Thiel Owners

The only cable I see on the BJ or Iconoclast site is the braided one. That is an extremely difficult geometry to get right. I suspect Galen has gotten it right, and it's worth a try if it's within your budget. 

Check these out guys, a beautiful pair of McCormack Monos.

Each polarity leg of an Iconoclast speaker cable is composed of twenty-four 24 AWG conductors. These conductors are twinned into Teflon®-insulated "bonded pairs," akin to those you may be accustomed to seeing in Belden's data cable products. These twelve bonded pairs are then braided in a basket-weave configuration and flattened to a rectangular profile. The two polarity legs are then laid back to back, and a nylon braid (red/black for ETP, blue/black or OFE or SPTPC) and FEP outer sheath complete the cable.

If you look up Iconoclast you can read the 61 pages of design theory , fascinating and educational . 

The updated quad star design for RCA  and Balanced  interconnects sounds ( no pun intended ) very intriguing . 

Rob - thanks so much for posting Iconoclast. Lovely Sunday read. I highly recommend anyone interested in what’s going on in cable read these papers. No worries for those less mathematically inclined; all the concept engineering is clear without the equations which can serve as illustrations to non-engineers. I’ll be ordering some to compare and contrast.

@everybody wanting to upgrade their 2.4 to 2.4SE..

(And I don't want to put Rob Gillum out if a job here.. ;-) )

I've contacted Clarity Cap and they are only willing to make the 14 and 28 uF caps of their newest purity range (PUR) if I buy a minimum of 25 pieces..

26 pieces would allow for 13 2.4's to be upgraded.. so I need twelve of you guys out there willing to upgrade with the Clarity Cap.. 

PM me if you want this Upgrade.. 

Pieter

All the little details added together may make for a difference.

http://www.claritycap.co.uk/products/pur.php.TomD

Re: Clarity PUR, this is getting above CS2.4SE, all the more so if you also upgrade the resistors and other caps (and if you have an FST board and also replace the coils).

I recall @tomthiel wrote about PUR some weeks ago. I had the impression this line is the next step in the progression SA>ESA>CSA>PUR. But the brochure makes me wonder if PUR is also a step above CMR, which had been the top-shelf Clarity. Curious to see the pricing. 
 

Might be tough to find 12 others willing to pony up for custom cap purchase. I hope I’m wrong. But not a dealbreaker to parallel, for example, 18+10 uF (or, I see 20+8 is also possible). That said, I would not parallel 27+1 or 13+1 after reading an anecdotal report this range of bypassing *might* yield deleterious results. I know the 1 uF bypasses were specified in the original CS2.4 but maybe not a coincidence that Jim Thiel went to full capacitance in single caps for the SE?

Beetlemania - good to see you. I can clarify. All these subsequent caps are way beyond the SE and I agree that dropping ’SE’ might be appropriate for these further upgrades. Jim’s Signature Edition was his late-life offering and the SA cap was the only electronic upgrade. It was CC’s best of its day and won the auditions against other caps including Mundorf and other expensive offerings. Other SE upgrades were the cosmetic bits.

I compared CC SAs to ESA and CSA and reported that the ESA was an incremental improvement and CSA a substantive one. Clarity’s patented PUR breakthrough is replacing the ubiquitous tin/zinc end caps with a tin/copper solution-which is a game changer. Later they added a Van den Hull silver leads option for short money. The CMR is a series cap which uses the same copper end caps. CC discovered that the geometry of the end cap could be improved. In round numbers it went from industry standard (1mm?) to 10mm thick for both the CSA (PUR) and CMR (PUR+). The upcharge is about 20% and said to be a high value improvement. I haven’t tested them due to my present workspace pause, but I am excited.

Regarding your single vs bypass comment - there are trade-offs and as you say, Jim landed on single with a better main cap. The smaller bypass value has shorter discharge time and other reactive improvements, producing a cleaner onset transient than the less worthy larger primary cap. But it also introduces electronic discontinuity in the cap bundle. When the primary cap is good enough, the discontinuities outweigh the timing improvement. In my direct comparisons, one CSA (even the SA) definitely wins, a slight ’capacitor tizz’ goes away.

