I built my 6SN7 years ago and remember having tons of problems with hum. In the end, after elevating the ground, adding many PSU caps, etc. I added a regulated PSU for the heaters and the hum disappeared.
I have been loving my Aikido paired with my AKSA 55N.
Just after completing the Aikido, I purchased a Simple SE board from George as well as board parts. I finished my SSE a couple of. On this ago and love the amp.
Could it be jealousy, but my Aikido and SSE aren't the best of friends. Together with a 30db voltage divider in front of the attenuator in the Aikido, I go great sound. My wife says it sounds warms and full (KT88 in the SSE, 6SN7 in the Aikido). BUT... every now and then, I'd get a dip in volume that I never had with my Aikido/AKSA. Of course I doubted the SSE, but I am now wondering otherwise.
I constructed a passive pre with volume control to run the SSE alone. No dips in volume. Then cleaned the signal wiring in my Aikido, removing the attenuator and source selector and refitting the RCA's. Again, my wife finds the sound warmer.
Then I switched a NOS Mullard 12AT7 and got a weird effect: I got a fluctuating up and down of the volume, not much and not fast. Back to my vintage Sylvania 12AT7 and no "volume vibrato." So, back to the SSE alone with the Mullard and great music.
OK..... So was I hearing the sound of oscillation?
If so, was it in the Aikido, or the SSE? I suspect the latter.
If this is the case, then the Aikido is obviously overdriving the SSE.
What solutions are there:
A. Add a voltage divider at the input in my SSE and use the SSE/Aikido all the time?
B. Reserve the Aikido for use with my AKSA only.
C. Modify option B and build an Aikido board bypass switch. Use the Aikido for source selection and volume, but use a bypass switch to bypass the Aikido circuitry, leaving the Aikido switched off.
D. Reconfigure the Aikido for lower gain, maybe using a 6bx7 or 6bl7 on the input and 6sn7 on output?
I'd appreciate any advise.
Charlie
I have been loving my Aikido paired with my AKSA 55N.
Just after completing the Aikido, I purchased a Simple SE board from George as well as board parts. I finished my SSE a couple of. On this ago and love the amp.
Could it be jealousy, but my Aikido and SSE aren't the best of friends. Together with a 30db voltage divider in front of the attenuator in the Aikido, I go great sound. My wife says it sounds warms and full (KT88 in the SSE, 6SN7 in the Aikido). BUT... every now and then, I'd get a dip in volume that I never had with my Aikido/AKSA. Of course I doubted the SSE, but I am now wondering otherwise.
I constructed a passive pre with volume control to run the SSE alone. No dips in volume. Then cleaned the signal wiring in my Aikido, removing the attenuator and source selector and refitting the RCA's. Again, my wife finds the sound warmer.
Then I switched a NOS Mullard 12AT7 and got a weird effect: I got a fluctuating up and down of the volume, not much and not fast. Back to my vintage Sylvania 12AT7 and no "volume vibrato." So, back to the SSE alone with the Mullard and great music.
OK..... So was I hearing the sound of oscillation?
If so, was it in the Aikido, or the SSE? I suspect the latter.
If this is the case, then the Aikido is obviously overdriving the SSE.
What solutions are there:
A. Add a voltage divider at the input in my SSE and use the SSE/Aikido all the time?
B. Reserve the Aikido for use with my AKSA only.
C. Modify option B and build an Aikido board bypass switch. Use the Aikido for source selection and volume, but use a bypass switch to bypass the Aikido circuitry, leaving the Aikido switched off.
D. Reconfigure the Aikido for lower gain, maybe using a 6bx7 or 6bl7 on the input and 6sn7 on output?
I'd appreciate any advise.
Charlie
Lets see if I get this right - you had a 30dB attenuator in front of the Aikido gain stage to drive a KT88 amplifier (What is the SSE?) but replaced this with a passive volume control (assume max gain of 1) and had no problems with level changes but still had sufficient signal levels to drive the amp to okay volume, yes?
But you changed back to the Aikido for the sound quality but got the same problem of varying volume levels - what did you do about a volume control?
Then you changed a valve and got a worse problem - how are you fitting 9 pin 12AT7 valves into the 8 pin 6SN7 sockets? The 6BX7 are okay for the o/p buffer but not so good for the gain stage - they're also happier running at over 20mA - a 5965 (ECC81, etc) has a bit lower gain and a better candidate, IMO.
