Pundit
Post by Gryffles on Sept 30, 2019 13:35:23 GMT 12
So my system has changed again but I'm heading in the right direction!
The changes are below:
Cartridge - Phasemation PP500
Phono - Octave Phono Module
Amps - AM 805 SE Mono amps (yes I owned these then purchased them back again)
Unfortunately one of the AM 805's lost volume yesterday. Still makes music but output is well down. Dropping off for repair today and the tech reckons it'll be minor and most likely a resistor - phew!
|
Post by Owen Y on Sept 30, 2019 18:01:43 GMT 12
It may be useful for others... how does the Octave phono compare with the many-tubed NVO phono?
|
Pundit
Post by Gryffles on Sept 30, 2019 18:22:33 GMT 12
It may be useful for others... how does the Octave phono compare with the many-tubed NVO phono? The Octave can't compete with the midrange of the NVO. Overall the Octave is a more accomplished phono, more refined, better bass, treble and sound staging and dead quite. It is also feature rich with two MC gain settings and subsonic filter.
|
Member
Post by snewt on Oct 1, 2019 8:11:43 GMT 12
Good to see you're not letting the grass grow under your feet mate 😉.I love the look of your speakers. I bet it's sounding great.
|
Pundit
Post by Gryffles on Oct 1, 2019 16:54:42 GMT 12
Good to see you're not letting the grass grow under your feet mate 😉.I love the look of your speakers. I bet it's sounding great. Some things don't seem to change aye Sounds pretty good mate.
|
Pundit
Post by Gryffles on Oct 13, 2019 14:26:41 GMT 12
Thought I'd post a pic of my PTP Lenco in a basic multi layer birch ply plinth. Parts include: SPH grease bearing and top collar DC motor and speed controller Clearlight Audio footers Ebony armboard
|
Pundit
Post by Gryffles on Oct 18, 2019 18:18:38 GMT 12
This beauty arrived yesterday: AM RT2 Preamp www.am-hiend.com/product/r-t1.htmlTwo box affair that is built like nothing I have ever seen. Very promising so far, in fact its better than promising, but I'll give it a few weeks and see how I'm feeling about it then. Initial impressions are of more texture and presence. True dual mono from PSU all the way through. Transformer volume control, transformer output. 6H30 valves driving 6922. Not noted on the website but the S/N ratio is a whopping 98dB.
|
Post by Owen Y on Oct 18, 2019 19:53:16 GMT 12
OK - a line preamp? With TVC & OPT? Nice. My tube linestage journey has come back to this in principle - TVC > 6SN7 > Tango NP-126 OPT. There's something about the way TXs transfer power in the low range & are sweet in the upper range. However, this AM has 2 tubes per ch for only 5x Gain.
|
Pundit
Post by Gryffles on Oct 18, 2019 21:23:04 GMT 12
OK - a line preamp? With TVC & OPT? Nice. My tube linestage journey has come back to this in principle - TVC > 6SN7 > Tango NP-126 OPT. There's something about the way TXs transfer power in the low range & are sweet in the upper range. However, this AM has 2 tubes per ch for only 5x Gain. Yes, line pre with TVC & OPT. I noticed you had changed your pre when I looked at your blog a while back. Completely agree with what you have found Owen. The other thing is not only how quite it is but it also seems to attenuate noise from cart and phono stage. Something really noticeable is no flattening of dynamics at lower volume either. Who can offer some explanation for this?
|
Post by colinf on Oct 19, 2019 20:16:10 GMT 12
Very nice Gryffles. An explanation...here goes...😳 A TVC is a transformer and thus the output impedance at low volume is lower than the source impedance, unlike a normal volume control. A normal pot has higher impedance than the input and reaches its highest value at half volume setting. Resistance and impedance generate noise. The lower the resistance, the lower the noise. It’s called the thermal noise of resistance, and there’s a formula for it. So with a TVC there is no loss in signal to noise ratio at low volume as resistance is very low, so dynamics are preserved. But it’s swings and roundabouts really, a volume pot has no limitation with frequency response like a transformer does. Then again, the high frequency (30 to 40kHz or so) resonance in a record being played by a stylus can be filtered to some degree by a transformer and its ultrasonically limited bandwidth. All volume pots sound different from each other as well, some flatten dynamics, some preserve it. A TVC should preserve it by design. As an aside, the infamous 50kHz time constant in some riaa networks allows the resonance through, making some poor recordings sound poorer than they are due to the increase in intermodulation distortion at audio frequencies. A bit of Sunday morning digest for you!
