I managed to get hold on more information about the sockets!
I was told that the 2 outer sockets (nr 1 and nr 3) is for gain tubes, I didn't understand what the mid socket (nr 2) is for but I guess it's for a phase inverter or cathode follower? (Dont even know what that is)
I did also get a circuit diagram but unfortunately the quality is quite bad, maybe any of you guys can extract something from it anyway?
http://www.diyaudio.com/forums/attachment.php?attachmentid=620396&stc=1&d=1497013520
Edit: Use the diagram I linked to in the message, I've uploaded 2 diagrams and the second one turned out to be for a sv227 which has 4 tubes as opposed to my sv226 with 3 tubes
I was told that the 2 outer sockets (nr 1 and nr 3) is for gain tubes, I didn't understand what the mid socket (nr 2) is for but I guess it's for a phase inverter or cathode follower? (Dont even know what that is)
I did also get a circuit diagram but unfortunately the quality is quite bad, maybe any of you guys can extract something from it anyway?
http://www.diyaudio.com/forums/attachment.php?attachmentid=620396&stc=1&d=1497013520
Edit: Use the diagram I linked to in the message, I've uploaded 2 diagrams and the second one turned out to be for a sv227 which has 4 tubes as opposed to my sv226 with 3 tubes
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You seem to be confused about the word "bias", not that I blame you considered some posts. I was referring to lowering the bias of the solid state section (output amp).
You can not adjust the bias for the tubes (unless you want to rewrite the schematics).
I was talking about lowering the bias setting for output transistors, thus putting the amp closer to pure class a/b. This will in many peoples ears "tighten up the bass".
You can not adjust the bias for the tubes (unless you want to rewrite the schematics).
I was talking about lowering the bias setting for output transistors, thus putting the amp closer to pure class a/b. This will in many peoples ears "tighten up the bass".
Hi 9colai, I also just acquired a used SV-226MK2. I've been searching around for tube mods and schematic for this amp. Thank you for posting the schematics.
I have replaced my tubes with PSVane 12AU7-T Mark Ⅱ. (Note, I ordered by mistake, I really wanted the 12AX7-T Mark II). I did install them anyway and the overall sound improved from stock tubes specially in the bass region. I'm driving B&W 805N by the way.
I'm still planning to test other tubes and see what would be the best for my system. I would be interested on what you find out as well. Please continue posting
For now my list of tubes to test:
PSVane 12AX7-T Mark II
Preferred Series 7025 / 12AX7
I have replaced my tubes with PSVane 12AU7-T Mark Ⅱ. (Note, I ordered by mistake, I really wanted the 12AX7-T Mark II). I did install them anyway and the overall sound improved from stock tubes specially in the bass region. I'm driving B&W 805N by the way.
I'm still planning to test other tubes and see what would be the best for my system. I would be interested on what you find out as well. Please continue posting
For now my list of tubes to test:
PSVane 12AX7-T Mark II
Preferred Series 7025 / 12AX7
Yeppps.... now you got it
Bias = Idle current = Tomgangsstrøm (in Danish)
Great! (I did knew the Danish for it though, but thanks anyway :-D).
Hi Ferdz
Awesome! You're welcome. I'll keep you updated, and congrats with your new amplifier
.Current status is: I now know that left and right tubes are gain tubes and has the most impact on the sound/tone and the mid tube is a phase inverter. Right now, my amplifier is too sensitive on the volume control and I would also like to experiment a little with the phase inverter. I've also read that it's possible to reduce distortion in the pre-stage with lower gain tubes that has high current capabilities. so I ordered 2 different tubes with lower gain for the mid slot. the 2 tubes I ordered is:
Tung sol 12AT7W
gain is 20-30 lower than the 12AX7 tubes, I didn't really look much in to different brands as I have the impression that the phase inverter doesn't affect the sound the same way as the gain tubes. It's still good to have one with low noise and microphobics. Also the 12AT7 tubes are constructed for the phase inverter stage where it needs more current as opposed to a gain slot that needs more voltage.
Sovtek 12AX7lps
gain can be lower than my current Mullard 12ax7 according to the technical specifications. I've also read several places that this tube is a good choice for a phase converter (something about a spiral heater? But I'm not sure).
Please correct if I'm wrong
I ordered 2 tung sol 12AX7's reissues for the gain slots. I chose the tung sols based on a description of the sound characteristics that looks interesting and a lot of hype around the internet
.
