12 volt tube mixer

[Tubetec]

I have five 20 ah 12v sealed lead acid batteries , mostly I just keep them in parallel on float charge , I never really thought about using them as a ht supply , 
Maybe four or more smaller 12 volts in series for ht and a single larger capacity 12 volts for the heaters , very much back to the foundations of the valve itself , no need for switching supplies at all , and it should be nice and quiet too .  Maybe the physics of two seperate batteries makes good sense like Pvision said , capacity of the HTbattery  need not be huge ,  multicell lipo  like used in Rc modeling might be another possibility  6 cell packs are common ,with around 24 volts fully charged  5000mah or more  is available off the shelf .There good for hundreds of amps of current , so a ht supply would be a very small load on them .

 

[gyraf]

It would be nice to find a reputable manufacturer of a 12V to 250V dc/dc convertor.

Absolutely - I've been looking for some time now.

As for the build-from-scratch approach, someone once did a functioning 500-series version of the G9 - that must have contained such circuitry...?

 

[ruffrecords]

Absolutely - I've been looking for some time now.

As for the build-from-scratch approach, someone once did a functioning 500-series version of the G9 - that must have contained such circuitry...?

I am sure I have seen at least one 500 series mic pre with a tube in it so I agree someone has been down this road before. I guess there are different approaches depending on the current draw. For a single tube drawing 10mA  (2.5 watts output) the approach might be different to  where you need 100mA for a small mixer (25W output). Maybe a good place to start would be a 10W device that would owrk for lots of projects using a small munber of tubes?

Cheers

Ian

 

[merlin]

Once you go the dc/dc route there are quite a few  ready built options out there compared to the ac mains in HT out scenario.
I am always a little wary of super cheap Chinese gear

I've used one of these before. Of course, it has Chinese ratings, but I was able to get about 25W out of it at 300V, comfortably.

https://www.ebay.co.uk/itm/DC-12V-24V-to-DC-200-450V-220V-380V-High-Voltage-Boost-Converter-Power-Supply/332742877713?hash=item4d79056211:g:0okAAOSwFqpbYfR1:rk:1f:0

 

[ruffrecords]

I've used one of these before. Of course, it has Chinese ratings, but I was able to get about 25W out of it at 300V, comfortably.

I have something similar on order to try out. I notice the one you posted uses an 8 pin DIP chip. Which chip is that?

Cheers

Ian

 

[merlin]

Which chip is that?

I don't know, the labelling is in Chinese characters! 

 

[Jarno]

There are a few circuits for SMPS HT supplies, but they are nowhere near 25W. A bipolar 555, a transistor, a cap and a coil basically.
I did a layout, but I need to source a beefier coil, right now the output collapses on even a few mA.

 

[Conviction]

I have an old tube mixer with a built-in HT power supply. It uses two germanium transistors, a couple of rectifiers, a cap and some kind of coil/inductor of unknown value. Supply is 6VDC (battery) for 300VDC output. The technique is probably obsolete,  but it's interesting. The downside is I can actually here it squaling, might have been different when it wasn't 60 years old.

This little device supplies HT to 14 EF86's and one E80CC.

I think I have the schematic.

 

[scott2000]

What's up with those vibrator transformers? I've seen some pretty big ones.....

 

[shabtek]

The gemini G9 51x uses a


MAX1771

 

[ruffrecords]

The gemini G9 51x uses a


MAX1771

Nice looking chip. Available in DIP too. Thanks for the tip.

Cheers

Ian

 

[PRR]

.

 

[ruffrecords]

All solid state 300V dc-dc convertor in 1959! Incredible.

Cheers

Ian

 

[JohnRoberts]

All solid state 300V dc-dc convertor in 1959! Incredible.

Cheers

Ian

I wonder if they count vibrator/relay choppers as solid state?
-------
My first technician  gig was on a DC to DC switching PS for a Navy project in the late 60s. No where near 300 V but pretty early days for switching supplies. Had to trick an early linear voltage regulator IC (LM100) to work as a switcher.

The early bipolar switching transistors would release their smoke if you looked at them funny. Voltage spikes from the magnetics were a problem with 24V rails, can't imagine 300V with 50's device technology. But I guess all that had to work up that high was the final rectifiers.

JR

 

 

[ruffrecords]

The first transistor I bought was a red spot transistor in the early 60s They were for audio frequencies. You could also get white spot transistors which were for RF. I also remember you could scrape the paint of the early Mullard OC71 transistors and get yourself a cheap opto transistor because the inside plastic case was transparent. They later got wise to this and filled them with opaque gunk.

Cheers

Ian

 

[Conviction]

All solid state 300V dc-dc convertor in 1959! Incredible.

Cheers

Ian

Like I said, I have an old tube mixer from 1958 with a 300 volts dc-dc converter. Input is 6VDC. Two germanium transistors, a rectifier bridge, some caps and a coil (inductor?) etc. Looks very neat. The (rather small, considering) box is located behind the mains power transformer.

This mixer model was used by Swedish Radio for field/remote recordings. Designed by a in house engineer named Fröberg.

Ps. I suspect the battery was heavy.

Could post some pics if someone's interested!

 

[ruffrecords]

Like I said, I have an old tube mixer from 1958 with a 300 volts dc-dc converter. Input is 6VDC. Two germanium transistors, a rectifier bridge, some caps and a coil (inductor?) etc. Looks very neat. The (rather small, considering) box is located behind the mains power transformer.

This mixer model was used by Swedish Radio for field/remote recordings. Designed by a in house engineer named Fröberg.

Ps. I suspect the battery was heavy.

Could post some pics if someone's interested!

I would definitely be interested.

Cheers

Ian

 

[PRR]

Much to amuse in this number, including a comparison of early car-radio dynamotors.
https://www.americanradiohistory.com/Archive-Electronics/30s/Electronics-1932-03.pdf

By 1949 the market was flooded with surplus production capacity and military surplus, plus the rise of vibrators. But I recall into the 1970s, dynamotors still being traded-around by ham radio operators, because they came in higher power and were much more robust against accident and wear than vibrators or the early transistor buzz-up boxes.

In 1949 you could hand-crank 500V 100mA-- field radio from a war where fuel could be scarce and sound could attract bullets but manpower was readily available.

"Send today. Don't delay!"

 

[Tubetec]

These look good , 280vdc @700ma ,not really sure if their suitable as ht supplies or not ,

https://www.ebay.ie/itm/5-Pieces-HLG-185H-C700A-Mean-Well-LED-Power-Supplies/392190856492

 

[ruffrecords]

These look good , 280vdc @700ma ,not really sure if their suitable as ht supplies or not ,

https://www.ebay.ie/itm/5-Pieces-HLG-185H-C700A-Mean-Well-LED-Power-Supplies/392190856492

Unfortunately, according to RS, they are a discontinued product which is a great pity. I have one of the higher power version which I have yet to test. I have also sent a direct enquiry to Meanwell about a 250V 400mA custom supply.

Cheers

Ian