hey guys... here's a list of small signal devices that we have been looking at and evaluating...not all of these will be brought to market... bear in mind that we're a small specialist producer not a factory with a ton of idle hands :=))
this list may also serve as a subset of designs which may be available to OEM's in appropiate quantities.
Your feedback (diy folks) on which ones might interest you would be helpful in guaging interest levels...
here goes;
1) MQS-1microphone input/ moving coil step up
pri impedances 600/250/150/62.5 ohms
secondary impedance 77Kohms
turns ratio 1:11.3 (600ohm to 77Kohms)
mol 10 milliwatts
max pri ac vrms (600ohm) 2.45 max
max sec ac volts rms (77kohm) 27.682) EXP-393
bridging\repeat coil
many Japanese use in btwn cd player
and preamp or in btwn cd player and input of power amp which has integrated volume control600 ohm primary to 600 ohm CT secondary
100 milliwatt MOL
max primary volts rms 7.75
very slick design... multiple ES shields
3) MQA-6this might be the basis for a mc step up trans...
pri impedances of 2.5, 5, 10, 15, 20, 30, 40 and 60 ohms
secondary impedance of 60,000 ohms CT
MOL of +10dbm
(note: sec winding could be redesigned for less step up... say drop sec impedance to 47K)
4) MQA-13interstage\phase splitter
mol of 60 milliwatt (+18dbm)
max pri 30 vrms
max sec 60 vrms (30 vrms + 30 vrms)
primary impedance of 15K single ended
secondary impedance of 60K CTtwin coil construction, single c-core.
balanced capacitance to ground on CT seconday.
5) MQA-15push pull interstage
primary impedance of 20K CT
secondary impedance of 45K CT
MOL of 320 milliwatt (+25dbm)
pri ac 80 volts rms (40vmrs + 40 vrms)
sec ac 120 volts rms (60vrms + 60vrms)balanced capacitances to ground on both sides of transformer
twin coil construction, single c-core or EI lamination
6) MQA-16small signal (preamp) output trans
15K single ended primary
secondary impedances of 500 CT, 330, 250, 200 CT, 125 and 50
MOL of 63 milliwatts (+18dbm)No dc. Parafeed only.
Twin coil construction on high perm single c-core.
7) MQA-18small signal PP output trans.
20K CT primary
secondary impedances of 50, 125, 200 CT, 250, 330, and 500 CT.
MOL of (+25 dbm)or 320 milliwatts.
max pri 80 volts rmsCenter tapped windings have balanced capacitances to ground.
Twin coil construction on high perm single c-core.
8) MQA-23driver transformer
20,000 ohms ct primary
7800 ohms ct secondary
MOL of 1 watt (+30dbm)
144 vrms on full primary (72vrms + 72vrms)
88 vrms on full secondary (44vrms + 44vrms)
pri max plate current of 8 madc and .5 madc unbal plate currentdescription for this design states "push-pull 6J5, etc to push-pull 2A3's , 6L6's etc"
msl
Follow Ups:
- Re: small signal transformer designs - pistoljoe 17:24:14 10/23/05
(0)
- In Reply to: small signal transformer designs posted by mqracing on October 20, 2005 at 09:22:57:
Mike, been waiting a few days to mull all these over in my head, and think about not only projects on my bench now, but also future stuff I'd like to tackle.
So, I would have to vote none of the above.
OK, I think you couldnt go wrong with a B7 with a 32ohm tap added for the grado headphones, in place of the MQA-16. The B-7s sound great, the price is great, no need to make a whole different product. At first the MQA-18 looked interesting for this, but then again I thought "How much power do I really need there? Do I need to resort to P-P for headphones?" Both would pale to the TL-404, anyways.
As far as phase splitting and step-ups go, I have a pair of nickle and also a pair of M4 Exo-173s, and I can say they kick ass like nothing else I've heard, or tried. They handle everything up to 100VRMS, right? So most any drivers are cool, there. Why not the mini Exo-173 like was discussed earlier? Say for under 10V? Again, a unique and top product that can do a couple of jobs.
