DHT OTL Linestage - Tram 2

[GeirT]

Thanks a lot Desmo. I sent Mr. Coleman a PM yesterday as you adviced and are awaiting his instructions.
By reading the forums I now see that the DHT heater issue has a long story that goes some seven years back. Super that the outcome became so positive!

If I manage to realize this build, I'll be eager to going on trying such mods for the heater supply on my Air Tight 300B stereo amp though I've kept it "sacred" (unmodded) so far ;-)

Best regards from Geir

 

[Desmo]

With my Tram II now sounding so much better with the new DHT regulators I'm tempted to go all in a buy a pair of what (might be?) the best 2A3's out there... I'm considering the TJ / Full Music 2A3/SE carbon plate tubes... But they are expensive, so I would love to hear if anyone has experiences with these in the Tram II? Or other 2A3 amp for that matter..!?

Thanks

 

[Birka]

JJ tesla 2a3

I am using these in melody mono blocks. You can find a review on them at sixmoons audio. Clearly more powerful than the original melody's.

 

[Desmo]

I am using these in melody mono blocks. You can find a review on them at sixmoons audio. Clearly more powerful than the original melody's.

Thanks Birka, I have tried the JJ 2A3 in my Tram II, nice tubes for sure, here is my review of them (and others): http://www.diyaudio.com/forums/diy-hifi-supply/191572-tram-2-45-tubes-3.html I'm looking for even better tubes than the JJ, and better than the Treasure 2A3-Z I'm using now. I think that the best ones out there for the Tram II might be the TJ / Full Music 2A3 SE and maybe the EML 2A3's. I have tried various NOS 2A3's also, but in my experience there are too many problems with them, especially sensitivity for hum...

 

[ptashton]

Has anyone tried the Tentlabs Direct Heated Tube Supplies. A link to this site: Tube filament supply Also have any of you tried the Full Music 45 Carbon Plate tubes. About $350 AUD for a pair. Any feedback is appreciated.

 

[Desmo]

The Tentlabs heater supplies are current regulators and should be somewhere between the original supplies from the Tram II and the Rod Coleman regarding sound quality, with the Rod Coleman regulators having the best sound. I have not tried them myself, but that's what I understand from others who has tried both, as you can see above I now use the Rod Coleman reguators.

I have just ordered the TJ Full Music 2A3 SE carbon plate tubes. Both the ''c'' version and the ''se'' version are carbon plates, but with different internal construction and different sound with the ''c'' version being more of a ''vintage sound with focus on the midrange''. The ''c'' version is cheaper, so if the aim is a vintage tone, then they are the better option than the -quite expensive- ''se'' versions. I will give my update on these when I have tried the TJ Full Music 2A3 SE in the Tram. Sorry, no experience with the carbon plate 45 tubes, but with all other tubes I have tried so far I find 2A3 the best sounding in the Tram II.

 

[ptashton]

Desmo, where are you getting your TJ Full Music 2A3 SE Carbon plate tubes from. Is it a special order. I enquired with Lorenz from WiWi Tubes in Hong Kong and he said the Carbon plated 45 Tubes were a special order.

Do you have any web links to the people who tried both the Rod Coleman and the Tentlab regulators.

Also what voltage are you measuring at the 'Bias' point on your FCUPS Module. Thanks

 

[Desmo]

I have ordered the TJ 2A3 SE from Parts Connexion. They list the tubes on their website and I see no mentioning of special order (but they might be) Full Music 2A3/SE Electric Tube, Matched Pair There is a 20% discount summer sale, so I thought it was a good time to order.

DHT regulators, there is a loooong thread on the topic here on diyaudio where both Guido Tent and Rod Colman attend. Guido Tent might not agree but most people agree that the Rod Coleman regulators are superior when it comes to sound: http://www.diyaudio.com/forums/tubes-valves/38248-new-dht-heater.html Ther disadvantage of the Tentlabs regulators are, that they are IC regulators and that the strong feedback in these affects the heaters and the sound. The upside is, that they are current regulators and that seems to be a better concept, sonically, than voltage regulators for DHT heating.

Sorry, I don't think I understand the bias from the FCUPS question? What voltage are you referring to? +B? -C? Or do you mean the plate voltage or something? Please clarify...

