31-03-2017, 09:21 AM
Why I say thank you my Diabolical friend, yes agreed it probably makes no difference in audio circuits but there must have been a reason (and RF usage may be it) why old style caps were marked with outer foil end but it may answer why modern ones are not. It was probable best practice in the day so you did not think about it when you working on equipment and thus avoided pitfalls and issues when it did matter.
Yes I agree the MAAS 50 looks interesting once you take all the R/C bandwidth limiting parts out of it. I did build some amps in the past my first project I seem to remember (and the only one I can recall to date) was an ETI project for a hybrid preamplifier. It used something like BC109 in front end to boost signal for MC cartridges and then used an ECC88 for the next or line stage it was about the late 80s or early 90s (the issue is on the American Broadcast site), I think it was November or December 1990.
Who says valve amps are not quiet, it operated from a stone still silent blackness, even thought it was a sat under a table for safety's sake of course and not in a box of any description, looking more like a rats nest than an amplifier. At the time I used it to drive a pair of Vortexion PA No.1 amps (From WW2), massive iron in those (it was in production from about 1936/37, later rebadged as CP20). I went straight in with the signal on the volume pot wiper (as I have the original user manual with War Department warnings and schematic - there is only local feedback around the 6V6 output tubes - no global feedback at all) , worked absolutely fine and was jaw droppingly good. Source Ortofon MC10 cartridge, Rotel RP830 turntable, Philips CD player, Philips 1970s tuner, a cassette deck and Kef Cantor III speakers.
One other kit I remember making and selling in the end was an Audio Note Preamplifier and I do not think there is anything else, the last one was sort of PCB hard-wired.
Anyhow I digress I am looking to rebuild my 3 Williamsons with Woden WOT-25 output transformers, and yes it might be gilding the lily (which was name of a similar project in Audio Magazine) but in that design it may make a difference as it tends to be a bit marginal although I never had an issues with it motor boating. I know it may not make any difference but knowing that the components should be fitted in a preferred way (is a good habit and practice to get into) - well how can I put it if it is not done that way it triggers an OCD area of my functionality.
Plus I am looking to build 3 150 watt OTL Power Amps to drive my cutter heads for disc recording, there are other projects in the pipeline as well.
Ah yes which brings me to my final point, how do you work out the gain of a stage (simple maths please) and what its impedance is? I assume Mu comes into it somewhere or not? I assume if you were doing a block diagram of each stage then that would be expressed in dBs (at 600 R?)? That the voltages would be looked up on a table (or on-line calculator these days) and one figure would be taken away from the other or added? Ah yes now that I am getting older it is time to do the things I never did when I was younger, so it is time for me to tinker with my boys toys.
I could look it up in a book but they tend to be overly maths heavy (my maths is not as bad as I think it is) however the BBC technical books and documents are easy to read (mostly).
One of the reasons in the past I stayed with tube/valve equipment is that it was much more difficult to read a solid state design and not so easy to make PCBs, now with the advent of on-line tools, silk screen printing I am revisiting that area as well. Valves are easier in that sense as they are hard wired, plus with more components comes more errors and so on. The Mullard and the GEC books on audio amplifiers and layouts warn of issues and what is good practice in component layout for the novice at least.
Yes I agree the MAAS 50 looks interesting once you take all the R/C bandwidth limiting parts out of it. I did build some amps in the past my first project I seem to remember (and the only one I can recall to date) was an ETI project for a hybrid preamplifier. It used something like BC109 in front end to boost signal for MC cartridges and then used an ECC88 for the next or line stage it was about the late 80s or early 90s (the issue is on the American Broadcast site), I think it was November or December 1990.
Who says valve amps are not quiet, it operated from a stone still silent blackness, even thought it was a sat under a table for safety's sake of course and not in a box of any description, looking more like a rats nest than an amplifier. At the time I used it to drive a pair of Vortexion PA No.1 amps (From WW2), massive iron in those (it was in production from about 1936/37, later rebadged as CP20). I went straight in with the signal on the volume pot wiper (as I have the original user manual with War Department warnings and schematic - there is only local feedback around the 6V6 output tubes - no global feedback at all) , worked absolutely fine and was jaw droppingly good. Source Ortofon MC10 cartridge, Rotel RP830 turntable, Philips CD player, Philips 1970s tuner, a cassette deck and Kef Cantor III speakers.
One other kit I remember making and selling in the end was an Audio Note Preamplifier and I do not think there is anything else, the last one was sort of PCB hard-wired.
Anyhow I digress I am looking to rebuild my 3 Williamsons with Woden WOT-25 output transformers, and yes it might be gilding the lily (which was name of a similar project in Audio Magazine) but in that design it may make a difference as it tends to be a bit marginal although I never had an issues with it motor boating. I know it may not make any difference but knowing that the components should be fitted in a preferred way (is a good habit and practice to get into) - well how can I put it if it is not done that way it triggers an OCD area of my functionality.
Plus I am looking to build 3 150 watt OTL Power Amps to drive my cutter heads for disc recording, there are other projects in the pipeline as well.
Ah yes which brings me to my final point, how do you work out the gain of a stage (simple maths please) and what its impedance is? I assume Mu comes into it somewhere or not? I assume if you were doing a block diagram of each stage then that would be expressed in dBs (at 600 R?)? That the voltages would be looked up on a table (or on-line calculator these days) and one figure would be taken away from the other or added? Ah yes now that I am getting older it is time to do the things I never did when I was younger, so it is time for me to tinker with my boys toys.
I could look it up in a book but they tend to be overly maths heavy (my maths is not as bad as I think it is) however the BBC technical books and documents are easy to read (mostly).
One of the reasons in the past I stayed with tube/valve equipment is that it was much more difficult to read a solid state design and not so easy to make PCBs, now with the advent of on-line tools, silk screen printing I am revisiting that area as well. Valves are easier in that sense as they are hard wired, plus with more components comes more errors and so on. The Mullard and the GEC books on audio amplifiers and layouts warn of issues and what is good practice in component layout for the novice at least.
