So, after a few days burn in of the new PSU and the Tantalum resistor, some news: The AN Tantalum has a very beautiful sound signature. I would not call it the most neutral or the transparent reistor in this position, but it adds an unbelievable amount of musicality.
The wirewounds are still more "vibrant". The space is deeper, more air around the instruments...but when you look at your feet: The feet tipping with the music comes with the AN Tantalum. It has a very beautiful tonal richness. It makes as well everything sound "bigger". An effect you need to get used to...
So, I would use the AN Tant for Jazz and the Neoohm for classical music...or other comaprison: the An is the LP12 and the Neoohm a heavy maas turntable. To get me right: The Neoohm is not thin at all. The AN is simply more colorful.
The wirewounds are still more "vibrant". The space is deeper, more air around the instruments...but when you look at your feet: The feet tipping with the music comes with the AN Tantalum. It has a very beautiful tonal richness. It makes as well everything sound "bigger". An effect you need to get used to...
So, I would use the AN Tant for Jazz and the Neoohm for classical music...or other comaprison: the An is the LP12 and the Neoohm a heavy maas turntable. To get me right: The Neoohm is not thin at all. The AN is simply more colorful.
OK, some progress report:
I implemented two switches to switch on the fly between 12V and 6 V heater-voltage per tube stage.
So, the tube-rolling was started. this is to be seen as my very first impression, need much more investigation, but I am looking forward if you have similar or different results:
B+ ist 250V. The first stage is with CCS at 6mA. So, I did not change the bias to optimize for each tube, I understand this imperfection of this process, but I rather collect initial impressions than get lost in trying to remember how something was sounding hours or days later. But I would be very interested in your experience how does a 12BH7 changes its sonics quality when not used at 6 mA, but at 12 mA (or 6cg7 etc) etc.
The second stage was originally the ECC99, which sound rather technical and thin. The TAD 12BH7 changed that dramatically to transparent and harmonical at the same time. So, it stayed currently as the cathode follower with 250 Ohm cathode resistor, as well a Neoohm wirewound.
So, given these conditions, istarted to do some tube rolling in the first stage:
- Psvane 12au7 Reference: Warm, good tone, but a little lack of transparency and dynamic.
- JJ 802S: Very fast, very wide soundstage, a little too cool in my view, a little bit technical, but very dynamic, there is a lot of inner structure of how tone is generated. Still one of my reference-tubes here.
- TAD 12BH7: WOW !!! Nearly as transparent as the JJ802S, but warmer and more powerful, adult soundstage. VERY SERIOUS, maybe even better than the JJ802S
- Raytheon 6CG7: Brutal. Even bigger sound and more powerfull than the 12BH7. Like a 12BH7 on steroids. Everything is warm, but less deep space, much bigger instruments than before, in my view unnatural big. You think that your poweramp have now double the power. But you loose the right size of instruments, ervything come more into the front and is less deep.
- Russian 6H23-EV ( my favourite 6922): As well like a 12au7 on steroids...but is it not as neutral as the above. It adds a signature which goes into the direction of a lot off pressure, a bit more noisy, flatter in space, more liek a small brother of the 6CG7, but with a more realistic size of the instruments.
So, I will investigate this further, please let me know what your findings are and if you have similar impressions or hints what to try as well.
ON the resistor front: My initial impressions hold true. Wirewound rules over Tantalum. Next will be the Rhopoint Wirewound against Neohm as I/V. I iwll as well exchange my Kiwame-Anode-Resistors (Carbon-Film) against Wirewounds and see what will happen.
I implemented two switches to switch on the fly between 12V and 6 V heater-voltage per tube stage.
So, the tube-rolling was started. this is to be seen as my very first impression, need much more investigation, but I am looking forward if you have similar or different results:
B+ ist 250V. The first stage is with CCS at 6mA. So, I did not change the bias to optimize for each tube, I understand this imperfection of this process, but I rather collect initial impressions than get lost in trying to remember how something was sounding hours or days later. But I would be very interested in your experience how does a 12BH7 changes its sonics quality when not used at 6 mA, but at 12 mA (or 6cg7 etc) etc.
The second stage was originally the ECC99, which sound rather technical and thin. The TAD 12BH7 changed that dramatically to transparent and harmonical at the same time. So, it stayed currently as the cathode follower with 250 Ohm cathode resistor, as well a Neoohm wirewound.
