Apt Holman Preamplifier Review (vintage Audio)

[EJ3]

No, it does not even meet the requirements set forward by the main consumer media in 1979 - that of the phonograph record. The overload margin of phono input above 5 kHz - where almost ALL of the action is ( due to the RIAA curve ) - is way too low . Too low even for normal better recorded musical material, let alone for ticks/pops - not to mention an occasional scratch that is sadly unavoidable in records. It is the typical limitation for the circuits operating with standard +'- 15 V DC power supply rails using op amps.

The review itself is good, but clearly displays that the reviewer is not at home with phono gear. There is no mention of the phono input gain adjustment that can be set for each channel independently ( to cater for the compensation of phono cartridge output voltage imbalance - allowing for the correct balance rec out levels ) - which has been unheard of at the time. Nor is there any mention of the circuit having - as one of the first if not actually the first to do so - a buffer stage at the input that isolates further circuitry from the interaction with phono cartridge inductance, an old and known problem affecting RIAA accuracy when using real world source and not lab measurement gear.

This preamp is a large collection of TL071 ( family.... ) opamps. Therefore nowadays it can be considerably improved by the use of direct replacement modern version of this op amp - TLE2071 ( family ). Lower noise, lower distortion, triple slew rate ... - it yields both measurable and audible improvement.

There are many things that we have learned from this iteration of my pair of APT/Holman Preamps. The overload margin as it is does not meet original spec, the opamps are an idea that we have been thinking about (we have been unsure of which ones to use). But I am pretty sure that the TLE2071's will happen in my next collaboration with Peter Williams at Quirk Audio, as he is willing to make more changes & adjustments than some others. These Preamps are, for me, a constant work in progress. At the next update, a few years hence, these and other things that we have found through this generous allowing of the testing of my units by Amir, will be addressed. It is my intent to keep the original circuitry design and take it as far as I can with the best of what is available that I can afford to have done. Therefore, every few years, there will be updates to these Preamps, based on the science of the issues that we have found. Thank you so much Amir for allowing me to have this reviewed.

 

[SirPaulGerman]

Is the DBX-CX-3 Preamp very close or the same as the CX-1 ?

 

[rdenney]

Is the DBX-CX-3 Preamp very close or the same as the CX-1 ?

My understanding is that it is not.

Rick “but they are cheaper and more plentiful” Denney

 

[SirPaulGerman]

My understanding is that it is not.

Rick “but they are cheaper and more plentiful” Denney

Do you recommend another preamp at the same level of the DBX CX-1?
I already have a Audiolab 8000c preamp, but I am not sure how good it is.

 

[anmpr1]

My first "really good" (???) speakers were a pair of JansZen Z412HP hybrid electrostatics that I bought from a friend down the hall in the dorm. He owned the original Quad ESLs

The shop where I bought most of my gear had a huge grand re-opening when all that was done, and the guys who founded DCM were there along with Andy Rappaport, who put out several preamp and power amps for a few years. Pretty sure that the shop sold Audionics and Hafler electronics at some point.

However, when it comes to the other speakers that were popular then that friends owned or I was able to audition at length, I am kind of drawing a blank. I recall Fried...

Interesting names--a regular blast from the past of 'high end. It was wild and wooly back then, for sure!

Fried loudspeakers were the creation of Irving Fried, who ran an audio storefront in Philadelphia. He was the first importer of the Quad electrostatic loudspeaker in the US. I guess that was back in the early '60s. In importance, Irv was more a 'legend in his own mind' than Peter Walker, who was a bona fide legend in his own time. Fried once told Gordon Holt that he was at least partly responsible for the designs of the Klipschorn and the AR acoustic suspension loudspeaker. Both Paul Klipsch and Roy Allison (who was then chief engineer at AR) wrote to Holt telling him they had no idea what Fried was talking about. For his part, Paul admitted that he 'knew about' Fried from an article the latter had written in the '50s, but by that time the Klipschorn design was essentially finished, having been completed in the mid '40s. As far as I know, Gordon never called Fried out over his claims.

