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PostPosted: Tue Apr 08, 2014 10:19 am 
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I have a pair of RCA 6DJ8 tubes. Not sure if these are Black Gates or what. Are these hearty enough to last in the SFL-2?


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PostPosted: Tue Apr 08, 2014 5:20 pm 
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Braxus wrote:
I have a pair of RCA 6DJ8 tubes. Not sure if these are Black Gates or what. Are these hearty enough to last in the SFL-2?



Those tubes should work just fine, although, you need to be careful when buying them used as some of them were very microphonic. Having said that, the best tubes that will work well for it were the Brimar tubes that were properly matched by Parts Connexions. I’m not sure if they still sells them.


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PostPosted: Tue Apr 08, 2014 5:48 pm 
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tube54 wrote:
Braxus wrote:
I have a pair of RCA 6DJ8 tubes. Not sure if these are Black Gates or what. Are these hearty enough to last in the SFL-2?



Those tubes should work just fine, although, you need to be careful when buying them used as some of them were very microphonic. Having said that, the best tubes that will work well for it were the Brimar tubes that were properly matched by Parts Connexions. I’m not sure if they still sells them.

Last year I called Chris @ PCX inquiring about replacement tubes and he steered me towards some '80's Reflektor mil-spec 6h23p-eb's (low noise/low microphonic/long life – 6922's). They were $70/MP. So, $280 for a MP set. They are excellent.

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PostPosted: Tue Apr 08, 2014 6:16 pm 
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Pneumonic wrote:
tube54 wrote:
Braxus wrote:
I have a pair of RCA 6DJ8 tubes. Not sure if these are Black Gates or what. Are these hearty enough to last in the SFL-2?



Those tubes should work just fine, although, you need to be careful when buying them used as some of them were very microphonic. Having said that, the best tubes that will work well for it were the Brimar tubes that were properly matched by Parts Connexions. I’m not sure if they still sells them.

Last year I called Chris @ PCX inquiring about replacement tubes and he steered me towards some '80's Reflektor mil-spec 6h23p-eb's (low noise/low microphonic/long life – 6922's). They were $70/MP. So, $280 for a MP set. They are excellent.


I had a quad of those so called Russian tubes and they were terrible.
the rca 6dj8 don't mean much - check the etch codes. I had a pair of rca labeled siemens gold pins and a pair labeled made in mexico?! not the same beasts.
black gates are capacitors.
one of my favorite 6922's and not overly expensive was the Holland amperex pq a-frames


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PostPosted: Tue Apr 08, 2014 6:48 pm 
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Location: Brandon, MB, CA
Quoting OP "the Preamp I use in my main system is a Anthem AVM20 , which is only supposed to be good for stereo but not great."

At current market price for a used AVM20 ($500) I bet you will not find a better value or sounding pre-amp / HT processor for the money. If you can live with-out HDMI this unit is the steal of the century. Just my opinion.

Take Care
EZ


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PostPosted: Tue Apr 08, 2014 6:56 pm 
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I looked for the tubes I have and was mistaken. These are not 6DJ8 tubes, but 6CG7 tubes. Can these still be used? And what exactly do I have here?


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PostPosted: Tue Apr 08, 2014 7:08 pm 
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Braxus wrote:
Image

Image

I looked for the tubes I have and was mistaken. These are not 6DJ8 tubes, but 6CG7 tubes. Can these still be used? And what exactly do I have here?


i believe that's like a mini 6sn7 if i recall. swappable in some circuits but has less gain and draws much more heater current. I've no listening experience.


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PostPosted: Tue Apr 08, 2014 7:16 pm 
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Location: Calgary, AB, CA
Braxus wrote:
Image

Image

I looked for the tubes I have and was mistaken. These are not 6DJ8 tubes, but 6CG7 tubes. Can these still be used? And what exactly do I have here?


Regarding the tubes to use, stick with the 6DJ8 variant as you get better results with them. The quad matched 6DJ8 Electro Harmonix tubes from Audio Research are excellent, but it'll cost you.


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PostPosted: Tue Apr 08, 2014 7:35 pm 
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tube54 wrote:
Braxus wrote:
Image

Image

I looked for the tubes I have and was mistaken. These are not 6DJ8 tubes, but 6CG7 tubes. Can these still be used? And what exactly do I have here?


Regarding the tubes to use, stick with the 6DJ8 variant as you get better results with them. The quad matched 6DJ8 Electro Harmonix tubes from Audio Research are excellent, but it'll cost you.


Me, not a big fan of eh tubes


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PostPosted: Tue Apr 08, 2014 8:17 pm 
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BinkyTheCat wrote:
tube54 wrote:
Braxus wrote:
Image

Image

I looked for the tubes I have and was mistaken. These are not 6DJ8 tubes, but 6CG7 tubes. Can these still be used? And what exactly do I have here?


Regarding the tubes to use, stick with the 6DJ8 variant as you get better results with them. The quad matched 6DJ8 Electro Harmonix tubes from Audio Research are excellent, but it'll cost you.


