LS100 phono tubes

John Boy · « **on:** 5 Apr 2012, 12:22 am »

Has anyone experimented with different tubes in the LS100 phono section? I use a Mullard rectifier and Black Treasures and now want to experiment with phono tubes. Should I consider one brand for both tubes or is it OK to mix? Not sure what functions each tube does.

dminches · « **Reply #1 on:** 5 Apr 2012, 04:04 pm »

I forget what each tubes does but there is no reason to limit yourself to using the same brand for both. Use what sounds best.

mraudio · « **Reply #2 on:** 5 Apr 2012, 05:25 pm »

I have tried quite a few different tubes in the phono stage of my LS100. I usually prefer Mullards and while I did really like them, the new Psvane Grade A from Grant Fidelity sounded better in this particular situation. Grant Fidelity will sell you one of each, so you don't need to buy a pair of each, unless you want spares.

I also tried some Brimars, Amperex, RCA and Teles in various different combinations. I found the sound of the Psvane's to be just superb. YMMV.

JG2 · « **Reply #3 on:** 23 Apr 2012, 06:59 pm »

Nice to see some current production tubes sounding so good!

modwright · « **Reply #4 on:** 5 Jun 2012, 04:29 am »

Suggestion and options for the LS 100 phono!

The first tube, closest to rear of chassis, must be a 12AU7 and exact variants, of which there are a number.

The basis of design for the second tube was the 12AX7, chosen to maximize gain for MC carts. However, I have found that this often too much gain for higher MC carts > 2mV and for MM carts.

Use of a 12AU7 tube here gives you approximately 15dB less gain and solves this problem.

The 12AT7 will give you less gain that the 12AX7 and may be worth experimenting with for MC carts.

The 'Mu' of the 12AX7 = 100; 12AT7 = 70; 12AU7 = 13. (Going by memory here, so if I am off slightly, please feel free to correct me). I have tested all combinations and the RIAA curve is not disturbed and they all work well.

Hope this helps!

Thanks,

Dan W.

nnck · « **Reply #5 on:** 5 Jun 2012, 05:47 am »

Quote from: modwright on 5 Jun 2012, 04:29 am

Suggestion and options for the LS 100 phono!

The first tube, closest to rear of chassis, must be a 12AU7 and exact variants, of which there are a number.

The basis of design for the second tube was the 12AX7, chosen to maximize gain for MC carts. However, I have found that this often too much gain for higher MC carts > 2mV and for MM carts.

Use of a 12AU7 tube here gives you approximately 15dB less gain and solves this problem.

The 12AT7 will give you less gain that the 12AX7 and may be worth experimenting with for MC carts.

The 'Mu' of the 12AX7 = 100; 12AT7 = 70; 12AU7 = 13. (Going by memory here, so if I am off slightly, please feel free to correct me). I have tested all combinations and the RIAA curve is not disturbed and they all work well.

Hope this helps!

Thanks,

Dan W.

Very interesting Dan. I actually contacted you about an issue like this a while back. My Benz Ace High cart output is about 2.4 - 2.5 mV, and while I find the sound of the phono stage very good, the gain is quite high from this combo! I've been considering different lower output carts as an alternative. But for now, maybe it would be worthwhile to try a 12au7 in both positions of the optional phono stage in the LS100.

There are several accounts online about people using 5751 tubes as a lower gain replacement for 12ax7 tubes as well. Some people claim they sound better than 12ax7 tubes as well. I know when I asked you about these tubes as 12ax7 replacements, I asked if the 5751 might alter the RIAA curve, and your response was that they very well might do that.

Have you ever tried the 5751 tube to replace the 12ax7 in that position? Do you still feel it would alter the RIAA curve? But we are safe running a 12au7 in both positions for sure?

nnck · « **Reply #6 on:** 6 Jun 2012, 11:54 pm »

Let me be the first to attest to the use of 2 x 12au7 tubes in the LS100 phono stage. Previous to this, matched with the Benz Ace High MC (2.5mV) on a VPI Scout, the gain was VERY HIGH coming from the phono. While the sound was still very good overall, this gave me very little usable control over the volume in the phono stage (the sound was already very loud at about 7-8 o'clock. 9 o'clock was DAMN LOUD. And beyond that was...YIKES!). This was only really an issue when using the remote (one short click would bring it from inaudible to pretty loud), and when switching between inputs (dont forget to turn it down before you switch to phono!).

Switching to 2 x 12au7 tubes definitely decreased the gain somewhat. I still think its slightly higher than the line outs in my system, but much closer. Sound is still very good, but I'm still listening and evaluating. Overall, it seems like a pretty good alternative.

My questions for everyone here are:

(1) which tube posiitions in the phono stage would you consider more important to the sound (the original 12ax7 or the 12au7)? I have one NOS Mullard 12au7 and the stock 12au7 - I'd like to put the better tube in the more important position. I know I can easily try both, just curious if anyone has ideas to support observations.

(2) Any favorite 12au7 tubes to try out - new or NOS? If anything, I'm looking for a tight, accurate bass sound to counter a slight boominess from the bass coming from my phono setup.
Or maybe any accounts of using 5751 tubes as I mentioned in the previous post.

modwright · « **Reply #7 on:** 11 Jun 2012, 05:34 pm »

The original 12AU7 is in the first gain position in the circuit and as such, I would consider the most critical. The 12AU7 that is sub'd for the 12AX7 is the second most critical tube.