And then for anything that resembles so low like MC duty, I would say to concentrate on your 4722 and 15095s. I know I would buy a hotrodded pair from you, and I bet they would sell like crazy. So, as a consumer, I would hold out for either of those to be offered before the MQS-1 or the MQA-6.
I would also add the TL-404 to my wish list.
Sorry, thats probably not the feedback you were looking for.
Joe
- My view :^) - Paul Joppa 12:58:28 10/23/05
(2)
- In Reply to: small signal transformer designs posted by mqracing on October 20, 2005 at 09:22:57:
For what it's worth ...
1) MQS-1 ... 600/250/150/62.5 to 77Kohms
Works for MC step up, for the lower output cartridges. A 47k secondary would be more universal.
2) EXP-393 ... 600 ohm primary to 600 ohm CT
Good for CD player output, if the player has a good opamp that can drive 600 ohms well.
3) MQA-6 ... 2.5, 5, 10, 15, 20, 30, 40 and 60 ohms to 60,000 ohms CT
Turns ratio is too high for most MC cartridges, and almost nobody uses a push-pull input stage with transformer input.
4) MQA-13 ... 15kSE to 60kCT
interstage\phase splitter but won't quite drive a pair of 45s or 2A3s, so limited application. Maybe powers a PP driver?
5) MQA-15 ... 20K CT to 45K CT
Use with the above phase splitter before the driver stage? How about MQA-13 - PP 5687s - MQA-15 - PP 300B - S-271-A? Very simple amp, and Mike can finally buy that Ferrari!
6) MQA-16 ... 15K single ended to 500 CT, 330, 250, 200 CT, 125 and 50
Just right for preamp and headphone output, using the classic triodes (27/76/6J5/6c4/etc). Not enough juice for pro console peaks, unless a magnetic material with greater headroom is used.
7) MQA-18 ... 20K CT to 50, 125, 200 CT, 250, 330, and 500 CT.
As above for PP outputs; does have more signal level capability
8) MQA-23
driver transformer for Class A2-AB2-B2, not a popular configuration in the last 40 years.
OK, that's my two cents. I think the MQA-16 has the most potential applications - but how does it compare with the B7-15k?
- PJ's view.... - mqracing 15:33:50 10/23/05
(1)
- In Reply to: My view :^) posted by Paul Joppa on October 23, 2005 at 12:58:28:
thanks PJ for your input.
I'll make some brief comments...
******************************************************
1) MQS-1 ... 600/250/150/62.5 to 77KohmsWorks for MC step up, for the lower output cartridges. A 47k secondary would be more universal.
++++++++++++++++++++++++++++++++++++++++++++++++++++we can reduce the turns on the secondary to obtain 47K... I looked in the folder and it appears I did the work to do this quite some time ago.
***********************************************************
*******************************************************
2) EXP-393 ... 600 ohm primary to 600 ohm CTGood for CD player output, if the player has a good opamp that can drive 600 ohms well.
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++I was looking on Sowter's site and noticed that he had some 600 ohm to 600 ohm small signal tranneys slated for use in D to A convertors... so I should explore this further... the 393 is quite a superb design... one of the most exciting (in terms of sheer technical elegance) of all the designs listed in this post. So it would be neat to find some real world (current day) apps for these guys.
**********************************************************************
****************************************************************
3) MQA-6 ... 2.5, 5, 10, 15, 20, 30, 40 and 60 ohms to 60,000 ohms CTTurns ratio is too high for most MC cartridges, and almost nobody uses a push-pull input stage with transformer input.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
yeah... it was listed as an input trans to feed PP grids....that's not where I thought the practicality of this design would bee. Instead I thought of it as perhaps a candidate for real low output moving coil cartridges... and we can "trim down" the 60K ohm secondary to something lower like 47K or 30K or whatever would be a useful step up ratio. what makes this guy sort of interesting is the multiple taps btwn 2.5 ohms and 60 ohms... more research is needed here on whether there is a "need" for these ratios in a moving coil step up.