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Wow thanks for the tip. This will save me some bucks since I will only need to buy 1 matched pair (gain tubes), and singles (center tube) - instead of buying 2 matched pairs or 3 matched singles.
I'm awaiting for my PSVane 12AX7T M2 and Preferred Series 7025 orders. I will probably order that Sovtek 12AX7LPs as well for my center tube.
I'm awaiting for my PSVane 12AX7T M2 and Preferred Series 7025 orders. I will probably order that Sovtek 12AX7LPs as well for my center tube.
Well, I was just reading specs and reviews/impressions. I couldn't afford expensive NOS so if I read impressions saying "I wish I bought these before spending on NOS" then I would just keep digging
I was intrigued by reviews in AudioKarma for the PSVane 12ax7 saying SQ like NOS Telefunken/Mullards tubes for a lot cheaper. But then some people don't like the PSVanes as well in these reviews. They suggested the Tianjin Full Music 12AX7, Preferred Series 7025
Cool, I'm looking forward to hear what you think
.When you say first and second stage, which sockets are you referring to? Also where do you have this information from?
I spoke with the dealer where I bought the amp and he confirmed that the mid tube is a phase inverter and the 2 outer tubes are gain tubes. He even told me that the 2 gain tubes should be the same.
I have repaired several Vincent amps and wanted to know what the tubes do.
The first stage is the center tube. One halve (triode) is used for the left and the other halve for the right channel. It's a high gain common cathode stage directly after the volume potentiometer.
The second and third stage is inside the other tube, for each channel a separate tube is used.
The second stage is also a common cathode stage with less gain, with feedback to the first stage cathode.
The third stage is a Cathode follower, which is a buffer without any gain.
It's output signal is the input for the power amp differential stage.
Every common cathode stage is a phase inverter and gain stage.
The first stage is the center tube. One halve (triode) is used for the left and the other halve for the right channel. It's a high gain common cathode stage directly after the volume potentiometer.
The second and third stage is inside the other tube, for each channel a separate tube is used.
The second stage is also a common cathode stage with less gain, with feedback to the first stage cathode.
The third stage is a Cathode follower, which is a buffer without any gain.
It's output signal is the input for the power amp differential stage.
Every common cathode stage is a phase inverter and gain stage.
Wow okay, thanks for sharing this! I wonder why I have been misinformed by the dealer
.So the mid tube is a V1 stage for left and right, the outer tubes are V2 and cathode followers for left and right respectively?
I've read that the tung sol reissues won't last long as a cathode follower, so maybe u should reconsider the tubes in the left and right sockets?
Nice job Ferdz.
To make it more complete you could add a feedback loop from second stage Anode to first stage cathode.
I'm sorry, but I cannot give the tube advises requested.
The amplifiers I have had my hands on where always working fine for the tube part. Also the factory supplied tubes where always ok, no need for replacement.
For the cathode follower, the only thing I can think about is the maximum heater to cathode voltage, which actually shouldn't be a problem with NOS tubes in this circuit. The heaters are powered from a -12V DC voltage.
To make it more complete you could add a feedback loop from second stage Anode to first stage cathode.
I'm sorry, but I cannot give the tube advises requested.
The amplifiers I have had my hands on where always working fine for the tube part. Also the factory supplied tubes where always ok, no need for replacement.
For the cathode follower, the only thing I can think about is the maximum heater to cathode voltage, which actually shouldn't be a problem with NOS tubes in this circuit. The heaters are powered from a -12V DC voltage.
Okay I have had mullards in the cathode followers for some years now without any trouble and that's new sensor tubes, so I guess it's fine.
I'm currently trying some old TAD tubes in the different slots and I did not notice any difference with the TAD high gain 7025 tubes in the outer sockets, but there is a noticeable difference in the mid socket, I like the mullard most in V1 though. But I guess that it just confirms your input djmiddelkoop as the v1 stage should be the most impactful gain stage.
I'm currently trying some old TAD tubes in the different slots and I did not notice any difference with the TAD high gain 7025 tubes in the outer sockets, but there is a noticeable difference in the mid socket, I like the mullard most in V1 though. But I guess that it just confirms your input djmiddelkoop as the v1 stage should be the most impactful gain stage.
It looks like the v1 (center) tube also affects soundstage a lot. I just installed my brand new Preferred Series 7025 (replacing the stock Chinese tube), keeping the outer PSVane 12AX7TM2 tubes (2 days old). Transparency and clarity is pretty good but I definitely lost the 3d-like soundstaging. I'm hoping it will improve in time while it continues to burn in.
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