AMR-iFi R&D
|
Pundit
Post by Gryffles on Oct 20, 2019 12:50:51 GMT 12
colinf thanks for taking the time to explain. I get enough of that to see you have answered my Q!
|
Pundit
Post by neilsan on Oct 20, 2019 16:32:58 GMT 12
How about LDR's colinf ? Find the sound through my Clone Note just as dynamic as a Plinius M7 but not as bright/edgy.
|
Post by colinf on Oct 20, 2019 20:56:06 GMT 12
Hi Neilsan, to clarify first, a light dependent resistor (LDR) volume control is a resistor and operates like a normal volume pot, only the resistance is controlled by the amount of light falling on it instead of by the position of a wiper on a resistance track in a normal pot. That neatly sidesteps the inconsistencies of the noise made by the wiper inherent in a normal volume pot. Contact noise can manifest as slight sibilance or harshness. IME resistance-type volume controls all sound completely different from one another. Your Clone Note sounds like it’s a good ‘un. I’ve just been fiddling with volume pots relentlessly the last few weeks, they can significantly change the tone and dynamics! It goes along with what I fiddled with in the 90s the last time I tried it, including different LDRs. Even brands of the same LDR model sound different from one another. Do you know which is in the Clone Note? The big TKD volume pots are interesting in that they don’t have a conventional resistance track. They have controlled, exposed resistances for the track and metal terminations coming off it for the wiper to land on. In that way contact noise is kept under control and could approach that for an LDR. A TVC has the volume taps from the transformer running through a switch to set the volume. Providing the switch contacts are in good condition the contact noise is very low and insignificant.
AMR-iFi R&D
|
Post by Owen Y on Oct 21, 2019 9:22:53 GMT 12
My feeling also is that resistors (incl. resistive tracks as in wiper pots) add distortion at HFs (harshness) & also at LFs (good wirewound Rs, less so). Interestingly, I found that SMD (Surface Mount Device) Rs were the best sounding resistive attenuators - but it's been a few years since I've been down that rabbit hole
|
Pundit
Post by Gryffles on Oct 21, 2019 11:34:42 GMT 12
My feeling also is that resistors (incl. resistive tracks as in wiper pots) add distortion at HFs (harshness) & also at LFs (good wirewound Rs, less so). Interestingly, I found that SMD (Surface Mount Device) Rs were the best sounding resistive attenuators - but it's been a few years since I've been down that rabbit hole Do you think that harshness is actually noise Owen? ie thermal noise (shot noise) I have found the very low noise floor of the AM RT2 to make quite a difference. Even attenuating noise from components upstream. The TVC's and output TX's must be very good in the AM as the specs state freq response from 20Hz to 100KHz
|
Post by Owen Y on Oct 21, 2019 12:47:03 GMT 12
Yes likely what Colin says is audible, esp in a low signal level device like a preamp. Also, noise is affected by the design of course, eg. where the vol control is located in the circuit, can determine the noise in relation to amplified signal. In a linestage, of course, signal output is lower than incoming signal - ie attenuated
|
Post by colinf on Oct 21, 2019 19:17:28 GMT 12
I've found that surface mount resistors sound better too. The better ones have ratings of around 10 ppm or less for precision and thermal drift, to get that in a through-hole resistor you have to pay through the nose. Also surface mount resistors are far more compact and use less solder to connect to, lessening the amount of solder the sound goes through in the joint, and shortening the length of circuit board track the signal goes through. But they have lower voltage limit ratings so for valves with their high voltages through-hole resistors are more appropriate. I’ve been switching over to surface mount resistors where possible. You can get around the voltage limit by using a few surface mount resistors in series in place of one high voltage normal resistor. Some TVCs have excellent frequency response, 100kHz is good. Harshness can come from a few sources, noise being one, high order harmonic distortion (4th order and above) another. So Owen, would you say a TVC is the ultimate way to control volume? The line stage seems to be the most difficult circuit to design in a system. It has to work at low noise, low distortion and have acceptable input impedance and low output impedance. Not that the other circuits like the poweramp and phono preamp aren’t difficult to design either, just that the line stage’s characteristics seem to be more prominently audible in a system. Gryffles, you can probably now hear the nice sound of the Phasemation better.