I like the RCA cleartops, but others may have recommendations.

Thanks,

Dan W.

dlach · « **Reply #8 on:** 13 Jun 2012, 03:16 am »

For the past 3 weeks I've been using 2 CIFTE 12au7's with the Ortofon Mojo MM cartridge (3mV) in a Music Hall MMF5.1 turntable. The CIFTE's ($39.95 apiece) were recommended by Jon at The TubeStore, who said they were made in the 1960's. They have a very open, smooth, and highly musical sound...or maybe it's Dan's phono stage.

Turning the volume knob up to about 10 o'clock gives all the volume you need, but it's completely clean and distortion free. I didn't know vinyl could sound this good.

Maybe I'll upgrade to a MC someday, but this combination of two superb 12au7's sounds pretty good.

BTW, can anyone recommend a reasonably priced MC cartridge..?

Denny

modwright · « **Reply #9 on:** 15 Jun 2012, 12:18 pm »

Thanks for sharing! I am glad that the tube swap from 12AX7 to 12AU7 essentially allows for MM/MC gain!

Take care,

Dan

hrcapers · « **Reply #10 on:** 29 Jun 2012, 12:37 am »

Thanks for the tip on the use of a 12AU7 in both spots! My Grado has never sounded better.

modwright · « **Reply #11 on:** 29 Jun 2012, 12:21 pm »

Excellent! Thank you.

Enjoy!

Dan

Scottdazzle · « **Reply #12 on:** 29 Jun 2012, 08:31 pm »

Quote from: dlach on 13 Jun 2012, 03:16 am

For the past 3 weeks I've been using 2 CIFTE 12au7's with the Ortofon Mojo MM cartridge (3mV) in a Music Hall MMF5.1 turntable. The CIFTE's ($39.95 apiece) were recommended by Jon at The TubeStore, who said they were made in the 1960's. They have a very open, smooth, and highly musical sound...or maybe it's Dan's phono stage.

Turning the volume knob up to about 10 o'clock gives all the volume you need, but it's completely clean and distortion free. I didn't know vinyl could sound this good.

Maybe I'll upgrade to a MC someday, but this combination of two superb 12au7's sounds pretty good.

BTW, can anyone recommend a reasonably priced MC cartridge..?

Denny

BTW, can anyone recommend a reasonably priced MC cartridge..?
Yes, the Denons under $500 perform way above what one would expect for the price.

mraudio · « **Reply #13 on:** 29 Jun 2012, 08:36 pm »

Try a Zu Audio/Denon DL-103 or a used Dynavector 17D2MKII or a 17D3 or even a DV20X2L.

dlach · « **Reply #14 on:** 30 Jun 2012, 12:08 am »

Thank you. I'll do some research and give one of them a try.

JMosch · « **Reply #15 on:** 25 May 2014, 11:27 pm »

Quote from: modwright on 11 Jun 2012, 05:34 pm

The original 12AU7 is in the first gain position in the circuit and as such, I would consider the most critical. The 12AU7 that is sub'd for the 12AX7 is the second most critical tube.

I like the RCA cleartops, but others may have recommendations.

Since I got my LS100 (about 4 months ago) I've been using a RCA cleartop 12AU7 in the first position and a Tele 12AT7 in the second stage. This turns out to be a sweet combo and perfect for my medium output cart, a Benz Wood M2 which has an output voltage of 0.8 mV. Its a beautiful thing to be able to adjust the gain like this.

To do some experimenting, I want to try this tube

Its an Amperex 7062 and it's listed as a 12AT7 equivalent.

Dan, or anyone else, will this work at the 2nd spot in the LS100 phono stage?

Sounds like an interesting tube.

John

modwright · « **Reply #16 on:** 27 May 2014, 06:32 pm »

A 12AT7 equivalent should be just fine!

The RIAA filter is a single stage and is between the stages. The plate impedance of the tubes has no effect on the RIAA and so it really just comes down to gain. Hence why I suggest substituting a 12AU7 for the 12AX7 in the first stage to reduce gain.

Thanks and please do post your findings!

Dan W.

JMosch · « **Reply #17 on:** 28 May 2014, 01:27 pm »

Thanks.
This tube should get here in a few days and I'll see how it compares to the Tele I have in there now.

John

thunderbrick · « **Reply #18 on:** 15 Jun 2015, 01:29 am »

Just took delivery of my LS-100, and two 12AU7 in the phono board did the trick for my MC Dynavector! My first LP is the Sheffield Drum Record and WOW!!!! It's a cliche, but I am hearing all KINDS of sounds I never did before. The attack, clarity and soundstage is un-freakin'-believable!

Gonna be a late night of listening!

RPM123 · « **Reply #19 on:** 19 Jul 2015, 04:34 pm »

Just purchased a LS100 last month and switched out the stock phono tubes with an Amperex PQ 7316 and a Telefunken ECC83 (12AX7). I am really enjoying these tubes! Also trying a pair of Psvane CV-181 TII and I can definitely understand the appeal of octal tubes. And of course, a month later they come out with these: Treasure Globe 6SN7-SE GF Limited Special Edition.

Very cool looking tubes!

http://psvanetube.com/wordpress/store/products/treasure-globe-6sn7-se-pair-gf-limited-special-edition/