Hey rmlowz, the 6SN7GTA and 6SN7GTB have a higher plate dissipation.
I am not sure what that does to function or sound.
And from what I have read they added "controlled heater warm up" to the 6SN7GTB.
They have a wire that heats up before allowing the filament to light.
Sort of like a soft start.
I'm looking for one that I have so I can take a picture of that wire (if I can find it).

I found this one but my other ones just look like a normal 6SN7GT, I had one with a zig zag wire at the bottom that lit before the filament. https://i.imgur.com/J9pV3Zb.jpg[/IMG]

Thanks Straitwire I appreciate your help, I understand now
Rich

You're welcome rmlowz... Happy New Year everybody!!!:pg2:

Not getting anywhere trying to contact Dennis Had through eBay. Could one of you veterans be kind enough to PM me a working email or phone number please? REALLY want a CJ5 preamp. Or at least send me a pm so I can respond with my contact info and forward it to him. Appreciate the help. I couldn’t get past the contact info nazi’s at eBay no matter how I tried to hide it while messaging radioman731. Thanks guys.

Sorry, you cannot send/receive PM’s unless you become a Subscriber here.

Keep trying the ebay contact system. Dennis is very cautious about giving out his personal contact information. He does read this forum, so keep trying and be patient.

Went to the Toy Shop yesterday, partially because I got off work early, and partly because Dennis told me that an old prototype he had built and given to me had been updated and was ready to go. I also brought along my non-functional 01A preamp to see if the Master could work his magic. It was nice of him to take the time to humor me, but I think he needed a distraction for the grind of filling orders.

Anyway, got to the shop and the "Q5'er" was already playing. Wow. The first obvious thing was the bass. Tight, solid, fast. Sounded almost like a sand amp on the bottom end. And no straining even at high volume. Always a prototype, the circuitry in this amp is a combo of a QMB front end, with an IIPS and SS rectifier, and a 6V6'er back end. Dennis said that it goes down to 15Hz with ease and loafs at 10 WPC with the 6550s.

https://live.staticflickr.com/65535/...8c36bd6c_k.jpgUntitled by analog addict, on Flickr


So while the Q5'er was doing it's thing, Dennis started into the 01A pre. After a bunch of modifications, and tweaks, he discovered that the hash/hum/noise was coming from the filament power supply. He created a pseudo center tap for each channel, which helped, and then finally had the eureka moment when he decided to split off each 01A's power supply to a completely independent circuit. Originally, each circuit was separate, except that the base 12VAC was coning from a single filament transformer. He decided to tap into the 6.3VAC supply for one of the 01As and leave the other on the original 12V transformer. SUCCESS!!

Now the preamp was quieter than a church mouse with the noise floor down an amazing -80db and the output signal looking clean almost up to 11 on the volume control.

Dennis had previously spent some time wrestling with this piece, and had essentially thrown up his hands in frustration, since it had been particularly stubborn. Went he gave it back to me over a year ago, he had advised me to toss it into the trash bin. I had a little trepidation bringing it back, because I knew he wouldn't be happy to see it. But, after all was said and done, of course we had to listen to it. And quickly the frown turned into smiles and then outright chortling....

Nothing like the glow of thoriated filaments...(unless it's a Mercury rectifier)

https://live.staticflickr.com/65535/...9c9e82ee_k.jpgUntitled by analog addict, on Flickr

The sound. How do I describe the sound? The 01A is a directly heated triode, like a 45 or 2A3, and the signal path circuit is about as simple as it gets. All the sweat and work is in the two power supplies. But, this tube rewards the listener with an amazing full, lush, rich sound, and combined with the Q5'er, throws the biggest most amazing soundstage I think I've ever heard. Nothing like tubes almost a century old!

The 01A in it's original small pin form was created in 1922, and I brought along some globes dating from the 1920's as well. They turned out to be quite microphonic, but may well benefit from some filament burn in, since they probably haven't been fired up for well over half a century. Anyway....


https://live.staticflickr.com/65535/...1ed044c0_k.jpgUntitled by analog addict, on Flickr

We stayed way later than intended as evidenced by the dark pix, mesmerized by this wonderful combination. Playing Donald Fagan's Nightfly on vinyl produced a soundstage that I swear was 270 degrees, fully extending to either side of me. Dennis took me up on my offer to leave the preamp, loading it in the car to take home. He may not be working on it, but I knew for a fact he wasn't done with it for the evening. Stay tuned....

(Note to moderator - Sorry for the large pic size. That's what Flickr is providing. If it's a problem, let me know and I will try and fix it...)

Issues with a used purchase... All input appreciated
 

Contacted Dennis about two weeks ago about getting one of the new cj5 preamps and an amp that would power our klipsch forte iii's. I didn't hear back but figure that's because he's so busy filling orders for the cj5. Then I saw this sale and just bought an ebay listing for an lp3-a preamp prototype Deninis made in 2/25/2016 and a 6v6r that Dennis made back in 12/3/2015. It was sold under consignment (i would be the third owner) and I can return in the next 14 days no questions asked. Even though I knew the 6v6r may not have the power we need for the forte iii's (we have a large living room/kitchen space they are in). We figured the pre would be worth it and we could use the 6v6 in a smaller room and get the qmb25 monoblocks or another DH amp he might suggest.

The wife and I were super excited to get them home and listen.

It sounds... Terrible. The vocals have no resonance and are flat and present behind the percussion and with lots of sibilance. The midrange is muffled and MIA. My wife had to leave the room when it's playing because it sounds so bad. And I got quite the headache due to the fatiguing nature. I'm suspicious either the tubes are in the wrong places, are poor matches or just worn out in a way the tube tester did not reveal. (Im a complete noob when it comes to tubes, so not able to tell if these are any good). The only issues with the amp I noticed is that the socket on the lp3-a that holds the RCA 80 tube is loose. (If I turned the lp3-a upside down and patted it with my hand, it's loose enough it would probably fall out). Also, there was some occasional popping and crackle when turning the volume knob manually at first.

I am a new member here and have been reading this thread for the past week or two (on page 128 from the beginning) but have jumped ahead a bit here and there and searched the thread. We had a friends rogue cronus magnum ii hooked up to our system which sounded phenomenal, but wanted to hear /try out the dennis had experience before deciding between a DH, Rogue, or Raven amp /preamp or integrated. Not sure we want to go through the hassle of sending it to Dennis or trying to roll tubes that we would have to order and wait on. We're wondering if there are any options /suggestions you all may have before returning it.

No noticeable plate glow or anything with the tubes.

Here is the tube compliment :

Lp3-a:
RCA 80
3x Russian 6H1Pi
GE 6cG7

6v6'r:
RCA 80
2x Svetlana 6550c (switched back and forth with 2x shu Guang 6v6GT)
Russian 6H1Pi

In the spirit of trying to help you, I am approving your post. Although, this really isn’t the proper venue to correct a poor experience on eBay.