First of all, thanks everybody.
So, if I understand correctly, look into CDP output voltage, frankenstein quick el cheapo passive to figure out exact gain need. I do have DMM, so I could just measure output voltage of the source.
Interesting that you guys mentioned “hair trigger” volume control syndrome. I have one of the Bryston preamp, driving Behringer 500 amplifier and that's exactly what I am getting.
On the other hand, I have heard a couple of passive setups in OPS and luck of dynamics was something that was bothering me as well. If I remember correctly it was Creek passive.
I'll get pods from Mouser and rig it up in a few days.
So, if I understand correctly, look into CDP output voltage, frankenstein quick el cheapo passive to figure out exact gain need. I do have DMM, so I could just measure output voltage of the source.
Interesting that you guys mentioned “hair trigger” volume control syndrome. I have one of the Bryston preamp, driving Behringer 500 amplifier and that's exactly what I am getting.
On the other hand, I have heard a couple of passive setups in OPS and luck of dynamics was something that was bothering me as well. If I remember correctly it was Creek passive.
I'll get pods from Mouser and rig it up in a few days.
http://www.tentlabs.com/
Interesting new 64 steps att (says that a buffer will come)
Also I find Promitheus TVC interesting, but still no tube
How does one make a tubepre with no gain, I believe there are very few around
Interesting new 64 steps att (says that a buffer will come)
Also I find Promitheus TVC interesting, but still no tube
How does one make a tubepre with no gain, I believe there are very few around
don't underestimate the quality of the "jaycar pot".
http://www.diyaudio.com/forums/showthread.php?s=&threadid=39258&perpage=10&pagenumber=1
col.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=39258&perpage=10&pagenumber=1
col.
A true unity gain preamp employing tubes can be done. You end up with something akin to an OPAMP, but with a lower open loop gain. The so called plate follower is an example.
If, as I suspect will be the case, this thread's originator needs only a buffered volume control, a "mundane" cathode follower will be employed. The small insertion loss associated with a CF is a non-issue, while the circuit's simplicity offers a 1st time builder genuine prospects of a successful outcome.
a huge range
classic? 6SN7. Flavour of the month? ECC88. Current non-flavour of the month? 12AX7. Defining factors? triodes, single envelope, reasonable availability, current driver (not voltage) good response to the 2V pp input. My circuit is basically the 'SN7 but with two separate tubes cos thats what I had. At hte cost of it all (really cheap...) I'd breadboard up an octal and noval option and try a bunch of the cheapest dual triode tubes I could find. You will learn heaps more than asking for a how-to here or by doing a paint-by-numbers kit.
classic? 6SN7. Flavour of the month? ECC88. Current non-flavour of the month? 12AX7. Defining factors? triodes, single envelope, reasonable availability, current driver (not voltage) good response to the 2V pp input. My circuit is basically the 'SN7 but with two separate tubes cos thats what I had. At hte cost of it all (really cheap...) I'd breadboard up an octal and noval option and try a bunch of the cheapest dual triode tubes I could find. You will learn heaps more than asking for a how-to here or by doing a paint-by-numbers kit.
I happened to have couple of spare 50K volume pots so I tried Eli D’s suggestion. At its maximum setting it was louder than I normally listen to so that’s good news for me. I did not notice the loss of dynamics compared to using my preamp’s analog “direct” mode (OPAMP used?). In fact it sounded pretty darn good (good news again).
But this is where it gets little mysterious. Initially I set both pots to 10K Ohm using multimeter and when the music started, it was at moderate volume already. Does this mean 10K volume pot may not be enough for my typical consumer level DVD player ($150 Sony)? Another question, at that initial setting, the output level wasn’t balanced so I had to turn one channel up which wasn’t the case with my preamp analog “direct” mode. Could this mean a defective volume pot?
