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Old 1st March 2013, 10:57 AM   #601
Desmo is offline Desmo  Denmark
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Location: Aarhus
Quote:
Originally Posted by ptashton View Post
Hugh, how is the GEC U52 sounding. Is it like the sound described by Morten?

Peter
Based on what I was told from the guy I talked to about rectifiers, these Philips 5R4GYS should sound very similar to the best 5U4G/GEC U52, maybe even with a bit more ''air'' and transparency. Price is much lower... He also said, that amongst the 5R4GY the Brimar's from the 1950's are the most hyped, and for a reason. They are harder to find, but still quite cheap compared to 5U4G/U52, so I have bought one of those and will compare with the Philips. The guy I talked to feels the Philips is as good as the Brimar... Hearing is believing...

They are really cheap compared to the nice GEC U52 you have, so maybe you can buy one, or borrow one from Hugh, and tell us how they compare
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Last edited by Desmo; 1st March 2013 at 11:08 AM.
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Old 1st March 2013, 05:04 PM   #602
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Hello Morten
it is so great that you again and again comes with good ideas,,,i must try this 5R4 tube
best Bjarne
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Old 2nd March 2013, 09:24 PM   #603
Falck is offline Falck  Sweden
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Join Date: Mar 2006
Location: Holma
Hi,

This is my first post on this forum.
I have just bought a readymade Tram2. Unfortunately I´m having some trouble with the startup and I would be grateful for some advice.

My Tram is set for 230-240 volts. I have followed the Tram manual (vers. 1.36) “Post build up Testing & Adjustment” and gone through the first 9 steps. I have the following notes:

Step 1 & 2 is OK!

Step 3 No tubes are inserted and LEDs in the front are OK!

Step 4 “Under the chassis you should see one LED on the FCUPS Module light up”
I don’t see just 1 LED light up. I can see 2 or 3 LEDs light up at different times. I don’t know if this is of any importance?

Step 5 & 6 “Use a multimeter to test the heater voltage as shown for one channel. Adjust the multiturn potentiometer (highlighted to the right in cyan) to the lowest voltage adjustable, this is normally around 2.7V”.
I measured 2.8V and I adjusted to 2.7V on both channels. I can adjust it to less than 2.7V but should I really do this?

Step 7, 8 & 9 “Switch the Tram off and back on. Test immediately after switch-on between ground (marked black to the right) and the grid of the left channel tube (marked red to the right). You should measure around -65V (+/- 10V). Repeat for second channel.” For both channels I measured -163 V between ground and grid. I then switched the Tram off. There are some things that don’t work according to the manual and I don’t know what´s wrong. I have contacted Diyhifisupply but I got no answer yet
Does any of You have any ideas?

Best Regards
Mats
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Old 3rd March 2013, 01:09 AM   #604
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Join Date: Oct 2006
Location: Karalee, Queensland
Mats, I had trouble with the voltages of my Tram2 and e-mailed Simon. This is his response. The feedback from DIYHIFI is not very good. They need a Technician on hand to respond to the technical questions. Their Technican is off site and it takes time if they do to respond. The questions on this forum are very much the same with voltage readings not matching the Tram2 manual. I asked if they could change the Manual to indicate the correct voltages, but it never happened. See attachment for lights on FCUPS Module after startup has stabilised. You get the different LEDs light up as you say.

From: Simon
Sent: Monday, July 30, 2012 5:11 PM
To: ptashton
Subject: Re: Testing ABS FCUP Tram2 Boards

Hi Peter

The LED is red, it seems to have some issue though the voltage we measured now is correct (-20v to -30v).

We are sending you the modules now. Please let us the result.

regards,
Simon
On 7/27/2012 9:14 AM, ptashton wrote:

What voltage did you get on the FCPSU for the Bias –74 volt. I was getting –118 volts. Are you getting –74 volts at the Bias point.


All the best

Peter
Attached Images
File Type: jpg IMG_5436.jpg (829.3 KB, 113 views)

Last edited by ptashton; 3rd March 2013 at 01:18 AM.
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Old 3rd March 2013, 07:10 AM   #605
Desmo is offline Desmo  Denmark
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Quote:
Originally Posted by ptashton View Post
They need a Technician on hand to respond to the technical questions. Their Technican is off site and it takes time if they do to respond.
Their Technician is Thorsten Lösch, the designer of this brilliant preamp. So maybe it helps to ask for him when contacting DIYHIFISUPPLY, or maybe contact him here at DIYAUDIO...
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Old 3rd March 2013, 07:17 AM   #606
Desmo is offline Desmo  Denmark
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Join Date: Jan 2007
Location: Aarhus
Quote:
Originally Posted by Falck View Post

Step 5 & 6 “Use a multimeter to test the heater voltage as shown for one channel. Adjust the multiturn potentiometer (highlighted to the right in cyan) to the lowest voltage adjustable, this is normally around 2.7V”.
I measured 2.8V and I adjusted to 2.7V on both channels. I can adjust it to less than 2.7V but should I really do this?

