ADB......please explain in more words about what you mean by "central image" please.
My personal understanding is that a mono system would have the best central image, everything appears to come from between the two speakers.
In a stereo system, every sound source (instruments, vocal...etc....) should image at their own place within the stage.......and not always in the center.
Correct me if I am wrong please.......anyone please
It would if I was using a pot as a volume control, and I have in the past, but with a TVC on the output it would just add more components in the signal path. If I was making a new TVC I would probably get a pair of these -
An externally hosted image should be here but it was not working when we last tested it.
But I bought a ready made TVC with Sowter 9335s for £150!
A stereo image refers to the soundstage, in this case left/right positioning. To some it isn't important. To me it is, so if everything is shifted to one side I find it annoying. It also messes up the illusion of stage depth.ADB......please explain in more words about what you mean by "central image" please.
My personal understanding is that a mono system would have the best central image, everything appears to come from between the two speakers.
In a stereo system, every sound source (instruments, vocal...etc....) should image at their own place within the stage.......and not always in the center.
Correct me if I am wrong please.......anyone please
And if I played a mono recording on my stereo system that mono image would also be shifted to one side.
1-2 dB gain difference (if it is frequency independent) of whole system is -for me- acceptable. I have a sofa against the loudspeakers, I like the music sitting on the left or right side, as well on the sweet spot.
I don't use balancing for decades.
I sit to the right, my wife to the left. But if the balance isn't right, the depth suffers. In my room I can get images a long way back, and if the balance is spot on then voices or instruments in the centre of the background stay central despite the foreground being biased towards my side.
I have no problem with 1-2dB, but what I am worried about is the channel imbalance in each component compounding. My system is going to have a tube phono stage, which has potential to be slightly unbalanced, into an 01a preamp, which might be unbalanced, into a pair of monoblock baby hueys, which could all be unbalanced by 1 or 2 dB, which could add up, right?
awkwardbydesign,
That's a good point. I can also always switch the left and right channel tubes in my preamp, as i'm going to build the baby huey's asymmetrically for aesthetics and to save on space. what i'll probably do is build it without a balance pot, and leave a space for one, as i can always add it really easily later.
I highly recommend reading up on the huey's by the way, the wealth of information in that thread is highly useful to anybody interested in tubes.
I'm still quite young and only working with the budget i get from summer jobs, and last summer with my phono preamp i only had less than ten dollars left at the end of the project, so i want to make sure i get my BOM spot on the first time. I also just want to thank the DiyAudio community for being so incredibly knowledgeable and helpful. You guys know everything about everything, and it's incredible being able to talk to the designers of a product.
That's a good point. I can also always switch the left and right channel tubes in my preamp, as i'm going to build the baby huey's asymmetrically for aesthetics and to save on space. what i'll probably do is build it without a balance pot, and leave a space for one, as i can always add it really easily later.
I highly recommend reading up on the huey's by the way, the wealth of information in that thread is highly useful to anybody interested in tubes.
I'm still quite young and only working with the budget i get from summer jobs, and last summer with my phono preamp i only had less than ten dollars left at the end of the project, so i want to make sure i get my BOM spot on the first time. I also just want to thank the DiyAudio community for being so incredibly knowledgeable and helpful. You guys know everything about everything, and it's incredible being able to talk to the designers of a product.
Good for you. I'm not so young
but still enjoy playing. And I agree, being able to talk to genuine experts is a great help. I couldn't have contemplated building these DHT pre-amps without their help. 
Hi,
I have a 71a linestage that is transformer coupled with the TVC at the output. I did search the thread and read a bit but could not find a definitive as to the whether people prefer the transformer step down with TVC at the output or a gyrator loaded DHT with the TVC at the input. It does not look like a good idea to put the TVC at the output of the gyrator loaded DHT circuit but I'm not an expert. Any opinions?
Thank you in advance,
Chris
I have a 71a linestage that is transformer coupled with the TVC at the output. I did search the thread and read a bit but could not find a definitive as to the whether people prefer the transformer step down with TVC at the output or a gyrator loaded DHT with the TVC at the input. It does not look like a good idea to put the TVC at the output of the gyrator loaded DHT circuit but I'm not an expert. Any opinions?
Thank you in advance,
Chris
Why not? Ale's gyrator output impedance in the few 100R- kOohm region (depending of the "lower" JFET).
