I´m most nervous about the frequency response.
The primary inductance should be quite high due to the parafeed circuit (no DC through the transformer) but I dont know anything about the interwinding capacitances, resonace freqs etc.
I haven´t deicided what plate load to use yet. I´m thinking either DIY plate chokes (alot of work) , CCS (Sand in my amp...
or SRPP.
The primary inductance should be quite high due to the parafeed circuit (no DC through the transformer) but I dont know anything about the interwinding capacitances, resonace freqs etc.
I haven´t deicided what plate load to use yet. I´m thinking either DIY plate chokes (alot of work) , CCS (Sand in my amp...
or SRPP.
TOROIDS
Hi,
In case you would choose an SRPP topology,an OPT such as the Hammond 119 DA should do fine.
Poweroutput would be 3.6W before clipping.
If you base your toroid around similar specs it would perform more then adequately.
Are you planning to use an existing power xformer (toroid) and use that as an OPT?
Ciao,
Hi,
In case you would choose an SRPP topology,an OPT such as the Hammond 119 DA should do fine.
Poweroutput would be 3.6W before clipping.
If you base your toroid around similar specs it would perform more then adequately.
Are you planning to use an existing power xformer (toroid) and use that as an OPT?
Ciao,
I'm not familiar with the term "parafeed." From context, it sounds like it might be synonymous with Circlotron...?
In any case, the thing to watch for in 6080/6AS7 based circuits is drift of idle current. What won't bother an EI stack can cause some grief with toroids. Idle current stabilization schemes (e.g., servos) and/or low value grid leak resistors can help a great deal.
In any case, the thing to watch for in 6080/6AS7 based circuits is drift of idle current. What won't bother an EI stack can cause some grief with toroids. Idle current stabilization schemes (e.g., servos) and/or low value grid leak resistors can help a great deal.
PARAFEED
Hi Sy,
If you like you can read about "parafeed" here:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=5920&highlight=PARAFEED
Since one does not have DC on the OPT it should be a problem.
Ciao,
Hi Sy,
If you like you can read about "parafeed" here:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=5920&highlight=PARAFEED
Since one does not have DC on the OPT it should be a problem.
Ciao,
Hi guys!
Thanx for the quick replys!
That Hammond 119DA seems like a really nice little transfomer, maybe I should try to get a pair of those instead of paying the same money for power toroids.
Now I feel encouraged to start up this project ASAP, right now I´m going for a little cartrip to pick up four 12B4A for another project.
...Or maybe they would work great as driverstage for the 6AS7s?
Thanx for the quick replys!
That Hammond 119DA seems like a really nice little transfomer, maybe I should try to get a pair of those instead of paying the same money for power toroids.
Now I feel encouraged to start up this project ASAP, right now I´m going for a little cartrip to pick up four 12B4A for another project.
...Or maybe they would work great as driverstage for the 6AS7s?
12B4A is a tasty tube. Try it at about 110 Va-k loaded with a choke or CCS, Vg - 11V, Ia= 30mA, Rk = 360R (approx from memory). Will swing +- 70V approx very cleanly and make a nice 1W amp on it's own, so it makes a grunty driver too. CCS loaded gain is about 6.5, Zout is 930R with a bypassed cathode, about 3600R without.Fuling said:
For a linestage where the swing will only be a volt or two max, use the same conditions as above with a 300V B+, Rl=6000R (10W rated). Gain is 5.6 (Rk bypassed), 4 (Rk unbypassed) and Zout is 800R and 2260R respectively. If you already have the supply rails up at this level this is an easier implementation. I'll try it soon, so no comment on the sonics yet, but it should be good.
Good evening, gentlemen!
Now I´m back from my little trip with four GE 12B4A in my pocket.
Happier than a pig in sh*t
Well, back to the topic:
What about finding toroids with two identical but separate primary windings and use them in a split load topology??
One winding on the plate and the other (phase inverted) on the cathode.
Since we´re talking triodes here the plate and cathode current are exactly equal which means perfect DC balance in the transformer which means high primary inductance which means good bass response (puh!)
Unfortunately toroids with two separate primays are a bit hard to find where I live, but it should be possible.
The reason behind all this talk about oddball transformers and amp topologies is that I just a week ago finished a very serious and expensive 6B4G SE amp that I´ve been collecting parts for for like six months. Now I just want to have som good old fun
and maybe learn something
Now I´m back from my little trip with four GE 12B4A in my pocket.
Happier than a pig in sh*t
Well, back to the topic:
What about finding toroids with two identical but separate primary windings and use them in a split load topology??
One winding on the plate and the other (phase inverted) on the cathode.
Since we´re talking triodes here the plate and cathode current are exactly equal which means perfect DC balance in the transformer which means high primary inductance which means good bass response (puh!)
Unfortunately toroids with two separate primays are a bit hard to find where I live, but it should be possible.
The reason behind all this talk about oddball transformers and amp topologies is that I just a week ago finished a very serious and expensive 6B4G SE amp that I´ve been collecting parts for for like six months. Now I just want to have som good old fun
and maybe learn something
Fuling,
One of the regulars over at audio asylum who uses the moniker fatbottle has a 6C33 SRPP amp which uses mains torroids as outputs. From memory it is a standard torroid from the Farnell catalogue with a 50W core.
I've linked a recent brief post, but if you use the search engine there you'll find more posts by him and others about mains torroids as outputs.
http://www.audioasylum.com/forums/tubediy/messages/21436.html
A regular here Robert (moniker:moronix) has an SRPP 6080/6AS7 poweramp, and he heas sent me the schem. I think it should be cool to pass it on. If you'd like to see it send me a PM with your email addy.
Cheers
One of the regulars over at audio asylum who uses the moniker fatbottle has a 6C33 SRPP amp which uses mains torroids as outputs. From memory it is a standard torroid from the Farnell catalogue with a 50W core.
I've linked a recent brief post, but if you use the search engine there you'll find more posts by him and others about mains torroids as outputs.
http://www.audioasylum.com/forums/tubediy/messages/21436.html
A regular here Robert (moniker:moronix) has an SRPP 6080/6AS7 poweramp, and he heas sent me the schem. I think it should be cool to pass it on. If you'd like to see it send me a PM with your email addy.
Cheers
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