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New to AK ,bought an old tube amp ,need help

K

klipschoid

Active Member
Need help determining what this amp is,whether mono or stereo,i think its a packard bell.Two output transformers under chassis ,has 4 tubes,i see a 7 pin socket in photos.I havent received the amp yet its codes are rpt-1,dpa-5 ,serial num 10817 and says pb#70759 ,thanks for any replies,ill try to post photos Screenshot_2017-01-29-21-06-23.png Screenshot_2017-01-29-21-06-36.png
 
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Check the 2 input rca jacks, if they go to 2 different tubes that would indicate stereo. Except in a single ended amp where 1/2 of each side of a dual triode like a 12ax7, would power 1 power tube like a 6bq5. Also check the output from the output transformer. if each goes to 2 seperate speaker jacks, that would indicate stereo.. On console amps the speaker hook ups might be a different kind than you are used to seeing. In fact they might be the half moon shaped brown phenolic things that are to the right of the "input" rca.
 
Kind of hard to tell from those photos what's going on. When you receive it, snap some more detailed photos.

At first blush, I'm going to guess a stereo single-ended 6AQ5 amp (you did say "7-pin"), driven by a 12AX7. The 4th tube is the rectifier (probably a 6X4 / EZ81). This was a pretty common topology for low-power console amps. The 6AQ5 is basically equivalent to a 6V6, but has a max plate voltage of 250V. You can expect probably 2.5W/ch out of it if that's the case.
 
Ah thanks yall,I am aware of effeciency and i have a pair of klipsch cornwalls 1980,yes the amp has the phenolic half moons on side,and correct the socket that is missing a tube is 7 pin,i want to study more and maybe replace the caps resistors and such and put in a wood frame ,ill take close up pics when i get the amp here
 
Thanks,i wonder how a 6aq5 sounds,i had a nobsound set el34 /6n9p/5z3p ,but i wanted an old american rusty real tube amp and see what my cornwalls think :)
 
Cademan,howd you know its a packard?,Im curious whats used as a preamp tube ,i guess the outputs are 6aq5,ill know more when i get it ,seller didnt say if it worked or not ,guess ill use a dim bulb test on it first ,thanks for yalls replies,i welcome more info ,anytime
 
I've owned several including the DPA stereo amps which use the 6BQ5/EL84 tubes in push pull.

Watch out for that single RCA jack just under the 120 volt ACC outlet. That one is for a dial light / panel lamp. Might think about switching it out with something more conventional so you don't accidentally plug something else into it.

The single front end tube is most likely a 12AX7. The two outer 7 pin tube sockets would be the 6AQ5's. That's probably a 6X4 rectifier tube if its 7 pin. If it is a 9 pin tube, it is a 6CA4.
 
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The rec is 9pin i looked at the photo i got taken of the under side spaghetti,i counted 9 tabs on the rec,thanks for your knowledge,it helps,now i know what goes in this "foot warmer"
 
If anyone can answer this id like to upgrade opts on this unit i would prob need two 5 watt but whats the impedence that is needed on the 6aq5 side of the xformer ? I havent yet looked at parameters for a 6aq5 ,thanks anyone ,i know theres a turns ratio,but i know these packard dpa,mine is dpa5 could prob use bigger opts ,yall have a good night
 
I have a pack Bell dpa-30 there's alot of info about them, PP 6bq5.

Yours looks like a stereo single ended amp.

The pack Bell DPA series all seem to be very respectable, very similar to the Maggie's everyone loves, just a little more rare.

I think those output transformers are going to be great on that amp, I wouldn't worry about upgrading them.

If I had that amp, I would probably recap it, gut any superfluous parts and maybe try to find a way to mount the transformers on top :) maybe give it all a paint job.

Those moon shaped things are the speaker Jack's. You can add proper speaker Jack's instead.

Chances are there's an octal socket or some sort of umbilical cord connector that would power to the rest of the components that you don't have, it may or may not need a switch or a jumper wire connected to turn it on.

I can't imagine an easier first tube amp project... It probably works as-is.

That's a perfect little amp!
 
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Thanks,its missing a tube,so ill go cheap on replacements to start off testing,i know its late,maybe reply tomorrow,im wondering why these 7 pin tubes arent capped at the bottom,you know,like the 8 pinners,like say an el34 ,,theyre naked glass with pins comin out,no plastic,or can those be bought.Yea ill prob wana recap,and reresist,lol,and put a good ole style barrier strip for speak outs ,and paint it ,thanks for reply and your input,talk later
 
Sams folder 480-9 covers it. I doubt you can fit better transformers on that chassis - looks pretty tight. 6BW4 can sub for the 6CA4 for considerably less - you need to add a jumper on the socket, then either can be used.
 
Ok,thanks,ill ask more in depth about that jumper when amp arrives,hope i gets here in one piece,seller didnt know anything about the amp,but not all sellers do
 
7 and 9 pin miniature tubes always have the pins coming right out of the glass. That's the way they were designed and they never have bases. It was an advancement in design that presumably cut production time and cost by eliminating the need to attach a base and solder the wires into the pins. They just made the wires coming out of the glass a little thicker and let them act as the pins.
 
Tried to get a scott tube amp a 200 stereomaster,but hell the prices are ridiculous,middle class people need a place in the market too,cant pay mcintosh prices for an old unknown condition scott amp lol
 
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