I'm new to SS builds with discrete components- I've populated a bunch of chipamp-type boards but that's the extent of my SS diy.
I have built a (big) handful of tube amps, from scratch -all fairly 'low-powered' amps. (ex RH84, Pointz' 6V6 Musical Machine, Chinese SE EL34).
I certainly would never try to operate any of those little tube amps 'wide open' (no input attenuation between the CD player and amp) in my 12 x 14 foot listening room - the windows would be rattling and the neighbours would notice.
In the past few weeks, I've put together a few Pass designs - BOSOZ 'preamp', ACA amps, and now one channel of an F6.
After I built the first channel of the ACA, I complained (here) about the lack of volume. Folks were very helpful with explanations -it's an 'instructional' project, 'can't expect much', impedance matching, my CD player isn't a good source, etc..
OK, I thought - I'll build a REAL Pass power amplifier.
I finished one channel of my F6 yesterday, and did a bit of testing today.
It's biased hot enough (1.8-2A) to warm up a 9 lb heatsink to 40C generally and 60C right next to the MOSFET.
It's producing 24 watts of output power before it starts clipping (analog scope and HP oscillator), with a 1kHz sine wave input, into an 8 ohm power resistor load.
My 'problem' is that it takes a 7 volt p-p input to get the amp producing that power.
I can plug my CD player directly into the input of the F6 amp and get a reasonable listening volume from a 85-90dB speaker.
I measured (with a digital scope) a couple of typical CD recordings - the average 'peak' output level was about 500mV p-p. Injecting a 500mV p-p sine wave into the F6 gave 0.95 volts RMS at the output, or 0.11 watts. The average 'non-peak' level was about 200mV p-p. This would drive the F6 to produce 0.015W of output.
Do I need to stick a preamp with a lot of gain between my CDP and the F6?
Suggestions?
If so, why don't people emphasize this issue more in all the 'build guides' and other enthusiastic postings here?
Or, have I built my amps incorrectly?
It seems very ironic to me that the popular Pass 'preamps' like the B1 and the BOSOZ don't have much (any) gain, so are no help in this situation.
It's amusing to build a 'heat-producing device' for the living room, but a heat sink really doesn't compare with some nice glowing tubes for visual interest, so, for me, a SS amp has to 'earn its keep' with some music power.
I'd appreciate comments from Pass enthusiasts. Thanks!
I have built a (big) handful of tube amps, from scratch -all fairly 'low-powered' amps. (ex RH84, Pointz' 6V6 Musical Machine, Chinese SE EL34).
I certainly would never try to operate any of those little tube amps 'wide open' (no input attenuation between the CD player and amp) in my 12 x 14 foot listening room - the windows would be rattling and the neighbours would notice.
In the past few weeks, I've put together a few Pass designs - BOSOZ 'preamp', ACA amps, and now one channel of an F6.
After I built the first channel of the ACA, I complained (here) about the lack of volume. Folks were very helpful with explanations -it's an 'instructional' project, 'can't expect much', impedance matching, my CD player isn't a good source, etc..
OK, I thought - I'll build a REAL Pass power amplifier.
I finished one channel of my F6 yesterday, and did a bit of testing today.
It's biased hot enough (1.8-2A) to warm up a 9 lb heatsink to 40C generally and 60C right next to the MOSFET.
It's producing 24 watts of output power before it starts clipping (analog scope and HP oscillator), with a 1kHz sine wave input, into an 8 ohm power resistor load.
My 'problem' is that it takes a 7 volt p-p input to get the amp producing that power.
I can plug my CD player directly into the input of the F6 amp and get a reasonable listening volume from a 85-90dB speaker.
I measured (with a digital scope) a couple of typical CD recordings - the average 'peak' output level was about 500mV p-p. Injecting a 500mV p-p sine wave into the F6 gave 0.95 volts RMS at the output, or 0.11 watts. The average 'non-peak' level was about 200mV p-p. This would drive the F6 to produce 0.015W of output.
Do I need to stick a preamp with a lot of gain between my CDP and the F6?
Suggestions?
If so, why don't people emphasize this issue more in all the 'build guides' and other enthusiastic postings here?
Or, have I built my amps incorrectly?
