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Old 4th November 2012, 07:08 PM   #431
GeirT is offline GeirT  Norway
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An update on the above post;
The sound is even better today. Yesterday I could only get the heater voltages up to 2.4V but today managed to get exactly 2.5V on the heater voltages by fiddling (reducing) the resistor values on the Colemans heaters out. Also swapped back to my old resistors (Dale) on the pre outlet.

The dryness in the sound is gone now and it is all music :-D
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Old 5th November 2012, 07:54 AM   #432
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Thanks Geir, Pleased to hear that you like them!

The Current-Sense resistors do need some running-in time, and probably the same for the capacitor C3. These are also the parts that Morten and Bjarne have switched to more exotic parts, to good effect. It should be worth trying them on any Tram with the Filament Regulator upgrade.
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Old 5th November 2012, 10:20 AM   #433
GeirT is offline GeirT  Norway
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Thanks Rod, I'll already contacted Morten earlier to get info on the suppliers in northern Europe of these parts.

Currently my current :-) sense resistance inserted is very low as I had to put some 1 Ohm and 2,2 Ohm resistors in parallel with the resistors supplies in your kit. Is there any danger that too much current is flowing then?

The heat of the regulators are OK since I simply glued them onto the chassis.

Geir
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Old 5th November 2012, 10:35 AM   #434
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Hi Geir, it's OK provided the dc input voltage does not vary too much.

If the current range is a little too low, increasing the supply voltage slightly will be effective in increasing the range slightly. A lower value for the resistor (between C1 & C2 in the raw supply) will allow this.

This method will probably give better sound.

Setting the filament voltage within the range 2,44V .. 2,50V (measured at the socket) will be good in all cases.
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Old 5th November 2012, 11:22 AM   #435
GeirT is offline GeirT  Norway
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Thanks Rod,
then I'll rather reduce the resistor values in the power supply than the filament heater resistors.
I'll listen for any 50 Hz coming through the DC supply. Currently it's more silent than ever for this pre.

Thank you again for your support.

Geir :-)
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Old 15th November 2012, 08:43 PM   #436
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Some very interesting information regarding the sound of 45 and 2A3 NOS tubes. This is quoted from Steve Garland from the Killerdac forum in Austrlia:

45 type tubes. These are usually ST shape 1940s. The more in demand 1930 Globe types have the numbers, 145/Arcturus. UX245 /RCA. UX345/ Cunningham. 445/Deforest.

These are in my opinion the next best sounding tube ever made of American design. A Great Naturally real sounding tube. The best timbre of any tube worldwide. These tubes where made for the bread and butter radios of the day.

They have a 2.5 filament voltage and will take 275V. Output is about 2 watts

I do run them hard, 200-250v (around 2 watts).

There are 2 that stand out.

Rogers 245 long plate globe 1930s. Made in Canada. This valve is a very pretty sounding tube, clean clear and so sweet, smooth upper frequencies, can be bright if not carefull with tuning the System, does not have the timbre of the RCAs, they sound more like some 250 globes than a 45, very opposed (sound wise) to the 245 RCA version below. Great on classical.

RCA 245 Globe, This tube type is dark sounding. Can be a little rough and ragged in the upper frequencies, and is also not the cleanest 45 tube around, but it has the best timbre you will hear out of any tube, so real, so solid, real flesh on bone, Great on male vocals, guitar, not white or bright at all. . There are many 45 varieties, and you must get the right one. The black charcoal plate, circle plate globe (1930s) they have the inch long glass piece hanging from the filament support rods . The best 45 ever made along with the Rogers 45 long plate. You can see in the picture, these are the right ones, The blacker the charcoal plate the better, like the one on the left, only buy RCA 245s that have this identical construction.


Most later 1940 ST 45 shape tubes are very good, and cheap more on these and others later

and for 2A3 tubes:

2A3s. The supposed best in the 2A3s range are the monoplates. These 2a3s where made in the 1930-to 1933 as a elite audio or radio tube. Some say they stopped making them because of the cost of manufacture.

They use 2.5 filament voltage and will take 250 Volts

Be careful, many RCA 2a3 monoplates are branded RCA but where made by Sylvania. these usually have a number under the base between the pins, like J39

I find 2A3s monoplates to be overrated sound-wise, very clean clear, big soundstage, To me they sound somewhat sterile and harmonically threadbare. They sound more like a modern tube design, (Mid 1930s on) they are not as musical or involving as the 50 tubes.

Another good 2A3 monoplate is the FIVRE made in ITALY. Very nice tube, better that the genuine RCA monoplate. I have had many of these, including two that where the sort after earlier model with the side support rods (new in box).

The best ones i have ever heard are the Radiotron 2A3 mono plates, made in England, These tubes are very very good but imposable to find, i did have two mint ones a few years ago.

I like the National union 2A3 monoplates, they sound more like a 245 valve. Rich darker full, but a little ragged.

Of the 2A3 dual plates, the best is the black plate, 1940s with spring filament support.

Next is the RCA dual black plate without spring supports.

2A3s dual plates (grey or even black) generally are industrial or military, not really intended for audio use.

An exception to the rule, some people say the FIVRE dual plate is the best 2a3, (i have not heard these)
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Old 16th November 2012, 08:56 AM   #437
Desmo is offline Desmo  Denmark
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Thanks for the updates

@Geir... Could you show pictures of your implementation of the Rod Coleman regulators? It's good to share our experiences and the solutions we make (I believe)... Also: The dry sound you describe is not something I have heard with these regulators, but it appears that it's gone now so all must be good...

@ptashton... Thanks for the tube info. When I bought the Tram I was reading all I could find on all kinds of NOS 45's and 2A3's, from what I was reading the 45's should -generally speaking- be the better tubes. However, of all the tubes I have now tried in the Tram I find the 2A3's superior sounding. In the beginning I also thought that NOS tubes would sound better than new production tubes, and I have bought my share of NOS tubes for the Tram. No I have stopped rolling tubes because the best tubes I have heard for the Tram are the ones I use now... And hey, they are current production tubes, and from China Hearing is believing
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Old 27th November 2012, 01:08 PM   #438
GeirT is offline GeirT  Norway
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Yes, funny you asked because I just thought about it!
I've been on vacation at our "cottage" in Rio, so sorry about late reply.

Anyway, hopefully the photos shows below.

Geir
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Old 27th November 2012, 01:13 PM   #439
GeirT is offline GeirT  Norway
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And the sound is not "dry" anymore. the shift in tonal balance was due to a too low heater voltage at a time before I manged to raise the voltage by reducing the resistance.
As I've been surfing away at Ipanema, I still have to adjust/reduce the resistance in the power supply so to give a higher supply voltage for the Colemans regulators.

Geir
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Old 27th November 2012, 02:22 PM   #440
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Hi Geir,

It sounds like you've been having a great time!

2 things...

1) how are the transistors attached to the chassis. I don't see any bolts.

2) you should be ok to remove the capacitors across the heater socket pins.

I like the apporach of using the chassis as the heatsink, it frees up a lot of space for the power supply filter section.
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