Just completed my spitfire clone !!!

chainsawmillerman · Post by **chainsawmillerman** » Thu 04/29/04 6:46 pm

Here's my first attempt at amp building.I'm extremely pleased with the result.The amp was quiet and sounds awsome.The only problem was I wired the pots backwards so I had to fix that and I had originally used stero jacks rather than switch jacks. It is , without any bias (no pun intended) my favorite amp . I just thought you'd like to have a peek.
Anyway I'm hooked , could be down right danderous for guys marriage though : )

kollantai · Post by **kollantai** » Thu 04/29/04 8:17 pm

very cool. I'm confused though. Is that the back or the front?

chainsawmillerman · Post by **chainsawmillerman** » Thu 04/29/04 8:32 pm

It's the front, here's the back

Post by **Plexi** » Thu 04/29/04 9:15 pm

Those look like rounded-black-plate EL84s?? Maybe Sylvania or one of the other brands..

Richie

chainsawmillerman · Post by **chainsawmillerman** » Thu 04/29/04 9:30 pm

Yes they are sylvania black plates,good eye! are they good? How much are they worth? I've not had them tested ,but the amp sounds great! They came with the amp off ebay.This amp started out as a Davis 106 PA head.It had 1 6eu7 also so I had to install another tube socket for the other 12ax7 and rewired the other for 12ax7 from 6eu7.

Post by **Plexi** » Thu 04/29/04 9:43 pm

Yes those are great tubes!! Probably should have said 6BQ5.. I think thats what they go by instead of EL84. Or 6BQ5/EL84

"""out as a Davis 106 PA head"""

now that is funny, Paul Ruby and myself had one of those Davis amps that we cobbled into 18 watters.
Thats the amp he had to figure out the buzz mod for the OT he used from that amp.So something good came from that. I think i got my Davis amp for 20.00 lol They also made a 6AQ5 amp i believe it was a 105A model

A friend of mine builds those Matchless type and Spitfire amps,Philip Morrison,you might see him on Ampage sometimes. He uses the Westlabs trannys..very expensive.

Richie

chainsawmillerman · Post by **chainsawmillerman** » Thu 04/29/04 10:53 pm

Hey thats cool! My amp is nice and quiet now that I put switch jacks in it : ) I never had any buzz? Maybe it's a different OPT. Anyway that chassis is very cramped Thats why I put the transformers on the ends.I like the size of the head it's like "the Mouse that Roared"! I Know the other davis you mean I think it's a 205 I also have 2- 405's and an 808 Davis. I had 1 davis 405 moded by Gar Gillies of Garnet fame into a Revolution type circuit and the other was modded by mark stephanson of stephanson amps to a jcm800 circuit (His amps are very cool ,check out his web site).Finally the 808 I'm currently modding to a Laney Circuit From kevin O'Connors TUT # 3 (the ultimate tone).This project my be more than I should be attempting.This amp came with 4 RCA black plates that I sold on ebay and pretty much financed this project from the proceeds : ) It runs on 4 6v6 and 4 12ax7. It's designed to mix tube type and each tube has it's own seperate bias pot.

chainsawmillerman · Post by **chainsawmillerman** » Thu 04/29/04 10:57 pm

Richie forgot to mention the davis 405 has 2 6l6 the 808 has 4 6l6.

Post by **Plexi** » Thu 04/29/04 11:22 pm

Well the buzz, was on the EL84s when Paul was using the Davis OT
I think there is some info in our files for the fix. Your driver may not be causing the problem the 18 watter does.. It only happens on some amps.
kind of a buzz when the amp is cranked.. It doesn't happen on all the 18s..
I looked at the old Davis chassis, its a 201A used 3 6EU7 and 2 6BQ5 6CA4.. It was the Univox i had that used the 6AQ5.. so i had them mixed up..lol

'''I'm currently modding to a Laney Circuit '''

Laney huh.. this link may help you..watch out for overload..[no pun]
I don't know how long this might be there, so you might want to get what you info you can.

http://www.laney.co.uk/html/Downloads/Services/

Richie

chainsawmillerman · Post by **chainsawmillerman** » Thu 04/29/04 11:56 pm

Thanks Richie,
Let me tell you what I'm planning and have accomplished on this one.I pretty much have the whole thing built.I have a pair of those damn sterio jacks in this amp too.I'm waiting for 2 jacks in the mail right now.So when I turn it on it just sqeals .This amp has a seperate filament transformer and i'm running this transformer off 120 volt supply.The power transformer is running off a variac.It is my understanding that I wil get cranked tone at lower levels, do you agree? I'm having a problem with the bias circuit right now .It seems I have to bring the variac down to 40% to get 20 milliamps off the 6v6's I'm also getting a faint squeel coming from the fillament transformer?I'm using rv6 25 kb pots heres the link to the specs on these pots http://www.precisionsales.com/precomp.html I'm thinking maybe there's not enough range on this pot? Like I said I may be in over my head here but it sure is interesting : ) I really don't have a great grasp on some of the more fundimental asspects of electronics (insert your warning here )but I'm learning. What your opinion? attached are some pics of the latest project.You will notice I made a mistake on the board layout.I kinda inverted it....Damn!!!

chainsawmillerman · Post by **chainsawmillerman** » Fri 04/30/04 12:23 am

I would like to add that I should be able to mix tube types as well.I notice the schematic also has 5 amp fuses on the 6.3 supply so obviously I would have to increase the fuses if I went to a tube with more draw.How would I test the filament transformer to make sure it could stand up to a say, el34 ? If it could'nt would the 6.3 drop below that ? or would the tranformer heat up or what? I'm interested to see what 2 kt66 and 2 6v6 would sound like.Thats a ways off mind you : ) . Can you help?

chainsawmillerman · Post by **chainsawmillerman** » Sat 05/01/04 12:08 am

Today I reversed the output transformer leads and there is no longer any
oscillation . I changed the 3k3 ground resistor in the bias circuit to a 11.2 and I can now bias the amp and maintain proper voltage on the plates.The voltage reading off the plates seem ok. The problem I have now is the amp has very little volume.Any ideas as to why this might be happening anyone?
Thanks,
Chris

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Just completed my spitfire clone !!!

Just completed my spitfire clone !!!