**********************************************************************
**********************************************************************
4) MQA-13 ... 15kSE to 60kCTinterstage\phase splitter but won't quite drive a pair of 45s or 2A3s, so limited application. Maybe powers a PP driver?
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
yeah with 30 vrms across pri as max then each grid can only see 30 vrms max... which limits it's usefulness as an interstage with most power triodes... but might have some apps if you were building with tubes like the EL84 or etc and wanted to use an interstage splitter...your suggestion if I understand it correctly... appears to be a very good one. this guy might actually be a candidate for use as an input transformer phase splitter... just as you mention\illustrate further below.
this guy might actually have some promise... plus we could tweak the design and make a 1:2 CT with a 10K primary as well... and another version with say a 5K primary. Just like we did with the B7-15K unit.
perhaps ironically, this guy runs at very, very low flux density... and is built on a core larger than the B7. If we adapted this for input transformer phase splitting duties... we could also drop the max vrms across primary (I doubt that anyone would blast the input of their amp with a 30vrms input signal)....
this may deserve more careful review and analysis...
*****************************************************************************************************************************************
5) MQA-15 ... 20K CT to 45K CT
Use with the above phase splitter before the driver stage? How about MQA-13 - PP 5687s - MQA-15 - PP 300B - S-271-A? Very simple amp, and Mike can finally buy that Ferrari!
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
good thought material here... thanks paul.I'd like to do a separate entry\post on this... to ask a few questions and gain more insight....
*********************************************************************
***********************************************************************
6) MQA-16 ... 15K single ended to 500 CT, 330, 250, 200 CT, 125 and 50Just right for preamp and headphone output, using the classic triodes (27/76/6J5/6c4/etc). Not enough juice for pro console peaks, unless a magnetic material with greater headroom is used.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Question. does this unit have enough MOL (i.e., volts) on the secondary to drive phones like the grados and sennheisers?other consideration is... is this unit our best choice from the archives for this application? there's some peerless iron that might recommend themselves for earphone amp applications.
*********************************************************************
******************************************************************
7) MQA-18 ... 20K CT to 50, 125, 200 CT, 250, 330, and 500 CT.As above for PP outputs; does have more signal level capability
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
my sense is very small market for these guys... and there's a Peerless that is probably a bit more of a hot rod (also more mullah)...
*****************************************************************************************************************************************
8) MQA-23driver transformer for Class A2-AB2-B2, not a popular configuration in the last 40 years.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
agreed. must have been brain fade... plus I just wanted to put it up here so I could find a reference to it easily if I needed to.
**********************************************************************
and PJ ended by noting;
::::OK, that's my two cents. I think the MQA-16 has the most potential applications - but how does it compare with the B7-15k?::::by recollection they both have the same MOL and the same basic impedances. the MQA-16 has a slightly better coil geometry in the sense that the secondaries from each end to ct will have greater AC symmetry than the B7. But, there are other design features in the B7 that I like better. the MQA-16 has more core area than the B7.
Beauty of the MQA-16 is that it could be hotrodded fairly easily... what weak points it has in the original design could be abated with a little bit of peerless magic sprinkled over top of it...
msl
- A couple more bits of data - Paul Joppa 22:59:37 10/23/05
(0)
- In Reply to: PJ's view.... posted by mqracing on October 23, 2005 at 15:33:50:
3) MQA-6 ... 2.5, 5, 10, 15, 20, 30, 40 and 60 ohms to 60,000 ohms CT
Out of some 85 MC cartridges in a list I found, only 6 have less than 200uV nominal (5 of them are Ortofons), with a minimum of 100uV. A 20:1 stepup will work well even down to 100uV (makes 2mV output), which is 125 ohms to 50k. If you really want to push these carts into the 5-10mV level, a turns ratio of 1:50 would be the highest ratio ever needed, which would be 20 ohms to 50k.
I suspect this transformer was designed for ribbon mics which have extremely low impedances and output levels. I still don't get the P-P input stage; it raises the noise 3dB - what a waste for low signal levels.
6) MQA-16 ... 15K single ended to 500 CT, 330, 250, 200 CT, 125 and 50
...