It seems very ironic to me that the popular Pass 'preamps' like the B1 and the BOSOZ don't have much (any) gain, so are no help in this situation.
It's amusing to build a 'heat-producing device' for the living room, but a heat sink really doesn't compare with some nice glowing tubes for visual interest, so, for me, a SS amp has to 'earn its keep' with some music power.
I'd appreciate comments from Pass enthusiasts. Thanks!
From memory F6 has a gain of around 5.
To drive the amp to clipping you will need a preamp with gain of at least 6dB.
If you need that level of volume then what that is telling you is you probably need a 50 to 60W amp or speakers with higher sensitivity.
Driving it to clipping is not a good way to listen to music.
To drive the amp to clipping you will need a preamp with gain of at least 6dB.
If you need that level of volume then what that is telling you is you probably need a 50 to 60W amp or speakers with higher sensitivity.
Driving it to clipping is not a good way to listen to music.
Thanks for the quick response.
These Pass projects should really come with a 'user warning' about the need for a preamp with plenty of gain, even when using a CD player as source- something not required with any tube or chip amp project I've met. I think I've made a (common?) beginner mistake with my choice. Fun 'scratch' builds, though....
Or, somebody smarter than me could design a simple front end for the Pass amps which would make it usable without the need for a separate preamp power supply...
I don't want to drive the amp to clipping. If I'm going to have a 'hot and heavyweight curiosity' taking up space in my listening/living room, I need it to play music at a reasonable listening level , and hopefully have some 'reserve' to handle the occasional loud dynamic.
Or just go back to my 5-10W tube amps which do the job, or the MyRef chip amp, or my thrift store commercial low powered SS amps with the volume control set at '3' on a 1-10 scale.
These Pass projects should really come with a 'user warning' about the need for a preamp with plenty of gain, even when using a CD player as source- something not required with any tube or chip amp project I've met. I think I've made a (common?) beginner mistake with my choice. Fun 'scratch' builds, though....
Or, somebody smarter than me could design a simple front end for the Pass amps which would make it usable without the need for a separate preamp power supply...
So, should I build something like an IC preamp stage and tuck it into the case with the F6?
I was looking at this Rod Elliott project using OPA2134 opamps:
High Quality Audio Preamp
I can derive the +/-15v supply for the preamp from the +/-24 v F6 rails using 7815 and 7915 regulators?
I was looking at this Rod Elliott project using OPA2134 opamps:
High Quality Audio Preamp
I can derive the +/-15v supply for the preamp from the +/-24 v F6 rails using 7815 and 7915 regulators?
Thanks for the quick response.
I don't want to drive the amp to clipping. If I'm going to have a 'hot and heavyweight curiosity' taking up space in my listening/living room, I need it to play music at a reasonable listening level , and hopefully have some 'reserve' to handle the occasional loud dynamic.
Or just go back to my 5-10W tube amps which do the job, or the MyRef chip amp, or my thrift store commercial low powered SS amps with the volume control set at '3' on a 1-10 scale.
These Pass projects should really come with a 'user warning' about the need for a preamp with plenty of gain, even when using a CD player as source- something not required with any tube or chip amp project I've met. I think I've made a (common?) beginner mistake with my choice. Fun 'scratch' builds, though....
Or, somebody smarter than me could design a simple front end for the Pass amps which would make it usable without the need for a separate preamp power supply...
These "Pass projects" are mostly based on Firstwatt designs. The philosophy is explained clearly on the home page.
http://www.firstwatt.com/
If you are looking for 500w of power, look elsewhere
. Sent from my iPad using Tapatalk
You used the 850g correct? Could it change the gain structure?
http://www.diyaudio.com/forums/pass-labs/166784-pictures-your-diy-pass-amplifier-392.html
Hammond 850G transformer. 150:600
http://www.mouser.com/Search/m_Prod...nufacturing/850G/&qs=Omd18uQ5iJExvtU1gRjl2Q==
http://www.diyaudio.com/forums/pass-labs/166784-pictures-your-diy-pass-amplifier-392.html
Hammond 850G transformer. 150:600
http://www.mouser.com/Search/m_Prod...nufacturing/850G/&qs=Omd18uQ5iJExvtU1gRjl2Q==
I would suggest a preamp, BA-3 pre project is a perfect diy project with a board from our store. For a scratch build I really like the LSK pre, both Juma's and the one presented at the Burning Amp Festival by Nelson. I own all 3. Needing a pre depends on source used, speakers and listening level preference. With a CD player a buffer is all that I need. When using my turntable a pre is definitely needed. To me the sound is more dynamic using a pre but then I may just be playing louder with a pre.
