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Post by Deleted on Apr 30, 2018 6:35:44 GMT
Hi Doc, did fitting the tube buffer add a valve like quality to the sound? If by that you mean the often described “Pipe and slippers” warmth that people acquaint with valves, then no. But then properly designed vales circuits don’t do that anyway. 😀. As I said Nelson Pass did the same thing with solid state, it just allows the passive attenuators to present a constant load to the power amp. When I first was playing around with the idea, I used a Musical Fidelity X10 D, which is a unity gain buffer, but got rid of that, precisely because it is meant to give a “Valve sound”, which was not what I was after.
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Post by Deleted on Apr 30, 2018 7:09:16 GMT
To clarify my understanding; the tube buffer you use does improve sound, by ensuring a constant load is presented to the power amp, rather than giving a bit of tube flavour?
I thought that was it’s intention, I might not have worded my question properly. I was just curious if the introduction of tubes would always add a certain something.
Do you know if all passive pres are non linear across the volume range? Is this the same with tvcs as well, or is it a case of no absolutes again?
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Post by Deleted on Apr 30, 2018 7:43:33 GMT
I have yet to hear some of these so called quality passive sound anything like it's price point.
Take a look at them under a scope @ 4Khz, they ring like a bell which is why some companies use car audio damping material inside the case to help combat this.
Sorry yet to be convinced at all
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Post by Deleted on Apr 30, 2018 10:55:35 GMT
To clarify my understanding; the tube buffer you use does improve sound, by ensuring a constant load is presented to the power amp, rather than giving a bit of tube flavour? I thought that was it’s intention, I might not have worded my question properly. I was just curious if the introduction of tubes would always add a certain something. Do you know if all passive pres are non linear across the volume range? Is this the same with tvcs as well, or is it a case of no absolutes again? Yes the improvement is due to the constant load preventing the parameters changing as the attenuation changes. Also in my opinion, it's best to avoid devices that are simply additive, ie they attenuate my increasing the reistance. The ideal method is to shunt the unwanted signal to earth a stepped attenuator thus wired will have the signal passing through just one resistor, not multiples. TVCs should have a constant impedance, which will be that of the secondary winding, however that's not always true, especially with some that have variable boost levels. Not yet tried a buffered TVC, might get the soldering iron out later this year.😁
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Post by Deleted on Apr 30, 2018 11:09:41 GMT
To clarify my understanding; the tube buffer you use does improve sound, by ensuring a constant load is presented to the power amp, rather than giving a bit of tube flavour? I thought that was it’s intention, I might not have worded my question properly. I was just curious if the introduction of tubes would always add a certain something. Do you know if all passive pres are non linear across the volume range? Is this the same with tvcs as well, or is it a case of no absolutes again? Yes the improvement is due to the constant load preventing the parameters changing as the attenuation changes. Also in my opinion, it's best to avoid devices that are simply additive, ie they attenuate my increasing the reistance. The ideal method is to shunt the unwanted signal to earth a stepped attenuator thus wired will have the signal passing through just one resistor, not multiples. TVCs should have a constant impedance, which will be that of the secondary winding, however that's not always true, especially with some that have variable boost levels. Not yet tried a buffered TVC, might get the soldering iron out later this year.😁 Thanks for the detailed explanation. In all seriousness, if you do try your experiment, I'm interested to know how it plays out.
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Post by Deleted on Apr 30, 2018 11:20:10 GMT
I have yet to hear some of these so called quality passive sound anything like it's price point. Take a look at them under a scope @ 4Khz, they ring like a bell which is why some companies use car audio damping material inside the case to help combat this. Sorry yet to be convinced at all Do you mean this about all passives?
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Post by dsjr on Apr 30, 2018 13:18:43 GMT
I'd imagine a transformer coupled passive preamp could ring, and possibly add a little distortion at the frequency extremes, but a pot in a box is just a variable resistor network using a film track instead of pre-determined resistors in 'steps.'
Andr'e, even Quad themselves recommended the old QED passive back in the day and I remember being peeved as I lost a potential 34 preamp sale when the 303 power amp owning client phoned Quad's service dept. and was told to buy the QED instead... The 33 preamp really does change the signal fed it quite audibly, especially in the low frequencies if mine is anything to go by and the 'Dada' updates minimise this, but it's still there, the bass roll-off deliberately set high to protect the 303's waywardness (massive potential response rise) in the sub 20Hz low bass into 57 speakers according to a HFN appreciation of the 303...
Passives can be got for not much money at all and the ones I'm associated with carry a 30 day return for refund policy if they're not suitable. The channel tracking of the pot is fine from 10% up from minimum and for most purposes, a little adjustment of the control can restore balance down this low. I have the stepped attenuators Tisbury use and of course, balance is excellent at every volume step. Not sure I find the reproduction of reverb and atmosphere effects is quite as good as the film pot though, but that's me.
By the way, some sources need a 50k load minimum (old Quad tuners and cheaper Rega CD payers apparently), so a typical 10k log pot in a box may not be entirely suitable?
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Post by Deleted on Apr 30, 2018 14:23:54 GMT
Never liked Dada. Always championed Net Audio.. It was the fully rebuilt Net '33' i liked not the standard. You need 10K for the Q303
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Post by dsjr on Apr 30, 2018 14:42:40 GMT
The net Audio 33 isn't a 33 at all really imo as the output buffer is totally different and I believe the phono stage too? My dada 33 is updated original with lower noise transistors able to handle the gain differences here and there and I went one further and changed the output cap on the output cards to take the bass roll-off down a touch (25hz instead of 35hz start). I love it dearly, but it *does* sound slightly different to the straight through mode (fed from a variable output CD player).
