Amplifier pairing with APT Holman

[Medsca]

I have purchased a APT Holman pre-amp at a yard sale this weekend.
I’m contemplating sending it along to Vince@ audioproz for the upgrades. The only issue is the tape buttons are sticking. I am also looking to see if anyone located near Baltimore, MD can complete the same service.
The reason for my post is to get some recommendations for a power Amp to pair with the APT Holman pre-amp. I have 500-750 budgeted for the AMP. Lower cost is always appreciated.
I presently have a NAD 114 pre-amp and a Adcom 5400 Amp that sends the music to Kef q150’s
I’m sure I might have to upgrade speakers as well.
Thank you all in advance for the consideration.

 

[mhardy6647]

1) APT also made a power amp. (just sayin')
2) I have no idea if they'd offer any help with rehab of a vintage APT preamp, but Soundscape on Cold Spring Lane in B-more sold 'em when they were new... IMO it wouldn't hurt to ask.

 

[Medsca]

Thank you very much for your response. Yes, the Holman amp 1 is special. Way way over budget.
I will give soundscape a call tomorrow to check in if they work on these.

 

[Mark185]

@Medsca , I am curious. If a used Apt Holman 1 amplifier is way way over budget, what is your budget including any service that may be required? I see these amps come up for sale on Ebay from time to time in the $400-600 price range depending on condition. A refurbishment by one of the recognized experts is another $600 so total outlay is probably in the $1000-1200 range. I have owned one of these amps for > 30 years and have no intention of selling it. I am always on the lookout for a used one in decent condition for a bargain price.

If $1000 is way way over budget, I am thinking you should look at something like the 3E Audio A7 which can be found for ~$250 on Amazon on sale. I bought one to use with my Apt Holman preamp while I contemplate replacing capacitors in my Apt amplifier myself or sending it out to Peter Williams at Quirk Audio. He is one of two recognized experts I am aware of. The other is Vince in the Boston area but he is a bit much to deal with when talking about doing the work. His expertise is unquestioned. He used to work at Apt and his rebuild service is probably worth the price. I just found Peter to be an easier personality to deal with and he also does excellent work for about the same money as Vince.

I am suggesting the 3E amplifier because just about any vintage amp available for < $500 is likely to need capacitors replaced and if you can't do the work yourself, the cost approaches $1000 anyway. I say this as an owner of the Apt Holman amp, Adcom 5500, and Hafler XL480. All are excellent vintage amps that I have owned for a long time.

 

[rdenney]

I have purchased a APT Holman pre-amp at a yard sale this weekend.
I’m contemplating sending it along to Vince@ audioproz for the upgrades. The only issue is the tape buttons are sticking. I am also looking to see if anyone located near Baltimore, MD can complete the same service.
The reason for my post is to get some recommendations for a power Amp to pair with the APT Holman pre-amp. I have 500-750 budgeted for the AMP. Lower cost is always appreciated.
I presently have a NAD 114 pre-amp and a Adcom 5400 Amp that sends the music to Kef q150’s
I’m sure I might have to upgrade speakers as well.
Thank you all in advance for the consideration.

I'm just going to answer the question.

I'm using a Buckeye NC502MP amp with mine. In your price range, excellent performance, abundant (I mean abundant) power, and enough gain for the Holman to easily drive it to full power without any chance of distortion.

The Holman preamp has a SINAD of about 90 dB, so it won't hold a good amp back.

Rick "it will work great with your Adcom, too" Denney

 

[Medsca]

@Medsca , I am curious. If a used Apt Holman 1 amplifier is way way over budget, what is your budget including any service that may be required? I see these amps come up for sale on Ebay from time to time in the $400-600 price range depending on condition. A refurbishment by one of the recognized experts is another $600 so total outlay is probably in the $1000-1200 range. I have owned one of these amps for > 30 years and have no intention of selling it. I am always on the lookout for a used one in decent condition for a bargain price.

If $1000 is way way over budget, I am thinking you should look at something like the 3E Audio A7 which can be found for ~$250 on Amazon on sale. I bought one to use with my Apt Holman preamp while I contemplate replacing capacitors in my Apt amplifier myself or sending it out to Peter Williams at Quirk Audio. He is one of two recognized experts I am aware of. The other is Vince in the Boston area but he is a bit much to deal with when talking about doing the work. His expertise is unquestioned. He used to work at Apt and his rebuild service is probably worth the price. I just found Peter to be an easier personality to deal with and he also does excellent work for about the same money as Vince.

