Does anyone care to ask an amplifier designer a technical question? My door is open.

Yes the Beveridge RM-1 with RM-2 power supply. A legendary component in my opinion with 2 phono inputs. Roger broke the mold with this one. If you have a chance to buy one get it, they show up for around $1000 on eBay. It will most likely need to be refurbished but all in you will have a full function line stage that will rival anything out there regardless of cost.

If I am a good guesser I would have to say that since wolf_garcia plays guitar and he has mentioned the Grateful Dead in a few of his posts the reference would be to the Doug Irwin Wolf guitar (known for the Dire Wolf inlay) made for Jerry Garcia. I’ve seen Garcia play it a number of times and the current owner of the guitar has made it available to be played by others, most notably Steve Kimock who Garcia really respected as a guitarist. You can see it here:

https://liveforlivemusic.com/features/a-brief-history-of-jerry-garcias-five-most-well-known-guitars/

[Side Note: Upon Garcia’s death some of the Irwin guitars made for him were auctioned off to help pay for Doug Irwin’s medical expenses, and it got a little gnarly with the Grateful Dead asking for a piece of the action since they contended none of the equipment ever belonged to Garcia, but was purchased under the Grateful Dead corporate umbrella. In essence the guitars weren’t Garcia’s to give away. So the band got to keep a couple of the guitars in the legal settlement. So much for that community thing.]

As for the Dennis Had Inspire amp, I have a lot of respect for Dennis having owned and enjoyed very early Cary equipment, but knowing someone that measured one of these amps I couldn’t ever bring myself to buy one. If anyone wants to have their amp measured Roger is game to do it (even brought his equipment to Burning Amp one year to measure amps). He keeps notes on all the amps (and some preamps) he has measured. I think Roger has measured most of my equipment and even I was surprised at some of the results.

I'd like to echo Roger's comment regarding the use of the term "hybrid" in reference to the RM-200. I also once thought of this amp in the same manner, but given my access to Roger I have the opportunity to not only listen to a lot of his designs but understand how certain designs came to be. I also have the benefit of being the one who tests repaired amps and new designs in my system.

So I was able to borrow an RM-200 for a while and at first I can't say the amp thrilled me, but over time it did grow on me (I prefer 6550s to KT-88s). I certainly don't think of the circuit as hybrid any longer, in fact to me it's a tube amp, and a cleverly designed one at that. As previously mentioned it may be the only amp with a tube output that puts out more power into lower loads. In addition, as I think about it, those amps referred to as hybrids that I have heard of use tubes on the input and transistors on the output. I have not heard of any others with the opposite design configuration.

When it comes to MR amplifiers the RM-10 MkII is my all time favorite. My old friend Paul Rosenthal (RIP Pubul57) and I ran similar systems at one time. An RM-10 with Lightspeed Attenuator. We always commented to each other how such big sound could come from such a small package. As Roger mentioned one of the things he designs for is reliability. I have owned mine for 12 years now, and other than replacing the power tubes have had zero issues with it.

We get requests from folks who want their old RM-9s refurbished. One of the common side requests we get is to put in an IEC inlet in place of the captive power cord, which from Roger’s perspective is more than adequate for the job, of reasonable length, and quite flexible. We try to talk folks out of this as there is just not enough room between the transformer cover and the edge of the frame to add an IEC inlet. In addition, the RM-9 frame makes this task rather difficult as you have to cut into the wood and there is risk of damage if not done properly. So for those who insist we advise them we will chop the stock cord about 6" from the top plate strain relief, attach a male IEC, and finish it off with shrink wrap and the customer gets to choose the power cord of their choice. Now the signal comes from the Romex in the wall, through the designer power cord, then that last 6" through the original stock power cord into the power supply.

However, some may not be aware that Roger does acknowledge a power cord can make a difference in the system. In this case, a power cord that addresses hum caused by having DC on the line, which can be a hard problem to fix. So he designed a power cord rated at 5 amps that removes DC and will quiet troubled transformers.

