Hi there midnight- I have just seen your suggestion- downloaded it from the tubestore.com library- thank you very very much
Sorry I've come a little late to this discussion. I agree with earlier comments that changing the RIAA curve is not a good idea however, your original post got me thinking of the Quad 33 pre amp and filters with a slope control.
I understand (maybe wrongly) that before the agreement on RIAA all record companies had their own preferred EQ settings and this was an attempt by Quad to provide a universal solution. I have thought about building a pre amp with these filters for the very reason you mention. Maybe you could could incorporate the idea.
I understand (maybe wrongly) that before the agreement on RIAA all record companies had their own preferred EQ settings and this was an attempt by Quad to provide a universal solution. I have thought about building a pre amp with these filters for the very reason you mention. Maybe you could could incorporate the idea.
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In my experience some records sound good, some great, some crappy. To me crappy means harsh, bright and irritating- yes it could be my preamp sucks or conversely could we twiddle the knobs a tad to suit? From what I have read not every recording studio/record maker adhered to the riaa protocol to the nth db so all I want to is to tailor playback by choosing which slope sound best.
I've been performing a total overhaul on mine. I've got a c8, and a c8s the stereo companion. They have more adjustments than the average person needs. So far I've found that all of the components I need in order to do so are available from major electronics suppliers. I have not tried to match up the pots, thankfully my pots are fine.
If you're going to have difficulty it will be in sourcing the pots. Lots of variables to get right...
If you're going to have difficulty it will be in sourcing the pots. Lots of variables to get right...
Even with the passive RIAA compensation, the C3G/D3a part has gain of 62dB which is way too much for the AT cartridge.
Hi Mr Mayhem
I have counted many selector switches. The pots are volume (obviously) and the adjustment ones on the back of the unit for the ax7's. I don't suppose there are any markings on the pots in your c8's? That might be helpful.
It begs the question- whether building a variable equalization/gain/slope box twixt pre-amp and amp might be doable- but of course I would need to be more clever than I actually am
A well set up D3a isn't typically harsh. Your problem makes me wonder if there isn't any oscillation. Maybe check and adjust stopper values. Your sketch doesn't show the values used.
On another note entirely, The C3g and D3a connection to G3 gives you the option of putting it to plate rather than to cathode. I've been finding that it can make an audible difference.
On another note entirely, The C3g and D3a connection to G3 gives you the option of putting it to plate rather than to cathode. I've been finding that it can make an audible difference.
Grid stoppers are 1k all round. i will change g3 to anode- do you place a 100 ohm resistor between g3 and anode? It is only harsh on a few notes (if you are familiar with sultans of swing - it is harsh on particular guitar notes and very smooth elsewhere). I am just wondering if it is my operating points. This is what I dont get- which ones do you choose? Perhaps the c3g and 6sl7 worked better in synergy and cancellation of harmonics. I have the preamp mated to Bruce Herrons oddblock kt88 amps- they are strident in their presentation so perhaps it is this combination that is less than pleasant.
I'm no engineer like some of the others in this thread but my experience is that as long as the technical problems are not there (eg like oscillation, over or under loading etc. ) , fine tuning the circuit is up to you. Years ago an EE persuaded me to experiment with grid resistor and stopper values to see how they affected things. Up until then I'd always used 1K carbon comp as though it was the law. He also convinced me that a good metal film was fine. Stopper values higher than needed can be lowered. It doesn't always make an audible difference but sometimes it does. When experimenting I found it easiest just to tack in a parallel resistor rather than always pulling and replacing every time.
I've been playing around with a circuit for the past couple of months that uses a telephony pentode ( like the C3g and D3a are) as the input. Until a week or so ago it had been running with G3 to cathode. Well used to the sound it was very easy to hear the difference when switching G3 to G2+plate.
No resistor there.
I used to always put in 100Ω between G2 and plate. Then on suggestion I tried Dennis Grimwood's use of a diode in series with the 100R . This also made an audible difference. These days I don't bother . Not sure why, I just don't . The G2 resistor to plate might be important on higher power tubes but I haven't had probems with the grids on low power signal tubes.
I've been playing around with a circuit for the past couple of months that uses a telephony pentode ( like the C3g and D3a are) as the input. Until a week or so ago it had been running with G3 to cathode. Well used to the sound it was very easy to hear the difference when switching G3 to G2+plate.
No resistor there.
I used to always put in 100Ω between G2 and plate. Then on suggestion I tried Dennis Grimwood's use of a diode in series with the 100R . This also made an audible difference. These days I don't bother . Not sure why, I just don't . The G2 resistor to plate might be important on higher power tubes but I haven't had probems with the grids on low power signal tubes.
There's also treble and bass adjustments, which are concentric but probably don't need to be.
The "Aural compensation" is also a pot if I remember correctly.
I'll have to dig mine out to get part numbers from the pots.
My opinion too -- with SY's "His Master's Noise" using strapped D3a
Perhaps the turntable/cartridge setup is the culprit. If I don't get the Linn set up just right it can sound harsh in the same region.
You are drawing far too much current from V1 with those huge RIAA capacitors. So the V1 stage is well into 2HD land. You should multiply those impedances by about 1000, i.e. multiply the resistances and divide the capacitances by 1000 each.
Hi Ejp. do you mean the RIAA network? Ok I will run the kabusa riaa calculator. Thank you for the input
You don’t need that. Just what I wrote. No calculator required. And that calculator doesn’t use the same network.
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No, it is an attempt by Quad to provide a highly configurable scratch filter.
Are we talking about the schematics in post #17? I have very similar phono preamplifier. In the RIAA EQ circuit you have to take the finite anode resistance into consideration. I distributed the RIAA EQ between three stages: 1-2 is the 3180 us an 318 us break points, 2-3 is the 75 us break point. The latter conveniently attenuates the noise and distortion of the first two stages. BTW, I also use the SRPP topology, but I get the signal from the cathodes as low impedance source.