Step 7, 8 & 9 “Switch the Tram off and back on. Test immediately after switch-on between ground (marked black to the right) and the grid of the left channel tube (marked red to the right). You should measure around -65V (+/- 10V). Repeat for second channel.” For both channels I measured -163 V between ground and grid. I then switched the Tram off. There are some things that don’t work according to the manual and I don’t know what´s wrong. I have contacted Diyhifisupply but I got no answer yet
Does any of You have any ideas?

Best Regards
Mats
Hi Mats,

Welcome to the dark side of DHT preamps

Heater voltage:
Adjusting to 2,7V with no tubes is fine. This is just to get the heater voltage ''about right'' before inserting the tubes. When you have the preamp up and running, with tubes, you should let it warm up for at least half an hour and then make fine adjustment of heater voltage to 2,5V.

Grid voltage:
Check if the wiring and the resistors around the Auto Bias module is correct. When power is on, the auto bias module pulls down the grid to the negative voltage of around -65 volts (+/-) and then the voltage gradually goes up to the operating point over several seconds. This is to make a soft start on the DHT tubes. That your voltage is much lower could indicate something with the wiring or the autobias module. Try to check if the voltage stays at the -163V? Or does it gradually rise..!? Is this in both channels..?
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Old 3rd March 2013, 07:29 AM   #607
Desmo is offline Desmo  Denmark
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Quote:
Originally Posted by beardman View Post
Hello Morten
it is so great that you again and again comes with good ideas,,,i must try this 5R4 tube
best Bjarne
Hi Bjarne,

Since I did not really hear noticeable differences between the 3 different rectifier tubes I had on hand I was skeptical of Peters praise on the sonic benefit of the best rectifiers... Now I must say that he is right..! It's just to get some good ones, and the sonic improvement is noticable. Only ''problem'' is, that the best 5u4g types cost a lot of money, but shop around and you will find the Philips 5r4gys really cheap.

I have done some more listening, and the rectifier now has some more hours on it of course. The positive impression is the same... Slightly warmer, smoother, no grain what so ever, more natural and at the same time very, very transparent..! The biggest difference (I feel) is in the treble range where (for instance) cymbals sound a lot more ''live and natural''... I play the bass in a band, and bass players listen a lot to drums and cymbals because we ''lock in'' with the drummer. The sound of cymbals with the 5r4gys is more like I hear live every week when we practice in our band
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Old 3rd March 2013, 08:01 AM   #608
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Morten, the next tube to work on is the 6AS7. GEC make some very nice examples. They are designated GEC Straight or curved Brown Base 6AS7G A1834 CV2523.
Attached Images
File Type: jpg GEC6AS7GCurvedBrownBaseA1834CV2523.jpg (48.6 KB, 98 views)
File Type: jpg GEC6AS7GStraightBrownBaseA1834CV25232.jpg (40.3 KB, 97 views)
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Old 3rd March 2013, 08:13 AM   #609
Desmo is offline Desmo  Denmark
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Join Date: Jan 2007
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That is done Peter...

I use a very, very nice sounding Cunningham tube at the Mu position. It sounds and also look amazing because the glow of the heater is so strong and visible through the internal structure.

At this point I can't really think of anything else that can be improved on my Tram II... And it sounds amazing..!
Attached Images
File Type: jpg IMG_2738.jpg (112.8 KB, 96 views)
File Type: jpg IMG_4276.jpg (122.6 KB, 91 views)
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Old 3rd March 2013, 08:18 AM   #610
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Join Date: Oct 2006
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Quote:
Originally Posted by Desmo View Post
Their Technician is Thorsten Lösch, the designer of this brilliant preamp. So maybe it helps to ask for him when contacting DIYHIFISUPPLY, or maybe contact him here at DIYAUDIO...
Morten, I wish it was Thorsten Lösch. Thorsten use to be very active on this forum and solved may problems straight away. I just did not get the feeling it was Thorsten in the e-mail correspondence with Simon.

Peter
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