Andy Rappaport was (in)famous for his 'looked like they were made in my basement' class-A biased electronics, that ran as hot as a matchstick, and had (some claimed) at least a 100% failure rate. But when service was required, his company was belly-up, and that was that. I heard Andy attempted make a comeback with a company called Octave Research-- more class A stuff. But by then it was pretty much over for him. Last I heard he went into investment banking--a vocation benefitting mankind at least as much as his amplifiers did.

Audionics was, to my mind, legitimate, having one foot in the pro studio scene. I believe they were bought up by Rockford, but Rockford always seemed to be more interested in the car audio business than hi-fi. Rockford also owned Hafler and Acoustat, but did nothing important with them.

 

[Digital Mastering System]

Thanks. See my response to your earlier post. One of the tests I introduced proved the test of time and is in the IEC standard. The pre-emphasized square wave test made signals much faster than poor little stylii could go so was wrong. However we were trying to find out why things sounded different and came up with two tests for which one was and one wasn't true. Not too bad a track record working at the fringe, and "but in the end is all came to nothing" is clearly wrong.

Mr. Holman: SO nice to see you here at ASR. I have one question for you as I was scanning the preamp's schematic: Why is there an opamp hooked up as a negative resistor on the output? Looks like it compensates for the feedback network loading, freeing up the main opamp to supply the output load. If I change the opamps to OPA1656 (or OPA2156 depending on input CM range), can I safely leave off this negative resistor? The new OPAXX56 family have 100ma outputs so don't really need the current help.
I have a old preamp which I am recapping and chip rolling - It also has a bad phono input FET - I intend to replace that input FET with a LSK170. A good idea?

 

[anmpr1]

Thanks. See my response to your earlier post. One of the tests I introduced proved the test of time and is in the IEC standard. The pre-emphasized square wave test made signals much faster than poor little stylii could go so was wrong. However we were trying to find out why things sounded different and came up with two tests for which one was and one wasn't true. Not too bad a track record working at the fringe, and "but in the end is all came to nothing" is clearly wrong.

Just to clarify my point if I did not explain it well (which I might not have done). I was writing in the context of reviewers looking for an objective rule they could use to identify what they perceived as certain sound differences within preamps. That is to say, in spite of the new tests promulgated at the time, reviewers found no reliable correlation between how a preamp managed the test in question, and the subsequent 'sound' of the preamp, from a subjective standpoint. I certainly did not mean to imply that your research on phono preamp stages (in order to identify what is going on in the RIAA circuit under dynamic conditions) was somehow not worthwhile.

To recap, in 1977, in the first issue of Audio Critic, Peter Aczel stated that he was looking for some kind of correlation between (phono) preamp measurements and how they sounded to him, and his listening panel. He then cited some of the newer tests that could be used for evaluating phono stages objectively, including yours, Matti Otala's, Wayne Hetrich's, Andy Rappaport's et al. Next, he ran down a dozen or so preamplifiers, more or less ranking them as to their 'sound'. He measured them using some of the tests. Then (...maybe it was an issue or two later) he indicated that none of the tests had any correlation to how the preamps sounded. That is what I meant by writing "...it all came to nothing."

Some years later, Peter told me that the truth of the matter was that the Dynaco probably sounded the same as the JC-2, all along, but he didn't match levels, so he no doubt fooled himself. It was as simple as that. But, then again, none of us, his readers, were on the ball, and none of us took Mark Davis seriously. To our detriment.

 

[EJ3]

The service manual is just a joy isn't it?

A breath of fresh air from the past.

 

[A Little R&R]

Conclusions
The owner who sent me this has a knack for finding these past jewels with excellent engineering. Their performance post refurbishing is extreme good even by today's standard which sadly has sled backward. Hopefully no one sheds a tear next time I complain about an audio product producing SINAD of 70 dB and such which this level of performance was achieved years ago.

I am happy to recommend the Apt Holman preamplifier. I see one on ebay for $550 although it will likely need thorough service like the sample I tested.

Sweet. Thanks Amir.