If the source (step down transformer, gyrator or CCS output) impedance "enough" low, it's working.
I use S&B TVC (CCS loaded #26, 220+100 nF coupling capacitor, 400H TVC) for years ago.
Hi,
Thank you. Can you be more specific regarding the output impedance? Based on what you wrote a think you meant in the 100r-1k ohms but I'm not sure. In my case this will work with either of my TVCs (Tribute/Intact). For those that have tried both, what are the sonic advantages? I know there will be more gain and greater bandwidth.
Thanks everyone,
Thank you. Can you be more specific regarding the output impedance? Based on what you wrote a think you meant in the 100r-1k ohms but I'm not sure. In my case this will work with either of my TVCs (Tribute/Intact). For those that have tried both, what are the sonic advantages? I know there will be more gain and greater bandwidth.
Thanks everyone,
My CCS (DN2540-IXTP01N100D) output impedance (at 1kHz) about 500R (measured).
Ale's gyrator:
- "upper" FET also IXTP01N100D;
- "lower" FET
J310: 1k25 (measured);
2SK 170: about 150R (measured) -but current is limited, up to 10-12mA - ;
AOT1N60: 130R (measured);
DN2540: about 65R (only simulation, measuring a little problematic);
BF862 about 200R (sim);
BSH111BK was not simulated, but Ale use it with satisfaction.
Ale's gyrator:
- "upper" FET also IXTP01N100D;
- "lower" FET
J310: 1k25 (measured);
2SK 170: about 150R (measured) -but current is limited, up to 10-12mA - ;
AOT1N60: 130R (measured);
DN2540: about 65R (only simulation, measuring a little problematic);
BF862 about 200R (sim);
BSH111BK was not simulated, but Ale use it with satisfaction.
My understanding is that using a TVC after an output transformer is not recommended; two transformers together.
Hi
I don't think transformer feeding transformer is wrong, just needs to be appropriately designed. The gyrator results in gain levels that might overload the primary of a TVC.
So thinking that gain structure and impedance matching both significant here.
Euro21's set up interests me and I would be interested to know if he is feeding it from CD standard 2V output, what gain the CCS'ed 26 has and what max voltage the primary of the S&B TVC.
Cheers
Gn
I don't think transformer feeding transformer is wrong, just needs to be appropriately designed. The gyrator results in gain levels that might overload the primary of a TVC.
So thinking that gain structure and impedance matching both significant here.
Euro21's set up interests me and I would be interested to know if he is feeding it from CD standard 2V output, what gain the CCS'ed 26 has and what max voltage the primary of the S&B TVC.
Cheers
Gn
My Sowter 9335 transformers are quoted at 7.7v max. But I use the 32bit digital volume control on my Benchmark DAC3 to attenuate the signal somewhat before the input on my 01A to reduce the voltage in. The pot on the input is wide open, so just 100k across the input. It seems to work OK. Using the TVC on the output of my transformer coupled 26 softened the sound more than I liked, but the gyrator coupled 01A sounds OK.
If I remember correctly, the S&B TX-102 recommended maximum input voltage is 7.75 RMS.
I usually use this TVC at about -20dB "gain", output voltage about 0.8V RMS (my daily used equipment is CCS loaded D3a, source follower, 300B SE 5k:8, 89dB loudspeaker), so TVC's input voltage may be at about maximum.
The CCS loaded #26 gain is about 7.5, but all of my source produce only about 1.1..1.2V RMS at 0dB, so max. output 9V RMS.
I have old measurements of whole #26 preamp (at -20dB TVC gain):
1V input THD output is 0.014/0.017 (practically this is the tubes distortion, mainly even);
bandwidth -1dB 20Hz...45kHz,
-3dB 14Hz...65kHz.
When I used my Slagle's TVC at the output of the 4P1L preamp when driving it at full signal, I didn't like the sound as much as having it at the input. I'd probably suggest this was to the increased distortion at lower frequencies on +10Vrms output. Never managed to measure it and if I get the time, will do in the future.
i'd rather locate the volume control at the input. If properly implemented the DHT preamp should be dead quiet and no reasons why it should be connected directly to the amp.
cheers
Ale
i'd rather locate the volume control at the input. If properly implemented the DHT preamp should be dead quiet and no reasons why it should be connected directly to the amp.
cheers
Ale