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Post by firebottle on Feb 25, 2020 15:05:24 GMT
This design isn't new, just new to me. It has a long thread on DIY Audio which I have only recently seen. The interesting thing is that without prior knowledge of this circuit I designed the KIN/Vivant phono stage and it is very similar, based on the same design approach using the mu follower circuit. The difference is that the Vivant is a hybrid implementation whereas the Salas circuit uses valves exclusively. The hybrid has a couple of advantages, not requiring a second floating heater supply and improved power supply rejection ratio, PSRR. However the all valve circuit has piqued my interest so I am building one. I have ordered a smart case for the amplifier section:  I don't know if I will mount the valves to be protruding out of the top or internal as yet. Originally I thought to include the power supply in the same box but had the good fortune to pick up an unfinished power supply project that was intended for an EAR 834 clone. I have had to add an extra transformer for the heater circuits, the right hand one in the picture.  As built the psu was trying to power a heater regulator from a 6.3V heater winding, as some of you will know that is not enough to accommodate the voltage overhead of a regulator circuit. I think the transformer primary was set to 225V in an effort to boost this voltage a bit but the problem is you then end up with excessive HT voltage as well. The extra transformer has two 8.5V windings as two independent heater circuits/regulators are required. Even with this secondary voltage I had to replace the standard rectifier diodes that were fitted with Schottky diodes that have a lower forward voltage. Originals:  Replacements:  Adding the extra heater regulator in part 2. |
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Bigman80
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Post by Bigman80 on Feb 25, 2020 15:10:11 GMT
How far along with this are you Al?
The cases look very modern! I like them
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Post by firebottle on Feb 25, 2020 15:15:42 GMT
A second heater regulator was squeezed into a corner of the pcb mounted on a heatsink taken from a faulty switch mode psu.  This also necessitated a schottky diode bridge rectifier, this was mounted on the heater transformer:  The finished power supply now looks like this, it is mounted in a non-descript grey steel enclosure.  There will be an umbilical cable connecting to the phono enclosure. I have the valves, valve bases and RCA sockets but will need to order capacitors at least. More to come when extra progress is made. |
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Post by hammer on Feb 25, 2020 16:29:04 GMT
Looks like a nice project Alan
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Post by sq225917 on Feb 25, 2020 17:38:04 GMT
Great minds,I mess about with diode choice to trim voltages in the Paradise psu. Cheaper than stocking a range of 30w power resistors.
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Post by firebottle on Mar 9, 2020 17:41:50 GMT
Progress so far, I have all the bits now and the case has arrived. Planning the internal layout this afternoon:  This is one of the difficult bits when building a point to point construction, it is very annoying if you end up without enough space in certain areas to get the components in easily. The multipin connector hanging on the top of the left hand side in the picture is proving 'special'  . I have fitted a fixed umbilical cord to the power supply as the connector that was on the power supply was a male, meaning when it wasn't mated there was a possibility of contacting the pins with 300V dc on them. I didn't fancy that much. So the only suitable connectors I had in my connectors box were both cable mounting so I am having to convert the above connector to a chassis mount. More progress tomorrow ........... |
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Bigman80
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Post by Bigman80 on Mar 9, 2020 18:12:38 GMT
That looks like it will be fairly compact when done Al, but having the PSU external will be well worthwhile.
Nice work.
Will it be done for Thursday? lol
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Post by firebottle on Mar 9, 2020 18:50:04 GMT
May be, not sure. I have a birthday to celebrate in between.
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Bigman80
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Post by Bigman80 on Mar 9, 2020 18:56:50 GMT
May be, not sure. I have a birthday to celebrate in between. Haha, I'd forgot. Tomorrow? |
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Post by firebottle on Mar 9, 2020 18:58:10 GMT
Wednesday.
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Post by Deleted on Mar 9, 2020 19:39:29 GMT
Any notion if this works out of providing it as a DIY kit Alan? I only ask as there's a shortage of decent DIY phono kits in the UK (The USA is awash with the things...) and the two that I can see available are just silly over-priced.
I built the inexpensive Hagerman Bugle 2 some years back, and good as it is for what it is, was looking for one a bit more challenging to have a crack at. My option is to bypass the power smoothing circuit of the Bugle2 (for the SMPS) and build a separate transformer power supply, individually choked per channel to feed to PCB from and put all into a nice case.
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Post by electronumpty on Mar 9, 2020 20:25:38 GMT
Any notion if this works out of providing it as a DIY kit Alan? I only ask as there's a shortage of decent DIY phono kits in the UK (The USA is awash with the things...) and the two that I can see available are just silly over-priced. I built the inexpensive Hagerman Bugle 2 some years back, and good as it is for what it is, was looking for one a bit more challenging to have a crack at. My option is to bypass the power smoothing circuit of the Bugle2 (for the SMPS) and build a separate transformer power supply, individually choked per channel to feed to PCB from and put all into a nice case. Sound like you need a Bigbottle! |
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Post by Bigman80 on Mar 9, 2020 20:55:35 GMT
@reffc electronumptyPaul, The DIY market has the best DIY Valve Phonostage available, imo. It's the Bigbottle MM/MC. There is a group buy currently in full swing on DIY, or if you are interested, drop me a message. Andy, I dont know if the Bigbottle would be challenging enough for Paul, but i think the SQ would be a surprise, as it is to most people who hear it. |
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Post by electronumpty on Mar 9, 2020 21:09:41 GMT
@reffc electronumptyPaul, The DIY market has the best DIY Valve Phonostage available, imo. It's the Bigbottle MM/MC. There is a group buy currently in full swing on DIY, or if you are interested, drop me a message. Andy, I dont know if the Bigbottle would be challenging enough for Paul, but i think the SQ would be a surprise, as it is to most people who hear it. Yes maybe not, it depends how much you want to diy I guess, athough I went a bit further with the case etc. Thought I'd mention it though as Alan developed the circuit, sound s great too! Also as Alan has mentioned there are some similarities to the circuit in the Salas even though they were developed in isolation. Don't ask me what they are though! 🤣 |
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Post by Deleted on Mar 9, 2020 21:50:31 GMT
Interesting stuff.