Jim developed that 1uF cap for the CS5 where it is not a bypass but the capacitive element in the two bucket brigade electronic delay lines that fine-tune the timing of the two midrange drivers. In its day, that was a world-class cap. It became a sonic improvement for following products around our Solens main caps. It got perhaps its best use in the tweeter of the CS3.6 where four of them are bundled as the 4uF series feed block. Today, it lacks the improvements of the new short geometry, silver wire and of course copper end caps. Also, I suspect the post-ELPAC caps may no longer be tin / styrene.

Correction: Second paragraph, second line PUR should read CSA. CC's breakthrough of copper-alloy end caps came with the CSA series.

Thank you for replying and the info👍🏼

It seems I'll have to go either for the caps Rob will be getting shortly with the correct values of 14/28, or I'll have to combine two or more caps.

Seeing as there are more combinations to get to the magical 14 and 28, what would be a good combination, and could that be explained :for instance, would it make a difference if I combine 8+4+2 uF ( each obviously half the others value; would that create an unwanted effect?), or if I combine 8+5+1?

Would it be better to combine 7+7, or would that be what you not want, because of?

Anybody a nice explanation for how to tackle this best?

Pieter

I've already got one potential upgrader👍🏼

One question here in the forum on the matter..

The person in in contact with at clarity caps said that the 28 uF cap would have to be in 250 VDC, as 27 uF would be their largest in 400 VDC, whereas the 14 uF could be made in 630 VDC (I don't know if the caps Rob has are also 630 for the 14 and 250 for the 28 uF cap?).

Would it be a problem, sonically, to put a 250 VDC cap in the system?

Pieter

Pieter - Higher voltage acts more like film-foil and sounds better. But the upper frequencies have far less power than bass, so difference is negligible. Also the 28uF is in the final station where voltage has been previously shunted to ground. Al in - take what you can get.

@pieper1973
The 250 V is not a “problem”. The OEM caps are only 100 V. But as @tomthiel explained, the higher voltage caps have thicker film which is desirable. So, a 250 V PUR would almost certainly sound way better than the OEM 100 V Solens or CYCs. But even better performance is possible with 400 V and 630 V versions. I heard an improvement with 250 V over 160 V CSAs on the woofer boards, and those are shunts, not direct feeds. It wasn’t a huge difference, and I told Tom I could understand a manufacturer going with the 160 V to meet a price point, but I was willing to pay for the improvement.

In my communications with Rob Gillum, he seemed lukewarm around my upgrade project. I suspect his stock is limited to SA at 630 V (I might be wrong!). One clue is that Thiel only built ~200 out of a planned 300 pairs of CS2.4 SE. Those SAs will certainly improve the sonics of the original CS2.4, even more so if you have boards sourced from FST with the CYC polyester caps. But a DIYer can do even better in 2022.

@tomthiel ,@beetlemania

Thank you.. 

tomthiel,

Excuse me if this has been asked as there are too many post in this discussion to read everyone. 

Regarding the CS2.7 are there any cap upgrades? If so what values?

Duramax - the 2.7 has been talked about informally. As the last of the True Thiel designs it is very mature and, unlike other products including the 1.6 and 3.7, XO manufacturer didn't go to China. Thiel made those in-house with traditional Thiel parts best-of-form parts. There are a couple of upgrade opportunities.

1: The midrange has a single 400uF electrolytic feed cap, which Jim would never have done. That cap can be replaced with by 4 @ 100uF high grade electrolytics. Or, I have designed a 100uF CSA 160 volt which will clarify the midrange but take more room than this layout will handle.

2: The tweeter feed has a 15uF + 1uF PP which can be replaced by a CSA or Purity 16uF to good advantage. That by itself would be the largest upgrade and lowest hanging fruit. There are also shunts to common in the tweeter circuit that would benefit in a small way. The 68uF electrolytic up to a CSA and the 1.5uF PP to a PUR.

However, the 2.7 is extremely refined for what it is, so it's way down the list for upgrading. I could get these components with my next CC R&D order, as well as the 2.4 caps that Pieter is asking about.

Tom , beetle and pieper

Wouldn't upgrading the 2.4 value caps to Clarity CMR's be rewarding enough  ?

duramax

I will be installing a Clarity CMR 1.5uf  , a MR 8.2uf on and a Mundorf 68uf electrolytic on the woofer bd. I also got one of those for the tweeter bd.  , If parts connextion has 8 Mundorfs in stock I will be replacing the 400uf topcon with 4 of the 100uf's on the mid bd. , Space is tight but I think I'll be using CMR 1uf on both the tweeter and mid boards as soon as they have another 20% off sale . I haven't found a small enough size electrolytic to replace the ERSE pulseX 15uf's .

