HiFi Haven Group Project - Building The "World's Best Tube Phono Preamp"
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I haven’t heard about any people on this forum who have built it, but I know of at least 3 people not on the forum who have built it. One of them has a CAT SL-1 preamp. He still uses the CAT linestage but now uses the D3a phono instead of the phono stage in the CAT. Of course each person built it a little differently. This is DIY after all....
I've been going thru the schematic here and have some further questions:
1) Is this a two chassis design? 1a) If so, are the connections at the arrows?
2) The Panasonic HFQ caps are discontinued. Would you source on Ebay or is there a non-discontinued cap recommended in the filament supply?
3) Since the Black Gate caps are no longer available to mere mortals, which of the Jensen caps are recommended in the power supply circuit.? There are lots of choices within the Jensen range.
TIA
1) Is this a two chassis design? 1a) If so, are the connections at the arrows?
2) The Panasonic HFQ caps are discontinued. Would you source on Ebay or is there a non-discontinued cap recommended in the filament supply?
3) Since the Black Gate caps are no longer available to mere mortals, which of the Jensen caps are recommended in the power supply circuit.? There are lots of choices within the Jensen range.
TIA
1. I used a 2-chassis design, and the connections between the two are the double arrows shown. A single chassis design would certainly work and indeed has the advantage of short wiring in the power supply. I went with the separate PS in order to get the lowest possible hum and noise. That seems to have worked because this is absolutely the quietest phono preamp I have ever used. A single chassis design might have equally low noise or it might not. I chose not to take the risk.
2. I have seen HFQ caps on EBay but I haven’t tried them. I bought mine when they were still being made. I think I would order the HFQ on EBay rather than try a different cap. I am not an expert on low-voltage caps but I do know that all of the currently manufactured caps that I have tried I didn’t like. The ones I didn’t like include Elna Silmic II, Audio Note Kaisei, and several types of Nichicons.
3. The Jensen caps I have used in several amp projects are available from PartsConnexion in Canada. The PCX part numbers are 68080 (47uf + 47uf, 500v) and 68081 (100 + 100, 500v). They also have single cap versions.
Sal, your above advise is noted. Thanks! Couple of more questions.
1) What did you use as your umbilical and how did you wire it? Did you run the B+ and heater wiring all together. I was thinking of separating the two.
2) The AN resistors are simply out of reach financially, to use in all indicated places. I was thinking of using the nude Vishay's for the RIAA and every place I could substitute for the AN as they don't make a nude Viisay in 330K for instance so I may be forced to buy a couple of $47.00 resistors. Opinions on using the 0.6watt nude Vishays where I can (except for the 12W Mills)?
3) Those TFTF in 2.0uf's are out of reach as well at $450.00 or so each. Opinions on a more reasonably price cap at that point?
Thanks in advance!
1) What did you use as your umbilical and how did you wire it? Did you run the B+ and heater wiring all together. I was thinking of separating the two.
2) The AN resistors are simply out of reach financially, to use in all indicated places. I was thinking of using the nude Vishay's for the RIAA and every place I could substitute for the AN as they don't make a nude Viisay in 330K for instance so I may be forced to buy a couple of $47.00 resistors. Opinions on using the 0.6watt nude Vishays where I can (except for the 12W Mills)?
3) Those TFTF in 2.0uf's are out of reach as well at $450.00 or so each. Opinions on a more reasonably price cap at that point?
Thanks in advance!
My power supply umbilical is just some loosely twisted Radio Shack hookup wire. One pair for the heater wires, and one pair for B+ and ground. The two pairs are separated and are hardwired (soldered) at each end. This was just a temporary test setup when I wired it up, but that was about 12 years ago. I have some V-Quad copper wire from VH Audio that I plan to try one of these days instead of the Radio Shack. I just haven’t gotten around to it.
I am not a big fan of the Vishay resistors. They are perfect for the RIAA because the eq has oddball values and you can order them with custom values matched to 1% tolerance. I also liked how they sounded in the eq network. Beyond the eq, I am suspicious about the nude Vishays. I think they would give a cold, lean tonal balance if they are used in other spots. That’s speculation though.
The output coupling cap doesn’t have to be 2uf. If I were building it today I would probably try a 0.47uf Copper Vcap instead.