Question. does this unit have enough MOL (i.e., volts) on the secondary to drive phones like the grados and sennheisers?IHF spec is 5 volts with 120 ohms source impedance. That means 5v on the 600 ohm tap (+16dBm), 2.5v on the 125 ohm tap (+17dBm), 1v at 30 ohms (+15dBm). Worst case is 125 ohms, +17dBm, and the MOL is +18 for this unit (and the B-7). That's why I think it's "perfect" for headphones.
- A couple more bits of data - Paul Joppa 22:59:37 10/23/05
(0)
- PJ's view.... - mqracing 15:33:50 10/23/05
(1)
- MQA-18 - VoltSecond 20:54:22 10/21/05
(0)
- In Reply to: small signal transformer designs posted by mqracing on October 20, 2005 at 09:22:57:
If the DCR is resonably low, this could make a good headphone transformer.
7) MQA-18
small signal PP output trans.
20K CT primary
secondary impedances of 50, 125, 200 CT, 250, 330, and 500 CT.
MOL of (+25 dbm)or 320 milliwatts.
max pri 80 volts rmsCenter tapped windings have balanced capacitances to ground.
Twin coil construction on high perm single c-core.
Play safe and play longer! Don't be an "OUCH!" casualty.
Unplug it, discharge it and measure it (twice) before you touch it.. . .Oh!. . .Remember: Modifying things voids their warrantee.
- MQA-15, 23... How about SE to PP Parafeed interstage too? - Jim Doyle 17:52:04 10/21/05
(3)
- In Reply to: small signal transformer designs posted by mqracing on October 20, 2005 at 09:22:57:
I'm interested in PP interstages for low-power stuff. I like
planning for 2A3 at the most extreme, KT66 as the average. A more
cheap version for EL84 types and less is cool too.The SE -> PP thing is very cool too. A parafed SE/PP (kinda like
a RIT-5 SR) with balanced windings would be very neat. Mainly to have
a Ni interstage transformer that could both phase split *and* drive
a PP stage.The Lundahl's are, of course, fully capable of driving big shit
like the 845, but why pay for a bigger transformer.-- Jim
- clarification - Jim Doyle 13:16:17 10/22/05
(1)
- In Reply to: MQA-15, 23... How about SE to PP Parafeed interstage too? posted by Jim Doyle on October 21, 2005 at 17:52:04:
What I was thinking and what actually made it to the keyboard
were too different issues. ;)An SE-PP Airgapped (but not nickle) IT would interesting. Yeah, you
can do the EXO-173. However, series fed has one advantage of requiring even fewer parts: no coupling cap, no CCS, no plate load.-- Jim
- Re: clarification - mqracing 16:54:45 10/23/05
(0)
- In Reply to: clarification posted by Jim Doyle on October 22, 2005 at 13:16:17:
Jim wrote:
:::An SE-PP Airgapped (but not nickle) IT would interesting. Yeah, you
can do the EXO-173. However, series fed has one advantage of requiring even fewer parts: no coupling cap, no CCS, no plate load.:::remember that the series feed does have a coupling cap in the signal path to ground... the power supply resevior capacitors... and the entirety of the power supply is in series with the music...
If you look historically at the top of the line offerings by the great tranney companies... the high performance IT's were all parafeed or PP... and for good reasons...
I don't want to argue (and won't) technicalities... but using an
EXO-173 only requires that you use a blocking cap... it does not REQUIRE that you also use a plate choke or a CCS on top of the anode of the tube... you could presumably still use a resistor as the plate load for the tube...though the plate choke and\or the CCS may offer some real world strong advantages... and if mullah is tight... bottlehead's CCS is quite the bargain cost wise.
Just yesterday I ran several designs for a 1:2CT with a nominal 5K pirmary impedance as an airgapped SE interstage... again, the age old question, would it work? yep. Was it elegant? Could it perform as well as an EXO-173? Those are the questions I ask myself. And my sense was that I could not honestly answer in the affirmative.
several of the items listed in this post... perform much stronger when you exlude the polarizing effects of the dc plate currents from the transformer...
so... I just can't get too honestly excited about doing an airgapped IT when I feel we have much, much better mousetraps available. I hope you understand.
thanks,
mike
- Re: clarification - mqracing 16:54:45 10/23/05
(0)
- EXO-173??? n/t - gluca 02:43:21 10/22/05
(0)
- In Reply to: MQA-15, 23... How about SE to PP Parafeed interstage too? posted by Jim Doyle on October 21, 2005 at 17:52:04:
.