I am suggesting the 3E amplifier because just about any vintage amp available for < $500 is likely to need capacitors replaced and if you can't do the work yourself, the cost approaches $1000 anyway. I say this as an owner of the Apt Holman amp, Adcom GFA5500, and Hafler XL480. All are excellent vintage amps that I have owned for a long time.

Thank so much for your support and reply. I will be sending Vince ( impressive backstory and intelligence) the Apt Holman preamp for tier 3 upgrade. I was also able to source a Hafler DH 200 from a neighborhood yard sale for an excellent price. I will be sending that unit in to him as well.
Now, I need to upgrade my speakers with ADS, Paradyms, KLH5’s, or PBS monitors.
That means I will be selling a fully serviced ($500) Adcom 5400, NAD 114, and one year old Kef Q150’s.

 

[rdenney]

Thank so much for your support and reply. I will be sending Vince ( impressive backstory and intelligence) the Apt Holman preamp for tier 3 upgrade. I was also able to source a Hafler DH 200 from a neighborhood yard sale for an excellent price. I will be sending that unit in to him as well.
Now, I need to upgrade my speakers with ADS, Paradyms, KLH5’s, or PBS monitors.
That means I will be selling a fully serviced ($500) Adcom 5400, NAD 114, and one year old Kef Q150’s.

I would suggest that you won't get much improvement from replacing the op-amps in the Holman. My Holman measured very similarly to the one that Amir tested that had received the complete treatment, and all I did was replace the electrolytic capacitors with good-quality replacements of the same capacitance and greater temperature ratings.

That might save you some money.

I would also submit that the vintage speakers on your list might not measure as well, and may well require significant servicing, compared to more recent designs. I moved from Advent loudseakers to Revel Concerta F12 towers, a pair of which I bought used for well under a kilobuck. They are better in every way, notwithstanding my unwavering love of the old Advents.

Rick "https://www.audiosciencereview.com/...an-preamp-using-vintage-test-equipment.63473/" Denney

 

[Mark185]

As Amir has demonstrated, rolling op amps has very little measurable effect and I think this applies equally to vintage and new equipment. Tom Holman is one of the preeminent audio engineers of his generation. If he thought the Texas Instruments TL072 was good enough, who are we to mess with that? It is not remotely close to state of the art op amps today but it is still in use in many applications. Part of the picture is a circuit has to be designed to take advantage of an op amp's characteristics. Simply pulling one and popping another in does not accomplish that.

FWIW, I am a EE but my education about analog devices is decades old. Memory tells me that when the TL072 was introduced, it was somewhat special because it used a JFET input with very high input impedance and decent noise characteristics. All the more reason not to mess with replacing them unless you know the replacement has similar input impedance and gain characteristics.

 

[Medsca]

I would suggest that you won't get much improvement from replacing the op-amps in the Holman. My Holman measured very similarly to the one that Amir tested that had received the complete treatment, and all I did was replace the electrolytic capacitors with good-quality replacements of the same capacitance and greater temperature ratings.

That might save you some money.

I would also submit that the vintage speakers on your list might not measure as well, and may well require significant servicing, compared to more recent designs. I moved from Advent loudseakers to Revel Concerta F12 towers, a pair of which I bought used for well under a kilobuck. They are better in every way, notwithstanding my unwavering love of the old Advents.

Rick "https://www.audiosciencereview.com/...an-preamp-using-vintage-test-equipment.63473/" Denney

I have an offer in to purchase a set of the Revel Concerta f12 for 400$. Is that a good price?

 

[rdenney]

I have an offer in to purchase a set of the Revel Concerta f12 for 400$. Is that a good price?

Yes, that is an excellent price if they are in a state of good repair. Replacing faulty drivers won't be easy, so make sure they work. Knowing where you are, I think I know the speakers you have made an offer on, and I've pondered buying them myself to use on a second system and to have as a backup.

