• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Old amp-rebuild or dismantle?

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Yep, you can use any of the 6L6 family of tubes inc the ones I mentioned before, ie; EL37, KT66 (not to mention many others of the same family) and of course the ubiqtous 807.
The beauty of the 807 is it's plentifull and cheap. Only downside and probably the reason it's not more popular is because of the topcap... Plus side is it's a rugged tube and it does sound nice...
tomcat
 
807 amps

If the 807 is a nice sounding tube and somewhat cheap and plentiful as well as being able to be swapped w/ other tubes, this might be a good way to go. I checked out the thread that dave pointed out and wondered, what the differences are between that amp and the one the poster wants to build are(from the FI Primer)? I didnt really follow all the discussion as to design philosophy. I just want a good performer thats easy to construct and needs little tweeting. Im also getting the impression that no matter what amp one builds, the OPT is a critical component and a bigger consideration to budget is in order. I see that freq. response gets more limited as the tranformers get cheaper. Any other good (simple) 807 designs?

Taylor
 
THX P10!

Dave, that was a great idea - bypassing the preamp and checking the sound of the amp only. I built a cheapie passive, the HH passive w/ RS parts and hooked it up to the amp. Bingo! Sweet sound and very detailed . So my next project is to rewire/replace parts. One question though. This amp uses balancing pots and meter(tube) and a center channel connect. I assume removing the center isnt a problem but if I pull out the meter and the two 500k pots, will this effect anything? Do the pots act as trim pots and need to be replaced or can I scrap the whole circuit. Below is one channel and the center and balancing circuit.

Taylor
 
The schematic

It didnt attach the first time.
 

Attachments

  • 5050schematic2b2.jpg
    5050schematic2b2.jpg
    54 KB · Views: 277
frugal-phile™
Joined 2001
Paid Member
Re: THX P10!

taylor said:
One question though. This amp uses balancing pots and meter(tube) and a center channel connect. I assume removing the center isnt a problem but if I pull out the meter and the two 500k pots, will this effect anything?

Looks like it is part of the biasing (not all the schema is there). I'd make sure you understand what it is doing before you muck too much.

dave
 
tubes

Bernhard, thanks for the offer but for I currently have 2 sets of telefunkens for it (hopefully that will be enough for awhile) Once I get the rewiring done and check/listen seriously to the unit, I may want somemore though. Ive decided to leave the "stereo balance" circuit in since Im not positive what removing it will do. When adjusting it while operating (500k pots) there is very little change it the sound. Besides, my buddies think the "blue eye" tube looks cool.

taylor
 
Dave and Taylor,

for data and curves on the EL84 and EL86 please go on my website (www button below), look for the index and below the link for typographic conventions there is s a link called "Download EL84 / EL86 data".
Click on that link and your browser will download an approx. 2MB zip-file with all the data and curves i could find.
I hope the pixes in this zip-file are readable, i had to use a digital camera for them.

Hurry up to download, as soon as i need the webspace, i'll delete them 1st.
 
Thanks for data! Now if I could interpret all of it. BTW, nice site youve got. Ive always loved vertical trackers if only for the great engineering and machining. My first love was a Rabco Studio Standard on a Thorens circa 1972 that was a friends. Never could convince my dad that "we" really needed one. Had to settle for a B&O.

taylor
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.