A question - why are you using a gain stage if you don't need one? The minimum gain in the 'standard' 6SN7 configuration is about 10 (about 18dB) and if you're using a 30 dB attenuator in front of this to get a reasonable volume out of the amplifier, then you don't really need to use the front gain stage of the Aikido at all, but just use the buffer o/p stage to get the 'colour' of the valves in the signal - I understand that there is a way to get lower gain from the gain stage of the Aikido (about 10dB) but have not seen it done in practice - maybe an email to Glassware will get you the information
There's a simple buffer project at Glassware Audio to follow but either way, it's all pretty straight forward as the o/p stage also has blocking capacitors, etc and only needs a simple wiring change or that switch.
This variation in volume could also be a ground problem - the Aikido is a pretty stable animal and it might be fighting off a ground loop problem, unusual as this may sound.
Can you reduce the gain on the amplifier?
Please excuse my mutterings if I've got all this wrong, and all the best ....
But you changed back to the Aikido for the sound quality but got the same problem of varying volume levels - what did you do about a volume control?
Then you changed a valve and got a worse problem - how are you fitting 9 pin 12AT7 valves into the 8 pin 6SN7 sockets? The 6BX7 are okay for the o/p buffer but not so good for the gain stage - they're also happier running at over 20mA - a 5965 (ECC81, etc) has a bit lower gain and a better candidate, IMO.
A question - why are you using a gain stage if you don't need one? The minimum gain in the 'standard' 6SN7 configuration is about 10 (about 18dB) and if you're using a 30 dB attenuator in front of this to get a reasonable volume out of the amplifier, then you don't really need to use the front gain stage of the Aikido at all, but just use the buffer o/p stage to get the 'colour' of the valves in the signal - I understand that there is a way to get lower gain from the gain stage of the Aikido (about 10dB) but have not seen it done in practice - maybe an email to Glassware will get you the information
There's a simple buffer project at Glassware Audio to follow but either way, it's all pretty straight forward as the o/p stage also has blocking capacitors, etc and only needs a simple wiring change or that switch.
This variation in volume could also be a ground problem - the Aikido is a pretty stable animal and it might be fighting off a ground loop problem, unusual as this may sound.
Can you reduce the gain on the amplifier?
Please excuse my mutterings if I've got all this wrong, and all the best ....
Option E. Reconfigure the Aikido as a cathode follower only (see the docs for that board on the tubecad site)
The aikido follower lets a lot of subsonics through, I found it enough to be apparent on the bias sense resistors on the power amp when the line voltage jumped. A series regulated B+ supply on the preamp solved that. I wonder if you are having a similar problem?
The aikido follower lets a lot of subsonics through, I found it enough to be apparent on the bias sense resistors on the power amp when the line voltage jumped. A series regulated B+ supply on the preamp solved that. I wonder if you are having a similar problem?
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Maybe you need a grid stopper for each 12AT7 grid? A resistor value around 68K should do it. Mount this resistor with minimal lead length right at the grid terminal of the tube socket. What grid stoppers do is to create a low pass filter (using the stray and Miller capacitance of the tube) to kill any supersonic oscillations that can cause your trouble.
James,
The SSE is Tubelab's SimpleSE amplifier. It uses a single 12AT7 driving two KT88's. It does not require a preamp, although it sounds fuller with my 6SN7 in front.
But, with the Aikido/SSE combo, I get the occasional volume drop, with a NOS Mullard in the SSE, I get the "motor boarding" effect.
I hope this clears any misunderstandings from my original post. As for volume, I do not need the Aikido in front of the SSE, but the fullness isn't quite there the same way. In comparison, with the KT88's and Aikido, the sound is more like my SSE alone, but with EL34's.
I'll look at the other options as posted by forum members, including my option E and the cathode follower from Broskie's website.
Thanks,
Charlie
The Aikido produces a lot of 2nd harmonics which is responsible for the 'fulness' effect.
Probably the SSE goes into clipping mode with the additional sub-sonics distortions of the Aikido. This clipping can produce a saturating effect and reduce the gain until capacitors and power supply recover.
If you want to keep the SSE you need to find which stage clips and possibly beef up that stage dealing with high level signals or beef up the power supply ( power transfo , rectifier)
It is great to learn that the SSE is a low distortion amplifier which lets you hear the effect of the Aikido. I would contact the designer of the SSE to see if he knows which part could reduce the recovery time or a simple upgrade.
