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In Reply to: RE: Citation A solid state preamp? quality? mods? posted by PeterI on June 29, 2012 at 13:53:30
I suspect that the chassis and front panel are the best parts; the knobs are OK as well. In fairness, the power transformer's probably pretty nice.
In all seriousness, (obviously) I've never heard one, but over the years hk made some very nice sounding vacuum tube and solid state hardware, so even though being a very early ss model is a strike against it, being an hk is one in the "plus" column.
Changing every capacitor probably couldn't hurt, though...
Are the transistors all silicon, or does it have germaniums in it too?
Manual's online courtesy of hk (harman int'l, that is)-- link below.
all the best,
mrh
Follow Ups:
I have had a few Citation As through the years. In fact, I still have one in perfect working order. It is an excellent preamp; if working well. While many caps will be inevitably due to replace / upgrade, this is still a great performer.
If you collect early records, pre stereo, this preamp has great features for you. For stereo, it is even better. If it had more gain, I would restore it and keep it forever; it is that good sounding. Tube preamps win, IMHO, but do not diss this outstanding example of early solid state stereo equipment. Compared to the Citation Eleven and Seventeen and later HK preamp versions, the A wins; every time. Combined with a scarce Citation B amp or the Citation Twelve, these combos are sweet and detailed. I only wish their preamps had more gain/drive. BTW, the Citation Twelve amp is hard to fault...
I'm trying to decide what preamp to use w/ my Heathkit W-5 tube amplifiers. Looking at AA classifieds. The Citation A is older than I thought. I used to have Citation 1. Very nice, but many features I don't need, and overly complicated.
I'm not afraid of a project, would totally rebuild. But I want to have something to show for my work, i.e. great sound and reliability.
cheers
Pete
You had an HF-85 and sold it ? What replaced it ?
I still use the HF-85 line stage as my reference. Before that, my Lafayette KT-600 was my line stage of choice. I also use an Audio Research SP-2 in my main system often, but that is not really a sweet sounder; detailed and accurate, yes. I prefer the warmth of other, more vintage units. Other preamps I have "saved" for a long while were Paragon E, Lux CL-32 and a super rare CL-30. The CL-32 replaced an ARC SP-3A, way back when.
If you can get another HF-85 for a good price, they have great potential. The phono stage can be changed and more phono stages can be added on the mic and tape head positions; easily. The line stage needs very little to still compete with anything you can think of getting. Their prices keep climbing on the bay; so the secret is worldwide, now. The HF-85 would be perfect for your W5s and any amps you want later. The drive capability of the HF-85 line stage is enormous. I used to drive my RCA MI-4256 2A3 amps, which need 5-8 Volts input to start singing, as the number 59 driver tube was the input tube. The KT-600 also drove these well. The longer you wait, the pricier these classic preamps get. The HF-85 is approaching the KT-600 values quickly. KT-600 has a circuit board while the HF-85 is point to point wiring. Certainly, a Mac C-20 is another good candidate. Enjoy !
I bought one years ago (cheap) and I should really do something with it. In its current state, it has some hum (P/S, most likely) and sounds quite mediocre. It's also rife with mediocre 12AX7s, so that's probably part of the issue.
come to think of it, I have a second HF-85 (basket case), too...
all the best,
mrh
If you want to "get rid" of the "basket case" HF85, please contact me off list.
thanks. would fix and keep.
I too had some hum in my last HF85, but in phono, very minor. I did the usual stuff: new electrolytics (JJ, the black cans). also PIO russian coupling caps. Used good parts in phono section. used very good Euro tubes.
cheers,
Pete
I have posted a few times concerning this item. The archives searches should prove worthwhile for mhardy and all. However, since we are "in the neighborhood" a short description is in order. This preamp uses AC filaments and a wimpy amount of power supply capacitance. A few weeks ago, maybe a month, there was a long thread about this preamp which started with the OP pinging my moniker. That thread had the OP's revised scheme of what his HF-85 would have for RIAA EQ, plus someone else posted the ST-84 scheme below that. The ST-84 was a revised HF-85 with a slightly better power supply arrangement, which can easily be added to any HF-85. Check that thread out...My ideology is to always restore the keeper vintage items first; then upgrade. I think the HF-85 has a great sounding line stage. There is an extra coupling cap that can be removed or rearranged in Y fashion; or left stock. But, the original coupling caps that are ceramic or waxy paper are detrimental to the sonics and deserve better upgraded types. If you want that classic sound, polyester/mylar/paper/paper in oil will do the trick. If you want a bit more accurate and seemingly faster sounding, some polystyrene or polypropylene are in order. The power supply needs lots more capacitance for each stage after the rectifier output cap.
