parallel = .6A, your trafo can source 3A.  Good.

The tubes themselves are running at (far) less than 10mA!   Tube circuits use high voltages with low current draws (generally speaking).  In a nutshell, you have WAY more ampacity than you need )

Don't know how good the trafo you're looking at is....if you want to go further down the tube road and reuse it, you might look at Hammond's offerings, they are very nice.  If that one is a good price and you're just experimenting, then hey - I'd go for it, knowing I may have to buy better for a later build.  

Wonder why they're wasting a triode?  They could've used a single triode for V1.  Hmmm.  

I used to love the old RP-7!!!    

[digi2t]

Well, thanks for that Mike. I'm way out in noobs-ville where tubes are concerned, so I really didn't know what kind of current they required. It's nice to see that the transfo I've got in sight will fit the build (and then some).

Quite honestly, this transformer rings the register at $80 shipped (yeah... pretty steep!), but I've yet to find one that fits the bill voltage-wise. They're either higher, or lower, where the 230v is concerned, and/or the heater voltage is only 6.3v.

I've looked at some Hammond stuff as well, but I haven't come across something suitable yet. If you have a link for a 230/3.15/3.15 xfo, let me know. Can I run this circuit at a higher voltage, say 260v, or will I have to start playing with the resistors to bias it properly?

[PRR]

The raw B+ is 322V. The 2K drop resistors won't do much (as we'll see).

The first stage has a 150K plate resistor. 320V/150K is 2mA if the tube is dead-short. Which would be stupid. Better bet is to assume the tube splits the 320V with the 150K resistor. This leads to 160V/150K or 1mA. A bit of g-amp experience says even less, so under 1mA.

The second stage is strange. There is a 47K+22K voltage-divider, though not drawn to call attention to that fact. This alone is 69K, across 320V, is 4.6mA. The tube sucks additional current, If it sucked very hard we'd have nearly 320V across 47K or 6.8mA, with almost no voltage for the tube. Which is unlikely. Without further insight we might pencil 5.5mA here.

1mA + 5.5mA = 7mA.

> 230-260 (90mA)

That's thirteen times bigger than you need.

(Another hint: 90mA will power two big 6V6 easily, and we don't even worry about the little-tube load when we have two big bottles.)

The 6V load is, as Mike says, 0.6A. 3A is five times more than you need.

If this fell out of the sky on your bench, you might use it. But EIGHTY bucks??

This lump is for a power amp (big bottles). You are making a preamp (small number of small bottles). Don't buy a Chevy V-8 for a lawnmower. (Yeah, there's guys who do... oddly they never have a mower deck...)

Don't worry too much about the high voltage. If it looks a bit high you increase the dropping resistors, IF you want. Most tube circuits are NOT fussy, even at +/-40% from nominal plate voltage. (Heaters should be +/-10%.)

Allied 6K27VF with a voltage-doubler will do the job:
http://www.alliedelec.com/search/productdetail.aspx?SKU=70009000
$15.

Allied 6K1VF can use the FWB supply and is a bit more generous:
http://www.alliedelec.com/search/productdetail.aspx?SKU=70008994
$18.

[GibsonGM]

Nice figures, Paul.   I got those too, but just rounded to "< 10mA" as I thought the 2nd stage was a bit funky, too!   
Either way, yeah - $80??
Dude, buy BOTH trafos that Paul just linked to, he he.   No need to get something that will do a whole amp for a small preamp...I assumed that would be much less - that price is REAL iron money.   I'd suggest, too, that you start to Immerse yourself in all things tube - build one of the smaller 9 to 40V jobs posted in here, too, if for nothing more than getting used to the calculations.

You cannot go wrong by reading everything available from Merlin. I got his preamp book, and it opened a lot of doors!   http://www.valvewizard.co.uk/

If you get 'close' with your transformers, you can either drop a little voltage, or simply live with the few extra volts.  But that's down the road, 'the tricks'....read read read read, about how to design a gain stage, first.   Load lines are where it's at!   When you can see a circuit and determine what its quiescent current is at its operating voltage, the rest of this will line up for you.   

[J0K3RX]

That's gonna make one canon ball of a pedal  

For these tube based pedals I have been hard leaning towards the nixie mainly because of price, size and easy to source the parts! $2.00 vs. $25.00 and the size and weight of a quarter...

If you have to go the transformer route I would use something like below and get to whatever voltage you need by various means... These work for most preamp designs.
$24.00 blue toroidal power transformer I think 15th down on the page.  Basically running it backwards, input 12V AC into the secondary's and output 240V AC from the primaries into a bridge rectifier..
http://www.hoffmanamps.com/MyStore/perlshop.cgi?action=template&thispage=Transformers&ORDER_ID=198158630

Details..
http://www.el34world.com/projects/tube_box_3.htm

[Derringer]

The second stage is strange.

so what is going on in V2 exactly?
I can recognize that the first triode of V2 is setup as a gain stage, but then how is it feeding the 2nd triode? What is that 2nd triode doing?

[davent]

A couple Hammond Flat Packs, the 229A12 for the heaters and a 229A230 for the high voltage.

http://ca.mouser.com/Search/Refine.aspx?N=4294759173&Keyword=546-229A12
http://ca.mouser.com/Search/Refine.aspx?Keyword=229a230

(From TUT5; Hotbox schematic.)

[J0K3RX]

A couple Hammond Flat Packs, the 229A12 for the heaters and a 229A230 for the high voltage.

http://ca.mouser.com/Search/Refine.aspx?N=4294759173&Keyword=546-229A12
http://ca.mouser.com/Search/Refine.aspx?Keyword=229a230

(From TUT5; Hotbox schematic.)

