In addition to what Salas instructed about preamp and power amp matching, I assume this short thread (actually the end of it) will give you an answer for F4 amp (as well as for any other power amp) compatibility with DCG3 (optimal gain setup and etc.).
F5T gain structure and preamp choice
I also made short YouTube video about how I determined my F5T max input voltage before clipping.
YouTube
I hope you guys remember Salas comment about DCG3 tweaks where he mentioned Quasimodo tester for power transformer snubbering.
Well, I have that tester and I added snubbers to my DCG3. Subjectively, I do hear an improvement. I do not want to use all these gourmet audio marketing words to describe it, but I feel more air, more bass (no subwoofer) and absolutely no noise/hiss/hum at max volume (10 cm ear from tweeter). Unfortunately, it took two attempts to come up with the right values for RC section in snubber. My tester got some cold-solder error (SMD type with very small components). But after I fixed it, all was corrected and snubber works as intended. So, if you have Quasimodo then please try it and share with your experience.
F5T gain structure and preamp choice
I also made short YouTube video about how I determined my F5T max input voltage before clipping.
YouTube
I hope you guys remember Salas comment about DCG3 tweaks where he mentioned Quasimodo tester for power transformer snubbering.
Well, I have that tester and I added snubbers to my DCG3. Subjectively, I do hear an improvement. I do not want to use all these gourmet audio marketing words to describe it, but I feel more air, more bass (no subwoofer) and absolutely no noise/hiss/hum at max volume (10 cm ear from tweeter). Unfortunately, it took two attempts to come up with the right values for RC section in snubber. My tester got some cold-solder error (SMD type with very small components). But after I fixed it, all was corrected and snubber works as intended. So, if you have Quasimodo then please try it and share with your experience.
Did you also up the DCG3 gain to 5X (2K R6) or the particular SE to BAL transformers already add some extra gain? Because F4 is a buffer amp with no gain and it could use 14dB (5X) of line gain with sensitive speakers as Mr. Pass mentions in its manual. Unless you destine it only for use with the F6 which has 5X gain on its own of course.
Maybe the wife has a point in her preference after all because the Sparko is all bipolar while the AD is JFET input and it could be not strictly better than the sophisticated discrete Sparko in general but merely more adequate in this specific place.
Salas I am running 5x gain because of the F4s. Speakers are 90db. I don't think the Jensen's have any gain. I am at work so it will be later before I can check.
Overall everybody has a different response to sound. I respect my wife's ears. Sometimes I want something to sound better or different.
Overall everybody has a different response to sound. I respect my wife's ears. Sometimes I want something to sound better or different.
5X active gain is almost all you can squeeze out of a standard rails DCG3 and a 2VRMS source assuming 0dBFS recorded peaks. Since recordings avoid hitting the hard digital roof there is also 6 to 10dB headroom in the good loud enough ones. But if with F6 you will feel there is too much gain on the dial return to 3X.
Have you thought of pinnocchio's suggestion to check the JFET input OPA1642 too? If by any chance it will be to your preference you could save the expensive discrete Sparkos for signal path use in other projects than serving the less influential DC servo job here.
Have you thought of pinnocchio's suggestion to check the JFET input OPA1642 too? If by any chance it will be to your preference you could save the expensive discrete Sparkos for signal path use in other projects than serving the less influential DC servo job here.
Thank you!
you mean method from that thread? Simple, no-math transformer snubber using Quasimodo test-jig
Thank you for your insights. The Sparko was a on the moment purchase. The owner gave a small discount for my purchase. I will add the OPA1642 to my next Mouser or Digikey order. I am still learning!! I have built one of the Pass inspired DIY headphone amps that is running the AD823, so I will give the Sparko an audition in that amp.
Thanks
David
Thanks
David
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No as I do not posses a scope. Would I be better off using them without the sense connected?
