Help needed to find these rare values!
 

Hey guys,
I really need your help.
I want to build the following amp using a PF86 and EL84, but I'm having a lot of trouble to locate the following components in exotic brands :(

http://www.bonavolta.ch/hobby/en/audio/el84_2.htm

*10uF 400V, BG, Cerafine, MKP in Oil etc.
*220ohm 2W or higher, Dale RN series/wirewound in Al heatsink, Caddok etc.
*27nF 400V, Vitamin Q (prefered), West Cap, Jensen or any other PIO in US mil quality or in recent productions.

For 10uF, I can't locate any exotic 10uF electrolytic in 400V or higher. I don't want to use Solen/ASC(not in oil) Film caps, becase they would cost me a lot in that capacitance & voltage. I'd like to try ASC/SIEMENS MKP in oil if there's no such value available in electrolytic form, but I can't locate any in the MKP in Oil type.

For 27nF, I really want to try PIO, but I can't locate any in that capacitance of recent productions. All 27nF that I can find is Vitamin Q/West Cap/Gudeman in 200V. I also tried to find some plastic film ones but I also couldn't locate any in 27nF...:whazzat:

For 220 ohms 2W or more powerful resistor, I can't find any in 220 ohms @ that high wattage (of course, only in exotic). I want to try Dale (no ceramic), Caddok and some other brands, but I found very hard to find an exotic one in that value & wattage....

So,,,,,,
10uF--- What's the minimum possible voltage that I'm allowed to use? Is there any other capacitance suggeted?

27nF-- What's the minimum possible voltage that I'm allowed to use? Is there any other capacitance suggeted? Could I also use 22nF or is it too low to be substituted with?

220ohm @ 2W-- Is there any other resistance suggested? Would it be ok to use 200 ohms? I don't want to connect in series to achieve that value, because it would end up with costing me a lot.
I tried to find 1W resistor @ a resistance close to 440 ohms (for parallel connection), but I couldn't find any, close enough to that resistance.

Please help!!:bawling: :bawling:

PS: It is obvious to see that Frank & SY will help me a lot :D

Hi,

First of all, that's one place I'd really recommend using a filmcap.
It doesn't have to 10µF per se but can be either bigger or smaller, even composed of several small caps. Polyester cap would be a major improvement over the electrolytic already.

Surely something along those lines should be available in your country?

Doesn't have to be 27nF either, go for 47nF or 68nF. These are common values in the 400V range. Wima MKP should be fine already.

220R 2W is a standard E24 series value and should be available in a variety of common brandnames such as Philips, Dale, Vishay.
You best stick with the recommended value but you could put 2*110R 1W resistors in series if those are easier to come by.

Also the cathode bypass cap of the EF86 should be more like 47µF/25V or higher. Here a BG is impossible to beat.
Ditto for the EL84 bypass cap although 47µF should be ample.

I'd also put a 10K (carbonfilm 1/8W) gridstopper on the grid of the EF86 and a 1M gridleakresistor in // with the 470K (I'd recommend 100K Panasonic) pot.

Then there's the PS to consider also...

Hope this helps, ;)

When it comes to sourcing exotic parts, Frank will be a lot more helpful than me. I like to play with topologies- the intricacies of Caddock versus Vishay are somewhat lost on me. That said, for big HV caps to use as power supply or decoupling, I'm quite partial to motor start/run capacitors.

Hey James

Just get the thing working first. I would just go to jaycar and use their cheap parts first, then try a few "upgrades". There is a heap of snake oil out there, so be careful.

I have found DSE bipolar 50uF/50V electros to be quite good for cathode bypass caps.

Also you can definitely change a few things in the circuit if you want. For example, EF37A will slot straight in instead of EF86, 6V6 can be substituted for EL84 (check the Pd and screen voltage though) and you can use a dual 100K pot at the front end.

You could also try a little negative feedback around the circuit if you have enough gain to spare.

I know that it's important to test it out first, but I 've got no time and money to waste on those crappy components and then upgrade.
Components supplied by DSE, Jaycar, RS NZ, and Farnell aren't cheap at all!:smash:
Some resistors sold by them cannot even handle more than 200V.
I would spend the money to buy even better components rather than buying those un-cheap components to test out:whazzat:

Would it fit there without any prob? Then I should try out your "Lovely Red Headed Tubes," but after I try out my nice looking TFK PF86.:)
I've got a pair of TFK EL84 as well;)

Well, I was planning to build a separate amp using 6V6 with your EF37A during my sizzling summer holidays, so I guess I should save those lovely 'REDS' for it :D

I know that its a very common value, but somehow I couldn't find any in exotic brands :xeye:
But now, I've found some Mil quality AB carbon comp. ones in 220ohms @ 2W:) 110ohms is even harder to find.

I don't really get which ones you are talking about:dead:
Could you please tell me which ones they are, by showing the original value shown in the diagram? There are many grids on each tube, as they are pentodes:rolleyes:
And I think I need to learn about the function of each grid soon.
Would I really be able to use 100K instead of 470K? It allows me to have more options to choose a brand.

Thanks guys!:cool:

JayJay

http://www.diyaudio.com/forums/showt...753#post431753

That should solve your cap problem...if they are expensive enough for your purposes :D

For the power resistors your looking for, you can buy as little as 1 resistor directly from Caddock, they got some thick film power resistors that might fit your liking.

Magura:)

First you need to email Michael Percy Audio. Second go here and download the catalog:

http://www.percyaudio.com/Catalog.pdf

Thirdly you need to take that big hook out of your lip.;) ;)

Man, I'm not a rich guy :dead:

How could I contact them?

www.caddock.com :D

Magura:)

For those who don't understand what I'm talking about; I had a very nice deal from ShiFtY for 3pcs of EF37A and many others as well..:)
Thanks Henry, I'll deposit the payment soon.;)

Should I just give'em a mail to contact?