Choke input power supply question...

[bernieclub]

Reading posts in other forums, it seems like the general consensus is that a choke input filter sounds way better than a cap input, even with the fanciest of fast and noiseless diodes.    Has anyone rebuilt their B.H. gear with choke input PS and had substantial positive results?   Has the BH crew considered using this design?
TIA
Bernie

[Paul Birkeland]

Choke input is great, but chokes designed for this duty are very, very expensive for amplifiers, and I don't believe super practical with voltage doublers. With the hybrid shunt regulator, the Foreplay III and Eros should be pretty immune to giant changes.

It might be possible to build Paramounts for #45's with choke input filters. You'd probably want some big MQ plate chokes for the job if possible.

[Dyna Saur]

With a given power trannie and rectifier(s), the choke input (LC) filter will deliver a significantly lower B+ voltage than a CLC filter.  Might be good for converting a 2A3 SE design to 45, where lower B+ voltaqge is required.

A small value (film)  input cap can be used to fine tune (increase) the output voltage in small steps to meet your requirements.

/ed B in NC

[Doc B.]

Might be good for converting a 2A3 SE design to 45, where lower B+ voltaqge is required.

Maybe you mean going from 300B to 2A3? The 2A3 and 45 already run at about the same B+. For example, the Stereomour.

[Dyna Saur]

No, I was thinking of the Paramour II, where, in the PSU,  the 270 ohms, 5W  Rfilter is changed to 1,500 ohms, 5W for the 45 (and the 1,100 ohm Rk is changed to 1,500 ohms), as described on the schematic and in the instructions.    

I would presume that this would be  be a better approach than changing the filter to a choke input filter design, though some may want to experiment with this? This may be applicable to the 45 version of the PII, with the iron and cap upgrade?   OTOH, the C7X may buzz like crazy in a choke-input PSU, if it's not designed for this kind of service....

I am not yet familiar with the inner details of the Stereomour, except as described in the order page. Maybe someday soon  I will have some actual hands-on experience with the Stereomour (just trying to justify the finances, stay tuned...)  It definitely looks "tempty" ;-)

/ed B

[Paul Joppa]

For comparison purposes, the Paramour II uses a fullwave bridge rectifier with about 300vAC input, and produces 380vDC at the power supply output. A choke-input supply would give you closer to 250vDC.

The most common operating point for a 45 needs about 340vDC. The most common 2A3 operating point needs only 300vDC but Paramour runs at higher voltage, lower current, largely for historical reasons.

Mostly I now use voltage doublers which work very poorly using choke-input filters, specifically they will not double, or even increase, the voltage relative to a normal fullwave bridge.

[bernieclub]

Thanks everyone for responses...it seems that
1  The stock transformer is not suitable for choke input with the standard configuration
2  Replacing the PT with a suitable substitute is probably not worth the difference for the cost without implementing shunt regs. and other circuit improvements.  duh

[Grainger49]

Reading posts in other forums, it seems like the general consensus is that a choke input filter sounds way better than a cap input, even with the fanciest of fast and noiseless diodes.    Has anyone rebuilt their B.H. gear with choke input PS and had substantial positive results?   Has the BH crew considered using this design?
TIA
Bernie

Bernie,

I am quoting your OP.  I don't see that you have specified what Bottlehead product you would like to put a choke input filter on.  I suppose that that means that the first element on the power supply filter would be an inductor.  But many folks have put chokes into FP and Seduction power supplies.

Are you concerned with a power amp/integrated amp only?

[bernieclub]

I always think I'm being clear until someone points out I'm not!    ParamourIs are the subject....I'm itching to rebuild them, but just at the contemplation stage right now...Crack arriving in a few weeks, I hope.    There's a "crazy" tubeDIY forum where a choke input PS for power amps is the holy grail.   I'm looking for well grounded opinions!
Thanks Grainger

[Paul Birkeland]

Rebuild your Paramours into SR-45 amps, that is a much better grounded holy grail.

Otherwise, you might be able to get PGP-8.1's from Magnequest and get enough voltage out of them for a choke input power supply feeding 2A3's.

[Paul Joppa]

I estimate that a PGP8.1 would provide about 300 volts with a choke-input filter using solid-state diodes. That' not enough for the stock Paramour circuit, but would be ideal for a 2A3 with a 2500 ohm load impedance, and should work quite well with 3000 ohms. The greater current (60mA) would require a larger plate choke.

Notice that you have now replaced all the iron on the original Paramour - there's not much left except the tube sockets!

[bernieclub]

Paul

Thanks for putting things into perspective.       I do have BCP15 plate chokes and BH-5 nickel stripe OPTs, which I don't know the impedance of, but I think I'll enjoy them as is.      I think maybe I should save up for Paramounts and be done with it!

Bernie

[Dyna Saur]

PJ inscribed:

Mostly I now use voltage doublers which work very poorly using choke-input filters, specifically they will not double, or even increase, the voltage relative to a normal fullwave bridge.

I must have not had my wheaties for breakfast  that day...  A fullwave voltage doubler, just by definition, would have to be a capacitor-input filter.   Otherwise it wouldn't really be a voltage doubler   I was stuck in the center-tapped HV secondary / 5AR4 rut that day ;-)    

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fwww.bonavolta.ch%2Fhobby%2Fimages%2Faudio%2Fsupply03.gif&hash=1cd30063f14fbe47c1ee3491838921f3c50e83c3)

As my bud Homer S.  sez, D'Oh!!!!   0_o

/ed B (in the  state of confustication)

[Grainger49]

PJ inscribed:

Mostly I now use voltage doublers which work very poorly using choke-input filters, specifically they will not double, or even increase, the voltage relative to a normal fullwave bridge.

I must have not had my wheaties for breakfast  that day...  A fullwave voltage doubler, just by definition, would have to be a capacitor-input filter.   Otherwise it wouldn't really be a voltage doubler   I was stuck in the center-tapped HV secondary / 5AR4 rut that day ;-)    

As my bud Homer S.  sez, D'Oh!!!!   0_o

/ed B (in the  state of confustication)

Dude!  (that is funny because I'm 60)

This is the place where a picture is worth a thousand words.  The voltage doubler takes 2 diodes and a center tapped transformer (I'm wrong about that).  The full wave can be execute two ways, that I know of, four ss diodes and the hybrid (tube and solid state) being the most effective, IMHO.  The center tap of a transformer need not be used for either the full wave or hybrid full wave rectifier.  

As always, any tube rectification wastes more voltage than solid state but passes NO reverse recovery nasties.

Hopefully someone, like CB, who is more computer savvy than me will post a picture depicting all of these.

[Dyna Saur]

I just turned 61 9 days ago....  As they say, the memory is the first thing to go, and I forgot what was the first...   8^0


As far as  full wave voltage doublers, I was thinking of this basic circuit, just replace the tube rect's with SS rectifiers (as done in the SEX amp and others).  It can be fed with a non-centertapped power trannie. With no load, it will deliver approximately 2.8X the AC RMS input voltage, as the current  load increases, the DC voltage output will decrease.

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fwww.bonavolta.ch%2Fhobby%2Fimages%2Faudio%2Fvdbl.gif&hash=5b68c6543774b3f205c37fe5f7b48a06648cf6cd)

Since its output has two caps in series, it would be, by default, the first part of a capacitor input filter...

/ed B