@ct0517 - nice set up. I sometimes use my RM-10 with my ESL 57s in biamp set up. The Class AB amp I use for the bottom is a Luxman M-02. I use the Beveridge RM-3 (no remote) to crossover at 100 Hz, 4th order crossovers for both high and low pass. Rather than two woofers I use four in an asymmetrical array. I am curious how you settled on the 60 Hz cutoff and what other levels you may have experimented with.

Regarding the A/B testing, while we began last weekend Roger spent the better part of the week optimizing the set up, no easy task said he. He has now been inviting folks over to listen and I took another stab at it today. This time I brought some go to CDs that I like to use, simple music for the most part, trios and duos, but there are certain things I’ll be listening for. In some cases it’s not even the music, Edgar Meyer’s and Yo Yo Ma’s breathing, Keith Jarrett’s chirping and Gary Peacock’s fretting, The footsteps in Todd Garfinkle’s Jun, the resin on the bow, stuff like that. In other cases it’s the bass, piano, strings, cymbals and high hats.

My session lasted an hour or so and in addition to some unique experiences there were some consistencies across all the music. I originally commented in my notes that the bass produced by the un-modded amp sounded fat but pleasing. However, after more listening, and especially as the bass notes went lower, it was clearly bloated. Not to mention that while the individual bass notes during the solo on Keith Jarret’s version of When I Fall in Love on the modded amp were clearly defined, they were at times smeared on the un-modded amp. In addition, the cymbals and the high hats were slightly muted on the un-modded amp and I could hear a bit of hash as well.

A couple lessons I received in the process. If I didn’t get it before, and I thought I did, I now know for certain the effects a low output impedance amplifier has on a speaker and the resulting sound. In addition, while I can easily hear the effects of an amplifier that clips or has higher amounts of distortion, I think for the first time I could clearly hear the effects of low amounts of IMD as I A/B'ed the amps. Now Roger has invited a few folks from the SFAS to be part of the next group who will participate in the listening test. It will be interesting to hear others impressions and compare notes.

I should have mentioned this, Roger built a very accurate switch box that has a long cable with a button switch on the end. I could sit at the listening position and click the button at various intervals (3 - 5 seconds generally) so going from A>B>A again was very simple. It was also easy to see which amp was in play.

@bdp24 - Eric this has truly been an eye opener. Roger can now do A/Bing on any number of amps. Fritz Heilor lives in the area recently donated a pair of speakers to us to use in a biamping experiment (Roger is impressed with his designs), so besides the Quads we have some box speakers available to us as well. The more the merrier I say. However, this listening stuff is really hard. After an hour or so I really needed a break. While some of the  differences were not subtle, in may cases you really had to focus to hear the differences, and at least to my ears, there were cases where there was no difference at all.

@ct0517 - thanks for the response. With the subs in place are you still running the Quads full range, the using the sub fior 60 Hz and under, or are the Quads completely cutoff at 60 Hz?

@bdp24, well that makes more sense. We are not crossing over the Quad in the test set up. However, in our respective RM-3s both Roger and I use 4th order Linkwitz/Riley crossovers, 24 dB slope cut at 100 Hz for high and low pass. Roger also adds some EQ to the low pass board that I believe he explained here or perhaps in another thread. In any event I have used the Quads with the RM-3 and my bass array in a biamp set up and like that arrangement, which I also do with my modified Acoustats. I don't run the satellites full range.

I probably should have put this in quotes from one of bdp24's posts to eliminate any confusion:

Roger Modjeski (@ramtubes) prefers the 6DJ8 for pre-amp use, but I don’t know that he currently offers a phono amp. Roger or clio09?

That was what I was responding to. In another post bdp24 did mention Roger building a passive for you. As I mentioned in my last post the Pot in the Box passive attenuator is available. The design is very simple using a Noble pot that is laser trimmed, thick film, discrete steps. They are the same extremely high quality Noble pots used on the Audio Research SP-6 and the Beveridge RM-1 (which I own). Typically these are built with two inputs with a selector switch. The front switch also has a mute position (middle position). If you are interested in some specs:

Input Impedance: 50K Ohms
Output Impedance: 0 - 25K Ohms
Frequency Response: DC - 100K Hz

The RM-4 was offered in two formats. The first a pre preamplifier, better known as a moving coil head amp for MC cartridges. Then there is the RM-4+ that adds an RIAA circuit, with optional attenuator and inputs for other sources. We have a couple of these lying around the shop. IIRC correctly one has 2 inputs and the other 6, both have an attenuator and input selector switch. You can send an email to [email protected] if interested.

