Hi records lovers!
I try make homemade record lathe and decided to join your ranks)
I recently purchased a Astatic Crystal X-26 for experiments
Heard that the head of this input is required 500Ohm
But I do not have such devices. All my amps maximum 4-16Ohm
Advise please, maybe there are options to buy a complete device with 500Ohm output on Ebay?
Maybe a headphone amplifier? I see different models from 32 to 600 ohm output
Regards
Amplifer for Astatic Crystal Head and other
Moderators: piaptk, tragwag, Steve E., Aussie0zborn
Amplifer for Astatic Crystal Head and other
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Re: Amplifer for Astatic Crystal Head and other
Hi,
The first issue is to determine if the head is good. Most of these heads are bad due to the fact that the Rochelle Salt crystals used do not age well (they absorb moisture easily). You may have to have it rebuilt.
These heads were meant to be driven by a high voltage, low current source. That was typically done by driving the head directly from the plate of a simple single ended class A tube stage (e.g. 6AQ5). Normally, the plate would drive an output transformer that would match the low impedance of a typical speaker to the high impedance of the output tube. If you find a small tube amp, it would not take to much work to re-purpose it for this application. Look for schematics for a typical Recordio and you'll get the idea. If you don't want to drive via a tube amp, you could get by using a 70.7 volt PA transformer in reverse. If you drive the 8 ohm 5 watt secondary tap of the transformer from you power amp and connect the head to the 70.7V primary, you'll be in the ballpark of the needed drive level (still a bit low). If you have a high power solid state amp available (e.g. 200 watts into 8 ohms), you could use this to get an idea of the head's condition by driving it directly. A 200 watt amp can swing about 40 Vrms at its output just before clipping. While this is very low compared to the 180 Vrms you really need, you should get some response from the head. You won't be drivng much actual power into the head, so there is no danger of smoking it. Most solid state amps are ok to run open or lightly loaded, so that should be ok as well. If you feed a 1Khz tone to the amp and drive it just below clipping (even into clipping), you should be able to feel and possibly hear the head vibrate. This might be a good first step before you sink any time or money into the head and drive amps.
Mark
The first issue is to determine if the head is good. Most of these heads are bad due to the fact that the Rochelle Salt crystals used do not age well (they absorb moisture easily). You may have to have it rebuilt.
These heads were meant to be driven by a high voltage, low current source. That was typically done by driving the head directly from the plate of a simple single ended class A tube stage (e.g. 6AQ5). Normally, the plate would drive an output transformer that would match the low impedance of a typical speaker to the high impedance of the output tube. If you find a small tube amp, it would not take to much work to re-purpose it for this application. Look for schematics for a typical Recordio and you'll get the idea. If you don't want to drive via a tube amp, you could get by using a 70.7 volt PA transformer in reverse. If you drive the 8 ohm 5 watt secondary tap of the transformer from you power amp and connect the head to the 70.7V primary, you'll be in the ballpark of the needed drive level (still a bit low). If you have a high power solid state amp available (e.g. 200 watts into 8 ohms), you could use this to get an idea of the head's condition by driving it directly. A 200 watt amp can swing about 40 Vrms at its output just before clipping. While this is very low compared to the 180 Vrms you really need, you should get some response from the head. You won't be drivng much actual power into the head, so there is no danger of smoking it. Most solid state amps are ok to run open or lightly loaded, so that should be ok as well. If you feed a 1Khz tone to the amp and drive it just below clipping (even into clipping), you should be able to feel and possibly hear the head vibrate. This might be a good first step before you sink any time or money into the head and drive amps.
Mark
Re: Amplifer for Astatic Crystal Head and other
Hi Mark!markrob wrote:Hi,
The first issue is to determine if the head is good.
Mark
First time i connect this head to litle 2,5W laptop amplifier, and
I heard a very, very soft volume music from the crystal head. barely audible
Yes, i have hybrid vacuum tube amplifier - 75 W (8 ohms), 110 watts (4 ohms) Magnat MA800
If i connect w head to my amplifer speaker output I do not burn my Crystal Head?
Thank you for answer!
