Welcome to Solid State Guitar Amp Forum | DIY Guitar Amplifiers. Please login or sign up.

July 15, 2024, 07:52:23 AM

Login with username, password and session length

Recent Posts

 

Recent posts

#1
Honey Amp / Re: Transformer Question
Last post by RookieRecurve - July 09, 2024, 10:23:24 AM
I was under the impression that a full-bridge rectifier would drop the voltage?  I guess too much voltage is better than too little as it should be easier to drop it than to increase it.
#2
Honey Amp / Re: Transformer Question
Last post by Loudthud - July 09, 2024, 02:21:03 AM
After rectification and a filter cap, the output will be close to 24VDC. To get 16VDC, you will need some kind of Voltage regulator.
#3
Honey Amp / Transformer Question
Last post by RookieRecurve - July 08, 2024, 07:30:48 PM
Hi all, I got my kit last week, and was looking at options for powering the amp, and discovered I have a power transformer from an old Dell powered-speaker set.  It outputs 17v AC and 2.5A.  I have a full-bridge DIY rectifier kit on its way to convert it to DC.  I am not sure what the final DC voltage will be, but I am hoping for 16 VDC.  I cut open some shrink wrap on the power supply, and found a 0.1uf 275VAC capacitor in there.  Any ideas what this is for?  It appears to be wired in parallel?  Any thoughts on my proposed power supply?  I figure it's free, and it's great for learning more.
#4
Amplifier Discussion / Re: Bipolar PSU PA + single PS...
Last post by Miyagi_83 - July 08, 2024, 12:28:29 PM
Thanks, g1 (pentode control grid?  ;) )
I'll measure the preamp's current draw and see how much or how little it is.
Have a good one.
#5
Amplifier Discussion / Re: Bipolar PSU PA + single PS...
Last post by g1 - July 08, 2024, 11:54:03 AM
Probably won't matter, depending how small the current is.
If you are really concerned, you could just put a resistor across the negative rail to draw a little current and balance it out.
#6
Schematics and Layouts / Re: Keelhauler MKII - a reason...
Last post by Miyagi_83 - July 08, 2024, 09:53:08 AM
@Umlaut
Hi, in practice, what's the maximum signal amplitude coming from that GIVE stage? Is there a limit?
Best regards,
M.
#7
Amplifier Discussion / Bipolar PSU PA + single PSU pr...
Last post by Miyagi_83 - July 08, 2024, 06:28:29 AM
Greetings, oh, collective wisdom.
I've got this solid-state guitar amp from the 1980s. It's operational, or at least it was last time I checked, but it's not quite the kind of tone I like. So, a thought of modifying it popped into my mind.

I was thinking of leaving the power section alone and changing the preamp to the one inspired by Joe Davisson's designs switchable to something else. It's not decided yet.

The amp as it is now uses a bipolar power supply and the preamp I was considering runs on a single PSU.
I'm wondering if it's not going to upset the power amp's PSU rail balance due to the extra current draw, which compared to the PA section is minuscule, I know, but it's still there.
Am I being paranoid here?
#8
Amplifier Discussion / Re: Transistor power amp compo...
Last post by Miyagi_83 - July 07, 2024, 04:32:14 PM
¡Muchas gracias, Señor Fahey!  :)
That definitely makes life easier, doesn't it? This info will come in handy one day, once I feel I'm ready to design and build my first high power transistor amplifier. I'm not going to rush it, though 😅
#9
Schematics and Layouts / Re: Keelhauler MKII - a reason...
Last post by J M Fahey - July 07, 2024, 08:42:14 AM
Looks VERY good in general.
Specially the third screen capture which shows a waveform with a kink near zero crossing plus rounded tops, quite close to a Pentode push pull clipping, the expected "tube power amp clipping". 👍🏻
#10
Amplifier Discussion / Re: Transistor power amp compo...
Last post by J M Fahey - July 07, 2024, 01:00:11 AM
Agree.
No power transistors in parallel here, you only have single Q8 on positive rail and Q11 on the negative one, so nothing to match.

Now in higher power amps where you have multiple transistors in parallel, as in Gibson G105 (or something like that) being discussed in another thread, where they use parallel 2N6254, yes, there you need it.

That said, modern transistors are *so* consistent that if same brand and type and from same batch (say you order 4 or 8 together from Mouser - Digikey - etc.) they *will* be very close, by default.

I often buy power transistors in bulk, say 20-25 units in a "stick".
Used to measure all and attach small labels to each ... not any more, incredibly consistent.

Only justified if, say, one transistor is made by, say, Fairchild and the other by ST or ON, or one was bought in 2014 and another in 2023 or some similar separated vintage.

Even so, low value emitter/ballast resistors (0.1  0.22  0.33 ohm) tend to even out current very well.