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Old 15th December 2010, 12:00 PM   #71
Mihan is offline Mihan  New Zealand
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Join Date: Aug 2008
Thanks everyone for your replies.
The Tram 2 is certainly in superb company with all your amplifiers.
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Old 18th December 2010, 10:59 AM   #72
Desmo is offline Desmo  Denmark
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Join Date: Jan 2007
Location: Aarhus
I'm still waiting, waiting, waiting for my Tram 2 to arrive... The waiting is the hardest part

While waiting I have been studying the circuit diagram in the manual found on the DIY Hifi Supply website. On thing pussles me: The selection of resistors used in the circuit. Carbon composites on the grids, Kiwame elsewhere and Kiwame and Takman metal film on the output resistor network. I suppose this combination of resistors is based on listening tests, but still I wonder...

Brian: Is the selection of resistors based on what you consider the best for the preamp? Or is it the best for a certain price point?

For instance there is the (relatively) new Amtrans carbons, the various Vishay's etc that are generally regarded as some of the better sounding resistors, but also much more expensive than the ones used in the Tram 2.

Brian maybe you can elaborate a bit on how the various resistors have been used in the voicing of the Tram 2? And if you think there are alternatives, that might be even better sounding please let us know

PS.
I have bought a pair of 100K ohm Vishay naked z-foil resistors for the volume control (shunt mode). Expensive, but imho worth it...
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Old 5th January 2011, 10:06 AM   #73
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Default Tram 2 Phase

Does the Tram 2 invert phase? Can't find any mention in the manual. . .

Thanks!!

Bob
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Old 6th January 2011, 11:50 AM   #74
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by catastrofe View Post
Does the Tram 2 invert phase? Can't find any mention in the manual. . .
Yes, it does. Any true single stage tube circuit inverts polarity...

Ciao T
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Old 6th January 2011, 12:33 PM   #75
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Quote:
Originally Posted by ThorstenL View Post
Hi,



Yes, it does. Any true single stage tube circuit inverts polarity...

Ciao T
Thanks Thorsten. Need to reverse + and - at my speakers!!
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Old 25th January 2011, 11:34 AM   #76
ktuuri is offline ktuuri  Canada
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Join Date: Nov 2007
Congrats on the Blue Note Award!

Not to much out there about the Tram, but what there is" I Like"

Not long ago I heard a Hybrid amp with 300B in the gain stage and I can't get it out of my mind. What a great Amp!

I asked the designer how would it be with a 2A3 as the gain stage, and he said it would be even sweeter!

I can't use his amp with my speakers, as I run Acoustat Direct Drive Tube Amps. But I have heard what these type of tubes can do, if done right.

I think it may be time for a new preamp soon, and I would love to be able to say I built it. I think this preamp is what I have been looking for.
Gotta save up a bit more scratch, but I'm already getting excited!
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Old 26th January 2011, 08:56 PM   #77
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Join Date: May 2003
Location: UK
I promised a while back to compare 2A3 and 45 tubes in my Tram mkII. My favourite 45s are old stock and well used, they are not at all lacking at frequency extremes but there's no pretending these 45s are in the prime of their life. My 2A3s are NOS (so I'm told and I believe it), they are RCA Cunninghams.

The track that encapsulates my thoughts is Hope On Fire by Vienna Teng from the album Warm Strangers. The 45s sound atmospheric and quite vocal oriented. The 2A3s rock much more, dynamics are clearly better, other track comes properly into focus and hangs together better as a whole. Is this because my 45s are tired? Well, I tried some new 45s and liked these less but it's hard to be sure. I can only suggest others try a similar test.

Note that when switching between 2A3 and 45 you need to reset the heater voltage due to the change in current requirements. You will also find the heater supplies run hotter with the 2A3s (1.5A vs 2.5A).
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Old 24th February 2011, 08:08 PM   #78
JoshK is online now JoshK  Canada
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I am very intrigued by this preamp. I am assuming Thoersten designed it?

Anyway, I took at look at the schematic and I can't help but wonder a few things. My gut instinct was that the 6AS7 was the top element in an SRPP or mu-stage, but clearly it is the top element in a cascode CCS. It is to shield the SS CCS of high voltage?

Secondly, it looks like you are using a filament bias scheme, is that right?

I am very intrigued as I said. I like the existence of a remote too!
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Old 16th March 2011, 12:36 PM   #79
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by JoshK View Post
I am very intrigued by this preamp. I am assuming Thoersten designed it?
If you mean me - yes, I had something to do with it.

Quote:
Originally Posted by JoshK View Post
Anyway, I took at look at the schematic and I can't help but wonder a few things. My gut instinct was that the 6AS7 was the top element in an SRPP or mu-stage, but clearly it is the top element in a cascode CCS. It is to shield the SS CCS of high voltage?
The SS CCS can handle the voltage, but sounds better that way.

Quote:
Originally Posted by JoshK View Post
Secondly, it looks like you are using a filament bias scheme, is that right?
No, fixed grid bias.

It's a tradeoff.

Filament Bias needs ton's of extra voltage and places the filament regulator/supply circuit directly in your audio signal loop for both input and output. My supply designs are good, but not so good that I want to conenct them in series with the input signal of a linestage (I'd not like to do that using other peoples supplies either BTW).

Use cathode bias instead and you need a big bypass capacitor which is in series with your input AND output signal at the same time and which due to the needed value is never the best grade.

Of course, most people do not "see" the cathode cap or the filament supply in filament bias as in "the signal path", but they are there and quite audible. Worse, the output signal current traverses the cathode cap or filament supply respectively in cathode- and filament-bias. Now that is always a fair bit of current and it will cause some non-linearity. Now this non-linearity is re-amplified by the tube because on the input it appears in series with the signal.

If you use fixed bias you have an immediately visible evil, awful coupling capacitor. BUT like in the Tram II we can use a tinfoil & teflon capacitor and get as close to "no capacitor" than is possible. And in this case all the current in the coupling capacitor is the signal and the current is very small, so non-linearity is small.

Of course, each way of biasing can be made to sound good (even diode biasing and Nicad Batteries in the cathodes), but I think fixed bias makes this much easier to achieve...

Ciao T
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Old 19th March 2011, 09:02 PM   #80
JoshK is online now JoshK  Canada
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Thanks T. Sorry for misspelling your name.

Also, I'm curious if the Tram II can be ordered set up for 71a (5v filament)?

Josh
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