@bdp24 - technically no, Roger does not offer a new production phono preamp (although we have some unique RM 4+ units lying around that in addition to phono include a volume control and inputs for other sources as well). I have a tape head/phono preamp that he designed in my system right now and which we showed at a SFAS meeting a few months back. It is a 2 box unit with separate power supply. It’s not an easy build and getting it mass produced will be tough, but if someone really wants one built to order, just phono only, and is willing to wait while it is built they can email Roger or I at [email protected] to discuss.

Pot in the box passive preamps can still be made to order. It’s an easy build and Roger has plenty of the really nice Noble pots available that he likes.

Also, FWIW, I’ll mention that Keith Herron, whose company and products (especially his phono stage) are about as non-controversial and highly regarded as they come, suggests that with his particular phono stage no loading whatsoever will often be found to be preferable with LOMCs, regardless of the cartridge type. (The LOMC input of his phono stage is FET-based, and it applies a load resistance to the cartridge that is nearly infinite when load resistors are not connected externally, to RCA jacks that are provided for that purpose). And I have found that to be the case in my own system, with an AT-ART9 cartridge having a recommended load of "100 ohms minimum."

I am glad this has been brought up. I met Keith at an audio show (IIRC the last THE SHOW Las Vegas held at St. Tropez). He had his phono stage there and because I didn't see any loading capability on it assumed it was MM only. He quickly corrected me by pointing out the cartridge he was using. When I asked him why no loading feature he provided an eloquent response that went over my head, but after my own testing, from that day forward I have never loaded a MC cartridge, regardless of the cartridge manufacturer's recommendation. Keith added a loading feature in the next design iteration and continues to offer it today and we can probably guess why.

In a separate post your "intake guy" Clio-something really gave me the business about being a troll and not having anything technical to add.

Actually, I said you bring zero value. The statement wasn't referring to just technical value. Perhaps you got confused with the other part of the paragraph where I said you lack the knowledge or credibility to refute anything Roger says. I was in fact referring to your lack of technical knowledge in that instance, but of course you already copped to that previously.

@fsonicsmith

Let me ask you this Roger; other than one of Ralph’s amps, which modern era top-tier tube amps have you actually sat down and listened to with not just your own planar speakers, but also modern coned speakers across a decent spectrum?

Other than designing amplifiers Roger has a pretty robust repair business and is an authorized repair shop for Allnic. Lots of vintage and modern equipment, solid state and tubed, crosses his path. I know because for the last 3 years I have been the repair intake person. As he has mentioned previously, Roger also measures anything he can get his hands on and has notebooks full of test notes for equipment that spans the ages. Also, Roger does not design planar speakers, he designs electrostatic speakers, there is a difference, perhaps you might read up on that.

Are you living in a cave?

Actually he has quite a nice house with a very nice system.

When we’re bored we go visit local folks to hear their modern systems (this past weekend we heard Avantgarde horns with their associated electronics) and Roger is pretty active with the SFAS, with the responsibility for running the upcoming phonostage shootout in January. My point is that Roger is very up to speed regarding current designs and design "philosophies," but testing and measurements are still critical to producing quality components and the principles behind these measurements go back in time. Ohms Law is still Ohms Law after all. Unless I missed something it hasn’t been updated or modernized.

Same is true for balanced amplifier design. Today we see all sorts of designers referring to their equipment as balanced. In many cases the design is just balanced at the input, not throughout (then there are the pseudo balanced designs). The only person I know that has been doing true balanced tube designs consistently (and in adherence to the balanced standard) has been Ralph Karsten and he’s been at it for over 40 years. However, the concept is not so modern, in fact it wasn’t developed for home audio use, but rather first utilized by the phone company to drive long cable lines (although I am unclear if the phone company developed the standard which I have heard referred to as the 600 ohm standard).