So, given these conditions, istarted to do some tube rolling in the first stage:
- Psvane 12au7 Reference: Warm, good tone, but a little lack of transparency and dynamic.
- JJ 802S: Very fast, very wide soundstage, a little too cool in my view, a little bit technical, but very dynamic, there is a lot of inner structure of how tone is generated. Still one of my reference-tubes here.
- TAD 12BH7: WOW !!! Nearly as transparent as the JJ802S, but warmer and more powerful, adult soundstage. VERY SERIOUS, maybe even better than the JJ802S
- Raytheon 6CG7: Brutal. Even bigger sound and more powerfull than the 12BH7. Like a 12BH7 on steroids. Everything is warm, but less deep space, much bigger instruments than before, in my view unnatural big. You think that your poweramp have now double the power. But you loose the right size of instruments, ervything come more into the front and is less deep.
- Russian 6H23-EV ( my favourite 6922): As well like a 12au7 on steroids...but is it not as neutral as the above. It adds a signature which goes into the direction of a lot off pressure, a bit more noisy, flatter in space, more liek a small brother of the 6CG7, but with a more realistic size of the instruments.
So, I will investigate this further, please let me know what your findings are and if you have similar impressions or hints what to try as well.
ON the resistor front: My initial impressions hold true. Wirewound rules over Tantalum. Next will be the Rhopoint Wirewound against Neohm as I/V. I iwll as well exchange my Kiwame-Anode-Resistors (Carbon-Film) against Wirewounds and see what will happen.
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How are you all measuring the current?
I've set the LM334 up as per Broskie's instructions:
Note that 10mA, the optimal value for most Unbalancer setups, does not receive a
resistor value, but we can readily see that 6.8 ohms is the correct value. (The LM334
datasheet goes into much more detail, but for tube work, 6.8 ohms is close enough.)
Although 10mA is the LM334's maximum current flow, the device sees less than 10V
with most tubes, such as the 6CG7 and 12AU7, so the device's dissipation is usually
less than 100mW, well below its 400mW limit. Nonetheless, it is a good idea to attach
a small heatsink to the IC, as it better ensures an accurate idle current.
I didn't use a heatsink as there wasn't much heat being generated at all, and I'm using a pair of 6N23P at the input and a pair of 6CG7 at the output. The sound is phenomenal - excellent bass definition. However, from reading through the thread, I'm slightly concerned about the mA currents you are referencing for different tubes - especially given the Broskie's manual notes 6.81R for every tube example he gives....
I used the same settings as you did, so 5ma per triode.
Allen Wright wrote once in his preamp cookbook that the 6922 needs at least 10MA per triode before it starts to sing...12bh7 is a 3.5 watt tube vs 6922 1,5 watt...that is why I believe the tubes do not play yet at their sound capabilitieties with 5 mA. 5mA hold the ratio of 24k load impedance at 250 Voot b+ in a nice, stabile relationship for headroom. But when you want to know how the tube can sound, we need to adopt potentially b+, Anodeload and current, that is why I asked if anyone has experience on th changes in sound when doing so....
Allen Wright wrote once in his preamp cookbook that the 6922 needs at least 10MA per triode before it starts to sing...12bh7 is a 3.5 watt tube vs 6922 1,5 watt...that is why I believe the tubes do not play yet at their sound capabilitieties with 5 mA. 5mA hold the ratio of 24k load impedance at 250 Voot b+ in a nice, stabile relationship for headroom. But when you want to know how the tube can sound, we need to adopt potentially b+, Anodeload and current, that is why I asked if anyone has experience on th changes in sound when doing so....
Broskie OTL Variations & Current-Mirror-Based Push-Pull Buffer
This was Nov 13.
Is there anyone that has any knowledge what's happening
with the pcb's (or John for that matter, hope his alrigth) ?
This was Nov 13.
Is there anyone that has any knowledge what's happening
with the pcb's (or John for that matter, hope his alrigth) ?
Hi are you guys running the 6n23p on 250v B+ ?
I tried 5814a RCA from 1966 as input tube, but the JJ ecc802s was better. I have ordered TAD 12bh7 and EH 6072a based on your comments.
I changed the output coupling cap from RTI film to jantzen superior z cap. That really took away the artificialness in human voices - now they sound much more lifelike and natural. Tried also some Russian k75-10 - more warm sound but definitely not neutral. Also swapped in some K73-16 that I had good experience with earlier - but they were dull sounding - so they were removed quickly again.