Here are measurements in the Canadian NRC anechoic chamber. They didn't do a spinorama, but they did provide the necessary measurements to understand directivity and dynamic capability. (Which are very good, by the way.) https://www.soundstagenetwork.com/measurements/revel_concerta_f12/

And here is Kal's positive review (and JA's measurements, which are equally positive): https://www.stereophile.com/content/revel-concerta-f12-loudspeaker

Rick "many other positive subjective reviews from the day, for whatever that s worth" Denney

 

[Medsca]

Thanks. I have been reading and researching Revel F12 all evening. I think they will fit quite nicely with the Apt Holman pre-amp and the Hafler DH200 power amp. Bi-wire or not to bi-wire is the next dichotomy?
Negotiated another round. The seller and I agreed on $325.00 for the pair.

 

[rdenney]

Thanks. I have been reading and researching Revel F12 all evening. I think they will fit quite nicely with the Apt Holman pre-amp and the Hafler DH200 power amp. Bi-wire or not to bi-wire is the next dichotomy?
Negotiated another round. The seller and I agreed on $325.00 for the pair.

No need to biwire--the crossover is inside the speaker and downstream from the connections, so biwiring saves nothing. Leave the shorting bars in place and run one set of wires.

That is an excellent price for very good speakers.

Rick "paid twice that and still got a good deal" Denney

 

[DWPress]

I had one of those! I had mine mostly paired with some NAD 2200's but it was great with any amp I used it with. It's the features that make the preamp special, not the sound.

 

[Medsca]

No need to biwire--the crossover is inside the speaker and downstream from the connections, so biwiring saves nothing. Leave the shorting bars in place and run one set of wires.

That is an excellent price for very good speakers.

Rick "paid twice that and still got a good deal" Denney

Okay picked up ( heavy buggers) the speakers any PEQ you would recommend?

 

[antcollinet]

Okay picked up ( heavy buggers) the speakers any PEQ you would recommend?

PEQ needs to be based on in room measurements, to account for room modes.

 

[rdenney]

Just wire ‘em up and enjoy them. The next step is a big one, involving a calibrated measurement microphone and Room Equalization Wizard (REW) running on a laptop wired into the system. But they will sound as good as your room allows without that.

Rick “enjoyed them straight out of the box” Denney

 

[Mark185]

I second the recommendation for REW and a calibrated microphone. Mini DSP makes the Umik 1 which is a USB microphone and the lowest priced quality measuring microphone I am aware of. There are XLR microphones on the market but then you need an audio interface box which will add at least another $100 to your purchase for a low end interface. You don't really need an XLR mic unless you are designing speakers and need to measure time of arrival for woofer, mid, tweeter, etc. USB mic is fine for room equalization.

@rdenney may know differently but the only moderately priced parametric equalizers I am aware of are the ones made by Mini DSP. I own their C-DSP 8x12 which is primarily designed for mobile audio but it can work well in a home system too. They make one more suited to a home system that actually costs less. It is the:

miniDSP Flex Unbalanced RCA 2x4 Digital Signal Processor

miniDSP Flex Unbalanced RCA 2x4 Digital Signal ProcessorThe front panel features an OLED display and a user-friendly volume control/encoder knob, ensuring effortless management. True to miniDSP's tradition, the Flex series is packed with proven audio processing functionalities, including...

www.parts-express.com

My goodness, prices on these things have gone way up with tariffs. I paid $700 for the C-DSP 8x12 and now it is $999.98. I bought mine in March 2025. In 2024 this was just $550 so prices have nearly doubled in less than a year thanks to tariffs. The same goes for the DSP-Flex. That was $650 just a few months ago, Even at these elevated prices, I don't know that there are other alternatives for sale for less. Part of the equation is the software support. Mini DSP software is mature and works well.

Another way to approach PEQ is to buy something like the WiiM Ultra Streamer preamp. It has PEQ software and works surprisingly well. I have one in my TV room feeding an Aux input on my Apt Holman preamp. It lets you start experimenting with PEQ for a much lower financial investment. There are also computer based PEQ programs that can get the job done but the initial learning curve is a bit higher and you need a decent quality audio interface box to do that.

One other way to approach this is buy a used automotive DSP on Ebay and get a low noise linear regulated 12 volt power supply. Arc Audio is based in the USA and makes some very good DSPs with excellent sottware and excellent customer service if you have questions. FWIW, I own a Wiim Ultra, mini DSP C-DSP 8x12, and DSP amplifiers from Arc Audio and Audiotek Fischer. All are well designed and have excellent software. The WiiM is probably the least capable but it is a very good value for $329.