AMR-iFi R&D
|
Post by Owen Y on Oct 21, 2019 19:26:45 GMT 12
Colin - I'd always thought that the phono stage would be the most difficult piece of amplification to design - but of course I have never designed one! ie. the low input signal level + the RIAA LF EQ, all adding up to huge gain required, whilst maintaining good dynamic range + low S/N! Then, doing it with valves. The best vol control? - I can't really say, but I am happy with the TVC. However I have not yet found time to play with a LDR attenuator - the easiest way I suppose, would be to buy one (built or kit) & 'paste' it into my preamp.
|
Post by colinf on Oct 21, 2019 21:16:26 GMT 12
Actually you’re right, designing a phono preamp is difficult! I’ve been doing it since I was about 16 and listened to so many variations in the sound over the years. But a line stage can add that insidious something that ends up detracting from the overall transparency. Line stages should improve the sound, not make it worse. I’ve experimented with loads of line stages as well as phono preamps, become frustrated, stopped it for years at a time, come back, gotten frustrated again, etc. Currently I use a pot with a jfet-input discrete opamp. The jfet has extremely high input impedance and so doesn’t draw any current from the wiper of the pot, so the pot generates next to no contact noise. In valves, I use the pot with a 6922 circuit in low gain configuration. The 6922 also has very high input impedance like jfets. The last time I tried a volume transformer (Dave Slagle) it coloured the sound a bit, but did appreciate the sense of limitless dynamics. Now to add the TVC to the 6922 circuit....Just might end up with a circuit similar to the AM!
AMR-iFi R&D
|
Pundit
Post by neilsan on Oct 22, 2019 8:33:27 GMT 12
I went from the Goldpoint SMD to the Clone Note LDR. Tried the Goldpoint again the other day and it's not as good to my ears as the LDR.More sterile sounding! So obviously I prefer the LDR distortions!
Just had a look colinf and the LDR's have NSL 7053 stamped on them.
|
Post by colinf on Oct 22, 2019 19:20:15 GMT 12
Ok, I believe they use those optocouplers in studios etc for low distortion compressors etc. Not fiddled with those yet, I’ll try them. I used to make my own optocouplers with separate leds and LDRs. The matching was quite variable so the Vactrol units in yours would be better. Audio Research used Vactrols in their earlier preamps for the warm-up mute circuit. I think Melos used them for volume control as well. Even LDRs aren’t perfect. As the signal goes through the resistance element, the small amount of audio signal power in the resistor has the effect of modulating the resistance to a degree, adding slight harmonic distortion. The SMD resistors on the Goldpoint will be very accurate, but the ear needs a smidge of distortion to make the sound believable. Just ask Nelson Pass.
AMR-iFi R&D
|
Post by Owen Y on Oct 22, 2019 20:03:51 GMT 12
Yes, I was thinking that the LDR is still a resistor in essence. but hey, I have yet to try them, so reserving judgement.
|
Pundit
Post by Gryffles on Nov 21, 2019 11:04:18 GMT 12
Although I'm really happy with the RT2 preamp I couldn't resist the house of Shindo when the chance presented itself. Just arrived so I'll give it a listen tonight.
|
Member
Post by snewt on Nov 21, 2019 18:14:07 GMT 12
Can't wait to hear the verdict!
|
Pundit
Post by Gryffles on Nov 21, 2019 19:05:18 GMT 12
Can't wait to hear the verdict! Nearly had a heart attack when there was no sound from RH channel after I set it up half an hour ago. Then I remembered the issues that can be had with the RCA sockets Shindo use. Crisis over with a wiggle of the RCA plug........phew haha
|
Post by colinf on Nov 21, 2019 19:38:46 GMT 12
|
Member
Post by snewt on Nov 22, 2019 21:41:59 GMT 12
And...? Was there Shindo magic going on?
|
Pundit
Post by Gryffles on Nov 23, 2019 14:07:56 GMT 12
And...? Was there Shindo magic going on? In short, yes. Does all the things you would expect and can read about but its magic is the way it puts it all together. I never like any changes in my system straight away and turned out the the Masseto and my new speakers arrived within a day of each other. So have just been listening and seeing what it's all about. The Zu Druids are known to need a good bit of play time to settle down and are very sensitive to the room/set-up.pretty happy so far though!
|
Pundit
Post by Gryffles on Dec 28, 2019 15:44:58 GMT 12
Quick update.
The Zu Druids now have 60 hrs on them and are starting to sound good. I was a bit concerned up to this point as they have changed a fair bit. The bass won't make your trouser legs flap but it is the most tuneful I have had in my system which is very enjoyable.
To match the Masseto I have found a used Shindo Montille 6V6 and a Shindo Mr T isolation transformer. They haven't arrived yet but will organise when I get back to Aus after my NZ holiday.
I've also added some used cables:
Auditorium 23 speaker cable and a Sablon Audio Panatela IC.
|
Pundit
Post by beeman on Jan 4, 2020 15:33:13 GMT 12
Better than the JBLs?
|