Zenith Consle Amp Narrow Freq Response

[shacky]

OK I may be getting defensive. Is the following comment true about these old Zenith console pulls :scratch2:

Amps like that Zenith have a real narrow frequency response mostly mid range and not much else.

This came from a very reputable tube guy. Please say it ain't so :tears:

 

[Mike Stehr]

It's been said about SET amplifiers as well.

If it sounds good to you, then that's all that matters.

 

[gadget73]

Maybe yes, maybe no. It also depends on your speakers, and your idea of wide frequency response. Its probably not going to go 20-20k, but if it sounds good, who cares? Console amps were not exactly built on the level of a McIntosh but they're not exactly Soundesign either.

 

[33&athird]

I don't think theres a reason it would naturally have a narrow range, although sometimes it said that tubes can have rolled-off bass. Any device in class A and with apporpriate biasing and values in place should perform alright...I think.

I also agree, if you like it, you cares:yes:

 

[shacky]

This was said in a discussion of my Eico HF-81 in comparison to the Zenith. Speakers are Klipsch Forte's.

Both the Zenith and Eico have been recapped.

 

[Phototone]

A lot of console amps had very small output transformers, which "could" limit their bass response. You can always put a larger set of transformers on the amp, from such vendors as Edcor.

 

[shacky]

Actually this little amp has built in bass boost at low volumes which is why I think I was liking it so much I put it in same conversation as my Eico.

After spending time back with the Eico it's obvious the Eico is in different class. But I was wondering about the frequency response limitations comment and if they are real or it's just a slap on a console pull.

The preamp in this little integrated is only one 12AX7. Half for each channel. I've have realy nice tubes in it and it's a fun amp to listen.

I have another one just like it with switchable bass boost. I was going to recap but wanted to know if I'm dealing with something flawed bassed on that comment.

 

[mibag6]

If you have the Zenith, hook it up to the Fortes and give it a listen. I have a similar Zenith amp and coupled with a pair of Heresys it was quite tolerable, produced all the bass you can get out of those. Also, for a grand total of about $50 the Zenith was bought, recapped and converted for stand alone use, not an awful lot spend to find out. I don't have bandwidth specs handy for the Zenith but I think the bottom end was around 30hz and the top I don't remember. I did swap out the original zenith el84s for some sovteks I had in another amp and it made a substantial improvement across the whole spectrum. Basically, give it a listen and see what you think.

 

[billyunderhi]

Speaker Selection - Room size - music selection-

These can be key.

I have a Zenith with (4) EL84 tubes and (2) 12AU7 and a 5U4GB Rectifier
The Power Trans is very large. The amp is stock (old caps)...

I also have a recapped RCA amp (4) EL84 tubes and (2) 6FQ7 witha 5AS4A Rectifier... Power Trans is a bit smaller.

The output Transformers are bigger on the Zenith and have more leads.

Both amps sound very good to my ears. KLH model 17 speakers or Allied Knight 3 way or a full range Altec 755E ---each amp makes great musics...


However in a big room (the shop 18 by 26) There is definately a "sweet spot" and stepping off to the side alot of the music goes missing. The same can be said of the solid state amps I have -Pioneer SX650 and a Bryston 3BST -
The room does not play well with the smaller speakers.

In my living room 10' by 14' - Both tube amps sound better, warmer with more bass.

The Bryston can overdrive these speakers making the top end sound harsh and tizzy or boxy reverberating and boomy depending on the type of music and the volume level.

To my ears the Zenith has a bit more in the lower end compared to the RCA amp. ( will have to recap soon and then see)

Part of the fun is discovering these differences and finding out what my tastes really are.

As mentioned - you can't beat the price of admission. The most I have invested in any tube amp is a minimum of 10 times less than the Bryston purchase.

I think that many smaller (stock wired) tube amps have a limited Freq range but they can do that range very well. There are CDs and records that I have had for 25 years and have listened to with consumer grade solid state equipment exclusively - the tube equipment presents new subtleties and it is fun to rediscover and re-hear music that I thought I knew backwards and forwards.

Tube amps reawakened my enjoyment of and interest in music.
The best part is I know so little and that means there is so much to look forward to learning.

Don't take the limited frequency slight to heart - open ears are better than closed minds.

 

[Narodow]

Shacky,
Bring it over and we can put it on the bench, hook up a load, oscillocope, Wattmeter and drive it with the audio oscillator. I am curious how it measures up to your HF-81.

Bryan

 

[shacky]

Shacky,
Bring it over and we can put it on the bench, hook up a load, oscillocope, Wattmeter and drive it with the audio oscillator. I am curious how it measures up to your HF-81.

Bryan

Sounds like a plan!

When I went back to the Eico I can tell right away the Eico is head and shoulders above the little Zenith. But it would be fun to see how they compare.

The Zenith has a warmth all it's own. Not as much detail as the Eico. But very pleasent for low level listening. The bass boost has it's charm.

BTW - Zenith does have some hum in one channel ...