​

 

[Mark185]

I forgot there is another relatively low cost entry to PEQ. The Dayton Audio DSP 408. I actually started out with one of these and it was fun and useful for learning how to apply PEQ. If I remember correctly, the analog input will overload at about 1.6 volts and distortion goes up rapidly beyond that. The output stage goes into heavy distortion around 2.2-2.5 volts which is not too bad for home audio. With this device, you have to maintain awareness of its overload voltages and not employ too much boost. It teaches you to cut boost whenever possible to achieve the desired frequency response. The software is basic but it does everything you will need as a begineer. It also has a smartphone app.

Dayton Audio DSP-408 4x8 DSP Digital Signal Processor for Home and Car Audio

Dayton Audio DSP-408 4x8 DSP Digital Signal Processor for Home and Car AudioTake Control of Your Sound Ease of use has always had its place in the consumer electronics industry. Dayton Audio has now brought to market a digital signal processor (DSP) that combines versatility, incredible sound...

www.parts-express.com

 

[rdenney]

A Yamaha YDP2006 is an effective digital parametric equalizer that will work fine if you don’t have to have computer integration. (You don’t.) These go for a hundred or a bit more, but you’ll probably need to clean the optical encoder (DeOxit works). They are intended for pro sound and have balanced ins and outs, though common adapters work fine. They are switchable for high or low level inputs, and also have an overall gain control. I’d take one of these over most cheapie equivalents that still cost more new.

A Dayton UMM-6 USB measurement microphone will work straight into a laptop’s USB port for running REW. Wire the computer’s audio line out to an unused input of the preamp for testing—it’s more than good enough for this purpose. $95 at Parts Express.

It is possible to do this at near the state of the art for not much money for those with a screwdriver and a can of DeOxit.

Rick “not chasing pennies with dollars” Denney

 

[Mark185]

@rdenney the Yamaha YDP2006 is pretty cool if it can be found for $100 or so. I never knew this existed. Unfortunately I have already 'chased pennies with dollars' more than once with audio equipment and cars. . It is part of my addiction and at 68 years old, I feel I have earned the right to toss logic out occasionally in favor of fun and tinkering. I looked up the YDP2006 and found a great review from 10 years ago.

Review: Yamaha's YDP2006 Digital Parametric Equalizer

Yamaha’s Stunning YDP2006 Digital Parametric Equalizer Back in the summer of 2007, I was ready to call it quits after a year-and-a-half with the ubiquitous Behringer DSP1124 Feedback Destroyer I was using to equalize my subwoofers. It had always been a love/hate relationship with the BFD...

www.whatsbestforum.com

The only thing that would give me pause regarding this equalizer is that it is a constant Q design. To be sure, constant Q was state of the art back then and vastly superior to equalizers that had variable Q that was not under control of the user. The noise and distortion measurements for the Yamaha are much better than something like the Dayton DSP 408. With all but one of the mini DSP products all in the $1000 price range, I would buy the Yamaha you recommend in a heartbeat if just using it for subwoofer duty like the author of the test review linked above.

I will add that the software capabilities of the Arc Audio and Audiotek Fischer mobile audio DSP units is head and shoulders above anything else in the consumer market but I also recognize that a considerable cost is involved to go down that route. They are great fun for an addicted tweaker like me and I use them in my cars and in one of my listening rooms at home. The software is free. The hardware is expensive unless you find a good deal on used equipment on Ebay.

A quick look this morning shows a Helix DSP Mini MK II for $499. If I did not already own several DSP units, I would be very tempted to buy this. If you or @Medsca are curious about why I am so high on this product, download the free software and run it in demo mode.

Download - DSP PC-Tool 6 software from Audiotec Fischer

DSP PC-Tool 6 Software from Audiotec Fischer | Equalizer | Time alignment | channel-assignment | real-time analyzer | multilingual

www.audiotec-fischer.de

Arc Audio software is just as good and their hardware is excellent. I will add that both the Arc Audio and Helix products have differential inputs despite using RCA jacks so an XLR adapter will allow pro level inputs that are fully isolated from ground. They also have optical and coaxial SPDIF inputs with excellent ADC circuits.

Summing up. The Yamaha is a great recommendation for the money and I appreciate you pointing that out. For someone like me, spending more to get really good computer integration is worth it but I recognize that is not for everybody.