People need to just keep schematic they are using handy. Most inquiries here, the first requests from members are two things: clear pics, and which schematic your build uses. Concise answers can be given, for correct parts for your build.
Russellc
Russellc
what has Iron Pumpkin more than the iron pré?
transformer volume control?
transformer volume control?
buffers with more cojones, AVC, settable (autoformer) gain of 0db, +2db, +4db, +6db, +8db
in case of balanced, AVC is utter rarity - proper differential one
nothing more, nothing less
in case of balanced, AVC is utter rarity - proper differential one
nothing more, nothing less
Can Iron Pre have that ability with output trans you suggested? Just copy circuit? Or, not worth effort? SE creature.
Last edited:
not possible
horses for courses
speaking of SE, you already have choice between +6db and +12db of gain
0db also possible, simply leaving xformers in drawer
in that case, you're having fancy B1
horses for courses
speaking of SE, you already have choice between +6db and +12db of gain
0db also possible, simply leaving xformers in drawer
in that case, you're having fancy B1
Time spent drilling holes and assembling today. I am an amateurish machinist at best.
But close enough!
But close enough!
You realize of course that you are assuming an amplifier with gain... This is not always true.
... Imagine trying to use something like an F4. Your assumptions then are out the window.
Example, My current Conrad Johnson PV9 outputs 20Vrms with an input of 2Vrms... this is a gain of 20db. Which puts it in a very nice place to drive the full current out of the F4 at ~40Vpp. I routinely run the preamp at 2 o'clock, which puts it nicely in what I'd expect to be a linear range with no distortion or noise: the F4 is rated at 40Vpp... so that's 14.14Vrms ( 20/33/50 wpc into 8/6/4 ohms).
Indeed, many tube amplifiers have lots of gain... I think the lowest is around 10Vrms... modern ARC.... but CJ still drives 20Vrms. Single ended.
Now my quest is to go bridged F4.. so I need a balanced preamp that will put drive 80Vpp... for 100/133/200 wpc into 4/6/8 phms. That means ~28.28Vrms from the preamp. Hence, 40Vrms from the preamp will nicely drive the bridged F4s with room to spare.
That means a gain of 23db from the balanced preamp. Quite a bit more than your calculations.
Last edited:
"You realize of course that you are assuming an amplifier with gain..."
No, I'm not. Your assumption about my assumption is incorrect. 😉
"This is not always true."
Agreed. Thus, I would never assume all power amplifiers have gain.
... Imagine trying to use something like an F4. Your assumptions then are out the window.
No, they're not. And they're not assumptions. It's just math. If my math is incorrect, I welcome corrections.
"Example, My current Conrad Johnson PV9 outputs 20Vrms with an input of 2Vrms... this is a gain of 20db. Which puts it in a very nice place to drive the full current out of the F4 at ~40Vpp. I routinely run the preamp at 2 o'clock, which puts it nicely in what I'd expect to be a linear range with no distortion or noise: the F4 is rated at 40Vpp... so that's 14.14Vrms ( 20/33/50 wpc into 8/6/4 ohms)."
Yes, and ....
"Indeed, many tube amplifiers have lots of gain... I think the lowest is around 10Vrms... modern ARC.... but CJ still drives 20Vrms. Single ended."
Yes, and ...
"Now my quest is to go bridged F4.. so I need a balanced preamp that will put drive 80Vpp... for 100/133/200 wpc into 4/6/8 phms. That means ~28.28Vrms from the preamp. Hence, 40Vrms from the preamp will nicely drive the bridged F4s with room to spare."
Yes, and ... I've repeatedly shown you that in another thread. I fail to see your point.
"That means a gain of 23db from the balanced preamp. Quite a bit more than your calculations."
Where did I calculate a gain? Please show me.
No, I'm not. Your assumption about my assumption is incorrect. 😉
"This is not always true."
Agreed. Thus, I would never assume all power amplifiers have gain.
... Imagine trying to use something like an F4. Your assumptions then are out the window.
No, they're not. And they're not assumptions. It's just math. If my math is incorrect, I welcome corrections.
"Example, My current Conrad Johnson PV9 outputs 20Vrms with an input of 2Vrms... this is a gain of 20db. Which puts it in a very nice place to drive the full current out of the F4 at ~40Vpp. I routinely run the preamp at 2 o'clock, which puts it nicely in what I'd expect to be a linear range with no distortion or noise: the F4 is rated at 40Vpp... so that's 14.14Vrms ( 20/33/50 wpc into 8/6/4 ohms)."
Yes, and ....
"Indeed, many tube amplifiers have lots of gain... I think the lowest is around 10Vrms... modern ARC.... but CJ still drives 20Vrms. Single ended."
Yes, and ...
"Now my quest is to go bridged F4.. so I need a balanced preamp that will put drive 80Vpp... for 100/133/200 wpc into 4/6/8 phms. That means ~28.28Vrms from the preamp. Hence, 40Vrms from the preamp will nicely drive the bridged F4s with room to spare."
Yes, and ... I've repeatedly shown you that in another thread. I fail to see your point.
"That means a gain of 23db from the balanced preamp. Quite a bit more than your calculations."
Where did I calculate a gain? Please show me.
tonyEE,
Similar problem. I wish to bridge F4 Monos also. You are saying one needs Bal Pre's to accomplish this? Is that best case or will SE Iron suffice? I am not at the stage to calculate only fabricate.
Similar problem. I wish to bridge F4 Monos also. You are saying one needs Bal Pre's to accomplish this? Is that best case or will SE Iron suffice? I am not at the stage to calculate only fabricate.
I'm too a dullard in this conversation. I'll stick to the machinewerk and see how it plays out.
Your calculations are correct. However, you did state that you were happy with a 6db gain in the preamp... I just showed you why this is not necessarily the case when the amp has no gain and the preamp has to do all the voltage amplification.
That's all.
IAIMH was talking abot relation of preamp gain and it's clipping capability, taking in account normal source levels today; nothing about amps
you're introducing your own fixation, now solved, with need to drive F4
I already explained to you cheapest way of driving bridged F4, especially applicable now when you have CJ swinging 40Vpp at output; just put appropriate iron in between CJ and set of F4
again to both of you (so Man who's working with wood), of things ready on disposal - for driving bridged F4 - take Bal Ba3 FE
or wait zillion years - I have plans to revisit (and fully redo) my venerable Pumpkin; this time full shebang, servos, onboard regs, selector, 64step attenuator blahblah
but not soon, time is relative
Last edited: