Anyone know of a warm diy tube pre? Pairing with pass x350.8. Currently have ARC ref5SE and although its good I need something warmer with my ATC scm7s (at my desk) which I find too bright and fatiguing.
Looking at the SP14 tube pre kit.
Looking at the SP14 tube pre kit.
The SP14 is a wonderful preamp, I love mine. It is warm, not bright at all, and you can roll the 6SN7s to tune it.
Are the build instructions pretty good? So far I only built a Crack OTL. Did you mod yours at all ?
"you can roll the 6SN7s to tune it"
You can most effectively adjust the "warmth" by adjusting the operating point of the voltage amplifying stage, i.e. by adjusting the value of cathode resistor. The higher is 2nd harmonic distortion, the "warmer" is the sound.
You can most effectively adjust the "warmth" by adjusting the operating point of the voltage amplifying stage, i.e. by adjusting the value of cathode resistor. The higher is 2nd harmonic distortion, the "warmer" is the sound.
Yes, the build instructions are very clear. I actually bought an assembled board and made my own enclosure. I upgraded to a Mundorf M-Tube cap in the power supply and some Mundorf electrolytics for the circuit itself. I also added a Khozmo ladder attentuator for the main volume control, and some Duelund hookup wire for the connections. For the output caps I use V-Cap CUTF's but those are very expensive. Myflex caps are a good affordable option. The case Roy sells is large, but it's also very roomy so you can upgrade to your heart's content.
The basic kit is very nice-sounding but you can definitely improve it with upgrades.
That's very true. In this case, however, the circuit is based on John Broskie's Aikido, so the operating points are fixed.
Operating point can be adjusted somewhat by the cathode resistor of the input triode (say 600...1200 ohms).
https://www.tubecad.com/2004/NewLineStage.gif
https://www.tubecad.com/2004/NewLineStage.gif
The resistor (300 ohms) between volume potentiometer and the grid of 1st triode has no effect below some 50...100 kHz.
Not sure about classifying "warm"... and this certainly isn't a beginner level project (not implying anything here), but offers an insane amount of options to suit whatever taste: Aikido. Now, not "Pass" per se, but maybe the next best zen thing—haha—I've run the Aikido with my M2X mono blocks and it's fantastic. I also put a Muses volume in it... remote control and all...
The OP asked about the SP14. It's a relatively easy kit to build. The board is designed to run 6SN7s at a certain operating point and includes the power supply with tube rectifier and regulated DC filament supplies. It's extremely well thought-out and, IMO, is about as good as an octal Aikido gets. I built an octal Aikido from scratch years ago, point-to-point. Anyone who's built a scratch preamp know how hard it is to get it quiet. All that is taken care of here. It's also eminently upgrade-able. You can start with the basic design and upgrade components later as your budget allows.
Those speakers should be higher than the desktop level, since the listening axis is below the tweeter.'
No change of electronics can help that.
No change of electronics can help that.
Maybe it is a good idea not to make the same mistakes as made over and over again in ever returning threads "how to solve my self created issue" when tube preamplifiers are coupled to solid state power amplifiers. It helps tremendously not to speak of designer names, types numbers and supposedly magical properties of the WoolyBully X1 by famous Igor Zass that has the 1923 Western Electric 6SN7 with black top but first determine what exactly is required to make this mixed marriage a successful one. For a mixed marriage some technical issues should be taken into account. Not every tube pre is the same and not every solid state device is the same although the latter has more standardized features.
It makes sense to adapt to standardized line level and input impedances of the decades old standards in the solid state world. This to make interchangeability an easy affair. A tube pre with a 20 db GAIN, maximum load of 100 kOhm and 22 Vrms output voltage combined with a power on pulse of 150V won't be optimal.This is what is often chosen however as stupid as that may sound.
- Start with the question "Does my setup need this?" instead of "I want/need (insert sound effect here) sound"
- pay attention to the desired gain as many tube pre devices have tons of superfluous GAIN. Totally useless GAIN in 99% of cases.Todays sources generally have 2V rms output level. Hint: one does not need any gain in 99% of cases when driving normal power amplifiers... Action: check gain of the power amplifier and adapt desired gain of preamp to that.
- many tube devices have very mediocre drive capability and are not even able to drive a wimpy load of 20 kOhm which the sources themselves would laugh about. Action: check input impedance of the power amplifier and adapt drive capability of preamp to that.
