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Challenge! Quick and dirty amp build - make a suggestion :)
Challenge! Quick and dirty amp build - make a suggestion :)
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Old 12th July 2016, 09:33 AM   #1
aspringv is offline aspringv  Australia
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Challenge! Quick and dirty amp build - make a suggestion :)
Default Challenge! Quick and dirty amp build - make a suggestion :)

Hi all,
So I just bought 50 tip31c transistors for not much. Who wants to suggest a build for em?
Constraints....
I'd like to build a stereo pair.
The heatsinks are pretty... ummm, ghetto. Photos to follow...
The tip31C are to be the only power transistors. Small bjt's and jfets are fine (assuming I have em)
Minimal adjustment! I'm doing this as a 'get over your finicky builds' exercise, so I'd like to just smash it out on a breadboard and away we go.
Be creative... LEDs? Go for it - I've thousands. Bulk paralleling? Sure, go nuts!
No power supply constraints - I've enough transfo's here to improvise my way up to most voltages...

I reckon I'd like to have a design by the Friday, and I could knock out a proto on the weekend...

So.... go for it!
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Old 12th July 2016, 10:15 AM   #2
vzaichenko is offline vzaichenko  Russian Federation
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Challenge! Quick and dirty amp build - make a suggestion :)
Quote:
Originally Posted by aspringv View Post
Hi all,
So I just bought 50 tip31c transistors for not much. Who wants to suggest a build for em?
Constraints....
I'd like to build a stereo pair.
The heatsinks are pretty... ummm, ghetto. Photos to follow...
The tip31C are to be the only power transistors. Small bjt's and jfets are fine (assuming I have em)
Minimal adjustment! I'm doing this as a 'get over your finicky builds' exercise, so I'd like to just smash it out on a breadboard and away we go.
Be creative... LEDs? Go for it - I've thousands. Bulk paralleling? Sure, go nuts!
No power supply constraints - I've enough transfo's here to improvise my way up to most voltages...

I reckon I'd like to have a design by the Friday, and I could knock out a proto on the weekend...

So.... go for it!
Hi Aspringv,

What output power do you have in mind?
What kind of speakers will you drive? What is their nominal impedance?

Cheers,
Valery
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Old 12th July 2016, 10:25 AM   #3
aspringv is offline aspringv  Australia
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Challenge! Quick and dirty amp build - make a suggestion :)
Default Theres a few choices...

Ok, I've a set of Clabby's (fullranger, tapped horn, 95dB, 8R) a set of TL6's from The Loudspeaker Kit (transmission line, MTM, 89.5dB sensitivity, 6R). Probably a build for the TL6's would be preferred, given I currently drive them with a home made Class D module from sure electronics...

Edit - Power output? No idea - happy to see what happens in all honesty!

Edit Edit - probably governed by the upper limit of supply caps I have on hand... 63V

Last edited by aspringv; 12th July 2016 at 10:35 AM.
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Old 12th July 2016, 10:40 AM   #4
Doug Kim is offline Doug Kim  South Korea
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How about trying JLH 1969 using paralleled TIP31C's?
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Old 12th July 2016, 10:41 AM   #5
aspringv is offline aspringv  Australia
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Challenge! Quick and dirty amp build - make a suggestion :)
Ghetto heatsinks (whisky for scale... and potentially inspiration). 300mm x 150mm. Ally extrusion as the fins...

It seemed like a good idea at the time...
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Old 12th July 2016, 10:42 AM   #6
sgrossklass is offline sgrossklass  Germany
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What do you have in stock in terms of TO-126 drivers and high-voltage transistors?

TIP31C are 4 amp jobs, so you'll want to parallel 2-3 pairs or so. Vceo is 100V, so unless cascoding, supplies should be ~+/-45 V max.

I'd go for something ESP P3A-ish (though maybe with the frontend upside down, i.e. pnp inputs and npn VAS). You only have to thermally couple drivers and bias spreader transistor when using a CFP output stage, which may come in handy. Dimension output resistors for some decent quiescent current in these rather slow outputs (expect <0.1 ohms), don't forget current sharing resistors in the emitter leads (0.1-ish ohms?).
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Old 12th July 2016, 10:49 AM   #7
aspringv is offline aspringv  Australia
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Challenge! Quick and dirty amp build - make a suggestion :)
to-126? BD139, BD140 is what I've on hand...

Both solid suggestions - I've most of a DOZ finished, so doing the JLH seems a waste...

ESP-P3A uses complimentary output BJT's... doesn't it?
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Old 12th July 2016, 10:54 AM   #8
aspringv is offline aspringv  Australia
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Challenge! Quick and dirty amp build - make a suggestion :)
Hmmmm, what about the attached... scaled down a bit and lots of paralleling of outputs.

Edit - credit to https://sites.google.com/site/quasis...series/nbip300 for the design. Those ghetto sinks would be in use if i was better at toner transfers...

Oh, and I've a stack of 0R15 5W resistors, so paralleling a pair is easy enough.
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File Type: pdf Nbip300schematic.pdf.pdf (42.1 KB, 13 views)

Last edited by aspringv; 12th July 2016 at 10:59 AM.
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Old 12th July 2016, 11:18 AM   #9
Ranchu32 is offline Ranchu32  Australia
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Looks like a reasonable start, although with those output devices you should limit the rails to about +/- 40V.

Left to right:
- C1 polyester or polypropylene film
- Match R5 & R10 as well as R4 and R9. Eliminate VR1
- Start conservative with Cdom - start with about 100pF.
- Select a better transistor type for the VAS (T6) if available
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Old 12th July 2016, 11:41 AM   #10
xrk971 is online now xrk971  United States
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Challenge! Quick and dirty amp build - make a suggestion :)
For your TL, the power from a pair of IRFP240/9240's with 35v rail would be perfectly adequate. However, since you say you have 63v caps, you can switch the BD139/140's to KSC3503/KSA1381 and power with 53v rails for 120w amp. It sounds fantastic for how simple of an amp it is. Those ghetto heatsinks are a great idea - would be perfect. It's such a simple amp - and can be built in a few hours. Several confirmed builds now and all reports are that it sounds great. Measurements of a speaker also look very good.

100W Ultimate Fidelity Amplifier

FH9 HV:
Click the image to open in full size.

Here it is driving dummy load at 120w:

Click the image to open in full size.

Here is the non HV version (BD139/140 drivers) with 35v rail supply. Sounds very good - deep powerful bass, smooth mids and clear non fatiguing highs.

Click the image to open in full size.

Last edited by xrk971; 12th July 2016 at 11:48 AM.
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