 

[shacky]

If you have the Zenith, hook it up to the Fortes and give it a listen. I have a similar Zenith amp and coupled with a pair of Heresys it was quite tolerable, produced all the bass you can get out of those. Also, for a grand total of about $50 the Zenith was bought, recapped and converted for stand alone use, not an awful lot spend to find out. I don't have bandwidth specs handy for the Zenith but I think the bottom end was around 30hz and the top I don't remember. I did swap out the original zenith el84s for some sovteks I had in another amp and it made a substantial improvement across the whole spectrum. Basically, give it a listen and see what you think.

I have and am listening again. I had to go back and see what that comment was all about. While the Zenith doesn't have the detail presentation of the Eico and the Eico is definitely more balance frequency wise - the Zenith sounds very nice. Very nice for low level listening with that built in bass boost. :yes:

 

[mibag6]

I wasn't sure from the first post if you had both amps or were considering getting the Zenith or what? From my experience I can say that relatively minor changes on the Zenith can make quite noticeable improvements in sound with the output tube change being the most dramatic. One mod I made from advice given by Tom Bavis was to split the cathode resistor and give each el84 it's own resistor and bypass cap and eliminated the jumper between the 2. That seemed to improve the separation and eliminates the need for matching the tubes. At any rate a little tube rolling might be entertaining, the old zenith tubes were just mush compared to the Sovteks and I stuck a Tele 12ax7 in just for grins and the improvements were substantial. Sorry to ramble, too much coffee and not enough to do.

 

[shacky]

Never havet o apologize to me. Same on my end. This is more fun than work

I have RCA 6BQ5's in output setion. Tele 12AX7 and can't remember the 12 AU it might be tele too.

I just put the Eico back in. It makes the Zenith sound muddy in comparison. But it's a nice muddy The added bass draws you in regardless.

I must say I'm liking the Eico-Forte's much better on the 4 OHM tap :yes:

 

[dcgillespie]

One thing that might help clear some of this up for you is to realize that there are really two issues at play here. Up to this point, the discussion has primarily centered on frequency response. It is important, and does have a notable impact on low level listening. But there is also the power bandwidth to consider as well. Frequency response wise -- which is typically measured at a 1 watt output level -- your Zenith may show some pretty good numbers -- say 30 to maybe even 20 kHz. That would mean that within in a stated level of variation of say +/- 1 or even .5 db, the output of the unit would be consistent over this frequency range at that power output level. But that can all change dramatically as power output is increased.

When a unit is operating at higher output levels, this is where the qualities of the output transformer really come into play. It takes a lot of iron to couple the full power of the amplifier at low frequencies, and well thought out winding patterns to couple all the high frequency power of the amplifier into the secondary load, and not let it all get lost to internal capacitances. The very best transformers can couple the amplifier's full power (with a typical power efficiency of about 80%), with little power loss at the frequency extremes, and therefore little rise in distortion, either. The smaller transformers such as your Zenith has will no doubt give a pleasing sound, and may in fact have a reasonable frequency response. But it is simply not capable of delivering it's full frequency response -- at significant power -- into a secondary load. Therefore, it's power bandwidth is limited.

On the other hand, the output transformers in your Eico have a frequency response to at least 60 kHZ, which will allow it to deliver the amplifier's full power over a range of at least 30 Hz to 15 kHz, which is something the Zenith is simply not capable of. That hardly means to trash the Zenith! It has a part to play in your equipment rotation. However, it also helps to know what it's capabilities are in comparison to the Eico's, so that both can be appreciated for the attributes they offer.

Dave

 

[shacky]

One thing that might help clear some of this up for you is to realize that there are really two issues at play here. Up to this point, the discussion has primarily centered on frequency response. It is important, and does have a notable impact on low level listening. But there is also the power bandwidth to consider as well. Frequency response wise -- which is typically measured at a 1 watt output level -- your Zenith may show some pretty good numbers -- say 30 to maybe even 20 kHz. That would mean that within in a stated level of variation of say +/- 1 or even .5 db, the output of the unit would be consistent over this frequency range at that power output level. But that can all change dramatically as power output is increased.

When a unit is operating at higher output levels, this is where the qualities of the output transformer really come into play. It takes a lot of iron to couple the full power of the amplifier at low frequencies, and well thought out winding patterns to couple all the high frequency power of the amplifier into the secondary load, and not let it all get lost to internal capacitances. The very best transformers can couple the amplifier's full power (with a typical power efficiency of about 80%), with little power loss at the frequency extremes, and therefore little rise in distortion, either. The smaller transformers such as your Zenith has will no doubt give a pleasing sound, and may in fact have a reasonable frequency response. But it is simply not capable of delivering it's full frequency response -- at significant power -- into a secondary load. Therefore, it's power bandwidth is limited.

On the other hand, the output transformers in your Eico have a frequency response to at least 60 kHZ, which will allow it to deliver the amplifier's full power over a range of at least 30 Hz to 15 kHz, which is something the Zenith is simply not capable of. That hardly means to trash the Zenith! It has a part to play in your equipment rotation. However, it also helps to know what it's capabilities are in comparison to the Eico's, so that both can be appreciated for the attributes they offer.

Dave

Dave,

Outstanding explanation. I thank you for that.

I was looking forward to experiencing Single Ended design (pentode with the Zenith. I realize the preamp section is very limited on the Zenith further adding to sonic differences,