Attention Sonic Frontiers owners.....

Hi, I have recently been corrected of a mistake regarding the Sonic Frontiers Line series pre/amps and Power Series of amps. I was always informed that the most important tube spots for these products was the rear most LV1, V1 rear positions. After trying a little experiment with my tube amp I became curious about a tube swap that I performed. I emailed SFI and I was then told of the circuit topology. It is broken down like this for the Line 2 and Power 2:
Line 2:
V1 and LV1 – Input buffer
V2 and LV2 – Gain stage
V3 and LV3 – Cathode follower
Power 2:
V1 and LV1 – input buffer
V2 and LV2 – voltage amplifier
V3 and LV3 – driver
V4 and LV4 – cathode follower.
I’ve since started using the gain stage slots for my better tubes and have been pleasantly surprised. I recommend that you try the same if you own one of these products. I'm not sure about the Line1+3 or the other power series of amps but I recommend you email SFI about them for more details.
You emailed Sonic Frontiers..... Well that was a mistake. I suggest you email Chris Johnson at Parts ConneXion. Chris is the former owner of Sonic Frontiers and designer. The back row will yield the biggest difference in sound, for the Line One and Line Two preamps.

Hi Jim, I am well aware of Chris Johnson and TPC as I have owned SFI gear for 6+ years. I will Email him about the actual job of each of the various pairs. But if you are right and the rear slots are the most important then you are saying the Buffer stage is more important then the gain stage. I hear differences in the slot movements but im trying to maximize the importance of a single pair of tubes in each piece as I don't wish to spend that kind of money on NOS. I find the sound right now using the gain slots for my better tubes to be much more dimensional sounding. I am using EH 6922's in the 2 pairs and in the gain slots a pair of Siemens 7308/E188cc's gold pins in the other slots. I have a host of other tubes that ill be playing with in due time but right now I am enjoying this setup.
Greg, I have only owned the Sonic Frontiers Line one preamp for about nine months. I have more money invested in NOS tubes than I gave for the preamp. I just can't seem to shake the bug.

I can not speak for the Sonic Frontiers Power amp. I am using an Audio Research VT 50.
Email Chris Johnson. Who better to ask than the owner/designer.
the product is still supported through Anthem locally here in the Greater Toronto Area- no need to go to PCX for that. Here is the e-mail address: Also- here is the link-

good luck.

p.s. I own an all-out modded Line 3 pre, and NOT by PCX...
sutts - who modded your line 3?
a E. Eng friend who designs and builds his own amps and preamps...
Gsselling, did you email Chris Johnson?

Gsselling, I spent most of yesterday experimenting changing tubes around in my Line 1. Lately I have been running a pair of early 60s NOS Siemens CCa tubes in the back row LV1 & V1. In the center row LV2 & V2 a pair of Amperex early 60s PQ USA 7308 tubes.
I moved the PQs to the back row and the CCa tubes to the center row. I new I would here a difference and indeed I did.
I listened for about an hour or so. Then I pulled the CCa tubes from the center and installed a pair of Telefunken E188CC tubes. I had interchanged the Telefunken E188CC and the Siemens CCa tubes in the back row enough times I new what to expect in the difference in sonics between the two tubes. I turned the Line one on and let it warm up for about a half hour. I then sat down for a listen......I listened for about an hour. Playing the same CDs I had listened to with the CCa tubes. The differences were still there but on a larger scale. Confused, yes...I pulled the E188CC tubes and reinstalled the CCA tubes. Turned the preamp back on, waited about a half hour and sat back down for a listen. The difference in sound between the two pairs of tubes is definitely more noticeable in the center row, LV2 & V2 than in the back row LV1 & V1.

Last night I sent an email myself to Chris Johnson.

Mr. Chris Johnson;
I know you have probably answered this question in the past several times. I
am of the understanding that the order of importance of tube placement in
the Sonic Frontiers Line 1 and Line 2 is as follows,
LV1 & V1..... most important will yield the biggest change in sound.
LV2 & V2.....Second most important.
LV3 & V3.....least important.

I have the Line one and have been installing the best of breed NOS tubes in
the back row, LV1 & V1. Early 60s Siemens CCa, Amperex White label PQ 7308
USA made, Telefunken E188CC, and Telefunken E88CC tubes.

Someone just posted a thread on Audiogon saying that "Sonic Frontiers" says
the center row LV2 & V2 will yield the biggest change in sound followed by
LV1 & V1.

Chris will you settle this once and for all. Who best can answer this
question but you the former owner and designer, of the Sonic frontiers Line
1, 2, and 3. Will you please give the reasons why.

Also would you mind if I posted your answer in quotes on Audiogon. I will
only post that part of your answer that you approve.

Thank you very much for your time.

Left my Full name
Audiogon user name jea48
My email address

A simple answer, unsigned:
>"LINE 1, Line-2

Most important.....gain tubes V2, LV2"<
A reply email address,
Information []

Hi Jim, wow, you've really dug into this with all of your might!!! This past week I took out my Siemens E188cc's from my amp and have been running both pairs in the LV1+2 and V 1+2 slots of the pre amp. I have found that they are much better paired like this while running all EH 6922's in the Power 2. I have ordered some more pairs of them to give them a shot in the amp to see what kind of results that would bring. Yesterday I finally got around to doing some room treatments in the way of Auralex absorption panels and some of their bass traps and the improvements that has brought is astounding. I will post more on all of this at a later time and I'll put up some pictures on system here.
I have the SF power 2 amp and SF says that the 2 front 6922 run hot. Had anyone experienced the capacitors under the 2 front tubes got hot and the cap. the labels pealed off?
Dear Gsselling,
I have the Line 2SE+ Preamplifier.
As you saw the front line (L3 and LV3) is the less important and really don´t affect the sound. So the problem are line 1 and 2. Both affect the sound, so I bought quads Siemens E88CC and quads Amperex 6922PQ White label made in USA. (for the line 3 I use a pair of Reflektor 6H23NEB)
I tried the four Siemens and then the four Amperex. For me, I prefer the sound of the Amperex but the Siemens have less noise and microphonics.
So, finnally I combined the Amperex with the Siemens. I put the Siemens in the line 2 and the Amperex in the line 1. So I have an identical tube set to replace them in the future.
For me this combination is the best. Althought I have a very little more texture in voices with the 4 Amperex I have less noise and more analitical with the Siemens in the Line 2.
I hope this help you.