Wouldn't upgrading the 2.4 value caps to Clarity CMR's be rewarding enough  ?
 

If I understand @tomthiel correctly, the PUR is an upgrade of the CSA and the CMR is also upgraded. So, yeah, CMR would be very rewarding if your wallet is that thick. In early discussions with Tom, I advocated using CMR at least as bypasses. Every report I’ve read indicated better sonics from CMR compared to CSA. Getting full capacitance, however, in CMR for a Thiel XO would be wallet crushing. Tom gently steered me to CSA which is more in line with the Thiel ethos regarding performance/value. Tom had CMR that I could have auditioned as the 1% bypasses on the coax feeds but I was exhausted of comparisons by that time and I was already thrilled with the sonics from CSA bypassed with Multicaps.

So, PUR is an improved CSA at about 20% added cost. CMR is probably still better than PUR? But a 10 uF CSA 630 V is $22.13 at Parts Connexion whereas the same in CMR is $91.78. So, if PUR gets you most of CMR sonics at a fraction of the price . . .

Beetle 

Thanks , I haven't looked at Clarity's web site for a few months , I now see the PUR and I like the diameter size of the 1uf , So far it's not available at parts connexion .

David Garretson is the US distributor .

2nd

David Garretson is the Man for all things ClarityCap.

Happy Listening!

Beetle and Rob - In my conversations with DG, the CMR thing was problematic in that in some ways the PUR (CSA with thick end caps) outperformed the CMR. Dave was instrumental in pushing CC to develop the PUR+, which is a CMR with thick end caps. FInalization and pricing has taken forever. I'll get that pricing and post some examples here for reference.

in some ways the PUR (CSA with thick end caps) outperformed the CMR
 

Seems like Madisound and PartsConnexion will want to sell most of their current stock of CSA and CMR before investing in PUR. Might be a while before we see PUR at these outlets.

Crap, I’m feeling a twinge of audiophile nervosa. LOL. Hard to imagine I can get much more out of these 2.4s but that’s also what I thought before the upgrades to my Ayre electronics.

Relax Beetle - let us work through the permutations with apples to apples comparisons. When the smoke settles and the fog lifts we might see some place for some PUR caps, but you're sitting pretty till that time. Spin some tunes with your wife. 

@those planning an upgrade of the 2.4. I've been in extensive talks with Clarity Caps and after harassing them (😬😬) I've got them willing to do a smaller batch of teen pieces rasch of the 14 uF and the 28 uF caps. The 14 will come in 630 VDC and the 28 will come in 250 vdc. 

The prices of the caps per piece, ex. VAT and shipping will come to:

PUR 14UH630V X 10 @ €165.00

PUR 28UH250V X 10 @ €142.50

This would mean 330 + 285 = 615 €  (677 $ / 516£) for the set.

I'm in, I've got one potential buyer who I'll be PM-IMG in a minute.

I need three more people willing to jump on the wagon..

PM me

Pieter

Teen should be ten and rasch should be each.. ( for better reading and understanding)

Relax Beetle ... you're sitting pretty till that time

Oh, don't I know it! I remain *very* happy and full of gratitude for all your help, @tomthiel. If someone else has better sounding 2.4s I wanna know about it. So, I was kidding but also curious to hear the PURs.

I remember telling myself, when I last buttoned up the binding plate panels after installing the Cardas, that I wasn't going to take the boards out ever again :)

Curious if you have an opinion or knowledge about how to pair "main caps" if the full capacitance is not available in a single cap. Is it best to optimize balance between caps (eg, 7+7=14) or is there some degree of leeway (eg, 10+3.9+0.1)?

Happy Friday! ALL

vair68robert,

Do you have a schenatic for the CS2.7 crossover. I have a few boxes of cpas I think I could find those values. 

Good morning everyone,

… first post here, but I have been reading you very carefully for some time. 

The question is about the possible crossover upgrade of my cs3.5.  
Currently the speakers are open for maintenance and therefore with possible access to the crossovers. The crossovers are still fully standard and  Rob Gillum tells me that the electrolytics (versa-tronics) even after all these years should be ok. 

