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Old 3rd Nov 2015, 6:13 pm   #21
Herald1360
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Default Re: Simple battery-powered valve guitar amp

It certainly would be, but finding a suitable TX might be interesting. Some high end radios used them in the '30s.
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Old 3rd Nov 2015, 6:49 pm   #22
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Default Re: Simple battery-powered valve guitar amp

Sorry for not replying to any of the posts but I'm a bit unwell at the moment. I'll be back!
Nick
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Old 3rd Nov 2015, 9:59 pm   #23
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Default Re: Simple battery-powered valve guitar amp

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Originally Posted by pwdrive View Post
Portable battery powered valve practice amp no problem, DF/DL etc, not a lot of power though, high efficiency speaker might improve things a bit.
https://www.youtube.com/watch?v=R9hkg-gZZeY
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Old 4th Nov 2015, 11:47 am   #24
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Default Re: Simple battery-powered valve guitar amp

It makes the right sort of noises but does come across in the video as perhaps rather loud for 200mW or so. Effectively miked up by the production process.

A sort of variation on what I was on about with Julie's ECL80 amp towards the end of post#3.
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Old 4th Nov 2015, 12:19 pm   #25
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Default Re: Simple battery-powered valve guitar amp

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Originally Posted by llama View Post
To save heater power (and a little HT power) for the phase-splitter, would a transformer input to the push-pull pair be feasible?
Graham
Definitely possible.

See "Quiescent push-pull" - http://www.r-type.org/addtext/add019.htm - for how portable radios got both reasonable volume and relatively low HT consumption in the 1920s/1930s. And no I don't know where to get a driver-transformer for a QP230
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Old 4th Nov 2015, 3:47 pm   #26
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Default Re: Simple battery-powered valve guitar amp

It might be possible to reduce the valve count by driving the amp with a Tube Screamer like what the SRV used:

https://www.youtube.com/watch?v=TZHe...OekJ--C7U0RoGd

http://www.dawsons.co.uk/ibanez-ts80...FSgcwwodCGkHSQ

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Old 4th Nov 2015, 4:38 pm   #27
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Default Re: Simple battery-powered valve guitar amp

Quote:
It might be possible to reduce the valve count by driving the amp with a Tube Screamer like what the SRV used
or better still make one I repaired an early 80's TS a few weeks back and they really are rather good.

This thread has encouraged me to attempt to make a little battery valve job, using a 12AT7 in pp using an interstage tx as phase splitter I expect there are lots of reasons why this wont work - but that has never stopped me trying!
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Old 4th Nov 2015, 4:48 pm   #28
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Default Re: Simple battery-powered valve guitar amp

Good man...give it a go.

I made an error in my previous post "with a Tube Screamer like what the SRV used"

Should have written "with a Tube Screamer like what SRV used"

Apologies.

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Old 5th Nov 2015, 6:33 am   #29
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Default Re: Simple battery-powered valve guitar amp

Wouldnt it be mo-bedda to have a battery powered guitarist and a conventional amplifier ?

I have spent days searching my library ( VERY large) and have found umpteen dozen vibrator sets, but not "battery" powered.
I did think the idea was OK, especially after seeing a "Pignose" amp.
BUT!! , along those lines, come some ideas
1. MOST efficient, most HORRIBLE to me, Class D
2. MOST ordinary another Pignose type amp
3. MOST interesting is making up a battery bank ( I havent seen a 90 volt battery since I was a kid) of silver oxide cells.
4. Making a battery bank of Li-Po cells ( huge capacity in very small format ) and not that expensive, DOES require specialist charger however.
5. MOST eccentric is using your billycart as battery carrier, and wearing Ian Andersons raincoat and cap, when you play.
6. MOST exiting is 20 3V4,s in pushpull parallel, driving a Marshall quad box, when the Li-Po battery works

Best regards
Joe
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Old 5th Nov 2015, 8:39 am   #30
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Default Re: Simple battery-powered valve guitar amp

Hi,

Old 1960's PMR equipment such as the PYE Cambridge and Vanguard had valve transmitters. The HT for these were supplied via a transistorised inverter. They could supply something around 100mA at about 270 Volts. For continuous use they would have to de-rated a little but there is still plenty there to power a reasonable output valve amplifier. Getting hold of an old PMR such as a PYE Cambridge would be a cheap and easy way to get hold of a good compact, well designed and reliable source of HT from a 12 Volt battery; although I would use silicon power transistors in the inverter rather than the original Germanium ones (NKT404?).
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Old 6th Nov 2015, 11:33 am   #31
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Default Re: Simple battery-powered valve guitar amp

Any cheap mains inverter (of the modern high frequency design) internally generates a DC bus at around 300 V before chopping it around to produce some crude semblance of a sine wave. This usually has the negative referenced to the battery negative and a simple resistor divider for the feedback allowing you to get any HT voltage you want by changing one component.