- clarification - Jim Doyle 13:16:17 10/22/05
(1)
- MQA-15 - John Swenson 17:40:38 10/20/05
(1)
- In Reply to: small signal transformer designs posted by mqracing on October 20, 2005 at 09:22:57:
I really love differential amplifiers and use them all over the place, the MQA-15 would be perfect for most of these uses. (actually most of my uses do not need that high a voltage rating, but I guess it wouldn't hurt).
John S.
- I vote for the MQA-15 too. (nt) - JLH 04:04:23 10/21/05
(0)
- In Reply to: MQA-15 posted by John Swenson on October 20, 2005 at 17:40:38:
;0)
- I vote for the MQA-15 too. (nt) - JLH 04:04:23 10/21/05
(0)
- MQA-18, MQA-15 and ... - gluca 15:32:41 10/20/05
(5)
- In Reply to: small signal transformer designs posted by mqracing on October 20, 2005 at 09:22:57:
... an input tranny with CT at seconday is really missing.
Whats the max current for MQA-15 and -18?
- Re: MQA-18, MQA-15 and ... - mqracing 16:55:39 10/20/05
(2)
- In Reply to: MQA-18, MQA-15 and ... posted by gluca on October 20, 2005 at 15:32:41:
Hi Gianluca:
check out the EXP-393 and the MQA-6. Each of these have center tapped secondaries.
I don't have the dc plate current ratings handy for the two units you mentioned. I will have to get back to you.
If the "inputs" above aren't what you had in mind... give me some idea of the characteristics (impedances, MOL, and etc) that you would be interested in.
MSL
- A piece of iron ... - gluca 01:52:01 10/21/05
(1)
- In Reply to: Re: MQA-18, MQA-15 and ... posted by mqracing on October 20, 2005 at 16:55:39:
... with +0db voltage gain to be hooked-up at the input of the power-amp.
Something like +20dBu max input level, able to work with sources of 600R and > 10k loads (the grid leak resistor), screened. Nickel.
EXP393 seems really to fit. Would it be happy with that load?
And maybe also a 1:2 step-up with similar specs.
Gianluca
- 2nd vote for 1:2 stepup - Paul Pickard 19:20:12 10/21/05
(0)
- In Reply to: A piece of iron ... posted by gluca on October 21, 2005 at 01:52:01:
but from our previous conversation, you already knew that...
Paul
- 2nd vote for 1:2 stepup - Paul Pickard 19:20:12 10/21/05
(0)
- A piece of iron ... - gluca 01:52:01 10/21/05
(1)
- Re: MQA-18, MQA-15 and ... - Steve Eddy 16:18:39 10/20/05
(1)
- In Reply to: MQA-18, MQA-15 and ... posted by gluca on October 20, 2005 at 15:32:41:
... an input tranny with CT at seconday is really missing.
Perhaps because the secondaries of the really good input trannies tend not to be perfectly symmetrical.
But their asymmetry isn't so great that you can't just split the load between a pair of resistors and take your "center tap" from the node between the two resistors.
se
- Thanks... that's actually my current set-up (n/t) - gluca 01:37:18 10/21/05
(0)
- In Reply to: Re: MQA-18, MQA-15 and ... posted by Steve Eddy on October 20, 2005 at 16:18:39:
.