That said, what do you suggest I do: replace the caps and also the resistors currently installed?  Which products in particular do you suggest and of which capacities for the 3.5?  Keep in mind that I absolutely do not want to alter the tonal balance  conceived by Jim Thiel. What I would like to do is restore the speakers in question to their original splendor or even improve them, but always keeping the original timbre imprint of the 3.5.  

Another doubt concerns the opportunity to mount some NOS D28/2 dynaudio tweeters that I managed to find. 

The technician who works on the speakers advises me not to install them  saying that the current ones are in good working order and to keep the new units as a reserve (in order to preserve the tonal balance of the speakers that could be altered installing new drivers). That leaves me a bit doubtful because it seems strange to me that the frequency response of the original tweeters has not dropped in a speaker of over thirty 'years, if only for a deterioration of the ferrofluid. 

I am eagerly awaiting your indications on what you believe to be the most appropriate approach. 

Thanks in advance
Stefano

Stefano - Here are some thoughts from having owned, listened to, appreciated and messed around with CS3.5s for decades. You are correct that anything you do will have sonic consequences; and also that some of those consequences will take you closer to the speakers’ original performance. Regarding the tweeters, unless you are hearing problems, I recommend you follow the advice to keep the 28/2s as backups. If you swap, see if Rob at Coherent Source Service can renew your ferro-fluid in your originals to save them as backups. Those VersaTronics caps are high performance, long-life caps. I don’t know of a single failure. However, 40 years is considered their estimated service life, and you are getting close. Some of those electrolytics are in signal paths where their failure would wipe out their driver; so I would replace those for safety. Rob or I can coach you; A’gon disallows sending schematics, etc. Note the 3.5 was the last product with the ultra-bypasses - styrene .015uF around PP 1uF. Great caps, keep them. Also keep your hookup wire.

Caps: better caps exist today and caps are an expensive upgrade. Your biggest bang / buck is to swap the 8uF tweeter feed for a ClarityCap CSA or PUR. These caps will not alter the ’house sound’ whereas other brands will.

Resistors: Jim developed those non-inductive ceramic resistors and they’re better than normal sand-casts. At the time we considered better resistors, but budget prevented their inclusion. I highly recommend swapping at least the series resistors, especially in the midrange and tweeter with Mills MRA-12s. Pretty short money, same circuit performance, sweeter sonics.

Binding posts: If your plastic-cap binding posts work, keep them. They are better than later big, brass posts which were Kathy’s capitulation to market perceptions.

Note: XO values were weaked end of 1987, you want the revision. What are your serial numbers?

Grille frames: This suggestion is just that, offered for general understanding. Those frames cause diffraction, but the fabric was considered in final voicing. IF your room is well damped (soft stuff, especially at wall reflection points), the difference in frequency response is often OK when bare. In that case, best performance is to create a grille frame that functionally fills the baffle edge voids, but eliminates the outer frame members. Conceptually, the new frame would keep the base perimeter and chop off the aerial parts. The long side struts would be rounded over to finish the curve of the baffle. Affix in place with Mortite or BluTac. You improve the anti-diffractive base function and eliminate the diffractive aerial elements.

Equalizer: The equalized bass was fundamental to Jim’s vision - it was abandoned due to market forces. It produces more integrated, better performing bass than the later reflex system. The EQ can be substantially improved (I am close to an available product.) Resistors replaced with metal film, Transistors replaced with lower noise, higher performance, maintainable versions. Caps upgraded as appropriate. Power supply redesigned as regulated rather than present unregulated circuit. Original all-discrete, Star Darlington, direct-coupled design remains. All in, big step up.

There are other hot-rod tweaks which we can discussed via PM if you wish. I posted all this detail for all you who might have been wondering.

@tomthiel 

@duramax747   contact Tom PM ,  he's been of great assistance to me .

duramax,  I am now going to wait for the PUR series for the 4 x 1uf caps needed for the tweeter/mid boards , they solve the size dilemma the I was agonizing over ,

as well as being an upgrade to the upgrade I was planning .

Still searching for an upgrade to the 15uf caps = in size to the ERSE pulse X caps 

Dear Tom, first of all I must tell you that I am honored to be able to talk directly with you on my beloved speakers.  Also wanted to thank you for the truly kind and thorough preliminary answer you gave me. 