Thanks!! bookmarked those!

[jubal81]

Anyone got links for good 12V wall warts - AC or DC?

[kingswayguitar]

Anyone got links for good 12V wall warts - AC or DC?

i recycle them from old office telephones, handheld radio chargers, etc...

[Gus]

Look at PRRs post it was posted first
googled and found Laney Klipp amp schematics.  
one with voltages
http://www.prowessamplifiers.com/schematics/images/klipp_60.jpg
The Laney KLIPP 60 in the link shows 290VDC for the circuit section and 80VDC on the plate so we know PART of the current draw 80VDC/22k about 3.6ma
then we have 290VDC - 80VDC for 210VDC across the 47K  210VDC/47K about 4.5ma
next figure out the first stage current  You know just looking it will be less then 290VDC/150K

Looks like a LTP(long tale pair) but with a CF(cathode follower) like input.  The plate voltage of the 2nd triode is held kind of constant with the voltage divider and cap (R5, R6 and C4)
The current change in R10 changes the voltage drop and drives the 3rd triode grid.  R9 and C5 form a lowpass filter

I wonder why a 80VDC supply was not used for the distortion stage(a RC branch) and why this circuit was made to run the distortion stage at the lower voltage
need to work out the power supply interaction between the triodes
The 47K, 22k and cap  works kind of like a shunt regulator so the 80VDC should be more stable

[digi2t]

Firstly, thanks to Paul for the math. No, I don't want to go this route;



But, as I said before, with no tube experience at all, I really had no idea as to what kind of currents are being drawn by these beasties. Armed with this information, I promptly re-examined my transformer choice, and decided that the 6K1VF would be my first choice. But, Allied's shipping charge boosts the total to $40! In the end, I've spotted a model on EBay that provides 230v (0.037A), and 2 x 6.3v (1.5A each), for $35 shipped. Unfortunately, in my case, it's not the price of the transformer, but the shipping cost that's sucking rocks here.

So if I understand correctly, (I've been doing some homework here) can I use a virtual ground setup on the 6.3v side of things, to get two 3.15v lines? Like this;



or this (fancier fine tuning, but is it really necessary?);



According to the reading I've done so far (thank you Valve Wizard!), there are hum cancelling benefits to doing this, and the transformer has plenty enough current supply to overcome the 30 to 40mA loss to ground created by the resistors.

@ davent ; Interesting, but I'm really trying to keep the parts counts down, especially where transformers are concerned. As JokerX referenced, I would prefer a 6 lb cannonball, to a 12 lb cannonball. 

@ JokerX ; That's really cool! Tiny too. Powering the heaters seems to be the problem here though. I've looked at the diagrams that are linked to this xfo, but I really don't want to deviate from the Klippers schematic that much, i.e. diode bridge, regulator, etc. Seems to me that virtual ground on the 6.3v line would be the easiest solution. Besides, price comes to the same as the one I've found.     

Sidebar; Just found a Hammond 261C6 on EBay, the guy is asking $12.95, OBO. Again, shipping sucks at $20, but if he bites lower, still a better price.

[davent]

Hammond 262D12 with a voltage doubler for the HV. Various Canadian sources for around $30 plus shipping.

I always order Hammonds here. http://www.tiptopelectronics.com/home.asp?txtQuery=262d12

http://www.tiptopelectronics.com/home.asp?txtQuery=229a12
http://www.tiptopelectronics.com/home.asp?txtQuery=229a230

Never have the stock but usually receive the orders in acouple weeks. Hammond ships from near me to Winnipeg then Winnipeg en dss it back to where it started... go figure.

Electrosonic may have warehouse/office in Montreal.
http://www.e-sonic.com/acc/products.aspx?partID=262D6&partIDExt=195&command=detail

[davent]

You could try the 12vac wall wart to heaters & backwards wired 230/12 transformer, keeps the mains voltage out of your box.

Article here on the creative use of wall warts and how to power small tube projects.

http://audioxpress.com/files/2008/01/stamler2874.pdf

[armdnrdy]

I usually order wall adapters from Jameco.

The prices are decent.....but not sure about shipping charges to Canada.

http://www.jameco.com/webapp/wcs/stores/servlet/StoreCatalogDrillDownView?langId=-1&storeId=10001&catalogId=10001&categoryName=category_root&subCategoryName=Power%20Supplies%20%26%20Wall%20Adapters&category=45

[PRR]

> so what is going on in V2 exactly?

Exactly? It's a lifetime study.

But for practical purpose, it is the Long-Tail Phase Splitter in a form seen in many-many Fender amps. It is the last driver stage before the Big Bottles.

It is also known as Cathode-Coupled.

> first triode of V2 is setup as a gain stage

No-- the plate goes to a 16uFd capacitor, there is "no" signal there.

V2a is a cathode follower. V2b is a grounded-grid.

Here it is "odd" mostly because it is fed 90V instead of the 300V-440V we give it to smack the big bottles. Which makes sense because we are not doing such heavy lifting.

And because only one of the two outputs is used. (But we don't need a second output.)

A particular feature of the Long-Tail family is predictable and symmetrical clipping. This influences the way the big Fender amps go past overload to over-overload. Here they seem to be doing different tricks mixing the V2b output with the V1 output.

[Derringer]

Exactly? It's a lifetime study.

LOL

thank you PRR, I have some reading to do .... as usual