So Fred Sonic Smith (I assume that’s what your handle references) perhaps you should leave us. You bring zero value, you do not possess the knowledge or credibility to refute anything Roger says and although their opinions greatly differ, at least Ralph has the credentials and reputation to partake in those discussions. Let him do so if he wishes, he needs no help from you.

I re-entered because I could not resist. I saw that your irascible behavior has continued and not just towards me, so I felt better about re-entering.

Actually that was your cue to leave and stay away. You re-entered because you enjoy trolling here.

But here’s the kicker: This thread was put up as a promotional device. You can tell because the manufacturer is talking about his products, often more than once in many of his posts. This is against the Audiogon rules, but because I and others are posting here as well, the entire thread doesn’t have to be taken down.

A promotional device in what manner? Do you think Roger is using this thread to try and sell more products? Since you called out Roger on this I will say you are walking a fine line here Ralph, especially given what you once told me in a conversation we had about marketing. The thread was started so that Roger can share his knowledge and experience with the community. He has requested that other designers not respond to the questions asked of him, and from my perspective it’s not that you don’t bring value to the discussion (and I get it’s a public forum), but when you bring up the self promotion stuff, I have to agree with George that it is the pot calling the kettle black.

You consistently promote balanced differential designs, not always mentioning products specifically, although correct me if I am wrong, but you have mentioned the MP-1 was one of the first balanced preamps in high end audio on more than one occasion. I have read many threads where you reference how your preamps solve the issue of cable artifacts coloring the sound, that you make them unity gain with a buffered output, and you have mentioned or alluded to your amplifier designs many a time as well. Granted you do so in a gentlemanly manner and as a means to educate. However, isn’t that what Roger is doing as well?

Here is an example from 12/26/2017:

Our MP-3 preamp is based on the first balanced preamp circuit ever sold to high end audio (our MP-1). It has a direct-coupled output (despite being a tube preamp) and has bandwidth to about 400KHz.

Here is an older example:

How the MP-1 works is it has a direct-coupled output. The output impedance is low enough that it can drive 32-ohm headphones easily. It is designed to drive 600 ohms without effort; obviously its output impedance has to be well below that in order to do so.

Because its outputs are direct-coupled, the output impedance is flat from 1Hz to 200KHz or thereabouts. So it really can drive 200 foot interconnects without difficulty.

It my opinion that getting rid of the output coupling caps is the single best thing you can do with a tube preamp to improve transparency and bandwidth.

The MP-1 was/is the first balanced line preamp for high end audio.

Roger is being very generous with his time (as you have over the years) and trying to answer as many questions as possible. Is he self promoting? His experience for sure. Does he mention his products? Yes. Does he push them? Not in my opinion. From my perspective he references them to supplement responses relevant to his experience or in direct response to questions about that product from other members posting on this thread. I see nothing wrong with that, especially since you have done the same on Audiogon.

@atmasphere
Ralph, while I respect your opinions and body of work, another fine line can easily be drawn between marketing and advertising. You have mentioned to me in the past Audiogon is where you spend most of your marketing efforts. I have a degree in marketing and have been in product marketing most of my professional career. In this age of Internet technology and online consumerism branding is important. You may not agree with this, but your time here sharing your expertise, providing assistance, and yes, mentioning your products, has promoted your brand, which is YOU. Let’s look at these links as an example which are a couple you frequently drop into your posts, including on this thread which is where I pulled them from:

http://www.atma-sphere.com/Resources/Common_Amplifier_Myths.php

http://www.atma-sphere.com/Resources/Paradigms_in_Amplifier_Design.php

If I click on either of the links above I am taken to your site. Simple marketing 101 these days, drive eyeballs to your site. Not only can I read the material, I can then click on a number of links to stay on the site, one of which is products. One might come to the conclusion that it is veiled advertising, but I am not going to get into a pissing match on that one. Suffice it to say in my opinion, and I’m sure I’m not alone, you promote your brand here, albeit respectfully, in a gentlemanly manner, but also in ways that are not overt. Nonetheless though it is promotion and marketing.