Normally no. Because longer sense runs being exposed to more "outside world interference" have more chances in picking stuff we always check when we have a scope. When we don't and there is oscillation or noise in various intensities we normally can understand them by strange behavior like voltage instability, weird noises, or the sound has gone noticeably south. Another thing is we just subjectively compare Kelvin mode vs two wire mode and if the former wins all is well. If the latter wins means there could be some more RF or small anomaly with the other mode and we keep the two wire one since there is no scope to see what was it or how to change it.
Antek AS-0518 replacement
Hi guys,
I got my Tea Bag kit and I'm about to start building the DCG-3 however one of the first things on my list, the Antek AS-0518's, are out of stock. So, I was wondering if you had any suggestions for a replacement transformer(s) in the US. I am building the dual mono DCSTB Power Supply. I'm sorry if this question has already been answered but I couldn't find answers while searching this thread. There was a suggestion that the Hammond 229D34 could work. It's through hole mount but I suppose I can figure that out with perfboard. It says it's 34v but I'm assuming when wired for center tap it would give me the required 17v. It's available now at Mouser and Digikey—more expensive than the Antek but I really want to get building. Thanks for any advice.
Hi guys,
I got my Tea Bag kit and I'm about to start building the DCG-3 however one of the first things on my list, the Antek AS-0518's, are out of stock. So, I was wondering if you had any suggestions for a replacement transformer(s) in the US. I am building the dual mono DCSTB Power Supply. I'm sorry if this question has already been answered but I couldn't find answers while searching this thread. There was a suggestion that the Hammond 229D34 could work. It's through hole mount but I suppose I can figure that out with perfboard. It says it's 34v but I'm assuming when wired for center tap it would give me the required 17v. It's available now at Mouser and Digikey—more expensive than the Antek but I really want to get building. Thanks for any advice.
AS-2218 - 200VA 18V Transformer - AnTek Products Corp
Why don't you just use the 200VA antek version.
Or this:
Avel Lindberg Y236502 160VA 18V+18V Toroidal Transformer
Why don't you just use the 200VA antek version.
Or this:
Avel Lindberg Y236502 160VA 18V+18V Toroidal Transformer
Also, I would think that 100VA per channel is quite overrated although Salas will probably have the definitive answer. I would be comfortable with 50VA per channel, no problem. Especially with less than 150ma bias. But it looks like Antek is out of stock for 50VA as well.
Personally I am using 50VA for both channels (Single mono). But I am using a different regulator.
Personally I am using 50VA for both channels (Single mono). But I am using a different regulator.
I am using 50VA toroidal transformers, with 2 x 18 secondaries for my build. Each board is connected to one transformer, so 2 transformers for dual-mono configuration.
This is what I am using, but it's with 230v input voltage only:
MCFE050/18 - MULTICOMP - Toroidal Transformer, 41.7mm x 87.3mm, 50 VA, 2 x 18V, 1.39 A, Chassis | element14 Singapore
If my understanding is correct, 2 units of this should work:
VPT36-1390 Triad Magnetics | Mouser
This is what I am using, but it's with 230v input voltage only:
MCFE050/18 - MULTICOMP - Toroidal Transformer, 41.7mm x 87.3mm, 50 VA, 2 x 18V, 1.39 A, Chassis | element14 Singapore
If my understanding is correct, 2 units of this should work:
VPT36-1390 Triad Magnetics | Mouser
Any 48-50VA per channel at 17-0-17 or 18-0-18 secondaries AC spec will do. Be it rectangular or toroidal. Quality construction and magnetic shielding are welcome of course but usually costly. That Hammond is not the cheapest but claims some electrical benefits though mounting it is a PITA. That Antek from the BOM has decent quality and some magnetic shielding at a good price. But unavailable for now as you guys say.
More VA from the same company for comparable dollars to other brands smaller models sure looks attractive at first but the extra box space occupied and the stronger magnetic field emitted should be considered too.
More VA from the same company for comparable dollars to other brands smaller models sure looks attractive at first but the extra box space occupied and the stronger magnetic field emitted should be considered too.