[Toonartist]

Dave did a nice job on this. Beautiful brushing.

Beautiful finish... very classy

 

[hpsxrb]

Could someone please tell me what the manufacturer's reference corresponds to the Alps Blue Velvet RK27 20K Stereo?
Apparently the European Mouser may have this potentiometer and not run the risk of getting a fake... Is it logarithmic?
Thanks

 

[martelanc24]

Could someone please tell me what the manufacturer's reference corresponds to the Alps Blue Velvet RK27 20K Stereo?
Apparently the European Mouser may have this potentiometer and not run the risk of getting a fake... Is it logarithmic?
Thanks

By coincidence, I am just searching for the potentiometer (and other components) today. I will order this one from Farnell, as I already have some other stuff to order anyway. Farnell order code: 1191722, manufacturer part number on Farnell: STRK27102. If someone else can also confirm this is the correct one, just so I am not mistaken.

 

[L0rdGwyn]

By coincidence, I am just searching for the potentiometer (and other components) today. I will order this one from Farnell, as I already have some other stuff to order anyway. Farnell order code: 1191722, manufacturer part number on Farnell: STRK27102. If someone else can also confirm this is the correct one, just so I am not mistaken.

That looks to be correct.

 

[smodtactical]

If that is anodized, note that the anodized layer is not conductive. If the mating faces of the side panels and the top plate were not masked and are completely anodized, you will need to sand / grind away some of the anodized layer to expose the underlying metal such that the side panels make ground connections with the top and bottom panels. You will have to do the same on the underside edge of the top and bottom plates, again, a metal-to-metal connection. Also, at the two holes where ground connections are made to the chassis, you will need to sand / grind away the anodized layer on the interior. All of this can be done with a Dremel tool.

I don't think its anodized. Its just barely brushed metal.

 

[L0rdGwyn]

I don't think its anodized. Its just barely brushed metal.

If it's just brushed uncoated aluminum then that's fine, not sure what you discussed with Dave. You can always check using the continuity setting of your multimeter to see if it's conductive.

 

[Toonartist]

If it's just brushed uncoated aluminum then that's fine, not sure what you discussed with Dave. You can always check using the continuity setting of your multimeter to see if it's conductive.

I was just thinking the same thing about the MM. My new chassis had 4 separate aluminium panels and I used some stranded wire with locking washers etc to link them all to earth and did the continuity check you described! Just to be sure!

 

[AnyDave]

If it's just brushed uncoated aluminum then that's fine, not sure what you discussed with Dave. You can always check using the continuity setting of your multimeter to see if it's conductive.

Wouldn't you want some sort of anodizing on it? Straight brushed aluminum has no protection on it at all; it would be a fingerprint magnet and tarnish over time (which could look cool).

 

[L0rdGwyn]

Wouldn't you want some sort of anodizing on it? Straight brushed aluminum has no protection on it at all; it would be a fingerprint magnet and tarnish over time (which could look cool).

Dave normally offers anodization, which is done by a shop local to him. It's unusual to just do brushed aluminum, but I don't know what was discussed. Regardless, all of the chassis panels have to be grounded, and obviously the signal and safety earth connections have to be grounded to the chassis. Not doing so is a safety issue.

 

[mjstealey]

Excellent interview, thank you @L0rdGwyn for doing this!

 

[hpsxrb]

I would like to be able to use the Aegis, also as a preamplifier.

I think that if I add RCA outputs, connecting them simultaneously to the Elma switch output (where the Switchcraft is also connected), I will solve the problem (when I use it as a preamp, I turn off the headphones).

My questions are regarding this connection:
1) at which end of these connections do I connect the ground (RCA out or next to the Elma switch)?
2) where is the best place to connect the ground?

Thank you very much in advance.

 

[L0rdGwyn]

I would like to be able to use the Aegis, also as a preamplifier.

I think that if I add RCA outputs, connecting them simultaneously to the Elma switch output (where the Switchcraft is also connected), I will solve the problem (when I use it as a preamp, I turn off the headphones).

My questions are regarding this connection:
1) at which end of these connections do I connect the ground (RCA out or next to the Elma switch)?
2) where is the best place to connect the ground?

