PT for small amps like TIMBO'S 10W SLO Clone - One Question

[kagliostro]

I've read the 10W SLO Clone thread posted by TIMBO

http://el34world.com/Forum/index.php?topic=24604.0

He decided to maintain the Haig B+ Voltage of the original amp for the preamp section and lower the Voltage for the power tubes using a VVR

I've a pair of transformers that are not difficult to find in my area they are 190VAC @ 120mA & 6.3VAC for heaters

the 190VAC rectified with a SS bridge will become around 265VDC (that I think are usable for those tubes that accept a B+ of max 250VDC like 6aq5 and others), but low for the SLO preamp

so my question is

is feasible to split the PS and add a voltage doubler only for the preamp section ?

190AC x 2.6 will become around 490VDC, clearly too high, but all the preamp is 5 tubes and I think a consumption of around 15mA, this litte consomption allow the use of resistors to tame the voltage, something like in the original SLO also if Power Tubes are not present ?

Thanks

Franco

[st]

Have a look at the Alembic f2b. It's a bass preamp that is really an exact copy of a Fender preamp (without any effects) and uses a voltage doubler for b+.

[kagliostro]

Ciao ST

I belive you, but I've a few F2b schematics and no one has a doubler

Franco

[TIMBO]

Hi K, Would it be easier to use two transformers.

[DummyLoad]

Ciao ST

I belive you, but I've a few F2b schematics and no one has a doubler

Franco

K, see attached. T2 is a 120V/240V isolation or world power step/down 20-25VA - 50VA is probably more common though.


--pete

[st]

Ciao ST

I belive you, but I've a few F2b schematics and no one has a doubler

Franco

This is the schematic on the official website, and it definitely has a voltage doubler:
http://www.alembic.com/support/F2B_manual.pdf

I don't think it was ever revised to not have a VD. (Many clones, though, might not have one...)

[kagliostro]

Many Many Thanks

I don't have that schematic

glad you shared it 

Franco

[kagliostro]

Excuse me, I apologize, I forgot to thanks TIMBO and DummyLoad for theyr answers


Franco

[TIMBO]

 

[kagliostro]

Hi Friends nice Easter to all

I stopped this thread because of .... some kidney stones that torment me (I hope you never find out what I'm talking about)

---

To me this seems the simplest solution (having a transformer like those I've)



if you see, on the original SLOClone B+ is 488V (near the same voltage I obtain with the doubler) and is tamed with resistors & capacitors (OK, there is also a choke) till the 384V of the first node of the preamp



Don't you think this is more easy than using 2 transformers ?? (consider that the consumption of the preamp is low, I think around 15mA)

Thanks

Franco

[shooter]

Happy Easter to you also my friend.
there is a saying in Christianity, "This too shall pass....", 
I have passed a few, the fewer the better!!

[kagliostro]

Ciao Shooter


Franco

[sluckey]

I wonder how these two components will interact with each other, since they are in parallel. Have you actually built this circuit?

[st]

I too believe it will not work. There is, however, a classic circuit that combines a "single" rectifier with a doubler, so that one transformer winding produces two voltages. Works with both ct and non-ct Transformers.

See e.g. here:
http://www.bunkerofdoom.com/lit/4x8/

[DummyLoad]

I wonder how these two components will interact with each other, since they are in parallel. Have you actually built this circuit?

both outputs will be 500V+.


--pete

[kagliostro]

Ciao Steve, Pete and all the other kindly friend

No, not yet build

(in this days is good if I'm able also to only read and post on the forum, because of those stones I was talking about ...)

Merlin show a second bridge connected to the AC with capacitors to obtain a doubled voltage but the AC must have a grounded CT, so I don't know if my design can work correctly





Franco


P.s.: My mind is very far from be functioning at 100%, excuse me

[DummyLoad]

Hi Friends nice Easter to all

I stopped this thread because of .... some kidney stones that torment me (I hope you never find out what I'm talking about)

---

so sorry to read this. please get well soon. 


--pete

[kagliostro]

Thanks Pete

looking to the circuit linked by St (many thanks St)



and redrawing it in a way that is more easy to read for me, if I'm correct this is the result



is this correct ?

 


or may be this is the correct version ???




Thanks

Franco

[TIMBO]

Hi K, Hope your stones pass without any problems.
I have had them, not fun.

[kagliostro]

Ciao TIMBO

I hope you never have to do again with them (and we know what we are  talking about)

Franco

[shooter]

in the '90s I was working with an Israeli engineer, he was proto-typing a machine that sat on the MRI table, you'd lay on it and it would emit HF sonic pulses that were supposed to bust up bigger stones.  The tech would then run you in the MRI and "see" how well they busted up.
He was a pretty dry engineer, so I was mostly bored 

[DummyLoad]

attached is how it should be wired. d3 + d7 form 1/2 of a doubler & d2 + d5 form 1/2 of a second doubler - d6 + d8 bring them together as a full wave doubler.


--pete

[kagliostro]

Thanks my friends

later if I feel better I'll try to read your answers

Tomorrow I'll go to a specialist, is one week and more I'm waiting for that

Franco

[kagliostro]

Ciao Shooter

tomorrow I'll know something more about, may be they can crumble my kidney stones with ultrasounds or perhaps even with just a few pills

Thanks Dummyload

today I was able to understand your schematic 

Thanks Friends

Franco