Probably the SSE goes into clipping mode with the additional sub-sonics distortions of the Aikido. This clipping can produce a saturating effect and reduce the gain until capacitors and power supply recover.
If you want to keep the SSE you need to find which stage clips and possibly beef up that stage dealing with high level signals or beef up the power supply ( power transfo , rectifier)
It is great to learn that the SSE is a low distortion amplifier which lets you hear the effect of the Aikido. I would contact the designer of the SSE to see if he knows which part could reduce the recovery time or a simple upgrade.
Charlie,
Something weird is a happening in your Aikido. I have built the same animal. As a matter of fact I have also built a Aikido using the 9 pin 6Sn7 equivilents. No hum problems and using AC on the heaters. They are however critical in their need for good grounds so that ground loops do not occur. I have used mine with every kind of tube amplifier I can get my hands on as well as SS power amplifiers. No hum problems and no oscillations. I have even used my Aikido with a pair of Allen model 75's with the 1st stage still intact. Using the first stage in a model 75 results in a lot of gain and yet I was able to dial back the Aikido and get some sweet sound.
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Original Burnedfingers,
I remember your assistance in the building of my Aikido (and Sy's). Thank-you. BeforeI move on, I need to go back and simplify my Aikido. It has been working great with my solid-state AKSA. I need to remove the diode-involved elevated ground, and other, probably superfluous bits, maybe even simplify my overly complex psu.
Then go back and ponder how to incorporate it (if at all) with my SimpleSE, maybe I'll re-chassis it into some quilted Maple and convert it to an ACF for use as a buffer with my Adcom in one of the family rooms.
Charlie
I remember your assistance in the building of my Aikido (and Sy's). Thank-you. BeforeI move on, I need to go back and simplify my Aikido. It has been working great with my solid-state AKSA. I need to remove the diode-involved elevated ground, and other, probably superfluous bits, maybe even simplify my overly complex psu.
Then go back and ponder how to incorporate it (if at all) with my SimpleSE, maybe I'll re-chassis it into some quilted Maple and convert it to an ACF for use as a buffer with my Adcom in one of the family rooms.
Charlie
.
I am the designer of the SSE. Although the SSE uses simple RC coupling I have not seen overload / recovery issues in NORMAL operation, nor when I connect up a guitar preamp and drive it 20 dB into clipping. It could be possible to create an overload and recovery issue if there was a strong subsonic signal at the input, although the volume drop would be accompanied with some significant distortion which has not been mentioned.
I run an SSE in bridged push - pull through a single OPT as a guitar amp. It makes over 50 watts and sees near constant clipping, all with the standard power supply using the budget Allied 6K7VG power transformer. The power supply and everything else in the SSE has no problems running up to 15 watts per channel in SE mode, UNLESS there is significant subsonic energy saturating the OPT. Saturation causes the output tube current to skyrocket, and a bigger power supply could actually be a bad thing. Reducing the size of the coupling cap could reduce the influence of subsonic signal input, but might affect the bass response if reduced too much.
I built a phono stage with a single IC chip per channel that had frequency response down to the few Hz range. A warped record, or worse a slightly non concentric record would deliver enough sub sonic (33/60 Hz) energy to the SSE to cause a periodic distortion caused by the OPT saturating. No volume drop was noted but the B+ voltage would vary with the record warp! I modified the phono stage to rolloff anything below 30 Hz.
Is there any distortion when the volume drops? What are you using for a signal source. If you have multiple sources, does the volume drop happen on all sources, or only one? Does volume level matter? If the drop happens at low volume AUDIO overload is ruled out, but subsonic signal could still be an issue.
Did you put a volume control in the SSE when you built it? If so is it still there? Does reducing the volume control at the SSE affect the issue (your option A)? If there is a subsonic issue between the output of the Aikido and the input of the SSE, an attenuator or volume control could "break the loop."
How long does this volume drop last, and are they totally random, or is there an event that triggers it? Sometimes the event can seem totally unrelated like the AC or furnace turning on, but causing a change in line voltage.
I would leave a voltmeter connected to the SSE power supply, and another to the Aikido and see if there is a voltage change when the volume drop occurs.
Motorboating was mentioned......How are you powering the Aikido? Are you stealing power from the SSE? If so you probably need some decoupling between the SSE and the Aikido. This could show up as a varying B+ voltage in either the amp or Aikido.
George,
Thanks for your detailed reply. I'll try to answer questions. It's really quite interesting and rather "detective-like"
I have not heard any distortion with the volume drops.