Me, not a big fan of eh tubes


As far as my experience goes the Audio Research EH and Brimar tubes were excellent match for my then Sonic Frontiers SFL-2 pre-amp as it sounded a little neutral with excellent top to bottom frequency response coupled with glorious midrange. The other tubes that I've tried such as Valvo, JJ, Philips JAN, Sovtek, Amperex pinch waist, Sylvannia, Mullard, Telefunken just to name a few including the other variant of 6DJ8 tubes didn't fair well and on top of that they didn't last long either. Although, I must admit that the Amperex Bugle Boys did make the SFL-2 sound warm, which I enjoyed very much especially in the midrange area, but at the expense of wooly bass and premature roll off on the top end. Also, I've learned this lesson a long time ago that most tubes are equipment dependent, if it sound's good on Audio Research doesn't mean that it will sound the same with Sonic Frontiers or Conrad Johnson, it gets worse, especially if the said tube equipment is voiced/designed from a certain type of tubes, which will really put a damper on tube rolling experimentation.

After all, it's always been about the trade-offs no matter what tube you use, the key thing is, can you live with those trades offs...


Last edited by tube54 on Tue Apr 08, 2014 10:23 pm, edited 1 time in total.

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PostPosted: Tue Apr 08, 2014 8:49 pm 
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I looked for the tubes I have and was mistaken. These are not 6DJ8 tubes, but 6CG7 tubes. Can these still be used? And what exactly do I have here?[/quote]

Regarding the tubes to use, stick with the 6DJ8 variant as you get better results with them. The quad matched 6DJ8 Electro Harmonix tubes from Audio Research are excellent, but it'll cost you.

As far as my experience go the Audio Research EH and Brimar tubes were excellent match for my then Sonic Frontiers SFL-2 pre-amp as it sounded a little neutral with excellent top to bottom frequency response coupled with glorious midrange. The other tubes that I've tried such as Valvo, JJ, Philips JAN, Sovtek, Amperex pinch waist, Sylvannia, Mullard, Telefunken just to name a few including the other variant of 6DJ8 tubes didn't fair well and on top of that they didn't last long either. Although, I must admit that the Amperex Bugle Boys did make the SFL-2 sound warm, which I enjoyed very much especially in the midrange area, but at the expense of wooly bass and premature roll off on the top end. Also, I've learned this lesson a long time ago that most tubes are equipment dependent, if it sound's good on Audio Research doesn't mean that it will sound the same with Sonic Frontiers or Conrad Johnson, it gets worse, especially if the said tube equipment is voiced/designed from a certain type of tubes, which will really put a damper on tube rolling experimentation.

After all, it's always been about the trade-offs no matter what tube you use, the key thing is, can you live with those trades offs...[/quote][/quote]

Myself I found the bugleboys almost too warm, too dark.
One tube that did surprise me in a pleasant way were the red labelled tungsrams.
And agreed, like you said, it's equipment dependent as well.


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PostPosted: Wed Apr 09, 2014 5:09 am 
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Location: montreal, QC, CA
Bought new SFL2 from Filtronic long ago.
Connected it to a system with Klipschorns huge SS amps
A annoying hissing sound was always present at idle
Informed seller of this, said nothing could be done with that unit
one week later I get a call out of the blue from seller saying my new SFL2 had just arrived from SF and is is ready for pickup and exchage with 1st one.
Looking inside, tubes were now low noise but dont know what else SF did to second unit to make it so quiet
Unit was now dead silent at idle. looks like stock units will respond well to some tweaking.
Customer service from Filtronic sales staff has been outstanding.


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PostPosted: Thu Apr 10, 2014 7:44 am 
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Location: Campbell River, BC, CA
Still own the SFL2 , had to read this all to remember my thoughts....

Still feel the same way if looking for this type of sound (neutral , bit of tube flair in mids), this has outstanding build quality , would think several thousand dollars to buy in same quality today IMO.

Note , price would vary alot , as depends on tubes used , even which version as there are at least three.
At this age good chance been repaired / retubed so depends on what used.

To note not really bias needed on tube replacement , on single ended (RCA)output used , the adjustment comes important when using balanced outputs it makes the positive & negative outputs the same amplitude so get lower noise for one , or proper balanced outputs.

For me this is close to perfect preamp , others may want more colorfull sound to be happy , your own results are the only one that matters.

I'm still very happy with unit , however still need to build a switching unit to switch in my surround sound preamp easier.
Any preamp switcher premade or do I have to DIY ?


Brian

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PostPosted: Fri Dec 25, 2015 6:38 pm 
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Location: Chilliwack, BC, CA
Just wondering. I have listened to this preamp and my major complaint with it is that it is squashing dynamics and mellowing out the sound. Is this typical for this tube preamp or is it an issue with the tubes in this unit? I think there are JJ 6922 in this thing. I want to confirm how dynamics with this pre on other peoples systems before I take action on what to do next.

Also at full volume with no source on, I'm getting slight hum or buzz on the speakers. Could it be because I have speakers and components stacked near the pre?


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PostPosted: Sun Dec 27, 2015 1:48 pm 
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Tube gear is hard to compare as each model may have differant versions , differant tubes differant load etc etc.

This one is built very much like two stereo preamps in one , the two when use balanced outputs must be gain matched to operate correct , even tubes must be reasonable close.

That said this line of preamps neither adds or takes away as many other designs do , perhaps the sound you hear is really how it should sound , maybe not what you want to hear though.

A bad set of tubes may also hurt or change the sound , the only real way to know is try another set.

Brian

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