- Thanks... that's actually my current set-up (n/t) - gluca 01:37:18 10/21/05
(0)
- Re: MQA-18, MQA-15 and ... - mqracing 16:55:39 10/20/05
(2)
- I really like the looks of the MQA-18 - keto 10:08:20 10/20/05
(2)
- In Reply to: small signal transformer designs posted by mqracing on October 20, 2005 at 09:22:57:
...since I'm FINALLY building a parafeed 12SN7GTA + big blue B7 (15K:500) linestage, and as described, the MQA-18 would be a perfect, drop-in PP sub for the B7, with 40 + 40 vrms from the SN7GTA, stepped down appropriately for gain. The parafeed circuit (Bottlehead C4S plate loads) will be tried with the second half of the SN7GTA as a shunt regulator, or alternately, with a pair of gas voltage regulators. Or maybe both, if its possible/adviseable to first shunt regulate (say 450V dropped to 400V) with 1/2 of the SN7GTA, followed by a dropping resistor (from 400V to 265V) to OD3 + OC3, and on to the C4S. Looks like I better drill out a couple more octal socket holes...
.............................................................................................................
MQA-18
20K CT primary
secondary impedances of 50, 125, 200 CT, 250, 330, and 500 CT.
MOL of (+25 dbm)or 320 milliwatts.
max pri 80 volts rms
...............................................................................................................Also planned is the addition of a 3rd PGP8.1 to my PP chassis. This, to head into PP300B territory with a dedicated supply for input/driver, seperate from the output supply of 135mA + big bleeder resistors. First up for input/driver will be a direct coupled 5842 to 45, cap-coupled to EXO-173...
Hey Mike, that's quite a cool list there. What about including separate center taps on the MQA-18 primary, for a loony such as myself who would want to try a cap across them, and thus parafeed the circuit?
Slightly OT link below, to pics from a concert on Tuesday; yours truly the curly haired one with no beard. We generated a couple of acoustic watts, with no phase shift...
--keto
- great pic of Keto..... - mqracing 21:51:48 10/20/05
(1)
- In Reply to: I really like the looks of the MQA-18 posted by keto on October 20, 2005 at 10:08:20:
hey... grrreat photos. A smiling friendly face for sure.
msl
- maybe I'm easily amused... - keto 06:35:47 10/24/05
(0)
- In Reply to: great pic of Keto..... posted by mqracing on October 20, 2005 at 21:51:48:
Early in the a.m. I finished up a parafeed preamp, using the cobalt 15K:500 B7 OPTs -- all, as a kind of experimental platform.
Signal circuit is 100K pot, 12SN7 (170Vp-k, 5mA, -5Vg), 30K plate load and 0.47uF parafeed cap.
PSU, from the IEC with integrated RFI filter, fuse, and switch: Stancor P-6234 (380-0-380vac/90mA, 2.5vac+2.5vac+6.3vac = about 12vac, 5vac/3A), 5U4G, 20uF/600V, BCM-8 (12H, 246ohms), 20uF/600V. This yields a B+ of about 490vdc. An MQ power transformer will be a must, later on.
12SN7 shunt-regulator for each channel. The biasing of the two-pair 12SN7 halves is achieved with a 10K dropping resistor to the "first" triodes (320Vp-k, 10mA, -10Vg, 1K unbypassed cathode R), and from that 330vdc node, the above-mentioned 30K plate load to the "second" triodes.
The sound is great, even hobbled together as it is.
The platform would seem to lend itself to 1) replacing the 10K dropping resistor with a 20mA-rated plate choke, 2) replacing the 30K plate load with a 5mA-rated plate choke, 3) untold experimentation with Bottlehead C4S and the like 4) untold experimentation with those MQ small-signal gadgets.
After performing last Tuesday, I heard a couple concerts in the same series, like the legendary flutist Robert Dick and saxophonist Daniel Kientzy (see pic at link of him playing a couple small horns, with the 7' contrabass bazooka looming over his shoulder). Great concerts, but the fancy amplification equipment was not up to snuff, to my ears. Maybe its just a simple reaction on my part to immediately put together this linestage, and take a few more transistors out of the signal path.
Easily and happily amused... --keto
- http://www.festivalcervantino.gob.mx/prensa/FotosPrensa/23/meta/pages/DSC_0038.htm (Open in New Window)
- maybe I'm easily amused... - keto 06:35:47 10/24/05
(0)
- great pic of Keto..... - mqracing 21:51:48 10/20/05
(1)
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