- Make sure the tube device has a muting relay to avoid high voltage DC tube magic at power on/off going to sensitive solid state gear inputs. Action: add muting relay to device/design.
It makes sense to adapt to standardized line level and input impedances of the decades old standards in the solid state world. This to make interchangeability an easy affair. A tube pre with a 20 db GAIN, maximum load of 100 kOhm and 22 Vrms output voltage combined with a power on pulse of 150V won't be optimal.This is what is often chosen however as stupid as that may sound.
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* I read that insertion of a "warm" tube device is needed as the speakers sound "bright and fatiguing". A problem is best solved at the source.... It would be a revolution if an error of device A would be solved by insertion of device B. Compare it to the doctor, it would surprise you that you go there for pain in the right leg and to get advice to solve it by training your left hand.
A careful look to the filters and general character of too bright and fatiguing speakers and why they are like that seems worthwhile. Possibly they are just mediocre stuff or the weakest link in the specific chain.
A careful look to the filters and general character of too bright and fatiguing speakers and why they are like that seems worthwhile. Possibly they are just mediocre stuff or the weakest link in the specific chain.
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Another idea to get "warmer" sound would be to use a DSP instead of a tube pre...
Here's one that's free of charge?
https://wavearts.com/products/plugins/tube-saturator-vintage/
Here's one that's free of charge?
https://wavearts.com/products/plugins/tube-saturator-vintage/
A gun to kill a fly 😀 OP could try to use a source that has variable output level/volume control directly to the Pass heater. Just suppose the speakers turn out to be OK sounding...
The Pass device is pretty standard with 26 dB gain and 50 kOhm input impedance (it definitely does not need any extra GAIN! when sources like a DAC or CD player are used). Even a passive 25 kOhm volume control would do for testing if the sources have fixed output level.
The Pass device is pretty standard with 26 dB gain and 50 kOhm input impedance (it definitely does not need any extra GAIN! when sources like a DAC or CD player are used). Even a passive 25 kOhm volume control would do for testing if the sources have fixed output level.
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6CG7/6FQ7 are a fantastic choice for the front end of an Aikido and more affordable than most 6SN7 types, they are the 9 pin equivalent and have very low intrinsic distortion. An all 6CG7 Aikido or an Aikido with 6CG7 front end, with 6922/6DJ8 or 6N1P output would be a very low distortion, capable preamp that would be especially affordable with 6CG7/6N1P.
Still too much gain for most setups.
The whole issue with tube DIYers is the typical consumer like approach to look at the tube type first or (the very worst) to just use a random tube that is available. It is all about the tubes and they are the most important. When all you have is a hammer then everything else looks like a nail.
It really would be better to design/think in terms of required (LOW!!!) gain, 2V rms input acceptance, low enough output impedance, drive capability and other boring technical parameters that may turn out to be the decisive parameters to success. After these parameters have been determined then a tube and/or a suitable tube design can be sought. One does not choose a random but available 2 cylinder 500cc engine first and then designs a car around it yet the average tube DIYer works like that.
Here you have the reason that tube preamps are designed that have worse properties than the sources driving them. No one that can calculate would use a ECC83/12AX7 for driving a solid state power amplifier that has 26 dB of gain itself and 10 kOhm input impedance while using sources that have 2 Vrms 600 Ohm outputs.
It is also the reason that only a few devices are compatible to standardized solid state equipment. It is fully normal that devices are thrown together that can overdrive and destroy normal equipment. This means that devices must be "married" to devices that can accept that. Interchangeability is therefor a future endeavor in the tube section.
It really would be better to design/think in terms of required (LOW!!!) gain, 2V rms input acceptance, low enough output impedance, drive capability and other boring technical parameters that may turn out to be the decisive parameters to success. After these parameters have been determined then a tube and/or a suitable tube design can be sought. One does not choose a random but available 2 cylinder 500cc engine first and then designs a car around it yet the average tube DIYer works like that.
Here you have the reason that tube preamps are designed that have worse properties than the sources driving them. No one that can calculate would use a ECC83/12AX7 for driving a solid state power amplifier that has 26 dB of gain itself and 10 kOhm input impedance while using sources that have 2 Vrms 600 Ohm outputs.
It is also the reason that only a few devices are compatible to standardized solid state equipment. It is fully normal that devices are thrown together that can overdrive and destroy normal equipment. This means that devices must be "married" to devices that can accept that. Interchangeability is therefor a future endeavor in the tube section.
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