I bought one of these off eBay about 15 months ago for $290, and then spent another $380 for level three "audiophile-grade" service (the works) from Audio Proz, a Boston-area company headed by a guy called Vince who was a technician at Holman back in the day. This means:

"The price includes the matching of channel parts (FET’s, op amps, etc.) for noise and performance, as well as some “esoteric” modifications. The modifications are done to satisfy those “golden ear” types who may possibly hear the subtle difference of some very critical capacitors in the audio path (e.g., there are a few stages that can benefit from capacitor bypassing with high quality Mylar capacitors, improvement of subsonic filter for advanced wider frequency response, less phase shift, etc.). Admittedly, I don’t think the sonic improvements are immediately obvious and dramatic (unless the unit had major off-spec or failed parts), but it is true that listeners who do own high quality, reasonably phase correct speakers playing quality, acoustic-oriented program material will hear an improvement. Let me stress my opinion (which is based on factual A/B blind testing and reinforced by AES Journal testing competitions) that the subtle differences of improved spatial/depth or instrument timbre clarity are mostly perceived due to the quality of the speakers and their appropriate listening position. But moreover, the level 3 mod will probably extend the life of the product by many years."

AudioProz : Full Article Details

Audioproz, located in Watertown Massachusetts, in the Boston area, has been in the audio business for 25 years. We specialize in professional audio, and hi-fi audio sales, repair, service, upgrades, and modification. The owner, Vince Naeve has worked for companies such as APT, H.H. Scott, and...

www.audioproz.com

No regrets. I love the simple classic look and the excellent sound of this component. Delighted that ASR is giving the Holman Apt some lovin'!

 

[Thermionics]

I lucked out about 4-5 years back and picked up a VG condition APT Holman preamp locally for about $100 if memory serves. The only work I've put into the preamp is to replace the relay which had finally given up the ghost, otherwise, it is as it left the factory. I've thought about recapping the preamp, but I'm a bit nervous about inadvertently reducing the (already excellent) performance. At the very least, I ought to dig in and replace the power supply caps simply because they're pushing 40 years.

Thank you, @Tomlinson Holman, for building such a wonderful preamp.

 

[Tom Prowda]

I had one of these units in my hifi system from 1976 though most of the 1980's. Great performance and sound, very nicely made, super reliable, unlike the Dayton Wright SPS unit it replaced. The tone controls actually worked! It was paired with Holman's Amp 1, another well made great sounding very reasonably priced piece of gear. My only complaint about the amp was that I always wished it had been 200 watts/channel to better work with a set of somewhat insensitive Gale GS-401 speakers.

 

[pseudoid]

Chassis construction (likely way safer in an accident than anything bought from a car factory):

I don't mean to disagree with that gorgeous labor-of-love but 'crash-worthiness' is not about the most rigid frame but one that will absorb the g-shocks involved during a frontal (or side or rear) impact without exposing the occupants to those g-forces occupying the cage.

 

[EJ3]

I don't mean to disagree with that gorgeous labor-of-love but 'crash-worthiness' is not about the most rigid frame but one that will absorb the g-shocks involved during a frontal (or side or rear) impact without exposing the occupants to those g-forces occupying the cage.

That is exactly what that frame is designed to do. Absorb & disperse over as much of it as possible, exposing the occupants to the least G-Forces possible.
If you look into modern automotive chassis design, today TORSIONAL RIGIDITY has been increasing drastically. Because the more torsional rigidity the chassis is, the better control the springs, shocks, anti-sway bars & tires have. Look at any modern car, they are using high strength steels to get this with a unibody construction.
This construction is body on chassis and is stonger where it needs to be and more flexible where it needs to be.

These cars/trucks are, by law, a low volume production vehicle that can be bought to spec or built yourself.
There is even a college program to build them at Mott College in Flint, Michigan:
A hands-on, three day workshop where students build a Factory Five Mk4 Roadster, ‘33 Hot Rod, or 818S Sports Car from the bare frame all the way up to the completed car in three days! Since 2002, the Build School has graduated over 2,000 students from the U.S. and all over the world. (notice the low number of graduates building these vehicles, they are not something that you see every day. But they are properly engineered [and way better than the original vehicles that they are based on]). Classes are held at the brand-new MCC Livingston Center in Flint, Michigan.
Mott College Instructors are certified automotive mechanics.

