Junk Bin Tube Amp.

[DummyLoad]

new list of obscure tubes of interest attached.

i think i'm going to fiddle with some loktals next... anyone have any ideas? - jojo, buttery, slucky, bueller....bueller?

7AD7 looks like a nice victim...errr, candidate.  SE would be nice - pentode front end? i remember a locktal twin triode that has a squat shape - can't find it now.  

aha! found it! 7F8

http://tubedata.milbert.com/sheets/127/7/7AD7.pdf

http://tubedata.milbert.com/sheets/137/7/7F8W.pdf

P-P ideas?  

[RicharD]

I dunno but I'm way overdue to build sumthin.  I started doing the perf-boards for the MP4 project since there ain't no way I'll be ordering any PCB's anytime soon.  It'll all easily fit in that old computer chassis you gave me.  This also got my protoboard completely cleaned.  I even windexed it.  I'm thinking about a stereo 6GK6 project since some loaded dummy gave me a complete set of transformers.  It might end up my car stereo amp ifin I ever tackle the inverter power supply project.

 

[jojokeo]

Great list! Thanks.

First thing that came to mind: pentode/7C7 > cathode follower/7F8W > Tone Stack > power tube/7AD7

Here's a 7C7 for $3.90 plus $3.90 shipping;
http://cgi.ebay.com/7C7-TUNG-SOL-DETECTOR-AMP-LOKTAL-EMISSIONS-90-Gm-109-/110659971555?pt=Vintage_Electronics_R2&hash=item19c3d929e3

[DummyLoad]

OIC, the loktal rokker.... me likes!

jojo, please clarify... do you mean:  <7C7 amp> <lvl ctrl><7F8 CF><tone ctrl><7F8 amp><7AD7 SE>


some loaded dummy...

[DummyLoad]

...no way I'll be ordering any PCB's anytime soon

i can help, uncle sam was generous this year... do we have the artwork finished?

[RicharD]

>some loaded dummy gave me a complete set of transformers

PT secondaries:  580VAC, 5VAC, 6.3VAC, 15VAC, 16VAC
Dang old organs and their tube rectifiers!  580V HT with sillycon puts me at 375VDC.  A bit much for 6GK6's.   

>do we have the artwork finished?

It's right where I left it when you saw it last.  We need to rework hole sizes, dew the ground planes, and verify dimensions of the pots, XLR jacks, etc.  I think it'd be better to run a prototype on perf and make sure the thang even works with all the frills added in.  We know the amp circuit is golden but I'm concerned about all the thingamagigs causing noise-n-pops.  If you wanna throw money at it, we need meters, relays, regulators, pots, and other misc.  That's still some coin.  I'd hate to do a board run and have problems.  Let's keep the horse in front of the cart. 

[DummyLoad]

....at 375VDC.  A bit much for 6GK6's. 

meh! they can take it... bias accordingly. 

[jojokeo]

Okay, two simple versions to check out...I haven't had time to verify bias values but I like the name 

[DummyLoad]

jojo, looks like the 7C7 uses the same RC charts of the 6J7 & 6W7G  that are very similar to 6267/EF86. matchless/VOX front end?

 

 

[DummyLoad]

A bit much for 6GK6's

i have 4 of these....

http://scottbecker.net/tube/sheets/131/6/6889.pdf

they are the 6L6 from hell. 3KV anode and 850V ratings, with Pa dissipation of 30 rated Watts - i bet they do 35-40 without breaking a sweat. they'll take 50g's continuous and guaranteed 500g impact resistance - sounds like your tube. used pairs can be had for about 70 bux on fleebayz... + we have other sources.

just a thought...

[jojokeo]

jojo, looks like the 7C7 uses the same RC charts of the 6J7 & 6W7G  that are very similar to 6267/EF86. matchless/VOX front end?

That's what I was thinking with using that particular one. Also why I think initially going w/ only the 100K/470K combo may help w/ poss micrphonics better?