I have built a poindexters 6v6 push / pull amp (4 W output) and now want to build a tube phono pre amp for my music Hall turntable with a Grado Green cartridge. I would like a simple build (not necessarily a kit - more $$) with schematic that a newbie can follow. Does anyone have experience with the Steve Graham Design published in a 6 part series in Wall of Sound last year (2019). Any direction / help would be greatly appreciated.
Thanks so much
Thanks so much
Well, there is this...
Bigbottle MM/MC Hybrid Valve Phonostage PCB
Bigbottle Phonostage Builders thread.
Bigbottle MM/MC Hybrid Valve Phonostage PCB
Bigbottle Phonostage Builders thread.
In a similar vein, there's the Valvewizard Compact Phone Iss.2 which I'm about to build into an existing EL84 PP amp.
I chose this because I am limited to one bottle per channel. If you are making a dedicated preamp you can use more valves
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In a PM, Dan asked about a PSU for the tweaked RCA setup. I'm providing Jeff Yourison's drawing of a cost effective, solidly performing, PSU.
I've also provided RCA's original setup, so that the various tweaks the membership has added can be cross compared. FWIW, RCA's specifying the 7025 was not a sales gimmick. Post WW2, which the design dates to, setting DC heater supplies up was difficult. The spiral wound, hum bucking, 7025 heater allowed a VERY careful builder to obtain a satisfactory residual hum level, with AC heating.
I've also provided RCA's original setup, so that the various tweaks the membership has added can be cross compared. FWIW, RCA's specifying the 7025 was not a sales gimmick. Post WW2, which the design dates to, setting DC heater supplies up was difficult. The spiral wound, hum bucking, 7025 heater allowed a VERY careful builder to obtain a satisfactory residual hum level, with AC heating.
Attachments
Thanks Eli - I may use that PSU for my phono stage. Do you have a slightly higher-res version? That one is just on the edge of legibility (well for my eyes anyway)
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Sorry, but "Onkel Frihu" made very clear, that an SRPP tube amp isn't the best of all tube circuits. He liberated all of his circuits from SRPP and is now more happy with the sound.
He never would advise to build SRPP any longer.
Rohrentechnik: Ave SRPP! – **frihu.com**
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All PCB designs are to be avoided in tube circuits. Great circuits were never build with PCB. This is a modern method for saving cost on building for the manufacturer, because it can be produced automated.
ALL PCB robb the sound of its 3D dimensionality and make it sound boring flat.
This is a passive build RIAA. Most of those passive EQ sound stupid boring.
An active build can do much better.
No, its not e brand new theory. You can read the same recommendations over and over on the net. But, of course not from companies who build with PCB based circuits and even not from listeners who owns such gear.
I will give you an example. Leica is building excellent optics and the so called dogs. Most of the users will say "this is an excellent lens, because I shoot with it" But this doesn't make either a Leica lens excellent nor does it make a PCB based tube pre excellent. The argument is just nonsense, but you will find it anywhere. Listeners, who thinks that their own gear is excellent, because they have bought it.
And furthermore, a " Lab test" doesn't show up how listenable a pre is, same with a Leica lens. You can (and should) engineer such a lens and a pre based on facts not fiction. But at the end, both the lens and the pre is only judged by the eyes and the ears. No one would ever judge a lens just by a lab test and no experienced listener would ever judge a pre only by a lab test.
But of course, there are those electronic designers who claim its no longer necessary to audition gear by the ears, because it was measuring perfect and it was computer aided designed. Such fools.
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My positive contribution results in excluding the negative examples that I have shown already:
-avoid PCB designs whenever possible (and in tube audio its almost always possible)
-build a well knowned design from the famous tube age, maybe Marantz, Shure, EMT, there are hundreds always existing
-avoid passive RIAA equalisation.
That will narrow your search results very much. A ten minute search in google with the infos I've given now should bring two or three very good candidates.
Bring them in here and we can discuss them.
The forum is not for asking a simple question and let others do the work.
We can try to optimise a given circuit and give some important hints. We can not educate on the complete tube phono schematic world outside.
For that, there are legions of huge education books to read.
Surely you don't believe everything you read on the Internet. While there is a lot of useful information out there, a lot of it is just opinion masquerading as fact.
If you want to learn something about the challenges of active equalization, you might give this a read. It is authored by a former contributor on the diyAudio forums. Of particular note is the gain requirement for good equalization accuracy. If it is difficult to get the necessary gain from an op amp, then a vacuum tube will struggle even more. Active equalization also introduces an extra time constant which is not part of the RIAA specification; this requires a work-around so as not to degrade RIAA accuracy at high frequencies.
Phono Preamp Design Using Active RIAA Equalization
You haven't presented any convincing information as to why passive equalization should be avoided. In fact, a lot of respected designers would strongly disagree with you. Some of those designs have already been mentioned; here is another one from the late Allen Wright.
http://www.vacuumstate.com/fileupload/SP_15_Article.pdf
I think (my opinion only!) that the original poster has already gotten some useful suggestions from this thread.
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