But you're only listening to one channel. You would get a +6db increase when using the second channel.
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VictoriaGuy , you choose the wrong trafo , your implementation is rather poor , components are cheapy ones , power supply is NOT what it should be , what else ....
F6 is an great amp , but it has to be build the right way , and this way is the BETTER way , not the cheapy one ...
if you want the best from your (any) device give it the best , in every way
.
F6 is an great amp , but it has to be build the right way , and this way is the BETTER way , not the cheapy one ...
if you want the best from your (any) device give it the best , in every way
.
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if properly wired , 850G will have same voltage ratio as Jensen used originally
as Papa wired it it is having primary (nominally) 150R and two independent secondaries of (nominally) 150R
which is exactly as 850G declaration 150R CT:600R CT (two 150R secondaries wired in series are giving 600R CT)
Jensen JT123 is practically classic repeater , having 4 independent coils of (nominally) 150R each
You are comparing amps (gainclone, etc) with 30db of gain against firstwatt amps with 15db of gain. Iam not surprised. Gainclones are designed to be used without a preamp. All the gain is in the amp. The firstwatt stuff will play nice with no preamp gain into really sensitive speakers but won't work well with the speakers you have now.
The ba3 preamp can run off your existing 24/-24 psu. A jfet boz can be built with batteries. Lots of options. Even a cheap eBay ic preamp will get you some gain.
The ba3 preamp can run off your existing 24/-24 psu. A jfet boz can be built with batteries. Lots of options. Even a cheap eBay ic preamp will get you some gain.
VictoriaGuy , you choose the wrong trafo , your implementation is rather poor , components are cheapy ones , power supply is NOT what it should be , what else ....
F6 is an great amp , but it has to be build the right way , and this way is the BETTER way , not the cheapy one ...
if you want the best from your (any) device give it the best , in every way
.
Explain to me how using different 'quality' components will change the gain structure of the F6 amp, and I will listen attentively. We are discussing the input sensitivity (in volts and mV), not anything very 'emotional' or abstract.
I think Mr Pass has made it pretty clear that 'standard' components (I followed the BOM carefully) will do the job in his designs.
The Hammond 850G is equivalent (better,probably) than the Jensen - exactly the same type, with four 150 ohm windings and the same winding resistances. Perhaps your F6 would sound better if you used the $100+ Hammond instead of a cheaper alternative.
Good point.
I was thinking along those lines, but once I re-read the Hammond and Jensen specs they seemed almost identical. I have the Hammond(s) on hand here, so they seemed a clear option.
The specs are here:
Hammond Mfg. - Broadcast Quality Audio Transformers - (560, 800-844 & 850 Series)
It's not 'sound quality' but gain that's the issue.if sound quality of FW amp didn't bought you , hopefully taught you to read specs, before building anything
I've read thousands
() of posts in 'Pass amp' discussion threads and nobody seems to be emphasizing the point I'm making - so that other beginners will not be disappointed:The Pass First Watt power amps don't have enough gain to be used in the same way as your other diy project amps, which will function without an added gain stage between a CD player or other 'line level' source. Despite the very high power requirements, you will be disappointed unless you put a preamp with considerable gain between your line level source and your Pass power amp.
It would be very useful if somebody would produce a 'summary table' with the basic gain info for the Pass circuits. The power amps don't compare with other diy or commercial power amps in gain, and some of the very popular Pass 'line stages' (B1,BOSOZ) don't have enough gain to do the job either.
These "Pass projects" are mostly based on Firstwatt designs. The philosophy is explained clearly on the home page.
FIRST WATT
If you are looking for 500w of power, look elsewhere
I've read that ;thanks for the link.
Does it state there that the input sensitivity is too low for effective use with a line level source without a preamp?
I clearly stated that my tube amps with <10W of power can produce too much 'sound pressure' (aka loudness) with my speakers. So I'm not looking for very high output power, at all.
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