Planning to design a low cost tube phono preamplifier. After searching on the web I realized a phono preamplifier should have the following features:
1. High gain. Normally 40 to 45dB
2. A RIAA circuit is necessary
3. High input impedance is needed for piezeo phono head
4. Low input impedance is needed for magnetic phono head
I found a very simple circuit designed by 7025 (12ax7), attached below. Is ther anybody had tried this circuit? How about the performance?
THe output impedance is 220kOhm, maybe too high for some power amplifiers. I think a cathod follower should be added.
1. High gain. Normally 40 to 45dB
2. A RIAA circuit is necessary
3. High input impedance is needed for piezeo phono head
4. Low input impedance is needed for magnetic phono head
I found a very simple circuit designed by 7025 (12ax7), attached below. Is ther anybody had tried this circuit? How about the performance?
THe output impedance is 220kOhm, maybe too high for some power amplifiers. I think a cathod follower should be added.
Attachments
There's already about a million companies offering kits based on these not-terrific and poorly-performing designs. Why not do something different? I would agree with Lars, if you want to offer something and your design chops aren't up to it (your last post confirms that), hire someone to do it for you.
Hi SY, this one isn't a kit, just a trial project. Maybe we'll offering phono preamp kit in the future, but not this one.
I just courious about phono because many people mentioned about it at this digital time. I just want to give a try, my personal hobby project. My phono player is still on the way.
I wish I can find someone to do it, but it's not easy to find an experienced tube amp designer here.
BTW, what do you think can be 'different' from the other 1 million companies products?
I just courious about phono because many people mentioned about it at this digital time. I just want to give a try, my personal hobby project. My phono player is still on the way.
I wish I can find someone to do it, but it's not easy to find an experienced tube amp designer here.
BTW, what do you think can be 'different' from the other 1 million companies products?
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It would be nice to have one with good RIAA conformance, low distortion, low input capacitance, high overload margins, and fast recovery from overload. If I were you, I'd spend a few days going through the preamp chapter in Morgan Jones's "Valve Amplifiers."
Morgan Jones said:
Yes, we have noticed lots of poor valve designs coming from over there. I guess that is why the unscrupulous copy other peoples's designs. Surely someone in China knows how to do valve audio?siliconray said:
High quality genuine components? Proper safety features? Genuine CE mark earned by careful analysis and testing for EMC and safety, backed up by real documentation? That would set you apart from many of your rivals.
You can self certify and use the CE mark, but be prepared to back it up with good records showing that you verified compliance with the requirement. Getting a test house to do this work is well beyond the reach of most small businesses. (It is very expensive)
CE mark in this context would generally be understood to apply to a finished product rather than something like a pcb based board kit.
This is not a requirement for selling in North America, but is for selling finished products in the EU. I've heard of no instances where this was applied to hobbyist projects, and hope that continues to be the case.
CE mark in this context would generally be understood to apply to a finished product rather than something like a pcb based board kit.
This is not a requirement for selling in North America, but is for selling finished products in the EU. I've heard of no instances where this was applied to hobbyist projects, and hope that continues to be the case.
Preamp RIAA
Hi SY, I did think one of the best pre RIAA on a project basis WAD / Hi-Fi World DIY/. I added only one ECC83 - parallel input and changed the power supply.
I've done different versions of the system. Regards Dinkers
Hi SY, I did think one of the best pre RIAA on a project basis WAD / Hi-Fi World DIY/. I added only one ECC83 - parallel input and changed the power supply.
I've done different versions of the system. Regards Dinkers
Attachments
![preriaa]p-oi.jpg](/community/data/attachments/253/253661-55025d877686aa76320f5dd59a508ad8.jpg)
pre RIAA WAD
Yes, I have seven pages for a full description. I tried everything posted on the diyAudio forum, but it is too large file
We are happy to make available on the mailbox, or will put on one side turn on the diyAudio forum. I can do it tomorrow
I want to point out that a lot of working on a good pre RIAA, because I listen almost exclusively to LPS. I tried to do a replica of the layout of the SRPP Audio Note and other systems. WAD is the best! Below is a photo posted M2 Phono and my version of WAD. Regards Dinkers
Yes, I have seven pages for a full description. I tried everything posted on the diyAudio forum, but it is too large file
We are happy to make available on the mailbox, or will put on one side turn on the diyAudio forum. I can do it tomorrow
I want to point out that a lot of working on a good pre RIAA, because I listen almost exclusively to LPS. I tried to do a replica of the layout of the SRPP Audio Note and other systems. WAD is the best! Below is a photo posted M2 Phono and my version of WAD. Regards Dinkers
Attachments
Thanks Dinkers, I'll read more aritcals about RIAA and phono amplifier at my spare time. Hope my first phono amp can be done in one month.
We have a server and a image management system. You can send me the files, I will upload to our server and post the links for download. My email: mike@ezpcb.com
We have a server and a image management system. You can send me the files, I will upload to our server and post the links for download. My email: mike@ezpcb.com
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pre RIAA WAD
Yes, a miniature diagram - this is WAD / World Audio Design /. Schematic SRPP / M2 Phono / is a system of original Audio Note. Do not have a scanner and I can now embed individual pages WAD. I think this is one of the best projects in general and RIAA phono preamp. Complemented by a step-up transformers can work with MC cartridges. In the picture my version of WAD with step-up
Regards Dinkers
Yes, a miniature diagram - this is WAD / World Audio Design /. Schematic SRPP / M2 Phono / is a system of original Audio Note. Do not have a scanner and I can now embed individual pages WAD. I think this is one of the best projects in general and RIAA phono preamp. Complemented by a step-up transformers can work with MC cartridges. In the picture my version of WAD with step-up
Regards Dinkers
Attachments
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