My signal sources are: CD (Rega Apollo), Vinyl (Rega P2 into a Cornet 2 phono). The volume drop seemed to occur on either.
The volume setting didn't seem to matter, although I tend not to listen at very loud volume levels.
No, I didn't put a volume control there. However, now that I have built a passive pre-amp using my 100K Goldpoint stepped attenuator, I could put that between the Aikido and SSE just to see if that would improve things.
What about a 30 db resistor l-pad at the input to the SSE?
The volume drops last less than a second. Interestingly, it seemed like other items (such as the sink disposal) caused a drop with change in line voltage - dropping from say 114 to 112, then back up to 114. Sometimes the lights would flicker. However, this is not always the case. Also the drops seemed more likely with the KT120's over the KT88's.
I could buy some cheap RS voltmeters and see what happens.
I run both SSE and Aikido on the same circuit through a PureAV surge protector and conditioner. They're on different outputs on the PureAV: the Aikido, CD, Phono are on non-delay, with the SSE being delayed by the conditioner.
Funny thing though: on the SSE alone, my wife likes the warmth of the EL34's running with B+ of 425 and cathode resistor of 910. The KT88's run with 560 ohm were a little sterile for her, although I liked the sound as it sounded clean with solid bass (not lacking in the EL34 either).
In fact, the Aikido with 6SN7's and the SSE with KT88's had the warmth of the EL34 SSE alone, but with a little more punch.
The EL34's are more relaxed, warm and with quiet, simply music the sound is quite engaging. Right now, I am listening to a CD by Breabach and their simply arrangements of scottish music is very enjoyable. I cannot imagine the complexities of Alan Parsons will be quite as good with the EL34's.
Charlie
Thanks for your detailed reply. I'll try to answer questions. It's really quite interesting and rather "detective-like"
I have not heard any distortion with the volume drops.
My signal sources are: CD (Rega Apollo), Vinyl (Rega P2 into a Cornet 2 phono). The volume drop seemed to occur on either.
The volume setting didn't seem to matter, although I tend not to listen at very loud volume levels.
No, I didn't put a volume control there. However, now that I have built a passive pre-amp using my 100K Goldpoint stepped attenuator, I could put that between the Aikido and SSE just to see if that would improve things.
What about a 30 db resistor l-pad at the input to the SSE?
The volume drops last less than a second. Interestingly, it seemed like other items (such as the sink disposal) caused a drop with change in line voltage - dropping from say 114 to 112, then back up to 114. Sometimes the lights would flicker. However, this is not always the case. Also the drops seemed more likely with the KT120's over the KT88's.
I could buy some cheap RS voltmeters and see what happens.
I run both SSE and Aikido on the same circuit through a PureAV surge protector and conditioner. They're on different outputs on the PureAV: the Aikido, CD, Phono are on non-delay, with the SSE being delayed by the conditioner.
Funny thing though: on the SSE alone, my wife likes the warmth of the EL34's running with B+ of 425 and cathode resistor of 910. The KT88's run with 560 ohm were a little sterile for her, although I liked the sound as it sounded clean with solid bass (not lacking in the EL34 either).
In fact, the Aikido with 6SN7's and the SSE with KT88's had the warmth of the EL34 SSE alone, but with a little more punch.
The EL34's are more relaxed, warm and with quiet, simply music the sound is quite engaging. Right now, I am listening to a CD by Breabach and their simply arrangements of scottish music is very enjoyable. I cannot imagine the complexities of Alan Parsons will be quite as good with the EL34's.
Charlie
I wonder if I could install a 30db l-pad at the input to the SimpleSE. Besides attenuating the strong signal from the Aikido preamp, could there be any negative consequences?
While I am quite liking, running the SSE without the Aikido preamp, I do have to crank up the 100k attenuator to get decent volume. Maybe this is not a big deal and once I get my 10p Pensils finished, it'll not be an issue at all. Pat of me is wondering if a I should install a bypass switch in my Aikido so that I can switch it between passive pre and active pre.
There's no rush I suppose.
Charlie
While I am quite liking, running the SSE without the Aikido preamp, I do have to crank up the 100k attenuator to get decent volume. Maybe this is not a big deal and once I get my 10p Pensils finished, it'll not be an issue at all. Pat of me is wondering if a I should install a bypass switch in my Aikido so that I can switch it between passive pre and active pre.
There's no rush I suppose.
Charlie
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