New Preamp

0 Members and 1 Guest are viewing this topic. Read 15942 times.

Tomy2Tone

Re: New Preamp
« Reply #60 on: 1 Apr 2016, 11:30 pm »
The Dude preamp that you heard at my place last summer was a 6sn7 preamp - so technically you HAVE heard one before.  Though who knows how much that was contributing to the overall sound, and how much you even remember of the overall sound with all the other variables going that day.  Also, I found out from the guy I sold it to that it was WAY out of spec.  It wasn't sounding nearly as good as his buddy's that he had heard in his system that led him to buy mine.  So, he brought it to a shop, who found some of the caps were off spec, which they were able to make some adjustments to fix.  He says it now sounds magnificent.  So, you didn't hear it in its prime either...

Yeah, I guess I should have stated I hadn't heard a 6sn7 in my setup. I do remember that day at your place but like you said there were a lot of variables. That was my first time hearing a Line Magnetic amp the Dude was hooked up to as well.


Tomy2Tone

Re: New Preamp
« Reply #61 on: 1 Apr 2016, 11:43 pm »
I haven't offered the pre for sale as the costs are pretty high. I'm very happy with the performance though, it's an amazing sounding preamp.

I'm not sure the tube buffer or any tube preamp is going to be a good idea with a Lampi DAC with DHT output tubes, but it's hard to say... the buffer has an output impedance less than the Lampi, about 500 ohms where the Lampi is going to depend on plate resistance of the tube in use, but that'll always be a good bit more than a cathode follower buffer. I'm more thinking in terms of tone, which is a good part of the appeal of the Lampi DACs having that DHT output section. You might want to consider trying the Lampi without a pre or just a passive pre like the Tortuga, my guess is it will be better overall that way. In my system I prefer the buffer over the Tortuga straight, but the tube output section does add a tiny bit of noise... moreso than a preamp with gain as the signal isn't amplified, it's actually reduced by 3-4 dB. With the Lampi DAC I can't see the additional noise and complexity of a tube buffer being worthwhile.

On the tubes, the 6922/6DJ8 are great tubes as well. The circuit design and parts quality will make a much bigger difference than 6922 vs 6SN7. The tube buffer I used in my preamp is Broski's ACF circuit, which uses a triode as a plate load and has a bipolar power supply to cancel some of the PS noise at the output. It's a very low distortion circuit that does not sound tubey at all, you get some of the 6SN7 sound from the buffer but not too much "tubiness".

Thanks Dave. I believe the dht tubes are on the L7 version and up if I remember right. I have a L4 with 12au7 and 12at7 tubes. I had tried a Tortuga pre a while back when I was using a dspeaker am 2.0 as a dac and thought it was ok but the Rogue Perseus I had at the time had more detail and better sound stage which was the opposite of another forum member here who used to have a Perseus before he got a Tortuga. But he was using a Eastern Electric dac in front of the Tortuga.

I think Morten might have another tour coming up so I may get another chance to see how it goes. I feel at this point I'm just tinkering as what I got now really sounds phenomenal. I guess it's a case of always wondering "hey, what if...."

zermatt

  • Jr. Member
  • Posts: 2
Re: New Preamp
« Reply #62 on: 9 Apr 2016, 05:20 pm »
Nice design, the wood gives it a nice look.

DaveC113

  • Facilitator
  • Posts: 3924
  • ZenWaveAudio.com
Re: New Preamp
« Reply #63 on: 14 Apr 2016, 08:28 pm »
Thanks zermatt! And welcome to AudioCircle!  :thumb:

Tommy, it's kinda hard to say what'll be ideal for your system and tastes... even though your Lampi doesn't use the big DHT ouput tubes I'm not sure following it with another tube section will be ideal. Some of it depends on what the output impedance of the Lampi is and the input impedance of your amps. If there aren't any impedance mismatches keeping it simple with a passive volume control is likely the best idea. I'd love to send a preamp to try out but for now I simply can't get into making preamps commercially. My speaker needs to be my main focus right now. I hope you can make it to RMAF again this year to hear it!  :green:


WC

Re: New Preamp
« Reply #64 on: 10 Mar 2017, 10:30 pm »
I was able to follow most of this design for the signal wiring. Which transformers did you use? I was interested in doing something similar.

Rocket

Re: New Preamp
« Reply #65 on: 11 Mar 2017, 10:00 am »
Hi Dave,

Just saw this post and what you have achieved is really amazing.  Your definitely gifted.  Hope you really enjoy the preamplifier in your system.

Cheers Rod

DaveC113

  • Facilitator
  • Posts: 3924
  • ZenWaveAudio.com
Re: New Preamp
« Reply #66 on: 12 Mar 2017, 01:12 pm »
I was able to follow most of this design for the signal wiring. Which transformers did you use? I was interested in doing something similar.

Hi WC, I used toroids that are enclosed in the wood boxes, they are also wrapped in mu-metal to reduce noise. If I remember right they are 120V in 240V out for the tube B+ and 120V in 12V out for the Tortuga LDRs.

Rod, thanks much!