The easiest solution is to switch your phono pre to one that has at least 3 inputs (Aesthetix Rhea for example but many others as well depending on your budget).
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If you have the real estate on your present preamp just add a selector switch and two more sets of RCAs. Or have a tech do it for you. It should be on the back panel and should do the switching before the active circuit. I converted the first three inputs on my preamp to be phonos, but I have six turntables and may have to add a few more inputs. Who says we're normal!
The use of a passive preamp is interesting as well as installing a home made switch with rca jacks. It may end up I do one of these options.What I was hoping is to find a product that was designed to do exactly what I need. It seems that the need for a device such as this exists in other applications besides turntables and tonearms.
Bob there are certainly passive preamps with switching or devices such as the Manley Labs Skipjack, which is a very high quality input switcher. The problem is that the phono signal is the smallest, and most frail, signal in your entire system. Do you really want to add a switch box followed by another set of interconnects and have that signal compromised even further? Not to mention the variable of capacitance in adding all of this stuff. It's not a desireable answer at all. Better to get a phono preamp design that accomodates multiple inputs, modify your existing phono stage or add other phono preamps and run then into your available line inputs.
Bob, to do what you want to do is a compromise, and you will have switches in the signal path before the RIAA EQ lifts the voltage of the signal, unless you use seperate phono preamps into seperate line level inputs in your preamp.
That said, if you choose to use swiching, keeping the wiring as short as possible, with the least amount of breaks, makes the most sense, and that generally calls for switching right at the input of the phono preamp. You still will have the switch contacts and the short lengths of wire, but at least you don't have the breaks and cable effects of additional interconnects and their added capacitance as well as the overall longer signal path.
I had a similar dilema, three tables and one phono section, a Fon Lo Thingee by Blue Circle. I liked it so much I had a custom Phono section made by Blue Circle that incorporated three Fon Lo Thingee Phono sections put into a "Proper Box" with a Grayhill three position selector switch going to one output. Each phono section has its own input with selectable gain and loading. The design utlized the existing Biggee power supply and SP capacitor pack to save a few dollars. I think it is really great and perfect solution for me.
With my budget I think that the idea of adding a selector switch and phono jacks at the preamp is the way to go. I will get the switch and jacks from an old receiver. No real estate on the pre so I'll make a box that rests on top and will enter thru the rca holes once the jacks are removed and hard wire direct. If I ever want to trade to another pre it will be simple to restore to original. Anything I have overlooked or need to consider is welcomed and encouraged.
I remember talking to one of Stuart Hegeman's technicians back in the early eighties about modifying my Hapi 2. He emphatically advised me that it was a bad idea. It seems that the topography of a preamp is very important and is taken into consideration during it's design. Adding extra RCA jacks and a selector switch might have the effect of creating an antenna to catch stray RF noise from the circuit and ruining the entire preamp. Needless to say, I took his advice. If I were to have 3 tonearms and cartridges, I would get 3 separate preamps. Keep it simple (circuit wise).
Thanks for the advice Heyraz. That will lead to the same problem at the final preamp. Maybe Veridian can comment on the results of his conversion with the addition of the selector switch. I am learning that most every change is a compromise in some regard.The simplest compromise is the financial one but it is also the most difficult to justify in these times.
Bob, I did not find much loss in my conversion, but my system is tuned for tone, not high resolution, so Ymmv. I also have a preamp with an integral phono stage and just took two of the extra line level inputs and ran them to the phono stage, a different animal than what you will be doing.
On the other hand, you can buy a small project box for $8.00, four sets of RCAs for another $15.00 and a selector switch for less than $10.00 and you are there and can make up your own mind. If it works for you, you can hardwire it in. Cheap and simple. Just keep those signal paths as short as possible.
Unfortunately, finances are always the impediment. My preamp (Forte 44) has 5 high level inputs, so I could get away with 3 discrete tonearm/preamps. If I were limited to one preamp input, I'd probably swap cables whenever I decided to listen to a different tonearm/cartridge for the cleanest possible sound. Otherwise, what's the point. Besides, how often to you think you'll be swapping? Weakest link in the chain theory carries much significance with me. Cool idea though, 3 tonearms. Much easier than changing headshells.
Heyraz what you say makes good sense and that is what i've been doing. It creates problems with location of equipment to make it accessable and out of the way.Thought if it didn't sound good I could allways go back to cable swapping.
I will try the box I described a few posts back and hear the results.I'm pretty sure something will be lost but if I'm lucky I won't be able to detect it with my old ears. If I can hear it than in the trash it will go as it was going anyway and back to cable swapping. And BTW you or at least I would switch very often if it was easier. Since I don't have the one perfect needle, cartridge and tonearm some records may sound better with a differant approach.In fact some records do sound better , what works best for one doesn't allways work best for others.
I have 2 cartridges now, a Grado Signature 8 on a spare headshell and a Grado Reference Sonata 1 that I listen to. I recently swapped back the Signature just to check it out again, but I didn't even bother finishing one side. The Sonata was so much more refined, I'm giving the Signature to my son. I like your approach though, and I plan on trying out other cartridges in the near future. Your turntable project must have cost a lot of money, good tonearms alone aren't cheap, never mind the cartridges. I thought if you were going to the expense of assembling such an instrument, you would want the best possible scenario. In fact, I'll bet you end up with the 3 discrete setups I described earlier or finding a preamp with more than one phono input. BTW, have you considered using a line preamp in front of your main preamp to handle handle phono preamp switching? I picked up a used Acurus preamp from ebay for around $300 recently, it has 6 high level inputs. I own 3 phono sections, all sounding different, but I settled on the one I preferred. The argument could be made some music sounds better on one preamp than the another. I'll bet there's as much character in a preamp as there is in a cartridge. You know, tube vs solid state.
Well to take the guessing out I will tell you I am using an ATP-12T with an AT-160LC , AN AT-1010 with a SIGNET TK7E and an EPA-100 with an AT-150MLX going to a UREI transcription preamp that has been custom modded by a shop here in town. Also use an ADCOM GFP-400 for now which has an excellent phono section.(my opinion)The reason for the 1 table with 3 arms is to thin out my office / listening room by removing some of the turntables I have. The custom plinth is an experiment using 3 layers of 3/4''in. MDF with 2 layers of 1/2''in. hardy cement board sandwiched between. Results are amazing. This is rock solid and I cannot hear any feedback at all. My room is 12 X 12 and can play very loud with no audible feedback that I can hear. That was definatly not the case prior.