Transistor Preamp

iPod 5G makes 1V output level. What is the input voltage that drives your DIY amp to full power? You probably only need 6dB voltage gain (2x.)

An opamp with 10k resistor in feedback loop will give you the +6dB gain, and is adequate performance for iPod source quality. I like ST Micro MC33079 dual opamp.

Something like this from Rod Elliott:
An externally hosted image should be here but it was not working when we last tested it.


Also, see his full page of preamp circuits, some are discreet (not opamp)
ESP Projects Pages - DIY Audio and Electronics
 
Any good small, easy, high fidelity transistorised preamplifier circuit that i can build ? Plan to use it with my DIY power amp. The preamp should be able to accept ipod level input.

Any help would be appreciated.
Try Rod Elliott P37A, may be not as good as OPA2132, but at least you should try once in your life :D
An externally hosted image should be here but it was not working when we last tested it.

You shouldn't use capacitors in the output if you can trim the VR1L to set output as close to 0V as you can or the following stages already have AC coupling caps. If must use, you should use film or paper or PIO cap like WIMA MKP10 (2x 10uF in parallel) or Mcap or K40U.... Avoid bipolar capacitors since they are not good if long-term stable is required.
 
For ipod and other devices with headphone output on can use step-up transformers.
High fidelity coupling transformer are expensive and clumsy, especially in stereo mode, if two transformers are placed close together as result of space problem, cross-talk will appear because magnetic field of one transformer will affect the other.
Cheap or medium transformers will sound like crap! Distortion and weak of very low AF.
I think solid-state preamp will be the best choice for: money, space and sound performance.
 
Hi Guys

I know there are different file formats that one CAN use, but who using an ipod will use the highest fidelity format? The source fideltiy is already low, so no circuit suggested is likely to impair the sound.

What circuit is the PA? Is it a chip amp? Any opamp preamp will provide performance better than the ipod output quality. The circuit in post-2 should have a cap in series with the resistor to ground in the feedback loop. This will assure minimum output DC offset. otherwise, there could be a tiny DC voltage at the output that could upset the PA input.

NEVER use paper dielectric capacitors. They dry out over time and change their characteristics and cause high signal loss. A customer brought me an old amp that had very low output. I replaced the paper coupling caps with modern plastic types and the amp had its full power again. So, actually i stand corrected by myself: paper capacitors will impair the sound of even an ipod.

Digital audio can sound quite amazing but no such system I've ever heard used an ipod.

Have fun
 
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I like Apex designs - they are easy to make, work, and sound good.

BJT:
165433d1270333407-100w-ultimate-fidelity-amplifier-apex-bjt-preamp.jpg


FET:
165430d1270331111-100w-ultimate-fidelity-amplifier-apex-fet-preamp.jpg


165434d1270333729-100w-ultimate-fidelity-amplifier-big-163027_apex-20preamp-20-284-29.jpg


More here:
http://www.diyaudio.com/forums/solid-state/164093-100w-ultimate-fidelity-amplifier-6.html
 
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James Bongiorno is the designer of Ampzilla and other famous products.

Here is an article he wrote for the June 1972 issue of Popular Electronics, with the modest title

Build a Distortionless Preamplifier

Oops since it is bigger than the max filesize for .pdf here on DIYA, I have extracted each page of the article individually. There are 5 pages and 5 .pdf files attached. Sorry for the annoyance.
 

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James Bongiorno is the designer of Ampzilla and other famous products.

Here is an article he wrote for the June 1972 issue of Popular Electronics, with the modest title

Build a Distortionless Preamplifier

Oops since it is bigger than the max filesize for .pdf here on DIYA, I have extracted each page of the article individually. There are 5 pages and 5 .pdf files attached. Sorry for the annoyance.

Thanks mark. I am unable to open the pdfs can you upload the full article on rapidshare and paste the link here.
 
James Bongiorno is the designer of Ampzilla and other famous products.

Here is an article he wrote for the June 1972 issue of Popular Electronics, with the modest title

Build a Distortionless Preamplifier

No doubt Mr. Bongiorno was a talented designer, but I can't believe that a 44 year old design can't be matched or surpassed with today's transistors and/or op-amps.

Also, why would you need all the gain of a phono preamp for an iPod?
 
Keep it simple, Rod Elliot´s single dual Op Amp (TL072 or similar) is already better than what you need.
Agree to adding a capacitor to ground so it has minimal offset.
And even a non polarized electrolytic will do fine.

One important question: what DC Voltage supplies does your ready built amp have?
Because we can probably supply your preamp from them with little effort.
 
Keep it simple, Rod Elliot´s single dual Op Amp (TL072 or similar) is already better than what you need.
Agree to adding a capacitor to ground so it has minimal offset.
And even a non polarized electrolytic will do fine.

One important question: what DC Voltage supplies does your ready built amp have?
Because we can probably supply your preamp from them with little effort.

Thanks I will try that but I really want a transistor based preamp. I just like the warm fuzzy sound. Chips sound shrill imho.

My power amp is powered by 45 v dc dual supply
 
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Octopart.com was able to find current production devices for the Bongiorno design, see figures below.

Its gain is set by feedback resistors R16, R17, R8 whose values you, the year_2016 circuit designer, can set however you like. Since this isn't a RIAA phono amp you would naturally omit switch S1 and omit the entire "G" signal path (R13, R14, R15, C7, C8).

It is interesting that Bongiorno feels his regulated DC power supply is more elaborate than the power supply designs in other 1972-vintage preamps, AND he feels this is crucial to the ultimate performance of his design. Maybe you could add your own year_2016 innovations and improvements to this portion of the circuit, and get something even better than Bongiorno did, 44 years ago.

_
 

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