Blitz - really appreciating that you share your experience with different resistors, caps and tubes in the unbalancer
Best regard
Søren
I tried 5814a RCA from 1966 as input tube, but the JJ ecc802s was better. I have ordered TAD 12bh7 and EH 6072a based on your comments.
I changed the output coupling cap from RTI film to jantzen superior z cap. That really took away the artificialness in human voices - now they sound much more lifelike and natural. Tried also some Russian k75-10 - more warm sound but definitely not neutral. Also swapped in some K73-16 that I had good experience with earlier - but they were dull sounding - so they were removed quickly again.
Blitz - really appreciating that you share your experience with different resistors, caps and tubes in the unbalancer
Best regard
Søren
Yes, I used 250 v as well for the 6922.
You can tune it like you like, reg. 2v. The 6922 has double the amplification than the rest of the bunch, but if you like the 6922 soundwise best: Great, you can lower the i/v resistor to half of its value and drive the dac more in current mode which sounds better. I am using 20 ohm in double mono setup of the dac for 12au7. With the 6922 in double mono 10 ohm would be fine. to get to 2v i guestimate.
You can tune it like you like, reg. 2v. The 6922 has double the amplification than the rest of the bunch, but if you like the 6922 soundwise best: Great, you can lower the i/v resistor to half of its value and drive the dac more in current mode which sounds better. I am using 20 ohm in double mono setup of the dac for 12au7. With the 6922 in double mono 10 ohm would be fine. to get to 2v i guestimate.
K73-16 are strange – in solid state gear they sound phenomenal, but with tube gear they seem to suck the life out of the sound!
Re the B+, note that the Broskie circuit halves the b+ for the input tubes. Hence on mine, I get 140v on the 6N23P (input tube), but 240v on the 6CG7 (output tube) – this is measured on the square solder pad of each tube, with reference to the GND terminal in the middle of the board (sorry, don’t know the specific terminology here).
Re the B+, note that the Broskie circuit halves the b+ for the input tubes. Hence on mine, I get 140v on the 6N23P (input tube), but 240v on the 6CG7 (output tube) – this is measured on the square solder pad of each tube, with reference to the GND terminal in the middle of the board (sorry, don’t know the specific terminology here).
Well, it does not Half b+...b+ is 250v. you are measure below the Anode resistor. the anode load resistor of 24k produces at 5ma a voltage drop of 120v. Over this anode load resistor the voltage swing is defined of the Anode of the tube... So, with a current source at the cathode, the tube sees the remaining 130v*0,005mA=0,65Watt, which is pretty save for the 6922. you could run the 6922 with double the current which Allen Wright adivised.
Yes, I did not tried this part yet...changing from 12au7 and 22 ohm to 6922 and 10 ohm - both with Neoohm Resistors...need to order the neoohms in 10 ohm first. You could go even further with an 12ax7 and 4 Ohm I guess...at a diffferent current of 1 mA though, so no plug and play.
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...Too much fun and stuff to play with...I have on my list as well:
Good Design Bad Design and DIY: Juli 2010
(build your own I/V-Resistor with Manganin-Wire, which is 86% Copper and should sound best...)
One El34 just died in my Amp and I need to fix this first as it seems it destroyed a reistor somewhere if I interpret the smell right...so slowed down again...
Good Design Bad Design and DIY: Juli 2010
(build your own I/V-Resistor with Manganin-Wire, which is 86% Copper and should sound best...)
One El34 just died in my Amp and I need to fix this first as it seems it destroyed a reistor somewhere if I interpret the smell right...so slowed down again...
Broskie gives an example of an IV stage using the 12AX7 w/Unbalancer here:
The Unbalancer
I think all you'd really need to change is the 6.81 resistor for the LM334 (not sure what value you would need). You could even try a 5751, which should sound fantastic.
Interestingly, the 6072/12AY7 is quite similar to the 12AX7 as per the datasheet, so perhaps you could use the 12AX7/5751/6072 to cycle through a few tests on the gain required.
That said, I changed input tubes from the 6072 to the 6CG7 then to the 6N23P (using the heater jumpers and 0.1uF capacitors to ground the tubes that have screens) without needing to change any part of the circuit. As I said in an earlier post, thank god for Broskie!
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