The things that matter to me are:
1. Accurate RIAA, preferably passive if it's a valve stage;
2. High quality choke regulated power supply;
3. High S/N (low noise) as the rest of my system delivers this so anything up front much under 95 probably wouldn't get a look in.
4. Adjustable capacitance loading options for any MM stage but that's not a deal killer for me.
In relation to the third point, I've been spoilt with a TRON Seven Reference spec linestage preamp which offers possibly the highest S/N performance of just about any valve pre in existence. It has been tweaked by Graham and contains some very special bits under the hood and the power amp's no slouch either.
In terms of difficulty, I've no problems building up power supplies, sorting casework etc. I built the Hagerman, including sorting and testing the components, in about 3 hours. It wasn't much of a challenge tbh for anyone handy with a soldering iron.
I don't pretend to be an amplifier designer as my expertise is in loudspeakers, passive crossover design, structural analysis, acoustics and I've been known to knock the odd bit of joinery up. I'm open to suggestions. Just upgrading the Hagerman would be enough as long as I can do that under the cost of a commercial offering.
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Post by Bigman80 on Mar 9, 2020 21:59:33 GMT
I think youd like this, paul.
You can build one for £350 exc valves and we seem to do what you look for, apart maybe the choke.
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Post by electronumpty on Mar 9, 2020 22:20:18 GMT
Mine cost about 420 excluding the case as this was made from donated aluminium and ply I had knocking about so free. But of that 120 was on mundorf caps and 70 on the toroidy tx . So it can be done cheaper than this by some way if needed.
Valves not included in the costs above but you can spend as much/little as you like on these.
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Post by Deleted on Mar 9, 2020 22:26:31 GMT
Interest piqued.
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Post by Bigman80 on Mar 9, 2020 22:36:59 GMT
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Post by Bigman80 on Mar 9, 2020 22:37:43 GMT
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Post by electronumpty on Mar 9, 2020 22:37:53 GMT
I have a build thread in the diy section here if you haven't seen it already. Mine is a mk 1 board and the mk3 looks to be more refined in layout and also supports mm. Oliver can tell you more about it.
Ah he beat me to it! 🙂
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Post by Bigman80 on Mar 9, 2020 22:38:21 GMT
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Post by Bigman80 on Mar 9, 2020 22:40:19 GMT
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Post by firebottle on Mar 10, 2020 8:46:09 GMT
No problem, thread drift is good.
@ Paul, if you weren't aware the Bigbottle phono stage is a collaboration between Bigman80 and myself Firebottle.
It has been designed specifically for very accurate RIAA with split passive eq. It includes all the power supply on the same pcb, apart from the transformer, and uses a capacitor multiplier instead of a choke.
It is MM/MC capable with a clever switching arrangement between the two via a simple on/off switch and on board relays.
It is a very quiet stage helped by using a cascode mu stage at the input. I'm sure you would like it.
Edit. Also included on the pcb are connection points for Loading sockets to accommodate capacitive loading for MM, or alternative resistive loading for MC.
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Post by Deleted on Mar 10, 2020 9:04:06 GMT
"Sounds" like it is well thought out.
If I did not have my KIN....
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Post by firebottle on Mar 10, 2020 10:38:14 GMT
OK back on track. I have managed to convert the umbilical power connector to chassis mount and am now set to start wiring.  |
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Post by Deleted on Mar 10, 2020 11:29:17 GMT
Thanks Alan
I wasn't really aware of its origins as I have not been a forum-goer where it may have been mentioned for a long time. Sounds like a decent amount of time and effort by you both has gone into this and I think it'd be good to try one hence I'm in discussion with Oli about the pcb. Sorry for thread drift and will follow this with interest.
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Post by firebottle on Mar 10, 2020 12:37:09 GMT
Wiring started, power wiring and twin 'earth' bars fitted to keep the circuitry dual mono.  |
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Post by Bigman80 on Mar 10, 2020 13:34:54 GMT
Wiring started, power wiring and twin 'earth' bars fitted to keep the circuitry dual mono. Very tidy. |
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Post by sq225917 on Mar 10, 2020 15:52:04 GMT
Bang tidy
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. I have fitted a fixed umbilical cord to the power supply as the connector that was on the power supply was a male, meaning when it wasn't mated there was a possibility of contacting the pins with 300V dc on them. I didn't fancy that much.