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Post by dsjr on Apr 30, 2018 14:45:37 GMT
Hi Doc, did fitting the tube buffer add a valve like quality to the sound? If by that you mean the often described “Pipe and slippers” warmth that people acquaint with valves, then no. But then properly designed vales circuits don’t do that anyway. 😀. As I said Nelson Pass did the same thing with solid state, it just allows the passive attenuators to present a constant load to the power amp. When I first was playing around with the idea, I used a Musical Fidelity X10 D, which is a unity gain buffer, but got rid of that, precisely because it is meant to give a “Valve sound”, which was not what I was after. I agree about the stock X-10D, but I did a Rock Grotto update on mine including mil-spec valves as recommended and it sounds a lot less 'trad valve-like' now, the bass under far better control! Some of the signal caps have been upgraded again since mine was done and apparently it's claimed to be even more benign ;
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Post by Deleted on Apr 30, 2018 14:52:51 GMT
The net Audio 33 isn't a 33 at all really imo as the output buffer is totally different and I believe the phono stage too? My dada 33 is updated original with lower noise transistors able to handle the gain differences here and there and I went one further and changed the output cap on the output cards to take the bass roll-off down a touch (25hz instead of 35hz start). I love it dearly, but it *does* sound slightly different to the straight through mode (fed from a variable output CD player). What u need to do to a 33 is rebuild it old for new but work on the Power supply mod. Not interested in modding for a CD player, i always use a straight Aux for CD. Try using them for the design they were in the day cos as you say they are no longer the original unit .
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Post by Deleted on Apr 30, 2018 15:01:53 GMT
Do you mean this about all passives? Hi Martin Thus far I have have listened to around 30 or so units ranging form £200-£20K+ (I know lol) over the years both TX coupled and the pot type like the Audio Synthesis. Some were flatter than a witches tit after Halloween others were quite dynamic, some had this lovely ball of sound in between the speakers, one or two managed to disappear very well some were constructed very nicely others were frankly a joke, with multiple long runs of single stranded wire (that had been soldered by a worse for ware sloth on mogadon) just ready to act as aerial! Again the quality of TX is important along with the construction, those that use a custom quality resistor ladder pot I feel offer better control and more refinement, however implementation is key here. Dsjr is correct output impedance on the passives can be problematic as some power amps can be fussy on their impedance's. 100K seems to be the standard output impedance. At the end of the day being damn quirky; if you like then run with it, for me personally, being not very amicable so not a chance. A quality active pre brings so much to the party imho.
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Post by Deleted on Apr 30, 2018 15:07:11 GMT
Be careful dont go upsetting them thats paid more than £100 for a passive
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Post by dsjr on Apr 30, 2018 16:49:52 GMT
The passives I know best - cough - are now 10k log pots - not sure about the nominal shunt-stepped ones but the two I made up were 47k..
Andr'e, my updated 33 is used on the tape input for the CD source. I know it means attenuating the input only for the output boards to ramp it up again, but that's the compromise I set as the output cards don't need adjusting down and therefore the phono boards increased to counter. The power supply is now the recommended 16V which the replacement BC155's? seem able to handle fine.
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Post by Deleted on Apr 30, 2018 18:21:33 GMT
I think i put a 15V regulated PSU in mine..
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Post by bigman80 on May 1, 2018 14:43:12 GMT
Yep, Slagle pre here. I won't be passing it on. Built a passive with Slagle AVC’s which was excellent, best pre I’ve used in my system. Have passed it on, though now have a Tribute AVC which I’ve yet to wire up to try. Hoping for great things from it though, Tribute make some of the best audio transformers on the planet.
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Post by yomanze on May 1, 2018 14:52:19 GMT
There are two major areas where passives suffer, which are macro-dynamics, and bass slam. In comparison to actives, passives can be better at resolving micro-dynamics and fine detail. However, for me, a great active preamp in the chain just sounds more like music to me. Technically it shouldn't make a difference in my setup, because my sources have a very low output impedance, but it does...
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Post by dsjr on May 1, 2018 15:14:57 GMT
There are two major areas where passives suffer, which are macro-dynamics, and bass slam. In comparison to actives, passives can be better at resolving micro-dynamics and fine detail. With respect sir, it depends on the power amp and to a lesser extent the sources used in my experience and you can't be absolutist about it I'm afraid. Some power amps do not care much for passive pots only, but others are happy to be used this way and others encourage this method. Thing is, you can get one cheaply enough on sale-or-return to try for yourself and pro stores have single input versions even cheaper, albeit with 3.5 stereo jacks as connectors...
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Post by yomanze on May 1, 2018 15:19:16 GMT
There are two major areas where passives suffer, which are macro-dynamics, and bass slam. In comparison to actives, passives can be better at resolving micro-dynamics and fine detail. With respect sir, it depends on the power amp and to a lesser extent the sources used in my experience and you can't be absolutist about it I'm afraid. Some power amps do not care much for passive pots only, but others are happy to be used this way and others encourage this method. Thing is, you can get one cheaply enough on sale-or-return to try for yourself and pro stores have single input versions even cheaper, albeit with 3.5 stereo jacks as connectors...
Nice to see you Dave. And yes it does depend, one example that I can think of is whether the amp has input buffer circuitry or not, or whether this is 'moved' into the active pre side i.e. a passive pre with an input buffer on the amp side would be, for all intents and purposes, the same thing as an active pre (at unity gain) driving an amp with no input buffer.
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