The HF-85 phono stage is just alright. It can be made to better standard. Plus, and it is a big plus, the Mic position is an easy place to add another phono EQ circuit. The Mic input has a ceramic input cap wired at the rotary switch. This can be bypassed with wire and a 47K resistor added at the mic input jacks to ground, for the proper RIAA phono loading. Somewhere between those "bypassed" ceramic caps and the switch area common to the tape head and phono EQ feedback circuits, you can add your favorite phono EQ circuit so the Mic position becomes Phono 2. The Tape Head wiring can also be rearranged for yet another phono stage. The 3 3/4 & 7 1/2 toggle switch can be rewired to accommodate various EQ values, which is important to many vinylphiles. I would probably choose two different HF cut networks at that toggle switch.
So, concerning the phono stages, consider that the HF-85 uses a unique feedback arrangement where the first stage is simply high gain and the second stage uses feedback EQ fed back to the second stage grid. Normal/Standard operating procedure for RIAA active EQ usually has the feedback EQ from the second stage plate fed back into the first stage's cathode. This can easily be accommodated, once the wiring is sorted out. The cathode bypass caps at the phono tubes would be removed. Then again, it is going to be your preamp. Thus, study all the circuits you would want to try. The HF-85 can actually be modded for different types of RIAA EQ for the different positions, once you sort out the wiring & parts arrangements. Likewise, the HF-81 integrated, with similar preamp stages, can wholly benefit from this idea.
That sorting out of the wiring is the biggest trick of resto mods. Draw out the stock wiring so you know what you "were" looking at, before you change the wiring. That way, you can always go back to stock. Do not depend on published threads and revised schemes from others, but get inspired from them. Learn the circuitry and learn what differing circuits will sound like. It is very rewarding and enlightening to then actually realize what changes made the sound right or wrong. Now, concerning actual phono EQ network values, again, rely on yourself after studying other published circuits. While the math is important to many, even the parts types actually make sonic impact. So, if your RIAA network EQ poles start out as 850 pf across 91K or 100K(HF cutoff), in series with 2700 pf across 2M(bass boost), depending on your parts type choices, including tubes, you might tweak the circuitry to 750 pf across 95K, in series with 2500 pf across 3 or 4Meg.
For the disbelievers of using your ears, go ahead and use the math. Check out all the vintage active RIAA EQ circuits with all the different tubes, gain setups and topologies. Then, you will surmise that many active/feedback EQ circuits are not that different despite differing overall topologies. I am influenced by the previous work of some genius engineers; plus, I can still trust my ears. I choose to tweak from my experience; when needed. The parts available now were not available when many of these circuits were devised. It is clearly audible that a mica EQ cap will sound different than a polystyrene or ceramic EQ cap of the same value. For absolute assurance, you might desire to build or buy an inverse RIAA EQ circuit and measure frequency response as flat through your EQ circuit passing through the inverse circuit. Then again, how do you know your inverse circuit that you built or bought is a better reference ? Maybe, using well known discs and vinyl systems is just as good, or even a better reference. Best of Luck with your resto efforts...
The benefit of bringing these vintage artifacts back to life, sounding better than they ever did before, is both worthwhile for your brain and your ears...ENJOY !
Edits: 07/01/12
I had so much gear go thru my hands in the years 2006-2010: 2 Eico HF85s, Mac C20, ARC SP-3a, 2 Citation 1s, Conrad Johnson PV-2 (the same one, twice), Quicksilver. The first HF85 I bought locally and then "ruined" with orange drops and average electrolytics. I traded to a guy who was thrilled w/ it. The second I did very thorough work (was more experienced by then), but still sold because I needed the money.I got into integrateds so didn't really need a preamp. Sold my Scott 299D to a friend, my Fishers, and kept the HF81; I didnt need hi power now. I listen to vinyl less and less. But enough about all that, your comments are enlightening, and opinions helpful.
Playing with an '80s Superphon Revelation II SS pre now.
cheers,
Pete
Edits: 07/05/12
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