RB300...what a donkey to set.
Pivot to spindle mounting confusion, tracking force precision hassle, no VTA and no azimuth adjustment, a nightmare! And still on my TT.
@Erlend
Aha, that explains it. Absolute tastes differ but surely he could hint you about carts and arms to consider synergistic for getting in different cost brackets for the FSP after he puts it through a part of his collection. Whatever tips you will know from him, people here l am sure will be happy to know too.
Aha, that explains it. Absolute tastes differ but surely he could hint you about carts and arms to consider synergistic for getting in different cost brackets for the FSP after he puts it through a part of his collection. Whatever tips you will know from him, people here l am sure will be happy to know too.
VTF...wind it to full so the coil preloads near nothing, then use the counterweight and a scale only. The arm breaks free then. VTA...have various mats. Azimuth...forget. Anti skating...lost in space. Just take it to zero and add only a little bit if the image center feels to the right. Anyway after set in paranormal way it results in a big sound with wide stage and fleshy mids. Bass and treble are kinda technicolor still.
The Danes are transducer specialists we don't forget. Ortofon, B&K, high tech loudspeaker drivers, a long tradition.
Remeasured values, although I am unsure what you mean by "loaded". Would you like me to put a resistor across the output?
After a long warmup...
DC in 43.5V, set using variac, transformer would do 50V!! I will be changing the R in my CRC to a larger resistor.
Rail+ 33.4V, I can not set this higher as I run out of adjustment for VR1
---- Left _ Right
TP1 7.67 7.68 to ground
TP2 4.07 4.08 to ground
Gain at 1kHz
Input 5.01 mV, bounces around this value, both sides connected
Output mV
Left Right
481 474, drifts quite a bit due to signal source. Values are approximate.
I'm not sure if this helps, but the room temperature was about 15C.
Thanks for looking at this
Jim
That's what I do. Though, I set it to 3g as suggested by OL.
Not bothered actually.
Ahh, will try. Although I've done it with HFN test record and 3 inner, outter and middle bias setting tracks to dialed to get minimum distortion.
You can experiment with rear end and arm mounting pilar tightening. Not to tight not too loose is the key for not too bloated or no too thin bass.
Measuring the test signal source on 47K or whatever the phono presents it, not on just the 10Meg a DMM will show it I meant.
Your now figures suggest 39.5dB. Talking nominal within experimental error and very close channel matching. You hit a good build electrical result.
I did, its as nice as an RB300 gets. With a 103R its a fat bold deep and wide presentation. Not best in accuracy, but a spoiled audio kids candy factory.
Measuring the test signal source on 47K or whatever the phono presents it, not on just the 10Meg a DMM will show it I meant.
Salas,
The test signal was set and measured while simultaneously connected to the left and right phono inputs. After setting/measuring the test signal the probe was moved to the left output. The right side output was connected to the second channel of the Tek TDS 210. The important DC voltages were measured with a DMM. A VTVM was used on the DC input but only because I like the big analogue meter.
I should have, but did not recheck the test signal voltage at the end. Silly me, the old Heathkit IG-5218 would have drifted. I will remeasure things, hopefully tihs weekend. Would you like me to change the procedure?
Thanks
Jim
Also some benefits or losses might depend on the TT. Wonder how does it compare to your arm? Wider presentation and fatter bass?
That was alright technique, similar to have simulated on 24K load. You are at the drift and noise limits of your gen probably, I don't think it will get any more repetitive and it looks safely close to nominal gain and channel matching. Excellent build tolerances you got for non NFB set gain. FSP is like building a tube non NFB overall loop phono only with silicone pentodes.
The Mission 774 was not a budget arm in its time. Has all necessary stuff, VTA, overhang, azimuth, far better bearings, damping trough, exact side hanging anti skate, sorbothane decoupled counterweight on threaded shaft, SME base, and the particular one is Cardas rewired. It only needs either extra mass or to engage the paddles and fluid for low compliance cart. Its basically neutral and it gives its best without extras for mass and damping when using carts like AT33PTG/II with it. Wins hands down on bass and treble resolution a stock Rega.
Its such budget mid weight monocast arms with rather agricultural bearing tolerances bounce along nicely on classic English Sondek school TTs giving good helpings of midbass, spectral mids and 3D but with some guessed at resolution beyond the basic portion plus greyer layering at the spectrum's edges. IMHO of course. On the other hand the 774 was designed by an American race cars engineer like a thoroughbred and its critical parts were machined in Japan if I remember correctly.
My CJ58's pulley started kicking the bucket, till DC motor mod, a spare TT. RB300...what a donkey to set.
Nice spare, I have always been fond of the Systemdeks. I've got a RB300 on my Thorens. When I finish the Folded I will swap in my Ortofon moving coil, and yes, not looking forward to the setup process.
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Both boards are 99% finished, just waiting on 6*470uF caps, which are supposed to ship next week. Cases are ordered and will arrive later this month. When the electrolytics arrive I'll install them and mock up the raw PSU's and do the initial bias setup. You may recall my transformers are a bit too high output, so I'll have to mess around a bit to get the raw voltage where I want it before I connect it to the folded PCBs.
Impressions so far: The boards are very nice, well laid out, easy to build up. I spent quite a bit of time measuring and selecting 2SK117's and diodes. For example, after selecting two K117's with very close Idss for Q7 I built a little jig, mounted the first Q7 in a socket, and a string of red LED's, and swapped LED's until I got a voltage that was close enough to 7.75V but not over, then inserted the other Q7 and tried LED's until I got exactly the same voltage. Similarly with Q2x, and I measured and sorted 16 2SA970's to find the "right" two Q3Z's, and went through a bunch of BC550's to select two for Q4x. This process of measuring, sorting, and selecting parts is time consuming, but it is also kind of fun, and I hope ultimately rewarding as it allows a level of matching that would seldom be found in a commercial product. Like I said before, this would be no fun if it was a paint-by-numbers kit or finished too soon! 
I have an op-amp based phono stage for MM carts that I like very much, and the Folded will be my MC stage. If it is half as good as reported by those who have built it so far, it will probably be my last phono stage. I look forward to listening, but I also enjoy building these things and will not rush the process.
It is also the first, and perhaps last, time I have used some of these "boutique" parts like naked Z-foils and exotic caps (I guess semi-exotic in today's marketplace, but at least one order of magnitude more expensive than anything I have bought or used before). Still not sure how I feel about that, but it seemed to be in the spirit of this build.
Also, spending time reading the schematic and the build guide while building has helped me to "grok" the circuit a little more, and that is always a win. In other words, I'm having fun so far, and anticipating more fun! (The case-work is always a PITA but ultimately satisfying when it all comes together.)
I have an op-amp based phono stage for MM carts that I like very much, and the Folded will be my MC stage. If it is half as good as reported by those who have built it so far, it will probably be my last phono stage. I look forward to listening, but I also enjoy building these things and will not rush the process.
It is also the first, and perhaps last, time I have used some of these "boutique" parts like naked Z-foils and exotic caps (I guess semi-exotic in today's marketplace, but at least one order of magnitude more expensive than anything I have bought or used before). Still not sure how I feel about that, but it seemed to be in the spirit of this build.
Also, spending time reading the schematic and the build guide while building has helped me to "grok" the circuit a little more, and that is always a win. In other words, I'm having fun so far, and anticipating more fun! (The case-work is always a PITA but ultimately satisfying when it all comes together.)