Amplifier Recommendation Requested

SRMcGee

Member
Paid Member
2004-05-23 10:59 pm
Wynnewood, PA, USA
Folks:

I'm looking for ideas for a new integrated amplifier for my parents. About 15 years ago I built them a simple LM3875-based integrated amplifier which they installed in my father's studio. My parents spend a lot of their time in that studio, which also serves as their reading room (he paints and they do a lot of reading) -- that amplifier is probably on at least 8 hours a day and they've derived a lot of pleasure from it. I'm considering building them a better-quality amp and would appreciate some suggestions.

My design criteria is:

1. The amp needs to be reasonably efficient. I've built a lot of Nelson Pass's designs and while I'm a big fan, big heat-generating Class A amps probably aren't the way to go for this project.

2. The amp has to be well-designed and not readily subject to over-heating. The amp will be on a small shelf with moderate air flow. Again, it will likely be on for extended periods of time.

3. It needs to sound at least as good as an LM3875 amp.

4. The speakers are 87 dB bookshelf loudspeakers. High volume will not be required.

5. Simpler is better (Mies van der Rohe was right, in my opinion).

Thank you in advance for the input.

Regards,
Scott
 
The easiest thing is to buy a used mixer to connect the two inputs as this $50 PV6 Peavey PV6 6-channel Compact Mixer 4 Microphone Preamplifiers 3-band EQulizer. | eBay
And a 160 W/ch PV4C PEAVEY PV-4C 250 Watts/Channel Proffesional Stereo Power Amplifier | eBay as this $170 one.
At those prices you may have to supply your own wall transformer for the mixer as the 16 vac 1 amp Triad at newark, or change the power supply rail caps, or maybe change out a volume pot. I paid $20 for my PV-4c for parts or repair, but I had to change rail caps + output transistors for about $80. Listening to it now using a TV tuner as source.
I reworked a $30 PV8 for parts or repair, putting new volume part in it, and finding the source of a dead output, a fractured via from top to bottom near the volume pot.
Next easiest is a honey badger from diyaudio store, plus a transformer bridge & filter caps, a box, a heat sink, a fan. A simple DPDT switch can work for the 2 inputs, then you need 4 RCA jacks in and 2 double binding terminals out. There wiill be machine work mounting components, use safety glasses with power tools. The cheapest source of all components, especially the box heat sink & the transformers is an amp for parts or repair from craigslist, ebay, flea market or pawn shop.
Lower in price but more complicated is a dual channel AX6 built on bare board, with 48 v or 50 v transformer, rectifier, filter caps, etc as above. Retro Amp 50W Single Supply Retro Amp 50W Single Supply - Page 22 - diyAudio
Mine puts out about 70 W/ch for 5 seconds at a time on a 70 v rail.
 
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Douglas:

Building. Two sources (FM tuner and CD player).

Well you're building so the inputs are pretty easy to arrange, so it's mostly about the amplifier itself... (If you were buying the input selection would be more important)

From my own interests I would suggest you take a look at some of the Class D modules and boards, there's bound to be one there that would box up nicely to make a good project and a nice amp for your parents.
 

SRMcGee

Member
Paid Member
2004-05-23 10:59 pm
Wynnewood, PA, USA
indianajo:

Yeah, but no. I want to build something nice for them, not cobble a bunch of eBay-sourced modules together. I'm thinking of something along the lines of a simple Class A/B amp, not too powerful (the Honey Badger would be overkill), maybe with a buffer and with a decent, open sound.

Douglas:

Yeah, maybe. When I last looked at Class D amps a few years ago, the general consensus was that the LM3875 was the best-sounding of the bunch. If true, then why bother building something new? If not, then there may be something out there worth considering.

Are there any simple 40-60 watt Class A/B amps for which pcbs are available?

Regards,
Scott
 

6L6

Moderator
Paid Member
2010-10-22 6:43 pm
Denver, Colorado
Scott,

Mark Johnson recently did a PCB for Bob Cordell’s LM3886 Super Gainclone. Neat circuit, and the 3886 can sound absolutely sublime when properly implemented. (Better than 3875 IMO) Contact me if you want a board set.

Bob also has a discrete design that I believe he is selling PCB for, he had a built board at BAF, but I dont remember details. Seemed quite interesting.
 
Apex FH9 is a wonderful sounding, easy to build simple amp. Many people have reported successful builds and also say that they love the sound. Class AB, 50w needs +/-35v PSU. Can be linear or a SMPS. I have spare PCBs I’ll send you for shipping cost - send me PM.

100W Ultimate Fidelity Amplifier

550058d1463590661-100w-ultimate-fidelity-amplifier-apex-fh9-png


557739d1467440491-100w-ultimate-fidelity-amplifier-image.jpeg


557904d1467529628-100w-ultimate-fidelity-amplifier-fh9-test-stereo-closeup-3.jpg


You’ll need a chassis, PSU, RCA jacks etc. but the amp itself is easy. No adjustments other than set bias current.

You can listen to sound clips from this amp here vs other amps.

Virtual Audition of Very Simple Quasi MOSFET Amp

The VSQ Quasi is also very good but more complex and harder to setup.
 
Yeah, maybe. When I last looked at Class D amps a few years ago, the general consensus was that the LM3875 was the best-sounding of the bunch. If true, then why bother building something new? If not, then there may be something out there worth considering.

At least have a look at the TPA3116 and TPA3255 boards. Things have progressed rather a lot in the last couple of years. Like distortion under a hundredth of a percent...
 
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Have a look at the ones at Neurochrome. Well engineered by tomchr who is a highly respected member here.
Neurochrome Audio: High performance DIY audio circuits.

The 3886DR (I've built one) is the simplest and goes on from there to more complex composite amps. I also have a LM3875 ala AudioSector / ChipAmp.com and Tom's are better.

Other than that, Rod Elliott (ESP) and Anthony Holton (Holton Precision Audio) have several.
 
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You already have a quality amplifier and I don't see how much more will be gained by a (slightly) better, if at all, amplifier. Your money would be better spent on a better pair of speakers using quality drivers. There are plenty of DIY designs with full plans. I built a two-way using SB Acoustics drivers and they were very good.
 

SRMcGee

Member
Paid Member
2004-05-23 10:59 pm
Wynnewood, PA, USA
You already have a quality amplifier and I don't see how much more will be gained by a (slightly) better, if at all, amplifier. Your money would be better spent on a better pair of speakers using quality drivers. There are plenty of DIY designs with full plans. I built a two-way using SB Acoustics drivers and they were very good.

Tromperie:

I don't disagree with your premise. In fact, I am also considering building my parents a new set of speakers. My perspective is that the LM3875 amp sounds good for what it is, but compared with the amps I've built for myself it unquestionably falls short. My parents are devoted music lovers and when they visit me they are enthralled by the quality of the sound my stereos produce. I'm better at this hobby than I was when their amp was built, and if I can raise the bar, why not?

Why do your parents need a new amp? Perhaps re-casing the 3875 is a better idea. Adding comfort features, bluetooth, remote, etc.

analog_sa:

I will admit that I take a little too much pride in the cosmetics and flexibility of my projects, but features aren't the issue here -- my parents don't need and likely would never use bluetooth or even a remote; they turn the stereo on in the morning and sometime late in the day turn it off. Music (mostly classical FM radio) plays continuously all day long in the studio. You're right to ask the question, but I think in this case my focus should be on higher quality sonics.

6L6, xrk971, mpmarino, rabbit and kokoriantz:

Thank you! Let me take a look; I may be in touch.

To all:

Thanks for the conversation. I love this community.

Regards,
Scott