I will definitely proceed to ask you questions on specific aspects via pm.

Thanks again

Rob - I can recommend the SonicCap from Sonic Craft that still has the old aspect ratio. Anything Sonic Craft carries has been carefully considered and chosen.

I've had an interesting time tube rolling with my Conrad Johnson Premier 12 tube monoblocks.

Same ones I drove the Thiel 3.7 and now my 2.7s.

When I had both the 3.7 and 2.7 in the house I was trying to decide which one to keep.  One of the distinguishing factors is the 3.7s sounded like they were: a bigger speaker.  Even though by specs only slightly extended further than the 2.7, there was a sense with the 3.7s of the proportion of the sound being a big different.  Bass went a bit deeper, the scale was a bit larger on everything.  The 2.7s seemed like putting a bit of a girdle on - like the bass frequencies were lifted slightly upwards, putting more emphasis on the punchiness of the mid-bass.

I finally tried replacing the 6550 power tube on my amps with the larger more powerful KT120 tubes.  What a difference!   Bass feels deeper, the scale of everything - soundstage, image sizes - expanded.  Now the 2.7s truly remind me of the 3.7s in that sense.   Pretty amazing.

prof

out of curiosity what 5751 tube are you using ?

@beetlemania

re: " Curious if you have an opinion or knowledge about how to pair "main caps" if the full capacitance is not available in a single cap. Is it best to optimize balance between caps (eg, 7+7=14) or is there some degree of leeway (eg, 10+3.9+0.1)?"

My opinion is based on Thiel experience and related observations - both approaches are valid, but will produce slightly different sonic signatures. I believe the cascading bypass format compensates for deficiencies in the large cap which produces dielectric cycle anomalies (charge lag, erratic discharge, Effective Series Resistance irregularities relative to power levels, etc.), along with possible smoothing of the signal in general.  A small cap is inherently less reactive, plus a higher quality small cap is more affordable considering budget constraints. As you have previously mentioned, Thiel’s 1uF bypass cap might sometimes introduce less-than-best characteristic balance when bypassing at greater than 10% of the base cap value. We arrived at our format because we developed that great 1uF tin foil / styrene film cap for the CS5, bought 6-figures of them, and put them to work wherever they made an improvement (that we could afford.) Our main (base) cap was a single cap unless its value exceeded 100uF, where the deleterious secondary effects broke through. In those cases, we used single value multiples. You’ll see ganged 100uF caps (often electrolytic) bypassed by a good polypropylene, bypassed by the great (yellow) 1uF tin/styrene. 100uF was the maximum cap value we identified from listening, and same-value was identified as more correct than cascaded values.

Note this scheme runs contrary to common practice. Note the CS2.7 (outsource engineered after Jim’s death) uses a 400uF lytic in the midrange feed (400E/15PP/1S) and other large, cascaded lytics in that shunt circuit (330E/220E/15PP.) That scheme differs from Jim’s. Note that people who prefer the 2.7 sometimes note they like the "smoothness" or "refinement" of that model which may be attributable to this cascaded approach. Note also, that Vandersteen employs such a cascaded-value, multi type approach to cap bundles. I have wondered if that difference might be a significant contributor to the obvious character difference between Thiel and VdS. The two brands share very similar philosophies and solutions down to wire configuration, but exhibit very different personalities. Jim’s engineering approach was always to identify the solution that addressed the hard-core principles most directly, optimize the particulars and confirm by ear that the most accurate solution had been found. Little to no slack was cut to make harsh recordings sound smoother or mitigate other signal chain problems.

In summary, I would choose the 7+7 option as truer to Jim’s approach. There is, of course, leeway and your other string presents the option of using a CMR (PUR+) as the 0.1uF value without breaking the bank.

If you climb back into your 2.4s and try these options, let us know what you learn. No end to the fun.

In most all applications I never liked the addition of bypass caps especially those on speakers. At one Thiel dealer in 80s we did a comparison of bypass caps on and off the result was they were left off.  For what its worth 3 of the 4 listeners on that day.continued on in the business at least one to this day and still dug in. Tom D

Tom T. & Duramax747

You got me rethinking the shunt circuit on the 2.7 , so I'm sticking with 

the 220uf  6% ERSE and the 330uf 10% changing it from a Topmay ? %

to an ERSE , I was thinking 2 x 220uf 6% and 110uf 6% .