 

[ptashton]

Desmo, At Tram 2 Manual V1.35 at page 17, on the right side of the Power Supply Module, there is a Bias -74V, ABS GND and B+ connections on the terminal block. Does the Bias -74V read -74 volts or is it much higher around -110 volts measuring from the Bias point to ABS GND.

Thanks

 

[Desmo]

Ahh, OK that is the -C voltage then. I don't remember, it's more than a year ago I build the preamp and measured the voltages, so it's long forgotten. I don't remember any voltages being off spec though.

I can check next time I open the preamp.

 

[ptashton]

Morten, have a look at this web site. Only US 540.00 for a pair. Full Music 2A3 / SE tube The company is in Hong Kong. Not a bad web site.

 

[Desmo]

Morten, have a look at this web site. Only US 540.00 for a pair. Full Music 2A3 / SE tube The company is in Hong Kong. Not a bad web site.

Thanks for the heads up! I did see those also, and the price is the same as at Parts Connexion (as long as they have the summer sale). I choose to order from Parts Connexion because I know them, and with expensive tubes like these I prefer to buy from a known source.

 

[ptashton]

I see DIYHIFI Supplies has come out with version 3 of the Filament Supply. They call it the 'DIYHFS Ultra Low Noise Filament Supply (Rev 3) 2-12V or 12-24v DC jumper selectable (Pair)' Note the 'Ultra Low Noise'. Any opinions from this forum on this new version.

Morten, I will have to look out for the Summer sale at Parts Connexion. Thanks

 

[GeirT]

I see DIYHIFI Supplies has come out with version 3 of the Filament Supply. They call it the 'DIYHFS Ultra Low Noise Filament Supply

Sure interesting, my Tram kit is in the pipeline so I'm curious to see if they have included the new heater or not. I've also received Rod Colemans heater kit already so I'll try both some day, and report.

 

[ptashton]

GeirT, where did you purchase your Rod Coleman Heater regulator kit. Do you have any info from Rod that you could share with this forum. Thanks

 

[Desmo]

Hi Geir, sorry I forgot the link..! You buy them directly from Rod Coleman, just drop him a pb here in diyaudio. There is a long thread about these regulators: http://www.diyaudio.com/forums/tubes-valves/38248-new-dht-heater-52.html


After doing a bit more listening I can honestly say, that this upgrade with the regulators is the one that sonically makes the biggest improvement. More than different tubes, coupling caps etc. And as a big bonus, the noise is also gone with these.

I quote myself on my reply to Geir on that question... Have a look at the DHT heater thread that goes all the way to 2004 and contact Rod Coleman via PM here in DiyAudio to get the regulators... They are submitted with all parts for the regulators, instruction manual, and descriptions on the parts t
you need for the raw-dc supply.

 

[ptashton]

Morten, thanks for your response. I will have a look at the New DHT Heater thread.

 

[Desmo]

Morten, thanks for your response. I will have a look at the New DHT Heater thread.

Your welcome... If you take your time to read / understand the thread, there is a lot of knowledge there. About voltage regulators, and current regulators. About regulators based on IC's with hard feedback that can effect the heaters/sound and discrete regulators that does not interfere in the same way etc etc...

 

[ptashton]

Morten, I just purchased Rod Coleman's Regulators. He sent me two PDF instruction manuals. What power supply circuit components did you use in the Tram2. It would help me greatly. Thanks Peter

 

[Desmo]

I used this one (from his older manual), but without the fuses on the DC side. If you have any doubts about what's best to do/use, then just ask him in the DHT heater thread, he is very helpful...

The most critical is the rectifier diodes and especially the first caps after the rectifiers. I used MBR1045 diodes and RIFA PEH200, 10.000uF-40V as C1. The RIFA's are big and a bit expensive, but they can handle 12A ripple, so they are exellent for this purpose. They are the two big white caps in my installation if you look at the pics. I can't remember the manufacturer of the C2 caps, but they are also 10.000uF - 40V types with a ripple capacity for around 4A or so. Check your local supplier and choose caps according to ripple handling - it's all well described in Rod Colemans instruction manual. For the rest of the components I used what I had...

I will recommend the upgrade of R1 and C3 on the regulator modules (there is lot's on this in the DHT heater thread). I used 12W Mills 0.47 ohm resistors and Amtrans 220nF caps. Both are relatively cheap and the sonic improvement in dynamics and clarity is worth it. They can fit like this...