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Sci.Electronics.Basics -> Valve preamp
There are 9 messages in this thread.
You are currently looking at messages 1 to 9.
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Author: Dave.HDate: 10:23 18-06-08
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I have found a valve preamp kit in an online store, to go between an
amplifier based on an LM380 chip, and a crystal or regen radio, but it
uses a microphone where I want an audio input. If anyone can tell me
how to connect an audio in one this or give me a schematic for a low
voltage preamp using a single 12AU7 tube, I'd be grateful
Thanks
Dave
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Author: Dave.HDate: 10:26 18-06-08
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On Jun 19, 12:23 am, "Dave.H" <the19...@googlemail.com> wrote:
> I have found a valve preamp kit in an online store, to go between an
> amplifier based on an LM380 chip, and a crystal or regen radio, but it
> uses a microphone where I want an audio input. If anyone can tell me
> how to connect an audio in one this or give me a schematic for a low
> voltage preamp using a single 12AU7 tube, I'd be grateful
>
> Thanks
> Dave
Oops, forgot the link to the preamp kit,
http://secure.oatleyelectronics.com//product_info.php?products_id=722
They do have (had) another similar preamp with an audio input, but
none are in stock now (discontinued)
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Author: EeyoreDate: 11:31 18-06-08
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Author: EeyoreDate: 11:33 18-06-08
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"Dave.H" wrote:
> "Dave.H" <the19...@googlemail.com> wrote:
> > I have found a valve preamp kit in an online store, to go between an
> > amplifier based on an LM380 chip, and a crystal or regen radio, but it
> > uses a microphone where I want an audio input. If anyone can tell me
> > how to connect an audio in one this or give me a schematic for a low
> > voltage preamp using a single 12AU7 tube, I'd be grateful
>
>
> Oops, forgot the link to the preamp kit,
> http://secure.oatleyelectronics.com//product_info.php?products_id=722
>
> They do have (had) another similar preamp with an audio input, but
> none are in stock now (discontinued)
Fascinating in its own way but utterly irrelevant to what you require.
Stop looking for 'kits' and do some *learning*. Then you can design your own
kits. Less than one day's appropriate study should do it.
Graham
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Author: ian fieldDate: 11:46 18-06-08
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"Dave.H" <the1930s@googlemail.com> wrote in message
news:5a943c3d-af76-42d7-8745-2dfc65a2bc3c@a9g2000prl.googlegroups.com...
> On Jun 19, 12:23 am, "Dave.H" <the19...@googlemail.com> wrote:
>> I have found a valve preamp kit in an online store, to go between an
>> amplifier based on an LM380 chip, and a crystal or regen radio, but it
>> uses a microphone where I want an audio input. If anyone can tell me
>> how to connect an audio in one this or give me a schematic for a low
>> voltage preamp using a single 12AU7 tube, I'd be grateful
>>
>> Thanks
>> Dave
>
> Oops, forgot the link to the preamp kit,
> http://secure.oatleyelectronics.com//product_info.php?products_id=722
>
> They do have (had) another similar preamp with an audio input, but
> none are in stock now (discontinued)
Can you upload the regen schematic to a picture host and post the link?
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Author: Dave.HDate: 19:49 18-06-08
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On Jun 19, 1:46 am, "ian field" <dai....@ntlworld.com> wrote:
> "Dave.H" <the19...@googlemail.com> wrote in message
>
> news:5a943c3d-af76-42d7-8745-2dfc65a2bc3c@a9g2000prl.googlegroups.com...
>
> > On Jun 19, 12:23 am, "Dave.H" <the19...@googlemail.com> wrote:
> >> I have found a valve preamp kit in an online store, to go between an
> >> amplifier based on an LM380 chip, and a crystal or regen radio, but it
> >> uses a microphone where I want an audio input. If anyone can tell me
> >> how to connect an audio in one this or give me a schematic for a low
> >> voltage preamp using a single 12AU7 tube, I'd be grateful
>
> >> Thanks
> >> Dave
>
> > Oops, forgot the link to the preamp kit,
> >http://secure.oatleyelectronics.com//product_info.php?products_id=722
>
> > They do have (had) another similar preamp with an audio input, but
> > none are in stock now (discontinued)
>
> Can you upload the regen schematic to a picture host and post the link?
http://www.oldradios.co.nz/hikers/, it's the 1951 Improved Hiker's one
valve
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Author: ian fieldDate: 10:42 19-06-08
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"Dave.H" <the1930s@googlemail.com> wrote in message
news:404015e4-00e7-40f0-badc-1a5beb73ba39@h1g2000prh.googlegroups.com...
> On Jun 19, 1:46 am, "ian field" <dai....@ntlworld.com> wrote:
>> "Dave.H" <the19...@googlemail.com> wrote in message
>>
>> news:5a943c3d-af76-42d7-8745-2dfc65a2bc3c@a9g2000prl.googlegroups.com...
>>
>> > On Jun 19, 12:23 am, "Dave.H" <the19...@googlemail.com>
wrote:
>> >> I have found a valve preamp kit in an online store, to go between an
>> >> amplifier based on an LM380 chip, and a crystal or regen radio, but it
>> >> uses a microphone where I want an audio input. If anyone can tell me
>> >> how to connect an audio in one this or give me a schematic for a low
>> >> voltage preamp using a single 12AU7 tube, I'd be grateful
>>
>> >> Thanks
>> >> Dave
>>
>> > Oops, forgot the link to the preamp kit,
>> >http://secure.oatleyelectronics.com//product_info.php?products_id=722
>>
>> > They do have (had) another similar preamp with an audio input, but
>> > none are in stock now (discontinued)
>>
>> Can you upload the regen schematic to a picture host and post the link?