Aluminum vs steel. I have had good results with both. In terms of ease of use, aluminum is much easier to drill and cut for a given thickness. A thin steel panel may have the same stiffness as a thicker aluminum panel, but if the steel is too thin it will ring and sound edgy. So it’s complicated.
My power supply chassis has inside dimensions of 8.5” x 8.5” and the audio chassis is 13.75w x 8.5d. I have wood sides so the overall dimensions are bigger.
My power supply chassis has inside dimensions of 8.5” x 8.5” and the audio chassis is 13.75w x 8.5d. I have wood sides so the overall dimensions are bigger.
I like the Landmark aluminum (1/8 inch I believe) chassis a lot but they are expensive. You can have dividers placed inside them but I am thinking that partitions made of aluminum won't do much shielding.
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Where does one find those?
The Landfall chassis appear to be well made. I would take exception though to their claim that the 1/8” aluminum is easy to work with. It’s not too bad for drilling or sawing but making holes with a punch is a major pain. I use Greenlee punches for making holes for tube sockets, big caps etc. and I still remember how difficult it was punching holes in the 1/8” top plate for my old 300B amps. I vowed Never Again!
In contrast, for some PP 6L6 amps I built earlier this year I used a pair of Eico HF-22 monoblocks. I stripped each steel chassis of all parts, cleaned them thoroughly, and then punched some new bigger holes in the same locations as some of the original tube sockets and electrolytics. I also cut some new holes for the IEC inlet, speaker binding posts, etc. Working with the thin steel was a dream compared to thicker aluminum.
In contrast, for some PP 6L6 amps I built earlier this year I used a pair of Eico HF-22 monoblocks. I stripped each steel chassis of all parts, cleaned them thoroughly, and then punched some new bigger holes in the same locations as some of the original tube sockets and electrolytics. I also cut some new holes for the IEC inlet, speaker binding posts, etc. Working with the thin steel was a dream compared to thicker aluminum.
Lubrication is the name of the game. A dash of methylated spirits makes punching or drilling aluminium a doddle.
I just reread this post and gleaned some new information. Thanks!
Still planning
First:
What exactly is the CCS on the plate of the 5687? K&K lists two boards that can have those initials.
TwoTerminal Constant Current Source
Two Terminal Cathode Current Sink
Other kits – K & K Audio
Second:
I was reading somewhere about separate power supplies and the recommendation was to include ALL the filtering in the PS chassis. Does it make sense to enclose all the circuits I've outlined in purple and break the umbilicals at the purple arrows or should I split the filtering chores as Salectric has played out in the schematic?
TIA
Dave
There are oodles of CCS variants floating around, heck you could even use a tube for the CCS! The K&K current source (not sink) will get the job done.
If you have no power supply capacitors in the preamp chassis, then the umbilical is in the signal path. If you put power supply caps close to the tubes in the preamp chassis, you will dramatically reduce the length of the signal path, and you'll remove the umbilical connectors and lots of wire from the signal path.
If you have no power supply capacitors in the preamp chassis, then the umbilical is in the signal path. If you put power supply caps close to the tubes in the preamp chassis, you will dramatically reduce the length of the signal path, and you'll remove the umbilical connectors and lots of wire from the signal path.
Use the “Large Cascode Current Source Kit” with included heat sink up to 7 watts. You need two of them, one for each channel.
I put the final stages of B+ filtering inside the audio chassis for the reasons Paul mentions. In particular I wanted the last chokes to be the first thing the B+ sees when it enters the audio chassis because they will knock out any stray RF noise the umbilical may have picked up. In my build, the BlackGate caps inside the audio chassis are positioned right next to the tubes to keep all connections as short as possible. With point-to-point wiring, I try to use the component leads for connections and avoid jumper wire connections as much as possible.
I put the final stages of B+ filtering inside the audio chassis for the reasons Paul mentions. In particular I wanted the last chokes to be the first thing the B+ sees when it enters the audio chassis because they will knock out any stray RF noise the umbilical may have picked up. In my build, the BlackGate caps inside the audio chassis are positioned right next to the tubes to keep all connections as short as possible. With point-to-point wiring, I try to use the component leads for connections and avoid jumper wire connections as much as possible.
One minor suggestion would be to provide a path to ground for any stray RF. A small cap (0.01uf) right at the input for the umbilical cord would help shunt any RF to ground as opposed to letting it float around and look for other unintended paths to ground.
---Gary
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