Here is another example. You often mention how feedback causes harmonics that the ear/bran can interpret as brightness and provide references you feel back up this point. Again, you are educating people here that in your opinion and listening experience amplifiers employing feedback are colored, but you are also alluding to the fact, which can easily be looked up by anyone inclined to do the research, that your amps don’t provide this coloration because of their minimal or lack of any feedback. You don’t have to mention product names to effectively market or promote them (and yes you cause some diversion because you reference SET amps as well when discussing this).

Now about Roger. Yes he is a friend and I work with him. Yes he has strong opinions about people who based on his knowledge and body of work have not done justice to the science of amplifier design and he calls them out. I can see where his personality might ruffle some feathers or turn off some folks, but let’s also note, which you failed to mention, that he has praised folks like Peter Walker, Julius Futterman, Saul Marantz, Sid Smith, Nelson Pass, and James Bongiorno.

Lastly, as you know I encouraged you at first to continue contributing to this thread as I believe you have valuable things to say. Unfortunately, the self promotion accusation bit has changed that. I have an idea. Why don’t you start a thread of your own and every time you see something here you disagree with or wish to comment on you reference it on your thread and hold a discussion there, and for future reference this will be my last comment on the topic. We have diverted this valuable thread enough.

Right now I am using the Acoustat servos with my modified Acoustat Model 2’s until Roger makes another run of his. Roger has made DD amps in the past for some folks overseas using them with Acoustat panels. The amps are an all tube design where the Acoustat servos had a solid state device for the input.

Here is some basic information for now until Roger chimes in:

http://tubeaudiostore.com/eslelodidram.html

I believe the RM-10 advertised here and referenced above in the thread is sold.

I'm pretty sure the unit for $2450 sold as well. A recent RM-10 buyer contacted us and indicated he purchased a unit that was in Cypress, TX which matches the location of the unit in question. Either way, good for both buyers for getting their hands on a such a nice amp.

@atmasphere - this is the power cord he was referring to that does make a difference under certain circumstances:

http://tubeaudiostore.com/pocoyoucanac.html

Otherwise as Roger noted in his last post just get a cord with good connectors.

Roger addressed this previously in the thread. The short answer is not much if at all. The power cord should be designed such that the ends provide good connections to your outlet receptacle and amp. It should also be of sufficient gauge so as not to cause a safety hazard. I believe the captive power cord on the Music Reference RM-9 was 14 or 16 gauge. Roger used 18 gauge lamp cord for Music Reference preamp and MC head amp captive power cords. I made my own 14 gauge power cords for my components. I bought male and female IEC connectors on Ali Baba and sourced some computer grade three conductor stranded wire. They were not hard to make and parts costs per cable were around $30.

ramtubes - So, you don’t believe power cables make a difference other than connectors and isolation transformers are worthless? Is that correct?

I don’t think he is saying connectors make a difference sound wise as some people might lead you to believe. In other words a Furutech connector won’t sound any better than an Oyaide connector. He is saying just use good ones. For me that means the ability to get a snug fit with the outlet (I use Hubbell hospital grade) and a means to make a good connection with the wire (I use off the shelf "Oyaide" connectors I buy on Ali Baba).

@atmasphere - I can't seem to find the reference you referred to on page 12. What I did find was this which Roger wrote:

I would have had the electrician put in several duplex outlets so no power strip is needed. Power strips vary in cost and quality but the expensive ones with big claims are just marketing. You have nice 10 Ga wire in the wall and then what?

Heres something Ive done. Get a bunch of reasonable power cords, like $20 each of various lengths. Cut off all the male plugs strip and hardwire the cut end directly to the 10 GA wire with a bussbar. Solder good solder lugs to the wires and screw them with a star washer to the bussbar. THe star washers are important. Now you have direct power cords and have eliminated one connection. Make some extras of course. The ones you arent using just coil them up.

I had custom power cords made that are 8 ft long, very flexible, supple, drape nicely and wont pull your smaller devices off the shelf. We have them if you need some.