 

[anmpr1]

I had one of these units in my hifi system from 1976 though most of the 1980's. Great performance and sound, very nicely made, super reliable, unlike the Dayton Wright SPS unit it replaced. The tone controls actually worked! It was paired with Holman's Amp 1, another well made great sounding very reasonably priced piece of gear. My only complaint about the amp was that I always wished it had been 200 watts/channel to better work with a set of somewhat insensitive Gale GS-401 speakers.

The good thing about audio is that it can be a two way street, so no one is to blame. Thus, you could say:

My only complaint about the Gale was that it wasn't more sensitive and efficient, so that would have worked better with my Amp 1!

I recall Gale products. I hadn't thought about them in a long time. The local Yamaha dealer had the franchise (back then, Yamaha was considered exclusive, and several cuts above Pioneer, Kenwood, Sansui et al). Featuring Gale's chrome encased speakers set up on his special stands, using Yamaha's new FET amp and their preamp--the one with about fifty knobs, switches, buttons and meters on the front panel. And this cool Yamaha designer cassette deck, shaped like a wedge.

The system's front end was Ira's lucite frame direct drive servo turntable (designed with his schoolmate, Sao Win). I don't recall the tonearm/cartridge. All I remember is how the 'total package' was really expensive, and the dealer got nervous when anyone approached it.

 

[Tomlinson Holman]

This is a review and detailed measurements of the Apt Holman vintage preamplifier. It is on kind loan from a member and has been refurbished by QuirkAudio.

The look is a cross between hifi and pro gear:

View attachment 167044

Other than some scratches on top, the unit is a very good cosmetic shape. Rear connections are extensive:

View attachment 167045

Yes, there was a time we had outlets in the back of stereos. The more there was, the higher end the gear was said to be! Wonder what led to their demise.

In case you are wondering as I did when I was first contacted about this unit, Holman is Tomlinson Holman or the T in THX (now works for Apple). Owner sent me the service manual which is not only extensive but has excellent tutorials on the design, instruments to test it with, and pages and pages of detail. It is incredible what used to be available compared to now.

Apt Holman Measurements
Let's start with our dashboard input. I selected Tape 1 as input but oddly front panel selector doesn't have Tape 1. I set it to Aux 1 and then pushed Tape 1 switch:

View attachment 167047

Wow, this is excellent! I expected SINAD in 60s or 70s and here we have 90 dB. It is dominated by second harmonic at that level. Even more impressive is the signal to noise ratio with same unity gain:
View attachment 167048

Frequency response was dead flat in audible band:
View attachment 167049

Crosstalk is better than many devices I test today:

View attachment 167050

There is essentially no frequency dependency in distortion+noise:

View attachment 167051

Output level is optimized for about 0.4 volts or so:
View attachment 167052

So you may want to pair it with a power amplifier that puts out most of its power at the above level.

Apt Holman Preamplifier Phono Stage Measurements
I adjusted the volume control to give a nominal 40 dB level (higher than preamp tests):
View attachment 167053

While I like to see no visible distortion spikes in this test, its level at -100 dB is still very good. SINAD is set by the slight amount of mains noise which I could not get rid of with various grounding methods (typical).

RIAA equalization is very good but there seems to be a high frequency resonance that causes error above 10 kHz:


View attachment 167054

I did not look to see if there is an adjustment/compensation for this in the service manual.

Be sure to use the balance control to restore equal level in both channels.

Level of headroom is good:


View attachment 167055

And doesn't change a lot due to frequency:
View attachment 167056

Conclusions
The owner who sent me this has a knack for finding these past jewels with excellent engineering. Their performance post refurbishing is extreme good even by today's standard which sadly has sled backward. Hopefully no one sheds a tear next time I complain about an audio product producing SINAD of 70 dB and such which this level of performance was achieved years ago.

I am happy to recommend the Apt Holman preamplifier. I see one on ebay for $550 although it will likely need thorough service like the sample I tested.


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As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/

Please note the phono response of this unit is not as shipped. It has been tampered with by removing the final cap of the RIAA equalization that makes up for the +1 term in Zf=Zi+1 equation of a non-inverting feedback amp. Somebody liked it "brighter," but it's wrong. Spec was ±0.2 dB 30 Hz to 15 kHz as I recall, and I made it that because I once heard a +0.5 dB error at 10 kHz in a blind a/b. Stan Lipshitz, former president of AES did a survey of RIAA equalization in preamps published in the AES Journal and among production ones found only three correct: the Quad 33, the Advent 300, and the Apt/Holman. All other high-end ones he measured were wrong.