Thank you very much in advance.

Do you mean that both connections will be always on, meaning the preamp out and headphone out connected in parallel without a switch? That should be fine, obviously you would not want to keep the headphone plugged in when using it as a preamp. The RCA outs would be connected to the ELMA switch board, same connections as the TRS, red to signal, black to ground. The ground connection is made off the TRS ground pin to the PCB. If the RCA grounds are connected to the ELMA switch, they will be grounded via the same path. Full disclosure I have not tried this, on paper it should work fine, but obligatory YMMV.

 

[hpsxrb]

It occurred to me to install a small 6V 8VA transformer in the corner where the power button is located and connect it in parallel to the rectifier valve heaters, thus increasing the capacity of the heaters from 2A to 3A, in order to increase versatility in terms of rectifier tube that can be used (...274).
My question is related to the two 1.2ohms/3W resistors that lower the voltage from 6V to 5V. In addition to the increase from 3W to 5W in the rating of these resistors, for the purposes of versatility of the tubes that we can use, should we change the values of these resistors?
If so, for what value?

Thank you in advance for your responses.

 

[L0rdGwyn]

It occurred to me to install a small 6V 8VA transformer in the corner where the power button is located and connect it in parallel to the rectifier valve heaters, thus increasing the capacity of the heaters from 2A to 3A, in order to increase versatility in terms of rectifier tube that can be used (...274).
My question is related to the two 1.2ohms/3W resistors that lower the voltage from 6V to 5V. In addition to the increase from 3W to 5W in the rating of these resistors, for the purposes of versatility of the tubes that we can use, should we change the values of these resistors?
If so, for what value?

Thank you in advance for your responses.

The value of the resistors in spec'd to reach 5V from the 6V windings of the Lundahl mains transformer with the rectifiers drawing 2A of current. If you use the same value of resistor for a 3A rectifier, you are going to get an addition 50% voltage drop across them due to the additional 1A of current. For example, using the original 1.2ohm resistors, which are in parallel to reach 0.6ohms, at 2A that is 1.2V voltage drop to go from ~6.2V to 5V. With 3A of current, they will drop 1.8V and you will have 4.4V left, not 5V. Using voltage dropping resistors to adjust heater voltages with tubes are varying current draw does not work, you'd have to use one or the other, 2A or 3A rectifiers. If you want to use 3A rectifiers in addition to 2A, you need a dedicated 5V winding. You could use a 5V transformer and not use the heater winding from the Lundahl transformer at all. Even better would be to get a custom mains transformer made with a 5V 3A winding. But keep in mind, if you put a mains transformer on the interior of the chassis, you are potentially introducing noise problems into the circuit, I would not do that.

Or just use 2A rectifiers.

 

[g0ldl10n]

The value of the resistors in spec'd to reach 5V from the 6V windings of the Lundahl mains transformer with the rectifiers drawing 2A of current. If you use the same value of resistor for a 3A rectifier, you are going to get an addition 50% voltage drop across them due to the additional 1A of current. For example, using the original 1.2ohm resistors, which are in parallel to reach 0.6ohms, at 2A that is 1.2V voltage drop to go from ~6.2V to 5V. With 3A of current, they will drop 1.8V and you will have 4.4V left, not 5V. Using voltage dropping resistors to adjust heater voltages with tubes are varying current draw does not work, you'd have to use one or the other, 2A or 3A rectifiers. If you want to use 3A rectifiers in addition to 2A, you need a dedicated 5V winding. You could use a 5V transformer and not use the heater winding from the Lundahl transformer at all. Even better would be to get a custom mains transformer made with a 5V 3A winding. But keep in mind, if you put a mains transformer on the interior of the chassis, you are potentially introducing noise problems into the circuit, I would not do that.

Or just use 2A rectifiers.

I will add to this, although many on the internet are not a fan ( I do wonder if they have even tried it tbh) due to "noise" caused by them - I only needed to use this method on my separate 12.6V filament PT, and there is no noise difference between using that and my 6.3V filament PT. Anti-parallel diodes to drop heater voltages, which would remain constant despite heater requirements of the tube in use.