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Re: Amplifer for Astatic Crystal Head and other
I find manual!
I will be glad if it is same would be helpful to someone
I will be glad if it is same would be helpful to someone
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Re: Amplifer for Astatic Crystal Head and other
I connect crystal head to MA-800 speakers output, set volume to max, and play generated tone - no head vibration, only little noise from inside head.markrob wrote: If you have a high power solid state amp available (e.g. 200 watts into 8 ohms), you could use this to get an idea of the head's condition by driving it directly... If you feed a 1Khz tone to the amp and drive it just below clipping (even into clipping), you should be able to feel and possibly hear the head vibrate.
Mark
I try play music, and I heard barely audible music inside this head
Re: Amplifer for Astatic Crystal Head and other
Hi,
If you have one available, measure the AC voltage across the head when you play the 1Khz tone. Make sure you see a voltage that is correct given the maximum power specified for you amp.
Use the formula V = Sqrt(P X R). For example, if you amp is 200 Watts into 8 ohms you would expect: V = Sqrt(200 x
= Sqrt(1600) = 40
If you have one available, measure the AC voltage across the head when you play the 1Khz tone. Make sure you see a voltage that is correct given the maximum power specified for you amp.
Use the formula V = Sqrt(P X R). For example, if you amp is 200 Watts into 8 ohms you would expect: V = Sqrt(200 x
= Sqrt(1600) = 40Re: Amplifer for Astatic Crystal Head and other
Hi!markrob wrote:Hi,
If you have one available, measure the AC voltage across the head when you play the 1Khz tone.
Thanks for answer
I think my amplifier most likely weak for this head.
But if I hear silent music from the inside of the head, so it works?
May be anyone know how i need to work this head?
Can you suggest any complete solutions, with link to ebay?
There may be ready devices allow get 500Ohm output?
Re: Amplifer for Astatic Crystal Head and other
Hi,
The real test would be to try cutting with the head. Also, I would try to attach a cutting stylus or something to stand in place of it. I've used a 1/16" drill for this purpose. Then try running a lower frequency tone to the head (e.g. 100hz). You should be able to feel the stylus vibrate.
Mark
The real test would be to try cutting with the head. Also, I would try to attach a cutting stylus or something to stand in place of it. I've used a 1/16" drill for this purpose. Then try running a lower frequency tone to the head (e.g. 100hz). You should be able to feel the stylus vibrate.
Mark
-
Lima Victor
- Posts: 15
- Joined: Sun Feb 16, 2014 3:43 pm
Re: Amplifer for Astatic Crystal Head and other
One of these transformers will probably do the job: http://www.ebay.com/itm/100v-visaton-tr84-speaker-transformer-4-8-ohm-/350583659391?pt=BI_Circuit_Breakers_Transformers&hash=item51a06a1b7f
Make sure to put some load (let's say a 10w 1000 ohm resistor) on the secondary of the transformer. The capacity of the cutting head, together with the inductance of the transformer, will form a resonant circuit which will resonate wildly and - if there's a tone on the right frequency - might blow your cutting head or the insulation of the transformer. Loading the transformer will reduce this effect. Putting another resistor in series with the head will reduce it even further.
Make sure to put some load (let's say a 10w 1000 ohm resistor) on the secondary of the transformer. The capacity of the cutting head, together with the inductance of the transformer, will form a resonant circuit which will resonate wildly and - if there's a tone on the right frequency - might blow your cutting head or the insulation of the transformer. Loading the transformer will reduce this effect. Putting another resistor in series with the head will reduce it even further.
Re: Amplifer for Astatic Crystal Head and other
Hi!Lima Victor wrote:One of these transformers will probably do the job: http://www.ebay.com/itm/100v-visaton-tr84-speaker-transformer-4-8-ohm-/350583659391?pt=BI_Circuit_Breakers_Transformers&hash=item51a06a1b7f
I'll try to follow your advice and buy a transformer later.
Although now doubt that this crystal cutting head in work condition
Now i get "Universal microphone recorder head", its work and easy cut from 5W 4ohm laptop amplifer-speakers .
Thank you!
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