>
> http://www.oldradios.co.nz/hikers/, it's the 1951 Improved Hiker's one
> valve
Replace the headphones with a logarithmic pot - the kit instructions should
indicate the resistance value to use, you need to make sure the pre-amp's
input capacitor's working voltage is rated to withstand the full HT on the
regen, or you could add a coupling capacitor to the pot's wiper.
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Author: Dave.HDate: 04:15 20-06-08
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On Jun 20, 12:42 am, "ian field" <dai....@ntlworld.com> wrote:
> "Dave.H" <the19...@googlemail.com> wrote in message
>
> news:404015e4-00e7-40f0-badc-1a5beb73ba39@h1g2000prh.googlegroups.com...
>
>
>
> > On Jun 19, 1:46 am, "ian field" <dai....@ntlworld.com> wrote:
> >> "Dave.H" <the19...@googlemail.com> wrote in message
>
> >>news:5a943c3d-af76-42d7-8745-2dfc65a2bc3c@a9g2000prl.googlegroups.com...
>
> >> > On Jun 19, 12:23 am, "Dave.H"
<the19...@googlemail.com> wrote:
> >> >> I have found a valve preamp kit in an online store, to go between
an
> >> >> amplifier based on an LM380 chip, and a crystal or regen radio,
but it
> >> >> uses a microphone where I want an audio input. If anyone can
tell me
> >> >> how to connect an audio in one this or give me a schematic for a
low
> >> >> voltage preamp using a single 12AU7 tube, I'd be grateful
>
> >> >> Thanks
> >> >> Dave
>
> >> > Oops, forgot the link to the preamp kit,
> >> >http://secure.oatleyelectronics.com//product_info.php?products_id=722
>
> >> > They do have (had) another similar preamp with an audio input, but
> >> > none are in stock now (discontinued)
>
> >> Can you upload the regen schematic to a picture host and post the link?
>
> >http://www.oldradios.co.nz/hikers/, it's the 1951 Improved Hiker's one
> > valve
>
> Replace the headphones with a logarithmic pot - the kit instructions should
> indicate the resistance value to use, you need to make sure the pre-amp's
> input capacitor's working voltage is rated to withstand the full HT on the
> regen, or you could add a coupling capacitor to the pot's wiper.
I just built a two transistor (BC549,BC558) preamp kit that works
well, will use that. I have a question regarding another regen I
have. The 45 volt HT is placed across the headphone terminals, how
would I connect an IC based amp to the radio, without frying the chip?
Schematic of the radio is at http://www.schmarder.com/radios/tube/1-30.htm
(bottom of page, not my website). Nice looking vintage style radio,
the top corners have been rounded off since (not by me), updated
pictures are @ http://www.flickr.com/photos/ozguy89/
Dave
Australia
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Author: ian fieldDate: 10:50 20-06-08
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"Dave.H" <the1930s@googlemail.com> wrote in message
news:1b4426d2-160f-4fca-a3f1-293899c63bae@w4g2000prd.googlegroups.com...
> On Jun 20, 12:42 am, "ian field" <dai....@ntlworld.com> wrote:
>> "Dave.H" <the19...@googlemail.com> wrote in message
>>
>> news:404015e4-00e7-40f0-badc-1a5beb73ba39@h1g2000prh.googlegroups.com...
>>
>>
>>
>> > On Jun 19, 1:46 am, "ian field" <dai....@ntlworld.com>
wrote:
>> >> "Dave.H" <the19...@googlemail.com> wrote in message
>>
>>
>>news:5a943c3d-af76-42d7-8745-2dfc65a2bc3c@a9g2000prl.googlegroups.com...
>>
>> >> > On Jun 19, 12:23 am, "Dave.H"
<the19...@googlemail.com> wrote:
>> >> >> I have found a valve preamp kit in an online store, to go
between
>> >> >> an
>> >> >> amplifier based on an LM380 chip, and a crystal or regen
radio, but
>> >> >> it
>> >> >> uses a microphone where I want an audio input. If anyone can
tell
>> >> >> me
>> >> >> how to connect an audio in one this or give me a schematic
for a
>> >> >> low
>> >> >> voltage preamp using a single 12AU7 tube, I'd be grateful
>>
>> >> >> Thanks
>> >> >> Dave
>>
>> >> > Oops, forgot the link to the preamp kit,
>> >>
>http://secure.oatleyelectronics.com//product_info.php?products_id=722
>>
>> >> > They do have (had) another similar preamp with an audio input,
but
>> >> > none are in stock now (discontinued)
>>
>> >> Can you upload the regen schematic to a picture host and post the
>> >> link?
>>
>> >http://www.oldradios.co.nz/hikers/, it's the 1951 Improved Hiker's one
>> > valve
>>
>> Replace the headphones with a logarithmic pot - the kit instructions
>> should
>> indicate the resistance value to use, you need to make sure the pre-amp's
>> input capacitor's working voltage is rated to withstand the full HT on
>> the
>> regen, or you could add a coupling capacitor to the pot's wiper.
>
> I just built a two transistor (BC549,BC558) preamp kit that works
> well, will use that. I have a question regarding another regen I
> have. The 45 volt HT is placed across the headphone terminals, how
> would I connect an IC based amp to the radio, without frying the chip?
Put a resistor of the same resistance as specified for the phones in place
of the phones, then couple the plate/anode to the top of a volume pot via a
non-polar capacitor (0.1 - 0.47uF) rated to withstand the HT and take the
O/P to the IC from the wiper - the bottom of the pot is obviously taken to
ground.
You may find the IC input impedance is a little on the low side (often less
than 47k) resulting in not much volume, an easy quick fix is to add a simple
JFET source follower between the wiper and the IC amp chip - take the Vdd
from the IC supply rail.
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