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Bijou All Tube Futterman Headphone Amplifier - Page 3

post #31 of 4123
I have to say I am very happy with the performance of this amp. I built it P2P a few months ago and have been using it as my main amp. The transformer DOES get pretty warm and sometimes makes a high pitch whine (not in the headphone output, but physically) if it's been left on for a few hours. (I THINK it's the transformer).

Anyways, anyone building this amp should be very happy with the sound.
post #32 of 4123
Quote:
But if someone was going all out the 370 would be worth considering in my book.
You get no argument from me there.
post #33 of 4123
Thread Starter 
Quote:
Originally Posted by rb67 View Post
I have to say I am very happy with the performance of this amp. I built it P2P a few months ago and have been using it as my main amp. The transformer DOES get pretty warm and sometimes makes a high pitch whine....
which transformer did you use? I know that runeight's amp runs hot but this is because the transformer was "underrated" for the necessary current requirements. The 270 DAX was chosen for it's higher rating. Mine gets warm, not unlike any of my other tube amps..dB

The 370 looks like a decent alternative.
post #34 of 4123
These are good points on the transformer.

My original 270AX overloaded transformer (because I had it in the parts box) runs very hot, although it doesn't make any noise.

The 270DAX will be running 2.8-3A for the heaters. That's close to the 3.5A rating and the heater winding will warm up for sure. But it should be far from overtaxed.

The HV winding in the full wave mode will be supplying from 55-65mA depending on chioce of ECC99 or 6N6Pi. The rating on the HV secondary is 90mA so this winding is only operating at 2/3 capacity or less.

My guess is that the transformer will warm up but it should not run hot.

rb67 which transformer are you using?

Edit: Don, your post and mine crossed in the ether.
post #35 of 4123
Quote:
Originally Posted by amphead View Post
I'm in for the three boards. Like I mentioned earlier, I can't log-in to my headwize account. Thanks for having my back Vixr! Runeight has me on his list now, Right? ;-) One question, you probably has this info listed, but are the tubes self-biasing or is there a biasing link? Thanks
I will put you into the list. We got your back (-:
Could you email me your name and email address?
post #36 of 4123
Quote:
Originally Posted by Jrossel View Post
I will put you into the list. We got your back (-:
Could you email me your name and email address?
Thanks Jrossel! Done.
post #37 of 4123
You can always use the R0080-036 model LiTe R-Core transformer.





It's got way too many secondary windings, but that allows you to use 12.6V heaters in addition to 6.3V heaters. Mine never gets hot, and who says there's something wrong with overkill

I bought mine from VT4C (very trustworthy seller btw). The cost in the end was about $50, which is comparable to the Hammond DAX. R-cores are less noisy though and this one's higher rated.
post #38 of 4123
Thread Starter 
Good call mazuki - I had forgotten that you used the r-core. It also makes sense if you are trying to hide the transformer inside a slim chassis but be aware that like the 300 series , there are more secondaries to connect in places they don't belong..dB
post #39 of 4123
I'm new to the world of tubes 'n' such so please forgive me if this is a stupid question.

The 270DAX is 117VAC primary. For 240VAC is the 370DAX the approriate replacement?
post #40 of 4123
Quote:
Originally Posted by fordgtlover View Post
I'm new to the world of tubes 'n' such so please forgive me if this is a stupid question.

The 270DAX is 117VAC primary. For 240VAC is the 370DAX the approriate replacement?
Yes, that's correct.
post #41 of 4123
Quote:
Originally Posted by Mazuki View Post
R-cores are less noisy though and this one's higher rated.
R and C and toroidal core power transformers have high bandwidth, which is bad in a tube PS as it allows HF noise to pass into the circuit. EI's, on the other hand, act as a natural filter to HF noise which is one of the reasons they are used in tube amps which generally don't reject PS noise well. You'll have to ask runeight what the HF PSRR of his regulator is to see if an R core is appropriate ... of you could add a choke instead of R7 or R8 -- I'd tend to do this anyway. Try a Hammond 158L -- high H, lowish DCR (about right for the circuit), decent current, and low cost. This will also allow you to lower the capacitance of C4 and C5 which would allow for a largish film cap, which would likely sound a little better.
post #42 of 4123
Good point on the transformer noise. Leaving aside the tube, which will generate its own noise, the rest of the PS has a PSRR of about -100db at 10Hz and gets montonically better than this with increasing frequency.
post #43 of 4123
As per Fordgtlover's post - i'll have to use the 370DAX series for the universal voltage - wiring it for 115v here and changing it to 240v when back home next year.

So will appreciate when the build comes to learn which appropriate secondary wires to use. I presume that 6.3v CT means that it it 6.3v-0--6.3 and we will use the center wire as the reference ground?

her shann
post #44 of 4123
Thread Starter 
Quote:
Originally Posted by hershann View Post
I presume that 6.3v CT means that it it 6.3v-0--6.3 and we will use the center wire as the reference ground?
her shann
no it means 3.15 - 0 - 3.15 , you would therefore not use the center tap.

..dB
post #45 of 4123
Thanks Dsavitsk! Putting a choke in, for the purpose of using large film caps on the output sounds good. The choke being a plus regardless to reject ps ripple.

Quote:
Originally Posted by dsavitsk View Post
R and C and toroidal core power transformers have high bandwidth, which is bad in a tube PS as it allows HF noise to pass into the circuit. EI's, on the other hand, act as a natural filter to HF noise which is one of the reasons they are used in tube amps which generally don't reject PS noise well. You'll have to ask runeight what the HF PSRR of his regulator is to see if an R core is appropriate ... of you could add a choke instead of R7 or R8 -- I'd tend to do this anyway. Try a Hammond 158L -- high H, lowish DCR (about right for the circuit), decent current, and low cost. This will also allow you to lower the capacitance of C4 and C5 which would allow for a largish film cap, which would likely sound a little better.
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