Buy a cheap inverter off ebay (de-rating suitably for Chinese Watts) and go from there. Avoid the ones that fit into a cigar lighter plug but something like this would be fine: http://www.ebay.co.uk/itm/12V-DC-to-...YAAOSwhcJWH8ex
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Old 6th Nov 2015, 3:49 pm   #32
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Default Re: Simple battery-powered valve guitar amp

A pair of PM24B would probably work down to 150V I would have thought and being directly heated they are 4V 1A.
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Old 6th Nov 2015, 4:21 pm   #33
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Default Re: Simple battery-powered valve guitar amp

But 4V or 8V is an awkward heater supply voltage for common rechargeable batteries. And decidedly power hungry for the audio output capability.
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Old 7th Nov 2015, 12:08 pm   #34
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Default Re: Simple battery-powered valve guitar amp

Mobility batteries are also available with around a 10 Ah capacity with dimensions not that much larger than what Nick was suggesting in his earlier post....

So for minimum draw with some kind of usable output an ECC83 driving an EL95 might be a solution, ECC83 heaters (heaters wired for 6.3v) in series with the EL95 heater, EL95 heater shunted with a 6v 100 Ma bulb (power on indicator) gives a heater chain current of 300 Ma.

There was a couple of EL95 SE output transformers on Ebay the other day, they probably turn up from time to time (ex German radios ?)

Lawrence.
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Old 10th Nov 2015, 3:06 pm   #35
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Default Re: Simple battery-powered valve guitar amp

My Taylor 'Electronic Fault finder' Model 22 uses an ECC82 as the output valve in Single-ended and makes a fair account of itself into a very undersized speaker. I have no doubt that an ECC82 in P-P would actually do quite well.

Also, on the subject of HT batteries, Li-ion AA's are now available at the usual online outlets, no reason why 24 of them can't be used to get about 90v. You can also get Li-ion 9v batteries although I'm not sure how they achieve the 9v, be it a shunt regulator, couple of diodes to drop from (presumably) 11.1v or some other wizardry.

Dave.
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Old 10th Nov 2015, 7:20 pm   #36
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Default Re: Simple battery-powered valve guitar amp

I have been playing with TinyCAD and drew out the main body of the Taylor 22 for practice, the only parts omitted are 2 parts of the rotary switch which select the speaker as an input device (for testing the O/P stage of your radio under test).

Your RF signal goes in via the Pentode, a normal AF signal is fed in via the terminal at the top, omitting the pentode pre-amp completely but this could be left in for low gain signals. Also not shown is the RF probe which has a GEX34 rectifier diode and some passives.
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Old 12th Nov 2015, 6:54 pm   #37
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Default Re: Simple battery-powered valve guitar amp

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Originally Posted by julie_m View Post
A class-D valve amplifier might just be feasible, using valves meant for hand-held battery transmitters .....
Thank you Julie. I think this is the way to go.
I'm going to make two identical in respect to physical size and speaker wattage. One using purely solid-state components and the other valve driven. My son can then tell me which he prefers.

I already have a circuit and design for the solid state version and I'll report back with a proposed circuit for the valve version once the house move is out of the way.

Thanks to everyone for the posts and suggestions. There is plenty here to get my teeth into.

Nick
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Old 12th Nov 2015, 10:10 pm   #38
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Default Re: Simple battery-powered valve guitar amp

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Originally Posted by SurreyNick View Post
Thank you Julie. I think [a] class-D valve amplifier using valves meant for hand-held battery transmitters is the way to go.
Eep! I wasn't being entirely serious when I suggested that ..... so don't blame me if it doesn't work.
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Quote:
Originally Posted by SurreyNick View Post
'm going to make two identical in respect to physical size and speaker wattage. One using purely solid-state components and the other valve driven. My son can then tell me which he prefers.
Now, that will be an interesting experiment! Especially if he does not know which one is which in the first place .....
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Old 12th Nov 2015, 10:39 pm   #39
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Default Re: Simple battery-powered valve guitar amp

If you're successful, you might well start a new audiophool trend!
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Old 13th Nov 2015, 12:13 am   #40
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Default Re: Simple battery-powered valve guitar amp

Experiment No 1 would be to make a pair of amps which produced the same amount of power, and to see which he preferred.

Experiment No 2 would be to make a pair of amps which took the same amount of power from batteries and so would have the same endurance/weight ratio, and then see which he preferred.

I once made a trio of hifi amplifiers. One was all valve, one was all bipolar and the third was bipolar with a MOSFET output stage. All three were engineered to the same standard; equal power output, similar distortion levels, freedom from slew-rate effects and similar bandwidths. The results of people listening to them were interesting. One of the amplifiers is sitting in the next room playing right now. The other two were stripped for parts. These were not 'performance' equipment, they were designed to have no discernible effect on the material being listened to and that doesn't apply to a guitar amplifier especially for heavy metal.

Anyway this discussion needs a few facts to go on. How many watts does he need and what carrying weight is acceptable?

David
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