Bottom line here. Its not the wire that matters. You have hundreds of feet of ordinary magnet wire in every transformer. What you gonna do bout that? :). All this power cord and power strip is just foolishness. Why do we need powercords that are a pain to run?

The custom power cords he is referencing in the quote above I believe to be 14 or 16 gauge, I'll have to check. I don't disbelieve your statement on connectors or power cords heating up, but I have never experienced it on any of my components including yours and Roger's amplifiers. As for the reference to light gauge cords not bringing home the bacon, what gauges are we talking about?

@fleschler - sounds like you are trying to pick a fight with Roger, or perhaps bait him. Seriously, you should re-examine this tactic.

@bdp24 - especially on this day, but my thoughts exactly.

@bdp24 - where can I find that B4 crossover kit you referenced. Haven’t been able to locate it on the Internet.

Yes was aware it was a First Watt product just never saw it advertised as a kit. Nelson does have a crossover kit on the DIY Audio store but it's an analog version of the digital crossover used by Ziegfried Linkwitz, who asked Nelson to design it. I actually have the stuffed boards for this crossover as Nelson made them available at the recent Burning Amp.

I hope that Roger will step in at some point and address some more questions but currently there are a couple projects occupying a lot of his time. So he’s had to take a little break from here.

@4krow - Roger has often talked to me about the difficulty in doing tone controls right. I know there are some C4 preamps of his out there with tone controls that owners have found very useful. He was often asked how to use the controls and his stock response was use the setting that sounds best to you.

In addition, Roger designed and for a while offered the two knob EQ for speakers that lack bass in the 320, 160 or 80 Hz range. You could choose between these frequencies and dial in exactly how much you want to boost, up to + 6 dB if I recall. Roger designed it in part because he listens to a lot of Leon Redbone and noticed the vocals never quite sounded right on most of the speakers he listened to. So the EQ corrected for that. He’s one of the few people I know that consistently uses the bass control on his RM3 crossover. Me, I’m set it and forget it with my RM3, but Roger fiddles with his to get the sound to his liking.

@c1ferrari (it’s been a while Sam, we met at Newport in my room there as you had interest in demoing the Lightspeed attenuator). I will talk to Roger about your situation and see what we can do to help (same for you Baranyi). We do stock the mylar for the panels if you need some.

@ks2 - When Roger refurbishes an RM-5 the preamp gets computer tested pre-end of Soviet era SLN 6922 tubes. That is the preferred tube and the lowest noise 6922/6DJ8 tube he has tested.

FWIW - I have used them in my RM-5 Mk IV, RM-1 (12 tubes total), RM-4, and the as yet unnamed phono stage/tape head preamp. So I can attest to Roger's findings.

@ieales - Thanks for digging that up. From what I read in the link if the B4 kits were to be available in March or so, then they are either quite delayed or perhaps they were made available and sold out. I have the SL kit on a fully populated board but would much prefer a B4 kit.

I can say from Roger's perspective that while he listens to digital sources, I am not sure he would comment on their circuit designs given his lack of interest in manufacturing such a unit. Roger is all about research first and foremost, as a great designer should be. From my conversations with him I don't think he has done much of the research necessary to formulate a response to your questions. Of course I could be wrong and I'm sure others with an opinion might chime in.

I for one, having tried both, always felt that tubes really don't add much value in digital sources. Yes I'm sure the "it's all in the implementation" folks will jump all over that one, perhaps the "jitter" folks as well, but that is just my experience. I've been using the same DAC for 12 years now and have had others in for audition, but the incumbent stays. Is it the PCM 1704 chips? The battery powered output stage? The direct coupled design? The Word Clock output? Not sure, but all I know is nothing else makes me want to replace it.

can you find the thread. I had no luck.

Here you go:

https://forum.audiogon.com/discussions/st-70-best-sounding-version/post?highlight=dynaco%2Bst70&...

Someone asked about the differences between an RM-10 MkI and MkII so perhaps you can educate them. Also, the OP already uses an RM-10 in their main system and is looking at an ST70 for a secondary system.