But this is where it gets little mysterious. Initially I set both pots to 10K Ohm using multimeter and when the music started, it was at moderate volume already. Does this mean 10K volume pot may not be enough for my typical consumer level DVD player ($150 Sony)? Another question, at that initial setting, the output level wasn’t balanced so I had to turn one channel up which wasn’t the case with my preamp analog “direct” mode. Could this mean a defective volume pot?
Separate L/R volume controls or ganged volume + ganged balance controls are installed for very good reason. There are all sorts of reasons for imbalances between channels, including manufacturing differences between specimens of a particular part. 20% tolerance is commonplace among low cost controls.
The previous remark about ratio, not value, being key in a voltage divider is correct. You used a 10 KOhm tap on a 50 KOhm resistance. That 1/5 ratio works out to 14 dB. of attenuation.
Thank you Evaas and Eli.
Personally, I favor the theory of less circuit the better, so I am enthused about the way my experiment turned out. But just for something to keep in the back burner, what kind of issues would prompt the use of active preamp, distance between components or added coloration?
Personally, I favor the theory of less circuit the better, so I am enthused about the way my experiment turned out. But just for something to keep in the back burner, what kind of issues would prompt the use of active preamp, distance between components or added coloration?
Evenharmonics said:
Well, I'd say use 'em when they sound better
problems come about mostly because of impedance matching. The source (cd player, phono stage) output 'likes' to see a certain impedance at the input of the preamp, and the preamp output 'likes' to see a certain impedance at the power amp input. With a passive preamp (i.e. a pot) you can match one or the other, but not both. Buffers do a better job of matching impedance without gain, and active gain stages do it with gain. coloring is part of the bargain
Another preamp to consider. 
This one is by Frank and as everyone knows what Frank designs works without a question.
I have personally built this one and it offers good performance and is quite easy to put together. This would be my second choice for a line stage my first would be the Aikido. After hearing the Forplay I wouldn't consider it at all but then thats my opinion.
This one is by Frank and as everyone knows what Frank designs works without a question.I have personally built this one and it offers good performance and is quite easy to put together. This would be my second choice for a line stage my first would be the Aikido. After hearing the Forplay I wouldn't consider it at all but then thats my opinion.
Attachments
burnedfingers said:Another preamp to consider.
I have personally built this one and it offers good performance and is quite easy to put together. This would be my second choice for a line stage my first would be the Aikido. After hearing the Forplay I wouldn't consider it at all but then thats my opinion.
While I have no quibbles with that straight forward 6SN7 design, I reiterate that the appropriate gain structure must be determined 1st. Remember the previous remarks about "hair trigger" and a SS line stage. My gut feeling is that a "unity" gain design is going to be the appropriate choice. FWIW, I've got some ideas about 10M45S loaded ECC99 cathode followers that might be suitable.
All CDP I have state the impedance as 200ohm and output as 2 volts. I think it's pretty standard now.
Should I get the pods anyway and try it?
Remember guys, I can crank out insane speaker cabinets with exotic veneer and fancy finish but I am a noob then it comes to amps. So, pleas be patient with me.
Should I get the pods anyway and try it?
Remember guys, I can crank out insane speaker cabinets with exotic veneer and fancy finish but I am a noob then it comes to amps. So, pleas be patient with me.
Eli, I see some tube buffer kits out there and I was wondering if they are worth trying.
Analog Metric
Decware
Analog Metric
Decware
Evenharmonics said:
The DECWARE design is a common cathode gain block, not a buffer. While I have great respect for Steve Deckert, my loathing of 12AU7 voltage amplifiers should be common knowledge, by now. "Different strokes for different folks."
That 5670 based Analog Metric design might pan out. FWIW, I'm thinking about 2X nice PEC pots. PIO (for smoothness) cap. coupled to the higher gm ECC99, set up as 2X cathode followers. 10M45S CCS loads and 2X red LED bias would be used. A bypassed GE 40L3501 would be used in the O/P coupling positions. Either SS or tube B+ rectification is OK. Given constant current operation, a well filtered, unregulated, PSU is quite sufficient.
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