Also as noted the imbalance is due to a mis-adjustment probably post factory of the cartridge balance control, which is reached through the side. The units were supplied with a test disc for balance. You played it, turned the mode knob to L-R, and adjusted the side control for a null, getting super good balance. This because we also heard small imbalances, also the reason the volume control has a tracking spec.

Cheers and kudos to people who are still interested and have read this.

 

[KEFCarver]

Please note the phono response of this unit is not as shipped. It has been tampered with by removing the final cap of the RIAA equalization that makes up for the +1 term in Zf=Zi+1 equation of a non-inverting feedback amp. Somebody liked it "brighter," but it's wrong. Spec was ±0.2 dB 30 Hz to 15 kHz as I recall, and I made it that because I once heard a +0.5 dB error at 10 kHz in a blind a/b. Stan Lipshitz, former president of AES did a survey of RIAA equalization in preamps published in the AES Journal and among production ones found only three correct: the Quad 33, the Advent 300, and the Apt/Holman. All other high-end ones he measured were wrong.

Also as noted the imbalance is due to a mis-adjustment probably post factory of the cartridge balance control, which is reached through the side. The units were supplied with a test disc for balance. You played it, turned the mode knob to L-R, and adjusted the side control for a null, getting super good balance. This because we also heard small imbalances, also the reason the volume control has a tracking spec.

Cheers and kudos to people who are still interested and have read this.

It is nice to see the designer, and one particularly one of such renown, explain their great "vintage" gear!

 

[NormB]

Just on a lark I went over to ePay and looked for one of these preamps.

Word, apparently, got out.

"I know what I got sonny, and it's worth every penny of $1200."

From what I'm reading, in today's market, some of them, yes.

 

[mglobe]

This is my first post on ASR, as I don't really know enough yet to contribute anything technical. I bought my Apt Holman preamp from my then brother-in-law sometime in the early 80's. It was a king's ransom for me at the time. I always knew it was special piece of gear. It got retired to a closet when I abandoned vinyl and went to home theater, and just recently revived when I decided to replace my dead Philips GA312 and set up a stereo. My Hafler 220 is not well and soon to be replaced with something new. I'm going to end up with hybrid system both phono and streaming, and with DSP running in the processor in/out loop on the Apt. So amazing to see T. Holman here! Thank you sir for this amazing, all original, still working preamp!

 

[EJ3]

This is my first post on ASR, as I don't really know enough yet to contribute anything technical. I bought my Apt Holman preamp from my then brother-in-law sometime in the early 80's. It was a king's ransom for me at the time. I always knew it was special piece of gear. It got retired to a closet when I abandoned vinyl and went to home theater, and just recently revived when I decided to replace my dead Philips GA312 and set up a stereo. My Hafler 220 is not well and soon to be replaced with something new. I'm going to end up with hybrid system both phono and streaming, and with DSP running in the processor in/out loop on the Apt. So amazing to see T. Holman here! Thank you sir for this amazing, all original, still working preamp!

Congratulations. Repairs, updates & mod's are easy also.
MC phono circuits are still available through Audio Proz:
(Quoting them [I am just a satisfied customer]):
"Audio Proz has been in the Hi-Fi and Pro Audio business for over 40 years. The owner, Vince Naeve has worked for companies such as Apt, H.H. Scott, and KLH. We are a different kind of shop. We assist our customers by helping them choose the correct equipment for their application, with special attention to the serviceability, longevity and manufacturer support. We try to be competitive on prices for new products and all of our used items are fully serviced, calibrated and Warranteed. We do not stock cheap throw away electronics that are actually more expensive to own and needlessly pollute the environment".

 

[mglobe]

Just got mine back from restoration by Quirk Audio. Turns out it has the MC circuitry as I suspected. Down the road I may have to play with that but for now the MC sounds (subjectively) glorious. Now where is that Diane Krall album. . Actually I really like her stuff.