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Inexpensive IC based phono preamp for LOMC
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Author:  Felix [ 23 Sep 2015, 04:48 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

G'day all, just regarding this single op amp phono stage, my admiration for this simple phono stage just grows and grows, especially how wonderfully musical it sounds, despite its circuit simplicity.

I have recently completed another more complex op amp based phono stage project that I had great hopes for but has turned out to be a little disappointing. It sounds fine, but 'sterile' without any of the musicality that Bruce Heran's simple op amp design has in spades.

As a example the other day I was listening to my beloved Dave Brubeck Greatest Hits vinyl album with my new phono stage and whilst it sounded good, I felt no emotional connection with the music at all. The next night I played the same album again with the same gear and cartridge (OEM stylus) Shure M97xE but with this amazing Bruce Heran simple op amp phono stage and I really 'connected' with the music in the most delightful way. Tonight listening to one of the Bach Brandenburg Concerto's on a Philips recording was similarly wonderful! This is a stunningly nice sounding and musical phono stage. I love it! Regards, Felix.

Author:  gofar99 [ 23 Sep 2015, 21:16 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

Hi Felix, I'm glad you like it. It turned out better than I expected and continues to surprise me (and folks like yourself). It fits in with my general philosophy ...simple is often better. But equally, not simple just for simple's sake. Use enough components to do the job without frills. BTW the preamp does a great job in the high gain mode with NAB equalization and 47K input for reel to reel tape playback. I use it with an Akai taking the signal directly off the the heads. It would probably work for cassette play back as well with adjustments to the equalization.

Good listening
Bruce

Author:  wdecho [ 03 May 2016, 06:46 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

I finished building this phono pre last week. Simple little build that sounds great for what it cost. Extremely quite with very efficient horn speakers.

Author:  gofar99 [ 03 May 2016, 10:16 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

Hi, Glad you like it. It is what I call a simple design well thought out. No extra frills in it and everything has a reason to be there. As for quiet....I am an avowed card carrying believer in no noise or hum. Any is really too much so it is a key part of any of my projects. They must not only do what they are supposed to do...but must do it quietly.

For the tube guys....I'm working on an even quieter "Groove" phono preamp. It has been actually an evolutionary process starting about 8 years ago. The most current version is about 2 years old now. I'll post the project when I'm satisfied it does the things I think it should. BTW It should be possible to update versions from 2010 or newer without a great deal of problems.

Good listening
Bruce

Author:  dlucy67 [ 03 May 2016, 10:31 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

gofar99 wrote:
For the tube guys....I'm working on an even quieter "Groove" phono preamp. It has been actually an evolutionary process starting about 8 years ago. The most current version is about 2 years old now. I'll post the project when I'm satisfied it does the things I think it should. BTW It should be possible to update versions from 2010 or newer without a great deal of problems.


That's great news! I'm looking forward to it. Please post as soon as you can.

Author:  gofar99 [ 03 May 2016, 11:00 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

Hi, Will do that.

A tidbit on the IC phono preamp..... if you have a cartridge that has imperfect channel balance (say 1-4 db) and is really worth the effort. I have one MM like that. You can change the value of the 300/330R resistors in the inverting side of the ICs to 50/82R and an put a 500R linear trim pot between them with the center tap going to ground. This will give you a major balance control (many DB) and will even work if the cartridge is LOMC when in circuit with the 47/51 ohm resistors in parallel. You can of course use other values of pot and resistors to obtain the same effect. In the MM mode the actual shifts in frequency response are insignificant for typical settings. In the LOMC mode with an extreme offset toward one channel they might become noticeable....but then if the cartridge is that far off then it probably isn't worth the trouble to keep around.

Good listening
Bruce

Author:  wdecho [ 03 May 2016, 14:09 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

This build was the second one of your designs I have built, the other being the ECC802S SRPP Tube Preamplifier and I am impressed with both of them. I am tempted to try one of the push pull amplifiers even though I am a devoted SET fan.

Author:  gofar99 [ 03 May 2016, 14:46 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

Hi, Glad you like them. The Dual Mono Block version or the mini mono blocks are the ones to try. You will not believe they are push-pull. We have at least on commercial vendor using them as replacements to his 2A3 SETs in sales demos (he does high end speakers). His opinion (I agree) is that they sound more like a really premium SET than most premium SETs do. A key thing if you do build them is to not change the output transformers. I had Edcor design them just for these amps. A bit more costly than some others they have but IMO well worth it. They run just about $50 US. A bargain IMO. The amps deliver 5 watts rms so that on occasion can be a limitation. If you need more muscle any of the bigger amps can do the job, but while they don't sound like your typical P-P amp (which IMO is a good thing) they are not quite as magical in low power applications as the EL84 amps. All IMO are great amps, but there is something about EL84s that is special. All the above is clearly OT, but them it is my topic anyway. Sorry.

Good listening
Bruce

Author:  mwhouston [ 03 May 2016, 15:02 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

I went for the Decware inspired schematic for my DIY EL84 and love the little amp. My DIY 300B with much bigger OPTs and double the watts is better but at many times the price.

Getting back to the phone preamp of Bruce's, they have been getting rave reviews here is Australia. I have built and sold quite a few, all battery powered. A local forum I'm on, which is not wholly DIY, has been the main source of my sales. Those who buy one love them and post thier reviews. In fact I'm right in the middle of making one to go to Perth, Australia now. These and DC blockers have been great little sellers. Some how I have to thank Bruce with more than just words. I do know though he will be pleased that the simple design is so good.

Author:  wdecho [ 04 May 2016, 06:13 ]
Post subject:  Re: Inexpensive IC based phono preamp for LOMC

I am in need of a new project and I am almost convinced to build the mono's EL84's. I do not need more than a few watts with my speakers. I have one SET with just 1 1/3 watts and it is as strong as all others I have. I have a friend that I talked into DIY who has built 2 Firstwatt clones. He has never built from a schematic yet. Would he achieve about the same results with your Poddwatt DMB Series 1 kit you have for sale. I believe he might try to build a complete kit project with some persuasion. He recently purchased a pair of Klipsch Jubilee speakers so wattage is no problem.

Members forgive me for not staying on the subject of SS but it will not hurt anyone to try tubes either.

:D

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