But I will be changing the 400uf ? % Topmay to 2 x 200uf 6% ERSEs .

I also ordered new 6 x 15uf 400V PulseX caps up from 250V .

Thanks again for all your insight .

Rob

vair68robert,

Please let us know what the results turn out to be. 

@tomthiel 

Thank you for the detailed answer. Interesting observation re: Thiel v Vandersteen house sound.

Those 7 uF PURs are the first I’ve seen in that capacitance value. Will be interesting to see if the North American retailers stock those. In the meantime it looks like @pieper1973 has a lead on getting the 14 and 28 in single caps.

If I ever make any further mods it will probably be to try an ultra bypass (eg, Jupiter copper foil), Path graphite resistors in the coax feed path (really tough to get the correct values at all positions), or, if your reports are over the moon, PUR in the coax feeds. Regardless, I’m sitting on some tricked-out, sweet-sounding CS2.4s.

Good day to you all..

I'm having a problem getting my hands on Mills resistors 12 Ohm @12W.

The sender has given me a very long list of other brands..

Anybody here recommend a substitute for the mills at same price range and sonic performance?

Thank you

 Pieter

@pieper1973

Are you in the US? Sonic Craft is your friend. They stock MRA-12s in all the values used in the CS2.4 although you do have to mix and match the old Mills (brown body) with the newer Vishay-Mills (black body). Fast shipping, fair pricing, and excellent service. IIRC, I paid for the mid-grade level matching and they gave me the full set measured at better than the top-grade level matching.

If you are really stuck, the only thing comparable, from my extensive research, is the Ohmite. Wilson uses Caddock but I could never figure out anything that would be suitable in the CS2.4. If you have really deep pockets, you might try Path or Dueland graphite resistors. People say they are the best. They better be at those prices - 5-8 times the Mills! At that’s if you can get the correct resistance in a single resistor. You have to get really creative running in series/parallel to get the proper values. Other than Mills, those are your choices. Otherwise, just keep the OEM resistors.

Adding to Beetle’s excellent summary, here’s a cheapskate trick for the Thiel resistors that you might keep.

Turns out, a big part of those resistors’ ’sonic problem’ is the thermodynamics due to their mounting. They are non-inductive wire-wound with current flowing around their coil circumference, dissipating into the ceramic body. The bottom of that body is glued to the panel, creating a large differential in wire heat distribution. Solution is to mount that same resistor on an edge rather than a flat. Put the edge on Mortite / BluTac pads for even better results. Cheap fix, much of the improvement of Mills, suitable for woofer and midrange. Spend your savings on a Path, etc. for the 12Z tweeter feed.

pieper

try using parallel resistors 

http://www.sengpielaudio.com/calculator-parallel.htm

a 20 and a 30 = 12

Nice tweak, @tomthiel Curious to hear the back story on how you discovered that.

@pieper1973 you have CS2.4, right? Why do you want 12 ohms?

Also, I forgot to mention one of the Mundorf lines is comparable to Mills . . . It’s a re-badged Ohmite.

Beetle - I looked extensively at thermal dynamics as a source of 'aural congestion', drifting crosspoints, etc. That's where the new layouts came from, which have all the resistors separated from caps as well as positioned over ventilation holes in the board for natural convection, and moved either to the exterior of the cabinet or to separate XO enclosures. The hookup wire(s) also mount to pin-type heat exchangers close to each driver to drain voicecoil heat directly through the lead wires. Taken together the thermal management significantly improves dynamic range and 'sonic orderliness' during high-power use. The small-signal Thiel reputation got bigger.

My investigation began by remembering 'warranty claims' for melted caps and charred XO boards in the old days. In my power tests, some resistors got too hot to touch. Series coils also get hot - I put them on 3 rubber feet for all-round radiating and convection. My tool of choice is a non-contact infra-red thermometer to identify small scale/ local differentials. That led to some heat-sinks being added in-line on the XO board for dissipation before entering caps. I don't remember at what stage all that investigation stood when we hot-rodded your 2.4s. There's always more. 

@beetlemania 

Among others I have the 2.4 ..

The 12 Ohm is needed for my one point monitor with the SCS3-N Thiel coaxes.

Audi, I don't want to combine resistors to get to 12 Ohm. I'm just looking for a good substitute for the Mills, if anybody knows of one..